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

Abstract

The purpose of the present invention is to provide an inkjet ink which has good friction resistance and alcohol resistance when printed on various substrates such as plastic substrates, and which does not produce odor during production or the like. Specifically, the present invention relates to a pigment dispersion for ink jet, which is characterized by containing a dispersant (A), a pigment (B), a binder (C) and water (D), the dispersant (A) containing at least a non-crosslinked resin (A1) having a constituent unit (a1) derived from an acid group-containing monomer, and in the resin (A1), the neutralization rate when an acid group is neutralized at a theoretical equivalent is 100%. The acid group in the constituent unit (a1) is neutralized using an alkanolamine having 1-3 hydroxyl groups in the structure at a neutralization rate of 80% to 200% (inclusive).

Description

Technical Field

[0001] The present invention relates to a pigment dispersion for use in aqueous inkjet ink, an aqueous inkjet ink prepared using the pigment dispersion, and a printed matter obtained by inkjet printing using the inkjet ink. Background Art

[0002] In addition to the view of sustainable development against the backdrop of the global expansion of air pollution caused by VOCs and global warming, there is a trend towards converting to petroleum resources due to concerns about labor safety and health and flammability and explosiveness, and restrictions on the use of organic solvents are becoming increasingly stringent. Therefore, in the printing ink industry, water-based inks are being developed by replacing 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 for inkjet inks.

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

[0004] In the past, in the printing of film substrates, solvent-based flexographic inks and solvent-based gravure inks were the mainstream. However, these printing methods have the problem of increased cost and time required for printing due to the need for platemaking. Therefore, in film packaging printing, the requirement for inkjet printing that does not require platemaking and can be printed on demand has increased. In addition, the requirement for on-demand printing of film substrates other than packaging applications, such as film printing in label display applications for indoor and outdoor use, has also increased.

[0005] However, water-based inkjet ink has the problem that friction resistance is not enough compared to solvent-based inkjet ink. In the printing to film substrate, although the back printing of printing on the back side of film substrate is mainstream, the speed of printing and processing is faster when the front printing of printing on the front side of film substrate is printed, and when the situation of attaching importance to productivity and cost, front printing is more favorable. However, due to the fact that in front printing, the printed surface is not in contact with the external environment across the substrate, the higher friction resistance of the printed surface and ink itself is required. If it is an inkjet ink having friction resistance concurrently, it can not only be used for the back printing of film, but also can be used for front printing, and versatility is improved, so it is desired that a kind of inkjet ink with excellent friction resistance is used.

[0006] On the other hand, attempts have been made to improve the friction resistance of aqueous inkjet inks, but as a result, aggregates are generated, which may reduce filterability and ink discharge. The reliability of ink discharge, which is a problem unique to inkjet printing, is caused by the following situation: during the time when ink is not discharged (open time) during inkjet printing, the ink discharged from the inkjet head dries up, resulting in nozzle clogging. For inkjet inks, it is desirable to have excellent ink resolubility that can reduce the occurrence of nozzle clogging.

[0007] In addition, recently, alcohol disinfectants are sometimes used for disinfection to prevent contact infection of bacteria and viruses through fingers and objects. Since consumers are expected to touch the package with their fingers covered with alcohol disinfectants or to disinfect the surface of the package itself with alcohol disinfectants, inkjet inks used for printing on the front of the package are also required to have high alcohol resistance.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2019-196423 Summary of the invention

[0011] Problems to be solved by the invention

[0012] Patent Document 1 discloses an inkjet ink having excellent water resistance and alcohol resistance and capable of film printing, characterized in that the acid value of the dispersant of the ink is neutralized with ammonia, and the resin emulsion has 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 known that a certain degree of friction resistance can be obtained by the structure of Patent Document 1. However, Patent Document 1 is related to the friction resistance that is expected to be further improved, and the friction resistance when dry is not evaluated.

[0013] In addition, since ammonia is used for neutralization in the invention described in Patent Document 1, there are problems caused by odor generated during production and residual odor in the composition itself. Furthermore, since ammonia is highly volatile, there is also a problem of nozzle clogging due to volatilization of ammonia used for neutralization. Furthermore, it is also desired to further improve the alcohol resistance.

[0014] 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 does not generate odor during manufacturing; an inkjet pigment dispersion that can be used for the inkjet ink; and a printed matter that is inkjet printed using the inkjet ink.

[0015] Solution to the problem

[0016] The present inventors have conducted intensive studies to solve this problem and have found that the problem can be solved by neutralizing part or all of the acid groups in the dispersant resin with an alkanolamine and using a non-crosslinked resin as a pigment dispersion dispersant, thereby completing the present invention.

[0017] That is, the present invention relates to the following inventions.

[0018] (1) A pigment dispersion for inkjet, comprising a dispersant (A), a pigment (B), a binder (C) and water (D),

[0019] The dispersant (A) contains at least a non-crosslinked resin (A1) having a structural unit (a1) derived from an acid group-containing monomer.

[0020] In the resin (A1), the acid groups in the structural unit (a1) are neutralized with an alkanolamine at a neutralization rate of 80% to 200%, assuming that the neutralization rate when the acid groups are neutralized in theoretical equivalent is 100%.

[0021] The above alkanolamine has 1 to 3 hydroxyl groups in its structure.

[0022] (2) The inkjet pigment dispersion according to (1), wherein the acid value of the resin (A1) is 80 to 225 mgKOH / g.

[0023] (3) The inkjet pigment dispersion according to (1) or (2), wherein the binder (C) is an acrylic binder or a polyester binder.

[0024] (4) The pigment dispersion for inkjet according to any one of (1) to (3), which is used for printing on a plastic substrate.

[0025] (5) An inkjet ink using the pigment dispersion for inkjet according to any one of (1) to (4).

[0026] (6) A printed matter obtained by printing with the inkjet ink of (5).

[0027] Effects of the Invention

[0028] According to the present invention, it is possible to obtain an aqueous inkjet ink which has excellent friction properties and alcohol resistance even when used on a plastic substrate or the like and which does not generate odor during production or the like. DETAILED DESCRIPTION

[0029] [Pigment dispersion for inkjet]

[0030] The "pigment dispersion for inkjet" of the present invention (hereinafter, sometimes simply referred to as "pigment dispersion" or "dispersion") contains a dispersant (A), a pigment (B), a binder (C) and water (D), and is used to prepare an inkjet ink. Hereinafter, the "dispersant (A)" may be referred to as "component (A)", and other components may be referred to similarly.

[0031] The pigment dispersion of the present invention is produced as an intermediate product for inkjet ink and is used for inkjet printing in the form of aqueous inkjet ink after dilution.

