Active energy ray-curable lithographic printing ink set, method for producing printed matter, and active energy ray-curable lithographic printing ink

Abstract

The object of the present invention is to provide an active energy ray-curable lithographic ink set having excellent ink superposition and a method for producing a printed matter using the same. The present invention is an active energy ray-curable lithographic ink set, comprising: at least one of a black ink and a color ink containing at least one of a black pigment, a blue pigment, a red pigment, and a yellow pigment, and a white ink containing a white pigment, wherein at least one of the black ink and the color ink is a black / color ink (1) having a viscosity value of 5.0 or more and 12.0 or less at 400 rpm measured at 38°C using an ink viscometer, and the viscosity value of the white ink at 400 rpm measured at 38°C using an ink viscometer is 1.0 or more and 5.0 or less.

Description

Technical Field

[0001] The present invention relates to an active energy ray-curable lithographic printing ink set, a method for producing a printed matter, and an active energy ray-curable lithographic printing ink. Background Art

[0002] Lithography is a printing method that has become widely popular as a system for supplying printed materials at high speed, in large quantities, and at low cost. In recent years, active energy ray-curing lithography using light sources such as mercury lamps and metal halide lamps has been widely used in many fields in particular from the perspective of high productivity.

[0003] In the past, lithography was mostly done on paper, but due to the diversification of printing applications, printing on plastic films has become more and more common. In recent years, lithography has also been tried on flexible packaging for daily necessities, food, medical supplies, etc., using films as substrates.

[0004] Active energy ray-curable lithographic ink has a viscosity 100 times higher than that of conventional gravure inks used for flexible packaging printing. Since the ink is instantly cured by irradiation with active energy rays, the ink does not have time to disperse, and tends to easily cause white leakage or unevenness on the surface of the ink film on the printed matter. In contrast, an active energy ray-curable lithographic ink having excellent fluidity is disclosed (Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-83864 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, the ink disclosed in Patent Document 1 tends to have difficulty in achieving both concealment properties and ink superposition properties.

[0010] Therefore, an object of the present invention is to overcome the problems of the related conventional techniques and to provide an active energy ray-curable lithographic printing ink set having high concealability of printed matter and excellent ink superposition during printing, and a method for producing a printed matter using the same.

[0011] Means for solving problems

[0012] The present inventors have come to realize the present invention by noting that if the pigment concentration in ink is increased in order to improve concealment, the viscosity of the ink increases, the pre-printed ink peels off, and the ink superposition becomes poor.

[0013] That is, the present invention is an active energy ray-curable lithographic ink kit, which comprises: at least one of black ink and color ink containing at least one of black pigment, blue pigment, red pigment and yellow pigment, and white ink containing white pigment, wherein at least one of the black ink and color ink is a black / color ink (1) having a viscosity value of 5.0 or more and 12.0 or less at 400 rpm measured by an ink viscometer at 38°C, and the single viscosity value of the white ink at 400 rpm measured by an ink viscometer at 38°C is 1.0 or more and 5.0 or less.

[0014] In addition, the method for manufacturing a printed material of the present invention comprises: a step of applying at least one of the black / color inks (1) to a printed material using the active energy ray-curable printing ink kit of the present invention; a step of applying the white ink to the printed material coated with the black / color ink (1); and a step of curing the ink using active energy rays.

[0015] The present invention is also an active energy ray-curable lithographic ink, comprising a resin (a), a multifunctional (meth)acrylate (b), a white pigment (c), and a monofunctional (meth)acrylate alkyl ester (d), wherein the content of the white pigment (c) is 30% by mass or more and 60% by mass or less relative to 100% by mass of the total amount of the ink, and the viscosity η at a rotation speed of 50 rpm measured at 35° C. using a cone-plate type rotational viscometer is WT50 Viscosity η at a rotation speed of 0.5 rpm WT0.5 The viscosity ratio η WT50 / η WT0.5 The viscosity is 0.7 or more and 1.0 or less, and the viscosity value at 400 rpm measured with an ink viscosity meter at 38° C. is 1.0 or more and 5.0 or less.

[0016] Effects of the Invention

[0017] According to the present invention, it is possible to provide an active energy ray-curable lithographic printing ink set which has high concealability of printed matter and is excellent in ink superposition during printing. DETAILED DESCRIPTION

[0018] The following describes in detail the active energy ray-curable lithographic ink set (hereinafter referred to as "ink set") and the method for producing printed matter according to the present invention. However, the present invention is not limited to the following embodiments and can be implemented with various modifications according to the purpose and application.

[0019] In the present invention, "above" means a value that is the same as or greater than the numerical value shown. In addition, "below" means a value that is the same as or less than the numerical value shown.

[0020] The ink set of the present invention comprises: at least one of black ink and color ink containing at least one of black pigment, blue pigment, red pigment, and yellow pigment; and white ink containing white pigment. Generally, the color tone of printed matter is expressed by combining black, blue, red, yellow, and white. The ink set of the present invention achieves excellent effects in the interaction between black ink or color ink and white ink.

[0021] [pigment]

[0022] The black ink or color ink in the ink set of the present invention contains a pigment, and one or more selected from organic pigments and inorganic pigments can be used.

[0023] Specific examples of organic pigments include phthalocyanine pigments, soluble azo pigments, insoluble azo pigments, lake pigments, quinacridone pigments, isoindolinone pigments, reduced (Shilin) ​​pigments, and metal complex pigments. Specific examples include phthalocyanine blue, phthalocyanine green, azo red, monoazo red, monoazo yellow, disazo red, disazo yellow, quinacridone red, quinacridone magenta, and isoindolinone yellow.

[0024] Examples of the inorganic pigment include titanium oxide, zinc oxide, alumina white, calcium carbonate, barium sulfate, red iron, cadmium red, chrome yellow, zinc yellow, Prussian blue, ultramarine, oxide-coated glass powder, oxide-coated mica, oxide-coated metal particles, aluminum powder, gold powder, silver powder, copper powder, bronze powder, zinc powder, stainless steel powder, nickel powder, organic bentonite, iron oxide, carbon black, and graphite.

[0025] The concentration of the pigment contained in the black ink or color ink in the ink set of the present invention is preferably 5% by mass or more. By setting it to 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more, a printed matter with a high printing paper density can be obtained.

[0026] In addition, the concentration of the pigment contained in the black ink or the color ink is preferably 50% by mass or less. By setting it to 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less, the fluidity of the ink can be improved and good transferability can be obtained.

[0027] [White pigment (c)]

[0028] The white ink in the ink set of the present invention contains a white pigment (c). As the white pigment (c), one or more selected from organic pigments and inorganic pigments commonly used in printing ink compositions can be used. Specific examples of the white pigment (c) include titanium oxide, zinc oxide, alumina white, lead carbonate, barium sulfate, zinc sulfate, calcium carbonate, etc. From the viewpoint of forming the background color of the transparent plastic film, titanium dioxide that imparts concealment to the ink is particularly preferred.

