Aqueous ink composition for inkjet

Abstract

To provide an aqueous ink for inkjet, which enables good continuous printability by an improvement of dischargeability when printing by an inkjet system and enables image printing with good print density.SOLUTION: The aqueous ink composition for inkjet of the present invention comprises at least a coloring material, a surfactant, a binder, and an aqueous medium, where the surfactant includes an acetylene diol-based surfactant (A) having an HLB of 1-4 and represented by (CH3)2CHCH2C(CH3)(OH)CCC(CH3)(OH)CH2CH(CH3)2, an acetylene diol-based surfactant (B) having an HLB of 10-15 and represented by R1C(CH3)(OH)CCC(CH3)(OH)R2 (in the formula, R1 and R2 each independently represent C1-5 alkyl group), and an EO adduct (C) of an acetylene diol having an HLB of 10-15 and represented by (CH3)2CHCH2C(CH3)(OCH2CH2)nOHCCC(CH3)(OCH2CH2)mOHCH2CH(CH3)2 (in the formula, m and n are integers which satisfy 0.5≤m≤25, 0.5≤n≤25, 1≤m+n≤40), and a ratio of contents of these based on mass is 1.6:1:1-3:1:1.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition for inkjet, and more particularly to an aqueous ink composition for inkjet that is excellent in ejection properties during printing by an inkjet method and enables image printing with good printing density.

Background Art

[0002] In conventional aqueous ink compositions for inkjet (hereinafter sometimes referred to as "aqueous ink compositions"), in order to improve the printing density during printing on recording media such as plain paper and high-quality plain paper, the content ratio of the pigment contained in the aqueous ink composition has been increased. Also, in order to improve the permeability of the aqueous ink composition to the recording medium, various solvents have been added. Further, by adding a surfactant to the aqueous ink composition, the wettability of the aqueous ink composition inside the nozzles of the inkjet head is appropriately controlled to improve the ejection properties of the aqueous ink composition.

[0003] Here, examples of the surfactant added to the aqueous ink composition include silicone-based surfactants, fluorine-based surfactants, and acetylene diol-based surfactants. For example, Patent Document 1 describes that an aqueous ink composition excellent in ejection stability and the like can be provided by containing an acetylene diol-based surfactant in the aqueous ink composition.

[0004] However, even when using these surfactants, it may be insufficient to sufficiently wet the inside of the nozzles of the inkjet head. In that case, for example, the meniscus of the ink liquid surface of the aqueous ink composition is drawn too much into the nozzle and it becomes difficult to maintain an appropriate shape. As a result, there is a problem that poor ejection of the aqueous ink composition occurs during printing by the inkjet method, and blurring occurs in the printed image. Also, by increasing the content of the surfactant, it is conceivable to improve such ejection failure. However, in that case, as a result of the decrease in the surface tension of the aqueous ink composition, the aqueous ink composition is overly wetted in the nozzle. As a result, an appropriate meniscus of the ink liquid surface is not formed in the nozzle, and there is a problem that the aqueous ink composition leaks from the nozzle. Further, by increasing the content of the surfactant, as a result of the increase in the permeability of the aqueous ink composition to the recording medium, diffraction and scattering of light occur in the printed image, and the amount of coloring material remaining in the surface layer portion of the recording medium also decreases, resulting in a problem that the printing density of the printed image decreases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above problems, and its object is to provide an aqueous ink composition for inkjet that enables good continuous printability by improving the ejection property during printing by the inkjet method and enables image printing with good printing density.

Means for Solving the Problems

[0007] The aqueous ink composition for inkjet according to the present invention is an aqueous ink composition for inkjet containing at least a coloring material, a surfactant, a binder, and an aqueous medium, wherein the surfactant has an HLB in the range of 1 to 4, and is an acetylene diol-based surfactant (A) represented by the chemical formula (CH3)2CHCH2C(CH3)(OH)CCC(CH3)(OH)CH2CH(CH3)2, and has an HLB in the range of 10 to 15, and the chemical formula R 1 C(CH3)(OH)CCC(CH3)(OH)R 2 (wherein R 1 and R 2 each independently represents an alkyl group having 1 to 5 carbon atoms.) an acetylene diol-based surfactant (B) represented by, and has an HLB in the range of 10 to 15, and the chemical formula (CH3)2CHCH2C(CH3)(OCH2CH2) n OHCCC(CH3)(OCH2CH2) m OHCH2CH(CH3)2 (wherein m and n are integers satisfying 0.5 ≦ m ≦ 25, 0.5 ≦ n ≦ 25, and 1 ≦ m + n ≦ 40). An ethylene oxide adduct (C) of acetylene diol represented by, and the content ratio of the acetylene diol-based surfactant (A), the acetylene diol-based surfactant (B), and the ethylene oxide adduct (C) of acetylene diol is based on mass. The acetylene diol-based surfactant (A): the acetylene diol-based surfactant (B): the ethylene oxide adduct (C) of acetylene diol = 1.6:1:1 to 3:1:1.

[0008] According to the above configuration, as the surfactant, one containing an acetylene diol-based surfactant (A), an acetylene diol-based surfactant (B), and an ethylene oxide adduct of acetylene diol (C) is used, and further, the ratio of the contents of these surfactants is in the range of 1.6:1:1 to 3:1:1 on a mass basis, whereby the wettability of the aqueous ink composition inside the nozzles of the inkjet head can be controlled within an appropriate range. That is, according to the above configuration, it is possible to prevent the meniscus of the ink liquid surface of the aqueous ink composition from being drawn into the nozzle too much, improve the ejection property during printing, and enable good continuous printability. Also, it is possible to prevent the aqueous ink composition from wetting too much inside the nozzle, so that a meniscus with an appropriate shape of the ink liquid surface is not formed, and the aqueous ink composition does not drop from the nozzle and cause dripping. Furthermore, according to the above configuration, in order to improve the wettability of the aqueous ink composition inside the nozzle, it is not necessary to excessively increase the content of the surfactant. Thereby, it is possible to suppress the excessive penetration of the aqueous ink composition into the recording medium. As a result, it is possible to reduce the occurrence of diffraction and scattering of light in the printed image, and to allow the coloring material to remain in the surface layer portion without excessively penetrating into the recording medium, and it is also possible to reduce or suppress the decrease in the printing density of the printed image.