[0032] <Dispersant (A)>

[0033] The dispersant (A) contains a non-crosslinked resin (A1), wherein the resin (A1) has at least a structural unit (a1) derived from an acid group-containing monomer. In the dispersant (A), the acid group in the structural unit (a1) is neutralized with a tertiary alkanolamine.

[0034] (Resin (A1))

[0035] The resin (A1) is a non-crosslinked resin having a constituent unit (a1) derived from an acid group-containing monomer and a constituent unit (a2) other than (a1), and can be obtained by polymerizing the acid group-containing monomer with monomers other than the acid group-containing monomer using a known method such as free radical polymerization in the presence of any polymerization initiator. The resin (A1) has an acid group, and hydrophilicity is imparted to the resin (A1), so that the pigment can be stably dispersed in water.

[0036] Examples of the acid group-containing monomer from which the structural unit (a1) is derived include a carboxyl group, a sulfonic acid group, a phosphoric acid group, and a thiocarboxyl group. Ethylenically unsaturated monomers having these groups can be used as raw material monomers for the structural unit (a1).

[0037] Examples of the carboxyl group-containing ethylenically unsaturated monomer 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.

[0038] Examples of sulfonic acid group-containing ethylenic unsaturated monomers include: unsaturated carboxylic acid sulfo-substituted alkyl or aryl esters such as 2-sulfoethyl acrylate and 4-sulfophenyl methacrylate; sulfocarboxylic acid unsaturated esters such as vinyl sulfosuccinate; and sulfostyrenes such as styrene-4-sulfonic acid.

[0039] Among them, the monomer from which the structural unit (a1) is derived is preferably a monomer having a carboxyl group as an acid group, more preferably an unsaturated carboxylic acid, and preferably acrylic acid or methacrylic acid, in view of the availability and price of the raw material monomer.

[0040] Hereinafter, both acrylic acid and methacrylic acid may be collectively referred to as “(meth)acrylic acid”, and both acrylate and methacrylate may be collectively referred to as “(meth)acrylate”. The same applies to similar acrylic compounds.

[0041] As the constituent unit (a2) other than the constituent unit (a1), there may be mentioned ethylenically unsaturated monomers copolymerizable with (a1), for example: (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 esters such as vinyl acetate and vinyl propionate; styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene Styrenes such as ethylene, propylene, 1-butene, 1-octene, vinylcyclohexane, 4-vinylcyclohexene, etc.; unsaturated hydrocarbons such as ethylene, propylene, 1-butene, 1-octene, vinylcyclohexane, 4-vinylcyclohexene, etc.; unsaturated halogenated hydrocarbons such as vinyl chloride, vinylidene chloride, tetrafluoroethylene, 3-chloropropylene, etc.; vinyl-substituted heterocyclic compounds such as 4-vinylpyridine, N-vinylcarbazole, N-vinylpyrrolidone, etc.; reaction products of monomers containing substituents having active hydrogen such as carboxyl, hydroxyl, and amine groups among the above-mentioned exemplified monomers with epoxides such as ethylene oxide, propylene oxide, and cyclohexene oxide; reaction products of monomers containing substituents such as hydroxyl and amine groups among the above-mentioned exemplified monomers with carboxylic acids such as acetic acid, propionic acid, butyric acid, hexanoic acid, decanoic acid, and dodecanoic acid, etc.

[0042] Among them, the monomer from which the structural unit (a2) is derived is preferably (meth)acrylates or styrenes, and preferably butyl (meth)acrylate, styrene or α-methylstyrene, in order to obtain an effect of improving the adsorption capacity of the resin (A1) to the pigment.

[0043] As the structural unit (a2), it is also preferred to contain methoxypolyethylene glycol monomethacrylate as a monomer in terms of having an excellent effect of further improving the discharge property.

[0044] Examples of the polymerization initiator include organic peroxides and azo compounds.

[0045] Examples of the organic peroxide include di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, cumene hydroperoxide, isobutyl peroxide, dodecanoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, tert-butyl peroxyisobutyrate, benzoyl peroxide, and methyl ethyl ketone peroxide.

[0046] Examples of the azo compound 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).

[0047] The polymerization initiator may be used alone or in combination of two or more.

[0048] Resin (A1) is a non-crosslinked resin. In the present invention, resin (A1) is non-crosslinked, which means that the resin (A1) is synthesized and manufactured without intentionally using a compound generally regarded as a crosslinking agent, or the resin (A1) is synthesized and manufactured without a commonly used crosslinking process. The crosslinking rate of the resin (A1) manufactured without the addition of a crosslinking agent or an intentional crosslinking process is 5% or less, preferably 3% or less, and most preferably 0%. The non-crosslinked resin (A1) is basically a straight-chain resin. The above crosslinking rate is a theoretical value, which is set to 100% when the crosslinking amount is 1 molar equivalent, and is set to 50% when it is 0.5 molar equivalent.

[0049] In the present invention, since the abrasion resistance is improved by the alkanolamine described later, it is not necessary to ensure the abrasion resistance by crosslinking the resin (A1). Moreover, since the resin (A1) is non-crosslinked, the re-solubility of the dispersion and the ink becomes good, and excellent ink discharge properties are obtained, and as a result, the undesirable conditions such as nozzle clogging can be suppressed. In addition, by not going through the crosslinking step during the production of the resin (A1), it is expected that the production process can be shortened and the energy consumption can be reduced.

[0050] The mass average molecular weight of the resin (A1) is preferably in the range of 2,000 to 100,000, particularly preferably in the range of 5,000 to 50,000, in order to easily make the pigment dispersion have an appropriate viscosity, to provide good dispersion stability, and to ensure long-term stable printing when made into an inkjet ink.

[0051] 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 preferably less than 170 mgKOH / g.

[0052] By setting it as the said range, the balance between the hydrophilicity of a dispersant and a pigment adsorption property can be maintained, and the dispersion stability of a pigment dispersion can be improved.

[0053] In the present invention, by making the resin (A1) non-crosslinked, good re-dissolution properties can be obtained even when the acid value of the resin (A1) is low (eg, less than 200 mgKOH / g).

[0054] The glass transition point of the resin (A1) is preferably 30 to 130°C, more preferably 50 to 120°C, particularly preferably 80 to 110°C.

[0055] In the dispersant (A), part or all of the acid groups in the structural unit (a1) are neutralized with an alkanolamine having 1 to 3 hydroxyl groups in the structure (hereinafter, sometimes simply referred to as "alkanolamine").

[0056] As the alkanolamine, preferably, one or two of the three hydrogen atoms of ammonia (NH3) are replaced by an "organic group having a hydroxyl group", and the remaining one or two are replaced by an organic group; or a compound in which all three hydrogen atoms are replaced by an "organic group having a hydroxyl group". As the organic group replacing the hydrogen atom, an alkyl group having 1 to 3 carbon atoms is preferably used, and as the "organic group having a hydroxyl group" replacing the hydrogen atom, a group in which a hydroxyl group is bonded to an alkyl group having 1 to 3 carbon atoms is preferably used.