[0029] When titanium dioxide is used as the white pigment (c), the particle size is preferably 200 nm or more and 300 nm or less. Within this range, the transmittance of visible light can be reduced favorably by the scattering effect.

[0030] The content of the white pigment (c) is preferably 30% by mass or more relative to 100% by mass of the total amount of the white ink. By setting it to 30% by mass or more, more preferably 35% by mass or more, and further preferably 40% by mass or more, concealment properties are improved.

[0031] The content of the white pigment (c) is preferably 60% by mass or less relative to 100% by mass of the total amount of the white ink. By setting it to 60% by mass or less, more preferably 55% by mass or less, and further preferably 50% by mass or less, the fluidity of the white ink is improved.

[0032] [Resin (a)]

[0033] The ink in the ink set of the present invention preferably contains resin (a). By containing resin (a), the cohesive force of the ink under high shear during printing can be improved. If the cohesive force of the ink becomes higher, the ink repellency to the non-image area is improved, and as a result, the resistance to plate smearing is improved. It should be noted that plate smearing refers to the phenomenon that the non-image area of ​​the plate is printed on the printed object in a state where the ink is stuck to the non-image area of ​​the plate and becomes a stain.

[0034] Examples of the resin (a) contained in the ink include acrylic resins, styrene acrylic resins, styrene maleic acid resins, rosin-modified maleic acid resins, rosin-modified acrylic resins, epoxy resins, polyester resins, polyurethane resins, phenolic resins, etc. Among them, acrylic resins, styrene acrylic resins, and styrene maleic acid resins are preferred from the viewpoints of easy availability of monomers, low cost, ease of synthesis, compatibility with other components of the ink, dispersibility of the pigment, etc.

[0035] The weight average molecular weight of the resin (a) contained in the ink is preferably 5,000 or more. When the weight average molecular weight is 5,000 or more, more preferably 15,000 or more, and even more preferably 20,000 or more, the anti-smearing property is improved.

[0036] The weight average molecular weight of the resin (a) contained in the ink is preferably 100,000 or less. By setting the weight average molecular weight to 100,000 or less, more preferably 75,000 or less, and even more preferably 50,000 or less, the fluidity of the ink can be maintained.

[0037] The weight average molecular weight of the resin (a) can be obtained by measuring in terms of polystyrene using gel permeation chromatography (GPC).

[0038] The resin (a) contained in the ink preferably contains a hydrophilic group. The ink contains the resin (a) containing a hydrophilic group, so that the dispersibility of the pigment is excellent. In addition, the ink can be effectively close to the Newtonian fluid described later. As the hydrophilic group, for example, hydroxyl, amino, sulfhydryl, carboxyl, sulfo, phosphoric acid, etc. can be preferably listed. Among them, carboxyl, hydroxyl with good dispersibility of the pigment are more preferred, and at least one of carboxyl and hydroxyl is particularly preferred.

[0039] Specific examples of the resin containing a hydrophilic group include (meth)acrylic acid copolymers, (meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, styrene-maleic acid-(meth)acrylic acid copolymers, styrene-maleic acid-(meth)acrylic acid ester copolymers, etc. It should be noted that "(meth)acrylic acid" is a general term including acrylic acid and methacrylic acid.

[0040] The acid value of the resin (a) contained in the ink is preferably 30 mgKOH / g or more. By setting it to 30 mgKOH / g or more, more preferably 60 mgKOH / g or more, and further preferably 75 mgKOH / g or more, the pigment dispersibility of the ink becomes good and the anti-plate smearing property is improved.

[0041] The acid value of the resin (a) contained in the ink is preferably 250 mgKOH / g or less. By setting the acid value to 250 mgKOH / g or less, more preferably 230 mgKOH / g or less, and further preferably 200 mgKOH / g or less, good solubility in the multifunctional (meth)acrylate described later can be exhibited, and the fluidity of the ink can be maintained by suppressing the increase in viscosity caused by polar groups.

[0042] The acid value of the resin (a) can be determined by the neutralization titration method in accordance with the test method 3.1 of JIS K 0070:1992.

[0043] The resin (a) contained in the ink preferably has an ethylenically unsaturated double bond group. The ethylenically unsaturated double bond group reacts with radical species to form a crosslinked structure, thereby improving the sensitivity of the ink in the ink set of the present invention to active energy rays.

[0044] The iodine value of the resin (a) contained in the ink is preferably 0.5 mol / kg or more. By setting it to 0.5 mol / kg or more, more preferably 1.0 mol / kg or more, and further preferably 1.5 mol / kg or more, the curing sensitivity of the ink to active energy rays becomes good.

[0045] The iodine value of the resin (a) contained in the ink is preferably 3.0 mol / kg or less. By setting the iodine value to 3.0 mol / kg or less, more preferably 2.5 mol / kg or less, and even more preferably 2.0 mol / kg or less, the storage stability of the ink is improved.

[0046] The iodine value of the resin (a) can be adjusted by the amount of the ethylenically unsaturated double bond groups. The iodine value of the resin can be determined by the method described in Item 6 of JIS K0070:1992.

[0047] The black ink or color ink in the ink set of the present invention preferably contains 5% by mass or more of the resin (a) relative to 100% by mass of the total amount of the color ink. By containing 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, the ink has improved anti-plate smearing properties.

[0048] In addition, the content of the resin (a) in the black ink or the color ink is preferably 50% by mass or less relative to the total amount 100% by mass of the color ink. By setting it to 50% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less, the pigment dispersibility and fluidity of the ink can be well maintained.

[0049] The white ink in the ink set of the present invention preferably contains 3% by mass or more of the resin (a) relative to 100% by mass of the total amount of the white ink. By containing 3% by mass or more, more preferably 4% by mass or more, and further preferably 5% by mass or more, the ink has improved anti-plate smearing properties.

[0050] In addition, the content of the resin (a) in the white ink is preferably 20% by mass or less relative to the total amount of the ink (100% by mass). By setting it to 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less, the pigment dispersibility and fluidity of the ink can be well maintained.

[0051] [Multifunctional (meth)acrylate (b)]

[0052] The ink in the ink set of the present invention preferably contains a multifunctional (meth)acrylate (b). When the ink contains a multifunctional (meth)acrylate, the sensitivity of the active energy ray-curable ink to the active energy ray becomes higher, and the adhesion to the printed object is improved. It should be noted that the functional number here refers to the number of (meth)acryloyl groups.

