Ethanol-based pigment dispersion

Abstract

To provide an ethanol-based pigment dispersion small in a dispersed particle size of a pigment, and excellent in storage stability at an ordinary temperature and storage stability at a high temperature, and an ethanol-based ink excellent in jetting property and decap property when using as an inkjet recording method.SOLUTION: An ethanol-based pigment dispersion includes: an aluminum lake pigment (A); and a pigment dispersant (B), where the pigment dispersant (B) is a polymer including a constitutional unit derived from an anionic group-containing monomer (b-1), and a constitutional unit derived from an oxyalkylene group-containing hydrophilic nonionic monomer (b-2). Also provided is an ethanol-based ink for inkjet-recording containing the ethanol-based pigment dispersion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ethanol-based pigment dispersion and an ethanol-based ink for inkjet recording containing the ethanol-based pigment dispersion. [Background technology]

[0002] Inkjet recording is a recording method that directly ejects ink droplets from extremely fine nozzles onto a recording medium, thereby obtaining printed materials with recorded text and images. Unlike conventional recording methods, it does not use printing plates, and is therefore expected to have a wide range of applications as an on-demand printing method that can handle small quantities of diverse products. Recently, there has been research into applying inkjet recording to pharmaceuticals and food products.

[0003] For example, Patent Document 1 describes an edible pigment composition comprising at least a lake pigment, a pigment dispersant, and a dispersion stabilizer, with the aim of providing a pigment composition with excellent dispersion stability (storage stability) of lake pigments, an aqueous ink composition for inkjet use, etc. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-127589 [Overview of the project] [Problems that the invention aims to solve]

[0005] In this context, aluminum lake pigments are pigments formed by the aggregation of polycationized aluminum hydroxide gel, which adsorbs edible dyes, which are originally ethanol-soluble and possess carboxyl and sulfonic acid groups, onto the surface of the aluminum hydroxide gel. Therefore, aluminum lake pigments are generally difficult to disperse in ethanol, and attempts to disperse them in ethanol often result in gelation while incorporating ethanol. Furthermore, even if the pigment can be temporarily dispersed with a pigment dispersant containing anionic functional groups, the aluminum ions eluted from the aluminum lake pigment cause the electric double layer formed by the anionic functional groups of the pigment dispersant to degenerate. This prevents the aggregation of pigment particles due to collisions caused by Brownian motion from being suppressed, leading to an increase in the particle size and subsequent sedimentation of the pigment particles. In the example described in Patent Document 1, sodium polyacrylate is used as a pigment dispersant and water as a dispersion medium. Although sodium polyacrylate is expected to stably adsorb to the surface of aluminum lake pigments because its carboxyl groups are oriented on the polycation aluminum hydroxide gel, it was found that the pigment could not be finely milled to a particle size sufficient for ink ejection in inkjet recording systems, resulting in insufficient storage stability at room temperature (25°C) and high temperatures. Furthermore, when applying ethanol-based inks using aluminum lake pigments to inkjet recording systems, improved ejection performance is also required, as is excellent decapping characteristics that prevent streaking when the ink nozzle surface is left unprotected after printing and printing is started again. The present invention aims to provide an ethanol-based pigment dispersion with a small pigment dispersion particle size and excellent storage stability at room temperature and high temperature, as well as an ethanol-based ink with excellent ejection properties and decapping characteristics when used in an inkjet recording system. [Means for solving the problem]

[0006] The inventors have found that the above problems can be solved by providing an ethanol-based pigment dispersion containing an aluminum lake pigment and a pigment dispersant, wherein the pigment dispersant is a polymer containing constituent units derived from a specific monomer. In other words, the present invention provides the following [1] and [2]. [1] An ethanol-based pigment dispersion containing an aluminum lake pigment (A) and a pigment dispersant (B), An ethanol-based pigment dispersion in which the pigment dispersant (B) is a polymer containing structural units derived from an anionic group-containing monomer (b-1) and structural units derived from a hydrophilic nonionic monomer (b-2) containing an oxyalkylene group. [2] An ethanol-based ink for inkjet recording, comprising the ethanol-based pigment dispersion described in [1] above and an ethanol-soluble organic solvent (C). [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an ethanol-based pigment dispersion with a small particle size of pigment and excellent storage stability at room temperature and high temperature, as well as an ethanol-based ink that has excellent ejection properties and decapping characteristics when used in an inkjet recording system. [Modes for carrying out the invention]

[0008] [Ethanol-based pigment dispersion] The ethanol-based pigment dispersion of the present invention (hereinafter also simply referred to as "pigment dispersion") is an ethanol-based pigment dispersion containing an aluminum lake pigment (A) and a pigment dispersant (B), wherein the pigment dispersant (B) is a polymer containing a structural unit derived from an anionic group-containing monomer (b-1) and a structural unit derived from a hydrophilic nonionic monomer (b-2) containing an oxyalkylene group. In this invention, "ethanol-based" means that in the liquid medium which is a component of the pigment dispersion or ink, ethanol accounts for the largest proportion by mass. In the liquid medium of the ethanol-based pigment dispersion or ethanol-based ink of the present invention, components other than ethanol include water, alcohols other than ethanol, and the like.

[0009] The present invention provides an ethanol-based pigment dispersion with a small pigment dispersion particle size and excellent storage stability at room temperature (hereinafter also referred to as "room temperature storage stability") and high temperature (hereinafter also referred to as "high temperature storage stability"). Furthermore, it provides an ethanol-based ink with excellent ejection properties and decapping characteristics when used in inkjet recording systems, which is a remarkable effect. The reason for this is not entirely clear, but it is thought to be as follows. The pigment dispersion of the present invention contains an aluminum lake pigment, but the pigment dispersant is a polymer comprising structural units derived from anionic group-containing monomers and structural units derived from hydrophilic nonionic monomers having oxyalkylene groups. Here, it is thought that the anionic groups introduced into the polymer by the anionic group-containing monomer are oriented and adsorbed onto the surface of the aluminum hydroxide gel of the aluminum lake pigment, and that the electrical repulsive force suppresses the aggregation and sedimentation of pigment particles, contributing to a reduction in the dispersed particle size. Furthermore, the oxyalkylene groups introduced into the polymer by the hydrophilic nonionic monomer increase the affinity of the aluminum lake pigment near the surface to the ethanol contained as a liquid medium, and the surface of the aluminum lake pigment is covered with a layer of ethanol molecules. As a result, a steric repulsive force is generated by this ethanol molecular layer, which can prevent contact between pigment particles, thus preventing aggregation of pigment particles and suppressing an increase in the particle size of the pigment particles. As a result, the particle size of the pigment dispersion in the pigment dispersion can be reduced, improving storage stability at room temperature and high temperature. Furthermore, when used in inkjet recording systems, it is possible to prevent aggregation of pigment particles in the narrow inkjet nozzles and suppress nozzle clogging, thereby improving ejection performance and decapping characteristics.

[0010] <Aluminum Lake Pigment (A)> The pigment dispersion of the present invention contains an aluminum lake pigment (A). The aluminum lake pigment (A) consists of a dye component (α) that exhibits coloring power and an aluminum hydroxide gel (β) that adsorbs the dye. The dye component (α) preferably has a hydrophilic functional group such as a sulfonic acid group or a carboxyl group introduced into the aromatic ring in the molecule from the viewpoint of detoxifying tar pigments, and thus has high ethanol solubility. From the viewpoint of using a dye component having such a chemical structure as an ethanol-insoluble pigment, the aluminum lake pigment (A) is a polymerized aluminum ion [Al n+2 (OH) 3n 6+ in the form of aluminum hydroxide gel (β) where n is 10 or more, and the dye component (α) is preferably bonded to the carrier.

[0011] The aluminum lake pigment (A) is not particularly limited, but from the viewpoints of reducing the dispersed particle size of the pigment, improving the storage stability at normal temperature and high temperature, and improving the ejection property and decapping property, preferably, as the dye component (α), at least one selected from No. 4 Yellow, No. 5 Yellow, No. 2 Red, No. 3 Red, No. 40 Red, No. 102 Red, No. 104-(1) Red, No. 3 Green, No. 1 Blue, and No. 2 Blue is used, and more preferably, it is one or more selected from aluminum lake of No. 4 Yellow, aluminum lake of No. 5 Yellow, aluminum lake of No. 1 Blue, and aluminum lake of No. 104-(1) Red.

[0012] <Pigment dispersant (B)> The pigment dispersion of the present invention contains a pigment dispersant (B) (hereinafter, also simply referred to as "dispersant (B)"). The dispersant (B) is a polymer containing a structural unit derived from an anionic group-containing monomer (b-1) and a structural unit derived from a hydrophilic nonionic monomer containing an oxyalkylene group (hereinafter, also simply referred to as "hydrophilic nonionic monomer") (b-2). The dispersant (B) is obtained by copolymerizing a raw material monomer containing an anionic group-containing monomer (b-1) and a hydrophilic nonionic monomer (b-2).

[0013] (Anionic group-containing monomer (b-1)) ​The dispersant (B) according to the present invention contains constituent units derived from an anionic group-containing monomer (b-1). The anionic group introduced into the polymer, which is the dispersant (B), by the anionic group-containing monomer (b-1) is oriented to the aluminum hydroxide gel (β) portion of the aluminum lake pigment (A), thereby allowing the dispersant (B) to be adsorbed onto the aluminum lake pigment (A). This is thought to reduce the dispersion particle size of the pigment, improve storage stability at room temperature and high temperature, and further improve discharge and decapping characteristics. There are no particular restrictions on the anionic group, but examples include carboxyl groups, sulfonic acid groups, and phosphate groups. From the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties, a carboxyl group is preferred. Examples of carboxyl group-containing monomers include monocarboxylic acid monomers such as (meth)acrylic acid, 2-ethylacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), α-phenylacrylic acid, β-acryloyloxypropionic acid, sorbic acid, α-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, and β-styrylacrylic acid (1-carboxy-4-phenylbutadiene-1,3); dicarboxylic acid monomers such as fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, mesaconic acid, and glutaconic acid; and tricarboxylic acid monomers such as aconitic acid and tricarboxyethylene. Among these, the anionic group-containing monomer (b-1) is preferably a carboxyl group-containing monomer, more preferably a monocarboxylic acid monomer, even more preferably (meth)acrylic acid, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties. It is even more preferably acrylic acid, and even more preferably acrylic acid, from the viewpoint of improving the dispersibility of the pigment and reducing the viscosity of the pigment dispersion. When the anionic group-containing monomer (b-1) contains acrylic acid, the content of acrylic acid in the carboxy group-containing monomer is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, even more preferably 70% by mass or more, and even more preferably 90% by mass or more, and is preferably 100% by mass or less. In the present specification, "(meth)acrylic acid" means one or more selected from acrylic acid and methacrylic acid. "(meth)acrylic acid" in the following also has the same meaning.

[0014] (Hydrophilic nonionic monomer (b-2) containing an oxyalkylene group) From the viewpoints of reducing the dispersed particle diameter of the pigment, improving the storage stability at normal temperature and high temperature, and improving the ejection property and the decapping property, the dispersant (B) according to the present invention contains a structural unit derived from a hydrophilic nonionic monomer (b-2) containing an oxyalkylene group. In the present invention, the "hydrophilicity" of a monomer means that when the monomer is dissolved until saturated in 100 g of ion-exchanged water at 25°C, the dissolved amount is 10 g or more.