[0057] As the alkanolamine, a compound represented by the following formula (I) is preferred.

[0058]

[0059] (In formula (I), R 1 ~R 3 are each independently an organic group which may have a hydroxyl group, R 1 ~R 3 At least one of them is an organic group having a hydroxyl group)

[0060] The organic group is preferably a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms.

[0061] The number of hydroxyl groups substituted with the alkyl group is preferably 2 or more, more preferably 1 to 3, and preferably 1.

[0062] The boiling point of the alkanolamine is preferably 100 to 330°C, preferably 110 to 330°C, more preferably 120 to 320°C, and further preferably 130 to 310°C.

[0063] By using an alkanolamine having a boiling point of 330°C or less for neutralization, the alkanolamine volatilizes well when the printed matter dries, and does not generate odor like ammonia. In addition, if the alkanolamine has a boiling point of 100°C or more, it is not easy to volatilize in the inkjet nozzle, so the nozzle is not easily clogged and the discharge performance is not reduced.

[0064] Examples of the alkanolamines 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.

[0065] Among these, tertiary alkanolamines having a carbon number of 2 or more and 9 or less are preferred, and methyldiethanolamine or triisopropanolamine is particularly preferred.

[0066] The method of neutralization with the alkanolamine is not particularly limited, and for example, neutralization can be performed by adding the alkanolamine and, if necessary, water to the resin (A1) in the organic solvent obtained by the synthesis of the monomers.

[0067] Neutralization can be performed using alkanolamine alone or in combination with other neutralizing agents. Examples of other neutralizing agents include metal salts.

[0068] Examples of the metal salt 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.

[0069] When the alkanolamine and the metal salt are used together, when the neutralization rate is 150% as described below, the ratio is preferably alkanolamine:metal salt=60-120%:30-90%, and the total neutralization rate is 150%. When the neutralization rate is not 150%, the alkanolamine and the metal salt are preferably used in the same ratio.

[0070] By using a metal salt in combination, a balance between abrasion resistance and solubility can be maintained. However, when a metal salt is used, there are problems such as unsuitability for printing for food packaging applications. Therefore, it is preferable to consider the use in combination.

[0071] Regarding neutralization, only a part of the acid groups may be neutralized, or all of the acid groups may be neutralized, and preferably all of the acid groups are neutralized.

[0072] Specifically, the neutralization rate when the acid groups of the resin (A1) are neutralized in theoretical equivalent is 100%, and the neutralization rate is 80% to 200%, preferably 100 to 200%. By setting such a neutralization rate, the solubility and filterability of the resin (A1) are improved.

[0073] The dispersant (A) may consist of the resin (A1) alone, or may contain other components in addition to the resin (A1).

[0074] In the pigment dispersion of the present invention, the dispersant (A) preferably contains 5 to 100% by mass, more preferably 10 to 80% by mass, relative to the pigment in terms of non-volatile components. Within these ranges, the reduction in dispersion stability of the pigment dispersion caused by excessive or insufficient dispersant can be suppressed, and a stable state can be maintained even during long-term storage.

[0075] <Pigment (B)>

[0076] The pigment (B) is not particularly limited as long as it can be well dispersed in the dispersion, and preferably a pigment that can be dispersed with an average particle size of 10 to 400 nm is used (details will be described later). For example, organic pigments, inorganic pigments, and dyes used in general inks, coatings, and recording agents can be used.

[0077] Examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene pigments, pyrenone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinoline yellow pigments, azomethine azo pigments, diketopyrrolopyrrole pigments, and isoindolinone pigments. For blue inks, copper phthalocyanine is preferably used in terms of cost and light resistance.

[0078] Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron, mica, etc. In addition, a bright pigment (METASHINE; Nippon Sheet Glass Co., Ltd.) obtained by coating a metal or metal oxide on a base material made of glass flakes or block flakes can be used. In terms of cost and coloring power, it is preferred to use titanium oxide for white ink, carbon black for black ink, aluminum for gold and silver inks, and mica for pearlescent inks.

[0079] As described above, in the dispersion, the pigment is preferably dispersed with a volume average particle size of 10 to 400 nm. The average particle size of the pigment can be measured by a known method such as a dynamic light scattering method after the dispersion is prepared, in a state where the pigment is uniformly dispersed in the dispersion. Among them, the volume average particle size of the dispersion is preferably 10 to 300 nm, more preferably 50 to 200 nm, and further preferably 50 to 150 nm, and particularly preferably 50 nm or more and less than 100 nm. By having a volume average particle size of 50 nm or more, the aggregation of the pigment during the storage of the pigment dispersion can be suppressed. In addition, the ink discharge property is improved by having a volume average particle size of 400 nm or less (particularly preferably less than 100 nm).

[0080] The content of the pigment in the dispersion is not particularly limited, and is preferably 10 to 30% by mass of the total amount of the dispersion. If it is less than 10% by mass, there is a concern that the inkjet ink obtained by diluting the dispersion to prepare the dispersion may not be able to obtain sufficient ink coloring power. In addition, if it is more than 30% by mass, depending on the type of pigment, there is a concern that the pigment will aggregate during the transportation and storage of the dispersion, and in this case, the dispersibility at an average particle size of 50 to 400 nm cannot be ensured. In addition, depending on the degree of dilution, there is a concern that the ink discharge property may deteriorate.

[0081] In the dispersion of the present invention, the pigment concentration is preferably 10 to 30% by mass, more preferably 10 to 25% by mass, when the pigment is an organic pigment or carbon black. Within these ranges, when diluted and adjusted to form an inkjet ink, both the ink coloring power and the ink discharge properties can be appropriately taken into account.

[0082] Moreover, when the pigment is an inorganic pigment, it is preferably 25 to 60% by mass, and more preferably 30 to 50% by mass.

[0083] <Adhesive (C)>

[0084] By using the binder (C) in the dispersion of the present invention, the substrate adhesion and abrasion resistance of the ink can be further improved. On the other hand, if the binder (C) has a pigment dispersing ability, the binder (C) may cause the dispersant (A) to separate from the pigment, thereby reducing the dispersion stability of the pigment dispersion. Therefore, the binder (C) preferably does not have a pigment dispersing ability.

[0085] Preferred pressure-sensitive adhesives include acrylic pressure-sensitive adhesives (C1) and polyester pressure-sensitive adhesives (C2).

[0086] (Acrylic adhesive (C1))

[0087] The acrylic adhesive (C1) is not particularly limited as long as it contains an acrylic resin, and an acrylic resin or an acrylic emulsion obtained by dispersing an acrylic resin in a solvent may be used. Among them, an aqueous acrylic emulsion is preferred in terms of excellent dispersibility in a pigment dispersion. By using an acrylic adhesive (C1), the adhesion of an inkjet ink using the dispersion of the present invention to an olefin substrate such as (biaxially) stretched polypropylene (OPP) can be improved.

