JP2022112190A - Pigment dispersion for inkjet ink, inkjet ink and printed matter - Google Patents

Abstract

To provide an inkjet ink having excellent adhesion to various base materials such as a plastic substrate, blocking resistance, scratch resistance and ink dischargeability during inkjet printing.SOLUTION: There are provided: an inkjet pigment dispersion which comprises a dispersant (A), a binder resin (B), a pigment (C) and water (D), wherein the dispersant (A) contains at least a resin (A1) having a constituent unit (a1) derived from an acid group-containing monomer, in the resin (A1), a part or all of the acid groups in the constituent unit (a1) are neutralized with ammonia and the binder (B) contains a crosslinked acrylic resin (B1); an inkjet ink using the inkjet pigment dispersion; and a printed matter printed with the inkjet ink.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to pigment dispersions used for aqueous inkjet ink applications, aqueous inkjet inks prepared using the pigment dispersions, and printed matter inkjet-printed using the inkjet inks.

In addition to the viewpoint of sustainability against the backdrop of worsening air pollution caused by VOCs and the global expansion of global warming, there is a movement to shift away from petroleum resources due to concerns about occupational safety and health and flammability and explosion, and the use of organic solvents. Regulations on their use are becoming more and more stringent. Therefore, in the printing ink industry, water-based inks are being developed by replacing the organic solvent in solvent-based printing inks with water, and the development and improvement of water-based inks are also desired for inkjet inks.

On the other hand, due to population growth, rising income levels, and changes in distribution systems, the consumption of plastic film packaging is on the rise worldwide, and along with this, the production volume of packaging ink is increasing year by year. Traditionally, solvent-based flexographic inks and solvent-based gravure inks were the mainstream for film package printing. However, since these printing methods require platemaking, there is a problem that costs increase and it takes time to print. Therefore, even in film package printing, there is a growing demand for inkjet printing that does not require platemaking and enables on-demand printing.

However, compared to solvent-based inkjet inks, water-based inkjet inks are still insufficient in terms of adhesion to substrates such as films, anti-blocking properties associated with set-off of printed patterns, and ink ejection properties from inkjet heads. was there. In particular, the problems of adhesion and anti-blocking properties were more pronounced when the base material was a film base material.
In relation to the problem of ink jetting, which is a problem specific to inkjet printing, nozzle clogging can occur when the ink dries at the jetting part of the inkjet head during the time when ink is not jetted during inkjet printing (open time). Are known. Inkjet inks are also desired to have excellent ink resolubility that can reduce the occurrence of nozzle clogging.

Further, in the inkjet ink for use as a film substrate, scratch resistance is a property that is preferably provided. In printing on film packages, reverse printing, in which printing is performed on the back side of the film substrate, is the mainstream, but front printing, in which printing is performed on the surface of the film substrate, is faster in terms of printing and processing speed, resulting in lower productivity and lower costs. Surface printing is more advantageous when emphasizing . However, in surface printing, the printed surface is in contact with the external environment without the mediation of the base material, so the printed surface and the ink itself are required to have high scratch resistance. Inkjet inks that have scratch resistance in addition to the properties described above can be used not only for reverse side printing but also for front side printing, increasing versatility.

Japanese Patent Application Laid-Open No. 2019-196423

Patent Document 1 discloses an inkjet ink that is excellent in water resistance and alcohol resistance and is capable of film printing. It is characterized by having a Tg and an acid value of In Patent Document 1, solvent resistance is evaluated by rubbing with a cotton swab moistened with a solvent, and it can be seen that the structure of Patent Document 1 provides a certain degree of scratch resistance. However, Patent Document 1 does not evaluate ink ejection properties, adhesion properties, and anti-blocking properties. In addition, it is desired to further improve the abrasion resistance.

The problem to be solved by the present invention is to provide an inkjet ink that has excellent adhesion to various substrates such as plastic substrates, blocking resistance, abrasion resistance, and ink ejection property during inkjet printing, and a It is an object of the present invention to provide an inkjet pigment dispersion obtained by the above-described inkjet pigment dispersion, and a printed matter subjected to inkjet printing with the inkjet ink.

As a result of intensive research to solve the above problems, the present inventors neutralized some or all of the acid groups in the dispersion resin with ammonia, and further developed a pigment using a crosslinked acrylic resin as a binder. The inventors have found that the problem can be solved by the dispersion, and completed the present invention.

Specifically, the present invention relates to the following inventions.
(1) containing a dispersant (A), a binder resin (B), a pigment (C), and water (D),
The dispersant (A) contains at least a resin (A1) having a structural unit (a1) derived from an acid group-containing monomer,
In the resin (A1), some or all of the acid groups in the structural unit (a1) are neutralized with ammonia,
A pigment dispersion for inkjet, wherein the binder (B) contains a crosslinked acrylic resin (B1).
(2) The ink-jet pigment dispersion of (1), wherein the dispersant (A) has a glass transition temperature of 50 to 120° C. and an acid value of 100 to 300 mgKOH/g.
(3) The crosslinked acrylic resin (B1) is an acrylic emulsion having a volume average particle diameter of 20 to 100 nm, a glass transition temperature of 0 to 70° C., and an acid value of 5 to 80 mgKOH/g. The inkjet pigment dispersion of (1) or (2).
(4) The inkjet pigment dispersion according to any one of (1) to (3), further comprising an amine compound (E) having a boiling point of 100° C. or higher.
(5) The inkjet pigment dispersion according to any one of (1) to (4), which is for printing on plastic substrates.
(6) An inkjet ink using the inkjet pigment dispersion according to any one of (1) to (5).
(7) A printed matter printed with the inkjet ink of (6).

According to the present invention, it is possible to obtain a water-based inkjet ink for printing on plastic substrates, which is excellent in adhesiveness to plastic substrates, anti-blocking properties, and ink ejection properties during inkjet printing.

[Inkjet pigment dispersion]
The "inkjet pigment dispersion" (hereinafter sometimes simply referred to as "pigment dispersion" or "dispersion") of the present invention comprises a dispersant (A), a binder resin (B), a pigment (C), and It contains water (D) and is used for the preparation of inkjet inks. Hereinafter, "dispersant (A)" may be referred to as "component (A)", and other components may be referred to in the same way.
The pigment dispersions of the invention are produced as intermediate products for inkjet inks and, after dilution, are used in inkjet printing as aqueous inkjet inks.