[0015] The hydrophilic nonionic monomer (b-2) is not particularly limited as long as it has an oxyalkylene group and a polymerizable group in the molecule. The oxyalkylene group preferably has 2 to 4 carbon atoms. Specifically, an oxyethylene group, an oxypropylene group, and an oxybutylene group can be mentioned. From the viewpoints of reducing the dispersed particle diameter of the pigment, improving the storage stability at normal temperature and high temperature, and improving the ejection property and the decapping property, it is preferably one or more selected from an oxyethylene group and an oxypropylene group, and more preferably an oxyethylene group. The polymerizable group is a group having a radically polymerizable unsaturated double bond, and examples thereof include one or more selected from a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. Among them, a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group is preferable. Examples of hydrophilic nonionic monomers (b-2) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; polyalkylene glycol (meth)acrylate; alkoxy polyalkylene glycol (meth)acrylate; and polyalkylene glycol monoallyl ether.

[0016] Among these, the hydrophilic nonionic monomer (b-2) preferably has a polyalkylene glycol chain, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties. The average number of moles of alkylene oxide added to the polyalkylene glycol chain is preferably 2 or more, more preferably 4 or more, even more preferably 9 or more, and also preferably 120 or less, more preferably 90 or less, even more preferably 45 or less, and even more preferably 35 or less. If the average number of moles added is within the above range, storage stability at high temperatures (hereinafter also referred to as "high-temperature storage stability") can be maintained for a long period of time. The polyalkylene glycol chain may contain units derived from ethylene oxide and units derived from propylene oxide. The molar ratio [EO / PO] of units derived from ethylene oxide (EO) to units derived from propylene oxide (PO) is preferably 1 or more, more preferably 1.1 or more, even more preferably 1.2 or more, and preferably 9 or less, more preferably 6 or less, even more preferably 3 or less, and even more preferably 2 or less.

[0017] The constituent units derived from the hydrophilic nonionic monomer (b-2) are preferably constituent units derived from polyalkylene glycol (meth)acrylate represented by the following formula (1), from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties. In this invention, "(meth)acrylate" means one or more selected from acrylates and methacrylates. The same applies to "(meth)acrylate" below.

[0018] [ka] (In formula (1), R 11 R represents a hydrogen atom or a methyl group. 12 (where represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, OA represents an oxyalkylene group having 2 to 4 carbon atoms, and n represents the average number of added moles of alkylene oxide, which is between 2 and 120.)

[0019] In formula (1) above, the number of carbon atoms in the oxyalkylene group OA is preferably 2 or more and 3 or less, more preferably 2, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties. That is, the oxyalkylene group OA is preferably one or more selected from an oxyethylene group and an oxypropylene group, more preferably an oxyethylene group, from the same viewpoint as above. In the above equation (1), R 11 From the viewpoint of dispersion stability, it is preferably a methyl group. In the above equation (1), R 12 From the viewpoint of reducing the dispersion particle size of the pigment and improving storage stability at room temperature and high temperature, as well as improving dischargeability and decappingability, the alkyl group is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group. The alkyl group may be linear or branched. In formula (1) above, n, which is the average number of moles added, is preferably 4 or more, more preferably 9 or more, from the viewpoint of reducing the dispersion particle size of the pigment and improving storage stability at room temperature and high temperature, further improving storage stability at high temperature, and improving dischargeability and decappingability, and also preferably 90 or less, more preferably 45 or less, and even more preferably 35 or less, from the same viewpoint as above. However, the n oxyalkylene groups may be identical or different from each other. Furthermore, if the oxyalkylene groups are different from each other, any of the following methods may be used: block addition, random addition, or alternating addition.

[0020] The polyalkylene glycol (meth)acrylate constituting the constituent unit represented by formula (1) is preferably one or more selected from polyethylene glycol mono(meth)acrylate, polyethylene glycol / polypropylene glycol (meth)acrylate, alkoxy polyethylene glycol (meth)acrylate, and alkoxy (polyethylene glycol / polypropylene glycol) (meth)acrylate, and more preferably one or more selected from polyethylene glycol mono(meth)acrylate and alkoxy polyethylene glycol (meth)acrylate. The alkoxy polyethylene glycol (meth)acrylate is preferably one or more selected from methoxy polyethylene glycol mono(meth)acrylate, ethoxy polyethylene glycol mono(meth)acrylate, propoxy polyethylene glycol mono(meth)acrylate, butoxy polyethylene glycol mono(meth)acrylate, octoxy polyethylene glycol mono(meth)acrylate, and stearoxy polyethylene glycol mono(meth)acrylate, more preferably one or more selected from methoxy polyethylene glycol mono(meth)acrylate, ethoxy polyethylene glycol mono(meth)acrylate, and propoxy polyethylene glycol mono(meth)acrylate, and even more preferably methoxy polyethylene glycol mono(meth)acrylate.

[0021] As described above, the hydrophilic nonionic monomer (b-2) is preferably alkoxy polyethylene glycol mono(meth)acrylate, more preferably one or more selected from methoxy polyethylene glycol mono(meth)acrylate, ethoxy polyethylene glycol mono(meth)acrylate, and propoxy polyethylene glycol mono(meth)acrylate, and even more preferably methoxy polyethylene glycol mono(meth)acrylate.

[0022] Specific examples of commercially available hydrophilic nonionic monomers (b-2) include NK ester M-20G, M-40G, M-90G, M-230G, M-450G, and M-900G (all manufactured by Shin Nakamura Chemical Industry Co., Ltd.); Bremmer PME-1000, PME-4000, and 50POEP-800B (all manufactured by NOF Corporation); and Light Ester 041MA (manufactured by Kyoeisha Chemical Co., Ltd.).

[0023] (Hydrophobic monomer having an alkyl group (b-3)) The dispersant (B) according to the present invention is preferably a polymer that further contains structural units derived from an anionic group-containing monomer (b-1) and structural units derived from a hydrophilic nonionic monomer (b-2), as well as structural units derived from a hydrophobic monomer (b-3) having an alkyl group (hereinafter also simply referred to as "hydrophobic monomer"). In this invention, "hydrophobic monomer" means a monomer in which the amount dissolved when dissolved in 100g of ion-exchanged water at 25°C until saturated is less than 10g. Because the dispersant (B) has an alkyl group introduced by the hydrophobic monomer (b-3), when the ethanol contained as a liquid medium volatilizes on the ink nozzle surface, the alkyl groups gather together, and the dispersant (B) forms a polymer film, suppressing excessive volatilization of ethanol and preventing the ink from drying on the ink nozzle surface. Furthermore, when new ink is supplied into the inkjet head during maintenance, the affinity of the alkyl group portion introduced in the dispersant (B) to ethanol dissolves the polymer film of the dispersant (B) formed on the ink nozzle surface, making it easy to restore a good ejection state. As a result, it is thought that the ink ejection performance is improved and the decapping characteristics, which make streaking less likely, can be further improved.

[0024] Hydrophobic monomers (b-3) have an alkyl group and a polymerizable group within their molecule. The number of carbon atoms in the alkyl group contained in the hydrophobic monomer (b-3) is preferably 1 or more, preferably 22 or less, more preferably 18 or less, even more preferably 16 or less, even more preferably 12 or less, even more preferably 10 or less, even more preferably 8 or less, even more preferably 6 or less, and even more preferably 4 or less. If the number of carbon atoms in the alkyl group of the hydrophobic monomer (b-3) is within the above range, drying of the ink on the ink nozzle surface can be suppressed, and when new ink is supplied into the inkjet head during maintenance, the dissolution of the polymer film of the dispersant (B) on the ink nozzle surface is promoted, making it easier to remove the polymer film with fewer maintenance cycles, and improving ejection performance and decapping characteristics. Examples of alkyl groups for hydrophobic monomers (b-3) include linear, branched, or alicyclic alkyl groups. Examples of linear or branched alkyl groups include methyl, ethyl, n-butyl, sec-butyl, isobutyl, tert-butyl, and n-hexyl groups. Examples of alicyclic alkyl groups include cyclohexyl groups. Among these, from the viewpoint of suppressing the drying of the ink on the ink nozzle surface, facilitating the removal of the polymer film with fewer maintenance times, and further improving the ejection property and decapping property, the alkyl group of the hydrophobic monomer (b-3) is preferably a linear or branched alkyl group, more preferably one or more selected from a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group, still more preferably one or more selected from a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group, still more preferably one or more selected from a methyl group, an ethyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group, still more preferably one or more selected from a methyl group, an ethyl group, and an n-butyl group, and still more preferably one or more selected from a methyl group and an ethyl group. The polymerizable group is a group having a radically polymerizable unsaturated double bond, and examples thereof include one or more selected from a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. Among them, preferably, it is a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group, more preferably an acryloyl group or a methacryloyl group, and still more preferably a methacryloyl group.

[0025] From the viewpoint of suppressing the drying of the ink on the ink nozzle surface, facilitating the removal of the polymer film with fewer maintenance times, and further improving the ejection property and decapping property, the structural unit derived from the hydrophobic monomer (b-3) is preferably a structural unit derived from an alkyl (meth)acrylate having an alkyl group derived from an aliphatic alcohol represented by the following formula (2).

[0026]

Chemical formula

[0027] In formula (2) above, R is an alkyl group. 22 The number of carbon atoms is preferably 1 or more, from the viewpoint of suppressing ink drying on the ink nozzle surface, facilitating removal of the polymer film with fewer maintenance cycles, and further improving ejection and decapping characteristics. From the same viewpoint as above, it is preferably 22 or less, more preferably 18 or less, even more preferably 16 or less, even more preferably 12 or less, even more preferably 10 or less, even more preferably 8 or less, even more preferably 6 or less, and even more preferably 4 or less. R is an alkyl group 22 R is an alkyl group derived from a linear, branched, or alicyclic aliphatic alcohol. 22 From the same viewpoint as described above, it is preferably a linear or branched alkyl group, more preferably one or more selected from methyl group, ethyl group, propyl group, n-butyl group, sec-butyl group, isobutyl group, tert-butyl group, and n-hexyl group, even more preferably one or more selected from methyl group, ethyl group, propyl group, n-butyl group, sec-butyl group, isobutyl group, and tert-butyl group, even more preferably one or more selected from methyl group, ethyl group, n-butyl group, sec-butyl group, isobutyl group, and tert-butyl group, even more preferably one or more selected from methyl group and ethyl group.

[0028] The hydrophobic monomer (b-3) is preferably an alkyl (meth)acrylate having an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms, and even more preferably one or more selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and n-hexyl acrylate, and even more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate It contains an alkyl (meth)acrylate having one or more alkyl groups with 1 to 4 carbon atoms selected from t-butyl, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, and tert-butyl acrylate, more preferably an alkyl (meth)acrylate having one or more alkyl groups with 1 to 4 carbon atoms selected from methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methyl acrylate, ethyl acrylate, and n-butyl acrylate, more preferably one or more selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl acrylate, more preferably one or more selected from methyl methacrylate and ethyl methacrylate, and more preferably one or more selected from methyl methacrylate and ethyl methacrylate.

[0029] The content of alkyl (meth)acrylate ester having an alkyl group with 1 to 4 carbon atoms in the hydrophobic monomer (b-3) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and preferably 100% by mass or less, from the viewpoint of suppressing ink drying on the nozzle surface, facilitating removal of the polymer film with fewer maintenance cycles, and improving discharge performance and decapping characteristics. The total content of methyl methacrylate and ethyl methacrylate in the hydrophobic monomer (b-3) is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less, from the viewpoint of suppressing ink drying on the nozzle surface, facilitating removal of the polymer film with fewer maintenance cycles, and further improving discharge performance and decapping characteristics.