[0088] Examples of acrylic emulsions include acrylic emulsions, styrene acrylic emulsions, acrylic maleic acid emulsions, and styrene acrylic maleic acid emulsions. Preferred acrylic emulsions include acrylic emulsions and styrene acrylic emulsions. The emulsion may be a core-shell type or an emulsion other than a core-shell type.

[0089] Examples of the structural unit in the emulsion resin include the structural units (a1) and (a2) described above, and structural units copolymerizable with these.

[0090] The present inventors have found through previous studies that the higher the Tg of the acrylic adhesive (C1), the better the dry friction resistance is. On the other hand, if the Tg of the acrylic adhesive (C1) is low, the dry friction resistance may be reduced.

[0091] The acid value of the acrylic adhesive (C1) is preferably 5 to 100 mgKOH / g, more preferably 5 to 80 mgKOH / g, and further preferably 20 to 50 mgKOH / g. If the acid value is less than 5 mgKOH / g, the dispersion stability of the acrylic adhesive (C1) may be reduced. On the other hand, if the acid value is greater than 100 mgKOH / g, the hygroscopicity of the printed coating may be increased, thereby impairing the wet friction resistance in the friction resistance.

[0092] The glass transition point of the acrylic pressure-sensitive adhesive (C1) is preferably 0 to 100°C, more preferably 0 to 80°C, further preferably 0 to 70°C, particularly preferably 10 to 40°C.

[0093] By setting it as the said range, the drying time after printing can be shortened, and it is preferable from the viewpoint of improving a printing speed and energy saving.

[0094] 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 placing a resin diluted with ion exchange water in a tank and using UPA-EX150 under the following conditions.

[0095] Load index: 5±1

[0096] ·Measurement time: 180 seconds

[0097] ·Number of measurements: 5 times

[0098] ·Permeability:

[0099] Particle refractive index: 1.80

[0100] Shape: spherical

[0101] Density: 1.00

[0102] Solvent refractive index: 1.333

[0103] Viscosity at high temperature: 30°C, 0.797

[0104] Low temperature viscosity: 20℃, 1.002

[0105] Filter: Stand: Norm

[0106] Sensitivity: Standard

[0107] UPA compatible mode

[0108] Of course, commercial products can be used as acrylic adhesives (C1). Commercial products include "ME-2039", "XJE-509", "XJE-518", "XJE-520", "XJE-556", "XJE-600" (manufactured by Starlight PMC, acrylic emulsions); "Joncryl 631", "Joncryl 731" (manufactured by BASF), etc.

[0109] (Polyester-based adhesive (C2))

[0110] The polyester binder (C2) may be a general polyester resin obtained by dehydration condensation of a polyol with a polycarboxylic acid, a polycarboxylic anhydride or a polycarboxylic ester. By using a polyester binder, the adhesion of the inkjet ink using the dispersion of the present invention to a substrate having a polar group such as polyethylene terephthalate (PET) can be improved.

[0111] Examples of the polyol used for producing the polyester resin 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; cyclic diols such as 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, and bisphenol S, and alkylene oxide adducts thereof.

[0112] The polycarboxylic acid used for producing the polyester resin is preferably a dicarboxylic acid, and specific examples thereof include succinic acid, adipic acid, sebacic acid, dodecenylsuccinic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, phthalic acid, isophthalic acid, terephthalic acid or derivatives thereof, and naphthalene dicarboxylic acid.

[0113] By using one or more of the above-mentioned polyols and one or more of the above-mentioned polycarboxylic acids, a polyester resin can be obtained.

[0114] The number average molecular weight of the polyester resin is preferably 1,000 to 50,000, more preferably 3,000 to 20,000.

[0115] As the polyester resin, a commercially available product can be used. Examples of the commercially available product 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), "Elitel KZA-6034" (number average molecular weight: 6500), "Elitel KT-8803" (number average molecular weight: 15000), "Elitel KT-8701" (number average molecular weight: 13000), "Elitel KT-9204" (number average molecular weight: 17000), "Elitel KT-8904" (number average molecular weight: 17,000), "Elitel KT-0507" (number average molecular weight: 17,000), "Elitel KT-9511" (number average molecular weight: 17,000) (all manufactured by Unitika), etc. These may be used alone or in combination of two or more.

[0116] The adhesive (C) may contain other components instead of the above-mentioned (C1) component and (C2) component, or may contain other components in addition to these components. As other components, polyurethane resins are preferred. Among them, polyether polyol polyurethane resins are preferably used in terms of being less prone to hydrolysis than polyester polyol polyurethanes and having particularly excellent friction resistance of colored images. As polyether polyol polyurethane resins, for example, polyurethane resins obtained by reacting polytetramethylene ether glycol (PTMG) with diisocyanates can be cited.

[0117] In the dispersion of the present invention, the binder (C) preferably contains 10 to 200 mass % in terms of non-volatile components, more preferably 30 to 150 mass %. If it is within these ranges, the adhesion, abrasion resistance and blocking resistance of the inkjet ink to the substrate can be achieved even after dilution, so it is preferred.

[0118] 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, more preferably 0.3 to 3.0% by mass.

[0119] <Other optional ingredients>

[0120] The pigment dispersion of the present invention may contain other optional components in addition to the above-mentioned (A) component, (B) component, (C) component and water (D) within a range not impairing the effects of the present invention.

[0121] 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, penetrants, dispersants other than the above, defoamers, preservatives, viscosity modifiers, pH modifiers, chelating agents, plasticizers, antioxidants, and ultraviolet absorbers.

[0122] (Amine compound (E) having a boiling point of 100° C. or higher)

[0123] 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 nozzle, resulting in improved discharge properties, and both discharge properties and abrasion resistance can be achieved.

[0124] Examples of the amine compound (E) include polyalkylene imine, polyallylamine, (poly)ethylene polyamine, alkanolamine, and alkylamine.

[0125] Among these, alkanolamines are preferred from the viewpoints of pigment dispersibility, odor, and resolubility.

[0126] (Polyalkyleneimine)

[0127] The polyalkylene imine is preferably a polyalkylene imine having an alkylene group having 2 or more and 5 or less carbon atoms.

[0128] The polyalkylene imine is preferably a polyalkylene imine having an alkylene group with a carbon number of 2 or more and 4 or less, more preferably polyethylene imine or polypropylene imine, and still more preferably polyethylene imine. These may be used alone or in combination of two or more.

[0129] The number average molecular weight of the polyalkyleneimine is preferably 150 or more, more preferably 500 or more, further preferably 800 or more, further preferably 1,000 or more, and is preferably 10,000 or less, more preferably 5,000 or less, further preferably 4,000 or less.

