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

Abstract

This invention relates to an inkjet pigment dispersion comprising a binder (A), a pigment (B), and an aqueous medium (C). The binder (A) is a polyurethane resin (A1) containing a polyol (a1) and a polyisocyanate (a2) as a reactant. The polyol (a1) comprises a polyol (a1-1) having acid groups and a polyester polyol (a1-2) other than the polyol (a1-1). The polyisocyanate (a2) comprises a polyisocyanate (a2-1) having a cyclic structure. Some or all of the acid groups in the polyurethane resin (A1) are neutralized. The glass transition temperature of the polyurethane resin (A1) is below 70°C.

Description

Technical Field

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

[0002] From a sustainability perspective, considering the worsening air pollution caused by VOCs and the expanding global warming, and driven by concerns about occupational safety and health, as well as flammability and explosiveness, there is a trend towards shifting away from petroleum resources, leading to increasingly stringent restrictions on the use of organic solvents. Therefore, in the printing ink industry, there is ongoing development of water-based inks that replace organic solvents in solvent-based printing inks with water. Similarly, in inkjet inks, there is a demand for the development and improvement of water-based inks.

[0003] On the other hand, due to population growth, rising income levels, and changes in the logistics system, the consumption of plastic film packaging is increasing worldwide, and the production of packaging inks is 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 drawbacks: increased costs due to the need for plate making, and time required to begin printing. Therefore, in film packaging printing, there is a growing demand for inkjet printing, which eliminates the need for plate making and allows for on-demand printing.

[0005] However, compared to solvent-based inkjet inks, water-based inkjet inks have the following issues: insufficient resistance to smudges and adhesion of the printed image, insufficient abrasion resistance, and insufficient lamination strength when adhesive is applied to the printed surface and the film is laminated. Furthermore, these issues are more pronounced when the substrate is a film substrate.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6295825 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] Patent Document 1 discloses an inkjet ink using polycarbonate-based polyurethane resin particles with a minimum film-forming temperature of 25°C or higher, which exhibits good drying properties and abrasion resistance on non-porous substrates. However, the invention described in Patent Document 1 did not conduct a lamination strength test, and it is desirable to further improve the lamination strength when developing it for packaging applications.

[0011] The problem to be solved by the present invention relates to: water-based inkjet ink with excellent anti-blocking, anti-friction and lamination strength, pigment dispersion capable of preparing the inkjet ink, and printed matter obtained by inkjet printing using the inkjet ink.

[0012] Methods for solving problems

[0013] In order to solve the above-mentioned problems, the inventors conducted active research and found that the above-mentioned problems could be solved by using a pigment dispersion with a specific polyurethane resin as a binder, thereby completing the present invention.

[0014] That is, the present invention relates to the following invention.

[0015] (1) A pigment dispersion for inkjet printing, comprising a binder (A), a pigment (B), and an aqueous medium (C), characterized in that,

[0016] The adhesive (A) described above is an adhesive containing a polyurethane resin (A1) as a reactant of a polyol (a1) and a polyisocyanate (a2). The polyol (a1) includes a polyol (a1-1) having an acid group and a polyester polyol (a1-2) other than the polyol (a1-1). The polyisocyanate (a2) includes a polyisocyanate (a2-1) having a cyclic structure.

[0017] Some or all of the acid groups in the aforementioned polyurethane resin (A1) are neutralized.

[0018] The glass transition temperature of the polyurethane resin (A1) is below 70°C.

[0019] (2) According to the inkjet pigment dispersion of (1), the acid value of the polyurethane resin (A1) is 10 to 40 mg KOH / g.

[0020] (3) According to (1) or (2) the inkjet pigment dispersion, the content of the binder (A) is 5 to 30% by mass of the total amount of pigment dispersion.

[0021] (4) The inkjet pigment dispersion according to any one of (1) to (2) is used for printing on plastic substrates.

[0022] (5) An inkjet ink that uses an inkjet pigment dispersion of any one of (1) to (4).

[0023] (6) A printed matter made by printing with inkjet ink of (5).

[0024] Invention Effects

[0025] According to the present invention, water-based inkjet inks with excellent anti-blocking, anti-friction, and lamination strength can be obtained. Detailed Implementation

[0026] The "pigment dispersion for inkjet ink" of the present invention (hereinafter, sometimes simply referred to as "pigment dispersion" or "dispersion") contains a binder (A), a pigment (B), and an aqueous medium (C). Hereinafter, "binder (A)" is sometimes referred to as "component (A)," and the same applies to other components.

[0027] The pigment dispersion of the present invention is manufactured as an intermediate product for inkjet inks, and after dilution, it is used as an aqueous inkjet ink for inkjet printing.

[0028] <Adhesive (A)>

[0029] The adhesive (A) contains polyurethane resin (A1), which is a reaction product of polyol (a1) and polyisocyanate (a2).

[0030] (Polyurethane resin (A1))

[0031] The polyurethane resin (A1) in this invention is a resin obtained by reacting a polyol (a1) with a polyisocyanate (a2). It is obtained by polymerizing components (a1) and (a2) in the presence of any polymerization initiator using known methods such as free radical polymerization. The presence of acid groups in the resin (A1) imparts hydrophilicity to the polyurethane resin (A1), allowing the pigment (B) to be stably dispersed in water.