<Dispersant (A)>
The dispersant (A) contains a resin (A1), and the resin (A1) has at least a structural unit (a1) derived from an acid group-containing monomer. Further, in the dispersant (A), some or all of the acid groups in the structural unit (a1) in the structural unit (a1) are neutralized with ammonia.

(Resin (A1))
The resin (A1) has a structural unit (a1) derived from an acid group-containing monomer and a structural unit (a2) other than (a1), and comprises an acid group-containing monomer and a monomer other than that. It can be obtained by polymerizing using a known method such as radical polymerization. By having an acid group in the resin (A1), hydrophilicity is imparted to the resin (A1), making it possible to stably disperse the pigment in water.

The acid group in the acid group-containing monomer from which the structural unit (a1) is derived includes a carboxyl group, a sulfonic acid group, a phosphoric acid group, a thiocarboxyl group, and the like, and an ethylenically unsaturated monomer having these groups is used as a structural unit. It can be used as a raw material monomer of (a1).
Examples of ethylenically unsaturated monomers containing a carboxyl group include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and 4-vinylbenzoic acid; vinyl succinate; , polybasic unsaturated esters such as allyl maleate, vinyl terephthalate, and allyl trimetitrate.
Examples of ethylenically unsaturated monomers containing a sulfonic acid group include unsaturated carboxylic acid sulfo-substituted alkyl or aryl esters such as 2-sulfoethyl acrylate and 4-sulfophenyl methacrylate; Unsaturated sulfocarboxylic acid esters; sulfostyrenes such as styrene-4-sulfonic acid can be mentioned.
Among them, as the monomer from which the structural unit (a1) is derived, a monomer having a carboxyl group as an acid group is preferable, and an unsaturated carboxylic acid is more preferable, considering the availability and price of the raw material monomer. Acid or methacrylic acid are preferred.
Hereinafter, the term "(meth)acrylic acid" may include both acrylic acid and methacrylic acid, and the term "(meth)acrylic acid ester" may include both acrylic acid ester and methacrylic acid ester. There is The same is true for similar acrylic compounds.

Examples of the structural unit (a2) other than the structural unit (a1) include ethylenically unsaturated monomers copolymerizable with (a1), such as methyl (meth)acrylate, ethyl (meth)acrylate, (Meth)acrylic acid esters such as methylpropyl (meth)acrylate; unsaturated fatty acids such as dimethyl maleate, dimethyl fumarate, 2-hydroxyethyl (meth)acrylate, 2-aminoethyl (meth)acrylate, etc. Esters; Unsaturated fatty acid amides such as (meth)acrylamide and N-methyl(meth)acrylamide; Unsaturated nitriles such as (meth)acrylonitrile; Unsaturated ethers such as vinyl acetate and vinyl propionate; -Styrenes such as methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 4-methoxystyrene, 4-chlorostyrene; ethylene, propylene, 1-butene, 1-octene , vinylcyclohexane, 4-vinylcyclohexene, and other unsaturated hydrocarbons; vinyl chloride, vinylidene chloride, tetrafluoroethylene, 3-chloropropylene, and other unsaturated halogenated hydrocarbons; 4-vinylpyridine, N-vinyl vinyl-substituted heterocyclic compounds such as carbazole, N-vinylpyrrolidone; monomers containing substituents having active hydrogen such as carboxyl group, hydroxyl group, amino group, etc. in the above-exemplified monomers, ethylene oxide, propylene oxide, Reaction products with epoxides such as cyclohexene oxide; acetic acid, propionic acid, butanoic acid, hexanoic acid, decanoic acid, dodecane, and monomers containing substituents having hydroxyl groups, amino groups, etc. in the above-exemplified monomers Examples thereof include reaction products with carboxylic acids such as acids.
Among them, styrenes are preferable, and styrene or α-methylstyrene is preferable as the monomer from which the structural unit (a2) is derived, since the effect of increasing the adsorptive power of the resin (A1) to the pigment can be obtained.

As the structural unit (a2), it is preferable to further contain methoxypolyethylene glycol monomethacrylate as a monomer since it has an excellent effect of improving ejection properties.

The resin (A1) may or may not have a crosslinked portion, for example. The resin having a crosslinked portion is obtained by copolymerizing the monomers described above with a glycidyl group-containing ethylenically unsaturated monomer such as 2,3-epoxypropyl (meth)acrylate in combination. After forming a crosslinkable resin, it can be obtained by cross-linking in combination with a curing accelerator as necessary in any step of producing an aqueous pigment dispersion.

The mass-average molecular weight of the resin (A1) is 2 in that the pigment dispersion has an appropriate viscosity, good dispersion stability, and long-term stable printing when used as an inkjet ink. ,000 to 100,000, particularly preferably 5,000 to 50,000.

The acid value of the resin (A1) is preferably 80-350 mgKOH/g, more preferably 100-300 mgKOH/g, particularly preferably 180-300.
The glass transition point of the resin (A1) is preferably 30 to 130°C, more preferably 50 to 120°C, particularly preferably 80 to 110°C.
Within the above range, the hydrophilicity and pigment adsorptivity of the dispersant are well balanced, and the dispersion stability of the pigment dispersion is improved. In addition, the coating film strength of the printed matter is increased, and the abrasion resistance is improved.

In the dispersant (A), part or all of the acid groups in the structural unit (a1) in the structural unit (a1) are neutralized with ammonia.
Although the method of neutralization with ammonia is not particularly limited, for example, aqueous ammonia and, if necessary, water are added to the resin (A1) in the organic solvent obtained by synthesizing the monomers. can be neutralized by
In the neutralization, only part of the acid groups may be neutralized, or all of the acid groups may be neutralized. Specifically, assuming that the neutralization rate is 100% when the acid groups of the dispersing agent (A) are neutralized in a theoretically equivalent amount, the neutralization rate is preferably 30 to 300%, particularly set in the range of 60 to 200%. preferably.
An inkjet ink using a dispersant (A) neutralized with ammonia becomes insoluble in water due to volatilization of ammonia in a drying process after printing. In addition, when the ammonia volatilizes, the acid groups in the dispersant (A) move to a non-dissociated equilibrium state, so that the hygroscopicity of the dispersant (A) decreases and the ink dries quickly. As a result, the adhesiveness to the substrate and the abrasion resistance are improved.

