JP2023019633A - Aqueous ink composition for inkjet - Google Patents

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

In conventional water-based ink compositions for inkjet (hereinafter sometimes referred to as "water-based ink compositions"), in order to improve the printing density when printing on recording media such as plain paper and high-quality plain paper, , increasing the content ratio of the pigment contained in the water-based ink composition. In order to improve the permeability of the water-based ink composition to the recording medium, various solvents are also added. Furthermore, by adding a surfactant to the water-based ink composition, the wettability of the water-based ink composition inside the nozzles of the inkjet head is appropriately controlled to improve the ejection property of the water-based ink composition. ing.

Examples of surfactants added to the water-based ink composition include silicon-based surfactants, fluorine-based surfactants, and acetylenediol-based surfactants. For example, Patent Document 1 describes that an aqueous ink composition having excellent ejection stability and the like can be provided by including an acetylenic diol-based surfactant in the aqueous ink composition.

However, even if these surfactants are used, there are cases where sufficient wetting of the inside of the nozzles of the inkjet head is insufficient. In that case, for example, the meniscus of the ink liquid surface of the water-based ink composition is drawn too much into the nozzle, making it difficult to maintain an appropriate shape. As a result, there is a problem that ejection failure of the water-based ink composition occurs during printing by an inkjet method, and blurring occurs in the printed image. It is also conceivable to improve such ejection failure by increasing the content of the surfactant, but in that case the surface tension of the water-based ink composition decreases, resulting in the water-based ink composition flowing inside the nozzle. Things get too wet. As a result, an appropriate ink meniscus is not formed in the nozzle, and the water-based ink composition drips from the nozzle. In addition, by increasing the content of the surfactant, the permeability of the water-based ink composition to the recording medium increases, resulting in diffraction and scattering of light in the printed image, which remains on the surface layer of the recording medium. Since the amount of the coloring material to be used is also reduced, there is also a problem that the printing density of the printed image is lowered.

Japanese Patent No. 6663069

The present invention has been made in view of the above-mentioned problems, and its object is to enable good continuous printability by improving the ejection property during printing with an inkjet method, and to achieve a good print density. An object of the present invention is to provide an inkjet water-based ink composition that enables image printing.

In order to solve the above problems, 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. , said surfactant has an HLB in the range of 1 to 4 and has the formula (CH ₃ ) ₂ CHCH ₂ C(CH ₃ )(OH)CCC(CH ₃ )(OH)CH ₂ CH(CH ₃ ) ₂ and an acetylenediol-based surfactant (A) represented by the formula 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 acetylenediol-based surfactant (B) represented by the formula (CH ₃ ) ₂ CHCH ₂ C(CH ₃ )(OCH ₂ CH ₂ ) _n OHCCC(CH ₃ )(OCH ₂ CH ₂ ) _m OHCH ₂ CH(CH ₃ ) ₂ (wherein m and n are 0.5≦ an integer satisfying m ≤ 25, 0.5 ≤ n ≤ 25, 1 ≤ m + n ≤ 40.) and an ethylene oxide adduct (C) of acetylenediol represented by A), the ratio of the contents of the acetylenediol-based surfactant (B) and the ethylene oxide adduct of the acetylenediol (C) is, on a mass basis, the acetylenediol-based surfactant (A): the acetylenediol-based surfactant Activator (B): ethylene oxide adduct (C) of acetylene diol is characterized in that the ratio is in the range of 1.6:1:1 to 3:1:1.

According to the above configuration, the surfactant includes an acetylenediol-based surfactant (A), an acetylenediol-based surfactant (B), and an ethylene oxide adduct of acetylenediol (C). By setting the content ratio of the surfactant in the range of 1.6:1:1 to 3:1:1 on a mass basis, the wettability of the water-based ink composition inside the nozzle of the inkjet head can be appropriately controlled. Range can be controlled. That is, according to the above configuration, the meniscus of the ink liquid surface of the water-based ink composition is prevented from being drawn into the nozzle too much, and the ejection property at the time of printing is improved, resulting in favorable continuous printing. make possible. It is also possible to prevent the water-based ink composition from excessively wetting the inside of the nozzle so that the meniscus of the ink liquid surface does not have an appropriate shape and the water-based ink composition falls from the nozzle and drips. can. Furthermore, according to the above configuration, it is not necessary to excessively increase the content of the surfactant in order to improve the wettability of the water-based ink composition inside the nozzle. This can prevent the water-based ink composition from penetrating excessively into the recording medium. As a result, the occurrence of light diffraction and scattering in the printed image can be reduced, and the coloring material can be left on the surface layer without excessively penetrating the recording medium, resulting in a decrease in the printing density of the printed image. can also be reduced or suppressed.

In the above configuration, it is preferable that the surfactant further contains an alcohol alkoxylate. As a result, it is possible to further improve the ejection property of the water-based ink composition from the nozzle, and to further suppress the decrease in the printing density of the printed image.

