Alcohol-based ink for inkjet recording

Abstract

To provide an alcohol-based ink for inkjet recording having excellent decapping properties while having excellent color development and hiding properties and to provide an inkjet recording method using the alcohol-based ink.SOLUTION: There are provided: an alcohol-based ink for inkjet recording which contains an aluminum lake pigment A, a pigment dispersant B, an alcohol C, a solvent D and a polymer E, wherein the pigment dispersant B is a polymer containing a constituent unit derived from an anionic group-containing monomer (b-1) and a constituent unit derived from a hydrophilic nonionic monomer (b-2), the alcohol C is one or more selected from the group consisting of ethanol, n-propanol and isopropanol, the solvent D has a boiling point of 150°C or more, a distance Ra of Hansen solubility parameter of the solvent D in water represented by the formula (I) is 40 or more, the solvent D is compatible with the alcohol C and the polymer E is soluble in the alcohol C and insoluble in the solvent D; and an inkjet recording method using the alcohol-based ink.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an alcohol-based ink for ink-jet recording. [Background technology]

[0002] Inkjet recording is a method of ejecting ink droplets from extremely fine nozzles directly onto a recording medium, depositing them on the recording medium to obtain printed matter on which characters and images are recorded. Unlike conventional recording methods, inkjet recording does not use plates, and is therefore expected to be used in a wide range of fields as on-demand printing that can handle small quantities of a wide variety of products. Recently, the application of inkjet recording to medicines and food has been considered.

[0003] For example, Patent Document 1 describes an edible pigment composition that contains at least a lake pigment, a pigment dispersant, and a dispersion stabilizer, and an edible aqueous ink composition for inkjet use that contains the pigment composition and that is edible, for the purpose of providing a pigment composition that can be applied to printing images with excellent color development on solid preparations such as pharmaceuticals and foods and that has excellent dispersion stability (storage stability) of the lake pigment, and an aqueous ink composition for inkjet use. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-127589 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, base makeup cosmetics such as foundations and concealers, which are primarily intended to adjust skin color, are required to have the ability to conceal blemishes, birthmarks, or pores on the skin, and to have high color development properties that enable the cosmetics to be colored in the original color of the colorant blended therein. Furthermore, point makeup cosmetics, such as eye shadow, blush, and nail enamel, which are applied to parts of the face or nails to locally apply color and emphasize the color, are used for the purposes of adding shading to impart a three-dimensional effect or of locally applying color to emphasize the color, and therefore are required to have the ability to conceal the original color of the skin or nails, as well as high color development that enables the cosmetics to be colored in the original color of the coloring agent blended therein. Furthermore, temporary hair dyes such as hair mascara are preferred because they cause less damage to hair and allow easy hair dyeing, and are used particularly for the purpose of imparting vivid colors to hair in order to improve fashionability. Since temporary hair dyes color hair by forming a colored coating film on the hair, they are required to have the ability to conceal the original color of the hair and to have high color development that allows the hair to be colored in the original color of the colorant blended in the temporary hair dye. Furthermore, when printing on recording media that already have a colored base, such as parts of the human body such as skin, nails, and hair, inorganic pigments with high hiding power, such as titanium oxide, zinc oxide, and iron oxide, are blended in order to conceal the base color, as compared to when printing on white paper. However, high density pigments such as titanium oxide have high hiding power but high specific gravity, and therefore sedimentation is unavoidable in liquids that require low viscosity, such as inkjet recording inks. If such sedimentation occurs in the nozzles of an inkjet head, the nozzles may become clogged. For this reason, there is a demand for the development of an inkjet recording ink that can form a printing coating film with excellent hiding power and color development without using inorganic pigments with high specific gravity. Furthermore, aluminum lake pigments, which have good color development and are also highly safe, are also known as pigments used in cosmetics. Aluminum lake pigments are pigments that have carboxyl groups and sulfonic acid groups and are formed by adsorbing food dyes that are originally soluble in ethanol onto the surface of aluminum hydroxide gel due to the coagulation action of polycationized aluminum hydroxide gel. Therefore, aluminum lake pigments are generally difficult to disperse in alcohol such as ethanol, and if an attempt is made to disperse them in alcohol, they will gel while absorbing the alcohol. Furthermore, even if the pigment can be temporarily dispersed using a pigment dispersant having an anionic functional group, the aluminum ions eluted from the aluminum lake pigment degenerate the electric double layer formed by the anionic functional group of the pigment dispersant, making it impossible to suppress aggregation caused by collisions of the pigment particles due to Brownian motion, resulting in an increase in the particle size of the pigment particles and causing sedimentation of the pigment particles. In the examples of Patent Document 1, sodium polyacrylate is used as a pigment dispersant and water is used as a dispersion medium. Although sodium polyacrylate is expected to be stably adsorbed to the surface of aluminum lake pigment because the carboxyl groups are oriented in aluminum hydroxide gel, which is a polycation, it was found that the pigment could not be finely divided to a particle size that allows the ink to be ejected in an inkjet recording method, and the dispersion stability of the aluminum lake pigment is insufficient. Furthermore, in the application of alcohol-based ink using aluminum lake pigment to an inkjet recording method, improvement of ejection performance is also required. In particular, as decap characteristics, ejection recovery property that allows the ejection performance before being left alone to be easily restored by a nozzle performance recovery operation (maintenance) such as wiping, and ejection durability that allows the ejection performance before being left alone to be expressed without causing non-ejection due to nozzle clogging when the ink nozzle surface is left without protection after printing and printing is started again are also required. An object of the present invention is to provide an alcohol-based ink for ink-jet recording which has excellent color development and hiding power as well as excellent decap characteristics, and an ink-jet recording method which uses the alcohol-based ink. [Means for solving the problem]

[0006] The present inventors have discovered that the above-mentioned problems can be solved by an alcohol ink for inkjet recording, which contains an aluminum lake pigment, a pigment dispersant containing a structural unit derived from a specific monomer, a specific alcohol, a solvent other than alcohol having a boiling point equal to or higher than a specific value and having a Hansen solubility parameter distance Ra in water, represented by a specific formula described below, equal to or higher than a specific value, and a polymer, wherein the solvent other than alcohol is compatible with the alcohol, and the polymer is soluble in the alcohol but insoluble in the solvent other than the alcohol. That is, the present invention relates to the following [1] and [2]. [1] An alcohol-based ink for ink-jet recording, comprising: an aluminum lake pigment A; a pigment dispersant B; an alcohol C; a solvent D; and a polymer E, 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, The alcohol C is at least one selected from the group consisting of ethanol, n-propanol, and isopropanol; The boiling point of the solvent D is 150° C. or higher, and the distance Ra of the Hansen solubility parameter of the solvent D in water represented by the following formula (I) is 40 or higher; An alcohol-based ink for ink-jet recording, wherein the solvent D is compatible with the alcohol C, and the polymer E is soluble in the alcohol C but insoluble in the solvent D. Ra = (4 × ΔD 2 +ΔP 2 +ΔH 2 ) 0.5 (I) ΔD: Difference in dispersion components in Hansen solubility parameters between solvent D and water ΔP: Difference in polar components in Hansen solubility parameters between solvent D and water ΔH: Difference in hydrogen bond components in the Hansen solubility parameters between solvent D and water [2] An inkjet recording method comprising ejecting the alcohol-based ink for inkjet recording according to [1] above onto a recording medium to form a printed coating film. Effect of the Invention

[0007] According to the present invention, it is possible to provide an alcohol-based ink for ink-jet recording which has excellent color development and hiding power as well as excellent decap characteristics, and an ink-jet recording method using the alcohol-based ink. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Alcohol-based ink for inkjet recording] The alcohol-based ink for ink-jet recording of the present invention (hereinafter, simply referred to as "the ink of the present invention" or "ink") is an alcohol-based ink for ink-jet recording, which contains an aluminum lake pigment A, a pigment dispersant B, an alcohol C, a solvent D, and a polymer E, in which the pigment dispersant B is a polymer containing a constitutional unit derived from an anionic group-containing monomer (b-1) and a constitutional unit derived from a hydrophilic nonionic monomer (b-2) containing an oxyalkylene group, the alcohol C is one or more selected from the group consisting of ethanol, n-propanol, and isopropanol, the boiling point of the solvent D is 150°C or higher, and the distance Ra of the Hansen solubility parameter of the solvent D in water represented by the following formula (I) is 40 or more, the solvent D is compatible with the alcohol C, and the polymer E is soluble in the alcohol C but insoluble in the solvent D. Ra = (4 × ΔD 2 +ΔP 2 +ΔH 2 ) 0.5 (I) ΔD: Difference in dispersion components in Hansen solubility parameters between solvent D and water ΔP: Difference in polar components in Hansen solubility parameters between solvent D and water ΔH: Difference in hydrogen bond components in the Hansen solubility parameters between solvent D and water

[0009] In the present invention, "alcohol-based" means that the content of alcohol C in the liquid medium, which is a constituent component of the ink of the present invention, accounts for the largest proportion by mass. In the present invention, "compatible" refers to a phenomenon in which alcohol C and solvent D dissolve in each other in a mixed system containing alcohol C and solvent D. Alcohol C and solvent D are considered to be in a compatible state when they are mixed and left to stand and do not separate into multiple phases, or when they are mixed and stirred and do not separate into phases to become cloudy. Polymer E is soluble in alcohol C and insoluble in solvent D, and is dissolved in the alcohol-based ink for ink-jet recording of the present invention. In the present invention, "polymer E is soluble in alcohol C" means that when polymer E, which has been dried at 105° C. for 2 hours and has reached a constant weight, is dissolved in 100 g of alcohol C at 25° C., the amount of polymer E dissolved in alcohol C is preferably 10 g or more from the viewpoint of improving color development and hiding power. In the present invention, "Polymer E is insoluble in solvent D" means that when polymer E, which has been dried at 105° C. for 2 hours and has reached a constant weight, is dissolved to saturation in 100 g of solvent D at 25° C., the amount of polymer E dissolved in solvent D is preferably less than 2 g, from the viewpoint of improving color development and hiding power. The above judgment of "compatible" or "soluble" is made at 25°C.

[0010] In the present invention, the "Hansen solubility parameter" is expressed by dividing the solubility parameter (SP value) introduced by Hildebrand into three components (dispersion component D, polar component P, and hydrogen bond component H). D, P, and H of each solvent are described in detail in "HANSEN SOLBILITY PARAMETERS" A User's Handbook Second Edition. In addition, HSP values ​​for many solvents and resins are also described in Industrial Solvents Handbook by Wesley L. Archer, etc. The D, P, and H of each solvent can also be determined using the software HSPiP from Charles Hansen Consulting, Inc. (Horsholm, Denmark, hansen-solubility.com). In the present invention, for solvents registered in the HSPiP version 4.1.03 database (see literature on various HSPs), the values ​​are used, and for solvents not in the database, the values ​​estimated by the above-mentioned HSPiP are used. In the present invention, the unit of the "Hansen solubility parameter" is "(MPa) 0.5 "

[0011] The ink of the present invention has the special effect of exhibiting excellent decap characteristics while having excellent color development and hiding power. The reason for this is not clear, but is thought to be as follows. The ink of the present invention contains, in addition to aluminum lake pigment A and pigment dispersant B, one or more alcohols C selected from the group consisting of ethanol, n-propanol, and isopropanol, solvent D having a boiling point of 150° C. or higher and a distance Ra of the Hansen solubility parameter in water represented by the above formula (I) of 40 or higher, and polymer E soluble in the alcohol C but insoluble in the solvent D. When such an ink is applied to a recording medium, the heat of vaporization is taken away by the evaporation of alcohol C in the coating film, the temperature of the coating film surface decreases, and moisture in the air condenses on the coating film surface and adheres to the coating film surface as fine water droplets. In the present invention, since alcohol C is one or more selected from a group consisting of specific alcohols and the distance Ra of the solubility parameter in water of solvent D is a specific value or higher, the adhesion of these fine water droplets to the coating film surface causes phase separation of solvent D, which was compatible with alcohol C. Since the polymer E is insoluble in the solvent D, the polymer E covers the phase-separated solvent D, and the coalescence of the solvent D is suppressed, so that primary particles having a core-shell structure with the solvent D as the core and the polymer E as the shell are formed. Furthermore, with the evaporation of the alcohol C and the alignment of the surfaces of the formed primary particles, a regularly separated cellular convection structure, so-called Benard Cells, is generated in the coating film, and it is considered that a printed coating film containing the aluminum lake pigment A in which the primary particles are accumulated to form secondary particles due to the Benard convection in each cell is obtained. As a result, it is presumed that the particle structure formed in the printed coating film scatters light, and high hiding power and color development are expressed. In addition, when the solvent D has a volatile property described later, the solvent D contained in the core part evaporates to form hollow primary particles, which can improve the hiding power, color development, and film-forming property of the printed coating film. Furthermore, in the ink of the present invention, the aluminum lake pigment A is dispersed in a polymer that contains, as a pigment dispersant B, a constituent unit derived from an anionic group-containing monomer (b-1) and a constituent unit derived from a hydrophilic nonionic monomer (b-2) having an oxyalkylene group. Here, the anionic group introduced into the pigment dispersant B by the constituent unit derived from the anionic group-containing monomer (b-1) is oriented and adsorbed on the surface of the aluminum hydroxide gel of the aluminum lake pigment A, and the electrical repulsive force of the anionic group suppresses the aggregation and precipitation of the pigment particles, which is believed to contribute to the reduction of the particle size of the pigment particles. The oxyalkylene group introduced into the pigment dispersant B by the constituent unit derived from the hydrophilic nonionic monomer (b-2) increases the affinity of the surface of the aluminum lake pigment A to the alcohol C contained as the liquid medium, and the surface of the aluminum lake pigment A is covered with an alcohol molecular layer, which generates a three-dimensional repulsive force that can prevent the contact between the pigment particles, and also prevents the aggregation of the pigment particles, which is believed to suppress the increase in the particle size of the pigment particles. As a result, the dispersed particle size of the pigment particles dispersed by the pigment dispersant B can be reduced, and when used in an ink for an inkjet recording method, the aggregation of the pigment particles in a narrow inkjet nozzle can be prevented, thereby suppressing the clogging of the nozzle, which is believed to improve the decap property.

[0012] <Aluminum Lake Pigment A> The ink of the present invention contains aluminum lake pigment A (hereinafter, simply referred to as "pigment"). Aluminum lake pigment A is composed 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 an aromatic ring in the molecule, and thus has high alcohol solubility. From the viewpoint of making the dye component having such a chemical structure into an alcohol-insoluble pigment, the aluminum lake pigment A is prepared by adding polymerized aluminum ions [Al n+2 (OH) 3n ] 6+ It is preferable that the dye component (α) is bonded to an aluminum hydroxide gel (β) carrier, the aluminum hydroxide gel (β) being present in the form of n=10 or more.