[0009] In the above configuration, it is preferable that the surfactant further contains an alcohol alkoxylate. Thereby, it is possible to further improve the ejection property of the aqueous ink composition from the nozzle and further suppress the decrease in the printing density of the printed image.

[0010] In the above configuration, it is preferable that the aqueous medium contains polyoxyethylene glycol having an added mole number of ethylene oxide in the range of 2 to 4. Thereby, it is possible to further improve the ejection property of the aqueous ink composition from the nozzle and further suppress the decrease in the printing density of the printed image.

[0011] In the above configuration, the coloring material may be at least any one of a cyan pigment, a magenta pigment, a yellow pigment, and a black pigment.

[0012] In the above configuration, it further preferably contains a humectant, and the humectant preferably contains a polyhydric alcohol having a valence of 3 or more. Thereby, drying of the aqueous ink composition can be prevented, and clogging near the nozzles of the inkjet head can be prevented or reduced. As a result, the ejectability of the aqueous ink composition can be further improved.

[0013] In the above configuration, it further preferably contains a penetration control agent, and the penetration control agent preferably contains at least one of a glycol-based solvent having 2 to 5 carbon atoms and a heterocyclic compound. Thereby, it becomes possible to control the penetrability of the aqueous ink composition into the recording medium. For example, it is possible to suppress the colorant from excessively penetrating into the recording medium and not remaining in the surface layer portion, and to suppress a decrease in the printing density of the printed image.

Advantages of the Invention

[0014] According to the aqueous ink composition for inkjet of the present invention, for example, compared with conventional surfactants such as silicone-based surfactants and fluorine-based surfactants, it has excellent ejectability during printing by the inkjet method, and can print an image with good density.

Embodiments for Carrying Out the Invention

[0015] (Aqueous Ink Composition for Inkjet) The aqueous ink composition for inkjet according to the present embodiment (hereinafter referred to as "aqueous ink composition") will be described below.

[0016] The aqueous ink composition of the present embodiment contains at least a colorant, a surfactant, a binder, and an aqueous medium. This aqueous ink composition can be suitably used for printing by the inkjet method. Here, in this specification, the "inkjet method" means a printing method in which an aqueous ink containing an aqueous ink composition is ejected as droplets from, for example, a known piezo-type inkjet head, and the droplets are fixed on a recording medium to form a printed image or the like. The details of the recording medium will be described later.

[0017] [Pigment] Examples of the pigment include pigments or dyes used for printing by an inkjet method.

[0018] The pigment preferably contains at least one of a cyan pigment, a magenta pigment, a yellow pigment, and a black pigment. For example, examples of inorganic pigments include titanium oxide, iron oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, ultramarine blue, navy blue, carbon black, graphite, calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, talc, and the like. Examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, thioindigo pigments, triphenylmethane lake pigments, oxazine lake pigments, and the like. These pigments may be used alone or in combination of two or more. Note that the pigments in the present embodiment are not limited to those exemplified.

[0019] In addition, as the pigment, a self-dispersible pigment or a resin-dispersed pigment can also be used. Among these pigments, from the viewpoint of increasing the printing density (image density), a self-dispersible pigment is preferable.

[0020] A self-dispersible pigment is a pigment in which various functional groups are chemically bonded to the surface of pigment particles, and thus it can be dispersed in an aqueous medium without using a pigment dispersant such as a resin or a surfactant. The pigment particles used for the self-dispersible pigment are not particularly limited, and any of the aforementioned inorganic pigments and organic pigments can be used. The functional groups are not particularly limited, and examples thereof include a hydroxyl group, a quinone group, a carbonyl group, a carboxyl group, a phosphate group, a sulfone group, an amine group, or salts thereof.

[0021] Specific examples of the self-dispersible pigment include self-dispersible carbon black, self-dispersible phthalocyanine, self-dispersible quinacridone, self-dispersible azo, and the like.

[0022] A resin-dispersed pigment is a pigment that can be dispersed in an aqueous medium by a resin dispersant soluble in the aqueous medium. The pigment used in the resin-dispersed pigment is not particularly limited, and any of the aforementioned inorganic pigments and organic pigments can be used. Also, the resin dispersant is not particularly limited, and examples thereof include polyvinyl alcohols, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer, acrylic acid-acrylic ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, or salts thereof. These resin dispersants may be used alone or in combination of two or more kinds.

[0023] The ratio of the pigment particles to the resin dispersant in the resin-dispersed pigment is not particularly limited and can be set as appropriate according to the need.

[0024] Specific examples of the resin-dispersed pigment include resin-dispersed carbon black, resin-dispersed phthalocyanine, resin-dispersed quinacridone, resin-dispersed azo, etc.

[0025] The dye is not particularly limited, and examples thereof include Red No. 2, Red No. 4, Red No. 40, Red No. 102, Yellow No. 4, Yellow No. 5, Green No. 3, Blue No. 1, chlorophyllin pigments, natural pigments, etc. The chlorophyllin pigments are not particularly limited, and examples thereof include sodium iron chlorophyllin, sodium copper chlorophyllin, sodium chlorophyllin, etc. Also, the natural pigments are not particularly limited, and examples thereof include cochineal pigment, cacao pigment, caramel pigment, etc.

