Inkjet ink composition and ink set

Abstract

To provide an ink jet ink composition with reduced generation of foreign materials derived from a pigment.SOLUTION: An ink jet ink composition includes: an acetoacetanilide-based monoazo pigment coated with a water-insoluble polymer; 1-(2-hydroxyethyl)-2-pyrrolidone; and water.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an inkjet ink composition and an ink set.

Background Art

[0002] Since the inkjet method can form high-quality images on a recording medium, various technical developments have been carried out conventionally. Not only the development of inkjet recording devices but also the study of making the ink composition used for this better has been widely conducted.

[0003] For example, foreign substances may occur in the ink composition, and studies have been made to suppress this. In Patent Document 1, in order to suppress foreign substances derived from a specific pigment in the ink, an attempt has been made to coexist a specific monoazo dye in the ink.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method described in Patent Document 1, elution of the causative substance of foreign substances from a specific colorant is not suppressed, and the generation of foreign substances cannot necessarily be said to be sufficiently suppressed.

Means for Solving the Problems

[0006] One aspect of the inkjet ink composition according to the present invention is an anilide acetoacetate monoazo pigment coated with a water-insoluble polymer, 1-(2-hydroxyethyl)-2-pyrrolidone, water, and contains.

[0007] One aspect of the ink set according to the present invention is the above-described inkjet ink composition, and a magenta ink composition containing a magenta pigment coated with a water-insoluble polymer, and a cyan ink composition containing a cyan pigment coated with a water-insoluble polymer, and includes.

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] Embodiments of the present invention will be described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited to the following embodiments, and various modified forms implemented within the scope of not changing the gist of the present invention are also included. Note that not all of the configurations described below are essential configurations of the present invention.

[0009] In this specification, “(meth)acryl” represents acrylic or methacrylic, and “(meth)acrylate” represents acrylate or methacrylate.

[0010] 1. Inkjet Ink Composition The inkjet ink composition according to the present embodiment contains an acetoacetic acid anilide-based monoazo pigment coated with a water-insoluble polymer, 1-(2-hydroxyethyl)-2-pyrrolidone, and water.

[0011] 1.1. Acetoacetic Acid Anilide-Based Monoazo Pigment The inkjet ink composition of the present embodiment contains an acetoacetic acid anilide-based monoazo pigment. The acetoacetic acid anilide-based monoazo pigment generally exhibits a yellow color and has relatively excellent light resistance and solvent resistance. Examples of the acetoacetic acid anilide-based monoazo pigment are listed in Table 1 below showing the general formula (I) and each substituent.

[0012]

Table 1

[0013] Acetoacetic acid anilide-based monoazo pigments are generally synthesized by diazotizing aromatic primary amines and performing a coupling reaction with acetoacetic acid anilide. At this time, the inventors have found that impurities in acetoacetic acid anilide react with diazo compounds in the system to generate foreign substances.

[0014] Among the above-exemplified acetoacetic acid anilide-based monoazo pigments, C.I. Pigment Yellow 1 and C.I. Pigment Yellow 74 are preferred in terms of better color development and lightfastness. On the other hand, although C.I. Pigment Yellow 1 and C.I. Pigment Yellow 74 may generate foreign substances, the inkjet ink composition of the present embodiment coats such pigments with a water-insoluble polymer and further contains 1-(2-hydroxyethyl)-2-pyrrolidone described later, so the generation of foreign substances can be sufficiently suppressed.

[0015] 1.2. Water-insoluble polymer The acetoacetic acid anilide-based monoazo pigments contained in the inkjet ink composition of the present embodiment are coated with a water-insoluble polymer. The water-insoluble polymer is not particularly limited, and examples thereof include those containing a basic group-containing monomer unit, a macromer unit, and / or a hydrophobic monomer unit. Further, the water-insoluble polymer may contain a hydroxyl group-containing monomer unit and other monomer units as necessary. Each unit will be described below.

[0016] (Basic group-containing monomer) The basic group-containing monomer is not particularly limited, and examples thereof include cationic monomers and anionic monomers. Examples thereof include those described in JP-A-9-286939, pages 5, column 7, line 24 to column 8, line 29. Here, the basic group is not particularly limited, and examples thereof include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group.

[0017] The cationic monomer is not particularly limited, and examples thereof include unsaturated amine-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate, N-(N’,N’-dimethylaminopropyl)(meth)acrylamide, and vinylpyrrolidone, and unsaturated ammonium salt-containing monomers.

[0018] The anionic monomer is not particularly limited, and examples thereof include unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid; unsaturated sulfonic acid monomers such as styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3-sulfopropyl (meth)acrylate, and bis-(3-sulfopropyl)-itaconic acid ester; and unsaturated phosphoric acid monomers such as vinylphosphonic acid, vinyl phosphate, bis(methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, and dibutyl-2-acryloyloxyethyl phosphate. Among the above anionic monomers, unsaturated carboxylic acid monomers are preferred from the viewpoints of dispersion stability and ejection stability, and acrylic acid and methacrylic acid are more preferred.

[0019] From the viewpoint of the dispersion stability of the resulting dispersion, the content of the basic group-containing monomer unit is preferably 2 to 40% by mass, more preferably 2 to 30% by mass, and particularly preferably 3 to 20% by mass based on the total amount of the water-insoluble polymer.

[0020] (Macromer) The macromer is not particularly limited, and examples thereof include styrene-based macromers and aromatic group-containing (meth)acrylate-based macromers having a polymerizable functional group at one end.

[0021] The number average molecular weight of the macromer is preferably from 500 to 100,000, more preferably from 1,000 to 10,000. The number average molecular weight of the macromer is measured by gel permeation chromatography using chloroform containing 1 mmol / L of dodecyl dimethylamine as a solvent and polystyrene as a standard substance.

[0022] The styrenic macromer is not particularly limited, and examples thereof include a styrenic monomer homopolymer or a copolymer of a styrenic monomer and another monomer. Examples of the styrenic monomer include styrene, 2-methylstyrene, vinyltoluene, ethylvinylbenzene, vinylnaphthalene, and chlorostyrene.

[0023] The aromatic group-containing (meth)acrylate-based macromer is not particularly limited, and examples thereof include a homopolymer of an aromatic group-containing (meth)acrylate or a copolymer thereof with another monomer. Examples of the aromatic group-containing (meth)acrylate include an arylalkyl group having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, which may have a substituent containing a heteroatom, or a (meth)acrylate having an aryl group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a substituent containing a heteroatom. Examples of the substituent containing a heteroatom include a halogen atom, an ester group, an ether group, and a hydroxy group. Specific examples of such monomers include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and benzyl (meth)acrylate is particularly preferred.

[0024] The polymerizable functional group present at one end of these macromers is not particularly limited, and for example, an acryloyloxy group or a methacryloyloxy group is preferred.

[0025] ​As the styrene monomer or another monomer copolymerized with an aromatic group-containing (meth)acrylate, acrylonitrile is preferred.

[0026] Commercially available styrene macromers are not particularly limited. Examples include products named AS-6(S), AN-6(S), and HS-6(S) from Toagosei Co., Ltd.

[0027] From the viewpoint of particularly enhancing the interaction with the colorant, the content of the macromer unit is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, based on the total amount of the water-insoluble polymer.

[0028] (Hydrophobic monomer) The hydrophobic monomer is not particularly limited. Examples include alkyl (meth)acrylates and aromatic group-containing monomers.

[0029] The alkyl (meth)acrylate is not particularly limited. For example, those having an alkyl group with 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms, are preferred. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate, (iso or tertiary)butyl (meth)acrylate, (iso)amyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl (meth)acrylate, (iso)dodecyl (meth)acrylate, and (iso)stearyl (meth)acrylate can be mentioned.