[0053] Specific examples of the polyfunctional (meth)acrylate (b) contained in the ink include 1,4-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, dicyclopentadiene tricyclodecane dimethanol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and alkylene oxide adducts thereof. Among them, 1,10-decanediol di(meth)acrylate and tricyclodecane dimethanol di(meth)acrylate are particularly preferred because of their suitable compatibility with the resin (a) contained in the ink and excellent balance with the reduction of the viscosity value.

[0054] Since the pigment dispersibility of the ink and the adhesion to the printed object are improved, it is preferred that the multifunctional (meth)acrylate (b) contained in the ink contains a hydroxyl group. As the multifunctional (meth)acrylate containing a hydroxyl group, specifically, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol di(meth)acrylate, diglycerol tri(meth)acrylate, diglycerol tetra(meth)acrylate, 2-hydroxy-3-acryloxypropyl (meth)acrylate, etc., and their alkylene oxide adducts can be cited. Among them, pentaerythritol tri(meth)acrylate is particularly preferred because it obtains good compatibility with the resin (a) and can give the ink a suitable viscosity.

[0055] The content of the multifunctional (meth)acrylate (b) in the ink is preferably 20% by mass or more. When the ink contains 20% by mass or more, more preferably 40% by mass or more of the multifunctional (meth)acrylate (b), good compatibility with the resin (a) can be obtained. In addition, when the content is 90% by mass or less, more preferably 70% by mass or less, the viscosity of the ink can be adjusted to obtain good fluidity.

[0056] [Monofunctional alkyl (meth)acrylate (d)]

[0057] The white ink in the ink set of the present invention preferably contains a monofunctional (meth) alkyl acrylate (d). Although high concealment is generally required for white ink, if a high concentration of pigment is contained in the ink in order to improve concealment, the viscosity value of the ink increases, and the pre-printed ink will peel off, and the superposition of the ink will become poor. In addition, generally speaking, as a method of reducing the viscosity value, it is known to reduce the resin concentration in the ink, or add silicone liquid, etc. However, if the resin concentration in the ink is reduced, the cohesive force of the ink decreases and the ink's resistance to smearing decreases; if silicone liquid is added, there are difficulties such as the formation of a film of silicone liquid on the surface of the ink and the reduction of the transferability of the ink between rollers, which produces poor printing. In contrast to these, by containing a monofunctional (meth) alkyl acrylate (d) in the white ink, the same additive acts as an incompatible component, and can become the starting point of cracking in the layer of the white ink without reducing the cohesive force of the ink and separating the components that are not needed in printing. That is, the viscosity value of the white ink can be effectively reduced while suppressing the above-mentioned printing defects.

[0058] Specific examples of the monofunctional (meth) alkyl acrylate (d) contained in the white ink include (iso)nonyl (meth)acrylate, (iso)decyl (meth)acrylate, (iso)undecyl (meth)acrylate, (iso)dodecyl (meth)acrylate, (iso)tridecyl (meth)acrylate, (iso)tetradecyl (meth)acrylate, (iso)pentadecyl (meth)acrylate, (iso)hexadecyl (meth)acrylate, (iso)heptadecyl (meth)acrylate, (iso)octadecyl (meth)acrylate, (iso)nonadecyl (meth)acrylate, (iso)eicosyl (meth)acrylate, (iso)henedecyl (meth)acrylate, (iso)docosyl (meth)acrylate, etc. The number of carbon atoms in the alkyl group of the monofunctional (meth) alkyl acrylate (d) is preferably 12 to 20. Among them, (iso)octadecyl (meth)acrylate is particularly preferred in that the viscosity of the white ink is greatly reduced.

[0059] The content of the monofunctional alkyl (meth)acrylate (d) in the white ink is preferably 1.0% by mass or more relative to 100% by mass of the total amount of the ink, because the viscosity of the white ink can be reduced. By setting the content of the monofunctional alkyl (meth)acrylate (d) to 1.0% by mass or more, more preferably 2.0% by mass or more, the viscosity of the white ink can be effectively reduced.

[0060] In addition, the content of the monofunctional (meth) alkyl acrylate (d) in the white ink is preferably 5.0% by mass or less relative to 100% by mass of the total amount of the ink. By setting the content of the monofunctional (meth) alkyl acrylate (d) to 5.0% by mass or less, more preferably to 4.0% by mass or less, the temporal stability of the white ink can be ensured.

[0061] [Sugaryl carboxylate (e)]

[0062] The white ink in the ink set of the present invention preferably contains a glycosyl carboxylate (e). The glycosyl carboxylate (e) is formed from a sugar and a carboxylic acid. By containing the glycosyl carboxylate (e), the smear resistance of the white ink can be improved.

[0063] Specific examples of the sugar-based carboxylates (e) include sucrose laurate, sucrose myristate, sucrose palmitate, sucrose stearate, sucrose oleate, sucrose behenate, sucrose erucate, sucrose acetate, sucrose benzoate, cellulose acetate, cellulose glycolate, cellulose nitrate, and the like. Among them, sucrose benzoate and sucrose acetate are particularly preferred from the perspective of obtaining good compatibility with the multifunctional (meth)acrylate (b).

[0064] The content of the glycosyl carboxylate (e) in the white ink is preferably 1.0% by mass or more relative to 100% by mass of the total amount of the ink. By setting the content of the glycosyl carboxylate (e) to 1.0% by mass or more, more preferably to 2.0% by mass or more, the smear resistance of the white ink can be effectively improved.

[0065] The content of the glycosyl carboxylate in the white ink is preferably 10.0% by mass or less relative to 100% by mass of the total ink amount. By setting the content of the glycosyl carboxylate (e) to 10.0% by mass or less, more preferably 5.0% by mass or less, the fluidity of the white ink can be maintained.

[0066] [Polymerization inhibitor]

[0067] The ink in the ink set of the present invention preferably contains a polymerization inhibitor. By containing a polymerization inhibitor, good storage stability of the ink can be obtained.

[0068] Specific examples of the polymerization inhibitor include hydroquinone, monoesters of hydroquinone, N-nitrosodiphenylamine, phenothiazine, p-tert-butylcatechol, N-phenylnaphthylamine, 2,6-di-tert-butyl-p-methylphenol, chloranil, and pyrogallol.

[0069] The content of the polymerization inhibitor in the ink is preferably 0.001% by mass or more. When the ink contains 0.001% by mass or more of the polymerization inhibitor, good storage stability can be effectively obtained.

[0070] The content of the polymerization inhibitor in the ink is preferably 5% by mass or less. By setting the content of the polymerization inhibitor in the ink to 5% by mass or less, good sensitivity can be maintained.

[0071] [Pigment dispersant]

[0072] The ink in the ink set of the present invention preferably contains a pigment dispersant. The pigment dispersant acts on the surface of the pigment and inhibits the aggregation of the pigment. This can improve the dispersibility of the pigment and improve the fluidity of the ink.