In the above configuration, the aqueous medium preferably contains polyoxyethylene glycol in which the number of added moles of ethylene oxide is in the range of 2 to 4. As a result, it is possible to further improve the ejection property of the water-based ink composition from the nozzle, and to further suppress the decrease in the printing density of the printed image.

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

In the above configuration, it is preferable that a humectant is further included, and the humectant contains a polyhydric alcohol having a valence of 3 or more. As a result, drying of the water-based ink composition can be prevented, and clogging in the vicinity of the nozzles of the inkjet head can be prevented or reduced. As a result, the jettability of the water-based ink composition can be further improved.

It is preferable that the composition further contains a penetration control agent, and that the penetration control agent contains at least one of a glycol solvent having 2 to 5 carbon atoms and a heterocyclic compound. This makes it possible to control the permeability of the water-based ink composition into the recording medium. For example, the coloring material does not excessively permeate the recording medium and remain on the surface layer, which reduces the print density of the printed image. can be suppressed.

According to the water-based ink composition for inkjet of the present invention, for example, compared with conventional surfactants such as silicon-based surfactants and fluorine-based surfactants, it has excellent ejection properties during printing by an inkjet method, and , it is possible to print an image with good density.

(Aqueous ink composition for inkjet)
The aqueous ink composition for inkjet (hereinafter referred to as "aqueous ink composition") according to the present embodiment will be described below.

The aqueous ink composition of the present embodiment contains at least a coloring material, a surfactant, a binder, and an aqueous medium. This water-based ink composition can be suitably used for printing by an inkjet system. Here, the term "inkjet method" as used herein means that an aqueous ink containing an aqueous ink composition is discharged as droplets from, for example, a known piezo inkjet head, and the droplets are applied to a recording medium. It means a printing method for fixing and forming a print image or the like. Details of the recording medium will be described later.

[Color material]
Colorants include pigments and dyes used in inkjet printing.

The pigment preferably contains at least one of a cyan pigment, a magenta pigment, a yellow pigment and a black pigment. Examples of inorganic pigments include titanium oxide, iron oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, ultramarine blue, Prussian blue, carbon black, graphite, calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. be done. Examples of organic pigments include azo-based pigments, phthalocyanine-based pigments, anthraquinone-based pigments, quinacridone-based pigments, thioindigo-based pigments, triphenylmethane lake-based pigments, and oxazine lake-based pigments. These pigments may be used alone or in combination of two or more. In addition, the pigment of this embodiment is not limited to the examples.

As the pigment, it is also possible to use a self-dispersed pigment or a resin-dispersed pigment. Among these pigments, self-dispersing pigments are preferred from the viewpoint of increasing print density (image density).

Self-dispersing pigments are pigments that chemically bond various functional groups to the surfaces of pigment particles, thereby dispersing them in an aqueous medium without using pigment dispersants such as resins or surfactants. The pigment particles used for the self-dispersion pigment are not particularly limited, and any of the above inorganic pigments and organic pigments can be used. Moreover, the functional group is not particularly limited, and examples thereof include a hydroxyl group, a quinone group, a carbonyl group, a carboxyl group, a phosphoric acid group, a sulfone group, an amine group, or salts thereof.

Specific examples of self-dispersing pigments include self-dispersing carbon black, self-dispersing phthalocyanine, self-dispersing quinacridone, and self-dispersing azo.

A resin-dispersed pigment is a pigment that can be dispersed in an aqueous medium using a resin dispersant that is soluble in the aqueous medium. The pigment used for the resin-dispersed pigment is not particularly limited, and any of the above inorganic pigments and organic pigments can be used. The resin dispersant is not particularly limited, and examples thereof include polyvinyl alcohols, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, and acrylic acid-acrylic acid ester copolymer. , 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, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, salts thereof, and the like. These resin dispersants may be used alone or in combination of two or more.

The ratio of the pigment particles to the resin dispersant in the resin-dispersed pigment is not particularly limited, and can be appropriately set as required.

Specific examples of resin-dispersed pigments include resin-dispersed carbon black, resin-dispersed phthalocyanine, resin-dispersed quinacridone, and resin-dispersed azo.

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, and the like. mentioned. The chlorophyllins pigment is not particularly limited, and examples thereof include sodium iron chlorophyllin, sodium copper chlorophyllin, sodium chlorophyllin and the like. Moreover, the natural coloring matter is not particularly limited, and examples thereof include cochineal coloring matter, cacao coloring matter, caramel coloring matter and the like.