[0030] As the aromatic group-containing monomer, a vinyl monomer having an aromatic group with 6 to 22 carbon atoms, preferably 6 to 12 carbon atoms, which may have a substituent containing a heteroatom, is preferred. Specifically, the same styrene monomers and aromatic group-containing (meth )acrylates as those described for the macromer can be mentioned. The substituent containing a heteroatom is not particularly limited. Examples include a halogen atom, an ester group, an ether group, and a hydroxy group.

[0031] The content of the hydrophobic monomer unit is preferably 5 to 98% by mass, more preferably 10 to 60% by mass, based on the total amount of the water-insoluble polymer, from the viewpoints of glossiness and imageability.

[0032] (Hydroxyl group-containing monomer) The hydroxyl group-containing monomer is not particularly limited, and examples thereof include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, polyethylene glycol (meth)acrylate (n = 2 to 30, where n represents the average number of added moles of the oxyalkylene group; the same applies hereinafter), polypropylene glycol (meth)acrylate (n = 2 to 30), and poly(ethylene glycol·propylene glycol) (meth)acrylate (oxyethylene group: n = 1 to 15, oxypropylene group: n = 1 to 15). Among these, 2-hydroxyethyl (meth)acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferred.

[0033] The content of the hydroxyl group-containing monomer unit is preferably 5 to 40% by mass, more preferably 7 to 20% by mass, based on the total amount of the water-insoluble polymer, from the viewpoint of the dispersion stability of the resulting dispersion.

[0034] (Other monomers) Other monomers are not particularly limited, and examples thereof include compounds represented by the following formula. CH2=C(R 1 )COO(R 2 O) p R 3 (In the formula, R 1 is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R 2 is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, R 3 is a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, p means the average number of added moles and represents a number from 1 to 60, preferably a number from 1 to 30.)

[0035] In the above formula, examples of the heteroatom include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom. R 1 Preferred examples of include a methyl group, an ethyl group, and an (iso)propyl group. Also, R 2 Preferred examples of the O group include an oxyethylene group, an oxy(iso)propylene group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, and an oxyalkylene group having 2 to 7 carbon atoms composed of a combination of two or more of these oxyalkylenes. Further, R 3 Preferred examples of include an aliphatic alkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, and an alkyl group having 4 to 30 carbon atoms having a heterocyclic ring.

[0036] The above-mentioned other monomers are not particularly limited. For example, methoxypolyethylene glycol (meth)acrylate (1 to 30: represents the value of p in the above formula; the same applies hereinafter), methoxypolytetramethylene glycol (meth)acrylate (1 to 30), ethoxypolyethylene glycol (meth)acrylate (1 to 30), octoxypolyethylene glycol (meth)acrylate (1 to 30), polyethylene glycol (meth)acrylate 2-ethylhexyl ether (1 to 30), (iso)propoxypolyethylene glycol (meth)acrylate (1 to 30), butoxypolyethylene glycol (meth)acrylate (1 to 30), methoxypolypropylene glycol (meth)acrylate (1 to 30), methoxy(ethylene glycol·propylene glycol)(meth)acrylate (1 to 30, ethylene glycol therein: 1 to 29). Among these, octoxypolyethylene glycol (meth)acrylate (1 to 30) and polyethylene glycol acrylate 2-ethylhexyl ether (1 to 30) are preferred.

[0037] Commercially available hydroxyl group-containing monomers and other monomers include polyfunctional acrylate monomers (NK esters) M-40G, 90G, and 230G from Shin-Nakamura Chemical Co., Ltd., and Brenmer series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800, 50PEP-300, and 50POEP-800B from NOF Corporation.

[0038] From the viewpoint of the dispersion stability of the resulting dispersion, the content of other monomer units is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, based on the total amount of the water-insoluble polymer.

[0039] From the viewpoints of glossiness and imageability, the mass ratio of the basic group-containing monomer unit to the macromer unit and the hydrophobic monomer unit (content of the basic group-containing monomer unit / (content of the macromer unit + content of the hydrophobic monomer unit)) is preferably 0.01 to 1, more preferably 0.02 to 0.67, and still more preferably 0.03 to 0.50.

[0040] From the viewpoint of the dispersion stability of the resulting dispersion, the total content of the basic group-containing monomer unit and the hydroxyl group-containing monomer unit is preferably 6 to 60% by mass, more preferably 10 to 50% by mass, based on the total amount of the water-insoluble polymer.

[0041] From the viewpoint of the dispersion stability of the resulting dispersion, the total content of the basic group-containing monomer unit and the other monomer units is preferably 6 to 75% by mass, more preferably 13 to 50% by mass, based on the total amount of the water-insoluble polymer.

[0042] From the viewpoint of the dispersion stability of the resulting dispersion, the total content of the basic group-containing monomer unit, the hydroxyl group-containing monomer unit, and the other monomer units is preferably 6 to 60% by mass, more preferably 13 to 50% by mass, based on the total amount of the water-insoluble polymer.

[0043] The method for producing the water-insoluble polymer is not particularly limited, and examples thereof include the method described in JP-A-2009-172971.

[0044] The ink composition of the present embodiment contains an acetoacetic acid anilide-based monoazo pigment coated with a water-insoluble polymer, thereby suppressing the generation of foreign matters, and further improving the printing density and glossiness of the obtained recording material. "Coated" means that a water-insoluble polymer adheres to at least a part of the particle surface of the acetoacetic acid anilide-based monoazo pigment.

[0045] The content of the acetoacetic acid anilide-based monoazo pigment coated with a water-insoluble polymer is preferably 0.5% by mass or more and 12.5% by mass or less, more preferably 1.0% by mass or more and 10% by mass or less, and still more preferably 2.5% by mass or more and 7.5% by mass or less with respect to the total amount of the ink composition. When the content of the acetoacetic acid anilide-based monoazo pigment coated with a water-insoluble polymer is 0.5% by mass or more, the generation of foreign matters derived from the acetoacetic acid anilide-based monoazo pigment coated with a water-insoluble polymer tends to be more suppressed. Further, when the content of the acetoacetic acid anilide-based monoazo pigment coated with a water-insoluble polymer is 12.5% by mass or less, the printing density and glossiness of the obtained recording material tend to be further improved.

[0046] 1.3. 1-(2-Hydroxyethyl)-2-pyrrolidone The inkjet ink composition according to the present embodiment contains 1-(2-hydroxyethyl)-2 -pyrrolidone. 1-(2-Hydroxyethyl)-2-pyrrolidone is also called N-hydroxyethylpyrrolidone, 1-(2-hydroxyethyl)pyrrolidin-2-one, etc. (In this specification, it may be abbreviated as "HEP".).

[0047] By containing HEP in the inkjet ink composition, it is possible to suppress the isomerization of substances derived from acetoacetic acid anilide-based monoazo pigments. Further, by containing HEP in the inkjet ink composition, even when substances derived from acetoacetic acid anilide-based monoazo pigments are isomerized, they can be quickly dissolved.

[0048] Furthermore, by containing HEP in the inkjet ink composition, it is possible to suppress the inhibitory action of 1,2-alkanediols and the like, which tend to inhibit the dispersibility of substances in a dispersed state. The inventors consider that such an effect is caused in part by the property of HEP to complement the hydrophobic-hydrophilic interface between 1,2-alkanediols with relatively strong hydrophobicity and water, polyhydric alcohols, organic solvents, etc. with relatively weak hydrophobicity or high hydrophilicity.

[0049] HEP has amphiphilic properties, but compared with surfactants, it does not have a structure in which the hydrophilic part and the hydrophobic part are clearly separated. Therefore, for example, it is difficult to destabilize the dispersed state of substances in a dispersed state in an inkjet ink composition such as pigments and resin particles. Therefore, HEP also has the property of being less likely to aggregate substances in a dispersed state in an inkjet ink composition among amphiphilic surfactants and organic solvents.