The dispersant (A) may consist of the resin (A1) only, or may contain other components in addition to the resin (A1).

In the pigment dispersion of the present invention, the dispersant (A) is preferably contained in an amount of 5 to 100% by mass, more preferably 10 to 60% by mass, in terms of nonvolatile matter. Within these ranges, deterioration in dispersion stability of the pigment dispersion due to excess or deficiency of the dispersant can be suppressed, and a stable state can be maintained even during long-term storage.

<Binder resin (B)>
In the present invention, the binder (B) contains a crosslinked acrylic resin (B1). The binder (B) is added for the purpose of enhancing the adhesion of the ink to the substrate and the abrasion resistance. If the binder (B) has a pigment dispersing ability, the binder (B) may detach the dispersant (A) from the pigment and reduce the dispersion stability of the pigment dispersion. preferably does not have pigment dispersibility.

(Crosslinked acrylic resin (B1))
As the crosslinked acrylic resin (B1) used as the binder resin, a crosslinked aqueous acrylic resin emulsion is preferred.
Examples of acrylic emulsions include acrylic emulsions, styrene-acrylic emulsions, acrylic-maleic acid emulsions, and styrene-acrylic-maleic acid emulsions, with acrylic emulsions and styrene-acrylic emulsions being preferred. The emulsion may be core-shell type or non-core-shell type.
Examples of the structural unit in the emulsion resin include those described above for the structural unit (a1) and the structural unit (a2), and those copolymerizable therewith.

In the present invention, the acrylic resin (B1) is crosslinked.
As a result of repeated studies by the present inventors, the higher the Tg of the acrylic resin (B1), the better the dry scratch resistance. It has been found that the scratch resistance is reduced.
However, although the mechanism of action is unknown, it was found that cross-linking the acrylic resin (B1) improves the dry scratch resistance even at a low Tg. Moreover, good results were obtained by cross-linking regardless of whether the Tg was high or low with respect to the wet rubbing resistance.
Therefore, by using the crosslinked acrylic resin (B1), even when the low Tg acrylic resin (B1) is used, a pigment dispersion having good scratch resistance in both dry and wet processes can be obtained.

Examples of the method for cross-linking the acrylic resin (B1) include a method using a cross-linking agent that reacts with the functional groups contained in the acrylic resin (B1). A cross-linking agent is a compound having two or more reactive functional groups in the molecule, and specific examples of the cross-linking agent include epoxy compounds, hydrazide compounds, and carbodiimide compounds.

The acid value of the acrylic resin (B1) is preferably 5-100 mgKOH/g, more preferably 5-80 mgKOH/g, still more preferably 20-50 mgKOH/g. If the acid value is less than 5 mgKOH/g, the dispersion stability of the acrylic resin (B1) may deteriorate. On the other hand, when the acid value exceeds 100 mgKOH/g, the hygroscopicity of the printed coating film increases, and the wet rubbing property of the rubbing resistance may be impaired.

The glass transition point of the acrylic resin (B1) is preferably 0 to 100°C, more preferably 0 to 80°C, even more preferably 0 to 70°C, and particularly preferably 10 to 40°C.
By setting it within the above range, the drying time after printing can be shortened, which is preferable from the viewpoint of improving the printing speed and saving energy.

The volume average particle size of the acrylic resin (B1) is preferably 20 to 100 nm, more preferably 20 to 80 nm. The volume average particle diameter can be measured, for example, by filling a cell with a resin diluted with ion-exchanged water and using UPA-EX150 under the following conditions.
・Loading index: 5±1
・Measurement time: 180 seconds ・Number of measurements: 5 ・Transmittance: transmission ・Particle refractive index: 1.80
・Shape: true sphere ・Density: 1.00
・ Solvent refractive index: 1.333
・Viscosity at high temperature: 30°C, 0.797
・Viscosity at low temperature: 20°C, 1.002
・Filter: Stand: Norm
・Sensitivity: Standard
・UPA compatible mode

Moreover, as resin (B1), it is of course possible to use a commercially available product. As a commercially available product, ME-2039 (manufactured by Seiko PMC Co., Ltd., crosslinked acrylic emulsion) and the like can be used.

In the pigment dispersion of the present invention, the binder resin (B) is preferably contained in an amount of 10 to 200% by mass, more preferably 30 to 150% by mass in terms of non-volatile content. These ranges are preferable because the adhesiveness of the inkjet ink to the substrate, the abrasion resistance, and the blocking resistance are compatible even after dilution.

<Pigment (C)>
The pigment (C) is not particularly limited as long as it can be dispersed well in the pigment dispersion, but it is preferable to use one that can be dispersed with an average particle size of 50 to 400 nm (details will be described later). . For example, organic pigments, inorganic pigments, and dyes used in general inks, paints, and recording agents can be used.

Examples of organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethineazo, ditopyrrolopyrrole, and isoindoline pigments. pigments. Copper phthalocyanine is preferably used for the indigo ink from the viewpoint of cost and light resistance.

Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, and mica (mica). A bright pigment (Metashine; Nippon Sheet Glass Co., Ltd.) obtained by coating glass flakes or massive flakes as a base material with a metal or a metal oxide can also be used. From the viewpoint of cost and coloring power, it is preferable to use titanium oxide for white ink, carbon black for black ink, aluminum for gold and silver inks, and mica for pearl ink.

As described above, in the pigment dispersion, the pigment is preferably dispersed with a volume average particle diameter of 50 to 400 nm. The average particle size of the pigment can be measured by a known method such as a dynamic light scattering method after preparing a pigment dispersion and then uniformly dispersing the pigment in the dispersion. Among them, the volume average particle diameter of the pigment in the dispersion is preferably 50 to 300 nm, more preferably 50 to 200 nm, even more preferably 50 to 150 nm, and particularly preferably 50 nm or more and less than 100 nm. When the volume average particle diameter is 50 nm or more, aggregation of the pigment during storage of the pigment dispersion can be suppressed. Further, when the volume average particle diameter is 400 nm or less (particularly preferably 100 nm or less), the ink jettability is improved.

