Pigment dispersion for inkjet ink, inkjet ink and printed matter

Abstract

To provide an inkjet ink that is excellent in scratch resistance and alcoholic resistance when printed on various substrates such as plastic substrate or the like, and generates no odor during production.SOLUTION: The present invention contains a dispersant (A), a pigment (B), a binder (C) and water (D), the dispersant (A) contains at least a non-crosslinked resin (A1) having a constituent unit (a1) derived from an acid-group-containing monomer, in the resin (A1), with a neutralization rate when the acid group in the constituent unit (a1) is neutralized with a theoretical equivalent 100%, at the neutralization rate of 80% or more and 200% or less, alkanolamine is used to neutralize, the alkanolamine has one to three hydroxy groups in a structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pigment dispersion used in aqueous inkjet inks, an aqueous inkjet ink prepared using the pigment dispersion, and a printed matter inkjet printed using the inkjet ink. [Background technology]

[0002] In addition to the need for sustainability against the backdrop of worsening air pollution caused by VOCs and the global expansion of global warming, there is a movement to move away from petroleum resources due to concerns about occupational safety and health and flammability, and regulations on the use of organic solvents are becoming increasingly strict. As a result, the printing ink industry is developing water-based inks that replace the organic solvents in solvent-based printing inks with water, and there is also a demand for the development and improvement of water-based inks in inkjet inks.

[0003] On the other hand, due to population growth, rising income levels, and changes in logistics systems, the consumption of plastic film packaging is on the rise worldwide, and as a result, the production of packaging ink is increasing year by year. Traditionally, solvent-based flexographic inks and solvent-based gravure inks have been the mainstream for printing on film substrates. However, these printing methods require plate-making, which increases costs and requires time before printing. For this reason, there is a growing demand for inkjet printing, which does not require plate-making and allows on-demand printing, even in film package printing. There is also a growing demand for on-demand printing on film substrates other than packaging applications, such as film printing for sign displays used indoors and outdoors.

[0004] However, aqueous inkjet inks have the problem of still being insufficient in abrasion resistance compared to solvent-based inkjet inks. While reverse printing, in which printing is performed on the reverse side of the film substrate, is the mainstream method for printing on a film substrate, surface printing, in which printing is performed on the front side of the film substrate, is faster in terms of printing and processing speed, and is therefore more advantageous when productivity and cost are important. However, in surface printing, the printed surface comes into contact with the external environment without the substrate, so high abrasion resistance is required for the printed surface and the ink itself. An inkjet ink with excellent abrasion resistance would be desirable because an inkjet ink with excellent abrasion resistance could be used not only for reverse printing but also for front printing on a film, thereby increasing versatility.

[0005] On the other hand, attempts have been made to improve the abrasion resistance of aqueous inkjet inks, but as a result, there are concerns that the resulting formation of aggregates will reduce filterability and ink ejection performance. Ink ejection reliability, a unique issue in inkjet printing, occurs when ink dries in the inkjet head ejection area during the open time (when ink is not being ejected) during inkjet printing, resulting in nozzle clogging. Inkjet inks are desired to have excellent ink resolubility, which can reduce the occurrence of nozzle clogging.

[0006] In addition, alcohol-based disinfectants are now being used to prevent contact infection of bacteria and viruses through hands and objects. Since it is anticipated that consumers may touch packages with their hands that have alcohol-based disinfectant on them, or that consumers may disinfect the surface of the package itself with alcohol-based disinfectant, inkjet inks used for printing on the surface of packages must also have high alcohol resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-196423 A Summary of the Invention [Problem to be solved by the invention]

[0008] Patent Document 1 discloses an inkjet ink that has excellent water resistance and alcohol resistance and is capable of film printing. The ink is characterized by the acid value of the dispersant being neutralized with ammonia and the resin emulsion having a specific Tg and acid value. In Patent Document 1, solvent resistance is evaluated by rubbing with a cotton swab moistened with a solvent, and it is clear that a certain degree of abrasion resistance can be achieved with the configuration of Patent Document 1. However, Patent Document 1 does not evaluate abrasion resistance in the dry state, which is where further improvement in abrasion resistance is desired. In addition, the invention described in Patent Document 1 uses ammonia for neutralization, which causes problems with odors generated during production and odors remaining in the composition itself. Furthermore, because ammonia is highly volatile, there is also the problem that nozzle clogging may occur when the ammonia used for neutralization evaporates. Furthermore, further improvement in alcohol resistance is desired.

[0009] The problem to be solved by the present invention is to provide an inkjet ink that has good abrasion resistance and alcohol resistance when printed on various substrates such as plastic substrates and that does not emit an odor during production, etc., as well as an inkjet pigment dispersion that can be used in the inkjet ink, and a printed item that has been inkjet printed with the inkjet ink. [Means for solving the problem]

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the problems can be solved by a pigment dispersion in which some or all of the acid groups in a dispersant resin are neutralized with an alkanolamine and further a non-crosslinked resin is used as a dispersant, thereby completing the present invention.

[0011] That is, the present invention relates to the following inventions. (1) A composition comprising a dispersant (A), a pigment (B), a binder (C), and water (D), The dispersant (A) contains at least a non-crosslinked resin (A1) having a structural unit (a1) derived from an acid group-containing monomer, In the resin (A1), the acid groups in the structural unit (a1) are neutralized with an alkanolamine at a neutralization rate of 80% or more and 200% or less, with the neutralization rate being 100% when the acid groups are neutralized in a theoretical equivalent amount; The pigment dispersion for inkjet recording is characterized in that the alkanolamine has 1 to 3 hydroxyl groups in the structure. (2) The pigment dispersion for inkjet according to (1), wherein the acid value of the resin (A1) is 80 to 225 mgKOH / g. (3) The pigment dispersion for inkjet according to (1) or (2), wherein the binder (C) is an acrylic binder or a polyester binder. (4) A pigment dispersion for inkjet printing according to any one of (1) to (3), which is for printing on a plastic substrate. (5) An inkjet ink using the inkjet pigment dispersion according to any one of (1) to (4). (6) Printed matter printed with the inkjet ink in (5). [Effects of the Invention]

[0012] According to the present invention, it is possible to obtain an aqueous inkjet ink that has good abrasion resistance and alcohol resistance even when used on a plastic substrate, and that does not emit an odor during production, etc. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Inkjet pigment dispersions] The "pigment dispersion for inkjet printing" (hereinafter sometimes simply referred to as "pigment dispersion" or "dispersion") of the present invention contains a dispersant (A), a pigment (B), a binder (C), and water (D), and is used for preparing inkjet inks. Hereinafter, "dispersant (A)" will sometimes be referred to as "component (A)," and the same will be used for other components. The pigment dispersion of the present invention is produced as an intermediate product for inkjet inks, and is used in inkjet printing as an aqueous inkjet ink after dilution.

