Printing ink and printed material

Abstract

To provide a printing ink containing an isoindoline pigment, in which discoloration of the printing ink is suppressed over time and storage stability is excellent.SOLUTION: The problem is solved by a printing ink containing an isoindoline pigment and at least one amine (A) selected from the group consisting of primary amines and secondary amines, where the amine (A) has a molecular weight of 1000 or less. The amine (A), however, does not include alkanolamines, amides, and melamine.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to printing inks and printed matter.

Background Art

[0002] As a printing ink containing an organic pigment exhibiting a hue from yellow to red, a printing ink containing an azo pigment has been conventionally used. However, due to environmental considerations, there is an increasing demand for a printing ink containing an organic pigment exhibiting a hue from yellow to red to replace the azo pigment. As one such printing ink, printing inks containing isoindoline pigments such as C.I. Pigment Yellow 185, C.I. Pigment Yellow 139, and C.I. Pigment Red 260 have attracted attention. Since isoindoline pigments also have basic properties such as excellent color reproducibility and lightfastness, development for printing ink applications has been underway. For example, Patent Document 1 discloses an inkjet ink containing an isoindoline pigment. By the way, it is required that the color of the printing ink does not change during storage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a result of intensive studies by the present inventors, conventional printing inks containing isoindoline pigments have a problem that the printing ink may change color over time, and accordingly, it may adversely affect the color tone of the printed matter. Therefore, the problem to be solved by the present invention is to provide a printing ink containing an isoindoline pigment having excellent storage stability in which discoloration of the printing ink is suppressed over time.

Means for Solving the Problems

[0005] As a result of investigations to solve the above problems, the present inventors have found that by using an isoindoline pigment in combination with a specific amine, discoloration of the ink is suppressed and storage stability is improved, leading to the present invention.

[0006] That is, the present invention relates to a printing ink containing an isoindoline pigment and at least one amine (A) selected from the group consisting of primary amines and secondary amines, wherein the molecular weight of the amine (A) is 1000 or less. However, the above amine (A) excludes alkanolamines, amides, and melamines.

[0007] The present invention also relates to the above printing ink wherein the amine (A) is an amine other than an aromatic amine.

[0008] The present invention also relates to the above printing ink wherein the amine (A) is an amino acid or an aliphatic amine.

[0009] The present invention also relates to the above printing ink containing 0.5 to 30 parts by mass of the amine (A) with respect to 100 parts by mass of the above isoindoline pigment.

[0010] The present invention also relates to a printed matter of the above printing ink.

Advantages of the Invention

[0011] According to the present invention, it has become possible to provide a printing ink containing an isoindoline pigment with excellent storage stability in which discoloration of the printing ink is suppressed over time.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. The embodiments described below illustrate an example of the present invention and are not limited to the following embodiments.

[0013] The terms used in this specification will be described. "C.I." means Color Index (C.I.). Unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively. Also, the numerical range specified using "~" shall include the numerical values described before and after "~" as the range of the lower limit value and the upper limit value.

[0014] <Printing ink> Examples of the printing ink of the present invention include various printing inks such as offset printing ink, flexographic printing ink, gravure printing ink, silk screen printing ink, inkjet printing ink, etc. In particular, it can be preferably used for aqueous printing inks such as aqueous inkjet ink and aqueous flexographic ink. In this specification, a printing ink containing water as a solvent shall be referred to as an aqueous printing ink.

[0015] <Isindoline pigment> The printing ink of the present invention contains an isindoline pigment, and preferably contains an isindoline pigment having a structure represented by the following general formula (1).

[0016] [Chemical formula]

[0017] In general formula (1), R2 and R3 each independently represent a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted aryl group. A represents a group represented by the following formula (2), formula (3), or formula (4).

[0018] [Chemical formula]

[0019] In formula (2), X represents -O- or -NH-, and R4 represents an optionally substituted alkyl group or an optionally substituted aryl group. In formula (3), R5 and R6 each independently represent a hydrogen atom or an optionally substituted alkyl group. In formula (4), R7 represents a hydrogen atom, and R8 to R 11 each independently represent a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryl group, or an optionally substituted aryloxy group.