Although the content of the pigment in the aqueous pigment dispersion is not particularly limited, it is preferably 10 to 30% by mass based on the total weight of the pigment dispersion. If it is less than 10% by mass, there is a risk that sufficient ink coloring power cannot be obtained in an inkjet ink prepared by diluting the pigment dispersion. If the amount is more than 30% by mass, the pigment may aggregate during transportation or storage of the dispersion, depending on the type of pigment. In addition, depending on the degree of dilution, there is a concern that the ink jettability may deteriorate.

In the pigment dispersion of the present invention, the pigment concentration is preferably 10 to 30 mass %, more preferably 10 to 25 mass % when the pigment is an organic pigment or carbon black. Within these ranges, when an inkjet ink is prepared by dilution adjustment, it is possible to favorably achieve both ink coloring power and ink jettability.
Also, when the pigment is an inorganic pigment, it is preferably 25 to 60% by mass, more preferably 30 to 50% by mass.

<Other optional ingredients>
The pigment dispersion of the present invention may contain other optional components in addition to the above components (A) to (C) and water (D) within a range that does not impair the effects of the present invention. good.
Other components include, for example, an amine compound (E) having a boiling point of 100° C. or higher, other resins other than the above components, solvents other than water, surfactants, waxes, low surface tension organic solvents, wetting agents, penetrants, and other than the above. dispersants, antifoaming agents, preservatives, viscosity modifiers, pH modifiers, chelating agents, plasticizers, antioxidants, ultraviolet absorbers and the like.

(Amine compound (E) having a boiling point of 100°C or higher)
The pigment dispersion of the invention preferably contains an amine compound (E) having a boiling point of 100° C. or higher.
In the pigment dispersion of the present invention, the dispersant (A) is neutralized with ammonia to improve adhesion to the substrate and abrasion resistance. Excessive progress may cause nozzle clogging. The amine compound (E) has the effect of moderately neutralizing the insolubilized acid groups in the ink and re-dissolving them in water. Moreover, the amine compound (E) having a boiling point of 100° C. or higher is also effective as a wetting agent.
Therefore, by adding the amine compound (E), excessive drying of the ink is suppressed and the ink does not clog the nozzles. be able to.

Amine compounds (E) include polyalkyleneimines, polyallylamines, (poly)ethylenepolyamines, alkanolamines and alkylamines.
Among these, alkanolamine is preferable from the viewpoint of pigment dispersibility.

(polyalkyleneimine)
The polyalkyleneimine is preferably a polyalkyleneimine having an alkylene group having 2 or more and 5 or less carbon atoms.
The polyalkyleneimine is preferably a polyalkyleneimine in which the alkylene group has 2 or more and 4 or less carbon atoms, more preferably polyethyleneimine or polypropyleneimine, and still more preferably polyethyleneimine. These may be used alone or in combination of two or more.

The number average molecular weight of the polyalkyleneimine is preferably 150 or more, more preferably 500 or more, still more preferably 800 or more, still more preferably 1,000 or more, and preferably 10,000 or less, more preferably 5,000 or more. 000 or less, more preferably 4,000 or less.
The molecular weight value is determined by the method described in Examples.

(Polyallylamine)
Examples of polyallylamine include polymers having amino groups in side chains, such as homopolymers or copolymers of allyl compounds such as allylamine and dimethylallylamine.
The weight average molecular weight of polyallylamine is preferably 800 or more, more preferably 1,000 or more, still more preferably 1,500 or more, and preferably 10,000 or less, more preferably 5,000 or less, and still more preferably is 4,000 or less.

(polyethylene polyamine)
(Poly)ethylenepolyamines include, for example, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and the like. Among these, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine are preferred.

(Alkanolamine)
The alkanolamine is preferably an alkanolamine having 2 to 9 carbon atoms. Examples of alkanolamines include primary alkanolamines such as monoethanolamine, monopropanolamine and monobutanolamine; monoalkanol secondary amines such as N-methylethanolamine and N-methylpropanolamine; diethanolamine and diisopropanolamine; Secondary alkanolamines such as dialkanol secondary amines of; - tertiary alkanolamines such as dialkanol tertiary amines such as ethyldiethanolamine, and trialkanol tertiary amines such as triethanolamine and triisopropanolamine. Among these, tertiary alkanolamines having 2 to 9 carbon atoms are preferred, and triisopropanolamine is particularly preferred.

(alkylamine)
The alkylamine is preferably an alkylamine having 1 to 6 carbon atoms. Examples of alkylamines include primary amines such as propylamine, butylamine and hexylamine; secondary amines such as diethylamine and dipropylamine.

In the pigment dispersion of the present invention, the amine compound (E) preferably has a neutralization rate of 30 to 500%, particularly preferably in the range of 50 to 400%, with respect to the acid groups of the dispersant (A). . Within these ranges, the ink does not cause nozzle clogging and is excellent in adhesion and abrasion resistance.

(Components other than (E) component)
Other resins may be aqueous resins suitable for preparing pigment dispersions, and preferred examples include acrylic resins such as polyvinyl alcohols, polyvinylpyrrolidones, acrylic acid-acrylic acid ester copolymers, and 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- Styrene-acrylic resin such as acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, and salts of the above water-based resins Those that do not fall under

Examples of solvents other than water include alcohol solvents such as methanol, ethanol, n-propanol and isopropanol; ketone solvents such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol and propylene glycol; ethers; lactam solvents such as N-methyl-2-pyrrolidone;

Surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. Among these, anionic surfactants or nonionic surfactants is preferred.

Examples of anionic surfactants include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfuric acid ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, and higher alcohol ethers. Sulfuric acid ester salts and sulfonates, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. Specific examples thereof include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, and dibutylphenylphenoldisulfonate.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, and glycerin fatty acid esters. , polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkylalkanolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, alkylphenol ethoxylates, etc., among which polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ether , polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, and alkylphenol ethoxylates are preferred.

