Pigment dispersion for inkjet ink, inkjet ink, and printed matter

Abstract

The present invention relates to a pigment dispersion for inkjet, an inkjet ink using the pigment dispersion for inkjet, and a printed matter printed with the inkjet ink, the pigment dispersion for inkjet being characterized by containing a dispersant (A), a pigment (B), and water (C), and the dispersant (A) containing a non-crosslinked resin (A1) having at least a structural unit (a1) derived from an acid group-containing monomer, in the resin (A1), a tertiary alkanolamine is used to neutralize the acid group in the structural unit (a1) at a neutralization rate exceeding 100% and being 200% or less, based on a neutralization rate of 100% when the acid group is neutralized in a theoretical equivalent amount, the tertiary alkanolamine having 2 to 3 hydroxyl groups in the structure, and a boiling point of 150 to 330°C.

Description

Technical Field

[0001] This invention relates to a pigment dispersion for use in water-based inkjet inks, water-based inkjet inks prepared using the pigment dispersion, and printed matter produced by inkjet printing using the inkjet ink. Background Technology

[0002] Against the backdrop of worsening air pollution caused by VOCs and the expanding global warming, there is a growing trend towards shifting away from petroleum-based resources due to sustainability concerns, occupational safety and health concerns, and concerns about flammability and explosiveness. This has led to stricter restrictions on the use of organic solvents. Consequently, in the printing ink industry, water-based inks have been developed to replace the organic solvents in solvent-based printing inks with water. For inkjet inks, there is also a need to develop and improve water-based inks.

[0003] On the other hand, due to population growth, rising income levels, and changes in logistics systems, the global consumption of plastic film for packaging is increasing, and the production of packaging inks is also increasing year by year.

[0004] Previously, solvent-based flexographic inks and solvent-based gravure inks were the mainstream methods for printing on film substrates. However, these printing methods have the following problems: increased costs due to the need for plate making, and time required before printing. Therefore, in film encapsulation printing, the demand for inkjet printing, which does not require plate making and can be printed on demand, is increasing. In addition, there is also an increasing demand for on-demand printing on film substrates for purposes other than encapsulation, such as film printing for indoor and outdoor signage and display applications.

[0005] However, compared to solvent-based inkjet inks, water-based inkjet inks suffer from insufficient abrasion resistance. In printing on film substrates, the mainstream method is back-side printing, which involves printing on the back of the film substrate. However, in terms of printing and processing speed, surface printing, which involves printing on the surface of the film substrate, is faster. Surface printing has advantages when productivity and cost are paramount. However, in surface printing, the printing surface is in contact with the external environment without being separated from the substrate, thus requiring both the printing surface and the ink itself to have high abrasion resistance. Inkjet inks with both abrasion resistance and surface resistance can be used not only for back-side printing but also for surface printing on films, increasing versatility. Therefore, an inkjet ink with excellent abrasion resistance is desired.

[0006] On the other hand, while attempts have been made to improve the abrasion resistance of water-based inkjet inks, the result has been the formation of agglomerates, raising concerns about reduced filterability and ink ejection performance. The ink ejection reliability issue unique to inkjet printing arises from nozzle clogging during the ink-free printing period (open time) due to the drying of some ink ejected from the printhead. For inkjet inks, excellent ink resolvability is desired to reduce this nozzle clogging.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2019-196423 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] Patent Document 1 discloses an inkjet ink with excellent water and alcohol resistance, suitable for film printing. This ink is characterized by the acid value of the dispersant being neutralized by ammonia, and the resin emulsion possessing specific Tg and acid values. In Patent Document 1, solvent resistance is evaluated by rubbing with a cotton swab soaked in solvent; it is known that a certain degree of abrasiveness can be obtained through the composition of Patent Document 1. However, Patent Document 1 does not evaluate filterability, resolubility, or abrasive resistance during drying; further improvement in abrasive resistance is desired.

[0012] Furthermore, in the invention described in Patent Document 1, since ammonia is used during neutralization, there are problems caused by odors generated during manufacturing and odors remaining in the composition itself. Moreover, since ammonia is highly volatile, there is a possibility that nozzle clogging may occur due to the volatilization of the ammonia used during neutralization.

[0013] The problem to be solved by the present invention is to provide an inkjet ink, an inkjet pigment dispersion that can be used in the inkjet ink, and a printed matter made by inkjet printing using the inkjet ink. The inkjet ink has good abrasion resistance when printed on various substrates such as plastic substrates, excellent filtration and ink discharge during inkjet printing, and does not produce odor during manufacturing.

[0014] Technical means to solve the problem

[0015] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that the problems could be solved by using the following pigment dispersion, thereby completing the present invention. The pigment dispersion utilizes a specific tertiary alkyl alcohol amine to neutralize part or all of the acid groups in the dispersant resin, and further uses a non-crosslinked resin as the dispersant.

[0016] That is, the present invention relates to the following invention.

[0017] (1) A pigment dispersion for inkjet printing, characterized in that it comprises a dispersant (A), a pigment (B), and water (C).

[0018] The dispersant (A) described above contains a non-crosslinked resin (A1), which has at least one structural unit (a1) derived from an acid-containing monomer.

[0019] In the above resin (A1), the neutralization rate when neutralizing acid groups at the theoretical equivalent is set to 100%, and tert-alkanolamine is used to neutralize the above acid groups in structural unit (a1) at a neutralization rate of more than 100% but less than 200%.

[0020] The aforementioned tert-alkanolamines have 2 to 3 hydroxyl groups in their structure and a boiling point of 150 to 330 °C.

[0021] (2) The inkjet pigment dispersion as in (1), wherein the acid value of the resin (A1) is 80 to 225 mg KOH / g.

[0022] (3) The inkjet pigment dispersion as in (1) or (2) further contains a binder (D).

[0023] (4) An inkjet pigment dispersion of any one of (1) to (3) for printing on a plastic substrate.

[0024] (5) An inkjet ink that uses an inkjet pigment dispersion of any one of (1) to (4).

[0025] (6) A printed matter made by printing with inkjet ink of (5).

[0026] Invention Effects

[0027] According to the present invention, a water-based inkjet ink can be obtained that has good friction properties even when used on plastic substrates, excellent filtration and ink discharge properties during inkjet printing, and does not produce odors during manufacturing. Detailed Implementation

[0028] Pigment dispersions for inkjet printing

[0029] 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), and water (C), and is used to prepare inkjet inks. Hereinafter, "dispersant (A)" is sometimes referred to as "component (A)," and the other components are sometimes referred to in the same way.

[0030] The pigment dispersion of the present invention is manufactured as an intermediate product for inkjet inks and can be used as an aqueous inkjet ink for inkjet printing after dilution.