[0020] Examples of the pigment having the structure represented by the general formula (1) above include C.I. Pigment Yellow 139, 185, C.I. Pigment Red 260, etc. The above pigments may be included alone or in combination of two or more. When two or more are used in combination, they may be in a mixed crystal state.

[0021] Among the pigments exemplified above, from the viewpoint of excellent light resistance, color reproducibility, high coloring power, and obtaining a printed matter with excellent image density even with a small amount of addition, it is preferable to contain C.I. Pigment Yellow 139 or 185.

[0022] <Amine (A)> The printing ink of the present invention contains at least one amine (A) selected from the group consisting of primary amines and secondary amines. The molecular weight of amine (A) is 1000 or less. Also, amine (A) is an amine other than alkanolamine, amide, and melamine.

[0023] The isoinoline pigment described above is known to be weak in resistance to basic materials. Depending on the combination method, the isoinoline pigment may decompose. However, as a result of intensive studies by the present inventors, it has been found that when amine (A) is used, the isoinoline pigment is not decomposed and discoloration of the ink over time can be suppressed. Although the detailed factors are unknown, it is considered that the balance of acid and base in the ink and the reactivity with amine (A) suppress the discoloration of the isoinoline pigment.

[0024] Specific examples of amine (A) include hexylamine, cyclohexylamine, aniline, methylamine, isopropylamine, benzylamine, 3-picolylamine, ethylenediamine, glycine, taurine, β-alanine, L-phenylalanine, dipropylamine, and salts thereof. Among the above, it is preferably a primary amine. Amine (A) is preferably an amine other than an aromatic amine, more preferably an aliphatic amine. Also, amine (A) is preferably an amino acid, more preferably an aliphatic amino acid. Amine (A) may be contained in the printing ink in a form of forming a salt with an acid. Specific examples of the acid forming a salt with amine (A) include hydrochloric acid, acetic acid, sulfuric acid, phosphoric acid, oxalic acid, nitric acid, hydrobromic acid, adipic acid, malonic acid, glutaric acid, salicylic acid, stearic acid, etc. Among the above, hydrochloride and acetate are preferred. Amine (A) may be used alone or in combination of two or more.

[0025] Amine (A) may be mixed with the isoindoline pigment from the beginning or may be mixed later in the ink.

[0026] The content of amine (A) in the printing ink of the present invention is preferably 0.5 to 30 parts by mass, more preferably 1 to 15 parts by mass, based on 100 parts by mass of the isoindoline pigment.

[0027] <Dispersion medium> The printing ink of the present invention can contain a dispersion medium. Examples of the dispersion medium include resins and solvents. Examples of the resin include binder resins. Examples of the solvent include water and organic solvents.

[0028] The binder resin may be, for example, a polyolefin resin, a polyester resin, a styrene copolymer, an acrylic resin, or a modified resin thereof. Specifically, polyethylene such as high-density polyethylene (HDPE), linear low-density polyethylene (L-LDPE), low-density polyethylene (LDPE), polyolefin resins such as polypropylene; polyester resins such as polyethylene terephthalate; styrene copolymers such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; acrylic resins such as acrylic resin and methacrylic resin; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, silicone resin, polyurethane resin, ethylene-vinyl acetate copolymer resin, vinyl acetate resin, nitrocellulose resin, polyamide resin, epoxy resin, xylene resin, polyvinyl butyral resin, polyvinyl acetal resin, cellulose ester resin, alkyd resin, rosin resin, rosin modified phenol resin, ketone resin, cyclized rubber, chlorinated polyolefin resin, terpene resin, coumarone indene resin, amino resin, petroleum resin, and modified resins thereof, etc. Examples of commercially available binder resins include Joncryl 780, Joncryl 7610 manufactured by BASF Japan, JE-1056, JE-1113, X-436 manufactured by Starlight PMC, etc.