Other surfactants include silicon-based surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers. spiculisporic acid, rhamnolipids, biosurfactants such as lysolecithin, and the like can also be used.

These surfactants can be used alone or in combination of two or more. Further, considering the dissolution stability and the like of the surfactant, the HLB is preferably in the range of 7-20.

Commercially available fluorosurfactants include Novec FC-4430, FC-4432 (manufactured by Sumitomo 3M), Zonyl FSO-100, FSN-100, FS-300, FSO (manufactured by DuPont), Ftop EF- 122A, EF-351, 352801, 802 (manufactured by Jemco), Megafac F-470, F-1405, F474, F-444 (manufactured by DIC), Surflon S-111, S-112, S-113, S121, S131 , S132, S-141, S-145 (manufactured by Asahi Glass), Ftergent series (manufactured by Neos), Fluorad FC series (manufactured by Minnesota Mining and Manufacturing Company), Monflor (Imperial ・chemical industry), Licowet VPF series (manufactured by Farbewerke Hoechst).

Examples of silicone surfactants include KF-351A, KF-642, Olfine PD-501, Olfine PD-502, Olfine PD-570 (manufactured by Shin-Etsu Chemical Co., Ltd.), BYK347, BYK348 (manufactured by BYK-Chemie Japan) and the like.

As polyoxyethylene alkyl ether-based surfactants, BT series (Nikko Chemicals), Nonipor series (Sanyo Kasei), D-, P-series (Takemoto Yushi), Emalex DAPE series (Nippon Emulsion), Pegnol series ( Toho Chemical Industry). Pegnol (Toho Kagaku Kogyo Co., Ltd.) is exemplified as a polyethylene glycol alkyl ester type.

Examples of acetylene glycol-based surfactants include OLFINE E1010, STG, Y (manufactured by Nisshin Chemical Co., Ltd.), Surfynol 104, 82, 420, 440, 465, 485, and TG (manufactured by Air Products and Chemicals Inc.). mentioned.

Waxes include, for example, plant and animal waxes such as carnauba wax, candy wax, beeswax, rice wax and lanolin; mineral waxes such as montan wax and ozokerite; paraffin waxes are so-called petroleum waxes; carbon waxes and Hoechst waxes. , synthetic waxes such as polyolefin wax, silicone wax and stearic acid amide; These waxes have the effect of imparting slip properties to the surface of the formed recorded matter and improving the abrasion resistance. These waxes can be used singly or in combination. Among these, silicone wax, polyolefin wax, paraffin wax and the like are preferably used.

Commercially available silicone waxes include, for example, SM8706EX, SM7036EX, SM7060EX, SM7025EX, SM490EX, SM8701EX, SM8709SR, SM8716SR, IE-7045, IE-7046T, SH7024, BY22-744EX, BY8FZ-X5, FZ-X5, FZ-8Z44E 4634EX, FZ-4602 (trade names, manufactured by Dow Corning Toray Co., Ltd.), POLON-MF-14, POLON-MF-14EC, POLON-MF-23 POLON-MF-63, POLON-MF-18T, POLON-MF -56, POLON-MF-49, POLON-MF-33A, POLON-MF-55T, POLON-MF-28T, POLONMF-50, POLON-MK-206, POLON-SR-CONC, KM-9771, KM-9774 , KM-2002-T, KM-2002-L-1, KM-9772, KS-7002, KS-701, X-51-1264 (trade names, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

Examples of polyolefin waxes include waxes produced from olefins such as ethylene, propylene and butylene, or derivatives thereof, and copolymers thereof, specifically polyethylene waxes, polypropylene waxes, polybutylene waxes, and the like. Polyolefin waxes can be used singly or in combination of two or more. Among these, polyethylene-based waxes are preferable from the viewpoint of being less likely to react with the crosslinkable groups of the urethane resin particles having the above-mentioned crosslinkable groups and having excellent ejection stability.

Commercially available polyolefin waxes include, for example, AQUACER 513 (polyethylene wax, average particle size 100 nm or more and 200 nm or less, melting point 130°C, solid content 30%), AQUACER 507, AQUACER 515, AQUACER 840, AQUACER 1547 (all trade names, BYK-Chemie Japan Co., Ltd. company's AQUACER series, Hitec E-7025P, Hitec E-2213, Hitec E-6500, Hitec E-6314, Hitec E-9460, Hitec E-9015, Hitec E-4A, Hitec E-5403P, Hitec Hightech series such as E-8237 (product name, manufactured by Toho Chemical Co., Ltd., polyethylene wax), Nopcoat PEM-17 (product name, manufactured by San Nopco, polyethylene emulsion, average particle size 40 nm), ULTRALUBE E-843N (product manufactured by Keim Additec Surface GmbH, polyethylene wax).

Paraffin wax is a so-called petroleum wax. Here, paraffin means an alkane having 20 or more carbon atoms, and paraffin wax is mainly composed of linear paraffinic hydrocarbons having 20 or more and 30 or less carbon atoms, and a small amount of isoparaffin. A mixture of hydrocarbons with a molecular weight of about 300 to 500, including By containing the paraffin wax in the ink, the recorded matter is imparted with slipperiness and water repellency, thereby improving scratch resistance.

Commercially available products of paraffin wax include, for example, AQUACER537 and AQUACER539 (both trade names, manufactured by BYK-Chemie Japan).

The wax is preferably contained in the pigment dispersion in the form of fine particles, that is, in the form of emulsion or suspension. This makes it easier to adjust the viscosity of the ink so that it falls within an appropriate range for ejection using an inkjet head, and to ensure ejection stability and intermittent ejection characteristics during recording.

Examples of low surface tension organic solvents such as glycol ether compounds include diethylene glycol mono(alkyl having 1 to 8 carbon atoms) ether, triethylene glycol mono(alkyl having 1 to 8 carbon atoms) ether, propylene glycol mono(1 to 8 carbon atoms) C-6 alkyl) ethers, dipropylene glycol mono(C 1-6 alkyl) ethers can be mentioned, and these can be used singly or as a mixture of two or more.