[0050] The content of HEP is preferably 0.5% by mass or more and 30.0% by mass or less, more preferably 1.0% by mass or more and 20.0% by mass or less, and even more preferably 2.0% by mass or more and 10.0% by mass or less with respect to the total amount of the inkjet ink composition.

[0051] 1.4. Water The inkjet ink composition according to this embodiment contains water. Examples of the water include pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, and distilled water, and those with reduced ionic impurities such as ultrapure water. Further, when using water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, etc., the generation of bacteria and fungi can be suppressed when the inkjet ink composition is stored for a long time.

[0052] The water content is 30% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, and still more preferably 50% by mass or more with respect to the total amount of the inkjet ink composition. When referring to water in the inkjet ink composition, for example, it includes the water contained in the raw materials and the added water. By the water content being 30% by mass or more, the inkjet ink composition can have a relatively low viscosity. Also, the upper limit of the water content is preferably 90% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less with respect to the total amount of the inkjet ink composition.

[0053] 1.5. Other Components 1.5.1. Humectant The inkjet ink composition may further contain a humectant. When the inkjet ink composition contains a humectant, the volatilization of moisture can be suppressed, and for example, the storage stability can be further improved.

[0054] Examples of the humectant can include alkyl polyols. Alkyl polyols have multiple Alcohols and 1,2 - alkanediols are conceptually included. While 1,2 - alkanediols have moisturizing properties, they also have the property of being a penetrant that improves the penetration of the inkjet ink composition into the recording medium. When an alkyl polyol is included, the moisturizing property of the inkjet ink composition can be further enhanced, the ejection stability by the inkjet method can be made excellent, and the evaporation of moisture from the recording head during long - term storage can be effectively suppressed. Also, thereby, even when a coloring material that is likely to cause nozzle clogging is used, the recovery property after standing and the continuous ejection stability can be maintained better.

[0055] Specific examples of the alkyl polyol include 1,3 - propanediol, 1,3 - butanediol, 1,4 - butanediol, 1,5 - pentanediol, 1,6 - hexanediol, 2 - ethyl - 2 - methyl - 1,3 - propanediol, 2 - methyl - 2 - propyl - 1,3 - propanediol, 2 - methyl - 1,3 - propanediol, 2,2 - dimethyl - 1,3 - propanediol, 3 - methyl - 1,3 - butanediol, 2 - ethyl - 1,3 - hexanediol, 3 - methyl - 1,5 - pentanediol, 2 - methylpentane - 2,4 - diol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, triethylene glycol, tetraethylene glycol, etc. These alkyl polyols may be used alone or in combination of two or more.

[0056] 1,2-Alkanediol is a general term for compounds in which hydroxyl groups are substituted at the 1- and 2-positions of an alkane. Examples of 1,2-alkanediol include ethylene glycol, propane-1,2-diol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 3-methyl-1,2-butanediol, 3-methyl-1,2-pentanediol, 4-methyl-1,2-pentanediol, 3,4-dimethyl-1,2-pentanediol, 3-ethyl-1,2-pentanediol, 4-ethyl-1,2-pentanediol, 3-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, 5-methyl-1,2-hexanediol, 3,4-dimethyl-1,2-hexanediol, 3,5-dimethyl-1,2-hexanediol, 4,5-dimethyl-1,2-hexanediol, 3-ethyl-1,2-hexanediol, 4-ethyl-1,2-hexanediol, 3-ethyl-4-methyl-1,2-hexanediol, and the like.

[0057] 1.5.2. Plasticizer The inkjet ink composition may further contain a plasticizer. When the inkjet ink composition contains a plasticizer, the flexibility of the water-insoluble polymer can be increased when it adheres to and dries on the recording medium, and the glossiness and printing density of the resulting recorded matter tend to be further improved.

[0058] The plasticizer is not particularly limited, and examples thereof include aliphatic carboxylic acid esters, aromatic carboxylic acid esters, phosphate esters, cycloalkane (ene) carboxylic acid esters, oxyacid esters, glycol esters, epoxy-based esters, sulfonamides, polyesters, glyceryl alkyl ethers, glyceryl alkyl esters, glycol alkyl ethers, glycol alkyl esters, ethers or esters of trimethylolpropane, and ethers or esters of pentaerythritol. Among these, aliphatic carboxylic acid esters such as dibutyl sebacate (dibutyl sebacate) are preferred.

[0059] The content of the plasticizer is preferably 0.01% by mass or more and 1.0% by mass or less, more preferably 0.05% by mass or more and 0.7% by mass or less, and still more preferably 0.1% by mass or more and 0.5% by mass or less with respect to the total amount of the inkjet ink composition. The content of the plasticizer being within this range tends to further improve the glossiness of the resulting recording.

[0060] If the inkjet ink composition contains a plasticizer, the water-insoluble polymer can be plasticized, so that the film-forming property of the water-insoluble polymer adhered to the recording medium can be enhanced. Thereby, an image with better gloss can be formed.

[0061] 1.5.3. Organic Solvent The inkjet ink composition may contain an organic solvent other than those described above. Main examples of such organic solvents include glycol ethers, cyclic amides, and the like.

[0062] 1.5.3.1. Glycol Ether The inkjet ink composition of the present embodiment may contain a glycol ether. Examples of the glycol ether include monoalkyl ethers or dialkyl ethers of glycols selected from ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene glycol. More specifically, methyl triglycol (triethylene glycol monomethyl ether), butyl triglycol (triethylene glycol monobutyl ether), butyl diglycol (diethylene glycol monobutyl ether), dipropylene glycol monopropyl ether, and the like can be mentioned, and diethylene glycol monobutyl ether is mentioned as a typical example.

[0063] The inkjet ink composition may contain one or more selected from glycol ethers represented by the following formula (1). R 1 -O-(CH2-CH2-O) n -R 2 ···(1) (In formula (1), R 1 represents H or an alkyl group having 1 to 4 carbon atoms, R 2 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 2 or more and 3 or less.)

[0064] Examples of the glycol ether represented by formula (1) include methyl triglycol (triethylene glycol monomethyl ether), butyl triglycol (triethylene glycol monobutyl ether), butyl diglycol (diethylene glycol monobutyl ether), triethylene glycol dimethyl ether, triethylene glycol dibutyl ether, diethylene glycol dibutyl ether, and the like.

[0065] A plurality of glycol ethers may be mixed and used. When using a glycol ether, the blending amount is 0.5% by mass or more and 30% by mass or less, preferably 1.0% by mass or more and 20% by mass or less, more preferably 3.0% by mass or more and 10.0% by mass or less, in total with respect to the total amount of the inkjet ink composition, from the viewpoints of viscosity adjustment of the inkjet ink composition and clogging prevention by the moisturizing effect.

[0066] 1.5.3.2. Cyclic amide The inkjet ink composition of this embodiment may contain a cyclic amide. Examples of the cyclic amide include compounds having a ring structure containing an amide group. Such compounds include γ-lactams such as 2-pyrrolidone, 1-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone), 1-ethyl-2-pyrrolidone (N-ethyl-2-pyrrolidone), 1-propyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, N-vinyl-2-pyrrolidone (NVP), β-lactams, δ-lactams, and ε-lactams such as ε-caprolactam. These cyclic amides may be used alone or in combination of two or more.

[0067] 1.5.3.3. Other Organic Solvents The inkjet ink composition of this embodiment may contain other organic solvents. Examples of other organic solvents include lactones such as γ-butyrolactone and betaine compounds.

[0068] The content of the organic solvent is preferably 0.2% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and still more preferably 1.0% by mass or more and 10% by mass or less based on the total amount of the ink composition.