[0029] Organic solvents can be roughly classified into water-soluble solvents and water-insoluble solvents. Examples of water-soluble solvents include ethanol, butanol, 1,2-butanediol, n-propanol, isopropanol, isobutanol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, tetraethylene glycol, dipropylene glycol, ketone alcohol, ethylene glycol dibutyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, 1,2-hexanediol, N-methyl-2-pyrrolidone, substituted pyrrolidone, 2,4,6-hexanetriol, tetrafurfuryl alcohol, 4-methoxy-4-methylpentanone, glycerin, etc. Also included are monoethers derived from polyhydric alcohols. For example, methoxypropanol or methoxybutanol can be mentioned. Also included are glycol ethers such as butyl glycol or butyl diglycol. Examples of water-insoluble solvents include toluene, xylene, butyl acetate, methyl acetate, methyl ethyl ketone, methyl isobutyl ketone, butyl alcohol, aliphatic hydrocarbons, etc.

[0030] The printing ink of the present invention preferably contains water. Examples of water include ion-exchanged water, distilled water, etc.

[0031] <Dispersant> The printing ink of the present invention may contain a dispersant. The type of the dispersant is not particularly limited, and examples thereof include (meth)acrylic resins, styrene (meth)acrylic resins, maleic resins, styrene maleic resins, urethane resins, ester resins, amide resins, imide resins, and the like. The above-mentioned dispersants can be synthesized by known methods or commercially available products can be used. Also, the structure thereof is not particularly limited, and examples include random structures, block structures, comb-shaped structures, star-shaped structures, and the like. Further, in the case of aqueous printing inks, it is preferable that the acid groups in the dispersant are neutralized with a base in order to increase the solubility in water. As the base, organic compounds such as aqueous ammonia and triethanolamine, and inorganic compounds such as lithium hydroxide, sodium hydroxide, and potassium hydroxide can be used.

[0032] Examples of commercially available dispersants include JONCRYL67, JONCRYL678, JONCRYL586, JONCRYL611, JONCRYL683, JONCRYL690, JONCRYL57J, JONCRYL60J, JONCRYL61J, JONCRYL62J, JONCRYL63J, JONCRYLHPD-96J, JONCRYLHPD671, JONCRYL501J, JONCRYLPDX-6102B, EFKAPX4701 manufactured by BASF Japan Ltd.; DISPERBYK180, DISPERBYK187, DISPERBYK190, DISPERBYK191, DISPERBYK194, DISPERBYK2010, DISPERBYK2015, DISPERBYK2090, DISPERBYK2091, DISPERBYK2095, DISPERBYK2155, BYKJET-9151, BYKJET-9170, BYKJET-9171 manufactured by BYK-Chemie GmbH; SOLSPERSE24000, SOLSPERSE32000, SOLSPERSE41000 manufactured by Lubrizol Japan Ltd.; SMA1000H, SMA1440H, SMA2000H, SMA3000H, SMA17352H manufactured by Sartomer Company, Inc., and the like.

[0033] The blending amount of the dispersant is preferably 1 to 80 parts by mass with respect to 100 parts by mass of the pigment.

[0034] The acid value of the dispersant is preferably 0 to 400 mgKOH / g, more preferably 0 to 300 mgKOH / g, and still more preferably 0 to 220 mgKOH / g. Also, the amine value of the dispersant is preferably 0 to 250 mgKOH / g, more preferably 0 to 100 mgKOH / g, and still more preferably 0 to 50 mgKOH / g.

[0035] The acid value of the dispersant in this specification is the number of mg of potassium hydroxide (KOH) required to neutralize the acid contained in 1 g of the dispersant, and is a value titrated with a KOH solution in an ethanol / toluene mixed solvent.

[0036] The amine value of the dispersant in this specification is the number of mg of KOH having the same number of moles as the amount of hydrochloric acid (HCl) required to neutralize the amine contained in 1 g of the dispersant, and is a value titrated with an HCl solution in an ethanol / toluene mixed solvent. The measurement of the above acid value and amine value can be carried out, for example, using a "Potentiometric Automatic Titrator AT-610" manufactured by Kyoto Electronics Industry Co., Ltd.

[0037] <Surfactant> The printing ink of the present invention can contain a surfactant. Examples of the surfactant include cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, etc. Only one kind may be used alone, or two or more kinds may be used in combination.