[0030] Specific examples of commercially available hydrophobic monomers (b-3) include Light Ester E (ethyl methacrylate), Light Ester NB (n-butyl methacrylate), Light Ester IB (isobutyl methacrylate), and Light Ester TB (tert-butyl methacrylate) (all manufactured by Kyoeisha Chemical Co., Ltd.).

[0031] The dispersant (B) may have constituent units derived from anionic group-containing monomer (b-1), constituent units derived from hydrophilic nonionic monomer (b-2), and constituent units derived from monomers other than hydrophobic monomer (b-3), to the extent that it does not impair the effects of the present invention. Examples of other monomers include hydrophilic nonionic monomers other than hydrophilic nonionic monomer (b-2); and hydrophobic monomers other than hydrophobic monomer (b-3).

[0032] Examples of hydrophilic nonionic monomers other than hydrophilic nonionic monomer (b-2) include (meth)acrylamide; N-vinyl-2-pyrrolidone; and N-alkyl(meth)acrylamide. Examples of hydrophobic monomers other than (b-3) include aromatic group-containing monomers. The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group with 6 to 22 carbon atoms, which may have substituents including heteroatoms, and more preferably one or more selected from styrene monomers and aromatic group-containing (meth)acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of styrene monomers include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. Examples of aromatic group-containing (meth)acrylates include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0033] The content of constituent units derived from the anionic group-containing monomer (b-1) in the total constituent units of the dispersant (B) is preferably 3% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and even more preferably 13% by mass or more, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature, further improving storage stability at high temperatures, and improving dischargeability and decappingability. Furthermore, from the same viewpoint as above, it is preferably 55% by mass or less, more preferably 45% by mass or less, even more preferably 35% by mass or less, even more preferably 25% by mass or less, and even more preferably 20% by mass or less. The content of constituent units derived from hydrophilic nonionic monomer (b-2) in the total constituent units of the dispersant (B) is preferably 40% by mass or more, more preferably 65% ​​by mass or more, even more preferably 75% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature, further improving storage stability at high temperatures, and improving dischargeability and decappingability. Furthermore, from the same viewpoint as above, it is preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. When the dispersant (B) contains constituent units derived from the hydrophobic monomer (b-3), the content of constituent units derived from the hydrophobic monomer (b-3) in the total constituent units of the dispersant (B) is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and still more preferably 1% by mass or more, and from the viewpoint of suppressing ink drying on the ink nozzle surface, facilitating removal of the polymer film with fewer maintenance cycles, and further improving discharge performance and decapping characteristics, and also preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, still still preferably 9% by mass or less, still still preferably 8% by mass or less, still still preferably 7% by mass or less, still still preferably 5% by mass or less, and still still preferably 3% by mass or less.

[0034] When the dispersant (B) contains constituent units derived from hydrophilic nonionic monomers other than hydrophilic nonionic monomer (b-2), the content of constituent units derived from hydrophilic nonionic monomers other than hydrophilic nonionic monomer (b-2) is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of improving the adsorption of the dispersant to the aluminum lake pigment in an ethanol-based medium, reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties.

[0035] When the dispersant (B) contains constituent units derived from hydrophobic monomers other than hydrophobic monomer (b-3), the content of constituent units derived from hydrophobic monomers other than hydrophobic monomer (b-3) is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of improving the adsorption of the dispersant to the aluminum lake pigment in an ethanol-based medium, reducing the dispersion particle size of the pigment, improving storage stability at room temperature and high temperature, and improving discharge and decapping properties.

[0036] As described above, the dispersant (B) may have other constituent units other than those derived from the anionic group-containing monomer (b-1), the hydrophilic nonionic monomer (b-2), and the hydrophobic monomer (b-3), as long as the effects of the present invention are not impaired. However, the total content of constituent units derived from the anionic group-containing monomer (b-1), the hydrophilic nonionic monomer (b-2), and the hydrophobic monomer (b-3) is such that, from the viewpoint of reducing the dispersion particle size of the pigment and improving storage stability at room temperature and high temperature, and furthermore, high temperature storage stability From the viewpoint of improving qualitative properties, as well as improving discharge and decapping properties, the composition is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 97% by mass or more, even more preferably 99% by mass or more, and preferably 100% by mass or less, and more preferably consisting only of structural units derived from anionic group-containing monomer (b-1), structural units derived from hydrophilic nonionic monomer (b-2), and structural units derived from hydrophobic monomer (b-3).

[0037] The dispersant (B) is preferably a polymer containing a structural unit derived from (meth)acrylic acid as an anionic group-containing monomer (b-1), a structural unit derived from alkoxy polyethylene glycol (meth)acrylate as a hydrophilic nonionic monomer (b-2), and a structural unit derived from an alkyl (meth)acrylate ester having an alkyl group having 1 to 10 carbon atoms as a hydrophobic monomer (b-3). More preferably, the dispersant (B) contains a structural unit derived from (meth)acrylic acid as an anionic group-containing monomer (b-1), a structural unit derived from methoxy polyethylene glycol (meth)acrylate as a hydrophilic nonionic monomer (b-2), and a structural unit derived from an alkyl (meth)acrylate ester having an alkyl group having 1 to 6 carbon atoms as a hydrophobic monomer (b-3). Dispersant B may be synthesized by a known polymerization method, or a commercially available product may be used.

[0038] In the present invention, during the process of forming a polymer film of the dispersant (B) on the ink nozzle surface following the evaporation of ethanol, alkyl groups gather together through hydrophobic interactions as ethanol evaporates. These aggregated alkyl groups act as starting points for film formation, thus suppressing ink drying on the ink nozzle surface. Furthermore, during maintenance, due to the affinity of the alkyl group portion introduced into the dispersant (B) for ethanol, the aggregated alkyl groups (nuclei) in the polymer film dissolve due to the ethanol in the newly supplied ink. This makes the polymer film easily ruptured, facilitating the restoration of a good ejection state. Thus, by having alkyl groups introduced by the hydrophobic monomer (b-3) in the dispersant (B), it is possible to form a polymer film that suppresses excessive ethanol evaporation during ink drying and has the property of being easily ruptured due to the affinity of the alkyl group portion for ethanol during maintenance. This is thought to improve ink ejection performance and further enhance decapping characteristics that reduce streaking. The formation of a polymer film exhibiting such effects is thought to depend on the type and number of alkyl groups introduced into the dispersant (B). From this viewpoint, when the dispersant (B) contains constituent units derived from anionic group-containing monomer (b-1), constituent units derived from hydrophilic nonionic monomer (b-2), and constituent units derived from hydrophobic monomer (b-3), the molar concentration of alkyl ester groups in the dispersant (B) is an indicator of the type and number of alkyl groups introduced into the dispersant (B). From the viewpoint of further improving dischargeability and decapping, the molar concentration of alkyl ester groups in the dispersant (B) is preferably 0.5 mol% or more, more preferably 0.7 mol% or more, even more preferably 1 mol% or more, even more preferably 3 mol% or more, even more preferably 4.5 mol% or more, even more preferably 5 mol% or more, even more preferably 5.5 mol% or more, and preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and even more preferably 8 mol% or less. The molar concentration of alkyl ester groups in the dispersant (B) can be calculated from the monomer composition of the dispersant (B) and the molecular weight of each monomer.

[0039] From the viewpoint of controlling molecular weight, a solution polymerization method is preferred for obtaining the dispersant (B). The solvent used in solution polymerization is not particularly limited, but water, aliphatic alcohols having 1 to 3 carbon atoms, ketones having 3 to 8 carbon atoms, esters such as ethyl acetate, and mixed solvents of one or more of these with water are preferred. However, isopropanol is preferred from the viewpoint of having a boiling point above the polymerization temperature and ease of removal after polymerization. Polymerization initiators and chain transfer agents can be used during polymerization. Any polymerization initiator commonly used in solution polymerization can be used. Examples include organic peroxides such as dilauroyl peroxide, pivaloyl tert-butyl peroxide, and tert-butyl peroxyneodecanoate; and azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile). Among these, dilauroyl peroxide is preferred. The amount of polymerization initiator used is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the total amount of raw material monomers of dispersant (B), from the viewpoint of the molecular weight distribution of dispersant (B), and also preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, from the same viewpoint as above. A chain transfer agent may be used as needed. When a chain transfer agent is used, isopropanol and thiol compounds are preferred as such agents. When isopropanol is used as a chain transfer agent, it can also be used as the solvent in solution polymerization. From the viewpoint of controlling molecular weight and being compatible with the solvent, isopropanol is preferred as the chain transfer agent. When a thiol compound is used as a chain transfer agent, the amount of thiol compound used is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of the total amount of raw material monomers of the dispersant (B), and from the viewpoint of the molecular weight distribution of the dispersant (B), and from the same viewpoint as above, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less. When isopropanol is used as both a chain transfer agent and a solvent, the amount of isopropanol used is preferably 30 parts by mass or more, more preferably 100 parts by mass or more, and even more preferably 200 parts by mass or more, per 100 parts by mass of the total amount of raw material monomers of dispersant (B), and, from the viewpoint of the molecular weight distribution of dispersant (B), preferably 1,000 parts by mass or less, more preferably 500 parts by mass or less, and even more preferably 300 parts by mass or less.

[0040] The preferred polymerization conditions vary depending on the type of polymerization initiator, but the polymerization temperature is preferably 50°C to 90°C, and the polymerization time is preferably 1 hour to 20 hours. When an organic peroxide is used as a polymerization initiator, the polymerization temperature is preferably 60°C or higher, more preferably 65°C or higher, from the viewpoint of reactivity, and preferably 85°C or lower, more preferably 83°C or lower, from the viewpoint of the molecular weight distribution of the dispersant (B). The polymerization atmosphere is preferably an inert gas atmosphere such as a nitrogen gas atmosphere or argon. After the polymerization reaction is complete, the generated dispersant (B) can be isolated from the reaction solution by known methods such as reprecipitation and solvent removal. Furthermore, unreacted monomers and other substances can be removed from the dispersant (B) by methods such as reprecipitation, membrane separation, chromatography, and extraction. From the viewpoint of improving the productivity of the pigment dispersion, the dispersant (B) may be used as a solution of the dispersant (B) without removing the solvent used in the polymerization reaction.

[0041] The acid value of the dispersant (B) is preferably 25 mg KOH / g or more, more preferably 30 mg KOH / g or more, even more preferably 50 mg KOH / g or more, and even more preferably 100 mg KOH / g or more, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature, further improving storage stability at high temperatures, and improving discharge and decapping properties. From the same viewpoint as above, it is preferably 400 mg KOH / g or less, more preferably 350 mg KOH / g or less, even more preferably 300 mg KOH / g or less, even more preferably 250 mg KOH / g or less, even more preferably 200 mg KOH / g or less, even more preferably 150 mg KOH / g or less, and even more preferably 130 mg KOH / g or less. The acid value can be measured by the method described in the examples.

[0042] The weight-average molecular weight of the dispersant (B) in terms of polystyrene is preferably 5,000 or more, more preferably 20,000 or more, and even more preferably 40,000 or more, from the viewpoint of improving dispersion stability, room temperature storage stability, further high temperature storage stability, and discharge and decapping properties, and from the viewpoint of reducing the dispersion particle size of the pigment, it is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 250,000 or less, even more preferably 200,000 or less, even more preferably 150,000 or less, and even more preferably 100,000 or less. The weight-average molecular weight can be measured by the method described in the examples.