The content of the coloring material affects image density, storage stability of the water-based ink composition, viscosity, pH, and the like. Therefore, it is preferable to appropriately set the content of the coloring material in consideration of these points. More specifically, the content of the coloring material is preferably in the range of 1% by mass to 10% by mass in terms of solid content, more preferably in the range of 3% by mass to 10% by mass, based on the total mass of the aqueous ink composition. A range of 4.5% to 7% by weight is particularly preferred. When the content of the coloring material is 1% by mass or more, the reduction in image density can be suppressed. On the other hand, if the content of the coloring material is 10% by mass or less, it is possible to prevent deterioration of ejection performance due to clogging of nozzles.

[Surfactant]
The surfactant includes at least an acetylenediol-based surfactant (A), an acetylenediol-based surfactant (B), and an ethylene oxide (EO) adduct of acetylenediol (C).

Acetylene diol-based surfactant (A) is (CH ₃ ) ₂ CHCH ₂ C(CH ₃ )(OH)CCC(CH ₃ ) A compound represented by (OH) _CH2CH ( _CH3 ) ₂ . Commercially available products of the acetylenediol-based surfactant (A) are not particularly limited. Co., Ltd.) and the like.

Acetylene diol-based surfactant (B) has an HLB of 10 to 15, preferably 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.). In this specification, when a range of carbon number is expressed, the range means to include all integer carbon numbers 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.

The alkyl group may be either a straight chain alkyl group or a branched chain alkyl group. More specifically, the alkyl group is a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group. mentioned. R ¹ and R ² may be the same or different.

Commercial products of the acetylene diol-based surfactant (B) are not particularly limited, and examples thereof include Surfynol 465 (HLB value: 13) (trade name, manufactured by Air Products Co., Ltd.).

The EO adduct (C) of acetylenediol is an adduct in which a predetermined number of added moles of ethylene oxide groups (EO) are added to acetylenediol. More specifically, the EO adduct of acetylenediol (C) has an HLB in the range of 10 to 15, preferably 12 to 14, and has the formula (CH ₃ ) ₂ CHCH ₂ C(CH ₃ )(OCH ₂ CH ₂ ) _n OHCCC(CH ₃ )(OCH ₂ CH ₂ ) _m OHCH ₂ CH(CH ₃ ) ₂ (wherein m and n are 0.5≦m≦25, 0.5≦n≦25, 1≦ is an integer that satisfies m+n≦40).

The commercial product of the EO adduct (C) of acetylenediol is not particularly limited, and examples thereof include Olphine (registered trademark) E1010 (trade name, manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 13).

In this specification, the HLB value is the HLB value according to the Griffin method, and means the value obtained by the following formula.
HLB value = 20 x (sum of formula weights of hydrophilic groups/molecular weight)
The HLB value is a value 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.

The content of the surfactant is preferably in the range of 0.1% by mass or more and 5% by mass or less, and 0.5% by mass or more and 4% by mass or less with respect to the total mass of the aqueous ink composition. It is more preferable to be within the range. By setting the content of the surfactant to 0.1% by mass or more, the meniscus of the ink liquid surface of the water-based ink composition is prevented from being drawn into the nozzle too much, and the ink-jet printing is improved. It improves the ejection property at the time of , and enables good continuous printing property. On the other hand, by setting the content of the surfactant to 5% by mass or less, the water-based ink composition is prevented from excessively wetting the inside of the nozzle, and the water-based ink composition is prevented from dripping from the nozzle. be able to. In addition, it is possible to suppress adverse effects on ejection of the water-based ink composition due to the insoluble matter of the surfactant and poor emulsification.

In addition, the content ratio of the acetylenediol-based surfactant (A), the acetylenediol-based surfactant (B), and the EO adduct of acetylenediol (C) is 1.6:1:1 to 3 on a mass basis. :1:1, preferably 2:1:1 to 3:1:1.

Further, the surfactant of the present embodiment may contain other surfactants. Other surfactants include, for example, alcohol alkoxylates. Containing an alcohol alkoxylate improves ejection properties during printing by an inkjet method, enables good continuous printing properties, and prevents reduction in print density. In addition, in the present invention, it is preferable not to contain a silicon-based surfactant and a fluorine-based surfactant as other surfactants.

The alcohol alkoxylate is not particularly limited, and examples thereof include alcohol ethoxylate, oleyl alcohol ethoxylate and the like. In addition, the alcohol alkoxylate is not particularly limited as a commercial product, and for example, Adekatol (registered trademark, manufactured by ADEKA Corporation), Conion (registered trademark, manufactured by Shin Nippon Rika Co., Ltd.), DYNWET (registered trademark, BYK Chemie Japan Co., Ltd.) manufactured by the company).

When an alcohol alkoxylate is contained in the surfactant, the content ratio of the alcohol alkoxylate to the total weight of the water-based ink composition is preferably in the range of 0.1 to 2.0, preferably 0.2. A range of ~1.0 is more preferred. By further containing the alcohol alkoxylate within the above range, it is possible to further improve the ejection property during printing by an ink jet system and further prevent the decrease in print density.