[0038] Examples of the cationic surfactant include aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, etc.

[0039] Anionic surfactants include, for example, fatty acid salts, alkyl sulfate salts, alkylaryl sulfonate salts, alkylnaphthalene sulfonate salts, dialkyl sulfonate salts, dialkyl sulfosuccinate salts, alkyl diaryl ether disulfonate salts, alkyl phosphate salts, polyoxyethylene alkyl ether sulfate salts, polyoxyethylene alkylaryl ether sulfate salts, naphthalene sulfonic acid formalin condensates, and polyoxyethylene alkyl phosphate ester salts, etc.

[0040] Amphoteric surfactants include, for example, carboxybetaine type, sulfobetaine type, aminocarboxylate salts, imidazolinium betaine, etc.

[0041] Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, glycerol borate fatty acid esters, polyoxyethylene glycerol fatty acid esters, acetylene glycol-based, fluorine-based, silicone-based, etc. Commercially available products of surfactants include, for example, Adeka Pluronic (registered trademark) L-64 (manufactured by ADEKA).

[0042] As the addition amount of the surfactant, in 100 parts by mass of the ink, 0 to 10 parts by mass is preferable, 0 to 4 parts by mass is more preferable, and 0 to 3 parts by mass is even more preferable.

[0043] The printing ink of the present invention can contain other additives. Other additives include preservatives, pH adjusters, defoamers, wetting agents, drying accelerators, penetrants, chelating agents, leveling agents, waxes, film-forming aids, dye derivatives, etc. As an example of the addition amount of these additives, in 100 parts by mass of the ink, 0.01 to 10 parts by mass is suitable.

[0044] Examples of the preservative include sodium dehydroacetate, sodium benzoate, sodium pyridine thione-1-oxide, zinc pyridine thione-1-oxide, 1,2-benzisothiazolin-3-one, amine salts of 1-benzisothiazolin-3-one, and the like. Examples of commercially available preservatives include Proxel GXL (manufactured by SC Johnson).

[0045] Examples of the pH adjuster include alkanolamines such as triethanolamine, inorganic salts, ammonia, various buffers, and the like.

[0046] Examples of commercially available defoamers include Surfynol 104E, Surfynol 104H, Surfynol 104A, Surfynol 104BC, Surfynol 104DPM, Surfynol 104PA, Surfynol 104PG-50, Surfynol DF110D, Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485, Surfynol PSA-336 (all manufactured by Nissin Chemical Industry Co., Ltd.), ADDITOL VXW6211, ADDITOL VXW4973, ADDITOL VXW6235, ADDITOL XW375, ADDITOL XW376, ADDITOL VXW6381, ADDITOL VXW6386, ADDITOL VXW6392, ADDITOL VXW6393, ADDITOL VXW6399, ADDITOL XW6544 (all manufactured by Allnex), SN Deformer 777#C (manufactured by San Nopco), and the like.

[0047] Examples of commercially available wetting agents include ADDITOL VXL6237N, ADDITOL XL260N, ADDITOL VXL6212, ADDITOL UVX7301 / 65, ADDITOL XW330, ADDITOL VXW6200, ADDITOL VXW6205, ADDITOL VXW6394, ADDITOL VXW6208, ADDITOL VXW6208 / 60, ADDITOL VXW6374 (all manufactured by Allnex), Tegowet 280 (manufactured by EVONIK), and the like.

[0048] Examples of the drying accelerator include alcohols such as methanol, ethanol, and isopropyl alcohol.

[0049] Examples of the penetrant include surfactants such as polyethylene glycol monolauryl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, and sodium dioctyl sulfosuccinate, in addition to water-soluble solvents.

[0050] Examples of the chelating agent include ethylenediaminetetraacetic acid, the sodium salt of ethylenediaminetetraacetic acid, the diammonium salt of ethylenediaminetetraacetic acid, and the tetraammonium salt of ethylenediaminetetraacetic acid.