[0014] <Dispersant (A)> The dispersant (A) contains a non-crosslinked resin (A1), which has at least a structural unit (a1) derived from an acid group-containing monomer, and the acid group in the structural unit (a1) in the dispersant (A) is neutralized with a tertiary alkanolamine.

[0015] (Resin (A1)) Resin (A1) is a non-crosslinked resin having a structural unit (a1) derived from an acid group-containing monomer and a structural unit (a2) other than (a1), and is obtained by polymerizing the acid group-containing monomer and the other monomer in the presence of any polymerization initiator using a known method such as radical polymerization. The presence of acid groups in resin (A1) imparts hydrophilicity to resin (A1), enabling stable dispersion of pigments in water.

[0016] In the acid group-containing monomer from which the structural unit (a1) is derived, examples of the acid group include a carboxyl group, a sulfonic acid group, a phosphoric acid group, and a thiocarboxyl group, and ethylenically unsaturated monomers having these groups can be used as raw material monomers for the structural unit (a1). Examples of the ethylenically unsaturated monomer 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; and unsaturated polybasic esters such as vinyl succinate, allyl maleate, vinyl terephthalate, and allyl trimetrite. 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 such as vinyl sulfosuccinate; and sulfostyrenes such as styrene-4-sulfonic acid. Among these, as the monomer from which the structural unit (a1) is derived, taking into consideration the availability and cost of the raw material monomers, a monomer having a carboxyl group as the acid group is preferred, unsaturated carboxylic acids are more preferred, and acrylic acid or methacrylic acid is more preferred. Hereinafter, the term "(meth)acrylic acid" may be used to encompass both acrylic acid and methacrylic acid, and the term "(meth)acrylic acid ester" may be used to encompass both acrylic acid esters and methacrylic acid esters. The same applies to similar acrylic acid compounds.

[0017] Examples of the structural unit (a2) other than the structural unit (a1) include ethylenically unsaturated monomers copolymerizable with (a1), such as (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, methylpropyl (meth)acrylate, and butyl (meth)acrylate; unsaturated fatty acid esters such as dimethyl maleate, dimethyl fumarate, 2-hydroxyethyl (meth)acrylate, and 2-aminoethyl (meth)acrylate; 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; styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 4-methoxystyrene, 4- Examples of the monomer include styrenes such as chlorostyrene; unsaturated hydrocarbons such as ethylene, propylene, 1-butene, 1-octene, vinylcyclohexane, and 4-vinylcyclohexene; unsaturated halogenated hydrocarbons such as vinyl chloride, vinylidene chloride, tetrafluoroethylene, and 3-chloropropylene; vinyl-substituted heterocyclic compounds such as 4-vinylpyridine, N-vinylcarbazole, and N-vinylpyrrolidone; reaction products of a monomer containing a substituent having an active hydrogen, such as a carboxyl group, a hydroxyl group, or an amino group, among the above-exemplified monomers, with an epoxide such as ethylene oxide, propylene oxide, or cyclohexene oxide; and reaction products of a monomer containing a substituent having a hydroxyl group, an amino group, or the like, among the above-exemplified monomers, with a carboxylic acid such as acetic acid, propionic acid, butanoic acid, hexanoic acid, decanoic acid, or dodecanoic acid. Among these, as the monomer from which the structural unit (a2) is derived, (meth)acrylic acid esters and styrenes are preferred, and butyl (meth)acrylate, styrene, or α-methylstyrene is preferred, as these have the effect of increasing the adsorptivity of the resin (A1) to the pigment.

[0018] The structural unit (a2) also preferably contains methoxypolyethylene glycol monomethacrylate as a monomer, as this has the excellent effect of improving ejection properties.

[0019] Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of organic peroxides include di-t-butyl peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, cumene hydroperoxide, isobutyl peroxide, lauryl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxypivalate, benzoyl peroxide, and methyl ethyl ketone peroxide. Examples of azo compounds include 2,2'-azobisisobutyronitrile (AIBN), 1,1'-azobis(cyclohexanecarbonitrile) (ABCN), 2,2'-azobis-2-methylbutyronitrile (AMBN), 2,2'-azobis-2,4-dimethylvaleronitrile (ADVN), and 4,4'-azobis-4-cyanovaleric acid (ACVA). The polymerization initiators may be used alone or in combination of two or more.

[0020] Resin (A1) is a non-crosslinked resin. In the present invention, "non-crosslinked resin (A1)" means that resin (A1) is synthesized and produced without intentionally using a compound generally considered to be a crosslinking agent, or that resin (A1) is synthesized and produced without undergoing a commonly used crosslinking step. The crosslinking rate of resin (A1) produced without adding a crosslinking agent or undergoing an intentional crosslinking step is 5% or less, preferably 3% or less, and most preferably 0%. Non-crosslinked resin (A1) is essentially a linear resin. The above crosslinking rate is a theoretical value, and is 100% when the amount of crosslinking agent is 1 molar equivalent, and 50% when the amount is 0.5 molar equivalent. In the present invention, since the abrasion resistance is improved by the alkanolamine described below, it is not necessary to ensure abrasion resistance by crosslinking the resin (A1). Furthermore, since the resin (A1) is non-crosslinked, the resolubility of the dispersion and ink is improved, and excellent ink ejection properties are obtained, thereby suppressing problems such as nozzle clogging. Furthermore, since the crosslinking step is not required during the production of the resin (A1), it is expected that the production process will be shortened and energy consumption will be reduced.

[0021] The mass average molecular weight of the resin (A1) is preferably in the range of 2,000 to 100,000, and particularly preferably in the range of 5,000 to 50,000, from the viewpoints of providing the pigment dispersion with an appropriate viscosity, improving dispersion stability, and easily ensuring stable printing over a long period of time when used in an inkjet ink.

[0022] The acid value of the resin (A1) is generally 80 to 350 mgKOH / g, preferably 80 to 225 mgKOH / g, more preferably 80 to 220 mgKOH / g, particularly preferably 100 mgKOH / g or more and less than 200 mgKOH / g, and also preferably less than 170 mgKOH / g. By adjusting the content within the above range, the hydrophilicity of the dispersant and the pigment adsorption property are well balanced, and the dispersion stability of the pigment dispersion is improved. In the present invention, by making the resin (A1) non-crosslinked, good resolubility can be obtained even when the acid value of the resin (A1) is relatively low (for example, less than 200 mgKOH / g, etc.).

[0023] The glass transition point of the resin (A1) is preferably from 30 to 130°C, more preferably from 50 to 120°C, and particularly preferably from 80 to 110°C.