[0032] • Polyols (a1)

[0033] The polyol (a1) in this invention includes polyols having acid groups (a1-1) and polyester polyols (a1-2) other than the polyols (a1-1) mentioned above.

[0034] Among polyols (a1-1) containing acid groups, examples of acid groups include carboxyl groups, sulfonic acid groups, phosphoric acid groups, and thiocarboxyl groups, with carboxyl groups or sulfonic acid groups being preferred.

[0035] Examples of carboxyl-containing polyols include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvalerate. Among these, 2,2-dimethylolpropionic acid and 2,2-dimethylolbutyric acid, which exhibit good dispersion stability, are preferred. Alternatively, carboxyl-containing polyester polyols obtained by reacting carboxyl-containing polyols with various polycarboxylic acids can also be used. These carboxyl-containing polyols can be used alone or in combination of two or more.

[0036] Examples of polyols containing sulfonic acid groups include polyester polyols obtained by reacting dicarboxylic acids such as 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid, and 5-(4-sulfophenoxy)isophthalic acid, or their salts, with low-molecular-weight polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and neopentyl glycol. These polyols containing sulfonic acid groups can be used alone or in combination of two or more.

[0037] The acid-containing polyol (a1-1) is preferably used in a range that makes the acid value of the polyurethane resin (A1) 10 to 30 mg KOH / g, and more preferably in a range that makes the acid value of the polyurethane resin (A1) 10 to 28 mg KOH / g. It should be noted that the acid value mentioned in this invention is a theoretical value calculated based on the amount of acid-containing compounds such as the acid-containing polyol (a1-1) used in the manufacture of the polyurethane resin (A1).

[0038] In this invention, some or all of the acid groups in the polyol (a1-1) containing acid groups are neutralized. By neutralizing some or all of the acid groups, good water dispersibility can be achieved.

[0039] There are no particular limitations on the methods of neutralization; for example, neutralization using metals or organic amines can be cited.

[0040] The metal used for neutralization is not particularly limited, but it is preferable to neutralize with metal ions such as sodium, potassium, calcium, copper, and lithium to form a metal salt. Alternatively, it is acceptable as long as at least some of the acid groups are neutralized to form a metal salt.

[0041] Metal ions such as sodium, potassium, calcium, copper, and lithium that can be used to neutralize acid groups are obtained from 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.

[0042] Organic amines used in neutralization include polyalkylene imines, polyallylamines, (poly)ethylene polyamines, alkanolamines, and alkylamines.

[0043] From the viewpoint of pigment dispersibility, alkylamines are preferred.

[0044] The polyalkylene imine is preferably a polyalkylene imine having an alkylene group with 2 to 5 carbon atoms, more preferably a polyalkylene imine having an alkylene group with 2 to 4 carbon atoms, further preferably a polyethylene imine or a polypropylene imine, and particularly preferably a polyethylene imine. One or more of these can be used.

[0045] 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 1000 or more, and preferably 10000 or less, more preferably 5000 or less, and even more preferably 4000 or less.

[0046] Polyallylamines include homopolymers or copolymers of allyl compounds such as allylamine and dimethylallylamine, which are polymers with amino groups in their side chains.

[0047] The weight-average molecular weight of polyallylamine is preferably 800 or more, more preferably 1000 or more, even more preferably 1500 or more, and preferably 10000 or less, more preferably 5000 or less, and even more preferably 4000 or less.

[0048] Examples of (poly)ethylene polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. Among these, ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine are preferred, and ethylenediamine is particularly preferred.

[0049] As an alkanolamine, an alkanolamine with 2 to 9 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, tertiary alkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, and tertiary alkanolamines such as triethanolamine and triisopropanolamine. Among these, tertiary alkanolamines with 2 to 9 carbon atoms are preferred, and triisopropanolamine is particularly preferred.

[0050] As an alkylamine, an alkylamine with 1 to 6 carbon atoms is preferred. Examples of alkylamines include primary amines such as propylamine, butylamine, and hexylamine; secondary amines such as diethylamine and dipropylamine; and tertiary amines such as triethylamine.

[0051] Polyester polyol (a1-2) is a polyester polyol that does not belong to the above-mentioned polyol (a1-1). By using polyester polyol (a1-2), the polarity and Tg value can be controlled by the presence of ester groups in the structure, thereby imparting appropriate softness and adhesion to the substrate to the polyurethane resin (A1), resulting in improved lamination strength and abrasion resistance.

[0052] Polyester polyols (a1-2) are reaction products (condensation polymers) obtained by reacting polycarboxylic acids with polyols (e.g., polycondensation). Polyester polyols have structural units derived from polycarboxylic acids and structural units derived from polyols.

[0053] Examples of polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, adipic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dimer acid, trimellitic acid, benzoyltetracarboxylic acid, benzoylpentacarboxylic acid, and benzoylhexacarboxylic acid.

[0054] Examples of polyols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, and 1,4-cyclohexanediol; 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, and 2-butyl-2-ethyl-1,3-propanediol. Diols with branched structures, such as alcohols, 1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-ethyl-1,6-hexanediol, 3,5-heptanediol, and 2-methyl-1,8-octanediol; glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, and sorbitol.

[0055] As for the polyester polyol (a1-2), considering its good compatibility with pigments (B) and the like, the number-average molecular weight is preferably in the range of 500 to 8,000, more preferably in the range of 800 to 7,000, and even more preferably in the range of 900 to 6,000. In this invention, the number-average and weight-average molecular weights are values ​​determined by gel permeation chromatography (GPC).