[0026] The content of the coloring material affects the image density, the storage stability, viscosity, pH, etc. of the aqueous ink composition. Therefore, the content of the coloring material is preferably set appropriately in consideration of these points. More specifically, the content of the coloring material is preferably in the range of 1% to 10% by mass in terms of solid content based on the total mass of the aqueous ink composition, more preferably in the range of 3% to 10% by mass, and particularly preferably in the range of 4.5% to 7% by mass. By setting the content of the coloring material to 1% by mass or more, a decrease in image density can be suppressed, and the effect is particularly remarkable when it is 4.5% by mass or more. On the other hand, by setting the content of the coloring material to 10% by mass or less, a decrease in ejection performance due to nozzle clogging can be prevented, and the effect is particularly remarkable when it is 7% by mass or less.

[0027] [Surfactant] The surfactant contains at least an acetylene diol-based surfactant (A), an acetylene diol-based surfactant (B), and an ethylene oxide (EO) adduct (C) of acetylene diol.

[0028] The acetylene diol-based surfactant (A) is a compound represented by (CH3)2CHCH2C(CH3)(OH)CCC(CH3)(OH)CH2CH(CH3)2 having an HLB (hydrophilic-lipophilic balance) in the range of 1 to 4, preferably 2 to 4. Commercially available products of the acetylene diol-based surfactant (A) are not particularly limited, and examples include Surfynol (registered trademark) 104PA (HLB value: 4), Surfynol 420 (HLB value: 4) (trade name, manufactured by Air Products Japan, Ltd.), etc.

[0029] The acetylene diol-based surfactant (B) has an HLB in the range of 10 to 15, preferably 12 to 14, and is R 1 C(CH3)(OH)CCC(CH3)(OH)R 2 (wherein R 1 and R 2Each independently represents an alkyl group having 1 to 5 carbon atoms. It is a compound represented by (). In the present specification, when representing the range of the number of carbon atoms, the range means including all the integer numbers of carbon atoms included in the range. Therefore, for example, an alkyl group having "1 to 3 carbon atoms" means all alkyl groups having 1, 2, and 3 carbon atoms.

[0030] The alkyl group may be either a linear alkyl group or a branched alkyl group. More specifically, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. R 1 and R 2 may be the same or different from each other.

[0031] Commercially available products of the acetylene diol-based surfactant (B) are not particularly limited. For example, Surfynol 465 (HLB value: 13) (trade name, manufactured by Air Products Japan Co., Ltd.) and the like can be mentioned.

[0032] The EO adduct (C) of acetylene diol is an adduct in which an ethylene oxide group (EO) is added to acetylene diol in a predetermined number of moles of addition. More specifically, the EO adduct (C) of acetylene diol has an HLB in the range of 10 to 15, preferably 12 to 14, and the chemical formula (CH3)2CHCH2C(CH3)(OCH2CH2) n OHCCC(CH3)(OCH2CH2) m OHCH2CH(CH3)2 (wherein m and n are integers satisfying 0.5 ≦ m ≦ 25, 0.5 ≦ n ≦ 25, and 1 ≦ m + n ≦ 40).

[0033] Commercially available products of the EO adduct (C) of acetylene diol are not particularly limited. For example, Orfin (registered trademark) E1010 (trade name, manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 13) and the like can be mentioned.

[0034] In the present specification, the HLB value is the HLB value calculated by the Griffin method and means the value obtained by the following formula. HLB value = 20 × (sum of formula weights of hydrophilic groups / molecular weight) The HLB value is within the range of 0 to 20. The larger the HLB value, the stronger the hydrophilicity, and the smaller the HLB value, the stronger the hydrophobicity.

[0035] The content of the surfactant is preferably in the range of 0.1% by mass or more and 5% by mass or less, more preferably in the range of 0.5% by mass or more and 4% by mass or less, based on the total mass of the aqueous ink composition. By setting the content of the surfactant to 0.1% by mass or more, it is possible to prevent the meniscus of the ink liquid surface in the aqueous ink composition from being drawn too much into the nozzle, improve the ejection property during printing by the inkjet method, and enable good continuous printability. On the other hand, by setting the content of the surfactant to 5% by mass or less, it is possible to prevent the aqueous ink composition from being overly wetted in the nozzle and prevent the aqueous ink composition from dripping from the nozzle. In addition, it is also possible to suppress the adverse effects of insoluble components or poor emulsification of the surfactant on the ejection of the aqueous ink composition.

[0036] In addition, the ratio of the contents of the acetylene diol-based surfactant (A), the acetylene diol-based surfactant (B), and the EO adduct of acetylene diol (C) is in the range of 1.6:1:1 to 3:1:1 on a mass basis, preferably in the range of 2:1:1 to 3:1:1.

[0037] In addition, in the surfactant of the present embodiment, other surfactants may be contained. Examples of other surfactants include alcohol alkoxylates. By containing an alcohol alkoxylate, the ejection property during printing by the inkjet method is improved, good continuous printability is enabled, and a reduction in printing density is prevented. In the present invention, it is preferable not to contain a silicone-based surfactant and a fluorine-based surfactant as other surfactants.

[0038] The alcohol alkoxylate is not particularly limited, and examples thereof include alcohol ethoxylate, oleyl alcohol ethoxylate, and the like. Further, commercially available products of alcohol alkoxylate are not particularly limited, and examples thereof include Adeka Tol (registered trademark, manufactured by ADEKA Corporation), Konion (registered trademark, manufactured by Shin Nippon Rika Co., Ltd.), DYNWET (registered trademark, manufactured by BYK-Chemie Japan Co., Ltd.), and the like.

[0039] When the surfactant contains an alcohol alkoxylate, the content ratio of the alcohol alkoxylate is preferably in the range of 0.1 to 2.0, more preferably in the range of 0.2 to 1.0, based on the total mass of the aqueous ink composition by mass. By further containing the alcohol alkoxylate within the above range, the ejection property during printing by the inkjet method can be further improved, and the reduction of the printing density can be further prevented.