[0073] The content of the pigment dispersant is preferably 5 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the pigment. By setting the content within this range, the fluidity of the ink can be effectively improved.

[0074] [Other additives]

[0075] The ink in the ink set of the present invention may contain other additives such as a photoinitiator, a surfactant, a wax, a defoaming agent, a transferability improving agent, and a leveling agent.

[0076] [stickiness value]

[0077] The viscosity value of at least one of the black ink and the color ink in the ink set of the present invention is 5.0 or more and 12.0 or less (hereinafter, the black ink or the color ink satisfying this requirement is also referred to as "black / chromatic ink (1)"). In addition, for all types of black ink and color ink in the ink set, it is preferred that the viscosity value corresponds to the black / chromatic ink (1) having a viscosity value of 5.0 or more and 12.0 or less.

[0078] In the present invention, the viscosity value is based on the test method 4.2 of JIS K5701-1:2000, and 1.31 mL of ink weighed with an ink pipette is measured using an ink viscometer at a rotation speed of 400 rpm and an apparatus temperature of 38° C., and the measured value 1 minute after the start of the measurement is used as the viscosity value used in the present invention. The viscosity value is an index indicating the viscosity of the ink, and a higher viscosity value indicates a higher viscosity of the ink.

[0079] By setting the viscosity value of black ink or color ink to 5.0 or more, preferably 5.5 or more, and more preferably 6.0 or more, it is possible to effectively prevent backtrapping of black ink or color ink used as preprint ink. Backtrapping refers to the phenomenon that the bottom layer ink first transferred to the printed material is peeled off by the back-print ink. If backtrapping occurs, the target pattern cannot be obtained and the printed material is unclear, or the back-print ink and the preprint ink are mixed and the color tone of the printed material changes at the beginning and end of printing, resulting in printing defects.

[0080] If the viscosity value of the black ink or the color ink is less than 5.0, the physical properties of the ink become unstable due to color mixing, resulting in plate blurring.

[0081] In addition, if the viscosity value is high, the surface of the ink transferred to the printed object is easily uneven, and the gloss of the printed object is reduced. In particular, in the printed part of the multi-color superposition, if the surface of the black ink or color ink as the bottom ink is uneven, the gloss is further reduced due to the influence. By setting the viscosity value of the black ink or color ink to 12.0 or less, more preferably to 9.0 or less, and more preferably to 8.5 or less, the reduction of the gloss of the printed part of the multi-color superposition can be suppressed.

[0082] Furthermore, when printing two or more types of black ink and color ink, it is preferable to reduce the viscosity value according to the order in which printing is performed in order to prevent reverse tracking.

[0083] The viscosity of the white ink in the ink set of the present invention is 1.0 or more and 5.0 or less. By setting the viscosity of the white ink to 5.0 or less, preferably 4.5 or less, and more preferably 4.0 or less, reverse overprinting can be suppressed even when the white ink is transferred onto pre-printed black ink or color ink.

[0084] In addition, by setting the viscosity value of the white ink to 1.0 or more, preferably 2.0 or more, and more preferably 2.5 or more, it is possible to suppress the reduction of the cohesive force of the ink and improve the anti-plate smearing property of the ink. In addition, it is possible to suppress the addition of the silicone liquid from becoming excessive, suppress the silicone liquid from forming a film on the surface of the ink, and suppress the reduction of the transferability of the ink between rollers.

[0085] The viscosity can be adjusted by the resin concentration in the ink. In addition, the viscosity can be reduced by adding silicone liquid.

[0086] In the ink set of the present invention, the difference in viscosity between at least one of the black / color inks (1) and the white ink is preferably 2.0 or more and 8.0 or less. In addition, all types of black ink and color inks are equivalent to the black / color ink (1), and the difference between all of the black / color inks (1) and the white ink is more preferably 2.0 or more and 8.0 or less. By setting the difference to be greater than 2.0, more preferably greater than 2.5, and further preferably greater than 3.0, reverse overprinting can be effectively prevented. In addition, by setting it to be less than 8.0, more preferably less than 7.5, and further preferably less than 7.0, the viscosity of the preprinted ink can be prevented from becoming higher and the gloss of the print from decreasing.

[0087] [Viscosity]

[0088] In the ink set of the present invention, the viscosity η of the white ink at 35°C at a rotation speed of 0.5 rpm measured by a cone-plate type rotational viscometer is WT0.5 It is preferably less than 30 Pa·s. WT0.5 By setting the viscosity to 30 Pa·s or less, more preferably 25 Pa·s or less, and still more preferably 20 Pa·s or less, the fluidity of the white ink can be improved, the leveling property on the printed matter can be improved, and the concealing property can be improved.

[0089] In addition, η WT0.5 It is preferably 5Pa·s or more. WT0.5 When the pressure is 5 Pa·s or more, good ink transferability between rollers can be obtained.

[0090] In the ink set of the present invention, the viscosity η of the white ink at 35°C and at a rotation speed of 50 rpm measured by a cone-plate type rotational viscometer is WT50 It is preferably less than 20 Pa·s. WT50 When the viscosity is 20 Pa·s or less, the ink can have good fluidity.

[0091] In addition, η WT50 It is preferably 5Pa·s or more. WT50 When the viscosity is 5 Pa·s or more, more preferably 8 Pa·s or more, and further preferably 10 Pa·s or more, the smear resistance of the white ink is improved.

[0092] In the ink set of the present invention, the viscosity η of the white ink at 35°C and at a rotation speed of 50 rpm measured by a cone-plate type rotational viscometer is WT50 Viscosity η at a rotation speed of 0.5 rpm WT0.5 The ratio η WT50 / η WT0.5 It is preferably greater than or equal to 0.70 and less than or equal to 1.00. WT50 / η WT0.5By setting the viscosity to be between 0.70 and 1.00, more preferably between 0.75 and 1.00, and further preferably between 0.80 and 1.00, the white ink can be close to a Newtonian fluid and can maintain a certain viscosity regardless of the shear intensity. Generally, when high shear is applied during printing, the structural viscosity of the ink composition collapses and the viscosity decreases, but the white ink in the preferred embodiment of the present invention has a small decrease in viscosity due to shear, and maintains a high viscosity under high shear. As a result, under such high shear during printing, the cohesive force of the ink increases, and the ink repellency to the non-line portion is improved, so the anti-smearing property is improved.

[0093] In the ink set of the present invention, the viscosity η of at least one of the black ink and the color ink measured at 35°C with a cone-plate type rotational viscometer at a rotation speed of 0.5 rpm is BC0.5 It is preferably less than 200 Pa·s. BC0.5 By setting it to 200 Pa·s or less, more preferably 150 Pa·s or less, and further preferably 100 Pa·s or less, the black ink or color ink can have good fluidity, and the leveling property on the printed matter can be improved, thereby improving the concealment property.