[0056] The polyol (a1) may also contain polyols other than those with acid groups (a1-1) and polyester polyols (a1-2). For example, it may also contain polyether polyols, polycarbonate polyols, and polyols with cyclic structures other than those mentioned above.

[0057] • Polyisocyanate (a2)

[0058] Polyisocyanate (a2) comprises polyisocyanate (a2-1) having a cyclic structure.

[0059] Examples of ring structures include cyclobutyl ring, cyclopentyl ring, cyclohexyl ring, cycloheptyl ring, cyclooctyl ring, propylcyclohexyl ring, tricyclic [5.2.1.0.2.6]decyl skeleton, bicyclic [4.3.0]nonyl skeleton, tricyclic [5.3.1.1]dodecyl skeleton, propyltricyclic [5.3.1.1]dodecyl skeleton, norbornene skeleton, isobornyl skeleton, bicyclic pentyl skeleton, adamantyl skeleton, and other alicyclic structures; as well as aromatic ring structures such as benzene ring and naphthalene ring.

[0060] Examples of polyisocyanates with an alicyclic structure (a2-1) include cyclohexane diisocyanate, hydrogenated phenyl dimethyl diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, etc.

[0061] Examples of polyisocyanates (a2-1) having an aromatic ring structure include 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenyl diisocyanate, toluene diisocyanate, naphthalene diisocyanate, phenyl dimethyl diisocyanate, tetramethylphenyl dimethyl diisocyanate, etc.

[0062] The preferred formulation is toluene diisocyanate or isophorone diisocyanate, with toluene diisocyanate being particularly preferred.

[0063] These polyisocyanates (a2-1) can be used alone or in combination of two or more.

[0064] Polyisocyanates (a2) may also include isocyanate compounds (a2-2) other than polyisocyanates (a2-1) having a cyclic structure.

[0065] As an isocyanate compound other than (a2-1), (a2-2) can be used with polyols that do not have a ring structure, such as hexamethylene diisocyanate, lysine diisocyanate and other aliphatic polyisocyanates.

[0066] As a method for manufacturing polyurethane resin (A1) obtained by reacting polyol (a1) with polyisocyanate (a2), for example, a method can be described in which the polyol (a1) and the polyisocyanate (a2) are mixed in the absence of solvent or in the presence of organic solvent, and the reaction is carried out in the range of about 50°C to 150°C.

[0067] The reaction between the polyol (a1) and the polyisocyanate (a2) is preferably carried out in an equivalent ratio of the isocyanate group of the polyisocyanate (a2) to the hydroxyl group of the polyol (a1) of 0.8 to 2.5, and more preferably in the range of 0.9 to 1.5.

[0068] The polyurethane resin (A1) of the present invention necessarily contains a cyclic structure derived from the polyisocyanate (a2-1) having a cyclic structure within its resin structure. Furthermore, when the polyol (a1) contains a polyol having a cyclic structure, the alicyclic structure derived therefrom also constitutes the polyurethane resin (A1). By giving the polyurethane resin (A1) an alicyclic structure, its abrasion resistance can be improved.

[0069] Relative to the entire polyurethane resin (A1) described above, the ring structure preferably exists in the range of 500 to 5000 mmol / kg, more preferably 600 to 4000 mmol / kg, even more preferably 800 to 3500 mmol / kg, and particularly preferably 800 to 2000 mmol / kg.

[0070] It should be noted that the proportion of the alicyclic structure contained in the polyurethane resin (A1) mentioned in this invention relative to the total polyurethane resin (A1) is a theoretical value calculated based on the total mass of all raw materials such as polyol (a1) and polyisocyanate (a2) used in the manufacture of polyurethane resin (A1), and the mass of the ring structure of the compound containing the ring structure used in the manufacture of polyurethane resin (A1).

[0071] In addition, chain extenders may be used as needed when manufacturing the polyurethane resin (A1) described above.

[0072] Examples of chain extenders mentioned above include polyamines, hydrazine compounds, and other compounds with active hydrogen atoms. These chain extenders can be used alone or in combination of two or more.

[0073] Examples of the aforementioned polyamines include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophorone diamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, and 1,4-cyclohexanediamine; N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylaminoethylamine, N-methylaminopropylamine, diethylenetriamine, dipropylenetriamine, and triethylenetetramine. Piperazine or ethylenediamine is preferred.

[0074] Examples of the aforementioned hydrazine compounds include hydrazine, N,N'-dimethylhydrazine, 1,6-hexamethylene dihydrazine, succinic dihydrazine, adiponic dihydrazine, glutaronic dihydrazine, sebacic dihydrazine, isophthalic dihydrazine, β-aminourea propionic hydrazine, 3-aminourea-propyl-hydrazyl carbamate, and aminourea-3-aminourea-methyl-3,5,5-trimethylcyclohexane. Among these, hydrazine is preferred.

[0075] Other compounds containing active hydrogen mentioned above include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylenediol, sucrose, methylenediol, glycerol, sorbitol, and other diols; bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, hydroquinone, and other phenols, as well as water.