[0013] The aluminum lake pigment A is not particularly limited, but from the viewpoint of reducing the particle size of the dispersed pigment particles and improving color development, hiding power, and decap properties, it is preferably a pigment using at least one dye component (α) selected from the group consisting of Yellow No. 4, Yellow No. 5, Red No. 2, Red No. 3, Red No. 40, Red No. 102, Red No. 104-(1), Green No. 3, Blue No. 1, and Blue No. 2, and more preferably at least one dye component selected from the group consisting of Yellow No. 4 Aluminum Lake, Yellow No. 5 Aluminum Lake, Blue No. 1 Aluminum Lake, and Red No. 104-(1) Aluminum Lake.

[0014] <Pigment dispersant B> The ink of the present invention contains a pigment dispersant B (hereinafter, also simply referred to as "dispersant B"). Dispersant B has the function of stably dispersing aluminum lake pigment A in an alcohol-based medium. That is, the ink of the present invention is an alcohol-based ink for ink-jet recording, in which aluminum lake pigment A is dispersed in dispersant B, and which contains alcohol C, solvent D, and polymer E. Dispersant B is a polymer containing a constitutional unit derived from an anionic group-containing monomer (b-1) and a constitutional unit derived from a hydrophilic nonionic monomer containing an oxyalkylene group (hereinafter, also simply referred to as "hydrophilic nonionic monomer (b-2)"). Dispersant B is obtained by copolymerizing raw material monomers including the anionic group-containing monomer (b-1) and the hydrophilic nonionic monomer (b-2).

[0015] (Anionic Group-Containing Monomer (b-1)) Dispersant B contains a constituent unit derived from an anionic group-containing monomer (b-1). The anionic group introduced into the polymer as dispersant B by the anionic group-containing monomer (b-1) is oriented to the aluminum hydroxide gel (β) portion of aluminum lake pigment A, thereby allowing dispersant B to be adsorbed to aluminum lake pigment A. This is believed to reduce the particle size of the dispersed pigment particles, improve color development and hiding power, and further improve decap properties. The anionic group is not particularly limited, but examples thereof include a carboxy group, a sulfonic acid group, and a phosphate group. From the viewpoint of reducing the particle size of the dispersed pigment particles and improving color development, hiding properties, and decap properties, the carboxy group is preferred. Examples of the carboxy group-containing monomer 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, β-styrylacrylic acid (1-carboxy-4-phenylbutadiene-1,3), and 2-methacryloyloxymethylsuccinic acid; 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, from the viewpoints of reducing the particle size of the dispersed pigment particles and improving the color development, hiding properties, and decap properties, the anionic group-containing monomer (b-1) is preferably a carboxy group-containing monomer, more preferably a monocarboxylic acid monomer, and even more preferably (meth)acrylic acid, and from the viewpoints of improving the dispersibility of the pigment, reducing the particle size of the dispersed pigment particles, and improving the color development, hiding properties, and decap properties, it is even more preferable that it contains acrylic acid, and even more preferably is acrylic acid. 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 mass% or more, more preferably 40 mass% or more, even more preferably 50 mass% or more, still more preferably 70 mass% or more, even more preferably 90 mass% or more, and preferably 100 mass% or less. In this specification, "(meth)acrylic acid" means one or more selected from the group consisting of acrylic acid and methacrylic acid. The "(meth)acrylic acid" in the following description has the same meaning.

[0016] (Hydrophilic nonionic monomer containing an oxyalkylene group (b-2)) Dispersant B contains a structural unit derived from a hydrophilic nonionic monomer (b-2) containing an oxyalkylene group, from the viewpoint of reducing the particle size of dispersed pigment particles and improving color development, hiding properties, and decap properties. In the present invention, the term "hydrophilic" of a monomer means that when the monomer is dissolved in 100 g of ion-exchanged water at 25° C. until saturation, the amount of the monomer dissolved is 10 g or more.

[0017] 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 a carbon number of 2 or more and 4 or less. Specific examples include an oxyethylene group, an oxypropylene group, and an oxybutylene group, but from the viewpoint of reducing the particle size of dispersed pigment particles and improving color development, hiding properties, and decap properties, the oxyalkylene group is preferably at least one selected from the group consisting of 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 includes at least one selected from the group consisting of 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. Specific examples of the hydrophilic nonionic monomer (b-2) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; polyalkylene glycol (meth)acrylates; alkoxy polyalkylene glycol (meth)acrylates; and polyalkylene glycol monoallyl ethers. In this specification, "(meth)acrylate" means one or more selected from the group consisting of acrylate and methacrylate. The "(meth)acrylate" in the following description has the same meaning.

[0018] Among these, the hydrophilic nonionic monomer (b-2) is preferably one having a polyalkylene glycol chain, from the viewpoint of reducing the particle size of the dispersed pigment particles and improving the hiding power, color development, and decap properties. The average number of moles of alkylene oxide added to the polyalkylene glycol chain is, from the same viewpoint as above, preferably 2 or more, more preferably 4 or more, and even more preferably 9 or more, and, from the same viewpoint as above, preferably 120 or less, more preferably 90 or less, even more preferably 45 or less, and still more preferably 35 or less. When the average number of moles added is within the above range, the decap property can be further improved. The polyalkylene glycol chain may contain units derived from ethylene oxide and units derived from propylene oxide.

[0019] From the viewpoint of reducing the particle size of dispersed pigment particles and improving color development, hiding properties, and decap properties, the structural unit derived from the hydrophilic nonionic monomer (b-2) is preferably a structural unit derived from an alkoxy polyalkylene glycol (meth)acrylate or a structural unit derived from a polyalkylene glycol (meth)acrylate, and more preferably a structural unit derived from a (meth)acrylate having a polyalkylene glycol chain represented by the following formula (1).

[0020] [ka] (In the formula, 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 a number of 2 to 120.

[0021] In the formula (1), from the viewpoints of reducing the particle size of the dispersed pigment and improving hiding power, color development, and decap properties, the number of carbon atoms in OA, which is an oxyalkylene group, is preferably from 2 to 3, more preferably 2. That is, from the same viewpoints as above, OA, which is an oxyalkylene group, is preferably at least one selected from the group consisting of an oxyethylene group and an oxypropylene group, more preferably an oxyethylene group. In the formula (1), R 12 From the viewpoint of reducing the particle size of the dispersed pigment and improving hiding power, color development, and decap properties, 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 the above formula (1), 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 particle size of the dispersed pigment and improving the hiding power, color development, and decap properties, and from the same viewpoint as above, it is preferably a number of 90 or less, more preferably 45 or less, and even more preferably 35 or less. However, the n oxyalkylene groups may be the same or different from each other. When the oxyalkylene groups are different from each other, they may be added in any of block addition, random addition, and alternating addition.

[0022] The polyalkylene glycol (meth)acrylate constituting the structural unit represented by the formula (1) is preferably one or more selected from the group consisting of polyethylene glycol mono(meth)acrylate, polyethylene glycol / polypropylene glycol (meth)acrylate, alkoxypolyethylene glycol (meth)acrylate, and alkoxy(polyethylene glycol / polypropylene glycol)(meth)acrylate, more preferably one or more selected from the group consisting of polyethylene glycol mono(meth)acrylate and alkoxypolyethylene glycol (meth)acrylate. The alkoxypolyethylene glycol (meth)acrylate is preferably one or more selected from the group consisting of methoxypolyethylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, propoxypolyethylene glycol mono(meth)acrylate, butoxypolyethylene glycol mono(meth)acrylate, octoxypolyethylene glycol mono(meth)acrylate, and stearoxypolyethylene glycol mono(meth)acrylate, more preferably one or more selected from the group consisting of methoxypolyethylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, and propoxypolyethylene glycol mono(meth)acrylate, and even more preferably methoxypolyethylene glycol mono(meth)acrylate.

[0023] As described above, the hydrophilic nonionic monomer (b-2) is preferably an alkoxypolyethylene glycol mono(meth)acrylate, more preferably one or more selected from the group consisting of methoxypolyethylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, and propoxypolyethylene glycol mono(meth)acrylate, and even more preferably methoxypolyethylene glycol mono(meth)acrylate.

[0024] 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 Co., Ltd.); Blenmar PME-1000, PME-4000, and 50POEP-800B (all manufactured by NOF Corporation); and Light Ester 041MA (manufactured by Kyoeisha Chemical Co., Ltd.).

[0025] (Hydrophobic Monomer Having an Alkyl Group (b-3)) Dispersant B may be a polymer further containing, in addition to the constituent units derived from the anionic group-containing monomer (b-1) and the constituent units derived from the hydrophilic nonionic monomer (b-2), a constituent unit derived from a hydrophobic monomer (b-3) having an alkyl group (hereinafter also simply referred to as "hydrophobic monomer (b-3)"). In the present invention, the term "hydrophobic monomer" refers to a monomer that, when dissolved in 100 g of ion-exchanged water at 25° C. until saturated, dissolves in an amount of less than 10 g. By dispersant B having an alkyl group introduced by hydrophobic monomer (b-3), the alkyl groups gather together on the ink nozzle surface as alcohol C contained as a liquid medium volatilizes, and dispersant B forms a polymer film, suppressing excessive volatilization of alcohol C and preventing the ink from drying on the ink nozzle surface. In addition, when new ink is supplied to the inkjet head for maintenance, the affinity of the alkyl group portion introduced into dispersant B to the alkyl group of alcohol C causes the alcohol C contained in the newly supplied ink to dissolve the portion (core) where the alkyl groups contained in the polymer film of dispersant B formed on the ink nozzle surface gather together, making the polymer film more likely to break and facilitating recovery of a good ejection state. As a result, it is considered that the ejection properties of the ink are improved and the decap characteristics can be further improved. In this way, since dispersant B has an alkyl group introduced by hydrophobic monomer (b-3), it is possible to form a polymer film that has the property of suppressing excessive volatilization of ethanol alcohol C during ink drying and the property of being easily torn during maintenance due to the affinity of the alkyl group portion for ethanol alcohol C, which is thought to further improve the ink ejection properties and decap characteristics.

[0026] The hydrophobic monomer (b-3) has an alkyl group and a polymerizable group in the molecule. The number of carbon atoms in the alkyl group contained in the hydrophobic monomer (b-3) is preferably 1 or more, and preferably 22 or less, more preferably 18 or less, even more preferably 16 or less, still more preferably 12 or less, still more preferably 10 or less, still more preferably 8 or less, still more preferably 6 or less, and still more preferably 4 or less. When 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 due to maintenance, dissolution of the polymer film of dispersant B on the ink nozzle surface is promoted, making it easier to remove the polymer film with fewer maintenance sessions, and improving decap properties. The alkyl group of the hydrophobic monomer (b-3) may be a straight-chain, branched-chain, or alicyclic alkyl group. Specific examples of the straight-chain or branched-chain alkyl group include a methyl group, an ethyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Examples of the alicyclic alkyl group include a cyclohexyl group. Among these, from the viewpoints of suppressing drying of the ink on the ink nozzle surface, facilitating removal of the polymer film with fewer maintenance sessions, and further improving the decap properties, the alkyl group of the hydrophobic monomer (b-3) is preferably a straight-chain or branched-chain alkyl group, more preferably one or more selected from the group consisting of 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, even more preferably one or more selected from the group consisting of 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 the group consisting of a methyl group, an ethyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group, and even more preferably one or more selected from the group consisting of a methyl group, an ethyl group, and an isobutyl group. The polymerizable group is a group having a radically polymerizable unsaturated double bond, and may be one or more selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. Among them, the vinyl group, the allyl group, the acryloyl group, or the methacryloyl group is preferable, the acryloyl group or the methacryloyl group is more preferable, and the methacryloyl group is even more preferable.

[0027] From the viewpoints of suppressing drying of the ink on the ink nozzle surface, facilitating removal of the polymer film with fewer maintenance sessions, and further improving decap properties, the structural unit derived from the hydrophobic monomer (b-3) is preferably a structural unit derived from an alkyl (meth)acrylate ester having an alkyl group derived from an aliphatic alcohol, as represented by the following formula (2):

[0028] [ka] (In the formula, R 21 represents a hydrogen atom or a methyl group, R 22 represents an alkyl group having 1 to 22 carbon atoms.

[0029] In the formula (2), R 22 The number of carbon atoms in is preferably 1 or more from the viewpoints of suppressing drying of the ink on the ink nozzle surface, facilitating removal of the polymer film with fewer maintenance sessions, and further improving decapability, and from the same viewpoints as above, is preferably 22 or less, more preferably 18 or less, even more preferably 16 or less, still more preferably 12 or less, still more preferably 10 or less, still more preferably 8 or less, still more preferably 6 or less, and still more preferably 4 or less. R is an alkyl group 22 is an alkyl group derived from a linear, branched, or alicyclic aliphatic alcohol. 22From the same viewpoint as above, is preferably a straight-chain or branched-chain alkyl group, more preferably one or more selected from the group consisting of 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, even more preferably one or more selected from the group consisting of 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 the group consisting of a methyl group, an ethyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group, and even more preferably one or more selected from the group consisting of a methyl group, an ethyl group, and an isobutyl group.

[0030] The hydrophobic monomer (b-3) is preferably a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 10 carbon atoms, more preferably a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 6 carbon atoms, still more preferably one or more selected from the group consisting of 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 still more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl acrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, tert-butyl acrylate, and n-hexyl acrylate. More preferably, the acrylates include one or more (meth)acrylic acid alkyl esters having an alkyl group having 1 to 4 carbon atoms selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl acrylate, ethyl acrylate, and n-butyl acrylate, even more preferably one or more (meth)acrylic acid alkyl esters having an alkyl group having 1 to 4 carbon atoms selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl acrylate, ethyl acrylate, and n-butyl acrylate, even more preferably one or more selected from the group consisting of methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, methyl acrylate, and ethyl acrylate, even more preferably one or more selected from the group consisting of methyl methacrylate, ethyl methacrylate, and isobutyl methacrylate, and even more preferably one or more selected from the group consisting of methyl methacrylate and isobutyl methacrylate.

[0031] The content of the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms in the hydrophobic monomer (b-3) is, from the viewpoints of suppressing drying of the ink on the nozzle surface, facilitating removal of the polymer film with fewer maintenance sessions, and improving decap properties, preferably 70 mass % or more, more preferably 80 mass % or more, even more preferably 90 mass % or more, still more preferably 95 mass % or more, and preferably 100 mass % or less. From the viewpoints of suppressing drying of the ink on the nozzle surface, facilitating removal of the polymer film with fewer maintenance sessions, and further improving the decap 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, still more preferably 70% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass or less.

[0032] 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), Light Ester TB (tert-butyl methacrylate) (all manufactured by Kyoeisha Chemical Co., Ltd.), and the like.

[0033] Dispersant B may have a constitutional unit derived from an anionic group-containing monomer (b-1), a constitutional unit derived from a hydrophilic nonionic monomer (b-2), and a constitutional unit derived from a monomer other than the hydrophobic monomer (b-3) within a range that does not impair the effects of the present invention. Examples of the other monomer include a hydrophilic nonionic monomer other than the hydrophilic nonionic monomer (b-2) and a hydrophobic monomer other than the hydrophobic monomer (b-3).