[0094] In addition, η BC0.5 It is preferably 20Pa·s or more. BC0.5 When the pressure is 20 Pa·s or more, good ink transfer properties between rollers can be obtained.

[0095] In the ink set of the present invention, the viscosity η of at least one of the black ink and the color ink measured at 35°C with a cone-plate type rotational viscometer at a rotation speed of 50 rpm is BC50 It is preferably less than 50 Pa·s. BC50 By setting the pressure to 50 Pa·s or less, the ink can have good fluidity.

[0096] In addition, η BC50 It is preferably 5Pa·s or more. BC50 By setting the viscosity to 5 Pa·s or more, more preferably to 10 Pa·s or more, and still more preferably to 15 Pa·s or more, the smear resistance of the black ink and the color inks can be improved.

[0097] In the ink set of the present invention, the viscosity η of at least one of the black ink and the color ink measured at 35°C with a cone-plate type rotational viscometer at a rotation speed of 50 rpm is BC50 Viscosity η at a rotation speed of 0.5 rpm BC0.5 The ratio η BC50 / η BC0.5 It is preferably 0.25 or more and 0.6 or less. BC50 / ηBC0.5 By setting the viscosity to be greater than 0.30 and less than 0.55, and more preferably greater than 0.35 and less than 0.50, the ink is close to a Newtonian fluid and can maintain a certain viscosity regardless of the shear strength. Generally, when high shear is applied during printing, the structural viscosity of the ink composition collapses and the viscosity decreases, but the black ink and color ink in the preferred embodiment of the present invention have a small viscosity drop due to shear, and maintain a high viscosity under high shear, and as a result, under high shear such as during printing, the cohesive force of the ink is high, and the ink repellency to the non-line portion is improved, so the resistance to smearing is improved.

[0098] The active energy ray-curable lithographic printing ink of the present invention comprises a resin (a), a multifunctional (meth)acrylate (b), a white pigment (c), and a monofunctional (meth)acrylate alkyl ester (d), wherein the content of the white pigment (c) is 30% by mass or more and 60% by mass or less relative to 100% by mass of the total amount of the ink, and the viscosity η at a rotation speed of 50 rpm measured at 35° C. using a cone-plate type rotational viscometer is WT50 Viscosity η at a rotation speed of 0.5 rpm WT0.5 The ratio η WT50 / η WT0.5 The viscosity is 0.7 or more and 1.0 or less, and the viscosity value at 400 rpm measured at 38° C. with an ink viscosity meter is 1.0 or more and 5.0 or less.

[0099] The technical significance, form, amount, and control means of the resin (a), multifunctional (meth)acrylate (b), inhibitor, pigment dispersant, and other additives in the energy-ray-curable lithographic ink of the present invention may be the same as those described in the description of the ink in the ink set of the present invention.

[0100] In addition, in the active energy ray-curable lithographic ink of the present invention, the content of the resin (a), the white pigment (c), the monofunctional (meth) alkyl acrylate (d), the glycosyl carboxylate (e), the viscosity value, and the technical significance, method, amount, and control means of the viscosity can be the same as those described in the description of the white ink in the ink kit of the present invention.

[0101] The method for manufacturing the ink in the ink set of the present invention and the active energy ray-curable lithographic ink of the present invention (hereinafter collectively referred to as "the ink involved in the present invention") is described below. However, the ink in the ink set of the present invention and the active energy ray-curable lithographic ink of the present invention are not limited to those manufactured by the method shown below.

[0102] The resin having a main chain structure derived from a resin selected from acrylic resin, styrene acrylic resin, and styrene maleic acid resin and having an ethylenically unsaturated double bond group and a hydrophilic group in the resin (a) can be prepared by the following method. That is, a compound selected from (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetate, or anhydrides thereof, a hydroxyl group-containing monomer such as (meth)acrylic acid 2-hydroxyethyl ester, an amino group-containing monomer such as dimethylaminoethyl (meth)acrylate, a mercapto group-containing monomer such as (meth)acrylic acid 2-(mercaptoacetoxy)ethyl ester, a sulfonic group-containing monomer such as (meth)acrylic acid amide tert-butyl sulfonic acid, a phosphoric acid group-containing monomer such as 2-(meth)acryloyloxyethyl acid phosphate, (meth)acrylic acid ester, styrene, (meth)acrylonitrile, vinyl acetate, etc., is polymerized or copolymerized using a free radical polymerization initiator to obtain a resin having a hydrophilic group. Furthermore, the mercapto group, amino group, hydroxyl group and carboxyl group, which are active hydrogen-containing groups in the resin having a hydrophilic group, are subjected to an addition reaction with an ethylenically unsaturated compound having a glycidyl group or an isocyanate group, acryloyl chloride, methacryloyl chloride or acryloyl chloride, thereby obtaining a resin having an ethylenically unsaturated double bond group and a hydrophilic group.

[0103] Moreover, as a specific example of the ethylenically unsaturated compound which has a glycidyl group, glycidyl (meth)acrylate, allyl glycidyl ether, glycidyl crotonate, glycidyl isocrotonate, etc. are mentioned.

[0104] Moreover, as a specific example of the ethylenically unsaturated compound which has an isocyanate group, (meth)acryloyl isocyanate, (meth)acryloyl ethyl isocyanate, etc. are mentioned.

[0105] The ink of the present invention is obtained by heating and dissolving resin, multifunctional (meth)acrylate, pigment and other components at 5 to 100° C. as required, and then uniformly mixing and dispersing them with a stirring and kneading machine such as a kneader, a three-roll mill, a ball mill, a planetary ball mill, a bead mill, a roller mill, a pulverizer, a sand mill, a gate mixer, a paint mixer, a homogenizer, a rotary mixer, etc. After mixing and dispersing or during mixing and dispersing, degassing is preferably performed under vacuum or reduced pressure conditions.

[0106] The method for manufacturing a printed material of the present invention comprises: a step of applying at least one of the black / color inks (1) to a printed material using the active energy ray-curable printing ink kit of the present invention; a step of applying the white ink to the printed material coated with the black / color ink (1); and a step of curing the ink using active energy rays.

[0107] Examples of the printed material include art paper, coated paper, cast-coated paper, synthetic paper, newspaper paper, aluminum-deposited paper, metal, and plastic film.

[0108] A preferred embodiment of the ink of the present invention also has excellent transferability and adhesion to plastic films. Examples of plastic films include polyethylene terephthalate, polyethylene, polyester, polyamide, polyimide, polystyrene, polypropylene, polycarbonate, and polyvinyl acetal.