Specifically, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl. Ether, diethylene glycol mono-iso-propyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monoheptyl ether, diethylene glycol monooctyl ether, triethylene glycol monomethyl ether, triethylene Glycol Monoethyl Ether, Triethylene Glycol Monopropyl Ether, Triethylene Glycol Monobutyl Ether, Triethylene Glycol Monopentyl Ether, Triethylene Glycol Monohexyl Ether, Triethylene Glycol Monoheptyl Ether, Triethylene Glycol Monooctyl Ether, Propylene Glycol Monomethyl Ether Ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol mono-iso-propyl ether, propylene glycol monobutyl ether, propylene glycol mono-t-butyl ether, propylene glycol monopentyl ether, propylene glycol monohexyl ether, dipropylene Glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol mono-iso-propyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether, dipropylene glycol monohexyl ether and the like. be able to.

Glycol ethers, surfactants, and the like can be used to adjust the surface tension of the ink. Specifically, it can be added appropriately so that the surface tension of the ink is 15 mN/m to 30 mN/m or less, and the amount of the surfactant added is in the range of about 0.1 to 10% by mass with respect to the aqueous pigment dispersion. It is preferably 0.3 to 2% by mass, more preferably 0.3 to 2% by mass. More preferably, the surface tension is in the range of 16-28, most preferably in the range of 18-25.

Although the wetting agent is not particularly limited, it is preferable to use a wetting agent that is miscible with water and that can prevent clogging of the ink jet printer head. For example, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a molecular weight of 2000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,2-butane Diol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methylpentane-2,4-diol, 1, Diol compounds such as 2-heptanediol, 1,2-nonanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-nonanediol and 1,2-octanediol , 1,4-butanediol, 1,3-butanediol, mesoerythritol, pentaerythritol, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone , ε-caprolactam and other nitrogen-containing heterocyclic compounds. Among them, the inclusion of propylene glycol and 1,3-butyl glycol is safe and has excellent effects on ink drying property and ejection performance.
The content of the humectant in the ink is preferably 3 to 50% by mass.

Penetrants include lower alcohols such as ethanol and isopropyl alcohol, ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether, and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. The content of the penetrant in the pigment dispersion is preferably 0.01 to 10 mass %.

<Method for producing pigment dispersion>
The method for producing the pigment dispersion in the present invention is not limited at all.
Components (A) to (D) and optional components such as component (E) added as necessary may be dispersed to form a pigment dispersion. ), a part of components (C) and (D), a medium, etc., to prepare a pigment-dispersed millbase liquid with a high pigment concentration, add component (B) and optional components as appropriate, and use an aqueous medium such as component (D) It may be diluted into a pigment dispersion for the preparation of aqueous inkjet inks. An aqueous pigment dispersion in which a pigment is dispersed with a desired volume average particle size can be easily obtained by preparing a pigment dispersion millbase liquid in advance by dispersing the pigment using a stirring/dispersing device and then preparing the pigment dispersion. be able to.
The latter method of preparing a pigment-dispersed millbase liquid and then converting it into a pigment dispersion will be described below.

Examples of the method for producing the pigment-dispersed millbase liquid include the following methods.
(1) A method of adding a pigment to an aqueous medium containing a pigment dispersant as necessary, and then dispersing the pigment in the aqueous medium using a stirring/dispersing device to prepare a pigment-dispersed millbase liquid.
(2) A pigment and, if necessary, a pigment dispersant are kneaded using a kneader such as a two-roll kneader or a mixer, the resulting kneaded product is added to an aqueous medium, and the pigment is dispersed using a stirring/dispersing device. A method for preparing a dispersed millbase liquor.
(3) After adding a pigment to a solution obtained by dissolving a pigment dispersant in an organic solvent compatible with water such as methyl ethyl ketone and tetrahydrofuran, the pigment is dispersed in the organic solution using a stirring/dispersing device. followed by phase inversion emulsification using an aqueous medium, followed by distilling off the organic solvent to prepare a pigment dispersion millbase liquid.

Examples of the stirring/dispersing device include an ultrasonic homogenizer, a high pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a dyno mill, a dispermat, an SC mill, a nanomizer, and the like. may be used alone, or two or more types of devices may be used in combination.

<Inkjet ink>
The pigment dispersion of the present invention is used and diluted with an aqueous medium so that the pigment content is 1 to 30% by mass to prepare an aqueous inkjet ink. This aqueous medium may be water, similar to component (D), a mixture of water and an organic solvent, or an organic solvent alone. The organic solvent is not particularly limited as long as it is miscible with water, and examples thereof include those mentioned above as optional components as the "solvent other than water".

<Printed Matter>
Since the inkjet ink of the present invention has excellent adhesion to various substrates, it is possible to suitably produce a printed material having a plastic substrate and an inkjet ink-printed layer.

Examples of plastic substrates include polyamide resins such as Ny6, nylon 66, and nylon 46; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; Polyhydroxycarboxylic acids such as polylactic acid, biodegradable resins typified by aliphatic polyester resins such as poly (ethylene succinate) and poly (butylene succinate), polyolefin resins such as polypropylene and polyethylene, polyimide resins, poly Examples include plastic substrates made of thermoplastic resins such as arylate resins or mixtures thereof, and laminates thereof. Among them, substrates made of polyester, polyamide, polyethylene, and polypropylene can be preferably used.

Also, the plastic substrate may be a plastic film. The plastic film may be either an unstretched film or a stretched film, and its production method is not limited. Also, the thickness of the film is not particularly limited, but it is usually in the range of 1 to 500 μm.
Moreover, it is preferable that the printing surface of the film is subjected to a corona discharge treatment. In addition, silica, alumina, or the like may be vapor-deposited on the printed surface.

INDUSTRIAL APPLICABILITY The printed matter of the present invention has good adhesion to plastic substrates and can be produced by inkjet printing, so that it can be suitably used as a packaging material. Since it is particularly excellent in designability and on-demand printability, it can be used particularly preferably for food packaging. Further, since the inkjet ink of the present invention is excellent in abrasion resistance, the printed material of the present invention can be a surface printed material in which the surface to be the front side is subjected to inkjet printing.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. Hereinafter, "part" means "mass part" and "%" means "mass%" unless otherwise specified.