[0034] Examples of the hydrophilic nonionic monomer other than the hydrophilic nonionic monomer (b-2) include (meth)acrylamide; N-vinyl-2-pyrrolidone; and N-alkyl(meth)acrylamide. Examples of hydrophobic monomers other than the hydrophobic monomer (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 a substituent containing a hetero atom, and more preferably at least one selected from the group consisting of a styrene-based monomer and an aromatic group-containing (meth)acrylate. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of the styrene monomer include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. Examples of the aromatic group-containing (meth)acrylate include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0035] The content of the structural units derived from the anionic group-containing monomer (b-1) in all the structural units of dispersant B is, from the viewpoints of reducing the particle size of the dispersed pigment particles and improving the color development, hiding properties, and decap properties, preferably 3 mass % or more, more preferably 7 mass % or more, even more preferably 10 mass % or more, and still more preferably 13 mass % or more, and from the same viewpoints as above, is preferably 55 mass % or less, more preferably 45 mass % or less, even more preferably 35 mass % or less, still more preferably 25 mass % or less, and still more preferably 20 mass % or less. The content of the structural units derived from the hydrophilic nonionic monomer (b-2) in all the structural units of dispersant B is, from the viewpoints of reducing the particle size of the dispersed pigment particles and improving the color development, hiding properties, and decap properties, 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, and from the same viewpoints as above, is preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 87% by mass or less. When dispersant B contains a constituent unit derived from hydrophobic monomer (b-3), the content of the constituent unit derived from hydrophobic monomer (b-3) in all constituent units of dispersant B is, from the viewpoints of suppressing drying of the ink on the ink nozzle surface, facilitating removal of the polymer film with fewer maintenance sessions, and further improving the decap properties, preferably 1 mass % or more, more preferably 5 mass % or more, and even more preferably 7 mass % or more, and from the same viewpoints as above, preferably 15 mass % or less, more preferably 12 mass % or less, and even more preferably 10 mass % or less.

[0036] When dispersant B contains a structural unit derived from a hydrophilic nonionic monomer other than the hydrophilic nonionic monomer (b-2), the content of the structural unit derived from a hydrophilic nonionic monomer other than the hydrophilic nonionic monomer (b-2) is, from the viewpoints of improving the adsorption of the dispersant to the pigment in an ethanol-based medium, reducing the particle size of the dispersed pigment particles, and improving the color development, hiding properties, and decap properties, preferably 10 mass % or less, more preferably 7 mass % or less, even more preferably 5 mass % or less, still more preferably 3 mass % or less, and even more preferably 2 mass % or less.

[0037] When dispersant B contains a structural unit derived from a hydrophobic monomer other than the hydrophobic monomer (b-3), the content of the structural unit derived from a hydrophobic monomer other than the hydrophobic monomer (b-3) is, from the viewpoints of improving the adsorption of the dispersant to the pigment in an ethanol medium, reducing the particle size of the dispersed pigment particles, and improving the color development, hiding properties, and decap properties, preferably 10 mass % or less, more preferably 7 mass % or less, even more preferably 5 mass % or less, still more preferably 3 mass % or less, and even more preferably 2 mass % or less.

[0038] As described above, dispersant B may have other structural units than the structural units derived from the anionic group-containing monomer (b-1), the structural units derived from the hydrophilic nonionic monomer (b-2), and the structural units derived from the hydrophobic monomer (b-3), within a range that does not impair the effects of the present invention. However, from the viewpoint of reducing the particle size of the dispersed pigment particles and improving the color development, hiding properties, and decap properties, the total content of the structural units derived from the anionic group-containing monomer (b-1), the structural units derived from the hydrophilic nonionic monomer (b-2), and the structural units derived from 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, still more preferably 95% by mass or more, still more preferably 97% by mass or more, still more preferably 99% by mass or more, and preferably 100% by mass or less.

[0039] From the viewpoint of reducing the particle size of the dispersed pigment particles and improving color development, hiding power, and decap properties, the dispersant B is preferably a polymer containing a constitutional unit derived from (meth)acrylic acid as the anionic group-containing monomer (b-1) and a constitutional unit derived from alkoxypolyethylene glycol (meth)acrylate as the hydrophilic nonionic monomer (b-2), and more preferably contains a constitutional unit derived from (meth)acrylic acid as the anionic group-containing monomer (b-1) and a constitutional unit derived from methoxypolyethylene glycol (meth)acrylate as the hydrophilic nonionic monomer (b-2). In addition, 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 decap properties, the dispersant B may further contain a constitutional unit derived from a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 10 carbon atoms as a hydrophobic monomer (b-3). As the hydrophobic monomer (b-3), a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 6 carbon atoms is preferably mentioned.

[0040] It is believed that the decap property can be further improved. The formation of a polymer film that exhibits such an effect is believed to depend on the type and number of alkyl groups introduced into dispersant B. From this viewpoint, when dispersant B contains a constitutional unit derived from an anionic group-containing monomer (b-1), a constitutional unit derived from a hydrophilic nonionic monomer (b-2), and a constitutional unit derived from a hydrophobic monomer (b-3), as an index of the type and number of alkyl groups introduced into dispersant B, the molar concentration of the alkyl ester group of 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 35 mol% or less, more preferably 30 mol% or less, and even more preferably 27 mol% or less, based on the total constitutional units of dispersant B being 100 mol%. The molar concentration of the alkyl ester group in dispersant B can be calculated from the monomer composition of dispersant B and the molecular weight of each monomer.

[0041] The dispersant B may be one synthesized by a known polymerization method, or a commercially available product. The method for obtaining Dispersant B is preferably a solution polymerization method from the viewpoint of controlling the molecular weight. The solvent used in the solution polymerization method is not particularly limited, and preferred examples thereof include 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. From the viewpoints of having a boiling point equal to or higher than the polymerization temperature and of ease of removal after polymerization, isopropanol is preferred. In the polymerization, a polymerization initiator and a chain transfer agent can be used. The polymerization initiator can be any one that is used in normal solution polymerization. For example, dilauroyl peroxide, pivaloyl tert-butyl peroxide, tert-butyl peroxyneodecanoate, and other organic peroxides; 2,2'-azobis(2,4-dimethylvaleronitrile), and other azo compounds can be mentioned. Among these, dilauroyl peroxide is preferred. The amount of the polymerization initiator used is, relative to 100 parts by mass of the total amount of the raw material monomers of Dispersant B, 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, from the viewpoint of the molecular weight distribution of Dispersant B, and is 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 necessary. When a chain transfer agent is used, the chain transfer agent is preferably isopropanol or a thiol compound. When isopropanol is used as the chain transfer agent, it can also be used as the solvent in the solution polymerization. The chain transfer agent is preferably isopropanol from the viewpoint of controlling the molecular weight and from the viewpoint of using it as a solvent as well. When a thiol compound is used as a chain transfer agent, the amount of the thiol compound used is, relative to 100 parts by mass of the total amount of raw material monomers of Dispersant B, 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, from the viewpoint of the molecular weight distribution of Dispersant B, and is 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. When isopropanol is used as both a chain transfer agent and a solvent, the amount of isopropanol used is, relative to 100 parts by mass of the total amount of raw material monomers of Dispersant B, 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, from the viewpoint of the molecular weight distribution of Dispersant B, and from the same viewpoint as above, is 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.

[0042] Although preferable polymerization conditions vary depending on the type of polymerization initiator, the polymerization temperature is preferably 50° C. or higher and 90° C. or lower, and the polymerization time is preferably 1 hour or higher and 20 hours or lower. When an organic peroxide is used as the polymerization initiator, the polymerization temperature is preferably 60° C. or higher, more preferably 65° C. or higher, from the viewpoint of reactivity, and is preferably 85° C. or lower, more preferably 83° C. or lower, from the viewpoint of the molecular weight distribution of dispersant B. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon. After the polymerization reaction is completed, the produced dispersant B can be isolated from the reaction solution by a known method such as reprecipitation, solvent distillation, etc. In addition, unreacted monomers and the like can be removed from dispersant B by reprecipitation, membrane separation, chromatography, extraction, etc. From the viewpoint of improving the productivity of the aluminum lake pigment dispersion, Dispersant B may be used as a solution of Dispersant B without removing the solvent used in the polymerization reaction.

[0043] The acid value of dispersant B is preferably 25 mgKOH / g or more, more preferably 30 mgKOH / g or more, even more preferably 50 mgKOH / g or more, and even more preferably 100 mgKOH / g or more, from the viewpoint of reducing the particle size of the dispersed pigment particles and improving color development, hiding power, and decap properties, and from the same viewpoint as above, is preferably 400 mgKOH / g or less, more preferably 350 mgKOH / g or less, even more preferably 300 mgKOH / g or less, even more preferably 250 mgKOH / g or less, even more preferably 200 mgKOH / g or less, even more preferably 150 mgKOH / g or less, and even more preferably 130 mgKOH / g or less. The acid value can be measured by the method described in the Examples.

[0044] The polystyrene-equivalent weight average molecular weight of dispersant B 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 the dispersion stability of the pigment and improving color development, hiding power, and decap properties, and is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 250,000 or less, still more preferably 200,000 or less, still more preferably 150,000 or less, and even more preferably 100,000 or less, from the viewpoint of reducing the particle size of the dispersed pigment particles. The weight average molecular weight can be measured by the method described in the Examples.

[0045] Dispersant B may be ionized by neutralizing at least a part of the anionic group. This allows random electrical repulsion to be imparted to dispersant B, and the anionic group of dispersant B is solvated with alcohol C in an alcohol-based medium, suppressing the formation of hydrogen bonds within the molecule, and the polymer chain of dispersant B is in a sufficiently expanded state without shrinking in the alcohol-based medium, so that the anionic group of dispersant B can more efficiently form ionic bonds with the aluminum of aluminum lake pigment A, and it is believed that the dispersed pigment particles can be made smaller in particle size, and color development, hiding power, and decap properties can be further improved. From this viewpoint, the degree of neutralization of dispersant B is preferably 0 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, still 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, still more preferably 40 mol% or less, still more preferably 37 mol% or less, still more preferably 27 mol% or less, still more preferably 22 mol% or less, and still more preferably 17 mol% or less.

[0046] Examples of the neutralizing agent 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, from the viewpoint of reducing the particle size of the dispersed pigment particles and further improving color development, hiding power, and decap properties, alkali metal hydroxides are preferred, and sodium hydroxide is more preferred. These neutralizing agents can be used alone or in combination of two or more. The neutralizing agent may be used as a solution of the neutralizing agent in alcohol C or as an aqueous solution of the neutralizing agent, preferably an aqueous solution of the neutralizing agent is used.

[0047] <Alcohol C> The ink of the present invention contains, as the alcohol C, one or more selected from the group consisting of ethanol, n-propanol, and isopropanol. In the ink of the present invention, alcohol C is compatible with solvent D and dissolves polymer E. As a result, when the ink of the present invention is applied to a recording medium, the alcohol C evaporates, and the heat of vaporization is taken away, the temperature of the coating film surface decreases, and minute water droplets adhere to the coating film surface, causing phase separation between alcohol C and solvent D. Primary particles having a core-shell structure with solvent D as the core and polymer E as the shell are formed, thereby improving hiding power and color development. The alcohol C may be used alone or in combination of two or more kinds. From the viewpoint of improving color development and hiding power, the alcohol C is preferably at least one selected from the group consisting of ethanol and isopropanol, more preferably ethanol, and from the viewpoint of improving decap properties, the alcohol C is preferably n-propanol.

[0048] <Solvent D> The ink of the present invention contains, as solvent D, a solvent having a boiling point of 150° C. or higher and a Hansen solubility parameter distance Ra of said solvent D in water, represented by the following formula (I), of 40 or higher. Ra = (4 × ΔD 2 +ΔP 2 +ΔH 2 ) 0.5 (I) ΔD: Difference in dispersion components in Hansen solubility parameters between solvent D and water ΔP: Difference in polar components in Hansen solubility parameters between solvent D and water ΔH: Difference in hydrogen bond components in the Hansen solubility parameters between solvent D and water In the ink of the present invention, solvent D is compatible with alcohol C but does not dissolve polymer E. As a result, when minute water droplets are deposited on the surface of the coating film due to the evaporation of alcohol C, phase separation occurs between alcohol C and solvent D, and primary particles having a core-shell structure in which solvent D is the core and polymer E is the shell are formed, thereby improving hiding power and color development. Solvent D may be used alone or in combination of two or more kinds.

[0049] The boiling point of solvent D is, from the viewpoint of forming primary particles and improving hiding power, color development, and decap properties, 150°C or higher, preferably 155°C or higher, more preferably 160°C or higher, even more preferably 165°C or higher, and even more preferably 170°C or higher, and from the viewpoint of handleability, is preferably 300°C or lower, more preferably 270°C or lower, even more preferably 250°C or lower, even more preferably 230°C or lower, even more preferably 210°C or lower, and even more preferably 180°C or lower. When two or more kinds of solvents D are used in combination, the boiling point of solvent D can be determined as a weighted average value weighted by the mass ratio of each component constituting solvent D to solvent D. When two or more types of solvent D are used in combination, the boiling point of each of the solvents constituting solvent D is preferably 150°C or higher, more preferably 155°C or higher, even more preferably 160°C or higher, still more preferably 165°C or higher, and even more preferably 170°C or higher, and from the viewpoint of handleability, is preferably 300°C or lower, more preferably 270°C or lower, even more preferably 250°C or lower, still more preferably 230°C or lower, still more preferably 210°C or lower, and even more preferably 180°C or lower. The ink of the present invention may contain a solvent D having a boiling point of 200°C or higher; from the viewpoint of handleability, the content of the solvent D having a boiling point of 200°C or higher is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, still more preferably 0.1% by mass or less, still more preferably substantially 0% by mass, and even more preferably 0% by mass.

[0050] The distance Ra of the Hansen solubility parameter of the solvent D in water is 40 or more, preferably 42 or more, more preferably 44 or more, and is preferably 60 or less, more preferably 57 or less, even more preferably 55 or less, still more preferably 50 or less, and even more preferably 47 or less, from the viewpoint of forming primary particles and improving color development and hiding power. When two or more types of solvent D are used in combination, the distance Ra of the Hansen solubility parameters in water can be determined as a weighted average value weighted by the content (mass%) of each solvent.

[0051] From the viewpoint of improving color development and hiding power, it is preferable that solvent D contains at least one oil selected from the group consisting of hydrocarbon oils and silicone oils. Examples of the hydrocarbon oil include at least one selected from the group consisting of α-olefin oligomers, liquid paraffin, liquid isoparaffins such as isododecane, isohexadecane, and hydrogenated polyisobutene (light liquid isoparaffin, heavy liquid isoparaffin), liquid ozokerite, squalane, pristane, and squalene. Among these, the hydrocarbon oil is more preferably at least one selected from the group consisting of α-olefin oligomers, liquid paraffin, liquid isoparaffin, liquid ozokerite, squalane, pristane, and squalene, more preferably liquid isoparaffin, even more preferably at least one selected from the group consisting of isododecane, isohexadecane, and hydrogenated polyisobutene, even more preferably at least one selected from the group consisting of isododecane and hydrogenated polyisobutene, and even more preferably hydrogenated polyisobutene. The weight average molecular weight of the hydrocarbon oil is preferably 150 or more, more preferably 160 or more, and preferably 1,000 or less, more preferably 500 or less, and even more preferably 300 or less. The viscosity of the hydrogenated polyisobutene at 20°C is preferably 0.5 mPa·s or more, more preferably 0.7 mPa·s or more, even more preferably 1 mPa·s or more, and preferably 30 mPa·s or less, more preferably 25 mPa·s or less, even more preferably 20 mPa·s or less, even more preferably 15 mPa·s or less, even more preferably 10 mPa·s or less, even more preferably 5 mPa·s or less, even more preferably 3 mPa·s or less, and even more preferably 2 mPa·s or less. The viscosity of the hydrogenated polyisobutene at 20°C can be measured using an E-type viscometer by the method described in the Examples.