[0040] [Binder] The binder preferably contains a polyolefin resin dispersion and at least one resin selected from the group consisting of a styrene acrylic resin, a styrene maleic acid resin, and a polyurethane resin. Thereby, while improving the ejection property, it enables printing of a printed image excellent in rubbing resistance and water resistance.

[0041] The polyolefin resin dispersion is a resin dispersion in which a polyolefin resin is dispersed in water in the form of an emulsion (latex or dispersion). By adding the polyolefin resin to water in the form of an emulsion resin dispersion, precipitation of the polyolefin resin that does not dissolve in water is prevented. For example, when a powdery polyolefin resin is added to water, the resulting composition is a composition in which the polyolefin resin precipitates without dissolving in water. As a result, the composition cannot be ejected from the inkjet head, and printing by the inkjet method becomes difficult.

[0042] The polyolefin resin dispersion of this embodiment functions as a binder in the aqueous ink composition. By blending the polyolefin resin dispersion, in the ink layer printed using the aqueous ink composition of this embodiment, for example, compared with the case of an aqueous ink composition using only a styrene acrylic resin, a styrene maleic acid resin, or a polyurethane resin (hereinafter referred to as "styrene acrylic resin etc.") as a binder, the film-forming temperature can be lowered. As a result, in the ink layer using the aqueous ink composition of this embodiment, for example, even when dried at a drying temperature of 80°C and a drying time of 10 minutes, it can be sufficiently dried and has excellent drying properties. Also, the abrasion resistance under the same drying conditions can be improved compared with the case of using only a styrene acrylic resin etc.

[0043] Examples of the polyolefin resin in the polyolefin resin dispersion include anionic polyolefin resins and nonionic polyolefin resins. Among these, in the present invention, anionic polyolefin resins are preferred from the viewpoints of abrasion resistance and water resistance.

[0044] The anionic polyolefin resin is not particularly limited, and examples thereof include acid-modified polyolefin resins such as maleic anhydride-modified polyolefin resins, chlorinated polyolefin resins, and non-chlorinated polyolefin resins. Also, commercially available products can be used as the polyolefin resin emulsion. Examples of such commercially available products include Hardlen (registered trademark) NZ-1004 (solid content concentration: 30% by mass), Hardlen NZ-1015 (solid content concentration: 30% by mass) (both are product names manufactured by Toyobo Co., Ltd.), Arrowbase (registered trademark) DA-1010 (solid content concentration: 25% by mass), Arrowbase DB-4010 (solid content concentration: 25% by mass) (both are product names manufactured by Unitika Ltd.), Super Cron (registered trademark) E-415 (solid content concentration: 30% by mass), Super Cron E-480T (solid content concentration: 30% by mass), Super Cron E-604 (solid content concentration: 40% by mass) (all are product names manufactured by Nippon Paper Industries Co., Ltd.), etc.

[0045] Styrene acrylic resin, styrene maleic resin, and polyurethane resin are optional components and function as binders in this embodiment. In this embodiment, these resins are not formulated as pigment dispersants.

[0046] The styrene acrylic resin is not particularly limited. For example, as its constituent components, it includes at least one styrene-based monomer component selected from the group consisting of styrene and its derivatives in the molecule, and at least one acrylic acid-based monomer component selected from the group consisting of (meth)acrylic acid and its derivatives. Examples of the styrene acrylic resin also include polymers containing monomer components other than the styrene-based monomer component and the acrylic acid-based monomer component. In this specification, "(meth)acrylic acid" means "acrylic acid" as well as "methacrylic acid".

[0047] The styrene maleic resin is not particularly limited. For example, as its constituent components, it includes at least one styrene-based monomer component selected from the group consisting of styrene and its derivatives in the molecule, and at least one maleic acid-based monomer component selected from the group consisting of maleic acid and its derivatives. Examples of the styrene maleic resin also include polymers containing monomer components other than the styrene-based monomer component and the maleic acid-based monomer component.

[0048] The polyurethane resin is not particularly limited. For example, polymers containing polyisocyanate, polyol, etc. in its constituent components can be mentioned.

[0049] In the present embodiment, the styrene acrylic resin, styrene maleic acid resin, and polyurethane resin are blended so as to be 0.75% by mass or less, preferably 0.6% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0% by mass in terms of solid content based on the total mass of the aqueous ink composition. By setting the content of the styrene acrylic resin or the like to 0.75% by mass or less in terms of solid content, it is possible to suppress the film-forming temperature of the ink layer formed by printing with the aqueous ink composition of the present embodiment from becoming excessively high. Thereby, good drying properties can be maintained. Also, the abrasion resistance can be improved as compared with the case where only the styrene acrylic resin or the like is used. Further, for example, in the styrene acrylic resin and styrene maleic acid resin, the ester bond in the molecule is easily hydrolyzed, and in the polyurethane resin, the urethane bond in the molecule is easily hydrolyzed. Therefore, in an aqueous ink composition containing a large amount of these resins, the water resistance and solvent resistance of the ink layer printed using the aqueous ink composition are not good. However, by suppressing the content of the styrene acrylic resin or the like to 0.75% by mass or less based on the total mass of the aqueous ink composition as in the present embodiment, it is possible to suppress or prevent the water resistance of the ink layer from decreasing.

[0050] Also, in the present embodiment, it is preferable that the binder consists only of a polyolefin resin dispersion. Thereby, the film-forming temperature of the ink layer formed by the aqueous ink composition of the present embodiment can be reduced, and sufficient drying can be achieved even under normal drying conditions, and the abrasion resistance can be further improved. Also, since it does not contain a styrene acrylic resin or the like, the water resistance of the ink layer can be further improved.

[0051] The content of the polyolefin resin dispersion is 1.2% by mass or more, preferably 1.5% by mass or more and 6% by mass or less, more preferably 3% by mass or more and 4.5% by mass or less in terms of solid content based on the total mass of the aqueous ink composition. By setting the content of the polyolefin resin dispersion in terms of solid content to 1.2% by mass or more, the abrasion resistance can be maintained well. In addition, by setting the content of the polyolefin resin emulsion in terms of solid content to 6% by mass or less, the dischargeability of the aqueous ink composition from the inkjet head can be maintained well.

