Method for manufacturing printed matter

Abstract

The present invention addresses the problem of providing a method for manufacturing surface-printed matter that has wet-on-wet printability as well as excellent density stability.　The present invention is a method for manufacturing printed matter, the method including in the stated order: an ink (A) transfer step for transferring the colorless or white ink (A) defined below onto a base material; a drying step for evaporating water or a solvent contained in the ink (A); an ink (B) transfer step for transferring the ink (B) defined below onto the base material; and an irradiation step for irradiating the transferred ink with active energy rays. Ink (A): volatile active energy ray-curable ink containing water or a solvent Ink (B): non-volatile active energy ray-curable ink not substantially containing water or a solvent

Description

Printing method

[0001] The present invention relates to a method for producing a printed matter.

[0002] Demand for flexible packaging, which is primarily used to package food and daily necessities, is expected to continue to grow in line with the global population increase, from the perspective of protecting the contents and preventing damage to the packaging during transportation and storage. Generally, flexible packaging is produced by printing on a plastic film substrate, then laminating the printed material with a sealant using an adhesive, before being processed into a bag (bag making).

[0003] Generally, packaging materials are made of laminates combining various films such as polyolefin, polyester, and polyamide, depending on the functionality required after bag production, such as strength and heat resistance. In recent years, growing environmental awareness has led to a demand for recyclable packaging materials, and monomaterials made of only the same type of film material have been attracting attention.

[0004] Since the printed image after the bag is made will be visible from the back of the substrate, a mirror image is printed on the substrate film, which is reverse printing. With reverse printing, lamination is always required after printing, so an aging process after lamination is essential, and the bag cannot be immediately moved on to the processing and filling process after printing.

[0005] On the other hand, surface-printed materials, where the printed side is the front side of the bag, require durability from the printed surface itself, but do not require lamination after printing, so they have the advantage of short delivery times and low costs.

[0006] Gravure printing, currently the mainstream method for printing on flexible packaging, produces prints that look vibrant, but because it uses inks that contain large amounts of solvent, it requires a lot of energy to dry the ink solvent and treat the exhaust, placing a heavy burden on the environment. Furthermore, different inks are generally used for reverse printing and front printing, each adjusted for their respective characteristics such as film strength and lamination suitability, making them unusable.

[0007] Meanwhile, in recent years, attempts have been made to use EB flexographic printing and EB offset printing, which cure inks by irradiation with actinic energy rays, particularly electron beams (EB), in flexible packaging printing (Patent Documents 1 and 2). Generally, flexible packaging printing is performed using a roll-to-roll process, making quick drying of the ink important. Actinic energy ray-curing printing methods not only offer environmental benefits by using almost no solvents, but also offer energy savings and high productivity by shortening the drying process without using thermal energy. Furthermore, curing by electron beam irradiation has excellent transparency and does not require a photopolymerization initiator in the ink, reducing the risk of printed matter odor and the migration of initiator decomposition components to the contents, thereby providing safety benefits by protecting the contents of the flexible packaging. However, electron beam irradiation equipment is more expensive and larger than ultraviolet irradiation equipment. Therefore, unlike ultraviolet irradiation equipment, electron beam irradiation equipment is installed after the final printing cylinder to cure the ink all at once, rather than on each printing cylinder. Therefore, the printing process is wet-on-wet, in which uncured ink is applied over and over again.

[0008] Patent Document 3 discloses a printing process for imparting wet-on-wet printability to an actinic ray-curable flexographic ink. According to this process, a preprinted actinic ray-curable flexographic ink is printed on a film, dried to form a gel, and then a postprinted actinic ray-curable flexographic ink is printed on the film, maintaining good trapping properties while overlaying colors, and finally cured by EB irradiation.

[0009] JP 2004-358788 A International Publication No. 2019 / 69736 Patent No. 5959855 A

[0010] However, in the technology disclosed in Patent Document 3, a solvent that can be distilled off is contained in the ink in order to impart wet-on-wet printability, and therefore fluctuations in the ink's physical properties occur not only during drying but also during storage and in the printing machine due to solvent evaporation. As a result, there are problems with continuous printing stability, such as a tendency for density, particularly in process colors, a lack of stability in density and halftone dot shape during continuous printing, and large density variations within the same printed surface.