[Synthesis Example of Dispersion]
(Synthesis Example 1: Synthesis Example of Styrene Acrylic Resin 1)
In a reaction vessel of an automatic polymerization reactor (polymerization tester DSL-2A S type, manufactured by Todoroki Sangyo Co., Ltd.) having a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device at the top 600 parts of methyl ethyl ketone was charged, and the inside of the reaction vessel was replaced with nitrogen while stirring. After raising the temperature to 80 ° C. while maintaining the inside of the reaction vessel in a nitrogen atmosphere, 160 parts of styrene, 80 parts of α-methylstyrene, 124 parts of acrylic acid, and 36 parts of Blenmer PME-100 (manufactured by NOF Corporation) from a dropping device. , and 44 parts of "PERBUTYL O" (active ingredient: t-butyl peroxy 2-ethylhexanoate, manufactured by NOF Corporation) was added dropwise over 4 hours. After completion of dropping, the reaction was continued at the same temperature for 15 hours to obtain a methyl ethyl ketone solution of styrene-acrylic resin.
To the methyl ethyl ketone solution of the styrene acrylic resin obtained above, 83 parts of 28% aqueous ammonia and 550 parts of deionized water are gradually added as neutralizing agents to neutralize the carboxyl groups in the styrene acrylic resin, and then methyl ethyl ketone is added. By distilling off under reduced pressure, a styrene-acrylic resin 1 having a non-volatile content of 40% by mass was obtained. The styrene acrylic resin 1 had an acid value of 240 mgKOH/g and a glass transition temperature of 91°C.

(Synthesis Examples 2 to 5: Synthesis examples of styrene acrylic resins 2 to 5)
Styrene acrylic resins 2 to 5 were obtained in the same manner as described above except that the monomer composition and neutralizing agent of Synthesis Example 1 were changed according to Table 1.
In the table below, BLEMMER PME-100 is methoxypolyethylene glycol monomethacrylate (manufactured by NOF Corporation).

[Synthesis example of binder resin]
(Synthesis Example 6: Synthesis Example of Aqueous Polyurethane 1)
964 parts by mass of 1,6-hexanediol-based polycarbonate diol (weight average molecular weight: 2,000) and 43 parts by mass of dimethylolpropionic acid were placed in a nitrogen-purged vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer. and 558 parts by mass of methyl ethyl ketone were added and mixed uniformly. Next, after adding 295 parts by mass of dicyclohexylmethane diisocyanate, 0.05 part by mass of tin dioctate was added and reacted at 70°C for about 4 hours to obtain a methyl ethyl ketone solution of urethane prepolymer 1 having an isocyanate group at the molecular end. Obtained.
33 parts by mass of triethylamine was added to the methyl ethyl ketone solution of the urethane prepolymer 1 obtained above to neutralize the carboxyl groups in the urethane prepolymer 1, and then 2,516 parts by mass of ion-exchanged water was gradually added. Then, 11.0 parts by mass of 80% hydrazine aqueous solution was added and reacted. After completion of the reaction, methyl ethyl ketone was distilled off under reduced pressure to obtain aqueous polyurethane 1 having a non-volatile content of 40% by mass. This aqueous polyurethane 1 had a volume average particle diameter of 98 nm, an acid value of 10 mgKOH/g, and a glass transition temperature of -29°C.

[Production Example of Mill Dispersion 1]
In a mixing tank, 250 parts of styrene acrylic resin 1 as a dispersion resin, 55 parts of isopropyl alcohol, 710 parts of ion-exchanged water, and 500 parts of FASTOGEN BLUE SBG-SD (Pigment Blue 15:3, manufactured by DIC Corporation) were charged and dispersed. (TK Homo Disper Model 20, manufactured by Tokushu Kika Kogyo Co., Ltd.). The obtained mixed solution is circulated and dispersed in a dispersing device (Pikomill model: PCM-LR, manufactured by Asada Iron Works Co., Ltd.) filled with zirconia beads with a diameter of 0.3 mm (a method of returning the dispersion liquid discharged from the dispersing device to the mixing tank )did. During the dispersing step, cold water was passed through the cooling jacket to control the temperature of the dispersion liquid to be kept at 30° C. or less, and dispersion was performed for 2 hours with the rotor peripheral speed of the dispersing apparatus fixed at 12 m/sec. After completion of the dispersion, the undiluted dispersion liquid extracted from the mixing tank was distilled under reduced pressure to remove part of the isopropyl alcohol and water, thereby obtaining a mill dispersion 1 (pigment concentration: 33%).

[Production Examples of Mill Dispersions 2 to 5]
Mill Dispersions 2 to 5 were obtained in the same manner as described above, except that the dispersion resin of Mill Dispersion 1 was changed to styrene acrylic resins 2 to 5, respectively.

[Example 1 Production Example of Pigment Dispersion 1]
45 parts of mill dispersion 1, ME-2039 (manufactured by Seiko PMC Co., Ltd., crosslinked acrylic emulsion, volume average particle diameter 63 nm, acid value 42 mg KOH / g, glass transition temperature 8 ° C., nonvolatile content 49%) as a binder. 24.5 parts, 3.9 parts of ULTRALUBE E-843N (polyethylene wax manufactured by Keim Additec Surface GmbH) as a wax, Proxel GXL (S) as a preservative (manufactured by Lonza Japan Co., Ltd.) 0.2 parts, ion 26.4 parts of exchanged water was charged and stirred for 30 minutes with a paint shaker (Toyo Seiki Seisakusho Co., Ltd., amplitude 750/min) to obtain Pigment Dispersion 1 having a pigment content of 15% in terms of mass.

[Examples 2 to 4, Comparative Examples 1 to 7: Production Examples of Pigment Dispersions]
Pigment Dispersions 2 to 4 (Examples 2 to 4) and Comparative Dispersions 1 to 7 (Comparative Examples 1 to 7) were obtained in the same manner as described above except that the formulation of Example 1 was changed according to Tables 2 to 3. .