[0052] Examples of silicone oils include linear silicone oils such as trisiloxane, branched silicone oils such as methyltrimethicone, and cyclic silicone oils such as methylcyclopolysiloxane. Among these, the silicone oil is preferably at least one selected from the group consisting of linear silicone oils, branched silicone oils, and cyclic silicone oils, more preferably at least one selected from the group consisting of trisiloxane, methyltrimethicone, and methylcyclopolysiloxane, and even more preferably at least one selected from the group consisting of trisiloxane and methyltrimethicone. The weight average molecular weight of the silicone oil is preferably 150 or more, more preferably 160 or more, and is preferably 1,000 or less, more preferably 500 or less, and even more preferably 300 or less. The viscosity of the silicone oil at 25° C. is preferably 0.5 mPa·s or more, and preferably 20 mPa·s or less, more preferably 10 mPa·s or less, even more preferably 5 mPa·s or less, still more preferably 3 mPa·s or less, and even more preferably 2 mPa·s or less. The viscosity of the silicone oil at 25° C. can be measured using an E-type viscometer in the manner described in the examples, by changing only the measurement temperature.

[0053] From the viewpoint of improving the film-forming properties and improving the color development and hiding properties of the resulting printed coating film, solvent D is preferably volatile, and more preferably is one or more selected from the group consisting of volatile hydrocarbon oils and volatile silicone oils. In the present invention, "volatile" means that the amount of evaporation at 25°C for 6 hours is 20% or more, as measured by the following method. Measurement method: Place a 90mm diameter filter paper in a 120mm diameter glass petri dish, place 1g of sample on the filter paper, and store in a room at 65% RH (25℃) for 6 hours. Measure the mass of the sample before and after storage, and calculate the amount of evaporation using the following formula. Evaporation amount (%) = [(sample mass before storage - sample mass after storage) / sample mass before storage] x 100

[0054] In the present invention, as described above, primary particles having a core-shell structure are formed, with solvent D as the core and polymer E as the shell. Since solvent D is volatile, the solvent D contained in the core evaporates to form hollow primary particles, thereby improving the hiding power, color development, and film-formability of the printed coating film. In addition, when the hollow primary particles are formed, minute holes (openings) may be formed in the shell. In this case, for example, when the ink of the present invention is applied to the skin, even if the skin grooves and wrinkles of the skin are deformed due to changes in facial expression, the hollow primary particles taken into the skin grooves and wrinkles can reversibly return to their original state by deforming the particles or pushing out air, following the volume change of the skin grooves and wrinkles. Therefore, it is considered that the extrusion of the hollow primary particles to the skin surface is suppressed, and the state of the cosmetic coating film before the deformation of the skin grooves and wrinkles can be well maintained, thereby improving the cosmetic retention. The hollow primary particles are preferably formed by evaporating the solvent D encapsulated in the core by adjusting the type of solvent D and the drying conditions of the coating film after application to the skin.

[0055] As the volatile hydrocarbon oil, from the viewpoint of improving color development and hiding power, and the film-forming properties of the printed coating film, a saturated or unsaturated hydrocarbon oil having 8 to 16 carbon atoms is preferred. Examples of the volatile hydrocarbon oil include paraffinic hydrocarbon oils such as n-decane, n-undecane, and n-dodecane; isoparaffinic hydrocarbon oils such as isodecane, isododecane, and hydrogenated polyisobutene (light liquid isoparaffin); and cyclic paraffin hydrocarbon oils such as cyclodecane and cyclododecane. Among these, the volatile hydrocarbon oil is preferably liquid isoparaffin, more preferably one or more selected from the group consisting of isodecane, isododecane, and hydrogenated polyisobutene, even more preferably one or more selected from the group consisting of isododecane and hydrogenated polyisobutene, and even more preferably hydrogenated polyisobutene. Examples of commercially available volatile hydrocarbon oils include "Pearlream 3" and "Pearlream 4" manufactured by NOF Corp.; and Marukasol R manufactured by Maruzen Petrochemical Co., Ltd.

[0056] As the volatile silicone oil, from the viewpoint of improving color development and hiding properties, as well as the film-forming properties of the printed coating film, preferably, one or more types selected from the group consisting of linear organopolysiloxanes and cyclic organopolysiloxanes are used. Specific examples of linear organopolysiloxanes include octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, and 1,1,1,3,5,5,5-heptamethyl-3-[(trimethylsilyl)oxy]-trisiloxane. Examples of the cyclic organopolysiloxane include 4- to 6-membered cyclic siloxanes having as a substituent an alkyl group having a carbon number of 1 to 5. Specific examples of the cyclic organopolysiloxane include octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. Commercially available volatile silicone oils include Shin-Etsu Chemical Co., Ltd.'s "KF-96A-1cs" (octamethyltrisiloxane), "KF-96L-1.5cs" (decamethyltetrasiloxane), "KF-96L-2cs" (dodecamethylpentasiloxane), "KF-995" (decamethylcyclopentasiloxane), and "TMF-1.5" (1,1,1,3,5,5,5-heptamethyl-3-[(trimethylsilyl)oxy]-trisiloxane); and Dow-Toray Co., Ltd.'s "DOWSIL SH200C Fluid 1cs" (octamethyltrisiloxane), "DOWSIL SH200C Fluid 1.5cs" (decamethyltetrasiloxane), "SH200C Fluid 2cs" (dodecamethylpentasiloxane), and "DOWSIL SH245 Fluid" (decamethylcyclopentasiloxane); Momentive Performance Materials' "TSF405A" (decamethylcyclopentasiloxane), etc.

[0057] Solvent D may contain, in addition to the hydrocarbon oil or silicone oil, a solvent used as a moisturizer, an ultraviolet absorber, an insect repellent, an anti-wrinkle agent, a fragrance, or the like. When solvent D contains at least one oil selected from the group consisting of hydrocarbon oils and silicone oils having a weight-average molecular weight of 150 or more and 1,000 or less, the total content of the hydrocarbon oils and silicone oils having a weight-average molecular weight of 150 or more and 1,000 or less in solvent D is, from the viewpoint of improving color development and hiding properties, preferably 50 mass % or more, more preferably 70 mass % or more, even more preferably 90 mass % or more, and preferably 100 mass % or less, and even more preferably 100 mass %.

[0058] <Polymer E> In the present invention, the polymer E coats the phase-separated solvent D and contributes to the formation of primary particles. There are no particular limitations on the polymer E, so long as it is soluble in the alcohol C and insoluble in the solvent D. Preferred examples of the polymer E include ionic polymers such as anionic polymers, cationic polymers, and betaine polymers. The polymer E can be used alone or in combination of two or more kinds.

[0059] (anionic polymer) An anionic polymer is a polymer that has an anionic group and exhibits anionic properties as a whole. The anionic group refers to an anionic group or a group that can be ionized to become an anionic group. Examples of the anionic group include a carboxy group (-COOM), a sulfonic acid group (-SO3M), and a phosphoric acid group (-OPO3M2). In the above chemical formula, M represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium.

[0060] [Anionic polymer EI] From the viewpoint of improving color development and hiding power, the anionic polymer is preferably an anionic polymer EI containing a structural unit derived from a monomer having an acidic group (hereinafter, also referred to as "anionic polymer EI"). From the same viewpoint as above, the monomer having an acidic group is preferably a carboxyl group-containing monomer. Preferred examples of the carboxyl group-containing monomer include the monomers exemplified in the above-mentioned dispersant B. Among them, the monomer having an acidic group is more preferably one or more selected from the group consisting of (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethylsuccinic acid, and further preferably (meth)acrylic acid.

[0061] From the viewpoint of improving color development and hiding power, the anionic polymer EI is preferably a copolymer further containing a structural unit derived from a monomer other than the monomer having an acidic group. Examples of the other monomer include hydrophobic monomers such as (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol and aromatic group-containing monomers; nonionic monomers.

[0062] The (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a carbon number of 1 to 22, more preferably 1 to 12, and even more preferably 1 to 8. Examples of the (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol include (meth)acrylates having a straight-chain alkyl group, (meth)acrylates having a branched-chain alkyl group, and (meth)acrylates having an alicyclic alkyl group. Preferred examples of the aromatic group-containing monomer include the monomers exemplified for the dispersant B described above.

[0063] Examples of nonionic monomers in the anionic polymer EI include (meth)acrylamide; N-vinyl-2-pyrrolidone; N-alkyl(meth)acrylamides having a linear, branched or cyclic alkyl group, such as N-tert-butylacrylamide, N-tert-octylacrylamide, N-(2-ethylhexyl)acrylamide, Nn-octylacrylamide, N-dodecylacrylamide, Nn-heptylacrylamide, N-hexylacrylamide, and N-cyclohexylmethacrylamide; Examples include hydroxyalkyl (meth)acrylates; polyalkylene glycol (meth)acrylates (m = 2 to 30, n represents the average number of moles of the oxyalkylene group added; the same applies below); alkoxypolyalkylene glycol (meth)acrylates (m = 1 to 30); and phenoxypolyalkylene glycol (meth)acrylates such as phenoxy (ethylene glycol-propylene glycol copolymer) (m = 1 to 30, ethylene glycol: m = 1 to 29) (meth)acrylate. Specific examples of commercially available nonionic monomers include NK Ester M-20G, M-40G, M-90G, M-230G, and the like, manufactured by Shin-Nakamura Chemical Co., Ltd.; Blemmer PE-90, 200, 350, and the like, Blemmer PME-100, 200, 400, and the like, Blemmer PP-500, 800, 1000, and the like, Blemmer AP-150, 400, 550, and the like, Blemmer 50PEP-300, Blemmer 50POEP-800B, Blemmer 43PAPE-600B, and the like, manufactured by NOF Corporation. The above-mentioned monomers may be used alone or in combination of two or more kinds.

[0064] The weight average molecular weight of the anionic polymer EI is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 20,000 or more, and is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 200,000 or less. The weight average molecular weight of the anionic polymer EI is a molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0065] Examples of commercially available anionic polymer EI include acrylic acid / acrylic acid alkyl ester / (N-alkyl)acrylamide copolymers such as "Ultrahold 8", "Ultrahold Strong", and "Ultrahold Power" manufactured by BASF Japan Ltd., and "Amphomer V-42" manufactured by National Starch Co., Ltd.; carboxyvinyl polymers such as the "Carbopol" series manufactured by Lubrizol Advanced Materials; (meth)acrylic acid / (meth)acrylic acid alkyl ester copolymers such as "Diahold" manufactured by Mitsubishi Chemical Corporation; ((meth)acrylic acid / diacetone acrylamide) copolymer AMP, ((meth)acrylic acid / acrylic acid alkyl ester / diacetone acrylamide) copolymer AMP, ((meth)acrylic acid / (meth)acrylic acid alkyl ester / (N-alkyl)alkyl acrylamide) copolymer AMP, such as the "Plussize L" series manufactured by GOO Chemical Industry Co., Ltd.; and (meth)acrylic acid / acrylic acid alkyl ester / vinyl pyrrolidone copolymers such as "Lubiflex VBM35" manufactured by BASF. Other examples of commercially available polymers having structural units derived from acrylic acid or methacrylic acid as monomers having an acidic group, which are used in cosmetics, include the "Aniset" series manufactured by Osaka Organic Chemical Industry Co., Ltd. Here, the term "(meth)acrylic acid alkyl ester" refers to one or more selected from the group consisting of acrylic acid alkyl esters and methacrylic acid alkyl esters. The anionic polymer EI can be used alone or in combination of two or more kinds.

[0066] From the viewpoint of improving color development and hiding power, the anionic polymer EI preferably contains a structural unit derived from a monomer having an acidic group and a structural unit derived from a (meth)acrylic acid alkyl ester, more preferably contains a structural unit derived from a monomer having an acidic group, a structural unit derived from a (meth)acrylic acid alkyl ester, and a structural unit derived from an (N-alkyl)(meth)acrylamide, still more preferably is a (meth)acrylic acid / (meth)acrylic acid alkyl ester / (N-alkyl)(meth)acrylamide copolymer, and still more preferably is an acrylic acid / acrylic acid alkyl ester / (N-alkyl)acrylamide copolymer.

[0067] (cationic polymer) In the present invention, the term "cationic" in the context of a cationic polymer means that when an unneutralized polymer is dispersed or dissolved in pure water, the pH is greater than 7; when a polymer having a quaternary ammonium group or the like is dispersed or dissolved in pure water with its counter ion being a hydroxide ion, the pH is greater than 7; or when a polymer is insoluble in pure water and the pH cannot be clearly measured, the zeta potential of a dispersion of the polymer dispersed in pure water is positive. From the viewpoint of improving color development and hiding power, the cationic polymer preferably has one or more basic groups selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and a hydrazino group, and more preferably has a quaternary ammonium group. The basic group includes, for example, one neutralized with one or more acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, and lactic acid.

[0068] The cationic polymer may be one or more selected from the group consisting of natural cationic polymers and synthetic cationic polymers. The natural cationic polymer is a polymer obtained by extraction, purification, etc. from a natural product, or a chemically modified polymer. A preferred example of the natural cationic polymer is one having a glucose residue in the polymer backbone. Specific examples of the natural cationic polymer are preferably one or more selected from the group consisting of cationic guar gum, cationic tara gum, cationic locust bean gum, cationic cellulose, cationic hydroxyalkyl cellulose, and cationic starch.

[0069] Examples of synthetic cationic polymers include polyethyleneimine, polyallylamine or acid neutralized products thereof, polyglycol-polyamine condensates, cationic polyvinyl alcohol, cationic polyvinylpyrrolidone, cationic silicone polymers, 2-(dimethylamino)ethyl methacrylate polymers or acid neutralized products thereof, poly(trimethyl-2-methacryloyloxyethyl ammonium chloride), amine / epichlorohydrin copolymers, N,N-dimethylaminoethyl diethyl methacrylate sulfate / vinylpyrrolidone copolymers, N,N-dimethylaminoethyl diethyl methacrylate sulfate / N,N-dimethylacrylamide / polyethylene glycol dimethacrylate copolymers, polydiallyldimethylammonium chloride, Examples of the copolymer include diallyldimethylammonium chloride / acrylamide copolymer, diallyldimethylammonium chloride / sulfur dioxide copolymer, diallyldimethylammonium chloride / hydroxyethylcellulose copolymer, 1-allyl-3-methylimidazolium chloride / vinylpyrrolidone copolymer, alkylamino(meth)acrylate / vinylpyrrolidone copolymer, alkylamino(meth)acrylate / vinylpyrrolidone / vinylcaprolactam copolymer, (3-(meth)acrylamidopropyl)trimethylammonium chloride / vinylpyrrolidone copolymer, and alkylaminoalkylacrylamide / alkylacrylamide / (meth)acrylate / polyethylene glycol (meth)acrylate copolymer. These cationic polymers can be used alone or in combination of two or more kinds.