[0130] The value of the molecular weight is determined by the method described in Examples.

[0131] (Polyallylamine)

[0132] Examples of the polyallylamine include polymers having an amine group in a side chain, such as homopolymers or copolymers of allyl compounds such as allylamine and dimethylallylamine.

[0133] The weight average molecular weight of the polyallylamine is preferably 800 or more, more preferably 1,000 or more, and still more preferably 1,500 or more, and is preferably 10,000 or less, more preferably 5,000 or less, and still more preferably 4,000 or less.

[0134] (Polyethylene Polyamine)

[0135] Examples of (poly)ethylene polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc. Among these, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine are preferred.

[0136] (Alkanolamine)

[0137] The alkanolamine is preferably an alkanolamine having a carbon number of 2 or more and 9 or less. Examples of the alkanolamine 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 dialkanol secondary amines such as diethanolamine and diisopropanolamine; tertiary alkanolamines such as monoalkanol tertiary amines such as N,N-dimethylethanolamine, N,N-dimethylpropanolamine, and N,N-diethylethanolamine; tertiary dialkanol tertiary amines such as N-methyldiethanolamine and N-ethyldiethanolamine; and tertiary trialkanol tertiary amines such as triethanolamine and triisopropanolamine. Among these, tertiary alkanolamines having a carbon number of 2 or more and 9 or less are preferred, and triisopropanolamine is particularly preferred.

[0138] (Alkylamine)

[0139] 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.

[0140] In the pigment dispersion of the present invention, the neutralization rate of the amine compound (E) relative to the acid group of the dispersant (A) is preferably 30 to 500%, and particularly preferably 50 to 400%. Within these ranges, the ink is free from nozzle clogging and has excellent adhesion and abrasion resistance.

[0141] (Ingredients other than (A) to (E))

[0142] As other resins, aqueous resins suitable for preparing pigment dispersions may be used, and examples thereof include styrene-maleic acid copolymers and styrene-maleic anhydride copolymers.

[0143] Examples of the solvent 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; lactam solvents such as N-methyl-2-pyrrolidone, etc.

[0144] Examples of the surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants and nonionic surfactants are preferred.

[0145] Examples of the anionic surfactant include alkylbenzene sulfonates, alkylphenyl sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, sulfuric acid ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfuric acid ester salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and specific examples thereof include dodecylbenzene sulfonate, isopropylnaphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, and dibutylphenylphenol disulfonate.

[0146] Examples of the nonionic surfactant 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 amides, fatty acid hydroxyalkaneamides, alkylalkanolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, and alkylphenol ethoxylates. Among 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 hydroxyalkaneamides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, and alkylphenol ethoxylates are preferred.

[0147] As other surfactants, silicone-based surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as echinopsinic acid, rhamnolipid, and defatted lecithin can also be used.

[0148] These surfactants may be used alone or in combination of two or more. In consideration of the solubility stability of the surfactant, the HLB thereof is preferably in the range of 7 to 20.

[0149] Examples of commercially available fluorine-based 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 and Manufacturing Company); Monflor (manufactured by Imperial Chemical Industries); Licowet VPF series (manufactured by Farbwerke Hoechst).

[0150] Examples of the silicone-based surfactant include KF-351A, KF-642, Olfine PD-501, Olfine PD-502, and Olfine PD-570 (manufactured by Shin-Etsu Chemical Co., Ltd.); BYK347 and BYK348 (manufactured by BYK-Chemie Japan).

[0151] Examples of polyoxyethylene alkyl ether surfactants include BT series (Nikko Chemicals), NONIPOLE series (Sanyo Chemical), D-, P- series (Takemoto Oil & Fats), EMALEX DAPE series (Nihon Emulsion), and Pegnol series (Toho Chemical Industry). Examples of polyethylene glycol alkyl esters include Pegnol (Toho Chemical Industry).

[0152] Examples of the acetylene glycol-based surfactant 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.).

[0153] Examples of wax include plant / animal waxes such as carnauba wax, candelilla wax, beeswax, rice bran wax, and lanolin; mineral waxes such as montan wax and ozokerite; paraffin wax (so-called petroleum wax); synthetic waxes such as carbowax, Hoechst wax, polyolefin wax, silicone wax, and stearamide; natural / synthetic wax emulsions such as α-olefin-maleic anhydride copolymers; and compound waxes. These waxes have the effect of imparting slip and improving friction resistance to the surface of the recorded object formed. These waxes can be used alone or in combination. Among these, silicone wax, polyolefin wax, paraffin wax, etc. are preferably used.

[0154] Examples of commercially available silicone waxes include SM8706EX, SM7036EX, SM7060EX, SM7025EX, SM490EX, SM8701EX, SM8709SR, SM8716SR, IE-7045, IE-7046T, SH7024, BY22-744EX, BY22-818EX, FZ-4658, FZ-4634EX, and FZ-4602 (these are trade names, manufactured by Dow Corning Toray Co., Ltd.); POLON-MF-14, POLON-MF-14EC, and POLON-MF-23P OLON-MF-63, POLON-MF-18T, POLON-MF-56, POLON-MF-49, POLON-MF-33A, POLON-MF-55T, POLON-MF-28T, POLONMF-50, POLON-MK-206, POLON-SR-CONC, KM-9771, KM-9774, KM-2002-T, KM-2002-L-1, KM-9772, KS-7002, KS-701, X-51-1264 (these are trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

[0155] Examples of polyolefin waxes include waxes made from olefins such as ethylene, propylene, butene, and their derivatives, and copolymers thereof, specifically, polyethylene waxes, polypropylene waxes, polybutene waxes, etc. Polyolefin waxes may be used alone or in combination of two or more. Of these, polyethylene waxes are preferred from the viewpoint of being difficult to react with the crosslinking groups of the polyurethane resin particles having the crosslinking groups and having excellent discharge stability.

[0156] Examples of commercially available polyolefin waxes include AQUACER series such as AQUACER531 (polyethylene wax, average particle size of 100 nm to 200 nm, melting point of 130° C., solid content of 30%), AQUACER507, AQUACER515, AQUACER840, and AQUACER1547 (these are trade names, manufactured by BYK-Chemie Japan Co., Ltd.); Hightech series such as Hightech E-7025P, Hightech E-2213, Hightech E-6500, Hightech E-6314, Hightech E-9460, Hightech E-9015, Hightech E-4A, Hightech E-5403P, and Hightech E-8237 (these are trade names, manufactured by Toho Chemical Co., Ltd., polyethylene wax); Nopcote PEM-17 (trade name, San Nopco, polyethylene emulsion, average particle size 40 nm), ULTRALUBE E-843N (trade name, Keim Additec Surface GmbH, polyethylene wax), etc.