[0109] In addition, as the plastic film, in addition to the plastic film itself, there can be cited plastic film laminated paper obtained by laminating a plastic film on paper, and metal-deposited plastic film in which a metal such as aluminum, zinc, copper, etc. is vapor-deposited on plastic, but the present invention is suitable for bottom printing, so a transparent film is particularly preferred. As the transparent film, any one selected from polyamide film, polyester film, polystyrene film, polyethylene film, and polypropylene film is preferred.

[0110] Furthermore, it is preferred that the plastic film be subjected to a surface treatment to impart good adhesion, for example, coating with a primer resin, corona discharge treatment, or plasma treatment.

[0111] As a method for applying ink to a printed object in the method for producing a printed object of the present invention, for example, flexographic printing, offset printing (lithographic printing), gravure printing, screen printing, rod coating, etc. Lithographic printing is particularly preferred, and as a method of lithographic printing, there are water-based printing and waterless printing, but waterless lithographic printing is more preferred.

[0112] In the method for producing a printed matter of the present invention, in order to prevent the above-mentioned reverse overprinting, it is preferred that the viscosity value be lowered according to the order of printing, and the white ink is preferably printed last.

[0113] In the method for producing printed matter of the present invention, it is preferred that the step of applying white ink is included twice or more. In that case, even in the case where white ink is printed as the base color of a transparent plastic film, the concealment property is improved.

[0114] In the method for producing a printed article of the present invention, the surface roughness (Ra) of the surface applied with the white ink is preferably 0.1 μm or more and 2.0 μm or less. Within this range, reverse overprinting can be effectively prevented.

[0115] The ink involved in the present invention can cure the ink coating on the printed material instantly by irradiating the active energy ray. In addition, the method for producing the printed material of the present invention comprises a step of curing the ink applied to the printed material using the active energy ray. As the active energy ray, a ray having the necessary excitation energy for the curing reaction can be used, for example, ultraviolet rays or electron rays can be preferably used. Among them, electron rays are more preferred from the viewpoint of curing sensitivity.

[0116] When curing by electron beam, it is preferable to use an electron beam device with an energy beam of 100 to 500 eV. As the absorbed dose of the printed matter, it is preferable to use 10 kGy or more, which has good curing sensitivity of the ink. In addition, it is preferable to use 70 kGy or less, which has little effect on the printed matter.

[0117] When curing by ultraviolet rays, it is preferable to use ultraviolet irradiation devices such as high pressure mercury lamps, xenon lamps, metal halide lamps, and light emitting diodes. Among them, light emitting diodes emitting bright lines with a wavelength of 350 to 420 nm are preferably used from the viewpoint of power saving and cost reduction.

[0118] Example

[0119] The present invention will be described in more detail below by way of examples, but the present invention is not limited thereto.

[0120] [Measurement and evaluation methods, treatment methods]

[0121] (1) Weight average molecular weight

[0122] The weight average molecular weight of the resin was measured by gel permeation chromatography (GPC) using tetrahydrofuran as a mobile phase. The resin was fractionated using a Shodex KF-803 column, and the weight average molecular weight was calculated using a polystyrene-based calibration curve.

[0123] (2) Ink viscosity

[0124] The measurement was performed based on 4.2 of JIS K5701-1 (2000). 1.31 mL of ink weighed with an ink pipette was measured using an ink viscometer ("INKO-GRAPH" TYPE V manufactured by Tester Industries, Ltd.) at a rotation speed of 400 rpm and 38° C. The measured value 1 minute after the start of the measurement was taken as the viscosity value in the present invention.

[0125] In addition, in each embodiment and comparative example (each ink kit), the minimum difference value and the maximum difference value among the viscosity values ​​of black ink, blue ink, red ink, yellow ink and white ink are shown in the table in the form of "minimum value of viscosity value difference - maximum value of viscosity value difference".

[0126] (3) Ink viscosity

[0127] A rheometer (MCR301 manufactured by Anton Paar) was equipped with a cone plate (cone angle 1°, φ=40 mm), and the viscosity of 0.35 ml of white ink weighed with an ink pipette was measured at 35° C., 0.5 rpm and 50 rpm.

[0128] (4) Waterless printing

[0129] A waterless offset printing plate (TAC-VG5, manufactured by Toray Industries, Ltd.) was installed on an offset rotary printing press (CI-8, manufactured by COMEXI, Inc.) consisting of 8 rollers. The ink specified in each embodiment and comparative example was printed on a polyester film (PTM12 manufactured by Unichika Co., Ltd.) with a thickness of 12 μm. A test pattern (175 lines of 1% to 50% dots, 30 μm wide thin lines, 120 μm diameter independent dots, 300 μm wide dotted lines, and solid parts) was printed on the back side with a printing temperature of 30°C, a printing speed of 200 m / min, and an ink supply of 50%. The printed material was then cured by irradiating with electron beams at an acceleration voltage of 110 kV and a radiation dose of 30 kGy to obtain a printed material.

[0130] It is to be noted that in each embodiment and comparative example, black ink is used on the first roller of the above-mentioned printing press, blue ink is used on the second roller, red ink is used on the third roller, yellow ink is used on the fourth roller, white ink is used on the sixth roller, and the second white ink is used on the seventh roller (refer to Example 10).

[0131] (5) Surface roughness of printed material

[0132] The exposed surface of the cured ink in the white solid portion of the printed material obtained by the printing method (4) was measured for arithmetic mean roughness Ra defined in JIS B0601 (2013) using a laser microscope (VK9700 manufactured by Keyence).

[0133] (6) Reverse overprinting

[0134] The reflection density of the solid parts printed with only the single colors of black ink, blue ink, red ink, and yellow ink, and the solid parts printed with each single color and white ink in sequence, as viewed from the printed display side, i.e., the film side, in the test pattern obtained by printing in the above (4) is measured using a reflection densitometer ("Spectro Eye" manufactured by Gretag Macbeth) with high-quality paper as the reference (reflection density 0). The data with the largest reflection density difference among black, blue, red, and yellow are used as evaluation data, and the evaluation is performed based on the following criteria. The smaller the reflection density difference, the more the reverse overprinting caused by the white ink can be suppressed.

[0135] C (poor): The difference in reflection density is larger than 0.3.

[0136] B (good): The difference in reflection density is 0.3 or less.

[0137] A (excellent): The reflection density difference is 0.2 or less.

[0138] AA (extremely excellent): The difference in reflection density is 0.1 or less.

[0139] (7) Concealment

[0140] The concealment property of the solid white portion of the test pattern obtained by printing in the above (4) was evaluated. The printed material to be evaluated was placed on a concealment test paper ("BYK-Chemie" manufactured by BYK-Chemie) so that the printed display side, i.e., the film side, was the surface side, and the concealment rate was measured using a reflection densitometer ("SpectroEye" manufactured by GretagMacbeth), and the evaluation was performed based on the following criteria.