[0031] <Dispersant (A)>

[0032] The dispersant (A) contains a non-crosslinked resin (A1), which has at least one structural unit (a1) derived from an acid-containing monomer. Furthermore, in the dispersant (A), the aforementioned acid group in the structural unit (a1) is neutralized by a tertiary alkyl alcohol amine.

[0033] (Resin (A1))

[0034] Resin (A1) is a non-crosslinked resin having "structural units (a1) derived from acid-containing monomers and structural units (a2) other than (a1)". It can be obtained by polymerizing acid-containing monomers with monomers other than those present using known methods such as free radical polymerization in the presence of any polymerization initiator. By giving resin (A1) acid groups, hydrophilicity is imparted to resin (A1), enabling pigments to be stably dispersed in water.

[0035] Among the acid-containing monomers from which the structural unit (a1) is derived, examples of acid groups include carboxyl groups, sulfonic acid groups, phosphate groups, and thiocarboxyl groups. Ethylene unsaturated monomers having these groups can be used as raw material monomers for the structural unit (a1).

[0036] Examples of unsaturated monomers containing carboxyl groups include: unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and 4-vinylbenzoic acid; and polybasic acid unsaturated esters such as vinyl succinate, allyl maleate, vinyl terephthalate, and allyl trimellitate.

[0037] In addition, examples of vinyl unsaturated monomers containing sulfonic acid groups include: sulfonated alkyl or aryl esters of unsaturated carboxylic acids such as 2-sulfoethyl acrylate and 4-sulfophenyl methacrylate; sulfonated carboxylic acid unsaturated esters such as vinyl sulfosuccinate; and sulfonated styrene derivatives such as styrene-4-sulfonic acid.

[0038] Among them, the monomers from which the structural unit (a1) is derived are preferably monomers with carboxyl groups as acid groups, taking into account the availability and price of the raw material monomers, and more preferably unsaturated carboxylic acids, preferably acrylic acid or methacrylic acid.

[0039] Hereinafter, the term "(meth)acrylic acid" is sometimes used to refer to both acrylic acid and methacrylic acid, and "(meth)acrylate" is sometimes used to refer to both acrylate and methacrylate. The same applies to similar acrylic compounds.

[0040] As structural unit (a2) other than structural unit (a1), examples of vinyl unsaturated monomers that can copolymerize with (a1) include: methyl methacrylate, ethyl methacrylate, methyl methacrylate, butyl methacrylate, and other methacrylates; dimethyl maleate, dimethyl fumarate, 2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate, and other unsaturated fatty acid esters; methacrylamide, N-methyl(meth)acrylamide, and other unsaturated fatty acid amides; methacrylonitrile and other unsaturated nitriles; vinyl acetate, vinyl propionate, and other unsaturated esters; styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, etc. Styrene derivatives such as tert-butylstyrene, 4-methoxystyrene, and 4-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-chloropropene; vinyl-substituted heterocyclic compounds such as 4-vinylpyridine, N-vinylcarbazole, and N-vinylpyrrolidone; reaction products of monomers containing substituents with active hydrogen such as carboxyl, hydroxyl, and amino groups as listed above with epoxides such as ethylene oxide, propylene oxide, and cyclohexane oxide; reaction products of monomers containing substituents such as hydroxyl and amino groups as listed above with carboxylic acids such as acetic acid, propionic acid, butyric acid, hexanoic acid, decanoic acid, and dodecanoic acid; etc.

[0041] Among them, the monomers that derive the structural unit (a2) are preferably (meth)acrylates or styrene-based monomers, and more preferably butyl (meth)acrylate, styrene, or α-methylstyrene, from the perspective of obtaining the effect of enhancing the adsorption force of the resin (A1) on the pigment.

[0042] As a structural unit (a2), further considering its excellent effect of improving discharge performance, it is also preferred to contain methoxy polyethylene glycol monomethacrylate as a monomer.

[0043] The resin (A1) is a non-crosslinked resin. In this invention, "non-crosslinked resin (A1)" means that the resin (A1) is synthesized or manufactured without deliberately using compounds commonly used as crosslinking agents, or without undergoing a conventional crosslinking process. The crosslinking rate of the resin (A1) manufactured without the addition of a crosslinking agent or without a deliberate crosslinking process is 5% or less, preferably 3% or less, and most preferably 0%. The non-crosslinked resin (A1) is essentially a linear resin. The above-mentioned crosslinking rate is a theoretical value, set at 100% when the crosslinking dosage is 1 molar equivalent, and at 50% when it is 0.5 molar equivalent.

[0044] In this invention, the abrasion resistance is improved by using an alkanolamine (described later), thus eliminating the need for crosslinking of the resin (A1) to ensure abrasion resistance. Furthermore, since the resin (A1) is non-crosslinked, the redissolvability of the dispersion and the ink is excellent, resulting in superior ink discharge properties and suppressing defects such as nozzle clogging. Additionally, since no crosslinking process is involved in the manufacture of the resin (A1), it is expected that the manufacturing process will be shortened and energy consumption reduced.

[0045] From the perspective of easily setting the pigment dispersion to a suitable viscosity, achieving good dispersion stability, and ensuring long-term stable printing when producing inkjet ink, 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.

[0046] The acid value of the resin (A1) is generally 80–350 mg KOH / g, preferably 80–225 mg KOH / g, more preferably 80–220 mg KOH / g, and particularly preferably 100 mg KOH / g or more but less than 200 mg KOH / g. Additionally, it is also preferred to have an acid value of less than 170 mg KOH / g.

[0047] By setting the dispersion within the above range, the hydrophilicity of the dispersant and the adsorption of the pigment are balanced, thereby improving the dispersion stability of the pigment dispersion.

[0048] In this invention, by setting the resin (A1) to be non-crosslinked, good resolubility can be obtained even when the oxidation of the resin (A1) is relatively low (e.g., less than 200 mg KOH / g).

[0049] The glass transition point of the resin (Al) is preferably 30 to 130°C, more preferably 50 to 120°C, and particularly preferably 80 to 110°C.

[0050] In the dispersant (A), a tertiary alkyl alcohol amine (hereinafter sometimes simply referred to as "alkyl alcohol amine") having 2 to 3 hydroxyl groups in its structure and a boiling point of 150 to 330 °C is used to neutralize some or all of the acid groups in the structural unit (a1).

[0051] As an alkanolamine, it is preferably a compound in which two of the three hydrogen atoms of ammonia (NH3) are replaced by an "organogroup having a hydroxyl group" and the remaining one is replaced by an organic group, or a compound in which all three hydrogen atoms are replaced by an "organogroup having a hydroxyl group". The organic group replacing the hydrogen atom is preferably an alkyl group having 1 to 3 carbon atoms, and the "organogroup having a hydroxyl group" replacing the hydrogen atom is preferably a group with a hydroxyl group bonded to an alkyl group having 1 to 3 carbon atoms.