The component names used in the above table represent the following.
M-141: Seiko PMC Co., Ltd., non-crosslinked acrylic emulsion, volume average particle size 71 nm, acid value 19 KOH mg / g, glass transition temperature 15 ° C., nonvolatile content 40%
QE-1042: Seiko PMC Co., Ltd., non-crosslinked acrylic emulsion, volume average particle size 31 nm, acid value 33 KOH mg / g, glass transition temperature 53 ° C., non-volatile content 40%

[Examples 5 to 8, Comparative Examples 8 to 14: Production Examples of Ink Compositions]
Using Pigment Dispersions 1 to 4 and Comparative Dispersions 1 to 7 obtained above, respectively, formulations as shown in Tables 4 to 5 below were performed, and the ink compositions 1 to 1 were prepared by stirring with a paint shaker for 30 minutes. 4 (Examples 5-8) and Comparative Ink Compositions 1-7 (Comparative Examples 8-14) were prepared.
Using the obtained ink composition of each example, a printed matter for evaluation was produced, and the blocking resistance, substrate adhesion, scratch resistance and nozzle clogging were evaluated. The evaluation results are also shown in Tables 4 and 5. The details of the method for producing the evaluation printed matter and the evaluation method will be described later.

<Preparation of printed matter for evaluation>
The ink composition is filled into an ink cartridge of an inkjet printer (manufactured by Seiko Epson Corporation, MJ-510C) and applied to a corona-treated polyethylene terephthalate (PET) film (Ester E5100, thickness 12 μm, manufactured by Toyobo Co., Ltd.) or a corona After printing a solid pattern on a treated polypropylene (OPP) biaxially stretched film (Pylen P2161, thickness 20 μm, manufactured by Toyobo Co., Ltd.), the pattern was dried with a dryer, and then placed in an oven at 90° C. for 10 minutes to obtain a printed matter. .

<Blocking resistance>
Cut the film into 4 cm x 4 cm size so that the printed surface and the non-printed surface of the printed PET film are in contact, stack them together, apply a load of 5 kgf/cm2, and leave the film at 50°C for 24 hours. The state of ink transfer (set-off) to the non-printed surface when the was peeled off was visually judged based on the area ratio (%) of the set-off portion.
⊚: No transfer to the non-printing surface is observed.
◯: Transfer due to set-off is observed, though slightly less than 5%.
Δ: 5% or more to less than 20% of transfer due to set-off is observed.
x: Transfer due to set-off of 20% or more is observed.

<Scratch resistance>
In accordance with JIS K5701-1:2000, the abrasion resistance of the printed OPP film was evaluated using a Gakushin-type rubbing fastness tester (manufactured by Tester Sangyo Co., Ltd., AB-301). The printed matter was set in the tester, and the dry friction test was performed using PPC paper as the friction paper, a load of 200 g, and 100 reciprocations. The test was conducted under the conditions of After the test, the degree of ink peeling on the printed matter was visually evaluated according to the following evaluation criteria.
A: Peeling did not occur at all.
O: Less than 1% of peeling occurred.
Δ: There was peeling of 1% or more and less than 5%.
x: There was peeling of 5% or more and less than 10%.

<Substrate adhesion>
After leaving the printed material for a day, stick cellophane tape (12mm width manufactured by Nichiban) on the printed surface, and quickly peel off one end of the cellophane tape in a direction perpendicular to the printed surface. The appearance was judged visually based on the standard.
A: The printed film is not peeled off at all.
○: 80% or more to less than 90% of the printed film remained on the film.
Δ: 50% or more to less than 80% of the printed film remained on the film.
x: Less than 50% of the printed film remained on the film.

<Evaluation of Ink Dischargeability>
After printing equivalent to 10 A4 solid sheets by the above-described inkjet printing procedure, a check pattern was printed, and non-ejection nozzles were evaluated according to the following criteria. A grade of C or higher is regarded as a pass.
A: Less than 1% of non-ejection nozzles B: 1% to less than 3% to less than 5% of non-ejection nozzles C: 3% to less than 5% of non-ejection nozzles D: 5% or more of non-ejection nozzles

As is clear from the above results, the inkjet inks of Examples 5 to 8 using the pigment dispersions of Examples 1 to 4 according to the present invention have excellent adhesion to plastic substrates, anti-blocking properties, ink jetting properties and resistance to ink jetting. It was confirmed that it was excellent in all aspects of scratch resistance.
On the other hand, the inkjet inks of Comparative Examples 8 to 14 using the comparative dispersions of Comparative Examples 1 to 7 were inferior in any of the above properties.
Therefore, it was confirmed that the inkjet pigment dispersion and the inkjet ink of the present invention can be suitably used for inkjet printing. In addition, the pigment dispersion and ink of the present invention are suitable for printing on packaging plastic films because of their high substrate adhesion to plastic substrates, and their high abrasion resistance makes them suitable for printing on plastic substrates. It was confirmed that the method can also be applied to printing.

Claims (7)

Dispersant (A), binder resin (B), pigment (C), and water (D),
The dispersant (A) contains at least a resin (A1) having a structural unit (a1) derived from an acid group-containing monomer,
In the resin (A1), some or all of the acid groups in the structural unit (a1) are neutralized with ammonia,
A pigment dispersion for inkjet, wherein the binder (B) contains a crosslinked acrylic resin (B1). 2. The inkjet pigment dispersion according to claim 1, wherein the dispersant (A) has a glass transition temperature of 50 to 120° C. and an acid value of 100 to 300 mgKOH/g. Claim 1, wherein the crosslinked acrylic resin (B1) is an acrylic emulsion having a volume average particle diameter of 20 to 100 nm, a glass transition temperature of 0 to 70°C, and an acid value of 5 to 80 mgKOH/g. 3. The inkjet pigment dispersion according to 2 above. 4. The inkjet pigment dispersion according to any one of claims 1 to 3, further comprising an amine compound (E) having a boiling point of 100°C or higher. 5. The inkjet pigment dispersion according to any one of claims 1 to 4, which is used for printing on plastic substrates. An inkjet ink using the inkjet pigment dispersion according to any one of claims 1 to 5. A printed matter printed with the inkjet ink according to claim 6 .