[0157] Paraffin wax is a so-called petroleum wax. Here, paraffin refers to an alkane with 20 or more carbon atoms, and paraffin refers to a mixture of hydrocarbons with a molecular weight of about 300 to 500, with a straight-chain paraffin hydrocarbon with 20 or more and 30 or less carbon atoms as the main component and a small amount of isoparaffin. When the ink contains paraffin wax, the recorded material is given slip and water repellency, thereby improving the abrasion resistance.

[0158] Examples of commercially available paraffin wax include AQUACER537 and AQUACER539 (these are trade names, manufactured by BYK-Chemie Japan Co., Ltd.).

[0159] The wax is preferably contained in the pigment dispersion in a particulate state, that is, in an emulsion state or a suspension state. This makes it easy to adjust the viscosity of the ink so that it is within an appropriate and correct range during discharge using an inkjet head, and it is easy to ensure discharge stability and intermittent discharge characteristics during recording.

[0160] 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. These may be used alone or as a mixture of two or more.

[0161] Specifically, 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 monotert-butyl ether, 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, and the like.

[0162] Glycol ethers, surfactants, etc. can be used as surface tension modifiers to adjust the surface tension of the ink. Specifically, they can be appropriately added so that the surface tension of the ink becomes 15mN / m to 30mN / m. The amount of surfactant added is preferably in the range of about 0.1 to 10% by mass, more preferably 0.3 to 2% by mass, relative to the aqueous pigment dispersion. The surface tension is more preferably in the range of 16 to 28mN / m, and most preferably in the range of 18 to 25mN / m.

[0163] The wetting agent is not particularly limited, but is preferably a wetting agent that is miscible with water and can prevent the nozzle of the inkjet printer from being clogged. Examples thereof include glycerol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol with a molecular weight of 2,000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methylpentane-2,4-diol, 1,2-heptanediol, 1,2-non ... 2-octanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-nonanediol, 1,2-octanediol and other diol compounds; 1,4-butanediol, 1,3-butanediol, mesoerythritol, pentaerythritol, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam and other nitrogen-containing heterocyclic compounds, etc. Among them, when propylene glycol and 1,3-butanediol are included, it is safe and has excellent effects on ink drying and discharge performance.

[0164] The content of the wetting agent in the ink is preferably 3 to 50% by mass.

[0165] Examples of the penetrant 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.

[0166] <Method for producing pigment dispersion>

[0167] The method for producing the pigment dispersion in the present invention is not limited at all.

[0168] The pigment dispersion can be prepared by dispersing any of the components (A) to (D) and the component (E) added as needed. Alternatively, a pigment dispersion grinding base liquid having a high pigment concentration can be prepared in advance by using the components (A), (B) and a part of the component (D), a medium, etc., and then the component (C) is appropriately added and diluted with an aqueous medium such as the component (D) to prepare a pigment dispersion for preparing an aqueous inkjet ink. The pigment dispersion can be prepared by dispersing the pigment in advance by using a stirring and dispersing device to prepare a pigment dispersion grinding base liquid, thereby easily obtaining an aqueous pigment dispersion in which the pigment is dispersed in a desired volume average particle size.

[0169] The following describes the latter method of preparing a pigment dispersion by preparing a pigment dispersion-grinding base liquid.

[0170] As a method for producing the pigment-dispersed mill base, the following method can be mentioned.

[0171] (1) A method of preparing a pigment-dispersed milling base by adding a pigment to an aqueous medium containing a pigment dispersant as necessary and then dispersing the pigment in the aqueous medium using a stirring and dispersing device.

[0172] (2) A method in which a pigment and a pigment dispersant, which is added as needed, are kneaded using a kneading machine such as a double roll mill or a mixer, the kneaded product is added to an aqueous medium, and a pigment dispersion base liquid is prepared using a stirring and dispersing device.

[0173] (3) A method of preparing a pigment dispersion grinding base liquid by dissolving a pigment dispersant in an organic solvent such as methyl ethyl ketone or tetrahydrofuran that is miscible with water to obtain a solution, adding a pigment to the obtained solution, dispersing the pigment in the organic solution using a stirring and dispersing device, and then performing phase inversion emulsification using an aqueous medium, and then distilling off the organic solvent.

[0174] Examples of the stirring and dispersing apparatus include an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roller mill, a sand mill, a sand grinder, a Dyno-mill, a high-speed disperser (Dispermat), an SC grinder, and a nanomizer. One of these may be used alone, or two or more of them may be used in combination.

[0175] <Inkjet ink>

[0176] The pigment dispersion of the present invention is used to dilute the pigment to a pigment content of 1 to 30% by mass using an aqueous medium to prepare an aqueous inkjet ink. The aqueous medium may be water, a mixture of water and an organic solvent, or only an organic solvent, as in component (D). The organic solvent is not particularly limited as long as it is an organic solvent miscible with water, and as the "solvent other than water", the above-mentioned solvents in any component may be cited.

[0177] In addition, the aqueous medium may contain any components of the pigment dispersion (for example, an antiseptic, a surface tension adjuster, etc.).

[0178] <Printed Materials>

[0179] The inkjet ink of the present invention has excellent adhesion to various substrates, especially to plastic substrates, and thus can be suitably used in the field of flexible packaging for food, daily necessities, pharmaceuticals, etc. having a plastic substrate and a printed layer based on the inkjet ink to produce printed materials.

[0180] Examples of the plastic substrate 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 poly(ethylene succinate) and poly(butylene succinate); polyolefin resins such as polypropylene and polyethylene; plastic substrates composed of thermoplastic resins such as polyvinyl chloride, polyimide resins, polyarylate resins, or mixtures thereof, and laminates thereof, among which substrates composed of polyester, polyamide, polyethylene, polypropylene, and polyvinyl chloride can be suitably used.

[0181] In addition, the plastic substrate may be a plastic film. The plastic film may be an unstretched film or a stretched film, and the method for making the plastic film is not limited. In addition, the thickness of the film is not particularly limited, and is usually in the range of 1 to 500 μm.

[0182] In addition, the printed surface of the film is preferably subjected to a corona discharge treatment. Alternatively, silicon dioxide, aluminum oxide, or the like may be vapor-deposited on the printed surface.

[0183] The printed matter of the present invention can be suitably used as a packaging material because it has good adhesion to a plastic substrate and can be produced by inkjet printing. In particular, it can be suitably used for food packaging because it has excellent design and on-demand printing properties. In addition, since the inkjet ink of the present invention has excellent friction resistance, the printed matter of the present invention can also be made into a front-side printed matter in which inkjet printing is performed on the front side.