[0052] As an alkanolamine, the preferred compound is the one represented by formula (I).

[0053]

[0054] (In formula (I), R) 1 ~R 2 Each is an organic group with a hydroxyl group, R. 3 (It is an organic group or an organic group containing a hydroxyl group).

[0055] The boiling point of the alkanolamine is 150–330°C, preferably 200–330°C, more preferably 200–320°C, and even more preferably 220°C–310°C.

[0056] By using alkanolamines with a boiling point below 330°C during neutralization, the alkanolamines volatilize well during print drying, and unlike ammonia, they do not produce an unpleasant odor. Furthermore, if alkanolamines with a boiling point above 150°C are used, they will not volatilize at the inkjet nozzles, thus reducing the likelihood of nozzle clogging and decreased ejection performance.

[0057] Examples of tertiary alkyl alcohol amines with boiling points of 150–330 °C include: dialkyl alcohol amines such as N-methyldiethanolamine, N-ethyldiethanolamine, and N-(3-aminopropyl)diethanolamine; and trialkyl alcohol amines such as triisopropanolamine.

[0058] The preferred form is a tert-alkanolamine with 2 to 9 carbon atoms, and particularly preferred are methyldiethanolamine or triisopropanolamine.

[0059] There are no particular limitations to the neutralization method using alkanolamines. For example, alkanolamines can be added to resins (A1) in organic solvents obtained through monomer synthesis, and water can be added as needed to neutralize them.

[0060] Neutralization can be carried out alone or in combination with other neutralizing agents. Other neutralizing agents include metal salts.

[0061] Examples of metal salts include: sodium hydroxide, potassium hydroxide, lithium hydroxide, and other metal hydroxides; sodium chloride, potassium chloride, and other metal chlorides; and copper sulfate, and other metal sulfides.

[0062] Regarding the ratio of alkanolamine to metal salt when used together, when the neutralization rate is 150%, it is preferably set to alkanolamine:metal salt = 60-120%:30-90%, totaling 150%. When the neutralization rate is not 150%, it is preferable to use the same ratio of alkanolamine and metal salt.

[0063] By using metal salts in combination, a balance can be achieved between abrasion resistance and solubility. However, when using metal salts, there are also problems such as unsuitability for printing in food packaging applications. Therefore, it is preferable to study the use of metal salts in combination.

[0064] Regarding neutralization, it is possible to neutralize only a portion of the acid groups or to neutralize all the acid groups, with neutralization of all acid groups being preferred.

[0065] Specifically, the neutralization rate when neutralizing the acid groups of resin (A1) with theoretical equivalent is set to 100%, and the neutralization rate is more than 100% but less than 200%, preferably 120-200%, and more preferably 150-200%. By setting such a neutralization rate, the solubility and filterability of resin (A1) are improved.

[0066] The dispersant (A) may consist of resin (A1) alone, or it may contain other components besides resin (A1).

[0067] In the pigment dispersion of the present invention, the dispersant (A) preferably contains 5 to 100% by mass relative to the pigment in terms of non-volatile components, more preferably 10 to 80% by mass. If it is within these ranges, the decrease in dispersion stability of the pigment dispersion caused by excess or deficiency of the dispersant can be suppressed, and it can maintain a stable state during long-term storage.

[0068] <Pigment (B)>

[0069] Pigment (B) is not particularly limited as long as it can be well dispersed in the dispersion, but it is preferred to use pigments that can be dispersed with an average particle size of 10 to 400 nm (details will be described below). For example, organic pigments, inorganic pigments, and dyes used in general inks, coatings, and recording agents can be used.

[0070] Organic pigments include: azo, phthalocyanine, anthraquinone, perylene, pyrene, quinacridone, thioindole, dioxazine, isoindolineone, quinolineone, azomethylazo, pyrrolopyrroledione, and isoindoline pigments. Regarding blue inks, copper phthalocyanine is preferred due to its cost and lightfastness.

[0071] Examples of inorganic pigments include: carbon black, titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silicon dioxide, red lead, and mica. Additionally, glossy pigments made by coating metals or metal oxides onto a base material of glass flakes or bulk flakes can be used (Metashine; Nippon Sheet Glass Co., Ltd.). From the perspectives of cost and tinting strength, titanium dioxide is preferred for white inks, carbon black for black inks, aluminum for gold and silver inks, and mica for pearlescent inks.

[0072] As described above, in the dispersion, the pigment is preferably dispersed with a volume average particle size of 10 to 400 nm. Regarding the average particle size of the pigment, after preparing the dispersion, the pigment is uniformly dispersed in the dispersion, and the volume average particle size is measured in this state using known methods such as dynamic light scattering. The volume average particle size 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. By ensuring a volume average particle size of 50 nm or more, pigment aggregation during storage of the pigment dispersion can be suppressed. Furthermore, by ensuring a volume average particle size of 400 nm or less (particularly preferably 100 nm or less), ink dischargeability is improved.

[0073] The pigment content in the dispersion is not particularly limited, but it is preferably 10-30% by mass in the total 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. Furthermore, if it is more than 30% by mass, depending on the type of pigment, pigment agglomeration may occur during dispersion transport and storage, in which case dispersibility at an average particle size of 50-400 nm cannot be guaranteed. Additionally, depending on the degree of dilution, there is a concern about deterioration in ink dischargeability.

[0074] In the dispersion of the present invention, the pigment concentration is preferably 10 to 30% by mass when the pigment is an organic pigment or carbon black, and more preferably 10 to 25% by mass. If it is within these ranges, when diluting and adjusting to produce inkjet ink, both ink tinting strength and ink discharge properties can be appropriately balanced.

[0075] Furthermore, when the pigment is an inorganic pigment, the preferred concentration is 25-60% by mass, more preferably 30-50% by mass.

[0076] <Other arbitrary ingredients>

[0077] The pigment dispersion of the present invention may also contain any other components besides components (A), (B), and water (C) without impairing the effects of the present invention.

[0078] Other components include, for example: adhesives (D), amine compounds with a boiling point of 100°C or higher (E), other resins besides those listed above, solvents other than water, surfactants, waxes, low surface tension organic solvents, wetting agents, penetrants, dispersants other than those listed above, defoamers, preservatives, viscosity modifiers, pH modifiers, chelating agents, plasticizers, antioxidants, ultraviolet absorbers, etc.