[0070] Among these, from the viewpoint of improving color development and hiding power, the cationic polymer is preferably at least one selected from the group consisting of cationic polymer EII-1 (hereinafter also referred to as "cationic polymer EII-1") containing a structural unit derived from a monomer having a basic group and a cationic silicone polymer (hereinafter also referred to as "cationic silicone polymer EII-2").

[0071] [Cationic polymer EII-1] The cationic polymer EII-1 contains a structural unit derived from a monomer having a basic group. Examples of the basic group include the same as those described above. Examples of monomers having a basic group include amino group-containing monomers such as alkylamino(meth)acrylate, N,N-dialkylaminoalkyl(meth)acrylate, N-[3-(dimethylamino)propyl](meth)acrylamide, and diallyldialkylammonium, and their acid neutralized or quaternized products. These monomers having a basic group can be used alone or in combination of two or more. Acids for neutralizing the acid include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, lactic acid, etc. Quaternizing agents include alkylating agents such as alkyl halides such as methyl chloride, ethyl chloride, methyl bromide, methyl iodide, etc., and dialkyl sulfates such as dimethyl sulfate, diethyl sulfate, di-n-propyl sulfate, etc.

[0072] From the viewpoint of improving color development and hiding power, the cationic polymer EII-1 is preferably a homopolymer of a monomer having a basic group, a copolymer of a monomer having a basic group and a monomer other than the monomer having a basic group, or a condensation polymer, more preferably a copolymer of a monomer having a basic group and a monomer other than the monomer having a basic group, even more preferably a copolymer containing a structural unit derived from a monomer having a basic group, a structural unit derived from a hydrophobic monomer listed in the above-mentioned anionic polymer EI, and a structural unit derived from a nonionic monomer listed in the above-mentioned anionic polymer EI, and even more preferably a copolymer containing a structural unit derived from an amino group-containing monomer, a structural unit derived from an alkyl (meth)acrylate ester, a structural unit derived from an N-alkyl (meth)acrylamide, and an alkoxypolyethylene glycol mono(meth)acrylate. and a structural unit derived from an alkoxypolyethylene glycol mono(meth)acrylate, and even more preferably a copolymer containing structural units derived from an amino group-containing monomer, structural units derived from a hydrocarbon group alkyl (meth)acrylate ester derived from an aliphatic alcohol having from 1 to 22 carbon atoms, structural units derived from an N-alkyl(meth)acrylamide having a linear, branched or cyclic alkyl group, and structural units derived from an alkoxypolyethylene glycol mono(meth)acrylate, and even more preferably a copolymer containing structural units derived from an amino group-containing monomer, structural units derived from a hydrocarbon group alkyl (meth)acrylate ester derived from an aliphatic alcohol having from 1 to 8 carbon atoms, structural units derived from an N-alkyl(meth)acrylamide having a branched alkyl group having from 4 to 8 carbon atoms, and structural units derived from a methoxypolyethylene glycol mono(meth)acrylate. The cationic polymer EII-1 is produced by copolymerizing raw material monomers including these monomers by a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. Among these polymerization methods, the solution polymerization method is preferred.

[0073] The contents of the monomer having a basic group, the hydrophobic monomer, and the nonionic monomer in the raw material monomers during the production of the cationic polymer EII-1 (content as unneutralized amount; the same applies below), i.e., the contents of the constituent units derived from each monomer in the cationic polymer EII-1, are as follows, from the viewpoint of improving color development and hiding power. The content of the monomer having a basic group is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, still more preferably 20% by mass or less, and even more preferably 17% by mass or less. The content of the hydrophobic monomer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less. The content of the nonionic monomer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 55% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less.

[0074] From the viewpoint of improving color development and hiding power, the weight average molecular weight of the cationic polymer EII-1 is preferably 7,000 or more, more preferably 10,000 or more, even more preferably 50,000 or more, still more preferably 100,000 or more, and is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 200,000 or less, still more preferably 150,000 or less. The weight average molecular weight of the cationic polymer EII-1 is a molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0075] [Cationic Silicone Polymer EII-2] The cationic silicone polymer EII-2 is preferably a poly(N-acylalkyleneimine) / organopolysiloxane copolymer comprising an organopolysiloxane segment (x) (hereinafter also simply referred to as "segment (x)") and a poly(N-acylalkyleneimine) segment (y) (hereinafter also simply referred to as "segment (y)") consisting of an alkylene group containing a cationic nitrogen atom bonded to at least one silicon atom of the segment (x) and a repeating unit of N-acylalkyleneimine represented by the following formula (3-1):

[0076] [ka] (In the formula, R 31 represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 22 carbon atoms, or an arylalkyl group or alkylaryl group having 7 to 22 carbon atoms, and a is 2 or 3.

[0077] In formula (3-1), R 31 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and still more preferably an ethyl group. R 31 Examples of the aryl group include a phenyl group and a naphthyl group. R 31 Examples of the arylalkyl group include a phenylalkyl group, a naphthylalkyl group, etc., in which the alkyl group has 1 or more and 20 or less carbon atoms, and examples of the alkylaryl group include an alkylphenyl group, an alkylnaphthyl group, etc., in which the alkyl group has 1 or more and 20 or less carbon atoms. In formula (3-1), a is preferably 2. The degree of polymerization of the repeating unit represented by formula (3-1) in segment (y) is not particularly limited, but is preferably, for example, 1 or more and 500 or less, and more preferably 6 or more and 100 or less.

[0078] An example of the organopolysiloxane that forms the segment (x) is a compound represented by the following formula (3-2). [ka] (In the formula, R 32 represents an alkyl group having 1 to 22 carbon atoms, a phenyl group, or an alkyl group containing a nitrogen atom, and a plurality of R 32 may be the same or different, but at least one of them is an alkyl group containing a cationic nitrogen atom. b is 100 or more and 5,000 or less.

[0079] In formula (3-2), R 32 The alkyl group having 1 to 22 carbon atoms represented by the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and further preferably a methyl group. R 32 Examples of the nitrogen atom-containing alkyl group represented by the formula (I) include an alkyl group having 2 to 20 carbon atoms and preferably containing 1 to 3 nitrogen atoms. The nitrogen atom-containing alkyl group may be present on at least one of the silicon atoms at the terminal or side chain of the organopolysiloxane, and the number of nitrogen atom-containing alkyl groups in the organopolysiloxane is preferably 1 to 300, and more preferably 1 to 100.

[0080] In the formula (3-2), b is preferably 100 or more and 2,000 or less, and more preferably 350 or more and 1,500 or less. The weight average molecular weight of the organopolysiloxane forming the segment (x) is preferably 1,000 or more, more preferably 10,000 or more, even more preferably 30,000 or more, and is preferably 1,000,000 or less, more preferably 500,000 or less, even more preferably 200,000 or less, and even more preferably 150,000 or less.

[0081] In the bond between the segment (x) and the segment (y), the alkylene group containing a nitrogen atom intervening therein is, for example, an alkylene group having 2 to 20 carbon atoms and preferably containing 1 to 3 nitrogen atoms. Specifically, examples of the nitrogen atom present between carbon atoms or at the terminal of an alkylene chain include (i) secondary amines or tertiary amines, (ii) ammonium salts in which a hydrogen ion is added to a secondary amine or tertiary amine, and (iii) quaternary ammonium salts. As the poly(N-acylalkyleneimine) / organopolysiloxane copolymer, one in which segment (y) is bonded to at least one silicon atom at the end or in the side chain of segment (x) via an alkylene group containing a cationic nitrogen atom is preferred. The mass ratio of the content of segment (x) to the total content of segment (x) and segment (y) in the poly(N-acylalkyleneimine) / organopolysiloxane copolymer [content of segment (x) / [total content of segment (x) and segment (y)]] is, from the viewpoint of improving color development and hiding power, preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.4 or more, still more preferably 0.5 or more, and is preferably 0.99 or less, more preferably 0.95 or less, even more preferably 0.9 or less. In this specification, the mass ratio [content of segment (x) / [total content of segment (x) and segment (y)]] is the ratio of the mass (Mx) of segment (x) to the total mass (Mx) of segment (x) and the mass (My) of segment (y) in the poly(N-acylalkyleneimine) / organopolysiloxane copolymer. The mass ratio [content of segment (x) / [total content of segment (x) and segment (y)]] was determined by dissolving 5% by mass of poly(N-acylalkyleneimine) / organopolysiloxane copolymer in deuterated chloroform and measuring the mass ratio by nuclear magnetic resonance ( 1 It can be calculated from the integral ratio of the alkyl group or phenyl group in the segment (x) to the methylene group in the segment (y) by H-NMR analysis.

[0082] From the viewpoint of improving color development and hiding power, the weight average molecular weight of the poly(N-acylalkyleneimine) / organopolysiloxane copolymer is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 70,000 or more, and is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 200,000 or less. The weight average molecular weight of the poly(N-acylalkyleneimine) / organopolysiloxane copolymer can be calculated from the weight average molecular weight of the organopolysiloxane forming the segment (x) and the above-mentioned mass ratio [content of segment (x) / [total content of segment (x) and segment (y)]].

[0083] Suitable examples of the poly(N-acylalkyleneimine) / organopolysiloxane copolymer include one or more selected from the group consisting of poly(N-formylethyleneimine) / organopolysiloxane copolymer, poly(N-acetylethyleneimine) / organopolysiloxane copolymer, and poly(N-propionylethyleneimine) / organopolysiloxane copolymer.

[0084] The poly(N-acylalkyleneimine) / organopolysiloxane copolymer can be obtained, for example, by reacting poly(N-acylalkyleneimine), which is a ring-opening polymer of cyclic iminoether, with organopolysiloxane forming segment (x). More specifically, it can be obtained, for example, by the method described in JP 2011-126978 A. The poly(N-acylalkyleneimine) / organosiloxane copolymer used as the cationic silicone polymer EII-2 can be used alone or in combination of two or more.

[0085] (betaine polymer) In the present invention, the betaine polymer may be a copolymer of a monomer having an anionic group and a monomer having a cationic group, a polymer or copolymer of a betaine monomer, a cationic polymer into which an anionic group has been introduced, an anionic polymer into which the above-mentioned basic group has been introduced, etc. Among these, from the viewpoint of improving color development and hiding power, the betaine polymer is preferably a polymer containing a betaine structure in the side chain, and more preferably a betaine polymer containing a constitutional unit derived from a betaine monomer (hereinafter also referred to as "betaine polymer EIII"). From the viewpoint of improving color development and hiding power, the betaine monomer is preferably a monomer containing a betaine structure and a (meth)acrylamide structure, more preferably one or more selected from the group consisting of a carboxybetaine monomer, a sulfobetaine monomer, and a phosphobetaine monomer, and even more preferably a carboxybetaine monomer.

[0086] Examples of the betaine polymer include polymethacryloylethyldimethylbetaine (homopolymer of N-methacryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine), (ethyl methacrylate betaine / acrylates) copolymer (N-methacryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine / methacrylic acid alkyl ester copolymer), polyquaternium-48 (methacryloylethyldimethylbetaine / methacryloylethyltrimethylammonium chloride / hydroxyethyl methacrylate copolymer), (methacryloylethylbetaine / methacryloylethylammonium chloride / methoxy PEG methacrylate) copolymer (methacryloylethyldimethylbetaine / methacryloylethyltrimethylammonium chloride / methoxy polyethylene glycol methacrylate copolymer), and octylacrylamide / (meth)acrylic acid or (meth)acrylic acid alkyl ester / t-butylaminoethyl methacrylate copolymer. Among these, from the viewpoint of improving color development and hiding power, the betaine polymer EIII is preferably a copolymer containing a structural unit derived from a betaine monomer and a structural unit derived from a hydrocarbon group alkyl (meth)acrylate ester derived from an aliphatic alcohol having 1 to 22 carbon atoms, more preferably a copolymer containing a structural unit derived from a carboxybetaine monomer and a structural unit derived from a hydrocarbon group alkyl (meth)acrylate ester derived from an aliphatic alcohol having 1 to 22 carbon atoms, and even more preferably an N-methacryloyloxyethyl-N,N-dimethylammonium-α-N-methylcarboxybetaine / alkyl methacrylate ester copolymer.

[0087] From the viewpoint of improving color development and hiding power, the weight average molecular weight of the betaine polymer is preferably 5,000 or more, more preferably 10,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 300,000 or less. The weight average molecular weight of the betaine polymer is a polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC).

[0088] Examples of commercially available betaine polymers include Pluscise L-410W, L-402W, L-440, L-440W, K-450, and L-450W (all of which are product names manufactured by GOO Chemical Industry Co., Ltd.); Yukaformer SM and Yukaformer 301 (all of which are product names manufactured by Mitsubishi Chemical Corporation); RAM Resin-1000, -2000, -3000, and -4000 (all of which are product names manufactured by Osaka Organic Chemical Industry Co., Ltd.); Marcoat Plus 3330 (product name manufactured by The Lubrizol Chemical Industry Co., Ltd.), Amphomer 28-4910, and LV-71 (all of which are product names manufactured by Akzo Nobel Co., Ltd.), and the like.

[0089] In the present invention, from the viewpoint of improving color development and hiding power, the amount of polymer E that dissolves in water is preferably less than 5 g when polymer E that has been dried at 105°C for 2 hours and has reached a constant weight is dissolved in 100 g of water at 25°C. When the polymer E is an anionic polymer, the above-mentioned dissolution amount is the amount dissolved when 100% of the anionic groups of the polymer E are neutralized with sodium hydroxide. When the polymer E is a cationic polymer, the above-mentioned dissolution amount is the amount dissolved when 100% of the cationic groups of the polymer E are neutralized with hydrochloric acid.

[0090] From the viewpoint of improving color development and hiding power, the polymer E is preferably an amphiphilic polymer that is insoluble in the solvent D but has affinity for the solvent D and also has affinity for water. From this viewpoint, the polymer E is more preferably one or more selected from the group consisting of an anionic polymer, a cationic polymer, and a betaine polymer, still more preferably one containing a polymer containing one or more selected from the group consisting of a monomer having an acidic group, a monomer having a basic group, and a betaine monomer as a monomer structural unit, even more preferably one containing a polymer containing one or more selected from the group consisting of a monomer having an acidic group and a betaine monomer as a monomer structural unit, even more preferably one containing one or more selected from the group consisting of an anionic polymer EI and a betaine polymer EIII, and even more preferably one containing an anionic polymer EI. Moreover, from the viewpoint of improving the water resistance of the printed coating film while improving the color development and hiding power, the polymer E preferably contains a polymer having a cationic group. From the same viewpoint as above, the polymer having a cationic group is more preferably one or more selected from the group consisting of cationic polymers and betaine polymers, even more preferably a cationic polymer, even more preferably one or more selected from the group consisting of cationic polymer EII-1 and cationic silicone polymer EII-2, and even more preferably cationic silicone polymer EII-2.