[0069] 1.5.4. Surfactant The inkjet ink composition may contain a surfactant. The surfactant is not particularly limited, and examples thereof include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0070] Although not particularly limited, examples of the acetylene glycol - based surfactant include, for example, 2,4,7,9 - tetramethyl - 5 - decyne - 4,7 - diol and alkylene oxide adducts of 2,4,7,9 - tetramethyl - 5 - decyne - 4,7 - diol, and one or more selected from 2,4 - dimethyl - 5 - decyne - 4 - ol and alkylene oxide adducts of 2,4 - dimethyl - 5 - decyne - 4 - ol are preferred. Although not particularly limited, examples of commercially available products of acetylene glycol - based surfactants include, for example, the Orfin 104 series and the E series of Orfin E1010 (trade names of products manufactured by Air Products Japan, Inc.), Surfynol 465, Surfynol 61 (trade names of products manufactured by Nissin Chemical Industry CO., Ltd.), and the like. The acetylene glycol - based surfactant may be used alone or in combination of two or more kinds.

[0071] Although not particularly limited, examples of the fluorine - based surfactant include, for example, perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds. Although not particularly limited, examples of commercially available products of fluorine - based surfactants include, for example, S - 144, S - 145 (manufactured by Asahi Glass Co., Ltd.); FC - 170C, FC - 430, Fluorad - FC4430 (manufactured by Sumitomo 3M Limited); FSO, FSO - 100, FSN, FSN - 100, FS - 300 (manufactured by Dupont); FT - 250, 251 (manufactured by Neos Co., Ltd.), and the like. The fluorine - based surfactant may be used alone or in combination of two or more kinds.

[0072] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes. Commercially available silicone surfactants are not particularly limited, but specifically include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (trade names above, manufactured by BYK Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (trade names above, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0073] The content of the surfactant is preferably 0.10% by mass or more and 1.5% by mass or less, more preferably 0.1% by mass or more and 1.25% by mass or less, and still more preferably 0.25% by mass or more and 1.0% by mass or less with respect to the total amount of the ink composition. When the content of the surfactant is within the above range, the glossiness tends to be further improved.

[0074] 1.5.5. Resin Particles The inkjet ink composition may contain resin particles. The resin particles can further improve the adhesion of the image formed by the inkjet ink composition adhered to the recording medium. When the inkjet ink composition further contains resin particles, for example, the abrasion resistance of the obtained image can be improved.

[0075] Examples of the resin particles include resin particles composed of urethane resins, acrylic resins (including styrene-acrylic resins), fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate resins, etc. Among them, urethane resins, acrylic resins, polyolefin resins, and polyester resins are preferred. These resin particles are often handled in the form of an emulsion, but may also be in the form of a powder. The resin particles can be used alone or in combination of two or more.

[0076] Urethane resins are a general term for resins having urethane bonds. In addition to urethane bonds, polyether-type urethane resins containing ether bonds in the main chain, polyester-type urethane resins containing ester bonds in the main chain, polycarbonate-type urethane resins containing carbonate bonds in the main chain, etc. may be used for urethane resins. Also, commercially available products may be used as urethane resins. For example, commercially available products such as Superflex 460, 460s, 840, E-4000 (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Resamin D-1060, D-2020, D-4080, D-4200, D-6300, D-6455 (trade name, manufactured by Dainichi Seiko Kogyo Co., Ltd.), Takelac WS-5100, WS-6021, W-512-A-6 (trade name, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.), Suncure 2710 (trade name, manufactured by Lubrizol), Permalin UA-150 (trade name, manufactured by Sanyo Chemical Industries, Ltd.) may be used.

[0077] Acrylic resins are a general term for polymers obtained by polymerizing at least one acrylic monomer such as (meth)acrylic acid and (meth)acrylic acid ester. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers and other monomers. For example, acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers, can be mentioned. Also, for example, styrene can be mentioned as a vinyl monomer.

[0078] As acrylic monomers, acrylamide, acrylonitrile, etc. can also be used. For the resin emulsion made from acrylic resin, commercially available products may be used. For example, it may be selected from and used, such as FK-854 (trade name, manufactured by Central Research Chemical Industry Co., Ltd.), Mobinyl 952B, 718A (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Nipol LX852, LX874 (trade name, manufactured by Zeon Corporation of Japan), etc.

[0079] Styrene-acrylic resin is a copolymer obtained from styrene monomer and (meth)acrylic monomer, and examples include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, etc. For styrene-acrylic resin, commercially available products may be used. For example, Joncryl 62J, 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (trade name, manufactured by BASF), Mobinyl 966A, 975N (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Vinibran 2586 (manufactured by Nisshin Chemical Industry Co., Ltd.), etc. may be used.

[0080] Polyolefin resin has olefins such as ethylene, propylene, butylene, etc. in its structural skeleton, and known ones can be appropriately selected and used. As the olefin resin, commercially available products can be used. For example, Arrow Base CB-1200, CD-1200 (trade name, manufactured by Unitika Ltd.), etc. may be used.

[0081] Also, the resin particles may be supplied in the form of an emulsion. Examples of commercially available products of such resin emulsions include Microgel E-1002, E-5002 (trade names of products manufactured by Nippon Paint Co., Ltd., styrene-acrylic resin emulsions), Boncoat 4001 (trade name of a product manufactured by DIC Corporation, acrylic resin emulsion), Boncoat 5454 (trade name of a product manufactured by DIC Corporation, styrene-acrylic resin emulsion), Polyzol AM-710, AM-920, AM-2300, AP-4735, AT-860, PSASE-4210E (acrylic resin emulsion), Polyzol AP-7020 (styrene-acrylic resin emulsion), Polyzol SH-502 (vinyl acetate resin emulsion), Polyzol AD-13, AD-2, AD-10, AD-96, AD-17, AD-70 (ethylene-vinyl acetate resin emulsion), Polyzol PSASE-6010 (ethylene-vinyl acetate resin emulsion) (trade name of a product manufactured by Showa Denko K.K.), Polyzol SAE1014 (trade name, styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (trade name, acrylic resin emulsion, manufactured by Saiden Chemical Co., Ltd.), AE-120A (trade name of a product manufactured by JSR Corporation, acrylic resin emulsion), AE373D (trade name of a product manufactured by E-Tech Co., Ltd., carboxy-modified styrene-acrylic resin emulsion), Seikadine 1900W (trade name of a product manufactured by Dainichi Seika Kogyo Co., Ltd., ethylene-vinyl acetate resin emulsion), Vinibran 2682 (acrylic resin emulsion), Vinibran 2886 (vinyl acetate-acrylic resin emulsion), Vinibran 5202 (acrylic acetate resin emulsion) (trade names of products manufactured by Nissin Chemical Industry Co., Ltd.), Elitel KA-5071S, KT-8803, KT-9204, KT-8701, KT-8904, KT-0507 (trade names of products manufactured by Unitika Ltd., polyester resin emulsion), Hi-Tech SN-2002 (trade name of a product manufactured by Toho Chemical Co., Ltd., polyester resin emulsion), Takelac W-6020, W-635, W-6061, W-605, W-635, W-6021 (trade names of products manufactured by Mitsui Chemicals Polyurethane Co., Ltd., urethane resin emulsion), Superflex 870, 800, 150, 420, 460, 470, 610, 700 (trade names of products manufactured by Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion), Permalin UA-150 (manufactured by Sanyo Chemical Industries, Ltd.,Urethane resin emulsion), Sanki-cure 2710 (manufactured by Nippon Lubrizol Corporation, urethane resin emulsion), NeoRez R-9660, R-9637, R-940 (manufactured by Kusumoto Chemical Co., Ltd., urethane resin emulsion), Adeka Bon Titer HUX-380, 290K (manufactured by ADEKA Corporation, urethane resin emulsion), Mobinyl 966A, Mobinyl 7320 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Joncryl 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (manufactured by BASF), NK Binder R-5HN (manufactured by Shin-Nakamura Chemical Co., Ltd.), Hydran WLS-210 (non-crosslinked polyurethane: manufactured by DIC Corporation), Joncryl 7610 (manufactured by BASF), etc. can be mentioned.