[0052] [Aqueous medium] Examples of the aqueous medium used in the aqueous ink composition of the present embodiment include water. As the water, it is preferable to use pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, distilled water, or water from which ionic impurities such as ultrapure water have been removed.

[0053] In addition, as the aqueous medium, a mixed solution of water and a water-soluble organic solvent may be used. The water-soluble organic solvent is not particularly limited. Specifically, for example, alcohols such as methyl alcohol, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-propyl alcohol, and isopropyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane, ethylene glycol methyl ether, ethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether, and triethylene glycol monoethyl ether; polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2,6-hexanetriol, thiodiglycol, polyethylene glycol, polypropylene glycol, glycerin, diglycerin, and polyglycerin; N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like. Among these water-soluble organic solvents, from the viewpoints of improving the ejectability of the aqueous ink composition and preventing the reduction of printing density, polyoxyethylene glycol having an added mole number of ethylene oxide of 2 to 4, more specifically, diethylene glycol, triethylene glycol, and tetraethylene glycol are preferable, diethylene glycol and triethylene glycol are more preferable, and triethylene glycol is particularly preferable. The water-soluble organic solvent can be used alone or in combination of two or more kinds.

[0054] The content of the aqueous medium is not particularly limited, but usually it is 5% by mass or more and 50% by mass or less, preferably 5% by mass or more and 45% by mass or less, based on the total mass of the aqueous ink composition. Further, when a mixed solution of water and a water-soluble organic solvent is used as the aqueous medium, the ratio of water to the water-soluble organic solvent is preferably in the range of 10:90 to 50:50, more preferably in the range of 20:80 to 40:60, and even more preferably in the range of 30:70 to 40:60.

[0055] [Other Additives] In the aqueous ink composition of the present embodiment, other additives may be blended as long as the effects of the present invention are not impaired. Examples of the additives include humectants, penetration (control) agents, pigment dispersants, water-soluble resins, pH adjusters, chelating agents, preservatives, viscosity adjusters, defoaming agents, dispersion stabilizers, anti-reducing agents, antioxidants, and the like. Except for the humectants and penetration agents, the contents of these additives are not particularly limited and can be set as appropriate according to need (the contents of the humectants and penetration agents will be described later).

[0056] Examples of the humectants include polyhydric alcohols having three or more hydroxyl groups. The polyhydric alcohols having three or more hydroxyl groups are not particularly limited, and examples thereof include polyethylene glycol, glycerin, and polyglycerin. Among these, from the viewpoint of preventing drying of the nozzle surface, high-boiling water-soluble polyhydric alcohols such as glycerin and polyglycerin are preferable. These humectants can be used alone or in combination of two or more.

[0057] The addition amount of the humectant is preferably in the range of 1% by mass or more and 20% by mass or less, more preferably in the range of 5% by mass or more and 15% by mass or less, based on the total mass of the aqueous ink composition. By setting the content of the humectant to 1% by mass or more, clogging near the nozzles of the inkjet head can be prevented when printing by the inkjet method, and the ejection performance can be further improved. In particular, when the content is 5% by mass or more, the effect is more remarkable. On the other hand, by setting the content of the humectant to 20% by mass or less, the viscosity of the aqueous ink composition can be appropriately controlled, and in particular, when the content is 15% by mass or less, the effect is more remarkable.

[0058] Examples of the penetration (control) agent include glycol solvents having 2 to 5 carbon atoms and heterocyclic compounds. The glycol solvent having 2 to 5 carbon atoms is not particularly limited, and examples thereof include ethylene glycol and propylene glycol. The heterocyclic compound is not particularly limited, and examples thereof include nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-hydroxyethyl-2-pyrrolidone. The exemplified penetration (control) agents can be used alone or in combination of two or more.

[0059] The addition amount of the penetration (control) agent is preferably in the range of 1% by mass or more and 20% by mass or less, more preferably in the range of 5% by mass or more and 15% by mass or less, based on the total mass of the aqueous ink composition. By setting the content of the penetration (control) agent to 1% by mass or more, sufficient penetrability of the aqueous ink composition into the recording medium can be maintained, and the effect is particularly remarkable when it is 5% by mass or more. On the other hand, by setting the content of the penetration (control) agent to 20% by mass or less, it is possible to suppress the excessive penetration of the coloring material into the recording medium and its non-residual in the surface layer portion, and to suppress the decrease in the printing density of the printed image. In addition, it is possible to suppress the excessive increase in the viscosity of the aqueous ink composition and maintain the stability of the aqueous ink composition. These effects are particularly remarkable when it is 15% by mass or less.

[0060] In addition, when the above-described self-dispersible pigment or resin-dispersed pigment is used as the coloring material, the blending of the pigment dispersant into the aqueous ink composition can be omitted. When a pigment other than the self-dispersible pigment and the resin-dispersed pigment is used, it is preferable to blend a pigment dispersant into the aqueous ink composition. The pigment dispersant is not particularly limited, and known ones can be appropriately adopted.

[0061] [Others] Considering the ejection property from the inkjet nozzle, the viscosity of the aqueous ink composition of the present embodiment is preferably 3 mPa·s to 6 mPa·s, more preferably 3.5 mPa·s to 5.7 mPa·s when ejected from the inkjet nozzle. By setting the viscosity of the aqueous ink composition within the above numerical range, the occurrence of clogging in the inkjet nozzle can be further suppressed, and good ejection property can be maintained. The viscosity of the aqueous ink composition can be obtained, for example, by measuring with a viscometer (trade name: VISCOMATE MODEL VM-10A, manufactured by Sekonic Corporation) under the condition of a measurement temperature of 25°C.