[0051] Examples of the dye derivative include known dye derivatives having an acidic group, a basic group, a neutral group, etc. in the organic dye residue. For example, compounds having an acidic substituent such as a sulfo group, a carboxy group, a phosphate group, etc. and their amine salts, compounds having a basic substituent such as a sulfonamide group or a tertiary amino group at the end, and compounds having a neutral substituent such as a phenyl group or a phthalimidoalkyl group.

[0052] The printing ink can further contain a brightening material. The brightening material is particles with an average thickness of 0.5 to 10 μm and an average particle diameter of 5 to 50 μm, and examples include metal flakes, mica, and coated glass flakes. Examples of the metal flakes include aluminum flakes and gold powder. Examples of the mica include ordinary mica and coated mica. Examples of the coated glass flakes include glass flakes coated with a metal oxide such as titanium oxide.

[0053] In addition, other coloring pigments and various additives commonly used in the art can be blended as needed. The manufacturing method, coating method, and drying method of the printing ink are not particularly limited, and methods well-known in the art can be used.

[0054] Hereinafter, an aqueous inkjet ink and an aqueous flexographic ink, which are one aspect of the present invention, will be described. <Water-based inkjet ink> Hereinafter, a water-based inkjet ink (hereinafter sometimes abbreviated as "inkjet ink") will be described.

[0055] From the viewpoints of color reproducibility of printed matter, storage stability, and dispersion stability of the ink, the total amount of pigment contained in the inkjet ink is preferably 1 to 10 parts by mass, more preferably 1.5 to 9.5 parts by mass, per 100 parts by mass of the inkjet ink.

[0056] <Water-based flexographic printing ink> Hereinafter, the water-based flexographic printing ink of the present specification will be described. The total amount of pigment contained in the water-based flexographic printing ink is preferably 5 to 60 parts by mass, more preferably 6 to 35 parts by mass, per 100 parts by mass of the water-based flexographic printing ink.

Examples

[0057] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples. In the following description, "parts", "%", and "ratio" are based on mass unless otherwise specified.

[0058] <Water-based inkjet ink> The following is an example of a water-based inkjet ink, which is one aspect of the printing ink of the present invention. The isoinoline pigments used are as shown below. Note that Pigment 2 was manufactured according to the method shown below. Pigment 1: Paliotol Yellow D 1155 (C.I. Pigment Yellow 185, manufactured by BASF) Pigment 2: Isoinoline pigment manufactured by the following method Pigment 3: Paliotol Yellow D 1819 (C.I. Pigment Yellow 139, manufactured by BASF)

[0059] <Manufacturing method of Pigment 2> The following production examples are cited from the examples of isoinoline compounds 1-5 described in JP-A-2022-031604. To a four-necked flask equipped with a reflux condenser, a dropping funnel, and a stirrer, 800 parts of water, 60 parts of 1,3-diiminisoindoline, and 120 parts of 28% aqueous ammonia were added in this order, and the mixture was stirred. Then, a solution prepared by dissolving 42.58 parts of 2-cyano-N-methylacetamide in 160 parts of water was added dropwise using the dropping funnel over 30 minutes. The mixture was heated and stirred at 30 °C until the starting 1,3-diiminisoindoline disappeared. The reaction slurry was filtered using a Buchner funnel to obtain a non-volatile fraction. The disappearance of the starting material was confirmed by high-performance liquid chromatography. To a four-necked flask equipped with a reflux condenser, a dropping funnel, and a stirrer, 60 parts of the non-volatile fraction obtained above, 480 parts of water, and 162 parts of 80% acetic acid were added, and the mixture was stirred. On the other hand, 326 parts of water and 138 parts of 80% acetic acid were added to the flask, and 27.18 parts of barbituric acid and 2.07 parts of 1,3-dimethylbarbituric acid were further added thereto, and the mixture was stirred at 65 °C. The heated solution of this mixture was poured into the liquid containing the stirring of the above non-volatile fraction, and the mixture was stirred at 30 °C for 3 hours. Further, 134 parts of water and 57 parts of 80% acetic acid were added to a separately prepared flask, and 14.49 parts of 1,3-dimethylbarbituric acid was further added thereto, and the mixture was stirred at 65 °C. This mixture was poured into the previous reaction solution, and the temperature was raised to 85 °C and stirred to complete the reaction. The heating and stirring were carried out until the above non-volatile fraction used as a starting material disappeared. The disappearance of the starting material was confirmed by high-performance liquid chromatography. Then, after cooling to 20 °C, the mixture was washed three times with 2400 parts of water to obtain a non-volatile fraction. This non-volatile fraction was dried in a hot air dryer at 80 °C to obtain 88.10 parts of Pigment 2.