[0011] Therefore, an object of the present invention is to provide a method for producing a surface-printed product that is not only suitable for wet-on-wet printing but also has excellent continuous printing stability.

[0012] That is, the present invention is a method for producing a printed matter, comprising, in this order: an ink (A) transfer step of transferring a colorless or white ink (A) as defined below to a substrate; a drying step of evaporating water or a solvent contained in the ink (A); an ink (B) transfer step of transferring an ink (B) as defined below to a substrate; and an irradiation step of irradiating the transferred ink with actinic rays. Ink (A): a volatile actinic ray-curable ink containing water or a solvent. Ink (B): a non-volatile actinic ray-curable ink that is substantially free of water or a solvent.

[0013] The method for producing a printed matter according to the present invention enables surface printing with excellent wet-on-wet printability and density stability, and the resulting printed matter exhibits excellent hiding power and abrasion resistance.

[0014] The present invention will be specifically described below. In the present invention, "or more" means the same as or greater than the indicated numerical value. Furthermore, "or less" means the same as or smaller than the indicated numerical value. Furthermore, "(meth)acrylate" is a generic term including acrylate and methacrylate.

[0015] The present invention is characterized by comprising, in this order, an ink (A) transferring step of transferring a colorless or white ink (A) as defined below to a substrate, a drying step of evaporating water or a solvent contained in the ink (A), an ink (B) transferring step of transferring an ink (B) as defined below to a substrate, and an irradiation step of irradiating the transferred ink with actinic rays: Ink (A): a volatile actinic ray-curable ink containing water or a solvent, Ink (B): a non-volatile actinic ray-curable ink substantially free of water or a solvent.

[0016] Generally, in surface printing, the fluidity of white ink or colorless anchor ink, which is printed over almost the entire surface of the substrate and serves as the base color for the printed image, is important in order to ensure good hiding power (in the case of white ink) and gloss in the appearance of the printed matter.

[0017] On the other hand, in wet-on-wet printing, the tack (viscosity, cohesive strength) of the later-printed ink must be lower than that of the pre-printed ink, otherwise the printed pre-printed ink will be peeled off during the later printing, causing color mixing. For this reason, there is a trade-off between adjusting the tack balance between inks and achieving high white fluidity.

[0018] In the technology disclosed in Patent Document 3, a solvent that can be evaporated is contained in the ink and dried between cylinders, so that the solvent is peeled off in the subsequent printing, preventing color mixing and realizing wet-on-wet printing suitability. However, because each ink contains a solvent that can be evaporated, fluctuations in the ink's physical properties occur not only during drying but also during storage and in the printing machine due to solvent evaporation.

[0019] For white, which is the base color, the image is generally solid, the ink supply is large, and high density is required, so fluctuations in ink properties have little effect.However, for color inks such as process colors and special colors other than white, print quality is affected by factors such as density and dot shape, so it is desirable to have small fluctuations during continuous printing.

[0020] In the method for producing printed matter of the present invention, the white or colorless ink that serves as the base color contains volatile water or solvent to give it high fluidity, and a drying process is performed before the post-printing, which prevents it from being peeled off during the post-printing and prevents color mixing. Furthermore, the color inks used in the post-printing, such as process colors and spot colors, are substantially free of volatile components, which reduces fluctuations in ink properties such as viscosity, making it less likely that the ink supply amount will fluctuate during continuous printing, improving the stability of print quality.

[0021] (Active Energy Ray-Curable Ink) Preferred embodiments of the active energy ray-curable ink, which are common to ink (A) and ink (B), will be described.

[0022] The active energy ray-curable ink of the present invention, i.e., ink (A) and / or ink (B), preferably contains a (meth)acrylate having an alicyclic skeleton. By containing a (meth)acrylate having an alicyclic skeleton, volume shrinkage during curing by active energy ray irradiation is reduced, and the adhesion of the cured ink film to the substrate is improved.