[0076] Organic solvents that can be used in the manufacture of polyurethane resin (A1) include, for example, ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; acetate solvents such as ethyl acetate and butyl acetate; nitrile solvents such as acetonitrile; and amide solvents such as dimethylformamide and N-methylpyrrolidone. These organic solvents can be used alone or in combination of two or more.

[0077] The glass transition temperature (Tg) of the polyurethane resin (Al) is below 70°C, preferably below 50°C, and more preferably below 40°C. Good resistance to adhesion can be obtained when the Tg is within this range.

[0078] From the viewpoint of improving energy efficiency by reducing the drying temperature during the manufacture of printed materials, the minimum film-forming temperature (MFT) of polyurethane resin (A1) is preferably 40°C or less, more preferably 35°C or less, and even more preferably 33°C or less.

[0079] In addition, regarding the aforementioned organic solvents, in order to seek safety and reduce the environmental impact, some or all of the aforementioned organic solvents may be removed during or after the manufacturing of the aforementioned polyurethane resin (A1), for example, by vacuum distillation.

[0080] From the perspective of exhibiting the durability of printed matter, the polyurethane resin (A1) obtained by the above method is preferably a polyurethane resin with a weight-average molecular weight in the range of 5,000 to 500,000, more preferably a polyurethane resin with a weight-average molecular weight in the range of 5,000 to 200,000, and even more preferably a polyurethane resin with a weight-average molecular weight in the range of 20,000 to 100,000.

[0081] It should be noted that the weight-average molecular weight (converted to polystyrene) determination using GPC (gel permeation chromatography) in this invention was performed using an HLC8220 system manufactured by Tosoh Corporation under the following conditions.

[0082] Separation column: Four TSKgelGMHHR-N series columns manufactured by Tosoh Corporation were used.

[0083] Mobile phase: Tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd.

[0084] Flow rate: 1.0 ml / min. Sample concentration: 0.4% by mass.

[0085] Sample injection volume: 100 μL. Detector: Differential refractometer.

[0086] When the weight-average molecular weight is above 5,000, not only is the durability of the printed matter improved, but it is also less prone to problems such as sticking caused by poor drying. In addition, when the molecular weight is below 500,000, it is less prone to problems such as decreased ink expulsion. Therefore, it is preferred.

[0087] The content (solid component) of binder (A) is preferably 5 to 30% by mass of the total amount of pigment dispersion, more preferably 5 to 25% by mass, and even more preferably 5 to 15% by mass.

[0088] The adhesive (A) may consist of only polyurethane resin (A1) or may contain other resins.

[0089] <Pigment (B)>

[0090] There are no particular limitations on the pigment (B) as long as it can be well dispersed in the dispersion, but it is preferred to use a pigment that can be dispersed with an average particle size of about 10 to 400 nm (details below). For example, organic pigments, inorganic pigments, and dyes commonly used in inks, coatings, and recording agents can be used.

[0091] Organic pigments include azo, phthalocyanine, anthraquinone, perylene, pyrene, quinacridone, thioindole, dioxazine, isoindolineone, quinolineone, azomethylazo, diketopyrrolopyrrole, and isoindoline pigments. From the perspectives of cost and lightfastness, copper phthalocyanine is preferred for blue inks.

[0092] 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 (METASHINE; Nippon Sheet Glass Co., Ltd.) obtained by coating glass flakes or bulk flakes with metals or metal oxides can be used. From the perspectives of cost and tinting strength, titanium dioxide is preferred for white inks, carbon black is preferred for black inks, aluminum is preferred for gold and silver inks, and mica is preferred for pearlescent inks.

[0093] 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, it can be measured by known methods such as dynamic light scattering after the dispersion is prepared, with the pigment uniformly dispersed in the dispersion. 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. A volume average particle size of 50 nm or more can suppress pigment aggregation during storage. Furthermore, an ink dischargeability is improved by a volume average particle size of 400 nm or less (particularly preferably 100 nm or less).

[0094] The pigment content in the dispersion is not particularly limited, but is preferably 10-30% by mass in the total dispersion. If it is less than 10% by mass, there is a concern that sufficient ink tinting strength cannot 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, there is a concern that the pigment may agglomerate during dispersion transport and storage, in which case the dispersibility of 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.

[0095] 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, it is possible to properly balance ink tinting strength and ink discharge properties.

[0096] Furthermore, when the pigment is an inorganic pigment, the content is preferably 25-60% by mass, more preferably 30-50% by mass.

[0097] <Aqueous Medium (C)>

[0098] In order to prepare a viscosity suitable for pump delivery and filter filtration of the dispersion, the pigment dispersion of the present invention further contains an aqueous medium.

[0099] Examples of aqueous media (C) include water, organic solvents mixed with water, and mixtures thereof.

[0100] Examples of organic solvents that can be mixed with 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. In this invention, water may be used alone; alternatively, a mixture of water and an organic solvent mixed with water may be used; or only an organic solvent mixed with water may be used.

[0101] As an aqueous medium (C), from the perspective of safety and environmental impact, it is preferable to use only water or a mixture of water and an organic solvent mixed with water, and it is particularly preferable to use only water.

[0102] <Other arbitrary ingredients>

[0103] The pigment dispersion of the present invention may also contain any other components besides (A), (B) and water (C) mentioned above, without impairing the effects of the present invention.