[0060] The dispersants used are as shown below. Incidentally, Dispersant 3 was produced according to <Production of Varnish of Dispersant 3> shown below. Dispersant 1: BYKJET-9170 (manufactured by BYK, non-volatile content 40%, acid value 7 mg KOH / g, amine value 7 mg KOH / g) Dispersant 2: BYKJET-9171 (manufactured by BYK, non-volatile content 40%, amine value 28 mg KOH / g) Dispersant 3: Varnish (non-volatile content 20%, acid value 110 mg KOH / g) Dispersant 4: BYKJET-9151 (manufactured by BYK, non-volatile content > 98.5%, acid value 8 mg KOH / g, amine value 18 mg KOH / g)

[0061] <Manufacturing method of the varnish of Dispersant 3> Into a mixing container equipped with a stirrer, 20.2 parts of styrene-acrylic resin X-1 (weight average molecular weight 18,000, acid value 110 mg KOH / g) manufactured by Starlight PMC, 3.8 parts of dimethylaminoethanol, and 76.0 parts of water were added and stirred well to completely neutralize and solubilize the styrene-acrylic resin in water. Then, 1 g of the obtained solution was sampled, heated and dried at 180 °C for 20 minutes, and after measuring the non-volatile content, water was added so that the non-volatile content became 20%, thereby obtaining the varnish of Dispersant 3 (non-volatile content 20%).

[0062] [Example 1] <Manufacture of Pigment Dispersion 1 for Inkjet Ink> · Pigment 1: 4.00 parts · Dispersant 1: 4.00 parts · Defoamer (Surfynol DF110D manufactured by Nissin Chemical Industry Co., Ltd., non-volatile content 32%): 0.31 part · Ion-exchanged water: 18.36 parts The above materials and 75 parts of zirconia beads with a diameter of 0.30 mm were charged into a glass bottle, sealed, and dispersed with a paint shaker manufactured by Red Devil for 6 hours. Then, the zirconia beads were removed to obtain 26.67 parts of Pigment Dispersion 1 for Inkjet Ink.

[0063] <Manufacture of Aqueous Inkjet Ink 1> · Pigment Dispersion 1 for Inkjet Ink: 26.67 parts · Binder resin (JE-1056 manufactured by Starlight PMC, non-volatile content 42.5%): 10.59 parts · Propylene glycol: 23.50 parts · pH adjuster (triethanolamine (pKa = 7.8)): 0.50 part · Ion-exchanged water: 36.50 parts · Hexylamine (molecular weight = 101.19): 0.20 part · Other additives Wetting agent (Tegowet 280 manufactured by EVONIK): 2.00 parts Preservative (Proxel GXL manufactured by SC Johnson): 0.05 part The above materials were mixed in a container equipped with a stirrer for 1 hour. Then, filtration was performed using a membrane filter with a pore size of 1 μm to remove coarse particles, thereby obtaining Aqueous Inkjet Ink 1.

[0064] [Examples 2 to 29, Comparative Examples 1 to 5] <Production of Pigment Dispersions 2 to 34 for Inkjet Ink> As shown in Table 1, except for changing the materials and formulations, Pigment Dispersions 2 to 34 for Inkjet Ink were produced in the same manner as Pigment Dispersion 1 for Inkjet Ink.

[0065] <Production of Aqueous Inkjet Inks 2 to 34> As shown in Table 1, except for changing the materials and formulations, Aqueous Inkjet Inks 2 to 34 were produced in the same manner as Aqueous Inkjet Ink 1.