[0079] <Adhesive (D)>

[0080] The binder (D) is a substance added to further improve the substrate adhesion and abrasion resistance of the ink. In this invention, since the abrasion resistance is improved by using the aforementioned tert-alkanolamine, sufficient abrasion resistance can be ensured even without the use of the binder (D).

[0081] If the binder (D) has pigment dispersing ability, there is a possibility that the binder (D) will cause the dispersant (A) to detach from the pigment, thereby reducing the dispersion stability of the pigment dispersion. Therefore, the binder (D) preferably does not have pigment dispersing ability.

[0082] As a preferred adhesive, acrylic adhesives (D1) can be cited as an example.

[0083] (Acrylic adhesive (D1))

[0084] As an acrylic adhesive (D1), an acrylic aqueous resin emulsion is preferred.

[0085] Examples of acrylic emulsions include acrylic emulsions, styrene-acrylic emulsions, acrylic-maleic emulsions, and styrene-acrylic-maleic emulsions. Preferred examples include acrylic emulsions and styrene-acrylic emulsions. The emulsion can be core-shell type or other types.

[0086] As structural units in emulsion resins, the structural units described in structural units (a1) and (a2) above, and the structural units that can be copolymerized with them can be listed.

[0087] Through previous research, the inventors have discovered that, regarding dry abrasion resistance, the higher the Tg of the acrylic adhesive (D1), the better the results can be obtained. On the other hand, if the Tg of the acrylic adhesive (D1) decreases, the dry abrasion resistance may decrease.

[0088] The acid value of the acrylic adhesive (D1) is preferably 5 to 100 mg KOH / g, more preferably 5 to 80 mg KOH / g, and even more preferably 20 to 50 mg KOH / g. If the acid value is less than 5 mg KOH / g, there is a possibility that the dispersion stability of the acrylic adhesive (D1) may decrease. On the other hand, if the acid value exceeds 100 mg KOH / g, the hygroscopicity of the printed coating becomes higher, and there is a possibility that the wet friction resistance may be impaired.

[0089] The glass transition point of the acrylic adhesive (D1) 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.

[0090] By setting the parameters within the above range, the drying time after printing can be shortened, which is preferred from the viewpoint of improving printing speed and saving energy.

[0091] The volume average particle size of the acrylic adhesive (D1) is preferably 20–100 nm, more preferably 20–80 nm. For example, the resin diluted with ion-exchanged water can be filled into a sample cell, and the volume average particle size can be determined using a UPA-EX150 under the following conditions.

[0092] • Load index: 5±1

[0093] • Measurement time: 180 seconds

[0094] Number of measurements: 5

[0095] • Penetration: Penetration

[0096] • Particle refractive index: 1.80

[0097] • Shape: True sphere

[0098] • Density: 1.00

[0099] Solvent refractive index: 1.333

[0100] Viscosity at high temperature: 0.797 at 30℃

[0101] Viscosity at low temperature: 1.002 at 20°C

[0102] • Filter: Stand: Norm

[0103] • Sensitivity: Standard

[0104] UPA interchangeable mode

[0105] In addition, commercially available products can also be used as acrylic adhesives (D1). Commercially available products include ME-2039XJE-509, XJE-518, XJE-520, XJE-556 (manufactured by Starlight PMC, acrylic emulsion), Joncryl 631, and Joncryl 731 (manufactured by BASF).

[0106] The adhesive (D) may further contain other components to replace the acrylic adhesive (D1) or contain other components besides the acrylic adhesive (D1). As other components, polyurethane resin is preferred; polyether polyol polyurethane resin is preferred because it is less prone to hydrolysis compared to polyester polyol polyurethane and exhibits particularly superior abrasion resistance in the colored image. Examples of such polyether polyol polyurethane resins include polyurethane resins reacted with polytetramethylene ether glycol (PTMG) and diisocyanate as essential components.

[0107] When the dispersion of the present invention contains a binder (D), the binder (D) preferably contains 10 to 200% by mass, more preferably 30 to 150% by mass, calculated as non-volatile components. If it is within these ranges, it also has the adhesion to the substrate, abrasion resistance, and adhesion resistance of inkjet ink after dilution, and is therefore preferred.

[0108] (Amine compounds with a boiling point above 100°C (E))

[0109] The pigment dispersion of the present invention preferably contains an amine compound (E) with a boiling point of 100°C or higher. By adding an amine compound (E), excessive drying of the ink is further suppressed, the ink does not cause nozzle clogging, and as a result, the discharge properties are improved, thus achieving both good discharge properties and abrasion resistance.

[0110] Examples of amine compounds (E) include: polyalkylimide, polyallylamine, (poly)ethylene polyamine, alkanolamine, and alkylamine.

[0111] From the viewpoints of pigment dispersibility, odor, and resolubility, alkanolamines are preferred.

[0112] (Polyalkylimide)

[0113] The polyalkylene imide is preferably a polyalkylene imide having an alkylene group having 2 to 5 carbon atoms.

[0114] The polyalkylene imide is preferably a polyalkylene imide with 2 to 4 carbon atoms in the alkylene group, more preferably a polyethylene imide or a polypropylene imide, and even more preferably a polyethylene imide. One or more of them may be used.

[0115] The number average molecular weight of the polyalkylimide 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, and even more preferably 4,000 or less.

[0116] The molecular weight can be determined using the method described in the examples.

[0117] (Polyallylamine)

[0118] Polyallylamines include homopolymers or copolymers of allyl compounds such as allylamine and dimethylallylamine, which are polymers with amino groups in their side chains.

[0119] The weight-average molecular weight of 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, and even more preferably 4,000 or less.

[0120] (Polyethylene polyamine)

[0121] Examples of (poly)ethylene polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. Among these, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine are preferred.

[0122] (Alkylamine)

[0123] As an alkanolamine, an alkanolamine having 2 or more but fewer carbon atoms is preferred. Examples of alkanolamines include: primary alkanolamines such as monoethanolamine, monopropanolamine, and monobutanolamine; secondary alkanolamines such as N-methylethanolamine and N-methylpropanolamine, and secondary alkanolamines such as diethanolamine and diisopropanolamine; tertiary alkanolamines such as N,N-dimethylethanolamine, N,N-dimethylpropanolamine, and N,N-diethylethanolamine, and tertiary alkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, and tertiary alkanolamines such as triethanolamine and triisopropanolamine. Among these, tertiary alkanolamines having 2 or more but fewer carbon atoms are preferred, and triisopropanolamine is particularly preferred.

[0124] (alkylamine)

[0125] As an alkylamine, an alkylamine having 1 to 6 carbon atoms is preferred. Examples of alkylamines include primary amines such as propylamine, butylamine, and hexylamine; and secondary amines such as diethylamine and dipropylamine.