[Binder]
The binder preferably contains a polyolefin resin dispersion and at least one resin selected from the group consisting of styrene-acrylic acid resin, styrene-maleic acid resin and polyurethane resin. As a result, it is possible to improve the ejection property and print a printed image excellent in abrasion resistance and water resistance.

A 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, the polyolefin resin that is not soluble in water is prevented from settling. For example, when a powdery polyolefin resin is added to water, a composition in which the polyolefin resin settles without being dissolved in water is obtained. As a result, the composition cannot be ejected from an inkjet head, and printing by an inkjet method becomes difficult.

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

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

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. Moreover, it is also possible to use a commercial item as a polyolefin resin emulsion. Examples of such commercial products include Hardren (registered trademark) NZ-1004 (solid content concentration: 30% by mass), Hardren NZ-1015 (solid content concentration: 30% by mass) (manufactured by Toyobo Co., Ltd., commercial products Name), Arrow Base (registered trademark) DA-1010 (solid concentration: 25% by mass), Arrow Base DB-4010 (solid concentration: 25% by mass) (manufactured by Unitika Ltd., trade name), Superchron (registered trademark) E-415 (solid content concentration: 30% by mass), Superchron E-480T (solid content concentration: 30% by mass), Superchron E-604 (solid content concentration: 40% by mass) (above, Japan manufactured by Paper Manufacturing Co., Ltd., trade name) and the like.

Styrene-acrylic acid resin, styrene-maleic acid resin and polyurethane resin are optional components, and function as binders in the present embodiment. In this embodiment, these resins are not blended as a pigment dispersant.

The styrene-acrylic acid resin is not particularly limited. For example, as its constituent components, in its molecule, at least one styrene-based monomer component selected from the group consisting of styrene and its derivatives, (meth)acrylic acid and its derivatives and at least one acrylic monomer component selected from the group consisting of: Moreover, the styrene-acrylic acid resin may contain a monomer component other than the styrene-based monomer component and the acrylic acid-based monomer component. In this specification, the term "(meth)acrylic acid" includes not only "acrylic acid" but also "methacrylic acid".

The styrene-maleic acid resin is not particularly limited. For example, the group consisting of at least one styrenic monomer component selected from the group consisting of styrene and its derivatives and maleic acid and its derivatives in the molecule as its constituent components. and at least one maleic acid-based monomer component selected from. Moreover, the styrene-maleic acid resin may contain monomer components other than the styrene-based monomer component and the maleic acid-based monomer component.

The polyurethane resin is not particularly limited, and examples thereof include polymers containing polyisocyanate, polyol, or the like as constituent components.

In the present embodiment, the styrene acrylic acid resin, the styrene maleic acid resin and the polyurethane resin are 0.75% by mass or less, preferably 0.6% by mass in terms of solid content, based on the total mass of the water-based ink composition. Below, more preferably 0.3% by mass or less, particularly preferably 0% by mass, is blended. By setting the content of the styrene acrylic acid resin or the like to 0.75% by mass or less in terms of solid content, the film-forming temperature of the ink layer formed by printing with the water-based ink composition of the present embodiment becomes excessively high. can be suppressed. Thereby, maintenance of favorable dryness is achieved. In addition, scratch resistance can also be improved as compared with the case where only styrene-acrylic acid resin or the like is used. Further, for example, in styrene-acrylic acid resin and styrene-maleic acid resin, the ester bond in the molecule is easily hydrolyzed, and in polyurethane resin, the urethane bond in the molecule is easily hydrolyzed. Therefore, in a water-based ink composition containing a large amount of these resins, the ink layer printed using the water-based ink composition does not have good water resistance and solvent resistance. However, as in the present embodiment, by suppressing the content of the styrene-acrylic acid resin or the like to 0.75% by mass or less with respect to the total mass of the aqueous ink composition, the water resistance of the ink layer is reduced. can be suppressed or prevented.

Moreover, in the present embodiment, the binder preferably consists of only the polyolefin resin dispersion. As a result, the film-forming temperature of the ink layer formed from the water-based ink composition of the present embodiment can be reduced, the ink layer can be sufficiently dried even under normal drying conditions, and the abrasion resistance can be further improved. . Moreover, since it does not contain styrene-acrylic acid resin or the like, it is possible to further improve the water resistance of the ink layer.

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 in terms of solid content, based on the total mass of the aqueous ink composition. It is more than mass % and below 4.5 mass %. By setting the content of the polyolefin resin dispersion in terms of solid content to 1.2% by mass or more, good abrasion resistance can be maintained. By setting the content of the polyolefin resin emulsion to 6% by mass or less in terms of solid content, it is possible to maintain good dischargeability of the water-based ink composition from the inkjet head.