[0066] <Evaluation 1 to 3: Evaluation of Hue Change over Time of Aqueous Inkjet Ink> After preparing the aqueous inkjet ink, it was stored at 25 °C and 50 °C for 1 week each, resulting in the aqueous inkjet ink stored at 25 °C and the aqueous inkjet ink stored at 50 °C, respectively. Thereafter, the aqueous inkjet ink stored at 25 °C was placed in a transparent colorimetric cell made of glass, and the ink itself was colorimetrically measured using a spectrophotometer (SE7700 manufactured by Nippon Denshoku Industries Co., Ltd.), and the chromaticity (a * 、b * 、L * ) was determined. The conditions were performed with a light source C, a 2° field of view, and reflectance measurement. The aqueous inkjet ink stored at 50 °C was colorimetrically measured in the same manner, and the chromaticity difference between the aqueous inkjet ink stored at 25 °C and the aqueous inkjet ink stored at 50 °C was determined. Then, the absolute value of the chromaticity difference (referred to as the "absolute value of the color difference", Δa *, Δb * , ΔL * (represented by) was calculated and judged according to the following criteria. The results are shown in Table 1. The smaller the absolute value of the color difference, the better the hue stability with less discoloration over time, and it can be evaluated as an ink with excellent properties. If it meets the following evaluation criteria of "5", "4", "3", and "2", it is at a practical level, and if it is "1", it is considered defective.

[0067] (Evaluation 1: Δa * 's evaluation criteria) 5. Δa * is less than 2.5. 4. Δa * is 2.5 or more and less than 5.0. 3. Δa * is 5.0 or more and less than 7.5. 2. Δa * is 7.5 or more and less than 10.0. 1. Δa * is 10.0 or more.

[0068] (Evaluation 2: Δb * 's evaluation criteria) 5. Δb * is less than 2.5. 4. Δb * is 2.5 or more and less than 5.0. 3. Δb * is 5.0 or more and less than 7.5. 2. Δb * is 7.5 or more and less than 10.0. 1. Δb * is 10.0 or more.

[0069] (Evaluation 3: ΔL * 's evaluation criteria) 5. ΔL * is less than 1.0. 4. ΔL * is 1.0 or more and less than 2.0. 3. ΔL * is 2.0 or more and less than 3.0. 2. ΔL * is 3.0 or more and less than 5.0. 1. ΔL* is 5.0 or more.

[0070]

Table 1

[0071]

Table 1

[0072] For Examples 1 to 7, amine (A) was changed to hexylamine, and the types and parts by mass of the isoindoline pigment and the dispersant were changed. Regardless of the types and parts by mass of the isoindoline pigment and the dispersant, a good inkjet ink with suppressed discoloration over time was obtained.

[0073] For Examples 8 to 12, amine (A) was changed to hexylamine, and the part by mass of amine (A) was changed. In the range of 0.5 to 30 parts by mass of amine (A) with respect to 100 parts by mass of the pigment, particularly in the range of 1 to 15 parts by mass of amine (A) with respect to 100 parts by mass of the pigment as shown in Examples 9 to 11, a good inkjet ink with suppressed discoloration over time was obtained.

[0074] For Examples 13 to 28, amine (A) was changed to various amine species. Good results with suppressed discoloration over time were obtained for the primary amines used in Inkjets 13 to 27. In particular, glycine used in Inkjet 20 is an easily available amino acid and has high practicality. For the tertiary amines and sodium hydroxide used in Inkjets 33 and 34 shown in Comparative Examples 4 and 5, the good results obtained with the amine (A) were not obtained.

[0075] The obtained inkjet ink was loaded into an inkjet printer (manufactured by Seiko Epson Corporation, model number: EM-930C, piezo method), and high-quality paper (NPi Form NEXT-IJ manufactured by Nippon Paper Industries Co., Ltd., 64 g / m 2) It was printed on . After printing, it was dried using an oven to obtain a printed matter.

[0076] <Water-based flexographic printing ink>

[0077] The following is an example of a water-based flexographic printing ink, which is one aspect of the printing ink of the present invention.