[0024] In the dispersant (A), some or all of the acid groups in the structural unit (a1) are neutralized with an alkanolamine having 1 to 3 hydroxyl groups in its structure (hereinafter sometimes simply referred to as "alkanolamine"). The alkanolamine is preferably a compound in which one or two of the three hydrogen atoms of ammonia (NH3) are substituted with an "organic group having a hydroxyl group" and the remaining one or two are substituted with an organic group, or a compound in which all three hydrogen atoms are substituted with an "organic group having a hydroxyl group". The organic group substituting the hydrogen atom is preferably an alkyl group having 1 to 3 carbon atoms, and the "organic group having a hydroxyl group" substituting the hydrogen atom is preferably a group in which a hydroxyl group is bonded to an alkyl group having 1 to 3 carbon atoms. The alkanolamine is preferably a compound represented by the following formula (I):

[0025] [ka] (In formula (I), R 1 ~R 3 are each independently an organic group which may have a hydroxyl group, and R 1 ~R 3 At least one of the groups is an organic group having a hydroxyl group.)

[0026] The organic group is preferably a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms. The number of hydroxyl groups substituting the alkyl group is preferably two or more, more preferably one to three, and most preferably one. The boiling point of the alkanolamine is preferably from 100 to 330°C, more preferably from 110 to 330°C, more preferably from 120 to 320°C, and even more preferably from 130 to 310°C. By using an alkanolamine with a boiling point of 330°C or less for neutralization, the alkanolamine volatilizes well when the printed material dries, without generating an odor like ammonia.Also, alkanolamines with a boiling point of 100°C or more are less likely to volatilize in inkjet nozzles, making them less likely to clog nozzles or reduce ejection performance.

[0027] Examples of the alkanolamines mentioned above include monoalkanol tertiary amines such as dimethylethanolamine; dialkanol tertiary amines such as N-methyldiethanolamine, N-ethyldiethanolamine, and N-(3-aminopropyl)diethanolamine; and trialkanol tertiary amines such as triisopropanolamine. Among these, tertiary alkanolamines having 2 to 9 carbon atoms are preferred, and methyldiethanolamine or triisopropanolamine is particularly preferred.

[0028] The method of neutralization with an alkanolamine is not particularly limited, but for example, the resin (A1) obtained by synthesis of the monomer in an organic solvent can be neutralized by adding an alkanolamine and, if necessary, water.

[0029] Neutralization may be carried out using the alkanolamine alone or in combination with other neutralizing agents, such as metal salts. Examples of metal salts include metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; metal chlorides such as sodium chloride and potassium chloride; and metal sulfides such as copper sulfate. When an alkanolamine and a metal salt are used in combination, the ratio of alkanolamine to metal salt is preferably 60 to 120%:30 to 90%, for a total neutralization rate of 150%, if the neutralization rate described below is 150%. If the neutralization rate is not 150%, it is preferable to use the alkanolamine and metal salt in the same ratio. By using a metal salt in combination, it is possible to achieve a balance between abrasion resistance and solubility. However, the use of a metal salt can also cause problems, such as it being unsuitable for printing on food packaging, so it is preferable to consider the use of a metal salt in combination with other salts, taking into account the intended application.

[0030] The neutralization may be such that only a portion of the acid groups are neutralized, or such that all of the acid groups are neutralized, but it is preferable that all of the acid groups are neutralized. Specifically, the neutralization rate when the acid groups of the resin (A1) are neutralized in a theoretical equivalent amount is taken as 100%, and the neutralization rate is 80% or more and 200% or less, preferably 100 to 200%. By achieving such a neutralization rate, the solubility and filterability of the resin (A1) are improved.

[0031] The dispersant (A) may consist of only the resin (A1), or may contain other components in addition to the resin (A1).

[0032] In the pigment dispersion of the present invention, the dispersant (A) is preferably contained in an amount of 5 to 100 mass % relative to the pigment in terms of nonvolatile content, and more preferably 10 to 80 mass %. Within these ranges, a decrease in the dispersion stability of the pigment dispersion due to an excess or deficiency of the dispersant is suppressed, and the pigment dispersion can be maintained in a stable state even during long-term storage.

[0033] <Pigment (B)> The pigment (B) is not particularly limited as long as it can be well dispersed in the dispersion, but it is preferable to use one that can be dispersed with an average particle diameter of 10 to 400 nm (details will be described later). For example, organic pigments, inorganic pigments, and dyes that are commonly used in inks, paints, and recording agents can be used.

[0034] Examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, azomethine azo pigments, dicetyrrolopyrrole pigments, isoindoline pigments, etc. For indigo inks, copper phthalocyanine pigments are preferably used from the standpoints of cost and light resistance.

[0035] 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. Also usable are glittering pigments (Metashine; Nippon Sheet Glass Co., Ltd.) made of glass flakes or aggregate flakes as a base material coated with a metal or metal oxide. From the standpoints 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 ink, and mica for pearl ink.

[0036] As described above, the pigment in the dispersion is preferably dispersed with a volume average particle diameter of 10 to 400 nm. The volume average particle diameter of the pigment can be measured by preparing the dispersion and then uniformly dispersing the pigment in the dispersion using a known method such as dynamic light scattering. The volume average particle diameter of the dispersion is preferably 10 to 300 nm, more preferably 50 to 200 nm, even more preferably 50 to 150 nm, and particularly preferably 50 nm or more but less than 100 nm. A volume average particle diameter of 50 nm or more can suppress aggregation of the pigment during storage of the pigment dispersion. Furthermore, a volume average particle diameter of 400 nm or less (particularly preferably 100 nm or less) can improve ink ejection properties.

[0037] The pigment content in the dispersion is not particularly limited, but is preferably 10 to 30% by mass of the total amount of the dispersion. If it is less than 10% by mass, sufficient ink coloring power may not be obtained in the inkjet ink prepared by diluting the dispersion. If it is more than 30% by mass, depending on the pigment type, the pigment may aggregate during transportation or storage of the dispersion, in which case dispersibility at an average particle diameter of 50 to 400 nm may not be ensured. Furthermore, depending on the degree of dilution, there is a concern that ink ejection performance may deteriorate.

[0038] In the dispersion of the present invention, when the pigment is an organic pigment or carbon black, the pigment concentration is preferably 10 to 30% by mass, more preferably 10 to 25% by mass. Within these ranges, when diluted to prepare an inkjet ink, both ink coloring power and ink ejection properties can be favorably achieved. When the pigment is an inorganic pigment, the content is preferably 25 to 60 mass %, more preferably 30 to 50 mass %.

[0039] <Binder (C)> The use of a binder (C) in the dispersion of the present invention can further improve the substrate adhesion and abrasion resistance of the ink. On the other hand, if the binder (C) has pigment dispersibility, the binder (C) may cause the dispersant (A) to be released from the pigment, which may reduce the dispersion stability of the pigment dispersion. Therefore, it is preferable that the binder (C) does not have pigment dispersibility. Preferred binders include acrylic binders (C1) and polyester binders (C2).