[0126] In the pigment dispersion of the present invention, the amine compound (E) preferably has a neutralization rate of 30% to 500% relative to the acid group of the dispersant (A), and particularly preferably is set in the range of 50% to 400%. If it is within these ranges, it becomes an ink that does not cause nozzle clogging and has excellent adhesion and abrasion resistance.

[0127] (Components other than (A) to (E))

[0128] As other resins, aqueous resins suitable for preparing pigment dispersions are preferred. Examples of preferred resins include: polyvinyl alcohols; polyvinylpyrrolidones; acrylic resins such as acrylic-acrylate copolymers; styrene-acrylic acid copolymers; styrene-methacrylic acid copolymers; styrene-methacrylic acid-acrylate copolymers; styrene-α-methylstyrene-acrylic acid copolymers; styrene-α-methylstyrene-acrylate-acrylate copolymers; styrene-maleic acid copolymers; styrene-maleic anhydride copolymers; vinylnaphthalene-acrylic acid copolymers; and substances in the salts of the aqueous resin that are not among the above-mentioned components.

[0129] 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.

[0130] Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants or nonionic surfactants are preferred.

[0131] Examples of anionic surfactants include: alkylbenzene sulfonates, alkylphenyl sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, sulfate salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. Specific examples include dodecylbenzene sulfonate, isopropylnaphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, dibutylphenylphenol disulfonate, etc.

[0132] 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 sorbitan fatty acid esters, glycerol fatty acid esters, polyoxyethylene glycerol fatty acid esters, polyglycerol fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid hydroxyalkylamides, alkylalkanolamides, acetylenide glycol, ethoxyethylene adducts of acetylenide glycol, polyethylene glycol-polypropylene glycol block copolymers, and alkylphenol ethoxides. Among these, 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 hydroxyalkylamides, acetylenide glycol, ethoxyethylene adducts of acetylenide glycol, polyethylene glycol-polypropylene glycol block copolymers, and alkylphenol ethoxides are preferred.

[0133] Other surfactants that can be used include: silicone surfactants such as polysiloxane ethylene oxide adducts; fluorinated surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl ethylene oxide ethers; and biosurfactants such as penicillic acid, rhamnolipids, and lysophosphatidylcholine.

[0134] These surfactants can be used alone or in mixtures of two or more. Furthermore, considering factors such as the solubility and stability of the surfactants, their HLB value is preferably in the range of 7 to 20.

[0135] Commercially available fluorinated surfactants include: NOVEC FC-4430, FC-4432 (manufactured by Sumitomo 3M), ZONYL FSO-100, FSN-100, FS-300, FSO (manufactured by DuPont), Eftop 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 & Manufacturing Company), Monflor (manufactured by Imperial Chemical Industries), and Lichovet VPF series (manufactured by Farbwerke Hoechst).

[0136] Examples of silicone-based surfactants include: KF-351A, KF-642, Olfine PD-501, Olfine PD-502, Olfine PD-570 (manufactured by Shin-Etsu Chemical Industry), BYK347, and BYK348 (manufactured by BYK-Chemie Japan).

[0137] Examples of polyoxyethylene alkyl ether surfactants include: BT series (Nikko Chemicals), Nonipol series (Sanyo Chemicals), D- and P- series (Takemoto Oils & Fats), EMLEX DAPE series (Nihon Emulsion), and Pegnol series (Toho Chemical Industry). Examples of polyethylene glycol alkyl ester surfactants include Pegnol (Toho Chemical Industry).

[0138] Examples of acetylene glycol surfactants include: Olfine E1010, STG, Y (manufactured by Nissin Chemical Co., Ltd.), Surfynol 104, 82, 420, 440, 465, 485, and TG (manufactured by Air Products and Chemicals Inc.).

[0139] Examples of waxes include: carnauba wax, candelilla wax, beeswax, rice bran wax, lanolin, and other plant and animal-based waxes; lignite wax, ceresin wax, and other mineral-based waxes; paraffin wax, also known as petroleum-based waxes; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, silicone wax, and stearamide; and natural and synthetic wax emulsions and compound waxes such as α-olefin-maleic anhydride copolymers. These waxes impart a smooth finish to the surface of the resulting recording material and improve its abrasion resistance. One or a mixture of these waxes can be used. Among them, silicone wax, polyolefin wax, and paraffin wax are preferred.

[0140] 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, FZ-4602 (these are trade names, manufactured by Toray Dow Corning), POLON-MF-14, POLON-MF-14EC, POLON-MF-23, P... POLON-MF-63, POLON-MF-18T, POLON-MF-56, POLON-MF-49, POLON-MF-33A, POLON-MF-55T, POLON-MF-28T, POLON-MF-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 (the above are trade names, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), etc.

[0141] Examples of polyolefin waxes include waxes and copolymers made from olefins such as ethylene, propylene, and butene or their derivatives, specifically polyethylene waxes, polypropylene waxes, and polybutene waxes. Polyolefin waxes can be used alone or in combination of two or more. Among these, polyethylene waxes are preferred from the viewpoint that they do not readily react with the crosslinking groups of polyurethane resin particles having the aforementioned crosslinking groups, thus resulting in excellent discharge stability.

[0142] Commercially available polyolefin waxes include, for example: AQUACER513 (polyethylene wax, average particle size 100nm-200nm, melting point 130℃, solids content 30%), AQUACER507, AQUACER515, AQUACER840, AQUACER1547 (trade names, manufactured by BYK-Chemie Japan), etc. (AQUACER series); HITEC E-7025P, HITEC E-2213, HITEC E-6500, HITEC E-6314, HITEC E-9460, HITEC E-9015, HITECE-4A, HITEC E-5403P, HITEC E-8237 (trade names, manufactured by Toho Chemical Co., Ltd., polyethylene wax), etc. (HITEC series); NOPCOTE PEM-17 (trade name, San...). Nopco manufactures polyethylene emulsions with an average particle size of 40 nm, ULTRALUBE E-843N (trade name, manufactured by keim additec surface GmbH, polyethylene wax), etc.

[0143] Paraffin wax is a type of petroleum-based wax. Here, paraffin hydrocarbons refer to alkanes with 20 or more carbon atoms, and paraffin wax refers to a mixture of hydrocarbons with a molecular weight of approximately 300-500, primarily composed of straight-chain paraffin hydrocarbons with 20-30 carbon atoms and containing small amounts of isoparaffin hydrocarbons. By incorporating paraffin wax into inks, the recorded material is given a smooth, water-repellent property, thereby improving its abrasion resistance.

[0144] Commercially available paraffin products include, for example, AQUACER537 and AQUACER539 (these are product names, manufactured by BYK-Chemie Japan).