[0104] Other components include, for example, amine compounds with a boiling point of 100°C or higher, other resins besides those listed above, surfactants, waxes, low surface tension organic solvents, wetting agents, penetrants, dispersants besides those listed above, defoamers, preservatives, viscosity modifiers, pH modifiers, chelating agents, plasticizers, antioxidants, ultraviolet absorbers, etc.

[0105] By adding amine compounds with boiling points above 100°C, excessive drying of the ink is further suppressed, and the ink does not cause nozzle clogging. As a result, the discharge properties become good, achieving a balance between discharge properties and abrasion resistance.

[0106] Examples of such amine compounds include polyalkylene imines, polyallylamines, (poly)ethylene polyamines, alkanolamines, and alkylamines.

[0107] From the viewpoints of pigment dispersibility, odor, and resolubility, alkanolamines are preferred.

[0108] (Polyalkylimide)

[0109] The polyalkylene imide is preferably a polyalkylene imide having an alkylene group having 2 to 5 carbon atoms.

[0110] The polyalkylene imine is preferably a polyalkylene imine with 2 to 4 carbon atoms in the alkylene group, more preferably a polyethylene imine or a polypropylene imine, and even more preferably a polyethylene imine. One or more of them may be used.

[0111] 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.

[0112] The molecular weight value was determined using the method described in the examples.

[0113] (Polyallylamine)

[0114] Polyallylamines include homopolymers or copolymers of allyl compounds such as allylamine and dimethylallylamine, which are polymers with amino groups in their side chains.

[0115] 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.

[0116] (Polyethylidene polyamine)

[0117] Examples of (poly)ethylene polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. Among these, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine are preferred.

[0118] (Alkylamine)

[0119] As an alkanolamine, an alkanolamine with 2 to 9 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, tertiary alkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, and tertiary alkanolamines such as triethanolamine and triisopropanolamine. Among these, tertiary alkanolamines with 2 to 9 carbon atoms are preferred, and triisopropanolamine is particularly preferred.

[0120] (alkylamine)

[0121] As an alkylamine, an alkylamine with 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.

[0122] Other resins may be aqueous resins suitable for preparing pigment dispersions. Preferred examples include, for instance, acrylic resins such as polyvinyl alcohol, polyvinylpyrrolidone, 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.

[0123] Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, among which anionic surfactants or nonionic surfactants are preferred.

[0124] 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, and polyoxyethylene alkyl ether phosphates. Specific examples include dodecylbenzene sulfonate, isopropylnaphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, and dibutylphenylphenol disulfonate.

[0125] 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 amides, fatty acid hydroxyalkylamides, alkylalkanolamides, acetylenide glycol, ethoxylated adducts of acetylenide glycol, polyethylene glycol-polypropylene glycol block copolymers, and alkylphenol ethoxylates. 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, ethoxylated adducts of acetylenide glycol, polyethylene glycol-polypropylene glycol block copolymers, and alkylphenol ethoxylates are preferred.

[0126] 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 spiculisporic acid, rhamnolipid, and lysophosphatidylcholine.

[0127] These surfactants can be used alone or in combination 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.

[0128] Commercially available fluorinated surfactants include: NOVEC FC-4430 and FC-4432 (manufactured by Sumitomo 3M); Zonyl FSO-100, FSN-100, FS-300, and FSO (manufactured by DuPont); Eftop EF-122A, EF-351, 352801, and 802 (manufactured by JEMCO); MEGAFAC F-470, F-1405, F-474, and F-444 (manufactured by DIC); Surflon S-111, S-112, S-113, S121, S131, S132, S-141, and S-145 (manufactured by Asahi Glass); FTERGENT series (manufactured by NEOS); Fluorad FC series (manufactured by Minnesota Mining and Manufacturing Co.); Monflor (manufactured by Imperial Chemical Industries); and Lichove. VPF series (manufactured by Farbwerke Hoechst).

[0129] 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).

[0130] Examples of polyoxyethylene alkyl ether surfactants include the BT series (Nikko Chemicals), the NONIPOLE series (Sanyo Chemicals), the D-, P- series (Takemoto Oils & Fats), the EMLEX DAPE series (Nihon Emulsion), and the Pegnol series (Toho Chemical Industry). Examples of polyethylene glycol alkyl ester surfactants include Pegnol (Toho Chemical Industry).

[0131] Examples of acetylene glycol surfactants include Olfine E1010, STG, and Y (manufactured by Nissin Chemical Co., Ltd.); and Surfynol 104, 82, 420, 440, 465, 485, and TG (manufactured by Air Products and Chemicals Inc.).

[0132] Examples of waxes include plant and animal-based waxes such as carnauba wax, candelilla wax, beeswax, rice bran wax, and lanolin; mineral-based waxes such as lignite wax and ceresin wax; so-called petroleum-based waxes such as paraffin wax; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, silicone wax, and stearamide; natural-synthetic wax emulsions and composite waxes such as α-olefin-maleic anhydride copolymers. These waxes impart a smooth surface to the formed recording material, thereby improving its abrasion resistance. One type or a mixture of these waxes can be used. Silicone waxes, polyolefin waxes, and paraffin waxes are preferred.

[0133] Commercially available silicone waxes include, for example, SM8706EX, SM7036EX, SM7060EX, SM7025EX, SM490EX, SM8701EX, SM8709SR, SM8716SR, IE-7045, IE-7046T, SH7024, BY22-744EX, BY22-818EX, FZ-4658, FZ-4634EX, and FZ-4602 (these are trade names, manufactured by Toray Industries, Inc.); POLON-MF-14, POLON-MF-14EC, POLON-MF-23, and 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.