[0043] The dispersant (B) may be ionized by neutralizing at least some of its anionic groups. This allows for random electrical repulsion to be imparted to the dispersant (B), and the solvation of the anionic groups of the dispersant (B) with ethanol in an ethanol-based medium suppresses the formation of intramolecular hydrogen bonds. As a result, the polymer chains of the dispersant (B) remain sufficiently expanded without contraction in the ethanol-based medium, allowing the anionic groups of the dispersant (B) to more efficiently form ionic bonds with the aluminum of the aluminum lake pigment (A). This is thought to reduce the particle size of the pigment dispersion, improve storage stability at room temperature and high temperatures, and further improve discharge and decapping properties. From this viewpoint, the degree of neutralization of the dispersant (B) is preferably 0 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, even more preferably 8 mol% or more, even more preferably 10 mol% or more, and preferably 90 mol% or less, more preferably 70 mol% or less, even more preferably 50 mol% or less, even more preferably 40 mol% or less, even more preferably 37 mol% or less, even more preferably 27 mol% or less, even more preferably 22 mol% or less, and even more preferably 17 mol% or less.

[0044] Examples of neutralizing agents used for neutralization include ammonia; organic amines such as ethylamine, diethylamine, trimethylamine, triethylamine, and triethanolamine; and alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, alkali metal hydroxides are preferred, and sodium hydroxide is more preferred, from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature, further improving storage stability at high temperatures, and further improving discharge and decapping properties. These neutralizing agents can be used individually or in combination of two or more. The neutralizing agent may be used as an ethanol solution of the neutralizing agent or an aqueous solution of the neutralizing agent, and it is preferable to use an ethanol solution of the neutralizing agent.

[0045] (Manufacturing of ethanol-based pigment dispersions) There are no particular limitations on the method for producing the pigment dispersion of the present invention, but from the viewpoint of reducing the dispersion particle size of the pigment, improving storage stability at room temperature, further improving storage stability at high temperatures, and improving discharge and decapping properties, a method of dispersing a pigment mixture containing aluminum lake pigment (A), dispersant (B), ethanol, and optionally additives in a disperser is preferred. Furthermore, in the dispersion treatment, a neutralizing agent may be added as needed to neutralize and ionize at least a portion of the anionic groups of the dispersant (B). The dispersion treatment of the pigment mixture may be carried out in a single dispersion, or, from the viewpoint of obtaining a uniform pigment dispersion, it may be carried out by pre-dispersion followed by final dispersion using a disperser. There are no particular limitations on the aforementioned disperser, and examples include kneading and mixing devices such as kneaders; media-type dispersers such as attritors, ball mills, sand mills using glass beads or zirconia beads, paint shakers, etc.; and colloid mills. From the viewpoint of reducing the viscosity of the pigment dispersion, the temperature of the dispersion treatment is preferably maintained at 10°C to 35°C, more preferably 15°C to 30°C, and even more preferably 18°C ​​to 27°C. From the viewpoint of sufficiently finely milling the pigment, the dispersion treatment time is preferably 2 hours to 200 hours, and more preferably 3 hours to 50 hours.

[0046] The content of aluminum lake pigment (A) in the pigment dispersion of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, from the viewpoint of the storage stability of the pigment dispersion at room temperature and at high temperature, and from the same viewpoint as above, preferably 20% by mass or less, more preferably 17% by mass or less, and even more preferably 15% by mass or less. The content of the dispersant (B) in the pigment dispersion of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, from the viewpoint of the storage stability of the pigment dispersion at room temperature and at high temperature, and from the same viewpoint as above, preferably 20% by mass or less, more preferably 17% by mass or less, and even more preferably 15% by mass or less. The mass ratio of the content of aluminum lake pigment (A) to the total content of aluminum lake pigment (A) and pigment dispersant (B) in the pigment dispersion of the present invention [aluminum lake pigment (A) / [aluminum lake pigment (A) + pigment dispersant (B)]] is preferably 0.10 or more, more preferably 0.20 or more, even more preferably 0.25 or more, even more preferably 0.30 or more, even more preferably 0.35 or more, even more preferably 0.40 or more, even more preferably 0.45 or more, and preferably 0.90 or less, more preferably 0.85 or less, even more preferably 0.80 or less, even more preferably 0.75 or less, even more preferably 0.70 or less, even more preferably 0.65 or less, even more preferably 0.60 or less, and even more preferably 0.55 or less. From the viewpoint of dispersion stability of the pigment dispersion, the ethanol content in the pigment dispersion of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, and from the same viewpoint as above, preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0047] (Physical properties of ethanol-based pigment dispersions) The volume-average particle size of the aluminum lake pigment (A) dispersed in the pigment dispersion of the present invention is preferably 200 nm or less, more preferably 170 nm or less, even more preferably 150 nm or less, even more preferably 140 nm or less, even more preferably 135 nm or less, and even more preferably 130 nm or less, from the viewpoint of improving dischargeability and decappingability, and preferably 50 nm or more, more preferably 70 nm or more, even more preferably 90 nm or more, and even more preferably 110 nm or more, from the viewpoint of productivity of the pigment dispersion. The volume-average particle size is measured by the method described in the examples. The viscosity of the pigment dispersion of the present invention at 20°C is preferably 1 mPa·s or more, more preferably 1.5 mPa·s or more, even more preferably 2 mPa·s or more, even more preferably 2.5 mPa·s or more, even more preferably 3 mPa·s or more, even more preferably 3.5 mPa·s or more, and even more preferably 4 mPa·s or more, and from the same viewpoint as above, preferably 20 mPa·s or less, more preferably 15 mPa·s or less, even more preferably 13 mPa·s or less, and even more preferably 10 mPa·s or less. The viscosity at 20°C is measured by the method described in the examples. The pH of the pigment dispersion of the present invention at 20°C is preferably 4 or higher, more preferably 4.5 or higher, and even more preferably 5 or higher, from the viewpoint of dispersion stability of the pigment dispersion, and preferably 9 or lower, more preferably 8 or lower, even more preferably 7.5 or lower, and even more preferably 7 or lower, from the viewpoint of dischargeability. The pH at 20°C is measured by the method described in the examples.

[0048] The pigment dispersion of the present invention uses a highly safe aluminum lake pigment (A), and is therefore preferable for use in the food, medical, and cosmetic fields. In particular, the pigment dispersion of the present invention is preferable for use in the cosmetic field. When the pigment dispersion of the present invention is used in the field of cosmetics, it is preferable to use the pigment dispersion in an ethanol-based ink applied to hair, skin (including lips), and nails as a cosmetic composition, and more preferably in an ethanol-based ink applied to hair. Examples of the aforementioned cosmetic compositions include cosmetic compositions for hair, cosmetic compositions for skin, cosmetic compositions for nails, and so on, with the latter being preferable for use as a cosmetic composition for hair. The hair cosmetic composition is preferably used for hair dyes such as hair mascara and hair color; styling products such as hair wax, hair spray, hair mousse, and hair foam; and hair growth products. The skin cosmetic composition is preferably applied to base makeup cosmetics such as makeup bases, foundations, and concealers; point makeup cosmetics such as blush, eyeshadow, mascara, eyeliner, eyebrow products, overcoats, and lipsticks; UV protection cosmetics such as sunscreen lotions and sunscreen creams; skin cleansing cosmetics such as facial cleansers and makeup removers; and basic cosmetics such as serums, masks, and massage cosmetics. As a cosmetic composition for nails, it is preferable to apply it to cosmetic products for beautifying nails, such as nail enamel and nail gloss. Furthermore, when the pigment dispersion of the present invention is used in the cosmetics field, the pigment dispersion can be used in ethanol-based inks used for printing to decorate the surface of packaging containers that contain cosmetics. Examples of such packaging containers include various compact cases that contain powder cosmetics such as foundation, eyeshadow, blush, and eyebrow products.

[0049] The pigment dispersion of the present invention has a reduced particle size of the dispersed pigment, excellent stability at room temperature and high temperature, and can further improve ejection and decapping properties when used in an inkjet recording method; therefore, it is preferable to use it for inkjet recording.

[0050] [Inkjet recording ethanol-based ink] The ethanol-based ink for inkjet recording of the present invention (hereinafter also simply referred to as "ethanol-based ink") preferably contains the ethanol-based pigment dispersion and an ethanol-soluble organic solvent (C) from the viewpoint of improving ejection and decapping properties. In the present invention, "ethanol-soluble organic solvent (C)" refers to an organic solvent that is miscible with ethanol in any ratio.

[0051] <Ethanol-soluble organic solvent (C)> The ethanol-soluble organic solvent (C) (hereinafter also simply referred to as "organic solvent (C)") preferably contains at least one ethanol-soluble organic solvent with a boiling point of 80°C or higher, from the viewpoint of suppressing viscosity increase due to the pigment dispersant and improving discharge and decapping properties. The boiling point of the organic solvent (C) is preferably 100°C or higher, more preferably 150°C or higher, even more preferably 200°C or higher, even more preferably 230°C or higher, even more preferably 250°C or higher, even more preferably 280°C or higher, and preferably 400°C or lower, more preferably 370°C or lower, even more preferably 350°C or lower, and even more preferably 330°C or lower, from the viewpoint of suppressing ink drying in the inkjet nozzle and improving ejection and decapping characteristics. When two or more ethanol-soluble organic solvents are used as organic solvent (C), the boiling point of organic solvent (C) is the weighted average value, weighted by the content (mass%) of each ethanol-soluble organic solvent.

[0052] Examples of organic solvents (C) include monohydric alcohols other than ethanol, polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, etc. Furthermore, polyhydric alcohols can be used by mixing multiple substances included in the concept of polyhydric alcohols, and similarly, it is preferable to use polyhydric alcohol alkyl ethers by mixing multiple substances.

[0053] Examples of monohydric alcohols include 1-propanol (boiling point 97°C), isopropanol (boiling point 83°C), 1-butanol (boiling point 118°C), 2-butanol (boiling point 99°C), and tert-butanol (boiling point 82°C). Monohydric alcohols are thought to promote the dissolution of the polymer film of dispersant B, which is formed on the ink nozzle surface as ethanol evaporates, by maintenance, thereby facilitating the recovery of a good ejection state and improving decapping characteristics. Examples of polyhydric alcohols include ethylene glycol (boiling point 197°C), diethylene glycol (boiling point 244°C), polyethylene glycol, propylene glycol (boiling point 188°C), dipropylene glycol (boiling point 232°C), polypropylene glycol, 1,3-propanediol (boiling point 210°C), 1,3-butanediol (boiling point 208°C), 1,4-butanediol (boiling point 230°C), and 3-methyl-1,3-butanediol. Examples include 1,5-pentanediol (boiling point 242°C), 1,2-hexanediol (boiling point 223°C), 1,6-hexanediol (boiling point 250°C), 2-methyl-2,4-pentanediol (boiling point 196°C), 1,2,6-hexanetriol (boiling point 178°C), 1,2,4-butanetriol (boiling point 190°C), 1,2,3-butanetriol (boiling point 175°C), petriol (boiling point 216°C), etc. Furthermore, it is preferable to use compounds with a boiling point of 250°C or higher, such as triethylene glycol (boiling point 285°C), tripropylene glycol (boiling point 273°C), and glycerin (boiling point 290°C), in combination with compounds with a boiling point of less than 250°C. Furthermore, an alkylene oxide adduct of the polyhydric alcohol may be used as the polyhydric alcohol. For example, a glycerol-modified ethylene oxide adduct is a preferred example of the alkylene oxide adduct of the polyhydric alcohol.