[0145] The wax is preferably contained in the pigment dispersion in a particulate state, i.e., an emulsion or suspension state. This makes it easy to adjust the ink viscosity to a suitable range during inkjet head ejection, and also makes it easier to ensure ejection stability and intermittent ejection characteristics during recording.

[0146] Regarding low surface tension organic solvents, for example as glycol ether compounds, examples include diethylene glycol mono(alkyl) ethers (1 to 8 carbons), triethylene glycol mono(alkyl) ethers (1 to 8 carbons), propylene glycol mono(alkyl) ethers (1 to 6 carbons), and dipropylene glycol mono(alkyl) ethers (1 to 6 carbons). They can be used in one form or in a mixture of two or more.

[0147] Specifically, the following can be listed: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monotert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monotert-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 monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monoethyl ... Diethylene glycol monobutyl ether, triethylene glycol monopentyl ether, 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 monoisopropyl ether, propylene glycol monobutyl ether, propylene glycol monotert-butyl ether, propylene glycol monopentyl ether, propylene glycol monohexyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether, dipropylene glycol monohexyl ether, etc.

[0148] Glycol ethers, surfactants, etc., can be used as surface tension modifiers to adjust the surface tension of inks. Specifically, they can be added appropriately to make the surface tension of the ink below 15 mN / m to 30 mN / m. The amount of surfactant added is preferably in the range of about 0.1% to 10% by mass relative to the aqueous pigment dispersion, more preferably 0.3% to 2% by mass. The surface tension is more preferably in the range of 16 to 28, and most preferably in the range of 18 to 25.

[0149] There are no particular limitations on the wetting agent, but it is preferred to be a substance that is miscible with water and can achieve an anti-clogging effect on the inkjet printhead. Examples include: glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol with a molecular weight of less than 2000, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 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 1,2-heptanediol. The ink contains diols such as 1,2-nonanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-nonanediol, and 1,2-octanediol; nitrogen-containing heterocyclic compounds such as 1,4-butanediol, 1,3-butanediol, erythritol, pentaerythritol, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidineone, and ε-caprolactam. Among these, the presence of propylene glycol and 1,3-butanediol indicates safety and demonstrates excellent ink drying and expulsion performance.

[0150] The preferred content of wetting agent in ink is 3-50% by mass.

[0151] Examples of penetrants include: lower alcohols such as ethanol and isopropanol; 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% by mass.

[0152] <Methods for manufacturing pigment dispersions>

[0153] The method for manufacturing the pigment dispersion in this invention is not limited in any way.

[0154] Pigment dispersions can be prepared by dispersing components (A) to (C) and, if necessary, any additional components such as (D) and (E). Alternatively, a pigment dispersion grinding base solution with a high pigment concentration can be prepared in advance using components (A), (B), a portion of components (C), and a medium. Then, any additional components such as (D) can be added appropriately, and the solution can be diluted with an aqueous medium such as component (C) to prepare a pigment dispersion for the preparation of water-based inkjet inks. By using a stirring and dispersing device to disperse the pigment and preparing a pigment dispersion grinding base solution in advance, and then preparing the pigment dispersion, an aqueous pigment dispersion with the desired volume average particle size can be easily obtained.

[0155] The latter method is described below, which involves preparing a pigment dispersion after making a pigment dispersion grinding base liquid.

[0156] The following methods can be listed as methods for manufacturing pigment dispersion and grinding base liquid.

[0157] (1) A method for preparing a pigment dispersion grinding base liquid by adding pigment to an aqueous medium containing a pigment dispersant as needed and then using a stirring and dispersing device to disperse the pigment in the aqueous medium.

[0158] (2) A method of preparing pigment dispersion grinding base liquid by using a two-roll mill, a mixer or other mixing machine to mix pigments and pigment dispersants as needed, adding the resulting mixture to an aqueous medium and using a stirring and dispersing device.

[0159] (3) A method for preparing a pigment dispersion grinding base liquid by dissolving a pigment dispersant in an organic solvent that is compatible with water, such as methyl ethyl ketone or tetrahydrofuran, adding pigment to the resulting solution, dispersing the pigment in the organic solution using a stirring and dispersing device, performing phase inversion emulsification using an aqueous medium, and then removing the organic solvent by distillation.

[0160] Examples of mixing and dispersing devices include ultrasonic homogenizers, high-pressure homogenizers, paint vibrators, ball mills, roller mills, sand mixers, sand mills, dyno-mills, dispersers, SC mills, and nanomers. One of these devices can be used alone or in combination with two or more other devices.

[0161] Inkjet ink

[0162] Waterborne inkjet ink is prepared by diluting the pigment dispersion of the present invention with an aqueous medium at a pigment content of 1 to 30% by mass. The aqueous medium may be water, as in component (C), or a mixture of water and an organic solvent, or only an organic solvent. As for the organic solvent, there is no particular limitation as long as it is mixed with water, and the solvents described above in any component can be listed as "solvents other than water".

[0163] In addition, the aqueous medium can contain any component of the pigment dispersion (e.g., component (D), preservatives, surface tension modifiers, etc.).

[0164] <Printed Materials>

[0165] The inkjet ink of the present invention exhibits excellent adhesion to various substrates, thus enabling the suitable manufacture of printed materials having a plastic substrate and a printing layer formed by the inkjet ink.

[0166] 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 represented by aliphatic polyester resins such as polyethylene succinate and polybutylene succinate; polyolefin resins such as polypropylene and polyethylene; and thermoplastic resins such as polyvinyl chloride, polyimide resin, polyarylate resin, or mixtures thereof. Among these, substrates composed of polyester, polyamide, polyethylene, polypropylene, and polyvinyl chloride are suitable.

[0167] In addition, the plastic substrate can be a plastic film. The plastic film can be either an unstretched film or a stretched film, and its manufacturing method is not limited. Furthermore, the film thickness is not particularly limited; it generally only needs to be in the range of 1–500 μm.

[0168] In addition, corona discharge treatment is preferably applied to the printing surface of the film. Alternatively, silicon dioxide, aluminum oxide, etc., can be vapor-deposited onto the printing surface.

[0169] The printed materials of this invention exhibit excellent adhesion to plastic substrates and can be produced via inkjet printing, making them suitable for use as packaging materials. In particular, their excellent design flexibility and printability make them especially suitable for food packaging. Furthermore, the inkjet inks of this invention have excellent abrasion resistance, allowing the printed materials to also be produced as surface-printed materials by inkjet printing on a surface surface.

[0170] Example

[0171] The present invention will now be specifically described through examples and comparative examples. Unless otherwise explicitly stated, “parts” will refer to “parts by mass” and “%” will refer to “% by mass”.