[0023] Examples of the (meth)acrylate having an alicyclic skeleton include isobornyl (meth)acrylate, norbornyl (meth)acrylate, norbornane-2-methanol (meth)acrylate, cyclohexyl (meth)acrylate, 1-adamantyl (meth)acrylate, 3-methyladamantan-2-yl (meth)acrylate, 3-ethyladamantan-2-yl (meth)acrylate, 9,9-bis[4-(meth)acryloyloxyethoxyphenyl]fluorene, 9,9-bis[4-(3-(meth)acryloyloxy-2-hydroxypropyloxy)phenyl]fluorene, tricyclopentenyl (meth)acrylate, tricyclopentenyloxy (meth)acrylate, tricyclodecane monomethylol (meth)acrylate, and dicyclopentadienyl tricyclodecane dimethanol di(meth)acrylate.

[0024] In particular, the alicyclic skeleton is more preferably one or more selected from a norbornane skeleton, an adamantane skeleton, a tricyclodecane skeleton, and a dicyclopentadiene skeleton, because this results in small volumetric shrinkage during curing and good physical properties of the cured coating, such as scratch resistance.

[0025] Furthermore, monofunctional or polyfunctional (meth)acrylates having no alicyclic skeleton can also be used.

[0026] Examples of monofunctional (meth)acrylates include hexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, benzyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, polyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, N-(2-hydroxyethyl)acrylamide, N-(2-hydroxyethyl)methacrylamide, N-(2-hydroxymethyl)acrylamide, N-(2-hydroxymethyl)methacrylamide, acryloylmorpholine, dimethylacrylamide, methoxymethylacrylamide, diethylacrylamide, and isopropylacrylamide.

[0027] Examples of bifunctional (meth)acrylates include diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, hexyl di(meth)acrylate, nonyl di(meth)acrylate, decanedi(meth)acrylate, 4,4'-isopropylidenediphenol di(meth)acrylate, and their ethylene oxide adducts, propylene oxide adducts, and tetraethylene oxide adducts.

[0028] Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, isocyanuric acid tri(meth)acrylate, and ethylene oxide adducts and propylene oxide adducts thereof.

[0029] Examples of tetrafunctional (meth)acrylates include pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, diglycerin tetra(meth)acrylate, and ethylene oxide adducts and propylene oxide adducts thereof.

[0030] Examples of penta- or higher functional (meth)acrylates include dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ethylene oxide and propylene oxide adducts thereof.

[0031] The active energy ray-curable ink of the present invention, i.e., ink (A) and / or ink (B), preferably contains a resin. Examples of the resin include acrylic resin, urethane resin, and phthalate resin, and either a commercially available product or a synthetic product may be used.

[0032] The acrylic resin can be obtained by polymerizing a (meth)acrylate monomer alone or in combination with two or more monomers in an organic solvent in the presence of a polymerization initiator. It can also be obtained by copolymerizing styrene, α-methyl-styrene, or the like.

[0033] Examples of commercially available acrylic resins include the "Hi-Loss" (registered trademark) series manufactured by Seiko PMC Corporation.

[0034] The urethane resin can be obtained by mixing one or more polyols and one or more polyisocyanates and carrying out a polycondensation reaction in an organic solvent in the presence of a condensing agent. Examples of the polyol include polyester polyols, polycarbonate polyols, and polyether polyols, and examples of the polyisocyanates include polyurethane polyisocyanates and isocyanurates.

[0035] The phthalate resin can be obtained by carrying out a polymerization reaction of diallyl orthophthalate or diallyl isophthalate alone or in combination in an organic solvent in the presence of a polymerization initiator.

[0036] Examples of commercially available phthalate resins include the "Daiso DAP" (registered trademark) series and "Daiso Isodap" (registered trademark) manufactured by Osaka Soda Co., Ltd.

[0037] Examples of pigments contained in the active energy ray-curable ink of the present invention include phthalocyanine pigments, soluble azo pigments, insoluble azo pigments, lake pigments, quinacridone pigments, isoindoline pigments, threne pigments, metal complex pigments, titanium oxide, zinc oxide, alumina white, calcium carbonate, barium sulfate, red iron oxide, cadmium red, yellow lead, zinc yellow, iron blue, ultramarine, oxide-coated glass powder, oxide-coated mica, oxide-coated metal particles, aluminum powder, gold powder, silver powder, copper powder, zinc powder, stainless steel powder, nickel powder, organic bentonite, iron oxide, carbon black, and graphite.