[0054] Examples of polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether (boiling point 135°C), ethylene glycol monobutyl ether (boiling point 171°C), diethylene glycol monomethyl ether (boiling point 194°C), diethylene glycol monoethyl ether (boiling point 202°C), diethylene glycol monobutyl ether (boiling point 230°C), triethylene glycol monomethyl ether (boiling point 122°C), triethylene glycol monoisobutyl ether (boiling point 160°C), tetraethylene glycol monomethyl ether (boiling point 158°C), propylene glycol monoethyl ether (boiling point 133°C), dipropylene glycol monobutyl ether (boiling point 227°C), dipropylene glycol monomethyl ether (boiling point 90°C), tripropylene glycol monomethyl ether (boiling point 100°C), and tripropylene glycol monobutyl ether. Furthermore, it is preferable to use compounds with a boiling point of 250°C or higher, such as triethylene glycol monobutyl ether (boiling point 276°C), in combination with compounds with a boiling point of less than 250°C.

[0055] Examples of nitrogen-containing heterocyclic compounds include N-methyl-2-pyrrolidone (boiling point 202°C), 2-pyrrolidone (boiling point 245°C), 1,3-dimethyl-2-imidazolidinone (boiling point 220°C), and ε-caprolactam (boiling point 136°C). Examples of amides include formamide (boiling point 210°C), N-methylformamide (boiling point 199°C), and N,N-dimethylformamide (boiling point 153°C). Examples of amines include monoethanolamine (boiling point 170°C), diethanolamine (boiling point 217°C), triethanolamine (boiling point 208°C), and triethylamine (boiling point 90°C). Examples of sulfur-containing compounds include dimethyl sulfoxide (boiling point 189°C). It is also preferable to use compounds with a boiling point of 250°C or higher, such as sulfolane (boiling point 285°C) and thiodiglycol (boiling point 282°C), in combination with compounds with a boiling point of less than 250°C.

[0056] Among these, from the viewpoint of suppressing ink drying in the inkjet nozzle and improving ejection and decapping characteristics, it is preferably one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers, more preferably one or more selected from polyhydric alcohols and polyhydric alcohol-modified alkylene oxide adducts, and even more preferably one or more selected from glycerin, 1,2-hexanediol, and glycerin-modified ethylene oxide adducts.

[0057] (Other ingredients) In addition to the aluminum lake pigment (A), dispersant (B), and ethanol-soluble organic solvent (C), the ethanol-based ink of the present invention may contain various additives such as surfactants, wetting agents, penetrating agents, dispersants other than dispersant (B), solvents other than ethanol-soluble organic solvent (C), viscosity modifiers, defoamers, antifungal agents, rust inhibitors, and ultraviolet absorbers. Furthermore, in order to adjust the viscosity of the ink and improve its ejection and decapping properties, the ethanol-based ink of the present invention may also contain ethanol as a solvent other than the ethanol-soluble organic solvent (C), in addition to the ethanol-based pigment dispersion and the ethanol-soluble organic solvent (C).

[0058] The ethanol-based ink of the present invention may further contain a surfactant from the viewpoint of print quality. Examples of surfactants include nonionic surfactants, anionic surfactants, and amphoteric surfactants. One type of surfactant may be used alone or two or more types may be used in combination. Among these, a nonionic surfactant is preferred from the viewpoint of print quality. Examples of nonionic surfactants include: (1) alkyl ethers, alkenyl ethers, alkynyl ethers, or aryl ethers of polyoxyalkylenes obtained by adding ethylene oxide, propylene oxide, or butylene oxide to saturated or unsaturated linear or branched higher alcohols, polyhydric alcohols, or aromatic alcohols having 8 to 22 carbon atoms; (2) esters of polyhydric fatty acids with saturated or unsaturated linear or branched hydrocarbon groups of higher alcohols having 8 to 22 carbon atoms; (3) polyoxyalkylene aliphatic amines having linear or branched alkyl or alkenyl groups having 8 to 20 carbon atoms; (4) ester compounds of polyhydric alcohols with higher fatty acids having 8 to 22 carbon atoms, or compounds obtained by adding ethylene oxide, propylene oxide, or butylene oxide to such ester compounds with polyhydric alcohols; (5) silicone-based surfactants; and (6) acetylene glycol-based surfactants. Among these, the nonionic surfactant is preferably one or more selected from silicone-based surfactants and acetylene glycol-based surfactants, and more preferably a silicone-based surfactant.

[0059] Examples of silicone-based surfactants include polyether-modified silicone, amino-modified silicone, carboxy-modified silicone, fatty acid-modified silicone, alcohol-modified silicone, aliphatic alcohol-modified silicone, epoxy-modified silicone, fluorine-modified silicone, and alkyl-modified silicone. Among these, polyether-modified silicone is preferred from the viewpoint of print quality. Polyether-modified silicones have a structure in which the hydrocarbon groups at the side chains and / or terminals of a silicone oil are replaced with polyether groups. Preferred polyether groups include polyethylene oxy groups, polypropylene oxy groups, and polyalkylene oxy groups in which ethylene oxy groups and propylene oxy groups (trimethylene oxy groups or propane-1,2-diyl oxy groups) are added in a block-like or random manner. As polyether-modified silicones, compounds in which polyether groups are grafted onto a silicone main chain, compounds in which silicone and polyether groups are bonded in a block-like manner, and the like can be used. Examples of polyether-modified silicones include PEG-3 dimethicone, PEG-9 dimethicone, PEG-9 methyl ether dimethicone, PEG-10 dimethicone, PEG-11 methyl ether dimethicone, PEG / PPG-20 / 22 butyl ether dimethicone, PEG-32 methyl ether dimethicone, PEG-9 polydimethylsiloxyethyl dimethicone, and lauryl PEG-9 polydimethylsiloxyethyl dimethicone. Among these, PEG-11 methyl ether dimethicone is preferred.

[0060] Examples of acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, 3,5-dimethyl-1-hexyn-3-ol, and one or more ethylene oxide adducts thereof. Among these, the acetylene glycol-based surfactant is preferably one or more selected from 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, 2,5-dimethyl-3-hexyn-2,5-diol, and their ethylene oxide adducts, and more preferably one or more selected from 2,4,7,9-tetramethyl-5-decine-4,7-diol and its ethylene oxide adduct.

[0061] Examples of commercially available nonionic surfactants include the KF series from Shin-Etsu Chemical Co., Ltd.; the Surfinol series from Nisshin Chemical Industry Co., Ltd. and Air Products & Chemicals; the Acetyleneol series from Kawaken Fine Chemical Co., Ltd.; and "Emulgen 120 (polyoxyethylene lauryl ether)" from Kao Corporation.

[0062] (Manufacturing of ethanol-based inks for inkjet recording) A preferred method for producing the ethanol-based ink of the present invention is to mix the ethanol-based pigment dispersion, an ethanol-soluble organic solvent (C), ethanol as needed, and various additives. Further filtration using a filter or the like may also be performed. The content of each component and the ink properties in the ethanol-based ink of the present invention are as follows.

[0063] (Content of aluminum lake pigment (A)) The content of the aluminum lake pigment (A) in the ethanol-based ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of coloration, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 7% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of improving discharge and decapping properties.

[0064] (Content of pigment dispersant (B)) The content of the dispersant (B) in the ethanol-based ink of the present invention is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, even more preferably 1% by mass or more, even more preferably 2% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, even more preferably 5% by mass or less, and even more preferably 4.5% by mass or less, from the viewpoint of improving the dispersion stability of the ethanol-based ink and improving the discharge and decapping properties. The mass ratio of the content of aluminum lake pigment (A) to the total content of aluminum lake pigment (A) and pigment dispersant (B) in the ethanol-based ink of the present invention [aluminum lake pigment (A) / [aluminum lake pigment (A) + pigment dispersant (B)]] is preferably 0.10 or more, more preferably 0.20 or more, even more preferably 0.25 or more, even more preferably 0.30 or more, even more preferably 0.35 or more, even more preferably 0.40 or more, even more preferably 0.45 or more, and also preferably 0.90 or less, more preferably 0.85 or less, even more preferably 0.80 or less, even more preferably 0.75 or less, even more preferably 0.70 or less, even more preferably 0.65 or less, even more preferably 0.60 or less, and even more preferably 0.55 or less.

[0065] (Content of ethanol-soluble organic solvent (C)) The content of the ethanol-soluble organic solvent (C) in the ethanol-based ink of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 13% by mass or more, from the viewpoint of improving discharge and decapping properties, and from the same viewpoint as above, preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0066] (Ethanol content) The ethanol content in the ethanol-based ink of the present invention is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of improving discharge and decapping properties, and also preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less, from the same viewpoint as above.

[0067] (Glycerin content) When the ethanol-based ink of the present invention contains glycerin as the ethanol-soluble organic solvent (C), the glycerin content in the ethanol-based ink is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of improving discharge and decapping properties, and also preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0068] (Surfactant content) When the ethanol-based ink of the present invention contains a surfactant, the amount of the surfactant in the ethanol-based ink is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, from the viewpoint of adjusting the dot diameter and improving print quality, and also preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.7% by mass or less, from the same viewpoint as above.

[0069] (Water content) Furthermore, when a neutralizing agent aqueous solution is used to neutralize the anionic groups in the production of the ethanol-based pigment dispersion, the resulting ethanol-based pigment dispersion may contain water. Therefore, the ethanol-based ink of the present invention may contain water introduced from the ethanol-based pigment dispersion. When the ethanol-based ink of the present invention contains water, the amount of water in the ethanol-based ink is preferably 3% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, even more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less.

[0070] (Physical properties of ethanol-based inks) The volume-average particle size of the aluminum lake pigment (A) dispersed in the ethanol-based ink of the present invention is preferably 200 nm or less, more preferably 170 nm or less, even more preferably 150 nm or less, even more preferably 140 nm or less, even more preferably 135 nm or less, and even more preferably 130 nm or less, from the viewpoint of improving discharge and decapping properties, and preferably 50 nm or more, more preferably 70 nm or more, even more preferably 90 nm or more, and even more preferably 110 nm or more, from the viewpoint of productivity of the ethanol-based ink. The volume-average particle size is measured by the method described in the examples. The viscosity of the ethanol-based ink of the present invention at 20°C is preferably 1.0 mPa·s or more, more preferably 1.5 mPa·s or more, even more preferably 2.0 mPa·s or more, even more preferably 2.5 mPa·s or more, even more preferably 3.0 mPa·s or more, and even more preferably 3.5 mPa·s or more, from the viewpoint of improving ejection and decapping properties, and also preferably 12 mPa·s or less, more preferably 9.0 mPa·s or less, even more preferably 7.0 mPa·s or less, even more preferably 5.5 mPa·s or less, and even more preferably 4.5 mPa·s or less. The viscosity of the ethanol-based ink at 20°C is measured by the method described in the examples. The pH of the ethanol-based ink of the present invention at 20°C is preferably 4 or higher, more preferably 4.5 or higher, and even more preferably 5 or higher, from the viewpoint of dispersion stability of the ethanol-based ink, and preferably 9 or lower, more preferably 8 or lower, even more preferably 7.5 or lower, and even more preferably 7 or lower, from the viewpoint of discharge performance. The pH of the ethanol-based ink at 20°C is measured by the same method as the pH of the pigment dispersion described in the examples.