[0172] [Example 1]

[0173] <Preparation of Dispersion Resin>

[0174] 600g of methyl ethyl ketone (MEK) was added to a 2L stainless steel flask. Nitrogen gas was introduced at a rate of 20mL / min, and the mixture was stirred at 100rpm while simultaneously heating to 80°C using an oil bath. 84.5g of pre-mixed methacrylic acid, 215.0g of styrene, 200.0g of butyl methacrylate, and 18.0g of PERBUTYL (registered trademark) O (manufactured by Nippon Oil Company) were added dropwise to the flask at a rate of 2g / min. The mixture was then stirred continuously for 16 hours while maintaining the internal temperature at 80°C to obtain resin A, which has a non-volatile content of 45%, an acid value of 110, and a weight-average molecular weight of 20,000.

[0175] <Preparation of Pigment Dispersions>

[0176] Add 13.6g of deionized water, 0.21g of methyldiethanolamine (MDEA, boiling point 247℃) (neutralization rate 150%), 1.3g of dispersion resin A, and 4.0g of copper phthalocyanine pigment (manufactured by DIC, TGR-SD) to a 100mL plastic container. 100g of zirconia beads (manufactured by NIKKATO, YTZ) were dispersed for 1 hour. Then, the beads were removed, MEK was thoroughly removed by distillation, the pigment concentration was adjusted to 15%, and the mixture was filtered using a membrane filter with an 8μm pore size (manufactured by Merck Millipore, nitrocellulose) to obtain the pigment dispersion.

[0177] <Making Inkjet Inks>

[0178] The prepared pigment dispersion is mixed with binder and water-soluble solvent to obtain the following water-based inkjet ink, which has a pigment concentration of 5%, a styrene-acrylic binder (manufactured by Starlight PMC, acid value 30℃, Tg 20℃) concentration of 1.5%, an oxidized polyethylene wax (manufactured by Keim Additec) concentration of 1.1%, a total water-soluble solvent concentration of 28% (propylene glycol 10%, 1,3-butanediol 5%, 1,2-hexanediol 3%, 2-pyrrolidone 10%), and a preservative and surface tension modifier concentration of 0.1-1.0%.

[0179] [Example 2]

[0180] In the pigment dispersion preparation process, 13.5g of ion-exchanged water and 0.28g of MDEA (neutralization rate 200%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 1.

[0181] [Example 3]

[0182] In the process of making the dispersion resin, 130.6g of methacrylic acid, 153.9g of butyl methacrylate, 215.0g of styrene, and 36.0g of PERBUTYL (registered trademark) were used. Otherwise, dispersion resin B with 45% non-volatile components, an acid value of 170, and a weight-average molecular weight of 8000 was obtained by the same method as in Example 1.

[0183] Furthermore, in the pigment dispersion preparation process, 13.3g of deionized water, 0.52g of triisopropanolamine (TIPA, boiling point 305°C) (neutralization rate 150%), and 1.3g of dispersion resin B were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 1.

[0184] [Example 4]

[0185] In the pigment dispersion preparation process, 13.6g of ion-exchanged water and 0.22g of MDEA (neutralization rate 101%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0186] [Example 5]

[0187] In the pigment dispersion preparation process, 13.5g of ion-exchanged water and 0.32g of MDEA (neutralization rate 150%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0188] [Example 6]

[0189] In the process of making the dispersion resin, 138.3g of acrylic acid, 0.0g of methacrylic acid, 0.0g of butyl methacrylate, 361.2g of styrene, and 26g of PERBUTYL (registered trademark) were used. Otherwise, dispersion resin C with 45% non-volatile components, an acid value of 215, and a weight-average molecular weight of 8500 was obtained by the same method as in Example 1.

[0190] Furthermore, in the pigment dispersion preparation process, 13.2g of ion-exchanged water, 0.66g of TIPA (neutralization rate 150%), and 1.3g of dispersion resin C were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0191] [Example 7]

[0192] In the pigment dispersion preparation process, 13.5g of ion-exchanged water and 0.32g of MDEA (neutralization rate 150%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 6.

[0193] [Comparative Example 1]

[0194] In the pigment dispersion preparation process, 13.6g of ion-exchanged water and 0.17g of 35% potassium hydroxide aqueous solution (KOH) (neutralization rate 60%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0195] [Comparative Example 2]

[0196] In the pigment dispersion preparation process, 13.6g of ion-exchanged water and 0.22g of 35% KOH (neutralization rate 75%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0197] [Comparative Example 3]

[0198] In the pigment dispersion preparation process, 13.5g of ion-exchanged water and 0.27g of triethanolamine (TEA, boiling point 335°C) (neutralization rate 100%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0199] [Comparative Example 4]

[0200] In the pigment dispersion preparation process, 13.4g of ion-exchanged water and 0.40g of TEA (neutralization rate 150%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0201] [Comparative Example 5]

[0202] In the pigment dispersion preparation process, 13.5g of ion-exchanged water and 0.35g of TIPA (neutralization rate 100%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 3.

[0203] [Comparative Example 6]

[0204] In the pigment dispersion preparation process, 13.5g of ion-exchanged water and 0.28g of 35% KOH (neutralization rate 75%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 6.

[0205] [Comparative Example 7]

[0206] In the pigment dispersion preparation process, 13.7g of ion-exchanged water and 0.11g of 28% ammonia solution (neutralization rate 80%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 6.

[0207] [Comparative Example 8]

[0208] In the pigment dispersion preparation process, 13.6g of ion-exchanged water and 0.20g of dimethylethanolamine (DMEA, boiling point 133°C) (neutralization rate 100%) were used. Otherwise, the pigment dispersion and water-based inkjet ink were obtained by the same method as in Example 6.

[0209] [Comparative Example 9]

[0210] In the pigment dispersion preparation process, 13.4g of ion-exchanged water and 0.37g of 35% KOH (neutralization rate 100%) were used. Otherwise, the pigment dispersion was obtained by the same method as in Example 6.

[0211] 0.43 g (50% equivalent) of polyglycerol polyglycidyl ether (manufactured by Nagase Kasei, epoxy equivalent 183) was added to the obtained dispersion, and the mixture was stirred at 70°C for 3 hours to perform resin crosslinking treatment. Further, the mixture was filtered using a membrane filter with an 8 μm pore size (manufactured by Merck Millipore, nitrocellulose).

[0212] In addition, pigment dispersions and water-based inkjet inks were obtained by the same method as in Example 6.

[0213] [Comparative Example 10]

[0214] In the pigment dispersion manufacturing process, 13.4 g of ion-exchanged water and 0.44 g of TIPA (neutralization rate 100%) were used. Otherwise, crosslinking treatment was performed in the same manner as in Comparative Example 9 to obtain the pigment dispersion and inkjet ink.