[0062] The aqueous ink composition of the present embodiment can be used as an aqueous ink composition capable of forming a printed image by forming an ink layer on the surface of a recording medium. Further, the aqueous ink composition of the present embodiment can be used not only when it is included in the aqueous ink for inkjet which is the final product, but also as the aqueous ink for inkjet itself.

[0063] (Method for manufacturing an aqueous ink composition for inkjet) The aqueous ink composition of the present embodiment can be produced by mixing a coloring material, a surfactant, a binder, an aqueous medium, and other additives to be blended as needed in an arbitrary order. For example, when using a pigment as the coloring material, the pigment, surfactant, binder, and aqueous medium are mixed at once, and the resulting mixture is subjected to a dispersion treatment using a normal disperser. The dispersion time at this time is not particularly limited, but it is preferably set so that the average dispersed particle diameter of the pigment in the dispersed state is within a specific range.

[0064] The disperser used in the dispersion treatment of the pigment is not particularly limited as long as it is a commonly used disperser. Specifically, for example, a ball mill, a roll mill, a sand mill, a bead mill, a paint shaker, a nanomizer, etc. can be mentioned.

[0065] Subsequently, with respect to the dispersion obtained by the dispersion treatment, the above-described other additives are further mixed by an appropriate method, whereby an aqueous ink composition using a pigment as a coloring material can be obtained.

[0066] The mixing method of each material is not particularly limited. For example, the materials can be sequentially added to a container equipped with a stirring device such as a disper, a mechanical stirrer, or a magnetic stirrer, and stirred and mixed. Also, the filtration method is not particularly limited, and for example, centrifugal filtration, filter filtration, etc. can be employed.

[0067] (Recording medium) The recording medium is not particularly limited, and conventionally known ones can be adopted. Specifically, for example, printing papers such as coated paper, art paper, and matte paper, and films, etc. can be mentioned.

Examples

[0068] Hereinafter, preferred embodiments of the present invention will be exemplarily described in detail. However, the materials, contents, etc. described in the following examples do not limit the scope of the present invention only to those, unless otherwise particularly limited.

[0069] (Example 1) As shown in Table 1, a self-dispersing black pigment at 40% by mass (in terms of solid content: 6% by mass) (solid content concentration: 15% by mass), an anionic polyolefin resin emulsion at 10% by mass (in terms of solid content: 1.5% by mass) (trade name: Hardlen (registered trademark) NZ-1004, manufactured by Toyobo Co., Ltd., solid content concentration: 30% by mass), 0.8% by mass of an acetylene diol-based surfactant (A) (trade name: Surfynol (registered trademark) 104PA, manufactured by Air Products Co., Ltd.), 0.5% by mass of an acetylene diol-based surfactant (B) (trade name: Surfynol 465, manufactured by Air Products Co., Ltd.), 0.5% by mass of an EO adduct of acetylene diol (C) (trade name: Orfin (registered trademark) E1010, manufactured by Nissin Chemical Industry Co., Ltd.), 5% by mass of diethylene glycol monobutyl ether (trade name: Hisolb DB, manufactured by Toho Chemical Industry Co., Ltd.), 5% by mass of triethylene glycol, and 38.2% by mass of water were mixed to prepare the aqueous ink composition according to this example.

[0070] (Example 2) As shown in Table 1, in this example, the content of the acetylene diol-based surfactant (A) was changed to 1% by mass, and the water content was changed to 38% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this example was prepared.

[0071] (Example 3) As shown in Table 1, in this example, the content of the acetylene diol-based surfactant (A) was changed to 1.2% by mass, and the water content was changed to 37.8% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this example was prepared.

[0072] (Example 4) As shown in Table 1, in this example, the content of the acetylene diol-based surfactant (A) was changed to 1.5% by mass, and the water content was changed to 37.5% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this example was prepared.

[0073] (Example 5) As shown in Table 1, in this example, as a surfactant, 0.5% by mass of alcohol alkoxylate (trade name: DYNWET (registered trademark) 800N, manufactured by Big Chemie Japan Co., Ltd.) was further added, and the water content was changed to 37.5% by mass. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0074]

Table 1

[0075] (Comparative Example 1) As shown in Table 2, in this comparative example, the content of the acetylene diol-based surfactant (A) was changed to 0.5% by mass, and the water content was changed to 38.5% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this comparative example was prepared.

[0076] (Comparative Example 2) As shown in Table 2, in this comparative example, the content of the acetylene diol-based surfactant (A) was changed to 2% by mass, and the water content was changed to 37% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this comparative example was prepared.

[0077] (Comparative Example 3) As shown in Table 2, in this comparative example, as a surfactant, only 1% by mass of the acetylene diol-based surfactant (A) was added, and the water content was changed to 39% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this comparative example was prepared.

[0078] (Comparative Example 4) As shown in Table 2, in this comparative example, as a surfactant, only 2% by mass of the acetylene diol-based surfactant (B) was added, and the water content was changed to 38% by mass. Otherwise, in the same manner as in Example 1, the aqueous ink composition according to this comparative example was prepared.

[0079] (Comparative Example 5) As shown in Table 2, in this comparative example, as the surfactant, only 2% by mass of an EO adduct (C) of acetylenediol was added, and the water content was changed to 38% by mass. Otherwise, in the same manner as in Example 1, an aqueous ink composition according to this comparative example was prepared.

[0080] (Comparative Example 6) As shown in Table 2, in this comparative example, as the surfactant, only 1% by mass of an acetylenediol-based surfactant (A) and 0.5% by mass of an EO adduct (C) of acetylenediol were added, and the water content was changed to 38.5% by mass. Otherwise, in the same manner as in Example 1, an aqueous ink composition according to this comparative example was prepared.

[0081] (Comparative Example 7) As shown in Table 2, in this comparative example, as the surfactant, only 1% by mass of an acetylenediol-based surfactant (A) and 0.5% by mass of an acetylenediol-based surfactant (B) were added, and the water content was changed to 38.5% by mass. Otherwise, in the same manner as in Example 1, an aqueous ink composition according to this comparative example was prepared.