[0141] C (poor): The concealment rate is less than 35%.

[0142] B (good): The concealment rate is 35% or more.

[0143] A (excellent): The concealment rate is 45% or more.

[0144] AA (excellent): The concealment rate is 55% or more.

[0145] (8) Anti-smearing

[0146] The test pattern was printed by the printing method of (4) above. However, for white ink, the ink supply was adjusted so that the concealment rate of the white solid part was 65%. The white density in the non-line portion adjacent to the white solid part of the test pattern was measured using a reflection densitometer (Gretag Macbeth, Spectro Eye) with the reference set to black paper (dark color paper black sold by Marubeni Paper Parp Co., Ltd.) and evaluated using the following reference.

[0147] C (poor): The reflection density exceeds 0.20.

[0148] B (good): The reflection density is 0.20 or less.

[0149] A (excellent): reflection density is 0.10 or less.

[0150] AA (extremely excellent): reflection density is 0.05 or less.

[0151] <Ink Materials>

[0152] [Resin (a)]

[0153] Resin 1: 0.6 equivalent of glycidyl methacrylate was added to the carboxyl group of a copolymer composed of 25% by mass of methyl methacrylate, 25% by mass of styrene, and 50% by mass of methacrylic acid to obtain a resin 1 having an ethylenically unsaturated double bond group and a hydrophilic group. The obtained resin 1 had a weight average molecular weight of 34,000, an acid value of 102 mgKOH / g, and an iodine value of 2.0 mol / kg.

[0154] [Multifunctional (meth)acrylate (b)]

[0155] (b) 1: A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate "Miramer" (registered trademark) M340 (manufactured by MIWON Co., Ltd.)

[0156] (b) 2: Tricyclodecane dimethanol diacrylate "Miramer" (registered trademark) M262 (manufactured by MIWON Co., Ltd.)

[0157] (b) 3: 1,10-Decanediol diacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., NK Ester A-DOD-N).

[0158] [Monofunctional alkyl (meth)acrylate (d)]

[0159] (d) 1: Isodecyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Carbon number: 10

[0160] (d) 2: Lauryl acrylate (produced by Wako Pure Chemical Industries, Ltd.) Carbon number: 12

[0161] (d) 3: Tetradecyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Carbon number: 14

[0162] (d) 4: Octadecyl acrylate (manufactured by Kyosha Chemical Co., Ltd., Rado SA), carbon number: 18

[0163] (d) 5: Behenyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) having 22 carbon atoms.

[0164] [pigment]

[0165] Pigment 1: Black pigment "MOGUL" E (manufactured by CABOT)

[0166] Pigment 2: Blue pigment Seika Sianin Blue 4920 (manufactured by Dainichi Seika Co., Ltd.)

[0167] Pigment 3: Red pigment "LIONOL" RED TT5701G (manufactured by Toyoka Rakuten Co., Ltd.)

[0168] Pigment 4: Yellow pigment "LIONOL" YELLOW TT1405G (manufactured by Toyoka Rakuten Co., Ltd.)

[0169] Pigment 5: White pigment (c) “Timek” CR58-2 (manufactured by Ishihara Sangyo Co., Ltd.).

[0170] [Extender Pigment]

[0171] Mica powder A-11 (manufactured by Matsuko Co., Ltd.).

[0172] [Surfactant]

[0173] Surfactant 1: "Disperbyk" (registered trademark) 2013 (manufactured by Bicchem Co., Ltd.)

[0174] Surfactant 2: "Solsperse" (registered trademark) 36000 (manufactured by Lubrizol)

[0175] Surfactant 3: "Solsperse" (registered trademark) 54000 (manufactured by Lubrizol Corporation).

[0176] [Other additives]

[0177] Additive 1: Sucrose benzoate "Miramer" (registered trademark) SB (manufactured by MIWON Co., Ltd.) was used as the glycosyl carboxylate.

[0178] [Example 1]

[0179] Resin (a), multifunctional (meth)acrylate (b), monofunctional (meth)acrylate alkyl ester, pigment, extender pigment, and surfactant were weighed according to the ink composition shown in Table 1, and kneaded using a three-roll mill (EXAKT (registered trademark) M-80S manufactured by EXAKT) at a gap of 1 and a speed of 500 rpm to obtain black ink 1. In addition, except that the raw materials were weighed according to the ink composition shown in Table 1 or Table 2, blue ink 3, red ink 5, yellow ink 7, and white ink 10 were obtained in the same manner as ink 1. These five inks were referred to as ink set 1.

[0180] Using the obtained ink set 1, the waterless printing in the above-mentioned (4) was performed in the printing order shown in Table 3 to print a test pattern.

[0181] The evaluation results of the ink and printing are shown in Tables 1 to 3. The viscosity values ​​of the black ink and color ink of ink set 1 were all 5.0 to 12.0, and the viscosity value of the white ink was 1.0 to 5.0, so reverse trapping, concealment, and smear resistance were all good.

[0182] [Example 2]

[0183] Yellow ink 8 was obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 1. This was combined with black ink 1, blue ink 3, red ink 5, and white ink 10 to form ink set 2.

[0184] Using the obtained ink set 2, the same operation as in Example 1 was carried out to print a color test pattern.

[0185] Ink set 2 has excellent reverse printing and concealment properties because the difference in viscosity between all black ink or color ink and white ink is 2.0 or more.

[0186] [Example 3]

[0187] White ink 11 was obtained in the same manner as ink 1 except that the raw materials were weighed in the ink composition shown in Table 2. This was combined with black ink 1, blue ink 3, red ink 5, and yellow ink 8 to form ink set 3.

[0188] Using the obtained ink set 3, a color test pattern was printed in the same manner as in Example 1.

[0189] The monofunctional alkyl (meth)acrylate (d) in the white ink of ink set 3 has 10 carbon atoms, and has good reverse overprint and excellent concealment properties.

[0190] [Examples 4, 5]

[0191] White ink 12 and ink 13 were obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 2. These were combined with black ink 1, blue ink 3, red ink 5, and yellow ink 8 to form ink set 4 and ink set 5.

[0192] Using the obtained ink set 4 and ink set 5, a color test pattern was printed in the same manner as in Example 1.

[0193] Ink set 4 and ink set 5 are both reverse-printed and have excellent concealment properties.

[0194] [Example 6]

[0195] White ink 14 was obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 2. This was combined with black ink 1, blue ink 3, red ink 5, and yellow ink 8 to form ink set 6.

[0196] Using the obtained ink set 6, the same operation as in Example 1 was carried out to print a color test pattern.