[0078] [Examples 30 to 32, Comparative Example 6] <Production of water-based flexographic printing inks 1 to 4> A mixture of Pigment 1 or Pigment 2, a dispersant (Joncryl HPD-671, manufactured by BASF Japan, solid content 25%, acid value 214 mgKOH / g), a surfactant (Adekapolonic (registered trademark) L-64, manufactured by ADEKA), ethylene glycol dibutyl ether, and water was kneaded with a bead mill, and then a binder resin (Joncryl 7610, manufactured by BASF Japan, solid content 52%), an antifoaming agent (SN Defoamer 777#C, manufactured by San Nopco), hexylamine (molecular weight = 101.19) or glycine (molecular weight = 75.07) was added and mixed in the ratios shown in Table 2 to obtain water-based flexographic printing inks 1 to 4, respectively.

[0079] <Evaluations 1 to 3: Evaluation of color change over time of water-based flexographic printing ink> After preparing the water-based flexographic printing ink, it was stored at 25°C and 50°C for 1 week each to obtain the water-based flexographic printing ink stored at 25°C and the water-based flexographic printing ink stored at 50°C. Thereafter, the water-based flexographic printing ink stored at 25°C was put into a transparent colorimetric cell made of glass, and the ink itself was colorimetrically measured using a spectrophotometer (SE7700 manufactured by Nippon Denshoku Industries Co., Ltd.) to obtain the chromaticity (a * , b * , L * ). The conditions were light source C, 2° field of view, and reflection measurement. The water-based flexographic printing ink stored at 50°C was colorimetrically measured in the same manner, and the chromaticity difference between the water-based flexographic printing ink stored at 25°C and the water-based flexographic printing ink stored at 50°C was obtained. Next, the absolute value of the chromaticity difference (referred to as "absolute value of color difference", Δa * , Δb * , ΔL *It was calculated (represented by ) and judged according to the following criteria. The results are shown in Table 2. The smaller the absolute value of the color difference, the better the hue stability with suppressed discoloration over time, and it can be evaluated as an ink with excellent properties. If it is "5", "4", "3", or "2" according to the following evaluation criteria, it is at a practical level, and if it is "1", it is defective.

[0080] (Evaluation 1: Δa * 's evaluation criteria) 5. Δa * is less than 2.5. 4. Δa * is 2.5 or more and less than 5.0. 3. Δa * is 5.0 or more and less than 7.5. 2. Δa * is 7.5 or more and less than 10.0. 1. Δa * is 10.0 or more.

[0081] (Evaluation 2: Δb * 's evaluation criteria) 5. Δb * is less than 2.5. 4. Δb * is 2.5 or more and less than 5.0. 3. Δb * is 5.0 or more and less than 7.5. 2. Δb * is 7.5 or more and less than 10.0. 1. Δb * is 10.0 or more.

[0082] (Evaluation 3: ΔL * 's evaluation criteria) 5. ΔL * is less than 1.0. 4. ΔL * is 1.0 or more and less than 2.0. 3. ΔL * is 2.0 or more and less than 3.0. 2. ΔL * is 3.0 or more and less than 5.0. 1. ΔL * is 5.0 or more.

[0083]

Table 2

[0084] For Examples 30 to 32, amine (A) was hexylamine and glycine, and the evaluation was carried out. Similar to the evaluation results of the inkjet ink, a good aqueous flexographic printing ink with suppressed discoloration over time was obtained.

[0085] The obtained aqueous flexographic printing ink was applied to a K-liner (manufactured by Oji Paper Co., Ltd., K) using a 0.15-mm Mayer bar and dried to obtain a printed matter.

Claims

1. A printing ink containing an isoindoline pigment and at least one amine (A) selected from the group consisting of primary amines and secondary amines, wherein the molecular weight of the amine (A) is 1000 or less. However, the amine (A) excludes alkanolamines, amides, and melamines.

2. The printing ink according to Claim 1, wherein the amine (A) is an amine other than an aromatic amine.

3. The printing ink according to Claim 1, wherein the amine (A) is an amino acid or an aliphatic amine.

4. The printing ink according to Claim 1, containing 0.5 to 30 parts by mass of the amine (A) with respect to 100 parts by mass of the isoindoline pigment.

5. A printed matter using the printing ink according to any one of Claims 1 to 4.

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