[0184] Example

[0185] Hereinafter, the present invention will be specifically described by way of Examples and Comparative Examples. Hereinafter, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0186] (Examples 1 to 5, Comparative Examples 1 to 4)

[0187] [Example 1]

[0188] <Preparation of dispersion resin>

[0189] 600 g of methyl ethyl ketone (MEK) was added to a 2L stainless steel flask, and nitrogen was blown in at 20 mL / min. The mixture was stirred at 100 rpm and heated to 80°C using an oil bath. 84.5 g of methacrylic acid, 215.0 g of styrene, 200.0 g of butyl methacrylate, and 18.0 g of PERBUTYL (registered trademark) O (manufactured by NOF Corporation) which had been pre-mixed were added dropwise to the flask at 2 g / min. Thereafter, stirring was continued for 16 hours while the internal temperature was maintained at 80°C, and a dispersion resin A having a non-volatile content of 45%, an acid value of 110, and a mass average molecular weight of 20,000 was obtained.

[0190] <Preparation of Dispersed Resin Neutralization Solution>

[0191] In a 10L glass separable flask, 1284.58g of ion exchange water, 315.42g of methyldiethanolamine (MDEA, boiling point 247°C) (neutralization rate 150%), and 2000g of dispersion resin A were added and stirred. Thereafter, 3300g of ion exchange water was added, and the temperature was raised while stirring to distill off MEK and water, thereby obtaining a 150% neutralized solution of dispersion resin A containing 18.82% of resin component.

[0192] <Preparation of Pigment Dispersion>

[0193] In a 5L polymer material container, 474.58g of ion exchange water, 557.92g of MDEA 150% neutralized solution of dispersion resin A, 17.5g of Surfynol 465, 0.805g of BYK-019 as a defoamer, and 700g of phthalocyanine pigment (FASTOGEN BLUE SBG-SD manufactured by DIC Corporation) were added, and a slurry was obtained by stirring for 1 hour using a high-speed disperser. Thereafter, the slurry was put into an SC100 grinder (manufactured by NIPPON COKES Corporation), and 440g of φ0.5mm zirconium oxide beads (manufactured by NIKKATO Corporation, YTZ) were added to perform a dispersion treatment. After the dispersion treatment, the dispersion obtained by removing the beads was adjusted with ion exchange water so that the pigment component became 29%. Thereafter, coarse particles were removed by centrifugation (6000 G for 30 minutes), and the mixture was filtered using a membrane filter having a pore size of 8 μm (manufactured by Merck Millipore, nitrocellulose) to obtain a pigment dispersion.

[0194] <Inkjet ink production>

[0195] The prepared pigment dispersion is mixed with ingredients such as a water-soluble solvent to obtain an aqueous inkjet ink having a pigment concentration of 5%, an acrylic binder (acrylic emulsion manufactured by Starlight PMC, acid value 30°C, Tg 20°C) concentration of 1.5%, an oxidized polyethylene wax (manufactured by Keimadditec) concentration of 1.1%, a water-soluble solvent totaling 28% (propylene glycol 10%, 1,3-butanediol 5%, 1.2-hexanediol 3%, 2-pyrrolidone 10%), and a preservative / surface tension adjuster concentration of 0.1 to 1.0%.

[0196] [Example 2]

[0197] A pigment dispersion and an aqueous inkjet ink were obtained in the same manner as in Example 1 except that MDEA was replaced with dimethylethanolamine (DMEA, boiling point 133° C.) in an amount corresponding to a neutralization rate of 100% in the preparation step of the dispersion resin neutralization solution.

[0198] [Example 3]

[0199] Aqueous inkjet ink was obtained in the same manner as in Example 1 except that a polyester binder (Elitel KA-5071S manufactured by Unitika) was used instead of the acrylic binder in the preparation step of the inkjet ink.

[0200] [Example 4]

[0201] 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 acrylic binder in the preparation step of the inkjet ink.

[0202] [Example 5]

[0203] Aqueous inkjet ink was obtained in the same manner as in Example 2 except that a polyurethane binder (polyether polyol-based polyurethane resin, XPD3253 manufactured by Lubrizol Corporation) was used instead of the acrylic binder in the inkjet ink preparation step.

[0204] [Comparative Example 1]

[0205] Aqueous inkjet ink was obtained by the same method as in Example 1 except that no acrylic binder was used in the preparation step of the inkjet ink.

[0206] [Comparative Example 2]

[0207] Aqueous inkjet ink was obtained by the same method as in Example 2 except that no acrylic binder was used in the preparation step of the inkjet ink.

[0208] [Comparative Example 3]

[0209] A pigment dispersion and an aqueous inkjet ink were obtained in the same manner as in Example 3, except that potassium hydroxide in an amount corresponding to a neutralization rate of 100% was added instead of MDEA in the preparation step of the dispersion resin neutralization solution.

[0210] [Comparative Example 4]

[0211] A pigment dispersion and an aqueous inkjet ink were obtained in the same manner as in Example 1, except that in the step of preparing the dispersion resin neutralization solution, aqueous ammonia in an amount corresponding to a neutralization rate of 100% was added instead of MDEA.

[0212] <Production of printed materials for evaluation>

[0213] The inkjet ink of each example was filled in the ink cartridge of an inkjet printer (manufactured by Seiko Epson Corporation, MJ-510C), and a solid pattern was printed on a corona-treated polypropylene (OPP) biaxially stretched film ("PYLEN P2161" manufactured by Toyobo Co., Ltd., with a thickness of 20 μm), a corona-treated (PVC) film ("LSPVC1270f140 μm" manufactured by SAKURAI Co., Ltd.), or a corona-treated polyethylene terephthalate (PET) film ("ESTER E5100" manufactured by Toyobo Co., Ltd., with a thickness of 12 μm), and then dried in a dryer and then further placed in a 90°C oven for 10 minutes to obtain a printed material.

[0214] <Odor test>

[0215] The amine odor of the pigment dispersion at room temperature was sensory evaluated according to the following evaluation criteria.

[0216] ○: Almost odorless

[0217] ×: Strong smell

[0218] <Storage stability>

[0219] The viscosity of the inkjet ink of each example was measured and stored in a thermostatic chamber at 70° C. for 1 week. Thereafter, the viscosity was measured again and the storage stability was evaluated according to the following calculation formula and evaluation criteria. A value of B or higher was considered acceptable.

[0220] Storage stability = |1-(viscosity after storage) / (viscosity before storage)|×100 (formula)

[0221] A: 0 or more and less than 5

[0222] B: 5 or more and less than 10

[0223] C: 10 or more and less than 20

[0224] D: 20 or more

[0225] <Dry friction resistance>

[0226] According to JIS K5701-1:2000, the friction resistance of the printed matter printed on the PET film using the inkjet ink of each example was evaluated using a Gakushin type friction fastness tester (manufactured by TESTER SANGYO (Strain), AB-301). The printed matter was placed in the tester, and the dry friction test was conducted under the conditions of 200g load and 100 reciprocating strokes. The peeling of the ink in the printed matter after the test was visually evaluated according to the following evaluation criteria. B or above was considered acceptable.