[0040] (Acrylic binder (C1)) The acrylic binder (C1) is not particularly limited as long as it contains an acrylic resin, and may be an acrylic resin or an acrylic emulsion obtained by dispersing an acrylic resin in a solvent. Among these, a water-based acrylic emulsion is preferred because of its excellent dispersibility in the pigment dispersion. The use of the acrylic binder (C1) can improve the adhesion of the inkjet ink using the dispersion of the present invention to an olefin-based substrate such as (biaxially) oriented polypropylene (OPP). 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 emulsions may be of a core-shell type or may be of a type other than the core-shell type. Examples of structural units in the emulsion resin include those described above as the structural unit (a1) and the structural unit (a2), as well as units copolymerizable therewith.

[0041] The present inventors have found through past studies that the higher the Tg of the acrylic binder (C1), the better the dry abrasion resistance obtained, while the lower the Tg of the acrylic binder (C1) the lower the dry abrasion resistance may be.

[0042] The acid value of the acrylic binder (C1) is preferably 5 to 100 mgKOH / g, more preferably 5 to 80 mgKOH / g, and even more preferably 20 to 50 mgKOH / g. If the acid value is less than 5 mgKOH / g, the dispersion stability of the acrylic binder (C1) may decrease. On the other hand, if the acid value exceeds 100 mgKOH / g, the moisture absorption of the printed coating film may increase, and the wet friction resistance, which is one of the abrasion resistance properties, may be impaired.

[0043] The glass transition point of the acrylic binder (C1) is preferably from 0 to 100°C, more preferably from 0 to 80°C, even more preferably from 0 to 70°C, and particularly preferably from 10 to 40°C. By setting the amount within the above range, the drying time after printing can be shortened, which is preferable from the viewpoint of improving printing speed and saving energy.

[0044] The volume average particle size of the acrylic binder (C1) is preferably 20 to 100 nm, more preferably 20 to 80 nm. The volume average particle size 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 Measurement count: 5 times ·Transparency: Transparent Particle refractive index: 1.80 ·Shape: true sphere ·Density: 1.00 Solvent refractive index: 1.333 ·Viscosity at high temperature: 30℃, 0.797 ·Viscosity at low temperature: 20℃, 1.002 Filter:Stand:Norm Sensitivity: Standard UPA compatibility mode

[0045] Of course, commercially available acrylic binders (C1) can also be used, such as "ME-2039," "XJE-509," "XJE-518," "XJE-520," "XJE-556," and "XJE-600" (acrylic emulsions manufactured by Seiko PMC Corporation); "Joncryl 631" and "Joncryl 731" (manufactured by BASF).

[0046] (Polyester binder (C2)) The polyester-based binder (C2) may be a general polyester resin obtained by dehydration condensation of a polyol with a polycarboxylic acid, a polycarboxylic acid anhydride, or a polycarboxylic acid ester. The use of a polyester-based binder can improve the adhesion of an ink-jet ink using the dispersion of the present invention to a substrate having a polar group, such as polyethylene terephthalate (PET). Examples of polyols used in producing polyester resins include alkylene glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,6-hexanediol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol; and cyclic diols such as 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, and bisphenol S, as well as alkylene oxide adducts thereof. The polycarboxylic acid used in the production of the polyester resin is preferably a dicarboxylic acid, and specific examples thereof include succinic acid, apidic acid, sebacic acid, dodecenylsuccinic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, phthalic acid, isophthalic acid, terephthalic acid, or derivatives thereof, and naphthalenedicarboxylic acid. A polyester resin can be obtained by using one or more of the above polyols and one or more of the polycarboxylic acids.

[0047] The number average molecular weight of the polyester resin is preferably 1,000 to 50,000, and more preferably 3,000 to 20,000.

[0048] As the polyester resin, commercially available products may be used. Examples of commercially available products include "ELITEL KA-5034" (number average molecular weight: 8500), "ELITEL KA-5071S" (number average molecular weight: 8500), "ELITEL KA-1449" (number average molecular weight: 7000), "ELITEL KA-0134" (number average molecular weight: 8500), "ELITEL KA-3556 (number average molecular weight: 8000), "ELITEL KA-6137" (number average molecular weight: 5000), and "ELITEL KZA-6034" (number average molecular weight: 8500). Examples of such copolymers include "ELITEL KT-8803" (number average molecular weight: 15,000), "ELITEL KT-8701" (number average molecular weight: 13,000), "ELITEL KT-9204" (number average molecular weight: 17,000), "ELITEL KT-8904" (number average molecular weight: 17,000), "ELITEL KT-0507" (number average molecular weight: 17,000), and "ELITEL KT-9511" (number average molecular weight: 17,000) (all manufactured by Unitika Ltd.). These may be used alone or in combination of two or more.

[0049] The binder (C) can contain other components instead of or in addition to the above-mentioned components (C1) and (C2). As the other components, polyurethane resins are preferred. Among them, polyether polyol polyurethane resins are preferred because they are less prone to hydrolysis than polyester polyol polyurethanes and provide particularly excellent abrasion resistance to colored images. Examples of polyether polyol polyurethane resins include polyurethane resins obtained by reacting polytetramethylene ether glycol (PTMG) with diisocyanate.

[0050] In the dispersion of the present invention, the binder (C) is preferably contained in an amount of 10 to 200 mass % in terms of nonvolatile content, more preferably 30 to 150 mass %, because this range allows the inkjet ink to have good adhesion to a substrate, abrasion resistance, and blocking resistance even after dilution. The content of the binder (C) in 100% by mass of the aqueous inkjet ink of the present invention is preferably 0.1 to 5.0% by mass, and more preferably 0.3 to 3.0% by mass.

[0051] <Other optional ingredients> The pigment dispersion of the present invention may contain other optional components in addition to the above-described components (A), (B), (C), and water (D), as long as the effects of the present invention are not impaired. Examples of other components include 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, penetrating agents, dispersants other than the above, antifoaming agents, preservatives, viscosity adjusters, pH adjusters, chelating agents, plasticizers, antioxidants, and ultraviolet absorbers.

[0052] (Amine compound (E) with a boiling point of 100°C or higher) The pigment dispersion of the present invention preferably contains an amine compound (E) having a boiling point of 100° C. or higher. By adding the amine compound (E), excessive drying of the ink is further suppressed, and the ink does not clog the nozzles, resulting in good jetting properties, making it possible to achieve both jetting properties and abrasion resistance.

[0053] Examples of the amine compound (E) include polyalkyleneimines, polyallylamine, (poly)ethylenepolyamines, alkanolamines, and alkylamines. Among these, alkanolamines are preferred from the viewpoints of pigment dispersibility, odor and resolubility.

[0054] (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 having an alkylene group with 2 to 4 carbon atoms, more preferably polyethyleneimine or polypropyleneimine, and even more preferably polyethyleneimine. These may be used alone or in combination of two or more.