[0082] When the resin particles are contained in the inkjet ink composition, the content is 0.1% by mass or more and 20% by mass or less, preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less, as a solid content based on the total mass of the inkjet ink composition.

[0083] 1.5.6. Other components The inkjet ink composition may contain additives that can be usually used in an inkjet ink composition for inkjet, such as a chelating agent, a pH adjuster, ureas, a preservative, a fungicide, a rust preventive, saccharides, an antioxidant, an ultraviolet absorber, an oxygen absorber, a dissolution aid, a viscosity adjuster, etc. In addition, it is more preferable from the viewpoint of safety that the inkjet ink composition of the present embodiment is an aqueous ink composition containing the most water in the volatile components. The inkjet ink composition may contain additives that can be usually used in an inkjet ink composition for inkjet, such as a chelating agent, a pH adjuster, ureas, a preservative, a fungicide, a rust preventive, saccharides, an antioxidant, an ultraviolet absorber, an oxygen absorber, a dissolution aid, a viscosity adjuster, etc. In addition, it is more preferable from the viewpoint of safety that the inkjet ink composition of the present embodiment is an aqueous ink composition containing the most water in the volatile components.

[0084] 1.6. Action and effect According to this inkjet ink composition, since the acetoacetic acid anilide-based monoazo pigment is coated with a water-insoluble polymer, elution of causative substances of foreign matter is suppressed. Moreover, by containing 1-(2-hydroxyethyl)-2-pyrrolidone, it is possible to suppress the causative substances from becoming foreign matter. As a result, the inkjet ink composition can suppress the generation of foreign matter even in situations where foreign matter is likely to occur, such as during long-term storage. Further, according to this inkjet ink composition, since an acetoacetic acid anilide-based monoazo pigment is used, an image with good color development can be formed. Furthermore, according to this inkjet ink composition, since the acetoacetic acid anilide-based monoazo pigment is coated with a water-insoluble polymer, an image with good gloss can be formed.

[0085] 2. Ink set The ink set according to this embodiment includes the above-described inkjet ink composition, a magenta ink composition containing a magenta pigment coated with a water-insoluble polymer, and a cyan ink composition containing a cyan pigment coated with a water-insoluble polymer.

[0086] 2.1. Water-insoluble polymer The water-insoluble polymer that coats the magenta pigment contained in the magenta ink composition and the cyan pigment contained in the cyan ink composition is the same as the water-insoluble polymer that coats the above-described acetoacetic acid anilide-based monoazo pigment, so detailed description thereof is omitted. Since the magenta ink composition and the cyan ink composition contain pigments coated with a water-insoluble polymer, it is easy to form an image with good color development and gloss when attached to a recording medium.

[0087] 2.2. Magenta ink composition The magenta ink composition contains a magenta pigment. Further, the magenta ink composition may contain other components. For example, it may contain 1-(2-hydroxyethyl)-2-pyrrolidone, water, or the substances exemplified in the section of "1.5. Other components" above. Furthermore, the content of these substances is the same as described above.

[0088] Examples of magenta pigments include C.I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57:1, 112, 122, 123, 150, 168, 184, 202, C.I. Pigment Violet 19, etc. Preferably, one or more mixtures selected from the group consisting of C.I. Pigment Red 122, 150, 202, and 209, and C.I. Pigment Violet 19 can be exemplified.

[0089] As the pigment, those previously dispersed with a dispersant may be used. Examples of the dispersant include (meth)acrylic resins and their salts such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylate copolymer, vinyl acetate-(meth)acrylate copolymer, vinyl acetate-(meth)acrylic acid copolymer, vinyl naphthalene-(meth)acrylic acid copolymer, etc.; styrene resins and their salts such as styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylate copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer, styrene-α-methylstyrene-(meth)acrylic acid-(meth)acrylate copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, etc.; iso Examples of the polymer compound (resin) containing a urethane bond formed by the reaction of a cyanate group and a hydroxyl group can be given. These may be linear and / or branched, and include urethane resins and their salts regardless of the presence or absence of a crosslinked structure; polyvinyl alcohols; vinyl naphthalene-maleic acid copolymer and its salts; vinyl acetate-maleic acid ester copolymer and its salts; and water-soluble resins such as vinyl acetate-crotonic acid copolymer and its salts.

[0090] Examples of commercially available dispersants for styrene-acrylic resins include X-200, X-1, X-205, X-220, X-228 (manufactured by Starlight PMC Co., Ltd.), Nopco Spars (registered trademark) 6100, 6110 (manufactured by San Nopco Ltd.), Joncryl 67, 586, 611, 678, 680, 682, 819 (manufactured by BASF), DISPERBYK-190 (manufactured by BYK-Chemie Japan Co., Ltd.), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, E-EN10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and the like.

[0091] Examples of commercially available acrylic resin dispersants include BYK-187, BYK-190, BYK-191, BYK-194N, BYK-199 (manufactured by BYK-Chemie GmbH), Aron A-210, A6114, AS-1100, AS-1800, A-30SL, A-7250, CL-2 (manufactured by Toagosei Co., Ltd.), and the like.

[0092] Examples of commercially available urethane resin dispersants include BYK-182, BYK-183, BYK-184, BYK-185 (manufactured by BYK-Chemie GmbH), TEGO Disperse 710 (manufactured by Evonic Tego Chemi), Borchi (registered trademark) Gen1350 (manufactured by OMG Borschers), and the like.

[0093] The dispersant may be used alone or in combination of two or more. The total content of the dispersant is preferably 0.1 part by mass or more and 30 parts by mass or less, more preferably 0.5 part by mass or more and 25 parts by mass or less, still more preferably 1 part by mass or more and 20 parts by mass or less, and even more preferably 1.5 parts by mass or more and 15 parts by mass or less, based on 50 parts by mass of the pigment. When the content of the dispersant is 0.1 part by mass or more based on 50 parts by mass of the pigment, the dispersion stability of the pigment can be further enhanced. Also, when the content of the dispersant is 30 parts by mass or less based on 50 parts by mass of the pigment, the viscosity of the resulting dispersion can be more effectively suppressed.

[0094] Alternatively, the pigment may be dispersed and used as a self-dispersing pigment by oxidizing or sulfonating the pigment surface with ozone, hypochlorous acid, fuming sulfuric acid, etc.

[0095] 2.3. Cyan Ink Composition The cyan ink composition contains a cyan pigment. Further, the cyan ink composition may contain other components. For example, it may contain 1-(2-hydroxyethyl)-2-pyrrolidone, water, or may contain the substances exemplified in the section of "1.5. Other Components" described above. Furthermore, the content of these substances is the same as described above.

[0096] Examples of the cyan pigment include C.I.Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60, etc.; C.I.Vat Blue 4, 60, etc. Preferably, one or more mixtures selected from the group consisting of C.I.Pigment Blue 15:3, 15:4, and 60 can be exemplified.

[0097] Regarding the use of a pigment dispersant, making it a self-dispersing type pigment, etc., it is the same as the above-mentioned magenta ink composition.

[0098] 2.4. Other Ink Compositions The ink set of this embodiment may contain a plurality of the above-mentioned inkjet ink compositions, magenta ink compositions, and cyan ink compositions. Further, the ink set of this embodiment may contain an ink composition other than the above-mentioned inkjet ink compositions, magenta ink compositions, and cyan ink compositions. Examples of such ink compositions may include ink compositions such as black, blue, red, orange, white, fluorescent color, metallic color, etc. Among these, the black ink composition will be described below.