[0038] Furthermore, colorless extender pigments such as mica (hydrated potassium aluminum silicate) and talc (magnesium silicate) can also be used, and the active energy ray-curable ink of the present invention can also be used as an anchor ink or overprint varnish that does not contain a color pigment.

[0039] The active energy ray-curable ink of the present invention, i.e., ink (A) and / or ink (B), preferably contains a wax. By containing a wax in the active energy ray-curable ink, the scratch resistance and slip properties of the cured film are improved.

[0040] Examples of the wax that can be used include natural waxes such as carnauba wax, Japan wax, montan wax, and lanolin, and synthetic waxes such as hydrocarbon waxes, polytetrafluoroethylene wax, polyamide wax, and silicone compounds. Of these, hydrocarbon waxes are preferred because of their excellent abrasion resistance.

[0041] Examples of hydrocarbon waxes include Fischer-Tropsch wax, polyethylene wax, polypropylene wax, paraffin wax, microcrystalline wax, etc. These waxes may be used alone or in combination of two or more.

[0042] The content of the wax in ink (A) or ink (B) is preferably 0.1% by mass or more and 10% by mass or less. By having the wax content be 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, scratch resistance and slipperiness are improved. Furthermore, by having the wax content be 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, the wax is well dispersed and fluidity is improved.

[0043] The active energy ray-curable ink of the present invention, i.e., ink (A) and / or ink (B), may contain other additives, such as a photopolymerization initiator, a pigment dispersant, a defoaming agent, and a leveling agent.

[0044] However, the active energy ray-curable ink in the present invention may be an ultraviolet-curable ink containing a photopolymerization initiator, but in terms of reducing the environmental burden, a radiation-curable ink that does not contain a photopolymerization initiator is more preferred.

[0045] The actinic radiation-curable ink used in the present invention may be either a flexographic ink or an offset ink. As the offset ink, an ink for waterless lithographic printing may be used.

[0046] When synthesizing the active energy ray-curable ink of the present invention, a pigment and an auxiliary are added to a resin varnish obtained by dissolving a resin in a monofunctional or polyfunctional (meth)acrylate, and the resulting mixture is dispersed and mixed using a three-roll mill in the case of an offset ink, or an attritor, ball mill, sand mill, or the like in the case of a flexographic ink.

[0047] (Ink (A)) Ink (A) is a volatile active energy ray-curable ink containing water or a solvent.

[0048] Examples of solvents in ink (A) include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, methyl ethyl ketone, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, propyl propionate, butyl propionate, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol dimethyl ether, and propylene glycol monomethyl ether acetate. One or more solvents may be used alone or in combination. Furthermore, water and a solvent may be used in combination.

[0049] The ink (A) preferably contains water or a solvent having a boiling point of 150° C. or less at 1 atmospheric pressure. When the boiling point of the water or solvent is 150° C. or less, more preferably 120° C. or less, the ink (A) is imparted with an appropriate quick-drying property. Furthermore, the ink (A) is dried instantly in the subsequent drying step, which makes it possible to suppress peeling off by the subsequently printed ink (B) and color mixing.

[0050] The content of water and / or solvent in ink (A) is preferably 10% by mass or more and 50% by mass or less in total of water and solvent. A content of 10% by mass or more, more preferably 20% by mass or more, suppresses peeling by ink (A) in subsequent printing after the drying step and color mixing. Furthermore, a content of 50% by mass or less, more preferably 40% by mass or less, imparts quick drying properties in the drying step.

[0051] The ink (A) has a viscosity η at 25°C and a rotation speed of 0.5 rpm according to JIS Z8803:2011 "Viscosity measurement method using a coaxial double cylindrical rotational viscometer." Ａ is preferably 0.1 Pa·s or more and 5 Pa·s or less. Ａ When the viscosity is 0.1 Pa·s or more and 5 Pa·s or less, more preferably 0.5 Pa·s or more and 2 Pa·s or less, the fluidity of the ink that becomes a colorless or white base color becomes good.