[0055] The number average molecular weight of the polyalkyleneimine is preferably 150 or more, more preferably 500 or more, even more preferably 800 or more, even more preferably 1,000 or more, and preferably 10,000 or less, more preferably 5,000 or less, even more preferably 4,000 or less. The molecular weight value can be determined by the method described in the Examples.

[0056] (Polyallylamine) Examples of polyallylamine include polymers having amino groups on the side chains, such as homopolymers or copolymers of allyl compounds such as allylamine and dimethylallylamine. The weight average molecular weight of the polyallylamine is preferably 800 or more, more preferably 1,000 or more, even more preferably 1,500 or more, and preferably 10,000 or less, more preferably 5,000 or less, even more preferably 4,000 or less.

[0057] (Polyethylene polyamine) Examples of (poly)ethylenepolyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc. Among these, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine are preferred.

[0058] (alkanolamines) The alkanolamine is preferably an alkanolamine having 2 to 9 carbon atoms. Examples of alkanolamines include primary alkanolamines such as monoethanolamine, monopropanolamine, and monobutanolamine; secondary alkanolamines such as monoalkanol secondary amines such as N-methylethanolamine and N-methylpropanolamine; and secondary alkanolamines such as dialkanol secondary amines such as diethanolamine and diisopropanolamine; and tertiary alkanolamines such as monoalkanol tertiary amines such as N,N-dimethylethanolamine, N,N-dimethylpropanolamine, and N,N-diethylethanolamine; dialkanol tertiary amines such as N-methyldiethanolamine and N-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.

[0059] (Alkylamine) The alkylamine is preferably an alkylamine having a carbon number of 1 to 6. Examples of the alkylamine include primary amines such as propylamine, butylamine, and hexylamine; and secondary amines such as diethylamine and dipropylamine.

[0060] In the pigment dispersion of the present invention, the neutralization rate of the amine compound (E) relative to the acid groups of the dispersant (A) is preferably set in the range of 30 to 500%, and particularly preferably in the range of 50 to 400%. Within these ranges, the ink will not clog nozzles and will have excellent adhesion and abrasion resistance.

[0061] (Components other than components (A) to (E)) As the other resin, a water-based resin suitable for preparing a pigment dispersion is preferable, and examples thereof include a styrene-maleic acid copolymer, a styrene-maleic anhydride copolymer, and the like.

[0062] 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; alkyl ethers of polyalkylene glycols; and lactam solvents such as N-methyl-2-pyrrolidone.

[0063] Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, and among these, anionic surfactants and nonionic surfactants are preferred.

[0064] Examples of anionic surfactants include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfate ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate ester salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates. Specific examples of these include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, and dibutylphenylphenol disulfonate.

[0065] 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, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylolamides, alkylalkanolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, and alkylphenol ethoxylates. Of these, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ethers, 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.

[0066] Other surfactants that can be used include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin.

[0067] These surfactants can be used alone or in combination of two or more. In consideration of the dissolution stability of the surfactant, the HLB value is preferably in the range of 7 to 20.

[0068] Commercially available fluorine-based surfactants include Novec FC-4430 and FC-4432 (manufactured by Sumitomo 3M), Zonyl FSO-100, FSN-100, FS-300, and FSO (manufactured by DuPont), Ftop EF-122A, EF-351, 352, 801, and 802 (manufactured by Gemco), Megafac F-470, F-1405, F474, and F-444 (manufactured by DIC), and Surflon S-111, S-112, S-113, and S Examples include 121, S131, S132, S-141, and S-145 (manufactured by Asahi Glass), the Ftergent series (manufactured by Neos), the Fluorad FC series (manufactured by Minnesota Mining and Manufacturing Company), Monflor (manufactured by Imperial Chemical Industries), and the Licowet VPF series (manufactured by Farbewerke-Hoechst).

[0069] 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, and BYK348 (manufactured by BYK Japan).

[0070] Examples of polyoxyethylene alkyl ether surfactants include the BT series (Nikko Chemicals), the Nonipol series (Sanyo Chemical Industry Co., Ltd.), the D- and P-series (Takemoto Oil & Fat Co., Ltd.), the EMALEX DAPE series (Nippon Emulsion Co., Ltd.), and the Pegnol series (Toho Chemical Industry Co., Ltd.). Examples of polyethylene glycol alkyl ester surfactants include Pegnol (Toho Chemical Industry Co., Ltd.).

[0071] Examples of acetylene glycol surfactants include Olfine E1010, STG, and Y (all manufactured by Nissin Chemical Co., Ltd.), and Surfynol 104, 82, 420, 440, 465, 485, and TG (manufactured by Air Products and Chemicals Inc.).

[0072] Examples of waxes include plant- and animal-based waxes such as carnauba wax, candelilla wax, beeswax, rice wax, and lanolin; mineral waxes such as montan wax and ozokerite; petroleum-based waxes such as paraffin wax; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, silicone wax, and stearic acid amide; and natural and synthetic wax emulsions and blended waxes such as α-olefin-maleic anhydride copolymers. These waxes impart slip properties to the surface of the printed matter and improve abrasion resistance. These waxes can be used alone or in combination. Among these, silicone wax, polyolefin wax, and paraffin wax are preferred.

[0073] Commercially available silicone waxes include, for example, SM8706EX, SM7036EX, SM7060EX, SM7025EX, SM490EX, SM8701EX, SM8709SR, SM8716SR, IE-7045, IE-7046T, SH7024, BY22-744EX, BY22-818EX, FZ-4658, FZ-4634EX, and FZ-4602 (all trade names, manufactured by Dow Corning Toray Co., Ltd.), POLON-MF-14, POLON-MF-14EC, and POLON-MF-2 3 Examples of such polyolefin copolymers include 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, and X-51-1264 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0074] 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, and polybutylene waxes. Polyolefin waxes can be used singly or in combination of two or more. Among these, polyethylene waxes are preferred because they are less likely to react with the crosslinkable groups of the urethane resin particles having the crosslinkable groups, and therefore have excellent ejection stability.

[0075] Commercially available polyolefin waxes include, for example, the AQUACER series, such as AQUACER 531 (polyethylene wax, average particle size 100 nm to 200 nm, melting point 130°C, solid content 30%), AQUACER 507, AQUACER 515, AQUACER 840, and AQUACER 1547 (all trade names, manufactured by BYK Japan); the Hitec series, such as Hitec E-7025P, Hitec E-2213, Hitec E-6500, Hitec E-6314, Hitec E-9460, Hitec E-9015, Hitec E-4A, Hitec E-5403P, and Hitec E-8237 (all trade names, manufactured by Toho Chemical Industry Co., Ltd., polyethylene wax); Nopcoat PEM-17 (trade name, manufactured by San Nopco, polyethylene emulsion, average particle size 40 nm); and ULTRALUBE E-843N (trade name, polyethylene wax, manufactured by Keim Additec Surface GmbH) and the like.