[0134] 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. One type of polyolefin wax can be used alone or in combination of two or more. From the viewpoint of minimizing reaction with the crosslinking groups of the aforementioned polyurethane resin particles having crosslinking groups, thus ensuring excellent discharge stability, polyethylene waxes are preferred.

[0135] Commercially available polyolefin waxes include, for example, AQUACER 513 (polyethylene wax, average particle size 100nm-200nm, melting point 130℃, solids content 30%), AQUACER 507, AQUACER 515, AQUACER 840, AQUACER 1547 (trade names, manufactured by BYK-Chemie Japan Co., Ltd.) and other AQUACER series products; 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 waxes) and other HITEC series products; and 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.

[0136] 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, consisting mainly of straight-chain paraffin hydrocarbons with 20-30 carbon atoms and containing small amounts of isoparaffin hydrocarbons. By incorporating paraffin wax into the ink, the recorded material can be given a smooth, water-repellent property, thereby improving its abrasion resistance.

[0137] Commercially available paraffin products include, for example, AQUACER537 and AQUACER539 (these are product names, manufactured by BYK-Chemie Japan Co., Ltd.).

[0138] 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 the appropriate range for ejection using the inkjet head, and also makes it easier to ensure ejection stability and intermittent ejection characteristics during recording.

[0139] As low surface tension organic solvents, examples of glycol ether compounds include diethylene glycol mono(alkyl) ethers (1 to 8 carbon atoms), triethylene glycol mono(alkyl) ethers (1 to 8 carbon atoms), propylene glycol mono(alkyl) ethers (1 to 6 carbon atoms), and dipropylene glycol mono(alkyl) ethers (1 to 6 carbon atoms), which can be used in the form of one or a mixture of two or more.

[0140] Specific examples include: 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 ... Dipropylene 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.

[0141] 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, 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 28, and most preferably in the range of 18 to 25.

[0142] As a wetting agent, there are no particular limitations, but substances that are miscible with water and can prevent inkjet printer head clogging are preferred. 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. Diol compounds such as 1,2-nonanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-nonanediol, and 1,2-octanediol; 1,4-butanediol, 1,3-butanediol, erythritol, and pentaerythritol; nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidineone, and ε-caprolactam. Among these, the inclusion of propylene glycol and 1,3-butanediol demonstrates safety and exhibits excellent ink drying and ejection properties.

[0143] The preferred content of wetting agent in ink is 3-50% by mass.

[0144] 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.

[0145] <Methods for manufacturing pigment dispersions>

[0146] The method for manufacturing the pigment dispersion in this invention is not limited in any way.

[0147] Pigment dispersions can be prepared by dispersing components (A) to (C) and any other components added as needed. Alternatively, a pigment dispersion grinding base solution with a high pigment concentration can be prepared in advance from components (A), (B), a portion of component (C), and a medium, and then any other components can be added appropriately. This 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 preparing a pigment dispersion grinding base solution in advance using a stirring and dispersing device to disperse the pigment, an aqueous pigment dispersion with the desired volume average particle size can be easily obtained.

[0148] The following describes the latter method of preparing a pigment dispersion after making a pigment dispersion grinding base liquid.

[0149] The following methods can be listed as methods for manufacturing pigment dispersion and grinding base liquid.

[0150] (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.

[0151] (2) A method of mixing pigments and pigment dispersants as needed using a double roller mill, mixer or other mixing machine, adding the obtained mixture to an aqueous medium, and preparing pigment dispersion grinding base liquid using a stirring and dispersing device.

[0152] (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 obtained solution, using a stirring and dispersing device to disperse the pigment in the organic solution, then using an aqueous medium to emulsify it by phase inversion, and then distilling to remove the organic solvent.

[0153] Examples of mixing and dispersing devices include ultrasonic homogenizers, high-pressure homogenizers, paint vibrators, ball mills, roller mills, sand mills, sand grinders, DYNO-MILL, Dispermat, SC MILL, and Nanomizer. One of these devices can be used alone, or two or more devices can be used in combination.

[0154] Inkjet ink

[0155] Using the pigment dispersion of the present invention, water-based inkjet ink is prepared by diluting it with an aqueous medium in such a way that the pigment content is 1 to 30% by mass. The aqueous medium, like component (C), can be water, a mixture of water and an organic solvent, or simply an organic solvent. As for the organic solvent, there are no particular limitations as long as it is mixed with water; examples of organic solvents described above in any component can be listed as "solvents other than water".

[0156] In addition, the aqueous medium may contain any component of the pigment dispersion (e.g., surfactants, preservatives, surface tension modifiers, etc.).

[0157] <Printed Materials>

[0158] The inkjet ink of the present invention has excellent printing properties on various substrates, and therefore can be used to manufacture printed materials having a plastic substrate and a printing layer obtained by inkjet ink.

[0159] Examples of plastic substrates include polyamide resins such as Ny6, Nylon 66, and Nylon 46; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polypropylene terephthalate, 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 plastic substrates and laminates thereof composed of 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 may be used appropriately.

[0160] Alternatively, the plastic substrate can also be a plastic film. The plastic film can be either an unstretched or stretched film, and its manufacturing method is not limited. Furthermore, the film thickness is not particularly limited; typically, a range of 1–500 μm is sufficient.