[0052] As described above, either flexographic ink or offset ink can be used as the active energy ray-curable ink in the present invention. However, it is particularly preferable to use, as the ink (A), a flexographic ink which has a low viscosity and may contain water or a solvent.

[0053] Examples of commercially available volatile electron beam curable flexographic inks include "Wetflex" manufactured by Sun Chemical and "Gelflex" manufactured by Sakata-Inx.

[0054] (Ink (B)) Ink (B) is a non-volatile actinic radiation-curable ink that is substantially free of water or solvent. "Substantially free of water or solvent" means that the total content of water and solvent in the ink is 0.5% by mass or less.

[0055] The ink (B) has a viscosity η of 25°C at a rotation speed of 0.5 rpm according to the "Viscosity measurement method using a coaxial double cylindrical rotational viscometer" of JIS Z8803:2011. Ｂ is preferably 20 Pa·s or more and 200 Pa·s or less. Ｂ By setting the viscosity to 20 Pa·s or more and 200 Pa·s or less, more preferably 40 Pa·s or more and 100 Pa·s or less, fluctuations in the physical properties of color inks such as process colors and special colors during printing can be kept small.

[0056] Also, η Ａ and η Ｂ When the values ​​are within the respective preferred ranges, the tackiness between the inks can be balanced, and continuous printing stability is improved, which is preferable.

[0057] As described above, either flexographic ink or offset ink can be used as the active energy ray-curable ink in the present invention. However, it is particularly preferable to use, as ink (B), an offset ink which has a high viscosity and does not contain a volatile component.

[0058] Examples of commercially available non-volatile electron beam curable offset inks include "Sun Beam" manufactured by Sun Chemical and "XCURA EVO" manufactured by Flint.

[0059] (Printing press) In the method for producing a printed matter of the present invention, it is preferable to use a center-drum type printing press. The center-drum type refers to a press having a single impression cylinder that sandwiches the printing substrate and faces a cylinder for transferring ink and a pressure cylinder. A center-drum type printing press is suitable for wet-on-wet printing processes because it does not require guide rolls for transporting the film between the cylinders.

[0060] Specific examples of center drum type printing presses include commercially available flexographic printing presses such as "MIRAFLEX" manufactured by Windmoeller & Hoelscher and "ONYX XS" manufactured by UTECO, and commercially available offset printing presses such as "CI-8" manufactured by COMEXI.

[0061] (Substrate) In the method for producing a printed matter of the present invention, it is preferable to use a non-absorbing raw material such as a metal or film as the substrate.

[0062] Examples of the film include polyesters such as polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, and polylactic acid, polyamide, polyimide, polyalkyl(meth)acrylate, polystyrene, poly-α-methylstyrene, polycarbonate, polyvinyl alcohol, polyvinyl acetal, polyvinyl chloride, and polyvinylidene fluoride. Among these, from the viewpoint of recyclability, it is preferable to use polyethylene or polypropylene alone, or a laminate thereof.

[0063] The film may be subjected to a surface treatment such as burning, easy-adhesion coating, or chemical vapor deposition.

[0064] The thickness of the substrate is preferably 5 μm or more and 50 μm or less. By making the thickness of the substrate 5 μm or more, preferably 10 μm or more, the mechanical strength of the substrate necessary for printing can be effectively obtained. Furthermore, by making the thickness 50 μm or less, preferably 30 μm or less, the cost of the substrate can be kept low.

[0065] When the substrate is a type of paper, such as coated paper such as art paper, coated paper, or cast paper, uncoated paper such as fine paper, newsprint, or Japanese paper, or synthetic paper or aluminum-deposited paper, a transparent ink may be used instead of a white ink as the ink (A).

[0066] The substrate used in the method for producing a printed matter of the present invention may be in the form of either a sheet or a roll. When printing on a thin film for flexible packaging, it is preferable to use a roll film and perform printing by roll-to-roll.

[0067] (Transfer Step) In each transfer step, the ink is transferred onto the transfer surface of the substrate.