[0076] Paraffin wax is a petroleum-based wax. Here, paraffin refers to an alkane with 20 or more carbon atoms, and paraffin wax refers to a mixture of hydrocarbons with a molecular weight of approximately 300 to 500, primarily consisting of linear paraffin hydrocarbons with 20 to 30 carbon atoms and containing a small amount of isoparaffin. Inclusion of paraffin wax in ink gives printed materials slip properties and water repellency, thereby improving abrasion resistance.

[0077] Commercially available paraffin wax products include, for example, AQUACER 537 and AQUACER 539 (trade names, manufactured by BYK Japan).

[0078] The wax is preferably contained in the pigment dispersion in the form of fine particles, i.e., in the form of an emulsion or suspension, which makes it easier to adjust the viscosity of the ink to an appropriate range for ejection using an inkjet head and also makes it easier to ensure ejection stability and intermittent ejection characteristics during recording.

[0079] Examples of low surface tension organic solvents include glycol ether compounds such as 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(alkyl having 1 to 6 carbon atoms) ether, and dipropylene glycol mono(alkyl having 1 to 6 carbon atoms) ether, and these can be used alone or as a mixture of two or more.

[0080] Specifically, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-isopropyl 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-isopropyl 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 monobutyl ether, Examples of the propylene glycol monopentyl ether include triethylene glycol monohexyl ether, triethylene glycol monoheptyl ether, triethylene glycol monooctyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol mono-isopropyl 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-isopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether, and dipropylene glycol monohexyl ether.

[0081] Glycol ethers, surfactants, and the like can be used as surface tension adjusters to adjust the surface tension of the ink. Specifically, they can be added appropriately so that the surface tension of the ink is 15 mN / m to 30 mN / m. The amount of surfactant added is preferably in the range of about 0.1 to 10 mass% of the aqueous pigment dispersion, and more preferably 0.3 to 2 mass%. The surface tension is more preferably in the range of 16 to 28 mN / m, and most preferably in the range of 18 to 25 mN / m.

[0082] The wetting agent is not particularly limited, but is preferably one that is miscible with water and has the effect of preventing clogging of the inkjet printer head. Examples include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycols with a molecular weight of 2000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,2-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methylpentane-2,4-diol, and the like. Examples of suitable inks include diol compounds such as 1,2-heptanediol, 1,2-nonanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-nonanediol, and 1,2-octanediol, and nitrogen-containing heterocyclic compounds such as 1,4-butanediol, 1,3-butanediol, mesoerythritol, pentaerythritol, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, and ε-caprolactam. Among these, inks containing propylene glycol and 1,3-butyl glycol are safe and exhibit excellent effects in terms of ink drying properties and ejection performance. The content of the wetting agent in the ink is preferably 3 to 50% by mass.

[0083] Examples of the penetrating agent 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 penetrating agent in the pigment dispersion is preferably 0.01 to 10% by mass.

[0084] <Method for producing pigment dispersion> The method for producing the pigment dispersion of the present invention is not limited in any way. The pigment dispersion may be prepared by dispersing components (A) to (D) and optional components such as component (E) that are added as needed, or the pigment dispersion for preparing an aqueous inkjet ink may be prepared by first preparing a pigment dispersion millbase with a high pigment concentration using a medium or a portion of components (A), (B), and (D), adding component (C) as needed, and diluting with an aqueous medium such as component (D). By preparing a pigment dispersion millbase in advance by dispersing the pigment using a stirring / dispersing device, and then preparing the pigment dispersion, an aqueous pigment dispersion in which the pigment is dispersed with the desired volume average particle size can be easily obtained. Hereinafter, the latter method of preparing a pigment dispersion millbase liquid and then converting it into a pigment dispersion will be described.

[0085] Examples of methods for producing a pigment dispersion millbase include the following methods. (1) A method of preparing a pigment dispersion millbase by adding a pigment to an aqueous medium containing a pigment dispersant as needed, and then dispersing the pigment in the aqueous medium using a stirring and dispersing device. (2) A method in which a pigment and, if necessary, a pigment dispersant are kneaded using a kneading machine such as a two-roll mill or a mixer, and the resulting kneaded mixture is added to an aqueous medium, followed by preparing a pigment dispersion millbase using a stirring and dispersing device. (3) A method in which a pigment dispersant is dissolved in an organic solvent compatible with water, such as methyl ethyl ketone or tetrahydrofuran, and a pigment is added to the resulting solution, and the pigment is dispersed in the organic solution using a stirring and dispersing device. Subsequently, an aqueous medium is used to effect phase inversion emulsification, and the organic solvent is then distilled off to prepare a pigment dispersion millbase.

[0086] 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, and a Nanomizer. One of these devices may be used alone, or two or more types of devices may be used in combination.

[0087] <Inkjet ink> The pigment dispersion of the present invention is 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, as with component (D), a mixture of water and an organic solvent, or an organic solvent only. The organic solvent is not particularly limited as long as it is miscible with water, and examples thereof include those described above as optional components for "solvents other than water." In addition, optional components of the pigment dispersion (for example, preservatives, surface tension adjusters, etc.) can also be contained in the aqueous medium.

[0088] <Printed material> The inkjet ink of the present invention has excellent adhesion to various substrates, and in particular, because it has excellent adhesion to plastic substrates, it can be suitably used to produce printed matter in the field of flexible packaging used for food, daily necessities, pharmaceuticals, etc., which has a plastic substrate and a printed layer made of inkjet ink.

[0089] 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; and thermoplastic resins such as polyvinyl chloride, polyimide resins, polyarylate resins, and mixtures thereof, as well as laminates of these. Of these, substrates made of polyester, polyamide, polyethylene, polypropylene, and polyvinyl chloride are particularly suitable.

[0090] The plastic substrate may be a plastic film. The plastic film may be an unstretched film or a stretched film, and the manufacturing method is not limited. The thickness of the film is also not particularly limited, but is usually in the range of 1 to 500 μm. The printed surface of the film is preferably subjected to a corona discharge treatment, and silica, alumina, etc. may be vapor-deposited on the printed surface.

[0091] The printed matter of the present invention has good adhesion to plastic substrates and can be produced by inkjet printing, making it suitable for use as a packaging material. In particular, it has excellent design properties and on-demand printability, making it particularly suitable for use in food packaging. Furthermore, since the inkjet ink of the present invention has excellent abrasion resistance, the printed matter of the present invention can also be a surface-printed printed matter in which inkjet printing is performed on the surface. [Example]

[0092] The present invention will be specifically described below with reference to examples and comparative examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0093] (Examples 1 to 5 and Comparative Examples 1 to 4) [Example 1] <Preparation of dispersion resin> A 2-liter stainless steel flask was charged with 600 g of methyl ethyl ketone (MEK), and the mixture was heated to 80°C in an oil bath while blowing in nitrogen at 20 mL / min and stirring at 100 rpm. A mixture of 84.5 g of methacrylic acid, 215.0 g of styrene, 200.0 g of butyl methacrylate, and 18.0 g of Perbutyl® O (NOF Corporation) was added dropwise to the flask at 2 g / min. The mixture was then stirred for 16 hours while maintaining the internal temperature at 80°C, yielding a dispersion resin A with a nonvolatile content of 45%, an acid value of 110, and a mass-average molecular weight of 20,000.