[0215] [Comparative Example 11]

[0216] In the pigment dispersion manufacturing process, 13.5g of ion-exchanged water and 0.34g of TEA (neutralization rate 100%) were used. Otherwise, crosslinking treatment was performed in the same manner as in Comparative Example 9 to obtain the pigment dispersion and inkjet ink.

[0217] <Evaluation of the production of printed materials>

[0218] The ink composition is filled into the ink cartridge of an inkjet printer (manufactured by Seiko Epson Corporation, MJ-510C). Solid patterns are printed on corona-treated polypropylene (OPP) biaxial stretch film ("PYLEN P2161" manufactured by Toyobo Co., Ltd., 20μm thick), corona-treated (PVC) film ("LSPVC1270" manufactured by SAKURAI Co., Ltd., 140μm), or corona-treated polyethylene terephthalate (PET) film ("Ester E5100" manufactured by Toyobo Co., Ltd., 12μm thick). After drying in a dryer, the print is further dried in a 90°C oven for 10 minutes to obtain the printed material.

[0219] <Odor Test>

[0220] Sensory evaluation was conducted on the amine odor in an oven during the drying of pigment dispersions at room temperature and printed materials for evaluation at 90°C, according to the 6-level odor rating system in the Odor Prevention Law. A grade indicates compliance.

[0221] A: Level 0-1 (Odorless to barely detectable odor)

[0222] B: Level 2-5 (indicates the type of odor, from faint to strong)

[0223] <Filtering>

[0224] The pigment dispersion with a pigment concentration adjusted to 15% was filtered using an 8 μm pore size membrane filter (Merck Millipore, nitrocellulose). Filterability was evaluated according to the following criteria. Crosslinked samples were judged based on their filterability after crosslinking treatment. A was considered acceptable.

[0225] A: Filtration rate is above 150g / min

[0226] B: Filtration rate is 50g / min~150g / min

[0227] C: The filtration rate is below 50g / min, or the filter is clogged before 26g of liquid passes through.

[0228] <Abrasion Resistance>

[0229] In accordance with JIS K5701-1:2000, the rubbing fastness of the printed matter printed on OPP film, PVC film, or PET film was evaluated using a Gakushin-type friction fastness tester (manufactured by TESTER SANGYO Co., Ltd., AB-301). The printed matter was set on the tester. For the dry rubbing test, PPC paper was used as the rubbing paper, and the test was conducted under the conditions of a load of 200 g and 100 round trips. For the wet rubbing test, No. 3 fine white cloth wetted with ion-exchanged water was used as the rubbing paper, and the test was conducted under the conditions of a load of 200 g and 10 round trips. Regarding the ink peeling situation of the printed matter after the test, it was evaluated visually according to the following evaluation criteria. Grade B or above is considered qualified.

[0230] A: No peeling occurred at all.

[0231] B: Less than 1% peeling occurred.

[0232] C: Peeling of 1% or more and less than 5% occurred.

[0233] D: Peeling of 5% or more and less than 10% occurred.

[0234] <Redissolution evaluation>

[0235] 30 μL of the aqueous inkjet ink for plastic substrates with the pigment concentration adjusted for each example was coated on a glass slide and placed in a dryer at 80 °C for 10 minutes to prepare a test plate. Then, it was immersed in water at room temperature for 60 seconds, and it was visually confirmed whether it redissolved. Grade B or above is considered qualified.

[0236] A: After being immersed for 30 seconds and taken out, no coloring components were confirmed on the glass slide, and no granular undissolved components were confirmed in the immersion solution.

[0237] B: A little dissolution residue could be confirmed on the glass slide or in the immersion solution, but it was within the allowable range.

[0238] C: Undissolved substances were clearly present on the glass slide or in the immersion solution

[0239] D: Undissolved substances were significantly present on the glass slide or in the immersion solution

[0240] It should be noted that the printing dyes evaluated as qualified or above in this experiment showed redissolution in the screen recording method or could be easily discharged by the cleaning operation after a long pause in printing in the inkjet recording method.

[0241] [Table 1]

[0242]

[0243] [Table 2]

[0244]

[0245] [Table 3]

[0246]

[0247] [Table 4]

[0248]

[0249] Based on the above results, it can be clearly confirmed that the inkjet inks of Examples 1-7 using the pigment dispersions of Examples 1-7 of the present invention do not produce odor during manufacturing, and have excellent abrasion resistance, filterability and resolubility.

[0250] On the other hand, the inkjet inks of Comparative Examples 1 to 11, which use the comparative dispersions of Comparative Examples 1 to 11, have all of the above-mentioned characteristics worse.

[0251] Therefore, it can be confirmed that the inkjet pigment dispersion and ink of the present invention are suitable for inkjet printing. Furthermore, it can be confirmed that the pigment dispersion and ink of the present invention have high abrasion resistance when printing on plastic substrates, making them suitable for printing on plastic films used for packaging, labeling, and other applications, and also applicable to surface printing.

Claims

1. A pigment dispersion for inkjet printing, characterized in that: It contains dispersant (A), pigment (B), and water (C). The dispersant (A) contains a non-crosslinked resin (A1), which has at least one structural unit (a1) derived from an acid-containing monomer. In the resin (A1), the neutralization rate when neutralizing acid groups at theoretical equivalents is set to 100%, and tert-alkanolamines are used to neutralize the acid groups in the structural unit (a1) at a neutralization rate exceeding 100% but less than 200%. The tertiary alkyl alcoholamine has 2-3 hydroxyl groups in its structure and a boiling point of 150-330℃. The resin (A1) has a mass-average molecular weight of 5,000 to 50,000. The acid value of the resin (A1) is 80~225 mgKOH / g.

2. The pigment dispersion for inkjet printing according to claim 1, wherein, The acid value of the resin (A1) is above 100 mg KOH / g and less than 200 mg KOH / g.

3. The pigment dispersion for inkjet printing according to claim 1 or 2, wherein, The dispersant (A) is styrene-methacrylic acid.

4. The pigment dispersion for inkjet printing according to claim 1 or 2, wherein, The tertiary alkyl alcoholamine is methyl diethanolamine or triisopropanolamine.

5. The pigment dispersion for inkjet printing according to claim 1 or 2, wherein, The content of pigment (B) in the total amount of the inkjet pigment dispersion is 10 to 30% by mass.

6. The inkjet pigment dispersion according to claim 1 or 2, further comprising a binder (D).

7. The inkjet pigment dispersion according to claim 1 or 2, used for printing on plastic substrates.

8. An inkjet ink that uses the inkjet pigment dispersion according to any one of claims 1 to 7.

9. A printed matter, printed using the inkjet ink of claim 8.

Images