[0068] Generally, color prints require a printing unit for transferring ink for each color to be printed. In each printing unit, the ink in the image area is transferred from the anilox roll or ink roll to the printing plate, or, depending on the method, via a blanket, onto the receiving surface of the printed material.

[0069] In the transfer step, the method of transferring the ink to the surface to be printed is preferably flexographic printing for low-viscosity volatile ink, or offset printing for high-viscosity non-volatile ink.

[0070] The printing method of the present invention includes, in the transfer step, an ink (A) transfer step of transferring a colorless or white ink (A) to a substrate, and an ink (B) transfer step of transferring ink (B) to a substrate, in this order.

[0071] For example, a white ink (A) can be first transferred onto a substrate to form a surface print. By performing surface print, the substrate itself can separate the cured ink layer from the packaged object, even in flexible packaging for packaging food or household goods, making it unnecessary to apply a sealant.

[0072] (Drying Process) In the method for producing a printed matter of the present invention, the water or solvent contained in the volatile ink transferred to the substrate can be removed by air blowing with a hot air dryer or the like, which is commonly used in flexographic printing machines. If the volatile component is a compound containing a hydroxyl group, such as water, an IR dryer can also be used. By removing the volatile component in the drying process, the volatile ink transferred to the substrate becomes semi-dried and its viscosity increases significantly. This results in a higher viscosity and cohesive force than the ink on the subsequent printing cylinder, thereby suppressing peeling and color bleeding.

[0073] Generally, the viscosity of the volatile ink is Ａ and the viscosity of the non-volatile ink is within the range of η Ｂ In normal wet-on-wet printing, if the viscosity is within this range, the pre-printed volatile ink will be stripped off by the post-printed non-volatile ink, which has an overwhelmingly higher viscosity, resulting in color mixing and making normal printing impossible. However, by using the volatile ink drying process of the present invention and then continuously printing the post-printed non-volatile ink, stripping and color mixing due to the post-printed ink can be suppressed, making continuous printing with stable quality possible.

[0074] (Overprint varnish transfer process) In the method for producing a printed matter of the present invention, it is preferable to include a process (overprint varnish transfer process) of transferring an active energy ray-curable overprint varnish to the substrate to which the ink (A) and ink (B) have been transferred, between the ink (B) transfer process and the irradiation process.

[0075] The actinic radiation-curable overprint varnish protects the cured printed ink and improves the scratch resistance of the surface-printed material. Depending on the properties of the varnish, it can also impart gloss or matte finish to the design of the printed material.

[0076] (Irradiation Step) In the irradiation step, the transferred ink is irradiated with active energy rays.

[0077] In the method for producing printed matter of the present invention, examples of sources of actinic radiation include ultraviolet light (particularly LED-UV), electron beams, and gamma rays. Radiation such as electron beams and gamma rays generates high-energy secondary electrons in the irradiated material, exciting surrounding molecules and generating reactive species such as radicals. When the irradiated material is an actinic radiation-curable ink, radicals are generated in the ink, causing radical polymerization to proceed, resulting in a cured ink film. In particular, electron beams generated at a low acceleration voltage are preferably used because they have sufficient permeability for ink films of 10 μm or less, can provide the energy necessary for curing, do not require special qualifications for use, and are easy to handle.

[0078] The penetration depth of an electron beam is determined by the acceleration voltage, and the acceleration voltage of the electron beam is preferably 50 kV or more, more preferably 90 kV or more, and even more preferably 110 kV or more, so that a sufficient dose of the electron beam penetrates the ink film. Furthermore, as the penetration depth increases, the dose of the electron beam imparted to the inside of the film also increases, so the acceleration voltage is preferably 300 kV or less, more preferably 200 kV or less, and even more preferably 150 kV or less.

[0079] Furthermore, the higher the electron beam irradiation dose, the greater the amount of radical species generated in the target substance, but also the greater the damage to the film. Therefore, the irradiation dose is preferably 10 kGy or more and 100 kGy or less, and more preferably 20 kGy or more and 50 kGy or less.