[0094] <Preparation of neutralized dispersion resin solution> A 10 L glass separable flask was charged with 1284.58 g of ion-exchanged water, 315.42 g of methyldiethanolamine (MDEA, boiling point 247°C) (neutralization rate 150%), and 2000 g of dispersion resin A, and the mixture was stirred. An additional 3300 g of ion-exchanged water was then added, and the mixture was heated with stirring to distill off MEK and water, yielding a 150% MDEA neutralized solution of dispersion resin A with a resin content of 18.82%.

[0095] <Preparation of pigment dispersion> A 5L plastic container was charged with 474.58g of ion-exchanged water, 557.92g of 150% neutralized MDEA dispersion resin A, 17.5g of Surfynol 465, 0.805g of BYK-019 as an antifoaming agent, and 700g of phthalocyanine pigment (DIC Corporation, FASTOGEN BLUE SBG-SD) and stirred for 1 hour using a Dispermat to obtain a slurry. The slurry was then placed in an SC100 mill (Nippon Coke Company) and dispersed with 440g of 0.5mm zirconia beads (Nikkato Corporation, YTZ). After dispersion, the beads were removed and the resulting dispersion was adjusted with ion-exchanged water to a pigment content of 29%. The mixture was then centrifuged (6000g for 30 minutes) to remove coarse particles, followed by filtration using an 8um pore size membrane filter (Merck Millipore, nitrocellulose) to obtain a pigment dispersion.

[0096] <Preparation of inkjet ink> The prepared pigment dispersion was mixed with water-soluble solvents and other ingredients to obtain an aqueous inkjet ink with a pigment concentration of 5%, an acrylic binder (acrylic emulsion manufactured by Seiko PMC, acid value 30°C, Tg 20°C) concentration of 1.5%, an oxidized polyethylene wax (manufactured by Keim Additec) concentration of 1.1%, a total of 28% water-soluble solvents (propylene glycol 10%, 1.3-butanediol 5%, 1.2-hexanediol 3%, 2-pyrrolidone 10%), and preservative and surface tension modifier concentrations of 0.1-1.0%.

[0097] [Example 2] A pigment dispersion and a water-based inkjet ink were obtained in the same manner as in Example 1, except that in the preparation process of the dispersion resin neutralization liquid, MDEA was replaced with dimethylethanolamine (DMEA, boiling point 133°C) and an amount equivalent to a 100% neutralization rate was added.

[0098] [Example 3] An aqueous inkjet ink was obtained in the same manner as in Example 1, except that in the inkjet ink preparation process, a polyester binder (Elitel KA-5071S manufactured by Unitika) was used instead of the acrylic binder.

[0099] [Example 4] An aqueous inkjet ink was obtained in the same manner as in Example 2, except that a polyester binder (Elitel KA-5071S manufactured by Unitika) was used instead of the kuril binder in the inkjet ink preparation process.

[0100] [Example 5] An aqueous inkjet ink was obtained in the same manner as in Example 2, except that in the inkjet ink preparation process, a polyurethane binder (polyether polyol polyurethane resin XPD3253 manufactured by Lubrizol Corporation) was used instead of the acrylic binder.

[0101] [Comparative Example 1] An aqueous inkjet ink was obtained in the same manner as in Example 1, except that no acrylic binder was used in the inkjet ink preparation process.

[0102] Comparative Example 2 An aqueous inkjet ink was obtained in the same manner as in Example 2, except that the acrylic binder was not used in the inkjet ink preparation process.

[0103] Comparative Example 3 A pigment dispersion and a water-based inkjet ink were obtained in the same manner as in Example 3, except that in the preparation of the dispersion resin neutralization liquid, potassium hydroxide was added in an amount corresponding to a neutralization rate of 100% instead of MDEA.

[0104] Comparative Example 4 A pigment dispersion and a water-based inkjet ink were obtained in the same manner as in Example 1, except that in the step of preparing the dispersion resin neutralization liquid, MDEA was replaced with ammonia water in an amount corresponding to a neutralization rate of 100%.

[0105] <Creating printed materials for evaluation> The inkjet ink of each example was filled into an ink cartridge of an inkjet printer (MJ-510C, manufactured by Seiko Epson Corporation), and a solid pattern was printed on a corona-treated biaxially stretched polypropylene (OPP) film ("Pylen P2161" manufactured by Toyobo Co., Ltd., thickness 20 μm), a corona-treated (PVC) film ("LSPVC1270f" manufactured by Sakurai Corporation, thickness 140 μm), or a corona-treated polyethylene terephthalate (PET) film ("Ester E5100" manufactured by Toyobo Co., Ltd., thickness 12 μm). The printed material was then dried with a hair dryer and further dried in an oven at 90° C. for 10 minutes to obtain a printed material.

[0106] <Odor test> The amine odor of the pigment dispersion at room temperature was evaluated sensorily according to the following evaluation criteria. ○: Almost odorless ×: Strong smell

[0107] <Storage stability> The viscosity of each inkjet ink was measured and the ink was left to stand in a thermostatic chamber at 70°C for one week. The viscosity was then measured again and the storage stability was evaluated according to the following calculation formula and evaluation criteria. A score of B or higher was considered acceptable. Storage stability = |1-(viscosity after storage) / (viscosity before storage)| x 100 (formula) A: 0 or more and less than 5 B: 5 or more but less than 10 C: 10 or more but less than 20 D: 20 or more

[0108] <Dry abrasion resistance> In accordance with JIS K5701-1:2000, the abrasion resistance of printed matter printed on PET film using each inkjet ink was evaluated using a Gakushin-type abrasion fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.). The printed matter was set in the tester, and the dry abrasion test was carried out using PPC paper as the abrasion paper, a load of 200 g, and 100 strokes back and forth. After the test, the degree of ink peeling from the printed matter was visually evaluated according to the following evaluation criteria. A grade of B or higher was considered a pass. A: No peeling occurred at all. B: Less than 1% peeling occurred. C: Peeling occurred at 1% or more and less than 5%. D: Peeling occurred at 5% or more but less than 10%.

[0109] [Table 1]

[0110] As is clear from the above results, it was confirmed that the inkjet inks of Examples 1 to 5, which used the pigment dispersions of Examples 1 to 5 according to the present invention, did not emit odors during production and had excellent abrasion resistance. On the other hand, the inkjet inks of Comparative Examples 1 to 4, which used the comparative pigment dispersions of Comparative Examples 1 to 4, were inferior in any of the above properties.