[0071] (Inkjet recording method) The inkjet recording method using the ethanol-based ink of the present invention is preferably a method of recording by ejecting the ethanol-based ink onto a recording medium using an inkjet recording device. Since the aluminum lake pigment (A) according to the present invention is a pigment with a relatively low specific gravity, an inkjet recording device without dispersion means may be used. However, it is preferable to use an inkjet recording device that has dispersion means for dispersing the aluminum lake pigment (A) in the ethanol-based ink. The dispersion means is not particularly limited as long as it is a means for dispersing the aluminum lake pigment (A) in the ethanol-based medium of the ethanol-based ink by mechanical force.

[0072] If the inkjet recording apparatus has a dispersion means, the inkjet recording method preferably includes a step 1 of redispersing the ethanol-based ink using the dispersion means, and a step 2 of ejecting the ethanol-based ink redispersed in step 1 and recording it on a recording medium. In the inkjet recording method described above, by using the ethanol-based ink, even if the aluminum lake pigment (A) dispersed in the ethanol-based ink settles or aggregates during or after printing, the dispersion means of the inkjet recording device can easily redisperse the aluminum lake pigment (A), thereby improving ejection performance and decapping characteristics. From this viewpoint, the inkjet recording device preferably includes at least an ink ejection means, a container for filling the ethanol-based ink (ink-filling container), an ink channel, and a dispersion means for dispersing the aluminum lake pigment (A) contained in the ethanol-based ink, and the ink-filling container may further include an ink pre-filling container.

[0073] As an ink ejection means, there are methods of ejecting ink using a thermal or piezo inkjet ejection head. From the viewpoint of ejection performance and decapping characteristics, the thermal method is preferred. That is, in the inkjet recording method of the present invention, it is preferable to use the ethanol-based ink for the thermal method, attach a container filled with the ethanol-based ink to an inkjet recording device, and eject the ethanol-based ink using a thermal ejection head to record it on a recording medium.

[0074] There are no particular restrictions on the recording medium, but examples include recording media used in printing in the food, medical, and cosmetic fields. Examples include highly absorbent recording media such as plain paper and fine paper; low absorbent recording media such as art paper, coated paper, and synthetic resin film; and metals. Furthermore, when the ethanol-based ink of the present invention is used as a cosmetic composition, hair, skin (including lips), and nails can also be used as recording media. Preferred embodiments of the cosmetic composition that can be used are as exemplified in the pigment dispersion described above. Furthermore, when the ethanol-based ink of the present invention is used as an ethanol-based ink for printing to decorate the surface of packaging containers that contain cosmetics, as mentioned above, examples include various packaging containers such as various compact cases that contain powder cosmetics such as foundation, eyeshadow, blush, and eyebrow products. [Examples]

[0075] In the following manufacturing examples, embodiments, and comparative examples, "parts" and "%" refer to "parts by mass" and "mass%" respectively, unless otherwise specified. The various physical properties were measured using the following method.

[0076] (1) Measurement of the acid value of the pigment dispersant (B) The measurement was performed in accordance with the potentiometric titration method of JIS K 0070.

[0077] (2) Measurement of the weight-average molecular weight of the pigment dispersant (B) Using a 0.2 M phosphate buffer / acetonitrile = 9 / 1 (volume ratio) solution as the eluent, the measurement was performed by gel permeation chromatography [GPC instrument (HLC-8320GPC) manufactured by Tosoh Corporation, column (PW+G4000PW+G2500PW) manufactured by Tosoh Corporation, flow rate: 1.0 mL / min, temperature: 40°C], with polyethylene glycol, whose weight-average molecular weight had been previously determined in monodisperse form, as the standard substance.

[0078] (3) Measurement of solid content concentration 10.0 g of sodium sulfate, which had been stabilized in a desiccator, was weighed into a 30 mL polypropylene container (φ=40 mm, height=30 mm). Approximately 1.0 g of the sample was added and mixed, then accurately weighed. The mixture was maintained at 105°C for 2 hours to remove volatile components, and then left in the desiccator for another 15 minutes before the mass was measured. The mass of the sample after removal of volatile components was taken as the solid content, and the solid content concentration (%) was obtained by dividing it by the mass of the added sample.

[0079] (4) Measurement of volume-average particle size of ethanol-based pigment dispersion or ethanol-based ink The volume-average particle size of ethanol-based pigment dispersions or ethanol-based inks was determined using the zeta potential / particle size measurement system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.) at a concentration of approximately 5 × 10⁻⁶. -3 A dispersion diluted with water to a certain percentage was placed in a measurement cell, and measurements were taken at a temperature of 25°C and with 100 cumulative measurements. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

[0080] (5) Viscosity of ethanol-based pigment dispersion or ethanol-based ink Viscosity was measured at 20°C using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard cone rotor 1°34'×R24, rotation speed 50 rpm). (6) pH of ethanol-based pigment dispersion The pH of an ethanol-based pigment dispersion at 20°C was measured using a benchtop pH meter "F-71" (manufactured by Horiba, Ltd.) equipped with a pH electrode "6337-10D" (manufactured by Horiba, Ltd.).

[0081] Manufacturing Example 1 (Preparation of a solution of pigment dispersant (B-1)) 233 g of isopropanol was placed in a 2 L glass reaction vessel equipped with two dropping funnels 1 and 2, and the vessel was purged with nitrogen gas. On the other hand, a monomer solution was prepared using 15 g of acrylic acid (reagent, Wako Special Grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as monomer (b-1) and 85 g of methoxypolyethylene glycol monomethacrylate (average number of moles of ethylene oxide (EO) added n=23, manufactured by NOF Corporation, trade name "Bremmer PME-1000") as monomer (b-2). This solution was placed in dropping funnel 1 and purged with nitrogen gas. Separately, a polymerization initiator solution was prepared by mixing 1.0 g of dilauroyl peroxide (manufactured by NOF Corporation, trade name "Perloyl L") with 10.0 g of isopropanol as a polymerization initiator. This solution was placed in dropping funnel 2 and purged with nitrogen gas. Next, under a nitrogen atmosphere, the isopropanol in the reaction vessel was stirred and maintained at 80°C. Polymerization was carried out by gradually adding the monomer solution in dropping funnel 1 and the polymerization initiator solution in dropping funnel 2 to the reaction vessel simultaneously over a period of 6 hours, thereby obtaining a polymerization reaction solution. Next, the pressure inside the reaction vessel was adjusted to 50 kPa and the temperature inside the reaction vessel to 60°C. Isopropanol was then distilled off from the resulting polymerization reaction solution, and the polymerization reaction solution was concentrated until the solid content concentration reached 90%. Next, the pressure inside the reaction vessel was adjusted to atmospheric pressure and the temperature inside the reaction vessel to 60°C. Under a nitrogen atmosphere, a polymerization initiator solution was added, which consisted of 0.7 g of dilauroyl peroxide (Perloyl L) mixed with 10.0 g of isopropanol, and the mixture was stirred for 1 hour. Next, the pressure inside the reaction vessel was adjusted to 2 kPa and the temperature inside the reaction vessel to 60°C, and the isopropanol was distilled off, concentrating the polymerization reaction solution until the solid content concentration reached 99% or higher. Next, while maintaining a pressure of 2 kPa inside the reaction vessel, the temperature inside the reaction vessel was raised to 65°C and then maintained at 65°C for 46 hours of heating and aging. Subsequently, the temperature inside the reaction vessel was cooled to 40°C, 200g of primary ethanol was added and stirred, and the polymer inside the reaction vessel was redissolved. Next, 1.74 g of a 48% sodium hydroxide aqueous solution (834 mg of sodium hydroxide) was added to the reaction vessel to neutralize the polymer, and then primary ethanol was added to bring the solid content concentration to 20% to obtain an ethanol solution of the pigment dispersant (B-1).

[0082] Manufacturing Examples 2-13, C1 (Preparation of solutions of pigment dispersants (B-2)-(B-13), (B-C1)) In Production Example 1, ethanol solutions of pigment dispersants (B-2) to (B-13) and (B-C1) were obtained in the same manner as shown in Table 1, except that the monomer composition and the amount of sodium hydroxide added were changed. The details of the monomers in Table 1 are as follows. Acrylic acid: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade. Methacrylic acid: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade. MPEGMAA (n=23): Methoxypolyethylene glycol monomethacrylate (average number of EO added moles = 23, manufactured by NOF Corporation, "Bremmer PME-1000") Ethyl methacrylate: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade. n-butyl methacrylate: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Grade 1. Methyl acrylate: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade. n-butyl acrylate: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Wako Special Grade. n-hexyl acrylate: Reagent manufactured by Polyscience, Inc., purity 98% or higher.

[0083] [Table 1]

[0084] Example 1-1 (Ethanol-based pigment dispersion P-1) In a 250 mL polypropylene bottle, 50 parts of the pigment dispersant (B-1) solution (solid content concentration 20%) obtained in Production Example 1 (10 parts of effective pigment dispersant (B-1)), 10 parts of aluminum lake pigment A-1 ["BC Yellow No. 4 AL" (Yellow No. 4 Aluminum Lake, manufactured by Kiseki Kasei Co., Ltd.)], and 40 parts of ethanol were added. 200 g of 50 μm diameter zirconia beads were added, and the mixture was dispersed in a paint shaker at 25°C for 15 hours. The zirconia beads were removed using a 75 μm mesh, and the solid content concentration was adjusted to obtain pigment dispersion P-1 (solid content concentration 20%).

[0085] Examples 1-2 to 1-13 and Comparative Example 1-1 (Ethanol-based pigment dispersions P-2 to P-13 and P-C1) In Example 1-1, the same procedure was followed except that the pigment dispersant (B) solution shown in Table 2 was used to obtain ethanol-based pigment dispersions P-2 to P-13 and P-C1 (solid content concentration 20%). The obtained ethanol-based pigment dispersions were evaluated as follows.

[0086] [evaluation] <Effect of reducing the particle size of dispersed pigments> [Volume-average particle size] The volume-average particle size of the pigment dispersions in Examples 1-1 to 1-13 and Comparative Example 1-1 was measured. The results are shown in Table 2. The smaller the volume-average particle size, the greater the effect of reducing the particle size of the pigment dispersion, and a volume-average particle size of 200 nm or less indicates an excellent effect of reducing the particle size of the pigment dispersion.

[0087] 〔viscosity〕 The viscosity of the pigment dispersions from Examples 1-1 to 1-13 and Comparative Example 1-1 was measured. The results are shown in Table 2. The viscosities of the pigment dispersions P-1 to P-13 in the examples were all 20 mPa·s or less, and when the pigment dispersions were filtered using a cellulose acetate syringe filter with a pore size of 5 μm, no decrease in filtration rate due to pressure loss occurred. This also indicates that the particle size of the dispersed pigments has been reduced. On the other hand, the comparative example pigment dispersion P-C1 had high viscosity, and when attempting to filter it using the same method as described above, pressure loss made it difficult to pass the liquid through.

[0088] <Evaluation of storage stability at room temperature> The pigment dispersions of Examples 1-1 to 1-13 and Comparative Example 1-1 were left to stand at room temperature (25°C), and the presence or absence of sediment was visually confirmed. The room temperature storage stability was evaluated according to the following evaluation criteria. The results are shown in Table 2. A: No sediment had formed even after being left undisturbed at room temperature for one week. B: Sedimentation was observed 24 hours after the start of standing at room temperature, but no clear supernatant layer was observed after standing at room temperature for one week. C: Settlement was observed 24 hours after the start of standing at room temperature, and a clear supernatant layer was observed after standing at room temperature for one week.