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

A mixed solution of water and a water-soluble organic solvent may also be used as the aqueous medium. The water-soluble organic solvent is not particularly limited, and specific examples include alcohols such as methyl alcohol, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-propyl alcohol, and isopropyl alcohol; Amides such as formamide and dimethylacetamide; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran, dioxane, ethylene glycol methyl ether, ethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl Ethers such as ether; 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, polyoxyethylene glycol having 2 to 4 moles of ethylene oxide added, more specifically diethylene glycol, is preferred from the viewpoint of improving the ejection property of the aqueous ink composition and preventing a decrease in print density. , triethylene glycol and tetraethylene glycol are preferred, diethylene glycol and triethylene glycol are more preferred, and triethylene glycol is particularly preferred. A water-soluble organic solvent can be used individually or in mixture of 2 or more types.

The content of the aqueous medium is not particularly limited, but is usually 5% by mass or more and 50% by mass or less, preferably 5% by mass or more and 45% by mass or less, relative to the total mass of the aqueous ink composition. 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 20:80 to 40:60. is more preferred, and a range of 30:70 to 40:60 is even more preferred.

[Other additives]
The water-based ink composition of the present embodiment may contain other additives as long as the effects of the present invention are not impaired. Additives include moisturizing agents, penetrating (controlling) agents, pigment dispersants, water-soluble resins, pH adjusters, chelating agents, preservatives, viscosity adjusters, antifoaming agents, dispersion stabilizers, reduction inhibitors, oxidation inhibitors and the like. Except for the moisturizing agent and the penetrating agent, the content of these additives is not particularly limited, and can be set as appropriate (the content of the moisturizing agent and the penetrating agent will be described later).

Moisturizers include, for example, trihydric or higher polyhydric alcohols. The trihydric or higher polyhydric alcohol is not particularly limited, and examples thereof include polyethylene glycol, glycerin, polyglycerin, and the like. Among these, high-boiling water-soluble polyhydric alcohols such as glycerin and polyglycerin are preferable from the viewpoint of preventing drying of the nozzle surface. These moisturizing agents can be used alone or in combination of two or more.

The amount of the moisturizing agent added is preferably in the range of 1% by mass or more and 20% by mass or less, and is in the range of 5% by mass or more and 15% by mass or less with respect to the total mass of the aqueous ink composition. is more preferred. By setting the content of the humectant to 1% by mass or more, clogging in the vicinity of the nozzle of the inkjet head can be prevented during printing by an inkjet method, and the ejection performance can be further improved, particularly 5% by mass. The effect is more remarkable when it is above. On the other hand, when the content of the humectant is 20% by mass or less, the viscosity of the water-based ink composition can be appropriately controlled.

Penetration (controlling) agents include, for example, glycol-based solvents having 2 to 5 carbon atoms, heterocyclic compounds, and the like. The glycol-based 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 (controlling) agents can be used alone or in combination of two or more.

The amount of the penetrating (controlling) agent added is preferably in the range of 1% by mass or more and 20% by mass or less, and in the range of 5% by mass or more and 15% by mass or less, relative to the total mass of the aqueous ink composition. is more preferable. By setting the content of the penetration (controlling) agent to 1% by mass or more, sufficient penetration of the water-based ink composition into the recording medium can be maintained. Remarkable. On the other hand, by setting the content of the penetrating (controlling) agent to 20% by mass or less, the coloring material does not excessively permeate the recording medium and remain on the surface layer, thereby suppressing a decrease in the printing density of the printed image. can do. Moreover, it is possible to prevent the viscosity of the water-based ink composition from becoming excessively high, and to maintain the stability of the water-based ink composition. These effects are particularly remarkable at 15% by mass or less.

When the above-described self-dispersing pigment or resin-dispersing pigment is used as the coloring material, the addition of the pigment dispersant to the water-based ink composition can be omitted. When using a pigment other than the self-dispersing pigment and the resin-dispersing pigment, it is preferable to add a pigment dispersant to the water-based ink composition. The pigment dispersant is not particularly limited, and any known dispersant can be used as appropriate.

[others]
The viscosity of the water-based 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 ejecting from an inkjet nozzle, considering ejection properties from the inkjet nozzle. is more preferred. By setting the viscosity of the water-based ink composition within the above numerical range, it is possible to further suppress the occurrence of clogging in the ink jet nozzle and maintain good ejection properties. The viscosity of the water-based ink composition can be obtained, for example, by measuring with a viscometer (trade name: VISCOMATE MODEL VM-10A, manufactured by Sekonic Co., Ltd.) at a measurement temperature of 25°C.

The aqueous ink composition of the present embodiment can be used as an aqueous ink composition capable of forming an ink layer on the surface of a recording medium to form a printed image. Further, the water-based ink composition of the present embodiment can be used as the water-based inkjet ink itself, in addition to being included in the water-based inkjet ink that is the final product.