[0227] A: No peeling occurred at all.

[0228] B: There was less than 1% peeling.

[0229] C: There is peeling of 1% or more and less than 5%.

[0230] D: There is peeling of 5% or more and less than 10%.

[0231] [Table 1]

[0232]

[0233] From the results, it can be seen that the inkjet inks of Examples 1 to 5 using the pigment dispersions of Examples 1 to 5 of the present invention do not generate odor during production and have excellent abrasion resistance. On the other hand, the inkjet inks of Comparative Examples 1 to 4 using the comparative pigment dispersions of Comparative Examples 1 to 4 are inferior in any of the above characteristics.

[0234] (Examples 6 to 7, Comparative Examples 5 to 6)

[0235] 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.

[0236] <Alcohol resistance>

[0237] According to JIS K5701-1:2000, the alcohol resistance of the printed matter printed on the PET film using the inkjet ink of each example was evaluated using a Gakushin type friction fastness tester (manufactured by TESTER SANGYO Co., Ltd., AB-301). The printed matter was placed in the tester, and a fine white cloth No. 3 moistened with 75% ethanol (EtOH) was used as the friction paper. The test was carried out under the conditions of a load of 200 g and 10 reciprocating strokes. The peeling of the ink in the printed matter after the test was visually evaluated according to the following evaluation criteria. B or above was considered acceptable.

[0238] A: There is less than 10% peeling.

[0239] B: There is 10% or more and less than 30% peeling.

[0240] C: There is 30% or more and less than 50% peeling.

[0241] D: 50% or more of the peeling occurred.

[0242] [Table 2]

[0243]

[0244] From these results, it was confirmed that the inkjet inks using the pigment dispersions of Examples 6 to 7 of the present invention were superior to the inkjet inks using the comparative pigment dispersions of Comparative Examples 5 to 6 in terms of alcohol resistance.

[0245] Therefore, it was confirmed that the inkjet pigment dispersion and inkjet ink of the present invention do not generate odor during production and can be suitably used in inkjet printing.

[0246] Furthermore, the pigment dispersion and inkjet ink of the present invention are excellent in abrasion resistance and alcohol resistance and are therefore suitable for printing on various substrates such as plastic films, and can be widely used for packaging, logo display, and the like, and can also be applied to front printing.

[0247] [Example 8]

[0248] <Preparation of dispersion resin>

[0249] 600 g of isopropyl alcohol was added to a 2 L stainless steel flask, and nitrogen was blown in at 20 mL / min. The mixture was stirred at 100 rpm and heated to 80°C using an oil bath. 82.7 g of methacrylic acid, 153.25 g of styrene, 88.65 g of butyl methacrylate, 73.44 g of 2-hydroxyethyl methacrylate, 88.65 g of butyl acrylate, 6.58 g of 2,2-azobis(2-methylbutyronitrile), 6.58 g of 4,4-azobisvaleric acid, and 0.33 g of 3-mercapto-1,2-propanediol (thioglycerol) were added dropwise to the flask at 2 g / min. Thereafter, stirring was continued for 16 hours while the internal temperature was maintained at 80°C to obtain a dispersion resin B having a non-volatile content of 45%, an acid value of 110, and a mass average molecular weight of 20,000.

[0250] <Preparation of Dispersed Resin Neutralization Solution>

[0251] Except that the dispersion resin A was changed to the dispersion resin B, the same method as the preparation of the dispersion resin neutralized solution in Example 1 was carried out to obtain an MDEA 150% neutralized solution of the dispersion resin B having a resin component of 18.82%.

[0252] <Preparation of Pigment Dispersion>

[0253] A pigment dispersion was obtained in the same manner as in the preparation of the pigment dispersion of Example 1, except that the MDEA 150% neutralized solution of the dispersion resin A was changed to the MDEA 150% neutralized solution of the dispersion resin B.

[0254] <Inkjet ink production>

[0255] Aqueous inkjet ink was obtained in the same manner as in Example 1 except that a polyester binder (Elitel KA-5071S manufactured by Unitika) was used instead of the acrylic binder in the preparation step of the inkjet ink.

[0256] [Example 9]

[0257] Aqueous inkjet ink was obtained by the same method as in Example 8 except that the concentration of the polyester binder was changed to 2.5% in the preparation step of the inkjet ink.

[0258] [Example 10]

[0259] Aqueous inkjet ink was obtained in the same manner as in Example 9 except that the polyester binder was changed to a polyester binder (Elitel KT-9511 manufactured by Unitika) in the preparation step of the inkjet ink.

[0260] [Example 11]

[0261] Aqueous inkjet ink was obtained by the same method as in Example 9 except that the polyester binder was changed to a polyester binder (Elitel KT-8803 manufactured by Unitika) in the preparation step of the inkjet ink.

[0262] [Example 12]

[0263] A pigment dispersion and an aqueous inkjet ink were obtained in the same manner as in Example 9 except that MDEA was replaced with dimethylethanolamine (DMEA, boiling point 133° C.) in the preparation step of the dispersion resin neutralization solution and added in an amount corresponding to a neutralization rate of 100%.

[0264] [Example 13]

[0265] Aqueous inkjet ink was obtained by the same method as in Example 12 except that the polyester binder was changed to a polyester binder (Elitel KT-8803 manufactured by Unitika) in the preparation step of the inkjet ink.

[0266] [Example 14]

[0267] A pigment dispersion and an aqueous inkjet ink were obtained in the same manner as in Example 9 except that MDEA was replaced with triisopropanolamine (TIPA, boiling point about 300° C.) in an amount corresponding to a neutralization rate of 150%.

[0268] [Table 3]

[0269]

[0270] From the results in Table 3, it was confirmed that the inkjet inks using the pigment dispersions of Examples 8 to 18 of the present invention did not generate odor during production and were excellent in abrasion resistance.

Claims

1. A pigment dispersion for inkjet, characterized in that: Contains dispersant (A), pigment (B), 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% to 200%, assuming that the neutralization rate when the acid groups are neutralized in theoretical equivalent is 100%. The alkanolamine has 1 to 3 hydroxyl groups in the structure.

2. The pigment dispersion for inkjet according to claim 1, wherein The acid value of the resin (A1) is 80 to 225 mgKOH / g.

3. The pigment dispersion for inkjet according to claim 1, wherein The adhesive (C) is an acrylic adhesive or a polyester adhesive. The pigment dispersion for inkjet according to claim 1 , which is used for printing on a plastic substrate. 5 . An inkjet ink using the pigment dispersion for inkjet according to claim 1 . 6 . A printed matter obtained by printing with the inkjet ink according to claim 5 .

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