[0089] <Evaluation of high-temperature storage stability> The pigment dispersions of Examples 1-1 to 1-13 and Comparative Example 1-1 were sealed in glass screw tubes and left to stand in a 60°C constant temperature bath for 4 weeks. After that, the volume-average particle size and viscosity were measured, and the particle size retention rate (%) and viscosity retention rate (%) were calculated using the following formulas. The results are shown in Table 2. The closer the particle size retention rate (%) and viscosity retention rate (%) are to 100%, the better the high-temperature storage stability. Particle size retention rate (%) = [Volume-average particle size after storage (nm) / Volume-average particle size before storage (nm)] × 100 Viscosity retention rate (%) = [Viscosity after storage (mPa·s) / Viscosity before storage (mPa·s)] × 100 Furthermore, visual inspection of the fluidity of the pigment dispersions after storage confirmed that pigment dispersions P-1 to P-13 in the examples maintained their fluidity even after storage. On the other hand, the comparative example pigment dispersion P-C1 was unable to maintain its fluidity after storage and had gelled.

[0090] [Table 2]

[0091] Table 2 shows that the pigment dispersions of the examples exhibit a greater effect in reducing the particle size of the dispersed pigments compared to the comparative examples, and also demonstrate superior stability at room temperature and high temperatures. Furthermore, in the evaluation of high-temperature storage stability, the pigment dispersions of the examples showed a particle size retention rate of 110% or less and a viscosity retention rate of 110% or less. This indicates that even high-concentration pigment dispersions with a solid content of 20% can be stored at high temperatures for extended periods.

[0092] Example 2-1 (Ethanol-based ink I-1) Using the pigment dispersion P-1 (solid content concentration 20%) obtained in Example 1-1, the following composition was used to mix the aluminum lake pigment (A) and pigment dispersant (B) in the ethanol-based ink so that the content of each was 4%. The resulting mixture was filtered using a 20 mL needleless syringe fitted with a cellulose acetate filter with a pore size of 1.2 μm (outer diameter 2.5 cm, manufactured by Sartorius Co., Ltd.) to remove coarse particles and obtain ethanol-based ink I-1. The viscosity of ethanol-based ink I-1 at 20°C was 4.1 mPa·s. <Composition> Ethanol-based pigment dispersion P-1 (containing 4 parts of aluminum lake pigment A-1 and 4 parts of pigment dispersant B-1) 40 parts Glycerin (boiling point 290°C) 10 parts Liponic EG-1 (product name of Lipo Chemicals, glycerin-modified EO adduct (average number of EO added moles: 26), boiling point 381°C) 3 parts 1,2-Hexanediol (boiling point 223°C) 3 parts KF-6011 (product name of Shin-Etsu Chemical Co., Ltd., polyether-modified silicone) 0.5 parts Ethanol 43.5 parts

[0093] Examples 2-2 to 2-13 and Comparative Example 2-1 (Ethanol-based inks I-2 to I-13 and I-C1) In Example 2-1, the pigment dispersions shown in Table 3 were used instead of pigment dispersion P-1, and the amount of glycerin was adjusted to the amount shown in Table 3 so that the viscosity at 20°C was between 4.0 and 4.4 mPa·s. The amount of the remaining ethanol was adjusted, but otherwise, each ethanol-based ink was obtained in the same manner. However, in Comparative Example 2-1, the viscosity did not decrease sufficiently with glycerin alone, so Liponic EG-1 and 1,2-hexanediol were also reduced, but the viscosity remained at 8.9 mPa·s.

[0094] <Evaluation of discharge capacity> Each ethanol-based ink from Examples 2-1 to 2-13 and Comparative Example 2-1 was filled into an HP62 inkjet cartridge (manufactured by HP Corporation) that had been thoroughly cleaned and dried with deionized water beforehand. A solid image measuring 12.8 mm in height and 30 mm in width was then printed on plain paper at 100% duty cycle using an HP OfficeJet 200 Mobile mobile inkjet printer (manufactured by HP Corporation, printing method: thermal). All of the ethanol-based inks I-1 to I-13 used in the examples were able to be dispensed without any problems. On the other hand, in the comparative example, the ethanol-based ink I-C1 had a high viscosity due to the pigment dispersion P-C1 used. Even when the glycerin content in the ink was reduced to 0%, the desired viscosity was not achieved, and the ink head channel inside the cartridge was not filled, making it impossible to evaluate the ejection performance. This is thought to be because the pigment dispersant used in the pigment dispersion P-C1 does not have constituent units derived from hydrophilic nonionic monomers (b-2), and therefore the viscosity of the pigment dispersion was not sufficiently reduced. The results are shown in Table 3 using the following notation. A: The ink was ejected without any problems, and I was able to print a solid image. B: The ink could not be ejected, and therefore the solid image could not be printed.

[0095] <Evaluation of decapping characteristics> Using ink cartridges filled with each of the ethanol-based inks from Examples 2-1 to 2-13 and Comparative Example 2-1, a solid image measuring 12.8 mm in height and 30 mm in width was printed at 100% duty cycle. After printing, a nozzle check pattern was printed to confirm that all nozzles were printing. Next, the ink cartridges were left in the printer for 30 minutes in a windless environment at a temperature of 25°C and 50% humidity. Then, a head cleaning operation was performed once, and a nozzle check was performed again to confirm the percentage of nozzles that were ejecting ink (recovery rate). If the percentage of nozzles that were ejecting ink was 90% or higher, maintenance was considered complete, and the percentage of nozzles that were ejecting ink was recorded. If the percentage of nozzles that were ejecting ink was less than 90%, the maintenance operation and nozzle check were repeated. However, since the comparative example ink underwent maintenance six times but the number of nozzles was still less than 90%, the percentage of nozzles that ejected ink after six maintenance cycles was recorded. The percentage of nozzles that were ejecting ink was 24%. The fewer times maintenance is required, the better the decapping characteristics. Furthermore, a higher recovery rate leads to improved print quality. The results are shown in Table 3.

[0096] [Table 3]

[0097] Table 3 shows that the ethanol-based inks in the examples exhibit superior ejection and decapping characteristics compared to the comparative examples.

[0098] Examples 3-1 to 3-4 (Ethanol-based pigment dispersions P-14 to P-17) In Example 1-1, ethanol-based pigment dispersions P-14 to P-17 (solid content concentration 20%) were obtained in the same manner as in Example 1-1, except that the amount of aluminum lake pigment (A) and the type of solution and amount of solid content of the pigment dispersant (B) shown in Table 4 were changed.

[0099] [evaluation] <Effect of reducing the particle size of dispersed pigments> [Volume-average particle size] The volume-average particle size of each ethanol-based pigment dispersion in Examples 3-1 to 3-4 was measured. The results are shown in Table 4. 〔viscosity〕 The viscosity of each ethanol-based pigment dispersion from Examples 3-1 to 3-4 was measured. The results are shown in Table 4. The viscosities of ethanol-based pigment dispersions P-14 to P-17 were all 20 mPa·s or less, and when the ethanol-based pigment dispersions were filtered using a cellulose acetate syringe filter with a pore size of 5 μm, no decrease in filtration rate due to pressure loss occurred. This also indicates that the particle size of the dispersed pigments has been reduced.

[0100] <Evaluation of storage stability at room temperature> The pigment dispersions of Examples 3-1 to 3-4 were left to stand at room temperature, and the presence or absence of sediment was visually confirmed. The room-temperature storage stability was evaluated according to the evaluation criteria described above. The results are shown in Table 4.

[0101] <Evaluation of high-temperature storage stability> Each of the ethanol-based pigment dispersions from Examples 3-1 to 3-4 was sealed in a glass screw tube and left to stand in a 60°C constant temperature bath for 4 weeks. After that, the volume-average particle size and viscosity were measured, and the particle size retention rate (%) and viscosity retention rate (%) were determined using the above formula. The results are shown in Table 4. Furthermore, visual inspection of the fluidity of the ethanol-based pigment dispersions after storage confirmed that ethanol-based pigment dispersions P-14 to P-17 maintained their fluidity after storage.

[0102] [Table 4]

[0103] Table 4 shows that the pigment dispersions of the examples exhibit a high effect in reducing the particle size of the dispersed pigments, and also have excellent stability at room temperature and high temperature.

[0104] Examples 4-1 to 4-4 (Ethanol-based inks I-14 to I-17) In Example 2-1, instead of ethanol-based pigment dispersion P-1, the ethanol-based pigment dispersions shown in Table 5 were used, and the amount of glycerin was adjusted to the amount shown in Table 5 so that the viscosity at 20°C was between 4.0 and 4.4 mPa·s. The amount of the remaining ethanol was adjusted, but otherwise, each ethanol-based ink was obtained in the same manner. The ejection and decapping characteristics described above were evaluated using each of the obtained ethanol-based inks. The results are shown in Table 5.

[0105] [Table 5]

[0106] Table 5 shows that the ethanol-based inks in the examples exhibit excellent ejection and decapping characteristics.

[0107] Manufacturing Examples 14-21 (Manufacturing of Pigment Dispersants B-14-B-21) Solutions of pigment dispersants B-14 to B-21 were obtained in the same manner as in Production Example 1, except that the monomer composition shown in Table 6 and the amount of sodium hydroxide used for neutralization were changed.

[0108] [Table 6]

[0109] Examples 5-1 to 5-8 (Ethanol-based pigment dispersions P-18 to P-25) In Example 1-1, the same procedure was followed except that the pigment dispersant (B) solution shown in Table 7 was used to obtain ethanol-based pigment dispersions P-18 to P-25 (solid content concentration 20%) shown in Table 7.

[0110] [evaluation] <Evaluation of the effect of reducing the particle size of dispersed pigments> [Volume-average particle size] The volume-average particle size of each ethanol-based pigment dispersion in Examples 5-1 to 5-8 was measured. The results are shown in Table 7. 〔viscosity〕 The viscosity of each ethanol-based pigment dispersion from Examples 5-1 to 5-8 was measured. The results are shown in Table 7. The viscosities of ethanol-based pigment dispersions P-18 to P-25 were all 20 mPa·s or less. When the ethanol-based pigment dispersions were filtered using a cellulose acetate syringe filter with a pore size of 5 μm, no decrease in filtration rate due to pressure loss occurred. This also indicates that the particle size of the dispersed pigments has been reduced.

[0111] <Evaluation of storage stability at room temperature> The pigment dispersions of Examples 5-1 to 5-8 were left to stand at room temperature, and the presence or absence of sediment was visually confirmed. The room-temperature storage stability was evaluated according to the evaluation criteria described above. The results are shown in Table 7.

[0112] <Evaluation of high-temperature storage stability> Each ethanol-based pigment dispersion from Examples 5-1 to 5-8 was sealed in a glass screw tube and left to stand in a 60°C constant temperature bath for 4 weeks. After that, the volume-average particle size and viscosity were measured, and the particle size retention rate (%) and viscosity retention rate (%) were determined using the above formula. The results are shown in Table 7. Furthermore, visual inspection of the fluidity of the ethanol-based pigment dispersions after storage confirmed that ethanol-based pigment dispersions P-18 to P-25 maintained their fluidity after storage.

[0113] [Table 7]

[0114] Table 7 shows that the pigment dispersions of the examples exhibit a high effect in reducing the particle size of the dispersed pigments, and also have excellent stability at room temperature and high temperature. Furthermore, in the evaluation of high-temperature storage stability, the pigment dispersions of the examples showed a particle size retention rate of 110% or less and a viscosity retention rate of 110% or less. This indicates that even high-concentration pigment dispersions with a solid content of 20% can be stored at high temperatures for extended periods.