[0161] In addition, it is preferable to perform corona discharge treatment on the printed surface of the film. Alternatively, silicon dioxide, aluminum oxide, etc., can be vapor-deposited onto the printed surface.

[0162] The printed materials of the present invention are suitable for use as packaging materials because of their excellent printability on plastic substrates and the fact that they can be produced by inkjet printing. In particular, due to their excellent design flexibility and printability on demand, they are especially suitable for food packaging applications. Furthermore, the inkjet inks of the present invention have excellent abrasion resistance, allowing for the production of surface-printed materials obtained by inkjet printing on a surface.

[0163] Example

[0164] The present invention will now be specifically described through examples and comparative examples. Unless otherwise specified, “parts” refers to “parts by mass” and “%” refers to “% by mass”.

[0165] The adhesives (1) to (3) used in this embodiment and the comparative adhesives (1) to (5) are shown below.

[0166] [Table 1]

[0167]

[0168] [Table 2]

[0169]

[0170] [Manufacturing Example: Preparation of Pigment Dispersions]

[0171] After the white pigment base is better stirred and mixed into the following composition, it is compounded by bead milling (using 1.0mmφ YTZ beads from Nikkato Corporation, with a bead filling rate of 80%), and the volume average particle size of the pigment is measured in the same manner as above to produce a compound base with a volume average particle size of 280nm.

[0172]

[0173] [Preparation of aqueous pigment dispersions for the preparation of water-based inkjet inks]

[0174] Various aqueous pigment dispersions were prepared according to the following composition, with the pigment concentration in the aqueous pigment dispersion being 30% by weight. Regarding the binder, the binders described in the examples above were used in an amount such that the solid component amount was 10.5% by weight of the total pigment dispersion.

[0175]

[0176] Preparation of water-based inkjet inks for plastic substrates

[0177] The water-based inkjet inks for plastic substrates of Examples 1-3 and Comparative Examples 1-5 were prepared according to the following ink composition, with the pigment concentration in the water-based inkjet ink for plastic substrates being 8% by weight.

[0178]

[0179] [Evaluation of the production of printing film: Inkjet printing]

[0180] The pigment dispersions of each example were filled into the ink cartridge of an inkjet printer (manufactured by Seiko Epson Corporation, MJ-510C). After printing the full-page pattern on corona-treated polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., ESTERE5100, 12μm thick) or corona-treated polypropylene (OPP) biaxial stretch film (manufactured by Toyobo Co., Ltd., PYLEN P2161, 20μm thick) as shown in Tables 1 and 2, the prints were dried in a dryer and then further dried in an 80°C oven for 10 minutes to obtain the printed material.

[0181] <Evaluation of the production of printed materials>

[0182] The ink compositions of the examples and comparative examples were filled into the ink cartridge of an inkjet printer (manufactured by Seiko Epson Corporation, MJ-510C). After printing the entire surface of the image on corona-treated polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., ESTERE5100, 12 μm thick) or corona-treated polypropylene (OPP) biaxial stretch film (manufactured by Toyobo Co., Ltd., PYLEN P2161, 20 μm thick), the images were dried in a dryer and then further dried in a 90°C oven for 10 minutes to obtain the printed material.

[0183] The obtained printed materials were evaluated using the evaluation methods shown below. The results are recorded in the table below.

[0184] <Anti-adhesion evaluation>

[0185] After cutting the film into 4cm x 4cm pieces, overlap them with the printed and non-printed sides of the printed material, and apply a 5kgf / cm pressure. 2 After the load was placed at 50°C for 24 hours, the transfer of ink to the non-printing surface (staining) was visually determined based on the area ratio (%) of the contaminated part when the film was peeled off.

[0186] ◎: No transfer to non-printing surfaces was observed.

[0187] 〇: Although it was less than 5%, transfer caused by contamination was observed.

[0188] △: Although it is between 5% and less than 10%, which is within the permissible range, transfer caused by contamination was observed.

[0189] ×: More than 10% of the transfer was caused by sticky contaminants.

[0190] <Lamination Strength Evaluation>

[0191] The lamination assessment was conducted in accordance with JIS Z 1707:2019. Details are as follows.

[0192] (OPP membrane)

[0193] Aromatic ether adhesives (LX401 and SP60, both manufactured by DIC) were mixed and diluted with ethyl acetate to a non-volatile content of 25%, thus preparing a heat-sealing adhesive. The adhesive was then applied at a concentration of 2 g / m³. 2 The coating is applied to the printed surface of the OPP film, and then a CCP film (PYLEN FILM-CT P1128, manufactured by Toyobo Co., Ltd.) is laminated onto it using a heated roller laminator set to 40°C. The laminate is then cured at 40°C for 3 days to produce the final product.

[0194] Select test pieces from the laminated film with a width of 10.0±0.1mm and an unfolded length of 100mm or more in the right-angle direction.

[0195] With the laminated portion of the test piece open 180° to the center, the clamp spacing is set to at least 50 mm, and both ends of the test piece are mounted on the clamps of a constant-speed elongation tensile testing machine. A tensile load is applied until the laminated portion fractures, and the maximum load (N / 10 mm) is determined. The lamination strength is evaluated according to the following criteria.