[0091] Furthermore, from the viewpoint of improving the color development and hiding power while improving the water resistance of the printed coating film, two or more kinds of polymers E may be used in combination. When two or more kinds of polymer E are used in combination, from the same viewpoint as above, it is preferable that at least two kinds selected from the group consisting of anionic polymer EI, cationic polymer EII-1, cationic silicone polymer EII-2, and betaine polymer EIII are contained, more preferably a combination of anionic polymer EI and cationic polymer EII-1, a combination of anionic polymer EI and cationic silicone polymer EII-2, a combination of cationic polymer EII-1 and cationic silicone polymer EII-2, a combination of anionic polymer EI and betaine polymer EIII, a combination of cationic polymer EII-1 and betaine polymer EIII, a combination of cationic silicone polymer EII-2 and betaine polymer EIII, or a combination of anionic polymer EI, cationic silicone polymer EII-2 and betaine polymer EIII, and even more preferably a combination of anionic polymer EI and cationic silicone polymer EII-2.

[0092] The ink of the present invention may contain, as components other than those described above, various additives such as water, polymers other than dispersant B and polymer E, wetting agents, penetrating agents, surfactants, viscosity modifiers, defoamers, antifungal agents, rust inhibitors, and ultraviolet absorbing agents.

[0093] <Water> From the viewpoint of improving color development, hiding power, and decap properties, the ink of the present invention preferably further contains water. By the ink of the present invention containing water in advance, phase separation between the alcohol C and the solvent D is easily caused, and the color development and hiding power can be further improved. Preferred examples of water include purified water, ion-exchanged water, and distilled water.

[0094] <Polymer F> The ink of the present invention contains aluminum lake pigment A, pigment dispersant B, alcohol C, solvent D, and polymer E, and may also contain polymer F, which precipitates as a polymer film at the gas-liquid interface near the nozzle opening when alcohol C volatilizes in the nozzle, thereby contributing to suppression of volatilization of alcohol C at the gas-liquid interface. Polymer F is preferably a nonionic polymer, and more preferably a nonionic polymer without a polyoxyalkylene structure. The type and amount of polymer F can be adjusted according to the resolubility of the precipitated polymer film in alcohol C and the film-forming ability at the time of precipitation. This allows the drying prevention ability to be quickly realized when alcohol C evaporates, while the polymer film made of the precipitated polymer F is redissolved by new ink supplied from the ink chamber at the time of the next ejection, restoring the normal ejection state.

[0095] Examples of the polymer F include one or more selected from the group consisting of polymers having a constitutional unit derived from a nonionic monomer, water-soluble polysaccharides (cellulose-based, gum-based, starch-based, etc.) and derivatives thereof. Examples of the nonionic monomer in the nonionic polymer include (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol having 1 to 22 carbon atoms; N-vinyl-2-pyrrolidone; vinyl alcohol; polyalkylene glycol (meth)acrylates (m=1 to 30); alkoxypolyalkylene glycol mono(meth)acrylates (m=1 to 30); (meth)acrylamide and derivatives thereof. The nonionic polymer may further contain a structural unit derived from a monomer other than the nonionic monomer, such as the above-mentioned styrene-based monomer, the above-mentioned aromatic group-containing (meth)acrylate, vinyl acetate, etc.

[0096] Specific examples of polymer F include polyvinyl acetal, polyurethane polyurea, polyvinylpyrrolidone, copolymers of vinylpyrrolidone and other nonionic monomers such as vinylpyrrolidone / vinyl acetate copolymer, cellulose-based polymers such as hydroxyalkyl cellulose and nitrocellulose, polyethylene glycol, polypropylene glycol, polyglycerin, polyvinyl alcohol, pullulan, guar gum, poly N,N-dimethylacrylamide, poly N-vinylacetamide, poly N-vinylformamide, poly(2-alkyl-2-oxazoline), phenol resin, etc. Among these, the nonionic polymer is preferably one or more selected from the group consisting of nitrocellulose, phenol resin, and polyvinyl acetal, from the viewpoints of the ability to prevent the ink from drying due to precipitation and the ability to restore the ejection state to a normal ejection state by redissolution. When polyvinyl butyral is used as the polyvinyl acetal, the degree of acetalization of the polyvinyl butyral is, from the viewpoint of improving color development and hiding properties, preferably 50 mol % or more, more preferably 55 mol % or more, even more preferably 60 mol % or more, and preferably 80 mol % or less, more preferably 75 mol % or less, even more preferably 70 mol % or less.

[0097] Specific examples of commercially available polymer F include polyvinyl butyrals such as the "S-LEC B" series (manufactured by Sekisui Chemical Co., Ltd.); polyurethane polyureas such as the "BAYCUSAN" series (manufactured by Covestro Japan Co., Ltd.); hydroxyethyl celluloses such as HEC Daicel SE900, SE850, SE600, SE550, and SE400 (all manufactured by Daicel FineChem Co., Ltd., product names); highly polymerized polyethylene glycols such as Polyox WSRN-12K, WSRN-60K, and WSR-301 (manufactured by Dow Chemical Co., Ltd., product names); polyethylene oxides such as PEO-27, PEO-18, PEO-15, and PEO-8 (manufactured by Sumitomo Seika Chemical Co., Ltd., product names); polyvinylpyrrolidones such as Rubiscol K90, K80, and K30 (manufactured by BASF, product names); and polyvinyl alcohols such as the "GOHSENOL" series (manufactured by Mitsubishi Chemical Corporation).

[0098] <High boiling point water-soluble organic solvent G> The ink of the present invention may contain a high-boiling point water-soluble organic solvent G as a solvent other than the alcohol C and the solvent D, which are added to general inkjet recording inks in order to improve the ejection properties of the ink, within a range that does not impair the effects of the present invention. In the present invention, the "high-boiling water-soluble organic solvent G" is an organic solvent that is miscible with water in any ratio and has a boiling point of 100° C. or higher. The boiling point of the high-boiling water-soluble organic solvent G is preferably 400° C. or lower.

[0099] Examples of the water-soluble organic solvent G include monohydric alcohols other than the alcohol C, polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. In addition, when one or more compounds selected from the group consisting of monohydric alcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds are used as the water-soluble organic solvent G, a mixture of two or more compounds included within each concept of the monohydric alcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds may be used.

[0100] Examples of the monohydric alcohol include n-butanol (boiling point: 118° C.) and n-pentanol (boiling point: 138° C.). 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), 3-methyl-1,3-butanediol (boiling point 203°C), 1,5-pentanediol (boiling point 242°C), and 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), triethylene glycol (boiling point 285 ° C), tripropylene glycol (boiling point 273 ° C), glycerin (boiling point 290 ° C), etc.

[0101] 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.

[0102] 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.), sulfolane (boiling point 285° C.), and thiodiglycol (boiling point 282° C.).

[0103] Since the high-boiling-point water-soluble organic solvent G has high moisturizing properties, it absorbs water and interferes with contact between solvent D and water, preventing phase separation between alcohol C and solvent D. This inhibits the formation of primary particles having a core-shell structure in which solvent D is the core and polymer E is the shell, and is thought to impair color development and hiding power. Furthermore, when polymer E dissolves in high-boiling point water-soluble organic solvent G, the formation of primary particles having a core-shell structure in which solvent D serves as the core and polymer E serves as the shell, which is formed as a result of evaporation of alcohol C from the coating film, is inhibited, which is thought to inhibit color development and hiding power. From this viewpoint, the content of the water-soluble organic solvent having a boiling point of 200°C or higher as the high-boiling-point water-soluble organic solvent G in the ink of the present invention is preferably less than 5% by mass, more preferably less than 2% by mass, even more preferably less than 1% by mass, still more preferably 0.1% by mass or less, still more preferably substantially 0% by mass, and even more preferably 0% by mass.

[0104] <Surfactant H> From the viewpoint of adjusting the dot diameter and improving the printing quality, the ink of the present invention may contain a surfactant H. Examples of the surfactant H include nonionic surfactants, anionic surfactants, and amphoteric surfactants. Among these, nonionic surfactants are preferred. Examples of nonionic surfactants include (1) polyoxyalkylene alkyl ethers, alkenyl ethers, alkynyl ethers, or aryl ethers obtained by adding ethylene oxide, propylene oxide, or butylene oxide to a saturated or unsaturated, linear or branched higher alcohol, polyhydric alcohol, or aromatic alcohol having 8 to 22 carbon atoms; (2) esters of polyvalent fatty acids and higher alcohols having a saturated or unsaturated, linear or branched hydrocarbon group having 8 to 22 carbon atoms; (3) polyoxyalkylene aliphatic amines having a linear or branched alkyl or alkenyl group having 8 to 20 carbon atoms; (4) ester compounds of higher fatty acids having 8 to 22 carbon atoms and polyhydric alcohols, or compounds obtained by adding ethylene oxide, propylene oxide, or butylene oxide to the ester compounds; (5) silicone-based surfactants; and (6) acetylene glycol-based surfactants.

[0105] Examples of silicone 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. Polyether-modified silicones have a structure in which the side chains and / or terminal hydrocarbon groups of silicone oil are replaced with polyether groups. Examples of the polyether groups include polyethyleneoxy groups, polypropyleneoxy groups, and polyalkyleneoxy groups in which ethyleneoxy groups and propyleneoxy groups (trimethyleneoxy groups or propane-1,2-diyloxy groups) are added in a block or random manner. Examples of polyether-modified silicones include compounds in which a polyether group is grafted onto a silicone main chain, and compounds in which silicone and a polyether group are bonded in the form of blocks. 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.

[0106] The acetylene glycol surfactant may be one or more selected from the group consisting of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, 3,5-dimethyl-1-hexyne-3-ol, and ethylene oxide adducts thereof.

[0107] Commercially available nonionic surfactants include, for example, the KF series manufactured by Shin-Etsu Chemical Co., Ltd.; the Surfynol series manufactured by Nissin Chemical Industry Co., Ltd. and Air Products & Chemicals; the Acetylenol series manufactured by Kawaken Fine Chemicals Co., Ltd.; and "EMULGEN 120 (polyoxyethylene lauryl ether)" manufactured by Kao Corporation.

[0108] (Manufacture of alcohol-based ink for inkjet recording) The method for producing the ink of the present invention is not particularly limited, and any known method can be used. The method for producing the ink of the present invention is to prepare an aluminum lake pigment dispersion in which the aluminum lake pigment A is dispersed in a liquid medium by the dispersant B by mixing and dispersing the aluminum lake pigment A and the aluminum lake pigment dispersion obtained is mixed with alcohol C, solvent D, polymer E, and additives as necessary to obtain the ink. There is no limitation on the mixing method when the ink of the present invention is produced by mixing the pigment dispersion with alcohol C, solvent D, polymer E, and additives as necessary, and any method, tool, or device can be used.

[0109] [Preparation of Aluminum Lake Pigment Dispersion] There is no particular restriction on the method for producing the aluminum lake pigment dispersion (hereinafter, simply referred to as "pigment dispersion"), but from the viewpoint of reducing the particle size of the pigment particles dispersed in the pigment dispersion and improving color development, hiding power, and decap properties, a method is preferred in which a pigment mixture containing aluminum lake pigment A, dispersant B, a liquid medium, and, if necessary, additives is subjected to a dispersion treatment by applying physical stress using a dispersing machine. In addition, in the dispersion treatment, it is preferable to further add a neutralizing agent, if necessary, to neutralize and ionize at least a portion of the anionic groups of dispersant B. The liquid medium is preferably the same solvent as the alcohol C, water, etc., and more preferably one or more selected from the group consisting of ethanol and water. The dispersion treatment of the pigment mixture may be carried out in one dispersion, or from the viewpoint of obtaining a uniform pigment dispersion, it may be carried out by pre-dispersing and then further carrying out main dispersion using a disperser. The dispersing machine is not particularly limited, and examples thereof include kneading and mixing machines such as kneaders; media-type dispersing machines such as attritors, ball mills, sand mills using glass beads or zirconia beads, and paint shakers; and colloid mills. From the viewpoint of reducing the viscosity of the pigment dispersion, the temperature of the dispersion treatment is preferably kept at 3°C ​​or more and 35°C or less, more preferably 5°C or more and 20°C or less, and even more preferably 5°C or more and 10°C or less. The time for the dispersion treatment is preferably from 2 hours to 200 hours, more preferably from 3 hours to 50 hours, from the viewpoint of sufficiently finely dispersing the pigment. When alcohol C is used as the liquid medium, the alcohol C may be removed from the dispersion after the dispersion treatment under reduced pressure using a known distillation or evaporation apparatus to obtain an aluminum lake pigment aqueous dispersion.

[0110] The content of aluminum lake pigment A in the pigment dispersion is preferably 2 mass % or more, more preferably 3 mass % or more, and even more preferably 4 mass % or more, from the viewpoint of easily adjusting the aluminum lake pigment to a desired particle diameter, and from the same viewpoint as above, it is preferably 20 mass % or less, more preferably 17 mass % or less, and even more preferably 15 mass % or less. The content of dispersant B in the pigment dispersion is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more, from the viewpoint of easily adjusting the aluminum lake pigment to a desired particle diameter, and from the same viewpoint as above, it is 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 dispersant B in the pigment dispersion [aluminum lake pigment A / [aluminum lake pigment A+dispersant B]] is, from the viewpoint of easily adjusting the aluminum lake pigment to a desired particle size and from the viewpoint of improving the decap property of the ink, preferably 0.10 or more, more preferably 0.20 or more, even more preferably 0.25 or more, still more preferably 0.30 or more, still more preferably 0.35 or more, still more preferably 0.40 or more, still more preferably 0.45 or more, and is preferably 0.90 or less, more preferably 0.85 or less, still more preferably 0.80 or less, still more preferably 0.75 or less, still more preferably 0.70 or less, still more preferably 0.65 or less, still more preferably 0.60 or less, still more preferably 0.55 or less. The water content in the pigment dispersion is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of easily adjusting the aluminum lake pigment to a desired particle diameter, and from the same viewpoint as above, it is preferably 97% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less.

[0111] [Physical Properties of Aluminum Lake Pigment Dispersion] The volume average particle size of the aluminum lake pigment A dispersed in the pigment dispersion is preferably 200 nm or less, more preferably 170 nm or less, even more preferably 150 nm or less, still more preferably 140 nm or less, still more preferably 135 nm or less, and still more preferably 130 nm or less from the viewpoint of improving the decap property, and is preferably 50 nm or more, more preferably 70 nm or more, still more preferably 90 nm or more, and still more preferably 110 nm or more from the viewpoint of the 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 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, still more preferably 2.5 mPa·s or more, still more preferably 3 mPa·s or more, still more preferably 3.5 mPa·s or more, and still more preferably 4 mPa·s or more, from the same viewpoints as above, and is preferably 20 mPa·s or less, more preferably 15 mPa·s or less, still more preferably 13 mPa·s or less, and still more preferably 10 mPa·s or less. The viscosity at 20°C is measured by the method described in the examples.