[0111] (Examples 6-7 and Comparative Examples 5-6) Pigment dispersions and aqueous inkjet inks of Examples 6 to 7 and Comparative Examples 5 to 6 were obtained in the same manner as in Examples 3 and 4 and Comparative Examples 1 and 2, except that the component (C), the neutralizing agent used, and the neutralization ratio were as shown in the table below.

[0112] <Alcohol tolerance> In accordance with JIS K5701-1:2000, the alcohol resistance of printed matter printed on PET film using each inkjet ink was evaluated using a Gakushin-type rub fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.). The printed matter was placed in the tester, and the rubbed paper was Kanakin No. 3 wetted with 75% ethanol (EtOH), with a load of 200 g and 10 strokes. After the test, the degree of ink peeling on the printed matter was visually evaluated according to the following criteria. A grade of B or higher was considered a pass. A: Less than 10% peeling occurred. B: Peeling occurred at 10% or more but less than 30%. C: Peeling occurred at 30% or more but less than 50%. D: Peeling of 50% or more was observed.

[0113] [Table 2]

[0114] As is clear from the above results, it was confirmed that the inkjet inks using the pigment dispersions of Examples 6 and 7 according to the present invention have superior alcohol resistance compared to the inkjet inks using the comparative pigment dispersions of Comparative Examples 5 and 6.

[0115] Therefore, it was confirmed that the inkjet pigment dispersion and inkjet ink of the present invention do not generate odors during production and can be suitably used for inkjet printing. In addition, the pigment dispersion and inkjet ink of the present invention have excellent abrasion resistance and alcohol resistance, and therefore are suitable for printing on various substrates such as plastic films, and can be widely used in applications such as packaging and sign displays, and it has been confirmed that they can also be applied to surface printing.

[0116] [Example 8] <Preparation of dispersion resin> A 2L stainless steel flask was charged with 600g of isopropyl alcohol, blown in nitrogen at 20mL / min, and heated to 80°C in an oil bath while stirring at 100 rpm. A premix of 82.7g of methacrylic acid, 153.25g of styrene, 88.65g of butyl methacrylate, 73.44g of 2-hydroxyethyl methacrylate, 88.65g of butyl acrylate, 6.58g of 2,2-azobis(2-methylbutyronitrile), 6.58g of 4,4-azobis-valeric acid, and 0.33g of 3-mercapto-1,2-propanediol (thioglycerol) was added dropwise to the flask at 2g / min. The internal temperature was then maintained at 80°C and stirring was continued for 16 hours to obtain a dispersion resin B with a non-volatile content of 45%, an acid value of 110, and a mass average molecular weight of 20,000.

[0117] <Preparation of neutralized dispersion resin solution> A 150% MDEA neutralized solution of dispersion resin B with a resin content of 18.82% was obtained in the same manner as in Example 1, except that dispersion resin A was changed to dispersion resin B.

[0118] <Preparation of pigment dispersion> A pigment dispersion was obtained in the same manner as in the preparation of the pigment dispersion of Example 1, except that the 150% MDEA neutralized solution of dispersion resin A was changed to the 150% MDEA neutralized solution of dispersion resin B.

[0119] <Preparation of inkjet ink> An aqueous inkjet ink was obtained in the same manner as in Example 1, except that in the inkjet ink preparation process, a polyester binder (Elitel KA-5071S manufactured by Unitika) was used instead of the acrylic binder.

[0120] [Example 9] An aqueous inkjet ink was obtained in the same manner as in Example 8, except that in the inkjet ink preparation process, the polyester binder concentration was changed to 2.5%.

[0121] [Example 10] An aqueous inkjet ink was obtained in the same manner as in Example 9, except that in the inkjet ink preparation process, the polyester binder was changed to a polyester binder (Elitel KT-9511 manufactured by Unitika).

[0122] [Example 11] An aqueous inkjet ink was obtained in the same manner as in Example 9, except that in the inkjet ink preparation process, the polyester binder was changed to a polyester binder (Elitel KT-8803 manufactured by Unitika).

[0123] [Example 12] A pigment dispersion and a water-based inkjet ink were obtained in the same manner as in Example 9, except that in the preparation process of the dispersion resin neutralization liquid, MDEA was replaced with dimethylethanolamine (DMEA, boiling point 133°C) and an amount equivalent to a 100% neutralization rate was added.

[0124] [Example 13] An aqueous inkjet ink was obtained in the same manner as in Example 12, except that in the inkjet ink preparation process, the polyester binder was changed to a polyester binder (Elitel KT-8803 manufactured by Unitika).

[0125] [Example 14] A pigment dispersion and a water-based inkjet ink were obtained in the same manner as in Example 9, except that in the preparation process of the dispersion resin neutralization liquid, MDEA was replaced with triisopropanolamine (TIPA, boiling point: approximately 300°C) and an amount equivalent to a neutralization rate of 150% was added.

[0126] [Table 3]

[0127] As is clear from the results in Table 3, it was confirmed that the inkjet inks using the pigment dispersions of Examples 8 to 18 according to the present invention did not emit odors during production and had excellent abrasion resistance.

Claims

1. A pigment dispersion for inkjet use, comprising a dispersant (A), a pigment (B), and water (D), The dispersant (A) contains at least a non-crosslinked resin (A1) having a structural unit (a1) derived from an acid group-containing monomer and a structural unit (a2) other than the structural unit (a1), The structural unit (a2) includes a structural unit derived from butyl (meth)acrylate, The mass average molecular weight of the resin (A1) is in the range of 2,0000 to 100,000, the acid value of the resin (A1) is 80 mgKOH / g or more and 110 mgKOH / g or less, In the resin (A1), the acid groups in the structural unit (a1) are neutralized with an alkanolamine at a neutralization rate of 100% or more and 200% or less, where the neutralization rate when the acid groups are neutralized in a theoretical equivalent amount is 100%, and 1. A pigment dispersion for inkjet use, wherein the alkanolamine is selected from the group consisting of methyldiethanolamine, dimethylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-(3-aminopropyl)diethanolamine, and triisopropanolamine.

2. A pigment dispersion for inkjet according to claim 1, wherein the structural unit (a2) includes a structural unit derived from butyl acrylate and a structural unit derived from butyl methacrylate.

3. The pigment dispersion for inkjet recording according to claim 1, wherein the structural unit (a2) comprises a structural unit derived from 2-hydroxyethyl (meth)acrylate.

4. The pigment dispersion for inkjet recording according to claim 1 or 2, further comprising a surfactant.

5. An aqueous inkjet ink comprising the inkjet pigment dispersion according to claim 1 or 2.

6. A printed matter printed with the aqueous inkjet ink according to claim 5.

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