[0197] The monofunctional alkyl (meth)acrylate (d) in the white ink of ink set 6 has 22 carbon atoms, has good hiding properties, and is excellent in reverse registration.

[0198] [Example 7]

[0199] White ink 15 was obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 2. This was combined with black ink 1, blue ink 3, red ink 5, and yellow ink 8 to form ink set 7.

[0200] Using the obtained ink set 7, a color test pattern was printed in the same manner as in Example 1.

[0201] The viscosity value of the white ink in ink kit 7 is 3.4, and the minimum difference in viscosity value when it is combined with black ink or color ink is 3.6, and the maximum difference in viscosity value is 4.9. The difference in viscosity value when all black ink or color ink is combined with white ink is greater than 3.0 and less than 7.0, so the reverse overprinting is extremely excellent, and the concealment and anti-smearing properties are excellent.

[0202] [Example 8]

[0203] White ink 16 was obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 2. This was combined with black ink 1, blue ink 3, red ink 5, and yellow ink 8 to form ink set 8.

[0204] Using the obtained ink set 8, the same operation as in Example 1 was carried out to print a color test pattern.

[0205] The white ink of ink set 8 has a viscosity value of 2.0, so reverse printing is extremely excellent.

[0206] [Example 9]

[0207] White ink 17 was obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 2. This was combined with black ink 1, blue ink 3, red ink 5, and yellow ink 8 to form ink set 9.

[0208] Using the obtained ink set 9, the same operation as in Example 1 was carried out to print a color test pattern.

[0209] Ink set 9 has extremely excellent reverse offset and smear resistance and excellent concealment property because the white ink contains saccharide carboxylate.

[0210] [Example 10]

[0211] A color test pattern was printed in the same manner as in Example 1 except that ink set 7 was used and white ink printing was performed twice.

[0212] Since the white ink is printed twice in this embodiment, the reverse overprint and concealment properties are extremely excellent, and the anti-smearing property is excellent.

[0213] [Example 11]

[0214] Black ink 2, blue ink 4, red ink 6, and yellow ink 9 were obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 1. These were combined with white ink 10 to form an ink set 10.

[0215] Using the obtained ink set 10, a color test pattern was printed in the same manner as in Example 1.

[0216] In the ink set 10 , since the difference in viscosity between all black ink or color ink and white ink is 3.0 or more, reverse overprinting is extremely excellent and concealment is excellent.

[0217] [Comparative Example 1]

[0218] White ink 18 was obtained in the same manner as ink 1 except that the raw materials were weighed according to the ink composition shown in Table 2. This was combined with black ink 2, blue ink 4, red ink 6, and yellow ink 9 to form ink set 11.

[0219] Using the obtained ink set 11, a color test pattern was printed in the same manner as in Example 1.

[0220] Ink set 11 has a white ink viscosity of 6.5, so reverse overprinting, concealment, and smear resistance are poor.

[0221] [Comparative Example 2]

[0222] The same procedure as for ink 1 was carried out except that the raw materials were weighed according to the ink composition shown in Table 1 to obtain black ink 19 . This was combined with white ink 10 to form ink set 12 .

[0223] Using the obtained ink set 12, the same operation as in Example 1 was carried out to print a color test pattern.

[0224] Ink set 12 has a black ink viscosity of 4.0, so reverse printing and smear resistance are poor.

[0225] Table 1-4:

[0226]

[0227]

[0228]

[0229]

Claims

1. An active energy ray-curable printing ink kit, comprising: at least one of black ink and color ink, and White ink containing white pigment, The black ink and the color ink each contain at least one of a black pigment, a blue pigment, a red pigment, and a yellow pigment. At least one of the black ink and the color ink is a black / color ink (1) having a viscosity value of 5.0 or more and 12.0 or less, The viscosity value of the white ink is 1.0 or more and 5.0 or less, and the viscosity η at a rotation speed of 50 rpm measured at 35° C. by a cone-plate type rotational viscometer is WT50 Viscosity η at a rotation speed of 0.5 rpm WT0.5 The viscosity ratio η WT50 / η WT0.5 is greater than or equal to 0.7 and less than or equal to 1.0, The viscosity values ​​are all measured values ​​obtained 1 minute after the start of the measurement at a rotation speed of 400 rpm and a temperature of 38° C., based on item 4.2 of the test method of JIS K5701-1:2000, using an ink viscosity meter.

2. The active energy ray-curable printing ink set according to claim 1, wherein: The difference in viscosity between at least one of the black / color inks (1) and the white ink at 400 rpm measured at 38° C. using an ink viscometer is 2.0 or more and 8.0 or less.

3. The active energy ray-curable printing ink set according to claim 1 or 2, wherein: The white ink contains a resin (a), a multifunctional (meth)acrylate (b), a white pigment (c) and a monofunctional (meth)acrylate alkyl ester (d), wherein the content of the white pigment (c) is greater than or equal to 30% by mass and less than or equal to 60% by mass relative to 100% by mass of the total amount of the ink.

4. The active energy ray-curable printing ink set according to claim 3, wherein: The alkyl group of the monofunctional alkyl (meth)acrylate (d) has 12 to 20 carbon atoms.

5. A method for producing a printed matter, comprising: Using the active energy ray-curable printing ink set according to any one of claims 1 to 4, A step of applying at least one of the black / color inks (1) onto a printed material; A step of applying the white ink onto a printed material coated with the black / color ink (1); and A step of curing the ink using active energy rays.

6. The method for producing a printed matter according to claim 5, wherein: The process includes applying the white ink two or more times.

7. The method for producing a printed matter according to claim 5 or 6, wherein: The printed object is a transparent film.

8. The method for producing a printed matter according to claim 7, wherein: The transparent film is any one selected from a polyamide film, a polyester film, a polystyrene film, a polyethylene film, and a polypropylene film.

9. The method for producing a printed matter according to claim 5 or 6, wherein: The active energy rays are electron rays.

10. An active energy ray-curable lithographic ink comprising a resin (a), a multifunctional (meth)acrylate (b), a white pigment (c), and a monofunctional (meth)acrylate alkyl ester (d), The content of the white pigment (c) is 30% by mass or more and 60% by mass or less relative to 100% by mass of the total amount of the ink, Viscosity η of white pigment (c) at 35°C measured with a cone-plate type rotational viscometer at a rotation speed of 50 rpm WT50 Viscosity η at a rotation speed of 0.5 rpm WT0.5 The viscosity ratio η WT50 / η WT0.5 is 0.7 or more and 1.0 or less, and the viscosity value is 1.0 or more and 5.0 or less, The viscosity value is a value measured 1 minute after the start of measurement at a rotation speed of 400 rpm and a temperature of 38° C. based on item 4.2 of the test method of JIS K5701-1:2000 using an ink viscosity meter.

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