[0112] Since the ink of the present invention uses the highly safe aluminum lake pigment A, it is preferably used in the food, medical, and cosmetic fields. Among these, the ink of the present invention is preferably used in the cosmetic field. When the ink of the present invention is used in the cosmetic field, it is preferably used as an ink to be applied to hair, skin (including lips), or nails, and more preferably used as an ink to be applied to hair. The ink to be applied to hair is preferably one or more selected from the group consisting of hair dyeing inks such as hair mascara and hair color; styling inks such as hair wax, hair spray, hair mousse and hair foam; and hair growth inks. The ink to be applied to the skin is preferably one or more selected from the group consisting of base makeup inks such as makeup base ink, foundation, and concealer; point makeup inks such as blusher, eye shadow, mascara, eyeliner, eyebrow pencil, overcoat agent, and lipstick; UV protection cosmetic inks such as sunscreen lotions and sunscreen creams; skin cleansing cosmetic inks such as facial cleansers and cleansing cosmetics; and basic cosmetic inks such as serums, packs, and massage cosmetics. The ink for ink-jet recording to be applied to nails is preferably applied to cosmetic inks for nail beautification, such as nail enamel and nail gloss. The ink of the present invention can reduce the particle size of dispersed pigment particles and has excellent color development, hiding properties, and decap characteristics, and is therefore preferably used as a cosmetic composition that is applied to the skin, hair, or nails using an inkjet device, i.e., an alcohol-based cosmetic composition for inkjet recording.

[0113] Furthermore, when the ink of the present invention is used in the field of cosmetics, it can be used to decorate the surface of powder cosmetics such as foundation, eye shadow, blush, eyebrow, etc., in various compact cases that store such powder cosmetics with a color or pattern different from the original color of the powder cosmetics. In this case, when the compact case is opened, beautiful and detailed decorations and images are seen, but since there is only a thin color-developing printed coating on the surface of the powder cosmetics, when actually using the case, the makeup can be done with the color of the powder cosmetics underneath the printed coating. This not only enhances the mood of the person wearing the makeup, but also makes it possible to use it as a special gift or to eliminate counterfeit cosmetics.

[0114] (Content of each component in alcohol-based ink for inkjet recording) From the viewpoint of coloring degree, the content of aluminum lake pigment A in the ink of the present invention is preferably 0.2 mass % or more, more preferably 0.4 mass % or more, even more preferably 0.6 mass % or more, still more preferably 0.8 mass % or more, and still more preferably 1.0 mass % or more, and from the viewpoint of improving decap properties, it is preferably 20 mass % or less, more preferably 15 mass % or less, even more preferably 10 mass % or less, still more preferably 7 mass % or less, still more preferably 5 mass % or less, and still more preferably 3 mass % or less.

[0115] From the viewpoint of improving the dispersion stability of the ink and improving the decap properties, the content of dispersant B in the ink of the present invention is preferably 0.2% by mass or more, more preferably 0.4% by mass or more, even more preferably 0.6% by mass or more, still more preferably 0.8% by mass or more, still more preferably 1.0% by mass or more, and is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, still more preferably 4% by mass or less, and still more preferably 2% 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 dispersant B in the ink of the present invention [aluminum lake pigment A / [aluminum lake pigment A+dispersant B]] is preferably 0.10 or more, more preferably 0.20 or more, even more preferably 0.25 or more, still more preferably 0.30 or more, still more preferably 0.35 or more, still more preferably 0.40 or more, still more preferably 0.45 or more, and is preferably 0.90 or less, more preferably 0.85 or less, even more preferably 0.80 or less, still more preferably 0.75 or less, still more preferably 0.70 or less, still more preferably 0.65 or less, still more preferably 0.60 or less, still more preferably 0.55 or less.

[0116] From the viewpoint of improving color development, hiding power, and decap properties, the content of alcohol C in the ink of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more, and from the same viewpoints as above, it is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, and even more preferably 55% by mass or less.

[0117] From the viewpoint of improving color development, hiding properties, and decap properties, the content of solvent D in the ink of the present invention is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, still more preferably 15% by mass or more, and still more preferably 20% by mass or more, and from the same viewpoints as above, it is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less, and still more preferably 33% by mass or less. The mass ratio of the content of alcohol C to solvent D in the ink of the present invention [alcohol C / solvent D] is preferably 0.6 or more, more preferably 1.0 or more, even more preferably 1.3 or more, and is preferably 7.0 or less, more preferably 6.0 or less, even more preferably 5.0 or less, still more preferably 4.0 or less, still more preferably 3.0 or less, and even more preferably 2.7 or less.

[0118] From the viewpoint of improving color development, hiding properties, and decap properties, the content of polymer E in the ink of the present invention is preferably 0.3 mass % or more, more preferably 0.7 mass % or more, even more preferably 1.0 mass % or more, still more preferably 1.3 mass % or more, and even more preferably 1.5 mass % or more, and from the same viewpoints as above, it is preferably 10 mass % or less, more preferably 7 mass % or less, even more preferably 5 mass % or less, and even more preferably 3 mass % or less. The mass ratio of the content of polymer E to aluminum lake pigment A in the ink of the present invention [polymer E / aluminum lake pigment A] is preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, still more preferably 1.0 or more, still more preferably 1.3 or more, and is preferably 3.0 or less, more preferably 2.5 or less, still more preferably 2.0 or less, still more preferably 1.7 or less. The mass ratio of the content of Polymer E to Dispersant B in the ink of the present invention [Polymer E / Dispersant B] is preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, still more preferably 1.0 or more, still more preferably 1.3 or more, and is preferably 3.0 or less, more preferably 2.5 or less, still more preferably 2.0 or less, still more preferably 1.7 or less.

[0119] The water content in the ink of the present invention is, from the viewpoint of improving color development, hiding power, and decap properties, preferably 7% by mass or more, more preferably 13% by mass or more, even more preferably 15% by mass or more, and still more preferably 17% by mass or more, and from the viewpoint of maintaining an appropriate ink viscosity, preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, and still more preferably 23% by mass or less.

[0120] From the viewpoint of improving color development and hiding power, the content of the high-boiling point water-soluble organic solvent G in the ink of the present invention is preferably less than 5% by mass, more preferably less than 2% by mass, even more preferably less than 1% by mass, still more preferably 0.1% by mass or less, still more preferably substantially 0% by mass, and even more preferably 0% by mass. The content of glycerin in the ink of the present invention is preferably less than 5% by mass, more preferably less than 3% by mass, and even more preferably less than 1% by mass, from the viewpoint of improving color development and hiding power.

[0121] From the viewpoint of adjusting the dot diameter and improving print quality, the content of surfactant H in the ink of the present invention is preferably less than 0.5% by mass, more preferably less than 0.1% by mass, even more preferably less than 0.05% by mass, and still more preferably less than 0.01% by mass. From the viewpoint of improving color development and hiding properties, the total content of the water-soluble organic solvent having a boiling point of 200° C. or more as the high-boiling point water-soluble organic solvent G in the ink of the present invention is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, still more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, still more preferably substantially 0% by mass, and still more preferably 0% by mass.

[0122] (Physical properties of alcohol-based ink for inkjet recording) The volume average particle size of the aluminum lake pigment A dispersed in the ink of the present invention is preferably 200 nm or less, more preferably 170 nm or less, even more preferably 150 nm or less, still more preferably 140 nm or less, still more preferably 135 nm or less, still more preferably 130 nm or less from the viewpoint of improving decapability, and is preferably 50 nm or more, more preferably 70 nm or more, still more preferably 90 nm or more, still more preferably 110 nm or more from the viewpoint of ink productivity. The volume average particle size is measured by the same method as the method for measuring the volume average particle size of the aluminum lake pigment A dispersed in the pigment dispersion described in the Examples. From the viewpoint of improving decap properties, the viscosity of the 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, still more preferably 2.5 mPa·s or more, still more preferably 3.0 mPa·s or more, and still more preferably 3.5 mPa·s or more, and from the same viewpoints as above, it is preferably 25 mPa·s or less, more preferably 20 mPa·s or less, and still more preferably 17 mPa·s or less. The viscosity of the ink of the present invention at 20°C is measured by the method described in the examples.

[0123] [Inkjet recording method] The inkjet recording method of the present invention is a method in which the above-mentioned alcohol-based ink for inkjet recording is ejected onto a recording medium using an inkjet recording apparatus to form a printed coating film. Since aluminum lake pigment A is a pigment with a relatively small specific gravity, an inkjet recording device without a dispersing means may be used, but it is preferable to use an inkjet recording device having a dispersing means for dispersing aluminum lake pigment A in the ink of the present invention. There are no particular limitations on the dispersing means as long as it is a means capable of dispersing aluminum lake pigment A in the ethanol medium of the ink of the present invention by mechanical force.

[0124] When the inkjet recording apparatus has a dispersion means, it is preferable that the inkjet recording method includes step 1 of redispersing the ink of the present invention by the dispersion means, and step 2 of ejecting the ink of the present invention redispersed in step 1 onto a recording medium. By using the ink of the present invention in the inkjet recording method, even if the aluminum lake pigment A dispersed in the ink of the present invention settles or aggregates during printing or after a printing pause, the aluminum lake pigment A can be easily redispersed by the dispersing means of the inkjet recording apparatus, thereby improving the decap characteristics. From this viewpoint, the inkjet recording apparatus preferably has at least an ink ejection means, a container for filling the ink of the present invention (ink-filled container), an ink flow path, and a dispersing means for dispersing the aluminum lake pigment A contained in the ink of the present invention, and the ink-filled container may further have an ink pre-filling container.

[0125] As the ink ejection means, there is a method of ejecting ink using a thermal or piezo inkjet ejection head. As the ejection method, the thermal method is preferable from the viewpoint of decap characteristics. That is, in the inkjet recording method of the present invention, a method is preferable in which the ink of the present invention is used for the thermal method, a container filled with the above-mentioned alcohol-based ink for inkjet recording is mounted on an inkjet recording device, and the above-mentioned alcohol-based ink for inkjet recording is ejected onto a recording medium using a thermal ejection head to form a printed coating film.

[0126] The recording medium is not particularly limited, and examples thereof include recording media used in printing in the food, medical, and cosmetic fields. Examples of the recording medium include high-absorbency recording media such as plain paper and wood-free paper; low-absorbency recording media such as art paper, coated paper, and synthetic resin film; and metals. In addition, when the above-mentioned alcohol-based ink for inkjet recording is used as a cosmetic composition, it can also be applied to a cosmetic method in which a cosmetic coating film is formed using hair, skin (including lips), or nails as a recording medium. Such a cosmetic method can be used as a simple cosmetic method in which the above-mentioned alcohol-based ink for inkjet recording is used as a temporary hair dye to dye hair in a mesh shape, applying color only to a desired part of the hair. EXAMPLES

[0127] In the following Synthesis Examples, Production Examples, Examples and Comparative Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. Various physical properties were measured by the following methods.

[0128] (1) Measurement of the acid value of pigment dispersant B The measurement was performed according to the potentiometric titration method of JIS K 0070.

[0129] (2) Measurement of weight average molecular weight of pigment dispersant B The measurement was performed by gel permeation chromatography under the following conditions. GPC equipment: Tosoh Corporation "HLC-8320GPC" Columns: "TSKgel PW", "TSKgel G4000PW", and "TSKgel G2500PW" manufactured by Tosoh Corporation Eluent: 0.2M phosphate buffer / acetonitrile = 9 / 1 (volume ratio) solution Flow rate: 1.0mL / min Column temperature: 40℃ Standard substance: Polyethylene glycol with a monodisperse weight-average molecular weight that has been previously specified

[0130] (3) Measurement of solids concentration 10.0 g of sodium sulfate, which had been kept constant in a desiccator, was weighed out into a 30 ml polypropylene container (φ=40 mm, height=30 mm), and about 1.0 g of the sample was added thereto and mixed, then accurately weighed, and maintained at 105°C for 2 hours to remove volatile matter, and further left in the desiccator for 15 minutes, and the mass was measured. The mass of the sample after removing the volatile matter was taken as the solid content, and divided by the mass of the sample added to obtain the solid content concentration (%).

[0131] (4) Measurement of the volume average particle size of aluminum lake pigment A dispersed in a pigment dispersion The volume average particle size of aluminum lake pigment A dispersed in the pigment dispersion was measured using a zeta potential / particle size measurement system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.) when the concentration of aluminum lake pigment A in the pigment dispersion was approximately 5 × 10-3 %, a sample diluted with water was placed in a measurement cell, and measurements were taken at 25°C, with 100 cumulative measurements, and the refractive index of water (1.333) was entered as the refractive index of the dispersion solvent.

[0132] (5) Viscosity measurement The viscosity of the hydrogenated polyisobutene, the pigment dispersion, or the alcohol-based ink for ink-jet recording 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).

[0133] Synthesis Example 1-1 (Synthesis of pigment dispersant B-1) A 2 L glass reaction vessel equipped with two dropping funnels 1 and 2 was charged with 233 g of isopropanol, and the inside atmosphere was replaced with nitrogen gas. On the other hand, a monomer solution of 15 g of acrylic acid (Wako Special Grade Reagent 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, product name "BLEMMER PME-1000") as monomer (b-2) (hereinafter referred to as "MPEGMA (n=23)") was prepared, placed in the 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, product name "Perloyl L") as a polymerization initiator with 10.0 g of isopropanol, and the solution was placed in the dropping funnel 2 and purged with nitrogen gas. Next, under a nitrogen atmosphere, the isopropanol in the reaction vessel was maintained at 80°C while being stirred, and the monomer solution in the dropping funnel 1 and the polymerization initiator solution in the dropping funnel 2 were each simultaneously dropped gradually into the reaction vessel over a period of 6 hours to carry out polymerization, thereby obtaining a polymerization reaction solution. Next, the pressure in the reaction vessel was adjusted to 50 kPa, and the temperature in the reaction vessel was adjusted to 60° C., and isopropanol was distilled off from the obtained polymerization reaction solution, and the polymerization reaction solution was concentrated until the solid content reached 90%. Next, the pressure in the reaction vessel was adjusted to normal pressure, and the temperature in the reaction vessel was adjusted to 60°C. A polymerization initiator solution prepared by mixing 0.7 g of dilauroyl peroxide (Perloyl L) as a polymerization initiator with 10.0 g of isopropanol was added under a nitrogen atmosphere, 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 was adjusted to 60° C., and the isopropanol was distilled off to concentrate the polymerization reaction solution until the solid content reached 99% or more. Next, while maintaining the pressure inside the reaction vessel at 2 kPa, the temperature inside the reaction vessel was raised to 65° C., and then, while maintaining the temperature at 65° C., heat aging was carried out for 46 hours. Thereafter, the temperature inside the reaction vessel was cooled to 40° C., and 100 g of ethanol was added and stirred to redissolve the polymer inside the reaction vessel. Next, 1.74 g of a 48% aqueous sodium hydroxide solution (amount of sodium hydroxide: 834 mg) was added to the reaction vessel to neutralize the polymer (neutralization degree: 10 mol%), and ethanol was added to the reaction vessel so that the solid content concentration became 40%, to obtain an ethanol solution of pigment dispersant B-1. The physical properties of pigment dispersant B-1 are shown in Table 1.