[0082] (Comparative Example 8) As shown in Table 2, in this comparative example, as the surfactant, only 0.5% by mass of an acetylenediol-based surfactant (B) and 0.5% by mass of an EO adduct (C) of acetylenediol were added, and the water content was changed to 39% by mass. Otherwise, in the same manner as in Example 1, an aqueous ink composition according to this comparative example was prepared.

[0083]

Table 2

[0084] (Example 6) As shown in Table 3, in this example, the penetrant was changed to triethylene glycol dimethyl ether. Otherwise, in the same manner as in Example 2, an aqueous ink composition according to this example was prepared.

[0085] (Example 7) As shown in Table 3, in this example, the penetrant was changed to triethylene glycol monomethyl ether. Otherwise, an aqueous ink composition according to this example was prepared in the same manner as in Example 2.

[0086] (Example 8) As shown in Table 3, in this example, the penetrant was changed to propylene glycol monopropyl ether. Otherwise, an aqueous ink composition according to this example was prepared in the same manner as in Example 2. <on

[0087] (Example 9) As shown in Table 3, in this example, the water-soluble organic solvent was changed to diethylene glycol. Otherwise, an aqueous ink composition according to this example was prepared in the same manner as in Example 2.

[0088] (Example 10) As shown in Table 3, in this example, the colorant was changed to a resin-dispersed black pigment (solid content concentration: 16% by mass) of 40% by mass (in terms of solid content: 6.4% by mass). Otherwise, an aqueous ink composition according to this example was prepared in the same manner as in Example 2.

[0089]

Table 3

[0090] (Example 11) As shown in Table 4, in this example, the binder was changed to a styrene acrylic resin (trade name: Joncryl 96J, manufactured by BASF Japan Ltd., solid content concentration: 30% by mass) of 10% by mass (in terms of solid content: 3% by mass). Otherwise, an aqueous ink composition according to this example was prepared in the same manner as in Example 2.

[0091] (Example 12) As shown in Table 4, in this example, the binder was changed to a styrene maleic acid resin (trade name: SMA 1440H, manufactured by TOTAL Co., Ltd., solid content concentration: 30% by mass) at 10% by mass (in terms of solid content: 3% by mass). Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0092] (Example 13) As shown in Table 4, in this example, the binder was changed to a nonionic polyolefin resin (trade name: AQUACER® 515, manufactured by BYK-Chemie Japan Co., Ltd.) at 10% by mass. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0093] (Example 14) As shown in Table 4, in this example, the binder was changed to a nonionic polyolefin resin (trade name: AQUACER® 531, manufactured by BYK-Chemie Japan Co., Ltd.) at 10% by mass. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0094] (Example 15) As shown in Table 4, in this example, the binder was changed to a nonionic polyolefin resin (trade name: AQUACER® 551, manufactured by BYK-Chemie Japan Co., Ltd.) at 10% by mass. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0095] (Example 16) As shown in Table 4, in this example, the binder was changed to a polyurethane resin (trade name: WBR-016U, manufactured by Daisheng Fine Chemical Co., Ltd.) at 10% by mass. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0096]

Table 4

[0097] (Example 17) As shown in Table 5, in this example, as the binder, 9% by mass (in terms of solid content: 2.7% by mass) of an anionic polyolefin resin emulsion (trade name: Hardlen (registered trademark) NZ-1004, manufactured by Toyobo Co., Ltd., solid content concentration: 30% by mass) and 1% by mass (in terms of solid content: 0.3% by mass) of a styrene acrylic resin (trade name: Joncryl 96J, manufactured by BASF Japan Ltd., solid content concentration: 30% by mass) were used. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0098] (Example 18) As shown in Table 5, in this example, as the binder, 8% by mass (in terms of solid content: 2.7% by mass) of an anionic polyolefin resin emulsion (trade name: Hardlen (registered trademark) NZ-1004, manufactured by Toyobo Co., Ltd., solid content concentration: 30% by mass) and 2% by mass (in terms of solid content: 0.3% by mass) of a styrene acrylic resin (trade name: Joncryl 96J, manufactured by BASF Japan Ltd., solid content concentration: 30% by mass) were used. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0099] (Example 19) As shown in Table 5, in this example, as the binder, 7% by mass (in terms of solid content: 2.7% by mass) of an anionic polyolefin resin emulsion (trade name: Hardlen (registered trademark) NZ-1004, manufactured by Toyobo Co., Ltd., solid content concentration: 30% by mass) and 3% by mass (in terms of solid content: 0.3% by mass) of a styrene acrylic resin (trade name: Joncryl 96J, manufactured by BASF Japan Ltd., solid content concentration: 30% by mass) were used. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0100] (Example 20) As shown in Table 5, in this example, the content of the polyolefin resin emulsion was changed to 3% by mass (in terms of solid content: 0.9% by mass), and the content of water was changed to 45% by mass. Otherwise, in the same manner as in Example 2, the aqueous ink composition according to this example was prepared.

[0101] (Example 21) As shown in Table 5, in this example, the content of the polyolefin resin emulsion was changed to 5% by mass (in terms of solid content: 0.9% by mass), and the content of water was changed to 43% by mass. Otherwise, in the same manner as in Example 2, an aqueous ink composition according to this example was prepared.

[0102] (Example 22) As shown in Table 5, in this example, the content of the polyolefin resin emulsion was changed to 15% by mass (in terms of solid content: 0.9% by mass), and the content of water was changed to 33% by mass. Otherwise, in the same manner as in Example 2, an aqueous ink composition according to this example was prepared.