[0099] The ink set of this embodiment may include a black ink composition. The black ink composition contains a black pigment. Further, the black ink composition may contain other components. For example, it may contain 1-(2-hydroxyethyl)-2-pyrrolidone and water, or may contain the substances exemplified in the section of "1.5. Other Components" above. Furthermore, the content of these substances is the same as described above.

[0100] Furthermore, the black pigment contained in the black ink composition may also be coated with a water-insoluble polymer.

[0101] As the black pigment, carbon blacks (such as C.I.Pigment Black 7 etc.) such as furnace black, lamp black, acetylene black, channel black, etc., and iron oxide can be used.

[0102] Examples of carbon black include No.2300, 900, MCF88, No.20B, No.33, No.40, No.45, No.52, MA7, MA8, MA100, No2200B, etc. manufactured by Mitsubishi Chemical Corporation. Also, examples of carbon black include Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, Special Black 6, 5, 4A, 4, 250, etc. manufactured by Degussa. Also, examples of carbon black include Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, etc. manufactured by Columbian Carbon. Also, examples of carbon black include Regal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12, etc. manufactured by Cabot. Furthermore, examples of carbon black include BONJET BLACK CW-1, CW-1S, CW-2, CW-3, M-800, etc. manufactured by Orient Chemical Industries Co., Ltd.

[0103] Regarding the use of a pigment dispersant, making it a self-dispersing pigment, etc., it is the same as the above-described magenta ink composition. Here, for the black pigment, by making it a black ink composition containing this as a self-dispersing pigment, the solid content concentration of the pigment can be increased, and the black color developability can be enhanced.

[0104] The black ink composition may contain a (meth)acrylic resin having a glass transition temperature of 20°C or lower. Examples of the (meth)acrylic resin having a glass transition temperature of 20°C or lower include those among the above-described resin particles having a glass transition temperature of 20°C or lower. In this way, the flexibility of the (meth)acrylic resin is good, and when it adheres to the recording medium, film formation is easier, so that an image with better fixing properties can be formed. Note that the glass transition temperature (Tg) of the resin can be measured by a standard method using DSC.

[0105] 2.5. Embodiments of the Ink Compositions Contained in the Ink Set As described above, the ink set of the present embodiment arbitrarily includes a plurality of inkjet ink compositions, magenta ink compositions, magenta ink compositions, cyan ink compositions, and ink compositions such as black, blue, red, orange, white, fluorescent color, and metallic color. Among these ink compositions, it is preferable that not only the inkjet ink composition but also the magenta ink composition, cyan ink composition, and ink compositions such as black, blue, red, orange, white, fluorescent color, and metallic color contain 1-(2-hydroxyethyl)-2-pyrrolidone. That is, it is more preferable that the inkjet ink composition and one or more of the ink compositions other than the inkjet ink composition contain 1-(2-hydroxyethyl)-2-pyrrolidone.

[0106] By using such an ink set, the generation of foreign matters can be further suppressed in the waste liquid discharged by flushing or the like for the ink compositions other than the inkjet ink composition.

[0107] 2.6. Operational Effects According to this ink set, even in a situation where foreign matter is likely to occur, such as when storing for a long time in at least the inkjet ink composition, the generation of foreign matter can be suppressed.

[0108] 3. Examples and Comparative Examples Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" are based on mass unless otherwise specified.

[0109] 3.1. Production of Pigment Dispersion The following dispersions were produced. · Aqueous dispersion I: An aqueous dispersion of C.I.Pigment Yellow 74 coated with a water-insoluble polymer (see Production Example 1 below. Solid content concentration: 20% by mass) · Aqueous dispersion II: An aqueous dispersion of C.I.Pigment Yellow 1 coated with a water-insoluble polymer (see Production Example 2 below. Solid content concentration: 20% by mass) · Aqueous dispersion III: An aqueous dispersion of C.I.Pigment Yellow 74 not coated with a water-insoluble polymer (solid content concentration: 20% by mass)

[0110] 〔Production Example of Water-Insoluble Polymer〕 Into a reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% by mass of a total of 200 parts of the following monomers were put and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution. The unit of the numerical value of each monomer is mass%, and the total is 100.0 mass%.

[0111] Methacrylic acid 11 Styrene macromer 10 Styrene 39 Benzyl methacrylate 10 PP-800 30

[0112] Here, each material is as follows. Styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6(S), number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group) PP-800 (polypropylene glycol monomethacrylate (average number of added moles of propylene oxide = 13, terminal: hydroxy group): manufactured by NOF Corporation, trade name: Blemmer PP-800)

[0113] On the other hand, 90% by mass of the remaining amount of each monomer was charged into a dropping funnel, and 0.27 part of the above polymerization chain transfer agent, 60 parts of methyl ethyl ketone, and 1.2 parts of a radical polymerization initiator (2,2'-azobis(2,4-dimethylvaleronitrile)) were added and mixed, and sufficient nitrogen gas substitution was performed , and a mixed solution was obtained.

[0114] Under a nitrogen atmosphere, the temperature of the mixed solution in the reaction vessel was raised to 65 °C while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours had elapsed at 65 °C from the end of dropping, a solution obtained by dissolving 0.3 part of the above radical polymerization initiator in 5 parts of methyl ethyl ketone was added, and further aging was carried out at 65 °C for 2 hours and at 70 °C for 2 hours to obtain a polymer solution. The weight average molecular weight of the obtained polymer was 150,000.

[0115] [Production Example 1 of Aqueous Dispersion] 30 parts of the polymer obtained by subjecting the solution of the water-insoluble polymer obtained in the above production example to drying under reduced pressure was dissolved in 70 parts of methyl ethyl ketone, and a neutralizing agent (5N aqueous sodium hydroxide solution) in an amount such that the degree of neutralization was 60% and 230 parts of ion-exchanged water were added to neutralize the basic groups. Further, 65 parts of an acetoacetic acid anilide-based monoazo pigment (C.I. Pigment Yellow 74, manufactured by Sanyo Color Works Co., Ltd., trade name: FY7413) as a yellow pigment were added, and the mixture was mixed at a temperature of 20 °C for 1 hour using a dispersing blade. The obtained mixture was subjected to a dispersion treatment of 10 passes at a pressure of 200 MPa using a microfluidizer (trade name, manufactured by Microfluidics).

[0116] To the obtained dispersion, 250 parts of ion-exchanged water was added and stirred. After that, methyl ethyl ketone was removed at 60 °C under reduced pressure, and further a part of water was removed. Filtration was carried out using a 5-μm filter (acetyl cellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) attached to a 25-mL syringe without a needle (manufactured by Terumo Corporation) to remove coarse particles, thereby obtaining an aqueous dispersion I of C.I. Pigment Yellow 74 coated with a water-insoluble polymer having a solid content concentration of 20% by mass.

[0117] [Production Example 2 of Aqueous Dispersion] An aqueous dispersion II of C.I. Pigment Yellow 1 coated with a water-insoluble polymer having a solid content concentration of 20% by mass was obtained in the same manner as in Production Example 1 except that C.I. Pigment Yellow 1 was used.

[0118] [Production Example 3 of Aqueous Dispersion] A 4-L stainless steel beaker was attached to a rotor-stator type high-shear mixer (manufactured by Silverson, product name "L4RT-A") and immersed in an ice bath. About 75 g of C.I. Pigment Yellow 74 and 1000 g of water were placed in this beaker and homogenized at 7200 rpm for 15 minutes. To this, 20 mL of an isopropanol solution in which 2.07 g (0.01 mol) of o-acetanisidide was dissolved was added, and further stirred for 15 minutes.

[0119] In another container, 4.35 g (0.025 mol) of sulfanilic acid, 30 mL of 1N-HCl, and 1.73 g (0.025 mol) of sodium nitrite were mixed at 5 to 10 °C to form a diazonium salt. Then, this was added to the mixture of C.I. Pigment Yellow 74 and o-acetanisidide while stirring, and the temperature was maintained at about 10 °C. This mixture was adjusted to pH 5 to 6 by dropwise addition of a 5M sodium hydroxide solution, and further stirred for 2 hours while confirming the progress of the reaction by the presence or absence of the diazonium salt.