[0134] Synthesis Examples 1-2 to 1-3 and Comparative Synthesis Example 1-1 (Synthesis of Pigment Dispersants B-2 to B-3 and B-C1) An ethanol solution of each pigment dispersant was obtained in the same manner as in Synthesis Example 1-1, except that the monomer composition in Synthesis Example 1-1 was changed as shown in Table 1. The physical properties of each pigment dispersant are shown in Table 1.

[0135] [Table 1]

[0136] Production Example 1-1 (Production of Pigment Dispersion P-1) 75 parts of the ethanol solution of pigment dispersant B-1 obtained in Synthesis Example 1-1 (solid concentration 40%) (30 parts as solid content (pigment dispersant (B-1))), 30 parts of aluminum lake pigment A-1 ["SunCROMA FD&C Blue 1 AL Lake" (blue No. 1 aluminum lake pigment, manufactured by Sun Chemical)], and 495 parts of water were added, and 378 g of zirconia beads having a diameter of 50 μm were added, and the mixture was dispersed at 5 ° C. for 6 hours using a small bead mill disperser "Ultra Apex Mill UAM-015" (manufactured by Hiroshima Metal & Machinery Co., Ltd.). The zirconia beads were removed using a 75 μm mesh, and the ethanol was removed from the resulting dispersion at 40 ° C. under reduced pressure, and the solid concentration was adjusted with water to obtain pigment dispersion P-1 (solid concentration 10%). The volume average particle size and viscosity of pigment dispersion P-1 are shown in Table 2.

[0137] Production Examples 1-2 to 1-3 and Comparative Production Example 1-1 (Production of Pigment Dispersions P-2 to P-3 and P-C1) Pigment dispersions P-2 to P-3 and P-C1 (solid content concentration 10%) were obtained in the same manner as in Production Example 1-1, except that pigment dispersant B-1 was changed to pigment dispersant B-2, B-3 or B-C1.

[0138] Production Examples 1-4 to 1-5 (Production of Pigment Dispersions P-4 to P-5) Pigment dispersions P-4 to P-5 (solid concentration 10%) were obtained in the same manner as in Production Example 1-1, except that water and ethanol were used to adjust the water and ethanol contents and solid concentrations to those shown in Table 2.

[0139] [Table 2]

[0140] Synthesis Example 2-1 (Synthesis of Cationic Silicone Polymer 1) 73.7 g (0.74 mol) of 2-ethyl-2-oxazoline was mixed with 156.0 g of ethyl acetate, and the resulting mixture was dehydrated with 12.0 g of molecular sieve "Zeorum A-4" (manufactured by Tosoh Corporation) at 28°C for 15 hours. 2.16 g (0.014 mol) of diethyl sulfate was added to the resulting ethyl acetate solution of dehydrated 2-ethyl-2-oxazoline, and the mixture was heated under reflux at 80°C for 8 hours under a nitrogen atmosphere to obtain a terminal-reactive poly(N-propionylethyleneimine) (number average molecular weight is 6,000) solution. Separately, 70.0 g of side-chain primary aminopropyl-modified polydimethylsiloxane "KF-864" (Shin-Etsu Silicones, weight average molecular weight 50,000 (catalog value), amine equivalent 3,800) was mixed with 140.0 g of ethyl acetate, and the mixture was dehydrated with 15.0 g of molecular sieves at 28°C for 15 hours. Next, the terminal reactive poly(N-propionylethyleneimine) solution obtained above was added all at once to the dehydrated side chain primary aminopropyl modified polydimethylsiloxane solution, and heated to reflux at 80° C. for 10 hours. The reaction mixture was concentrated under reduced pressure to obtain a poly(N-propionylethyleneimine) / dimethylpolysiloxane copolymer (hereinafter also referred to as "cationic silicone polymer 1") as a white rubber-like solid (135 g). The weight average molecular weight of the cationic silicone polymer 1 was 100,000 (calculated value), and the mass ratio [content of organopolysiloxane segment (x) / [total content of organopolysiloxane segment (x) and poly(N-acylalkyleneimine) segment (y)]] was 0.50.

[0141] Example 1 (Alcohol-based ink X-1 for ink-jet recording) The pigment dispersion P-1 (solid concentration 10%) obtained in Production Example 1-1, ethanol as alcohol C, "Pearlream 3" (hydrogenated polyisobutene, boiling point 179°C, Ra45, viscosity 1.4 mPa·s) manufactured by NOF Corporation as solvent D, cationic silicone polymer 1 as polymer EII-2, and "Pluscise L-9909U" (display name: (acrylates / alkyl acrylate (C1-18) / alkyl (C1-8) acrylamide) copolymer AMP) manufactured by GOO Chemical Industry Co., Ltd. as anionic polymer EI were mixed in the following formulation so that the content of aluminum lake pigment A in the ink for inkjet recording was 1.1% and the content of pigment dispersant B was 1.1%, and the resulting mixture was filtered with a 20 mL needleless syringe equipped with a cellulose acetate filter (outer diameter 2.5 cm, manufactured by Sartorius Co., Ltd.) with a pore size of 1.2 μm to remove coarse particles, thereby obtaining alcohol-based ink for inkjet recording X-1. The viscosity of the inkjet recording alcohol-based ink X-1 at 20°C was 8.2 mPa·s. <Blend composition> Pigment Dispersion P-1 22 parts Ethanol 56.4 parts Pearleem 3 20 copies Cationic silicone polymer 1 1.2 parts Plus Size L-9909U 0.4 parts

[0142] Examples 2 to 7 and Comparative Examples C1 to C8 (Inkjet Recording Alcohol-Based Inks X-2 to X-7 and X-C1 to X-C8) In the same manner as in Example 1, except that the blending compositions were changed to those shown in Table 3, each alcohol-based ink for ink-jet recording was obtained. Details of Pearleem 4 listed in Table 3 are as follows. Pearleem 4: NOF Corporation's "Pearleam 4" (hydrogenated polyisobutene, boiling point 262°C, Ra45, viscosity 3.7mPa·s)

[0143] [evaluation] <Evaluation of color development and hiding power> Each of the alcohol-based inks for inkjet recording in Examples 1 to 7 and Comparative Examples C1 to C8 was filled into an inkjet head "DMC-11610" (manufactured by Fujifilm Corporation), and printing was performed using a material printer "DMP-2831" (manufactured by Fujifilm Corporation). The printing mode used a standard waveform, the voltage was set to 35V, and the dot space of the printed image was set to 20 μm. A black polyester film "Lumirror X30" (Toray Industries, Inc.) was used as the recording medium, and a solid image of 10 mm height x 10 mm width was printed four times in layers at 100% duty. CIE L of the resulting print * a * b * Color space coordinates (L * 1, a * 1, b * 1) was measured. The CIE L of the unprinted black polyester film "Lumirror X30" (Toray Industries, Inc.) * a * b * Color space coordinates (L * 2, a * 2, b * 2) is measured, and the difference ΔL * , Δa * , and Δb * The obtained difference ΔL * ,Δa * , and Δb * The color development was evaluated by calculating the saturation ΔC from the following formula, and the color difference ΔE from the following formula to evaluate the hiding power. The larger the saturation ΔC, the better the color development, and the larger the color difference ΔE, the better the hiding power. The results are shown in Table 3. Saturation ΔC=〔(Δa * ) 2 +(Δb * ) 2 〕 0.5 Color difference ΔE=〔(ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2 〕 0.5

[0144] <Evaluation of decap characteristics> [Evaluation of ejection recovery property] Using the inkjet head described above filled with each of the alcohol-based inks for inkjet recording in Examples 1 to 7 and Comparative Examples C1 to C8, the nozzle surface was wiped with a nonwoven fabric impregnated with ethanol, and ejection from all nozzles was confirmed in the drop watcher mode of the printing machine described above. Next, the ink nozzle surface was left for 5 seconds without protection, and the discharge state was checked again in the drop watcher mode. In this discharge, if the number of nozzles that could not discharge out of the total 16 nozzles was 9 or more, the nozzle drying time was set to 0 seconds. In the case where the number of nozzles that could discharge was 10 or more, the nozzle surface was wiped with a nonwoven fabric impregnated with ethanol, and the discharge state was checked again in the drop watcher mode. After performing wipe maintenance with a nonwoven fabric impregnated with ethanol until the number of nozzles that could discharge was 12 or more, the ink nozzle surface was left for 10 seconds without protection, and if the number of nozzles that could not discharge out of the total 16 nozzles in this discharge was 9 or more, the nozzle drying time was set to 5 seconds. In the case where the number of nozzles that could discharge out of the total 16 nozzles was 10 or more, the ink nozzle surface was left for 15 seconds without protection, and if the number of nozzles that could not discharge out of the total 16 nozzles in this discharge was 9 or more, the nozzle drying time was set to 10 seconds. This procedure was repeated while the ink nozzle surface was left unprotected for an extended period of time of 30 seconds, 45 seconds, 60 seconds, and 75 seconds, each time at 15 second intervals, and the evaluation was repeated. The longer the nozzle drying time, the better the ejection recovery and the less frequent the maintenance. The results are shown in Table 3.

[0145] [Evaluation of Discharge Durability] Using the inkjet head described above filled with each of the alcohol-based inks for inkjet recording in Examples 1 to 7 and Comparative Examples C1 to C8, the nozzle surface was wiped with a nonwoven fabric impregnated with ethanol, and ejection from all nozzles was confirmed in the drop watcher mode of the printing machine described above. Next, the printer with the inkjet head attached was left at room temperature for 24 hours. Next, the nozzle surface was wiped with a nonwoven fabric soaked in ethanol, and the number of nozzles capable of ejecting was confirmed in the drop watcher mode. The percentage of the number of nozzles capable of ejecting relative to the total number of nozzles was taken as the ejection rate after the nozzle was left alone, and the ejection durability was evaluated. The higher the ejection rate after the nozzle was left alone, the higher the ejection durability and the easier the maintenance. The results are shown in Table 3.

[0146] [Table 3]

[0147] From Table 3, it can be seen that the alcohol-based inks for inkjet recording of Examples 1 to 7 have excellent color development and hiding power, while also having excellent ejection recovery properties and ejection durability, and are able to maintain the good ejection performance before being left alone even when the nozzle is left in an open state, and thus have excellent decap characteristics, as they are called.

[0148] Examples 11 to 28 (alcohol-based inks for inkjet recording Y-1 to Y-18) In the same manner as in Example 1, except that the blending compositions were changed to those shown in Table 4, each alcohol-based ink for ink-jet recording was obtained. The color development, hiding power, ejection recovery, and ejection durability of each of the obtained alcohol-based inks for inkjet recording were evaluated in the same manner as described above, and the effect of reducing the particle size of the dispersed pigment particles was evaluated by the following evaluation method. The results are shown in Table 4.

[0149] <Effect of reducing the size of dispersed pigment particles> The viscosity of each of the alcohol-based inkjet recording inks of Examples 11 to 28 was measured. The results are shown in Table 4. The viscosity of each of the alcohol-based inkjet recording inks Y-1 to Y-18 was 20 mPa s or less, and when each of the alcohol-based inkjet recording inks was filtered using a cellulose acetate syringe filter with a pore size of 1.2 μm, no decrease in filtration speed due to pressure loss occurred. From this, it is presumed that the dispersion state of the aluminum lake pigment A was stable.

[0150] [Table 4]

[0151] From Table 4, it can be seen that the alcohol-based inks for inkjet recording of Examples 11 to 28 have excellent color development and hiding power, while also having excellent ejection recovery properties and ejection durability, and are able to maintain the good ejection performance before being left alone even when the nozzle is left in an open state, and thus have excellent decap characteristics, as they are called. [Industrial Applicability]

[0152] According to the present invention, the ink is excellent in color development, hiding power, and decap characteristics, and is therefore suitable as an alcohol-based ink for inkjet recording. The ink for inkjet recording of the present invention uses aluminum lake pigment A, which is highly safe, and can be used in the food industry, medical industry, and cosmetics for skin, hair, nails, etc.

Claims

1. An alcohol-based ink for inkjet recording, comprising: an aluminum lake pigment (A); a pigment dispersant (B); an alcohol (C); a solvent (D); and a polymer (E); 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, the alcohol C is at least one selected from the group consisting of ethanol, n-propanol, and isopropanol; The boiling point of the solvent D is 150°C or higher, and the distance Ra of the Hansen solubility parameter of the solvent D in water represented by the following formula (I) is 40 or higher, The alcohol-based ink for ink-jet recording, wherein the solvent D is compatible with the alcohol C, and the polymer E is soluble in the alcohol C but insoluble in the solvent D. Ra=(4×ΔD 2 +ΔP 2 +ΔH 2 ) 0.5 (I) ΔD: Difference in dispersion component in Hansen solubility parameter between solvent D and water ΔP: Difference in polar component in Hansen solubility parameter between solvent D and water ΔH: Difference in hydrogen bond component in Hansen solubility parameter between solvent D and water

2. The alcohol-based ink for ink-jet recording according to claim 1, further comprising water in an amount of 7% by mass or more and 50% by mass or less.

3. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the content of alcohol C is 30% by mass or more and 70% by mass or less.

4. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the content of the solvent D in the alcohol-based ink for ink-jet recording is 7% by mass or more and 33% by mass or less.

5. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the content of solvents having a boiling point of 200[deg.] C. or higher in solvent D is 0.5% by mass or less.

6. 2. The alcohol-based ink for inkjet recording according to claim 1, wherein the total content of the high-boiling-point water-soluble organic solvent G other than the alcohol C and the solvent D, which is a water-soluble organic solvent having a boiling point of 200°C or higher, and the surfactant H in the alcohol-based ink for inkjet recording is 0.5% by mass or less.

7. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the aluminum lake pigment A is at least one selected from the group consisting of Yellow No. 4 Aluminum Lake, Yellow No. 5 Aluminum Lake, Blue No. 1 Aluminum Lake, and Red No. 104-(1) Aluminum Lake.

8. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the content of the aluminum lake pigment A is 0.8% by mass or more.

9. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the hydrophilic nonionic monomer (b-2) is an alkoxypolyethylene glycol mono(meth)acrylate.

10. 2. The alcohol-based ink for inkjet recording according to claim 1, wherein the mass ratio of the content of the 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.

11. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the pigment dispersant B has an acid value of 25 mgKOH / g or more and 400 mgKOH / g or less.

12. 2. The alcohol-based ink for ink-jet recording according to claim 1, wherein the degree of neutralization of the anionic groups of the pigment dispersant B is from 0 mol % to 50 mol %.

13. An inkjet recording method comprising ejecting the alcohol-based ink for inkjet recording according to any one of claims 1 to 12 onto a recording medium to form a printed coating film.