(Method for producing water-based ink composition for inkjet)
The water-based ink composition of the present embodiment can be produced by mixing the colorant, surfactant, binder, water-based medium, and other optional additives in any order. For example, when a pigment is used as the colorant, the pigment, surfactant, binder and aqueous medium are mixed at once, and the mixed liquid is subjected to dispersion treatment using an ordinary dispersing machine. The dispersion time at this time is not particularly limited, but is preferably set so that the average dispersed particle diameter of the pigment in the dispersed state is within a specific range.

The dispersing machine used in dispersing the pigment is not particularly limited as long as it is a commonly used dispersing machine. Specific examples include ball mills, roll mills, sand mills, bead mills, paint shakers and nanomizers.

Subsequently, the dispersion liquid obtained by the dispersion treatment is further mixed with the other additives described above by an appropriate method, thereby obtaining an aqueous ink composition using a pigment as a coloring material.

The method for mixing each material is not particularly limited, and for example, the materials can be sequentially added to a vessel equipped with a stirring device such as a disper, mechanical stirrer, or magnetic stirrer, and stirred and mixed. Moreover, the filtration method is not particularly limited, and for example, centrifugal filtration, filter filtration, or the like can be employed.

(recoding media)
The recording medium is not particularly limited, and conventionally known media can be employed. Specific examples include printing paper such as coated paper, art paper, and matte paper, and films.

Preferred embodiments of the present invention will be described in detail below. However, the materials and contents described in the following examples are not intended to limit the scope of the present invention unless otherwise specified.

(Example 1)
As shown in Table 1, 40% by mass (solid content conversion: 6% by mass) of self-dispersing black pigment (solid content concentration: 15% by mass) and 10% by mass (solid content conversion: 1.5% by mass) Anionic polyolefin resin emulsion (trade name: Hardren (registered trademark) NZ-1004, manufactured by Toyobo Co., Ltd., solid content concentration: 30% by mass) and 0.8% by mass of acetylene diol surfactant (A) (product Name: Surfynol (registered trademark) 104PA, manufactured by Air Products Co., Ltd.), 0.5% by mass of acetylene diol-based surfactant (B) (trade name: Surfynol 465, manufactured by Air Products Co., Ltd.), and 0 5% by mass of EO adduct (C) of acetylenediol (trade name: Olfin (registered trademark) E1010, manufactured by Nissin Chemical Industry Co., Ltd.) and 5% by mass of diethylene glycol monobutyl ether (trade name: Hisolve DB, Toho Kagaku Kogyo Co., Ltd.), 5% by mass of triethylene glycol, and 38.2% by mass of water were mixed to prepare an aqueous ink composition according to this example.

(Example 2)
As shown in Table 1, in this example, the content of the acetylenediol-based surfactant (A) was changed to 1% by mass, and the content of water was changed to 38% by mass. A water-based ink composition according to this example was prepared in the same manner as in Example 1 except for these.

(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 content of water was changed to 37.8% by mass. A water-based ink composition according to this example was prepared in the same manner as in Example 1 except for these.

(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 content of water was changed to 37.5% by mass. A water-based ink composition according to this example was prepared in the same manner as in Example 1 except for these.

(Example 5)
As shown in Table 1, in this example, 0.5% by mass of alcohol alkoxylate (trade name: DYNWET (registered trademark) 800N, manufactured by BYK-Chemie Japan Co., Ltd.) was added as a surfactant. , the water content was changed to 37.5% by mass. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for these.

(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 content of water was changed to 38.5% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

(Comparative example 2)
As shown in Table 2, in this comparative example, the content of the acetylenediol-based surfactant (A) was changed to 2% by mass, and the content of water was changed to 37% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

(Comparative Example 3)
As shown in Table 2, in this comparative example, only 1% by mass of acetylenediol-based surfactant (A) was added as a surfactant, and the water content was changed to 39% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

(Comparative Example 4)
As shown in Table 2, in this comparative example, only 2% by mass of the acetylenediol-based surfactant (B) was added as the surfactant, and the water content was changed to 38% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

(Comparative Example 5)
As shown in Table 2, in this comparative example, only 2% by mass of EO adduct (C) of acetylenediol was added as a surfactant, and the water content was changed to 38% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

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

(Comparative Example 7)
As shown in Table 2, in this comparative example, 1% by mass of acetylenediol-based surfactant (A) and 0.5% by mass of acetylenediol-based surfactant (B) were used as surfactants. was added, and the water content was changed to 38.5% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

(Comparative Example 8)
As shown in Table 2, in this comparative example, as surfactants, 0.5% by mass of an acetylenediol-based surfactant (B) and 0.5% by mass of an EO adduct of acetylenediol (C ) was added, and the water content was changed to 39% by mass. A water-based ink composition according to this comparative example was prepared in the same manner as in Example 1 except for these.