[0103]

Table 5

[0104] (Spoutability) Using the aqueous ink compositions of Examples 1 to 22 and Comparative Examples 1 to 8, printing was performed by an inkjet method on inkjet premium paper (trade name: Next-IJ, manufactured by Nippon Paper Industries Co., Ltd.). Specifically, printing was performed by a single-pass method using an inkjet printer (trade name: PX-105, manufactured by Epson Corporation). The printing was carried out in an environment of a temperature of 25°C and a relative humidity of 60%. Thereafter, hot air at a temperature of 80°C was directly applied for 10 minutes to sufficiently dry the printed surface. Thereby, samples according to each example and each comparative example were prepared. Thereafter, the spoutability of the ink layer of each sample was evaluated. The results are shown in Tables 1 to 5.

[0105] Note that the evaluation of spoutability was carried out using the following criteria. ○: Can be ejected without problems △: Slight printing blur occurs ×: Ejection is impossible or significant printing blur occurs

[0106] (Printing density) Similar to the case of evaluating the ejection property, printing was performed by an inkjet method on inkjet premium paper using the aqueous ink compositions of Examples 1 to 22 and Comparative Examples 1 to 8, respectively. Thereby, samples according to each example and each comparative example were produced.

[0107] Subsequently, the image density (print density) of the printed image was measured with a reflection densitometer (trade name: Exact, manufactured by Video Jet Xrite Co., Ltd.). The measurement was carried out by measuring the image density for 10 randomly selected regions in the printed image, and the arithmetic mean value of the obtained measurement values was taken as the print density of the evaluation target. The results are shown in Tables 1 to 5.

[0108] (Results) As can be seen from Examples 1 to 4, as the surfactant, all of the acetylene diol-based surfactant (A), the acetylene diol-based surfactant (B), and the ethylene oxide adduct of acetylene diol (C) are contained, and in the aqueous ink compositions of Examples 1 to 4 where the ratio of the contents of these surfactants is in the range of 1.6:1:1 to 3:1:1, it was confirmed that the ejection property is good and the decrease in the print density of the printed image is also suppressed (see Table 1). Also, as can be seen from Example 5, even when an alcohol alkoxylate is further contained as a surfactant in addition to these three components of surfactants, it was confirmed that the ejection property and the print density are excellent (see Table 1). On the other hand, as in Comparative Examples 3 to 8, when all of the acetylene diol-based surfactant (A), the acetylene diol-based surfactant (B), and the ethylene oxide adduct of acetylene diol (C) are not simultaneously contained as the surfactant, or even when all of these three components of surfactants are contained as in Comparative Examples 1 and 2, when the ratio of the contents is outside the range of 1.6:1:1 to 3:1:1, ejection failure occurred, and it was also confirmed that the print density decreased in some of the comparative examples (see Table 2).

[0109] Also, as can be seen from Examples 6 to 10, when triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, or propylene glycol monopropyl ether is used as the penetrant, when diethylene glycol is used as the water-soluble organic solvent, and when a resin-dispersed black pigment is used as the coloring material, good ejectability is exhibited and it has been confirmed that printing can be performed with a high printing density (see Table 3).

[0110] Furthermore, as can be seen from Examples 11 to 19, when a styrene acrylic resin, a styrene maleic acid resin, a nonionic polyolefin, or a polyurethane resin is used as the binder, and when an anionic polyolefin resin emulsion and a styrene acrylic resin are used in combination, good ejectability is exhibited and it has been confirmed that printing can be performed with a high printing density (see Tables 4 and 5). Also, as can be seen from Examples 20 to 22, when an anionic polyolefin resin emulsion is used as the binder and its content is changed to 3% by mass, 5% by mass, or 15% by mass, good ejectability is exhibited and it has been confirmed that printing can be performed with a high printing density (see Table 5).

Claims

1. An aqueous inkjet ink composition comprising at least a colorant, a surfactant, a binder, and an aqueous medium, The surfactant is The HLB is in the range of 1 to 4, and the acetylene diol surfactant (A) represented by the chemical formula (CH ３ ), ２ CHCH ２ C(CH ３ )(OH)CCC(CH ３ )(OH)CH ２ CH(CH ３ ), ２ and The HLB is in the range of 10 to 15, and the chemical formula is R １ C(CH ３ )(OH)CCC(CH ３ )(OH)R ２ (wherein R １ and R ２ each independently represent an alkyl group having 1 to 5 carbon atoms), and an acetylene diol-based surfactant (B) represented by the following formula: It has an HLB in the range of 10 to 15 and the chemical formula (CH ３ ) ２ CHCH ２ C(CH ３ ) (OCH ２ CH ２ ) ｎ OCCCC (CH ３ ) (OCH ２ CH ２ ) ｍ OHCH ２ CH (CH ３ ) ２ (wherein m and n are integers satisfying 0.5≦m≦25, 0.5≦n≦25, and 1≦m+n≦40), Including, The aqueous inkjet ink composition has a content ratio of the acetylenic diol surfactant (A), the acetylenic diol surfactant (B), and the ethylene oxide adduct of acetylenic diol (C) of the acetylenic diol surfactant (A):the acetylenic diol surfactant (B):the ethylene oxide adduct of acetylenic diol (C) in the range of 1.6:1:1 to 3:1:1 on a mass basis.

2. The aqueous inkjet ink composition according to claim 1, wherein the surfactant further comprises an alcohol alkoxylate.

3. 3. The aqueous inkjet ink composition according to claim 1, wherein the aqueous medium contains polyoxyethylene glycol having an added mole number of ethylene oxide in the range of 2 to 4.

4. 4. The aqueous inkjet ink composition according to claim 1, wherein the coloring material comprises at least one of a cyan pigment, a magenta pigment, a yellow pigment, and a black pigment.

5. It also contains moisturizers, 5. The aqueous inkjet ink composition according to claim 1, wherein the humectant contains a trihydric or higher polyhydric alcohol.

6. Further comprising a penetration control agent, 6. The aqueous inkjet ink composition according to claim 1, wherein the penetration control agent comprises at least one of a glycol solvent having 2 to 5 carbon atoms and a heterocyclic compound.

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