[0196] (PET film)

[0197] The heat-sealing adhesive used was an aliphatic-ester adhesive (LX703VL and KR-90, both manufactured by DIC Corporation), and the laminating film was an LLDPE film (TUX-HC, manufactured by Mitsui Tosel Corporation). In addition, the lamination strength was evaluated using the same method.

[0198] ◎: Maximum load (N / 10mm) is 3 or higher

[0199] 〇: Maximum load (N / 10mm) is 2 to less than 3

[0200] △: Maximum load (N / 10mm) is 1 to less than 2

[0201] ×: Maximum load (N / 10mm) is 0 to less than 1.

[0202] <Abrasion Resistance>

[0203] According to JIS K5701-1:2000, the abrasion resistance of OPP film printed materials was evaluated using a vibration-type rubbing fastness tester (manufactured by TESTER Sangyo Co., Ltd., AB-301). The printed materials were placed in the tester. For the dry rubbing test, PPC paper was used as the rubbing paper, and the test was conducted under conditions of a load of 200g and 100 cycles. For the wet rubbing test, fine white cloth No. 3 moistened with ion-exchanged water was used as the rubbing paper, and the test was conducted under conditions of a load of 200g and 10 cycles. The ink peeling in the printed materials after the test was evaluated visually according to the following evaluation criteria.

[0204] ◎: No peeling occurred in either the dry friction test or the wet friction test.

[0205] 〇: Less than 1% of the peeling occurs in either the dry friction test or the wet friction test, whichever is worse.

[0206] △: The worse of the dry friction test and wet friction test results in more than 1% but less than 5% peeling.

[0207] ×: In the dry friction test or the wet friction test, the worse result is that there is more than 5% but less than 10% peeling.

[0208] <Storage Stability Evaluation>

[0209] (Particle size and viscosity changes)

[0210] Each ink was stored in a constant temperature bath at 70°C for 5 days to conduct a test to promote storage stability.

[0211] The ink was measured before and after the storage stability promotion test using a nanoparticle size measuring device (Nanotrac wave II Ex150, manufactured by MicrotracBEL Co., Ltd.), and the average particle size before and after the storage stability promotion test was compared.

[0212] The ink viscosity before and after the storage stability promotion test was measured using an E-type viscometer (TVE-25L type, manufactured by Toki Sangyo). The viscosity before and after the storage stability promotion test was compared and evaluated on a three-level scale from A to C. A grade of B or above was considered acceptable.

[0213] A: The changes in average particle size and viscosity before and after the storage stability test were both less than 5%.

[0214] B: The change rate of the average particle size and viscosity, whichever is worse, before and after the storage stability test is 5% to 15%.

[0215] C: The worse of the two values, average particle size and viscosity, showed a change rate exceeding 15% before and after the storage stability test.

[0216] (Color change)

[0217] After conducting the same storage stability enhancement test as above, the color tone was visually confirmed and evaluated on a scale of A to C. A grade of B or higher was considered acceptable.

[0218] A: There was no color change before and after the test.

[0219] B: Slight color changes were observed before and after the experiment.

[0220] C: The color changed significantly before and after the test.

[0221] The evaluation results of the inkjet inks are recorded in the table below.

[0222] [Table 3]

[0223]

[0224] It can be confirmed that the inkjet inks of Examples 1 to 3 of the present invention have excellent adhesion resistance and abrasion resistance to plastic substrates, and exhibit excellent lamination strength when the adhesive is applied to the printed surface and the film is laminated.

[0225] On the other hand, the water-based inkjet inks of Comparative Examples 1-5 are different from the inks of Examples 1-3, and all of their properties are inferior.

[0226] Therefore, it can be confirmed that the pigment dispersion of the present invention is suitable for use in water-based inkjet inks.

Claims

1. An inkjet pigment dispersion comprising a binder A, a pigment B, and an aqueous medium C, for printing on plastic substrates, characterized in that: The adhesive A is an adhesive containing polyurethane resin A1 as a reactant of polyol a1 and polyisocyanate a2. The polyol a1 comprises polyol a1-1 having acid groups and polyester polyol a1-2 other than polyol a1-1. The polyisocyanate a2 comprises polyisocyanate a2-1 having a cyclic structure. Some or all of the acid groups in the polyurethane resin A1 are neutralized. The glass transition temperature of the polyurethane resin A1 is below 70°C. The minimum film-forming temperature (MFT) of the polyurethane resin A1 is below 40°C. The acid value of the polyurethane resin A1 is 10~40 mgKOH / g. The mass-average molecular weight of the polyurethane resin A1 is in the range of 35,000 to 100,000. The polyisocyanate a2-1 with a cyclic structure is toluene diisocyanate or isophorone diisocyanate.

2. The inkjet pigment dispersion according to claim 1, wherein the ring structure exists in the polyurethane resin A1 in the range of 500 to 5000 mmol / kg relative to the entire polyurethane resin A1.

3. The inkjet pigment dispersion according to claim 1 or 2, wherein the acid value of the polyurethane resin A1 is 10~30 mgKOH / g.

4. The inkjet pigment dispersion according to claim 1 or 2, wherein the content of binder A is 5 to 30% by mass of the total amount of pigment dispersion.

5. An inkjet ink that uses the inkjet pigment dispersion according to any one of claims 1 to 4.

6. A printed matter, printed using the inkjet ink of claim 5.

Images