(Example 6)
As shown in Table 3, in this example, the penetrant was changed to triethylene glycol dimethyl ether. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 7)
As shown in Table 3, in this example, the penetrant was changed to triethylene glycol monomethyl ether. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 8)
As shown in Table 3, in this example, the penetrant was changed to propylene glycol monopropyl ether. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 9)
As shown in Table 3, in this example, the water-soluble organic solvent was changed to diethylene glycol. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 10)
As shown in Table 3, in this example, the coloring material was changed to 40% by mass (solid content conversion: 6.4% by mass) of resin-dispersed black pigment (solid content concentration: 16% by mass). . A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 11)
As shown in Table 4, in this example, the binder was 10% by mass (in terms of solid content: 3% by mass) of styrene acrylic acid resin (trade name: Joncryl 96J, manufactured by BASF Japan Ltd., solid content concentration : 30% by mass). A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 12)
As shown in Table 4, in this example, the binder was 10% by mass (in terms of solid content: 3% by mass) of styrene maleic acid resin (trade name: SMA 1440H, manufactured by TOTAL Corporation, solid content concentration: 30 mass %). A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 13)
As shown in Table 4, in this example, the binder was changed to 10% by mass nonionic polyolefin resin (trade name: AQUACER (registered trademark) 515, manufactured by BYK-Chemie Japan). A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 14)
As shown in Table 4, in this example, the binder was changed to 10% by mass nonionic polyolefin resin (trade name: AQUACER (registered trademark) 531, manufactured by BYK-Chemie Japan). A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 15)
As shown in Table 4, in this example, the binder was changed to 10% by mass nonionic polyolefin resin (trade name: AQUACER (registered trademark) 551, manufactured by BYK-Chemie Japan). A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 16)
As shown in Table 4, in this example, the binder was changed to 10% by mass polyurethane resin (trade name: WBR-016U, manufactured by Taisei Fine Chemical Co., Ltd.). A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 17)
As shown in Table 5, in this example, an anionic polyolefin resin emulsion (trade name: Hardren (registered trademark) NZ-1004, Toyobo Co., Ltd., solid content concentration: 30% by mass) and 1% by mass (solid content conversion: 0.3% by mass) styrene acrylic acid resin (trade name: Joncryl 96J, BASF Japan Co., Ltd., solid content concentration: 30% by mass) was used. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 18)
As shown in Table 5, in this example, 8% by mass (in terms of solid content: 2.7% by mass) of an anionic polyolefin resin emulsion (trade name: Hardren (registered trademark) NZ-1004, Toyobo Co., Ltd., solid content concentration: 30% by mass) and 2% by mass (solid content conversion: 0.3% by mass) styrene acrylic acid resin (trade name: Joncryl 96J, BASF Japan Co., Ltd., solid content concentration: 30% by mass) was used. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 19)
As shown in Table 5, in this example, 7% by mass (in terms of solid content: 2.7% by mass) of an anionic polyolefin resin emulsion (product name: Hardren (registered trademark) NZ-1004, Toyobo Co., Ltd., solid content concentration: 30% by mass) and 3% by mass (solid content conversion: 0.3% by mass) styrene acrylic acid resin (trade name: Joncryl 96J, BASF Japan Co., Ltd., solid content concentration: 30% by mass) was used. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for the above.

(Example 20)
As shown in Table 5, in this example, the content of the polyolefin resin emulsion was changed to 3% by mass (converted to solid content: 0.9% by mass), and the content of water was changed to 45% by mass. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for these.

(Example 21)
As shown in Table 5, in this example, the content of the polyolefin resin emulsion was changed to 5% by mass (converted to solid content: 0.9% by mass), and the content of water was changed to 43% by mass. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for these.

(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. A water-based ink composition according to this example was prepared in the same manner as in Example 2 except for these.

(Ejectability)
Using the water-based ink compositions of Examples 1 to 22 and Comparative Examples 1 to 8, ink jet printing was performed on high quality ink jet paper (trade name: Next-IJ, manufactured by Nippon Paper Industries Co., Ltd.). Specifically, an inkjet printer (trade name: PX-105, manufactured by Epson Corporation) was used for printing in a single pass (one pass) method. The printing was performed under an environment of 25° C. temperature and 60% relative humidity. After that, hot air at a temperature of 80° C. was directly applied for 10 minutes to sufficiently dry the printed surface. Thus, samples according to each example and each comparative example were produced. After that, the ejection properties of the ink layer of each sample were evaluated. The results are shown in Tables 1-5.

In addition, the following criteria were used for the evaluation of dischargeability.
○: Ejection is possible without problems △: Printing is slightly disturbed ×: Ejection is not possible or printing is greatly disturbed

(Print density)
In the same manner as in the evaluation of jettability, each of the water-based ink compositions of Examples 1 to 22 and Comparative Examples 1 to 8 was used to print on high-quality inkjet paper by an inkjet method. Thus, samples according to each example and each comparative example were produced.