[0120] Transfer the mixture to a Telsonic flow-through ultrasonic processor and subject it to ultrasonic treatment for over 2 hours. After purifying the resulting pigment dispersion using a 50 nm diafiltration membrane column, concentrate it to a solid content of 20% to obtain an aqueous dispersion III of C.I. Pigment Yellow 74 that is not coated with a water-insoluble polymer.

[0121] 3.2. Preparation of Inkjet Ink Composition Mix each material in the composition shown in Table 2 below and stir well to obtain each ink composition. Specifically, each ink composition was prepared by uniformly mixing each material and removing insoluble matter with a filter. In the table, the unit of the numerical value is mass%, and the total is 100.0 mass%.

[0122]

Table 2

[0123] The abbreviations in Table 2 are as follows. ·DBS: Dibutyl Sebacate (plasticizer) ·HEP: 1-(2-Hydroxyethyl)-2-pyrrolidone ·TEGmBE: Triethylene Glycol Monobutyl Ether ·Gly: Glycerin (humectant) ·TEG: Triethylene Glycol (humectant) ·E1010: Orfin E1010 (acetylene glycol-based surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) ※ Note that the content of the colorant is the solid content.

[0124] 3.3. Examples 1 to 7, Comparative Examples 1 to 3 3.3.1. Evaluation of Plain Paper OD (Optical Density) The inkjet ink composition shown in Table 2 was filled into an inkjet printer PX-B700 (manufactured by Seiko Epson Corporation), and a patch pattern with 100% Duty was printed on a recording medium in the "plain paper clean" mode to obtain a recorded matter. As the recording medium, XEROX P paper (manufactured by Fuji Xerox Co., Ltd.), which is a type of plain paper, was used. For the obtained recorded matter, the OD value of the patch portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth), and the optical density value (OD value) was evaluated according to the following evaluation criteria. The results are shown in Table 2. (Evaluation Criteria) A: The OD value was 1.1 or more. B: The OD value was less than 1.1.

[0125] 3.3.2. PGPP Gloss (Glossiness) The ink composition shown in Table 2 was filled into an inkjet printer PX-B700 (manufactured by Seiko Epson Corporation), and a patch pattern with 100% Duty was printed on a recording medium in the "glossy paper standard" mode to obtain a recorded matter. As the recording medium, EPSON Photo Paper <Glossy> (manufactured by Seiko Epson Corporation), which is a type of glossy paper, was used. For the obtained recorded matter, the glossiness at 60° was measured using a gloss meter MULTI Gloss 268 (manufactured by Konica Minolta), and the glossiness was evaluated according to the following evaluation criteria. The results are shown in Table 2. (Evaluation Criteria) A: The glossiness was 30 or more. B: The glossiness was 20 or more and less than 30. C: The glossiness was less than 20.

[0126] 3.3.3. Liquid Passage Test 100 ml of the inkjet ink composition shown in Table 2 was filled into a cartridge ICY90L for an inkjet printer PX-B700 (manufactured by Seiko Epson Corporation) and left at room temperature (25°C) for 6 months and 12 months. Then, the ink composition was taken out from the cartridge, and the entire amount was filtered using an MF-Millipore membrane filter (SS 3 microns, diameter 49 mm), and the filter paper after filtration was observed with an optical microscope (300 times magnification). (Evaluation Criteria) A: No foreign substances were observed after storage for 6 months and 12 months. B: No foreign substances were observed after storage for 6 months, and even after storage for 12 months, it only covered less than one-tenth of the filter area. C: No foreign substances were observed after storage for 6 months, but after storage for 12 months, it covered one-tenth or more of the filter area. D: Foreign substances were observed, and it covered less than one-tenth of the filter area. E: Foreign substances were observed, and it covered one-tenth or more of the filter area.

[0127] 3.4. Production of Magenta Ink Composition, Cyan Ink Composition, and Black Ink Composition Each material was mixed in the composition shown in Table 3 below and stirred well to obtain each ink composition. Specifically, each ink composition was prepared by uniformly mixing each material and removing insoluble matter with a filter. In the table, the unit of the numerical value is mass%, and the total is 100.0 mass%.

[0128]

Table 3

[0129] In Table 3, Y1 and Y3 are yellow ink compositions (inkjet ink compositions), M1, M2, and M3 are magenta ink compositions, and C1 and C3 are cyan ink compositions. Also, Aqueous Dispersion I is the Aqueous Dispersion I obtained in the above [Production Example 1 of Aqueous Dispersion].

[0130] PV19 coated with a water-insoluble polymer is an aqueous dispersion of C.I.Pigment Violet 19 coated with a water-insoluble polymer having a solid content concentration of 20 mass%, obtained in the same manner as in Production Example 1 except that C.I.Pigment Violet 19 was used.

[0131] PR122 coated with a water-insoluble polymer is C.I.Pigment Red 12 An aqueous dispersion of C.I.Pigment Red 122 coated with a water-insoluble polymer having a solid content concentration of 20% by mass, obtained in the same manner as in Production Example 1 except that 2 was used.

[0132] PB15:4 coated with a water-insoluble polymer is an aqueous dispersion of C.I.Pigment Blue 15:4 coated with a water-insoluble polymer having a solid content concentration of 20% by mass, obtained in the same manner as in Production Example 1 except that C.I.Pigment Blue 15:4 was used.

[0133] (Preparation of self-dispersing CB dispersion) 20 g of commercially available carbon black S170 (trade name, manufactured by Degussa) was mixed with 500 g of water and dispersed with a household mixer for 5 minutes. The resulting liquid was placed in a 3-liter glass container equipped with a stirrer, and while stirring with the stirrer, an ozone-containing gas with an ozone concentration of 8% by weight was introduced at 500 cc / min. At this time, an electrolytic ozone generator manufactured by Permelex Electrodes was used as the ozone generator to generate ozone. The obtained dispersion stock solution was filtered through a glass fiber filter paper GA-100 (trade name: manufactured by Advantec Toyo Co., Ltd.), and further concentrated while adding a 0.1 N potassium hydroxide solution to adjust the pH to 9 until the pigment concentration reached 15% by weight to prepare a dispersion.

[0134] (Adjustment of St-Ac resin) Into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, 900 g of ion-exchanged water and 3 g of sodium lauryl sulfate were charged, and the temperature was raised to 70 °C while purging with nitrogen under stirring. While maintaining the internal temperature at 70 °C, 4 g of potassium persulfate was added as a polymerization initiator. After dissolution, an emulsion prepared by previously adding 20 g of acrylamide, 300 g of styrene, 640 g of butyl acrylate, and 30 g of methacrylic acid to 450 g of ion-exchanged water and 3 g of sodium lauryl sulfate and stirring was continuously dropped into the reaction solution over 4 hours. After completion of the dropping, aging was carried out for 3 hours. After the obtained aqueous emulsion was cooled to room temperature, ion-exchanged water and a 5% aqueous sodium hydroxide solution were added to adjust the solid content to 30% by weight and the pH to 8. The glass transition temperature (Tg) of the St-Ac resin was measured by a conventional method using DSC and was 15 °C.

[0135] Other abbreviations are the same as in Table 2.