[0115] Examples 6-1 to 6-8 (Ethanol-based inks I-18 to I-25) In Example 2-1, instead of ethanol-based pigment dispersion P-1, the pigment dispersions shown in Table 8 were used, and the amount of glycerin was adjusted to the amount shown in Table 8 so that the viscosity at 20°C was between 4.0 and 4.4 mPa·s. The amount of the remaining ethanol was also adjusted, but otherwise, each ethanol-based ink was obtained in the same manner. The ejection and decapping characteristics described above were evaluated using each of the obtained ethanol-based inks. The results are shown in Table 8.

[0116] [Table 8]

[0117] Table 8 shows that the ethanol-based inks in the examples exhibit excellent ejection and decapping characteristics.

[0118] Examples 7-1 to 7-3 (Ethanol-based pigment dispersions P-26 to P-28) In Example 1-1, aluminum lake pigments A-2 to A-4 were used instead of aluminum lake pigment A-1, and the type of pigment dispersant was changed from B-1 to the pigment dispersants shown in Table 9. The same procedure was followed to obtain ethanol-based pigment dispersions P-26 to P-28 (solid content concentration 20%). • A-2: "SunCROMA FD&C Yellow 6 AL Lake" (Yellow No. 5 Aluminum Lake, manufactured by Sun Chemical) • A-3: "SunCROMA FD&C Blue 1 AL Lake" (Blue No. 1 Aluminum Lake, manufactured by Sun Chemical) • A-4: "SunCROMA FD&C Red 28 AL Lake" (Red No. 104-1 Aluminum Lake, Sun Chemical) [evaluation] <Evaluation of the effect of reducing the particle size of dispersed pigments> [Volume-average particle size] The volume-average particle size of each ethanol-based pigment dispersion in Examples 7-1 to 7-3 was measured. The results are shown in Table 9. 〔viscosity〕 The viscosity of each ethanol-based pigment dispersion from Examples 7-1 to 7-3 was measured. The results are shown in Table 9. The viscosities of ethanol-based pigment dispersions P-26 to P-28 were all 20 mPa·s or less, and when the ethanol-based pigment dispersions were filtered using a cellulose acetate syringe filter with a pore size of 5 μm, no decrease in filtration rate due to pressure loss occurred. This also indicates that the particle size of the dispersed pigments has been reduced.

[0119] <Evaluation of storage stability at room temperature> The pigment dispersions of Examples 7-1 to 7-3 were left to stand at room temperature, and the presence or absence of sediment was visually confirmed. The room-temperature storage stability was evaluated according to the evaluation criteria described above. The results are shown in Table 9.

[0120] <Evaluation of high-temperature storage stability> Each ethanol-based pigment dispersion from Examples 7-1 to 7-3 was sealed in a glass screw tube and left to stand in a 60°C constant temperature bath for 4 weeks. After that, the volume-average particle size and viscosity were measured, and the particle size retention rate (%) and viscosity retention rate (%) were determined using the above formula. The results are shown in Table 9. Furthermore, visual inspection of the fluidity of the ethanol-based pigment dispersions after storage confirmed that ethanol-based pigment dispersions P-26 to P-28 maintained their fluidity after storage.

[0121] [Table 9]

[0122] Table 9 shows that the pigment dispersions of the examples exhibit a high effect in reducing the particle size of the dispersed pigments, and also have excellent stability at room temperature and high temperature. Furthermore, in the evaluation of high-temperature storage stability, the pigment dispersions of the examples showed a particle size retention rate of 110% or less and a viscosity retention rate of 110% or less. This indicates that even high-concentration pigment dispersions with a solid content of 20% can be stored at high temperatures for extended periods.

[0123] Examples 8-1 to 8-3 (Ethanol-based inks I-26 to I-28) In Example 2-1, instead of ethanol-based pigment dispersion P-1, the pigment dispersions shown in Table 10 were used, and the amount of glycerin was adjusted to the amount shown in Table 10 so that the viscosity at 20°C was between 4.0 and 4.4 mPa·s. The amount of the remaining ethanol was also adjusted, but otherwise, each ethanol-based ink was obtained in the same manner. The ejection and decapping characteristics described above were evaluated using each of the obtained ethanol-based inks. The results are shown in Table 10.

[0124] [Table 10]

[0125] Table 10 shows that the ethanol-based inks in the examples exhibit excellent ejection and decapping characteristics.

[0126] Manufacturing Examples 22-26 (Manufacturing of Pigment Dispersants B-22-B-26) Solutions of pigment dispersants B-22 to B-26 were obtained in the same manner as in Production Example 1, except that the monomer composition shown in Table 11 and the amount of sodium hydroxide used for neutralization were changed.

[0127] [Table 11]

[0128] Examples 9-1 to 9-5 (Ethanol-based pigment dispersions P-29 to P-33) In Example 1-1, the same procedure was followed except that the pigment dispersant (B) solution shown in Table 12 was used, to obtain ethanol-based pigment dispersions P-29 to P-33 (solid content concentration 20%) shown in Table 12.

[0129] [evaluation] <Evaluation of the effect of reducing the particle size of dispersed pigments> [Volume-average particle size] The volume-average particle size of each ethanol-based pigment dispersion from Examples 9-1 to 9-5 was measured. The results are shown in Table 12. 〔viscosity〕 The viscosity of each ethanol-based pigment dispersion from Examples 9-1 to 9-5 was measured. The results are shown in Table 12. The viscosity of ethanol-based pigment dispersions P-29 to P-33 was 20 mPa·s or less, and when the ethanol-based pigment dispersions were filtered using a cellulose acetate syringe filter with a pore size of 5 μm, no decrease in filtration rate due to pressure loss occurred. This also indicates that the particle size of the dispersed pigments has been reduced.

[0130] <Evaluation of storage stability at room temperature> The pigment dispersions of Examples 9-1 to 9-5 were left to stand at room temperature, and the presence or absence of sediment was visually confirmed. The room-temperature storage stability was evaluated according to the evaluation criteria described above. The results are shown in Table 12.

[0131] <Evaluation of high-temperature storage stability> Each ethanol-based pigment dispersion from Examples 9-1 to 9-5 was sealed in a glass screw tube and left to stand in a 60°C constant temperature bath for 4 weeks. After that, the volume-average particle size and viscosity were measured, and the particle size retention rate (%) and viscosity retention rate (%) were determined using the above formula. The results are shown in Table 12. Furthermore, visual inspection of the fluidity of the ethanol-based pigment dispersions after storage confirmed that ethanol-based pigment dispersions P-29 to P-33 maintained their fluidity after storage.

[0132] [Table 12]

[0133] Table 12 shows that the pigment dispersions of the examples exhibit a high effect in reducing the particle size of the dispersed pigments, and also have excellent stability at room temperature and high temperature. Furthermore, in the evaluation of high-temperature storage stability, the pigment dispersions of the examples showed a particle size retention rate of 110% or less and a viscosity retention rate of 110% or less. This indicates that even high-concentration pigment dispersions with a solid content of 20% can be stored at high temperatures for extended periods.

[0134] Examples 10-1 to 10-5 (Ethanol-based inks I-29 to I-33) In Example 2-1, instead of ethanol-based pigment dispersion P-1, the pigment dispersions shown in Table 13 were used, and the amount of glycerin was adjusted to the amount shown in Table 13 so that the viscosity at 20°C was between 4.0 and 4.4 mPa·s. The amount of the remaining ethanol was also adjusted, but otherwise, each ethanol-based ink was obtained in the same manner. The ejection and decapping characteristics described above were evaluated using each of the obtained ethanol-based inks. The results are shown in Table 13.

[0135] [Table 13]

[0136] Table 13 shows that the ethanol-based inks in the examples exhibit excellent ejection and decapping characteristics. [Industrial applicability]

[0137] According to the present invention, it is possible to provide an ethanol-based pigment dispersion with a small particle size of pigment and excellent storage stability at room temperature and high temperature. Ethanol-based inks containing this ethanol-based pigment dispersion have excellent ejection properties and decapping characteristics, making them suitable as ethanol-based inks for inkjet recording. Because the ethanol-based pigment dispersion of the present invention uses a highly safe aluminum lake pigment (A), it can be used in the food industry, the medical industry, and the cosmetics industry for skin, hair, nails, etc.

Claims

1. An ethanol-based pigment dispersion containing an aluminum lake pigment (A) and a pigment dispersant (B), The pigment dispersant (B) is a polymer comprising a structural unit derived from an anionic group-containing monomer (b-1) and a structural unit derived from a hydrophilic nonionic monomer (b-2) containing an oxyalkylene group. At least a portion of the anionic groups of the pigment dispersant (B) are neutralized. The constituent units derived from the hydrophilic nonionic monomer (b-2) are constituent units derived from polyalkylene glycol (meth)acrylate represented by the following formula (1), in an ethanol-based pigment dispersion. 【Chemistry 1】 In formula (1) above, R 11 represents a hydrogen atom or a methyl group, R 12 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, OA represents an oxyalkylene group having 2 to 4 carbon atoms, and n represents the average number of moles of alkylene oxide added, which is between 9 and 35.

2. The ethanol-based pigment dispersion according to claim 1, wherein the pigment dispersant (B) is a polymer further comprising a structural unit derived from a hydrophobic monomer (b-3) having an alkyl group.

3. The ethanol-based pigment dispersion according to claim 2, wherein the content of constituent units derived from the hydrophobic monomer (b-3) in the total constituent units of the pigment dispersant (B) is 0.2% by mass or more and 15% by mass or less.

4. The ethanol-based pigment dispersion according to claim 2 or 3, wherein the alkyl group contained in the hydrophobic monomer (b-3) has 1 to 6 carbon atoms.

5. The ethanol-based pigment dispersion according to any one of claims 1 to 4, wherein the aluminum lake pigment (A) is one or more selected from Yellow No. 4 Aluminum Lake, Yellow No. 5 Aluminum Lake, Blue No. 1 Aluminum Lake, and Red No. 104-(1) Aluminum Lake.

6. The ethanol-based pigment dispersion according to any one of claims 1 to 5, wherein R 12 in formula (1) is an alkyl group having 1 to 8 carbon atoms.

7. An ethanol-based pigment dispersion according to any one of claims 1 to 6, wherein the mass ratio of the content of aluminum lake pigment (A) to the total content of the aluminum lake pigment (A) and the pigment dispersant (B) [aluminum lake pigment (A) / [aluminum lake pigment (A) + pigment dispersant (B)]] is 0.30 or more and 0.70 or less.

8. The ethanol-based pigment dispersion according to any one of claims 1 to 7, wherein the acid value of the pigment dispersant (B) is 25 mg KOH / g or more and 400 mg KOH / g or less.

9. The ethanol-based pigment dispersion according to any one of claims 1 to 8, wherein the degree of neutralization of the anionic groups of the pigment dispersant (B) is 3 mol% or more and 50 mol% or less.

10. An ethanol-based ink for inkjet recording, comprising an ethanol-based pigment dispersion according to any one of claims 1 to 9 and an ethanol-soluble organic solvent (C).

11. The ethanol-based ink for inkjet recording according to claim 10, further containing a silicone-based surfactant.

12. An ethanol-based ink for inkjet recording according to claim 10 or 11, used in inkjet recording where the ink ejection method is a thermal method.

13. An ethanol-based inkjet recording ink according to any one of claims 10 to 12, wherein the content of the aluminum lake pigment (A) in the ink is 2% by mass or more.

Images