Subsequently, the image density (printing density) of the printed image was measured with a reflection densitometer (trade name: Exact, manufactured by Videojet X-Rite Co., Ltd.). For the measurement, the image density was measured for each of 10 randomly selected regions in the printed image, and the arithmetic average value of the obtained measured values was used as the print density to be evaluated. The results are shown in Tables 1-5.

(result)
As can be seen from Examples 1 to 4, the surfactant contains all of the acetylenediol-based surfactant (A), the acetylenediol-based surfactant (B), and the ethylene oxide adduct of acetylenediol (C), and , The water-based ink compositions of Examples 1 to 4, in which the content ratio of these surfactants is in the range of 1.6:1:1 to 3:1:1, have good jettability and printability. It was confirmed that the decrease in print density of the image was also suppressed (see Table 1). Further, as can be seen from Example 5, it was confirmed that, in addition to these three component surfactants, even when an alcohol alkoxylate was added as a surfactant, the jettability and print density were excellent. (See Table 1). On the other hand, as in Comparative Examples 3 to 8, as surfactants, an acetylenediol-based surfactant (A), an acetylenediol-based surfactant (B), and an ethylene oxide adduct of acetylenediol (C) were all added at the same time. Even if it does not contain, or if it contains all of these three component surfactants as in Comparative Examples 1 and 2, the content ratio is in the range of 1.6: 1: 1 to 3: 1: 1. It was confirmed that when the ink was out of alignment, ejection failure occurred, and print density decreased in some of the comparative examples (see Table 2).

Further, as can be seen from Examples 6 to 10, when triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, or propylene glycol monopropyl ether was used as the penetrant, when diethylene glycol was used as the water-soluble organic solvent, and the colorant It was confirmed that even when a resin-dispersed black pigment was used as the ink, good jettability was exhibited and printing was possible with a high print density (see Table 3).

Furthermore, as can be seen from Examples 11 to 19, when styrene acrylic acid resin, styrene maleic acid resin, nonionic polyolefin or polyurethane resin is used as a binder, and anionic polyolefin resin emulsion and styrene acrylic acid resin are used together It was confirmed that good ejection properties were exhibited and printing was possible with a high print density even in the case where the ink was applied (see Tables 4 and 5). Further, as can be seen from Examples 20 to 22, even when an anionic polyolefin resin emulsion is used as a binder and the content thereof is changed to 3% by mass, 5% by mass or 15% by mass, good ejection properties are exhibited. It was also confirmed that printing can be performed at a high print density (see Table 5).

Claims (6)

An inkjet aqueous ink composition comprising at least a coloring material, a surfactant, a binder, and an aqueous medium,
The surfactant is
Acetylene diol-based interface having HLB in the range of 1 to 4 and represented by the chemical formula (CH ₃ ) ₂ CHCH ₂ C(CH ₃ )(OH)CCC(CH ₃ )(OH)CH ₂ CH(CH ₃ ) ₂ an active agent (A);
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 have 1 to 1 carbon atoms). represents an alkyl group of 5.) and an acetylenediol-based surfactant (B) represented by
HLB is in the range of 10-15 and has the chemical formula (CH ₃ ) ₂ CHCH ₂ C(CH ₃ )(OCH ₂ CH ₂ ) _n OHCCC(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, 1 ≤ m + n ≤ 40.) Ethylene oxide adduct (C) of acetylenediol represented by and,
including
The ratio of the contents of the acetylenediol-based surfactant (A), the acetylenediol-based surfactant (B), and the ethylene oxide adduct of the acetylenediol (C) is such that the acetylenediol-based surfactant ( A): A water-based inkjet ink composition wherein the acetylenediol-based surfactant (B): ethylene oxide adduct (C) of the acetylenediol is in the range of 1.6:1:1 to 3:1:1. 2. The aqueous ink composition for inkjet according to claim 1, wherein the surfactant further comprises an alcohol alkoxylate. 3. The aqueous ink composition for inkjet according to claim 1, wherein the aqueous medium contains polyoxyethylene glycol in which the number of added moles of ethylene oxide is in the range of 2 to 4. The water-based ink composition for inkjet according to any one of claims 1 to 3, wherein the coloring material contains at least one of a cyan pigment, a magenta pigment, a yellow pigment and a black pigment. It also contains a moisturizer,
The aqueous ink composition for inkjet according to any one of claims 1 to 4, wherein the humectant contains a trihydric or higher polyhydric alcohol. further comprising a penetration control agent,
The water-based ink composition for inkjet according to any one of claims 1 to 5, wherein the permeation control agent contains at least one of a glycol-based solvent having 2 to 5 carbon atoms and a heterocyclic compound.