[0136] 3.5. Evaluation of Inkjet 3.5.1. PGPP Gloss (YMC Image) Among the ink compositions shown in Table 4, the ink compositions of Y (yellow), M (magenta), and C (cyan) were filled into an inkjet printer PX-B700 (manufactured by Seiko Epson Corporation), and a patch pattern with 100% Duty was printed on a recording medium in the "Glossy Paper Standard" mode to obtain a recorded matter. As the recording medium, EPSON Photo Paper <Glossy> (manufactured by Seiko Epson Corporation), which is a type of glossy paper, was used. For the obtained recorded matter, the glossiness at 60° was measured using a gloss meter MULTI Gloss 268 (manufactured by Konica Minolta), and the glossiness was evaluated according to the following evaluation criteria. The results are shown in Table 4. (Evaluation Criteria) A: The glossiness was 30 or more. B: The glossiness was 20 or more and less than 30. C: The glossiness was less than 20.

[0137] [Table 4]

[0138] 3.5.2. Liquid Penetration Test For the ink compositions shown in Table 3, a mixed solution obtained by mixing the four colors of Y (yellow), M (magenta), C (cyan), and K (black) shown in Table 4 in equal weight ratio (1:1:1:1) was filled to 100 ml in a cartridge ICY90L for an inkjet printer PX - B700 (manufactured by Seiko Epson Corporation) and left at room temperature (25°C) for 6 months and 12 months.

[0139] Thereafter, the ink composition was taken out from the cartridge, and the entire amount was filtered using an MF - Millipore membrane filter (SS 3 microns, diameter 49 mm), and the filter paper after filtration was observed with an optical microscope (300 times magnification). (Evaluation Criteria) A: No foreign matter was observed after leaving for 6 months and 12 months. B: No foreign matter was observed after leaving for 6 months, and even after leaving for 12 months, it only covered less than one - tenth of the filter area. C: No foreign matter was observed after leaving for 6 months, but after leaving for 12 months, it covered one - tenth or more of the filter area. D: Foreign matter was observed after leaving for 6 months, and it covered less than one - tenth of the filter area. E: Foreign matter was observed after leaving for 6 months, and it covered one - tenth or more of the filter area.

[0140] 3.6. Evaluation Results The inkjet ink composition of each example containing an acetanilide-based monoazo pigment coated with a water-insoluble polymer, 1-(2-hydroxyethyl)-2-pyrrolidone, and water was found to give good results in the liquid passing test and to suppress the generation of foreign substances. Also, an inkjet ink composition containing an acetanilide-based monoazo pigment coated with a water-insoluble polymer, 1-(2-hydroxyethyl)-2-pyrrolidone, and water, a magenta ink composition containing a magenta pigment coated with a water-insoluble polymer, and a cyan ink composition containing a cyan pigment coated with a water-insoluble polymer. The ink sets of each example containing these were found to give good results in the liquid passing test and to suppress the generation of foreign substances.

[0141] Also, from the results of the liquid passing test, it was found that it is effective to contain HEP in order to suppress foreign substances in the acetanilide-based monoazo pigment, and the larger the total amount of HEP in each ink composition, the better the suppression can be achieved. From this, it was found that in the ink set, it is more preferable to contain HEP also in magenta, cyan, and black.

[0142] The above-described embodiments and modifications are examples and are not limited thereto. For example, it is also possible to appropriately combine each embodiment and each modification.

[0143] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations having the same functions, methods, and results, or configurations having the same purposes and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that exhibit the same operational effects as the configurations described in the embodiments or configurations that can achieve the same purpose. The present invention also includes configurations in which known techniques are added to the configurations described in the embodiments.

[0144] The following contents are derived from the above-described embodiments and modifications.

[0145] The inkjet ink composition An anilide acetoacetic acid monoazo pigment coated with a water-insoluble polymer, and 1-(2-hydroxyethyl)-2-pyrrolidone, and water, and contain.

[0146] According to this inkjet ink composition, since the anilide acetoacetic acid monoazo pigment is coated with a water-insoluble polymer, elution of causative substances of foreign matters is suppressed. Moreover, by containing 1-(2-hydroxyethyl)-2-pyrrolidone, it is possible to suppress the causative substances from becoming foreign matters. Thereby, even in a situation where foreign matters are likely to occur, such as when the inkjet ink composition is stored for a long time, the generation of foreign matters can be suppressed. Further, according to this inkjet ink composition, since an anilide acetoacetic acid monoazo pigment is used, an image with good color development can be formed. Furthermore, according to this inkjet ink composition, since the anilide acetoacetic acid monoazo pigment is coated with a water-insoluble polymer, an image with good gloss can be formed.

[0147] In the above inkjet ink composition, the anilide acetoacetic acid monoazo pigment may be C.I. Pigment Yellow 1 or C.I. Pigment Yellow 74.

[0148] According to this inkjet ink composition, even when a colorant that easily generates foreign matters is used, the generation of foreign matters can be suppressed. Further, according to this inkjet ink composition, an image with better color development can be formed.

[0149] In the above inkjet ink composition, it may further contain a humectant.

[0150] According to this inkjet ink composition, volatilization of moisture can be suppressed, and for example, storage stability can be further improved.

[0151] In the above inkjet ink composition, it may further contain a plasticizer.

[0152] According to this inkjet ink composition, since the water-insoluble polymer can be plasticized, the film-forming property of the water-insoluble polymer adhered to the recording medium can be enhanced. As a result, an image with better gloss can be formed.

[0153] An ink set comprises any one of the above inkjet ink compositions, a magenta ink composition containing a magenta pigment coated with a water-insoluble polymer, a cyan ink composition containing a cyan pigment coated with a water-insoluble polymer, and

[0154] According to this ink set, even in a situation where foreign matters are likely to occur, such as when stored for a long time in at least the inkjet ink composition, the generation of foreign matters can be suppressed.

[0155] In the above ink set, it may further contain a black ink composition containing a self-dispersing pigment.

[0156] According to this ink set, since the pigment has self-dispersibility, the solid content concentration of the pigment can be increased, and the black color development property can be enhanced.

[0157] In the above ink set, the black ink composition may contain a (meth)acrylic resin having a glass transition temperature of 20°C or lower.

[0158] According to this ink set, since the (meth)acrylic resin has good flexibility and is more easily film-formed when adhered to the recording medium, an image with better fixing property can be formed.

[0159] In the above ink set, The inkjet ink composition contained in the ink set and one or more ink compositions other than the inkjet ink composition may contain 1-(2-hydroxyethyl)-2-pyrrolidone.

[0160] According to this ink set, since 1-(2-hydroxyethyl)-2-pyrrolidone is contained in the ink composition other than the inkjet ink composition, generation of foreign matters can be further suppressed in the waste liquid discharged by flushing or the like.

Claims

1. An anilide acetoacetic acid monoazo pigment coated with a water-insoluble polymer, 1-(2-hydroxyethyl)-2-pyrrolidone, Water, contained, wherein the content of the 1-(2-hydroxyethyl)-2-pyrrolidone is 0.5% by mass or more and 10% by mass or less based on the total amount of the inkjet ink composition, the inkjet ink composition.

2. In Claim 1, wherein the anilide acetoacetic acid monoazo pigment is C.I. Pigment Yellow 1 or C.I. Pigment Yellow 74, the inkjet ink composition.

3. In Claim 1 or Claim 2, further containing a humectant, the inkjet ink composition.

4. In any one of Claims 1 to 3, further containing a plasticizer, the inkjet ink composition.

5. The inkjet ink composition according to any one of Claims 1 to 4, a magenta ink composition containing a magenta pigment coated with a water-insoluble polymer, a cyan ink composition containing a cyan pigment coated with a water-insoluble polymer, including, an ink set.

6. In Claim 5, further including a black ink composition containing a self-dispersing pigment, the ink set.

7. In Claim 6, wherein the black ink composition contains a (meth)acrylic resin having a glass transition temperature of 20°C or lower, the ink set.

8. In any one of Claims 6 to 7, wherein one or more of the inkjet ink composition contained in the ink set and the ink compositions other than the inkjet ink composition contain 1-(2-hydroxyethyl)-2-pyrrolidone, the ink set.

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