[0080] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0081] <Measurement and evaluation methods> (1) Ink viscosity (η Ａ , η Ｂ ) The viscosity was measured according to JIS Z8803:2011 "Method for measuring viscosity using a coaxial double cylindrical rotational viscometer." A B-type viscometer (DV-II manufactured by BROOKFIELD) equipped with a cylinder spindle No. 4 was used, and the measurement was performed under the conditions of 25°C and a rotation speed of 0.5 rpm.

[0082] (2) Tack Value 1.3 ml of ink was applied to the roller of an Inkometer (Tester Sangyo Co., Ltd., "INKOGRAPH" TYPE-V), and the roller was operated at a roller temperature of 38° C. and a rotation speed of 400 rpm, and the tack value was measured after 1 minute.

[0083] (3) Printability The printed matter was observed and evaluated according to the following criteria. A: Color printing with no ink peeling or color mixing. B: Slight peeling of the white ink due to color ink printed after it, or color mixing where the color ink appears slightly whitish, is observed. C: Peeling of the white ink due to color ink printed after it, or color mixing is observed.

[0084] (4) Opacity The opacity of the printed matter was measured using a reflection densitometer (eXact Advance, manufactured by xRite Corporation) for areas containing only solid white. An opacity value of 55% or more is considered good, and an opacity value of 60% or more is considered extremely good.

[0085] (5) Density Stability During continuous printing of 4000 m, five samples were taken every 1000 m from the start of printing, and the density of the process colors (CMYK) of each sample was measured. The difference between the maximum and minimum density values ​​of the five samples for each color was calculated, and the largest value among the four color differences was called the maximum density difference, and this value was recorded. Evaluation was then performed according to the following criteria: A: The maximum density difference was 0.1 or less. B: The maximum density difference was greater than 0.1 and less than 0.2. C: The maximum density difference was greater than 0.2.

[0086] (6) Peelability of printed matter On a solid white area of ​​a printed matter, a piece of "Cellotape" (registered trademark) No. 405 (width 18 mm) manufactured by Nichiban Co., Ltd. was applied to a randomly selected area of ​​30 mm x 18 mm, and then the area was peeled off by hand and evaluated according to the following criteria: A: The ink film did not peel off. B: Partial peeling of the ink film was observed.

[0087] (7) Scratch resistance of printed matter A randomly selected 3 cm x 3 cm area of ​​the solid white part of the printed matter was rubbed back and forth with a human fingernail 20 times, and the rub resistance was evaluated according to the following criteria: A: No scratches caused by the fingernail were observed. B: Partial peeling of the ink was observed along the fingernail marks.

[0088] <Printing Unit> As the printing units corresponding to the first to fifth cylinders of the printing press described later, any of the following was used.

[0089] (1) Flexographic Printing Unit A printing plate (AWP DEW manufactured by Asahi Kasei) was used, and an image of the corresponding color was exposed and developed to make a plate. An anilox roller (Nova Gold manufactured by Praxair Surface Technologies) was used.

[0090] (2) Offset Printing Unit A waterless lithographic printing plate precursor (TAC-VT4, manufactured by Toray Industries, Inc.) was used as the printing plate, and the corresponding color image was exposed and developed to make a plate. A rubber roller manufactured by Boetcher, 726-40, and a blanket manufactured by Kinyosha, T414W were used.

[0091] <Printing Method> First, the configuration common to the following printing methods 1 to 5 will be described.

[0092] Starting from the upstream side in the running direction of the printing substrate, white ink was set on the first cylinder, black ink on the second cylinder, cyan ink on the third cylinder, magenta ink on the fourth cylinder, and yellow ink on the fifth cylinder.

[0093] Using the same image for printing methods 1 to 4, the solid areas of the process colors were set to predetermined print densities (black 1.7, cyan 1.4, magenta 1.3, yellow 1.1), and then 4,000 m of surface color printing was carried out continuously on the substrate at a printing speed of 200 m / min.

[0094] In the irradiation step, the ink was cured by irradiating it with an electron beam at an acceleration voltage of 110 kV and an exposure dose of 30 kGy, thereby obtaining a printed matter.

[0095] [Printing Method 1] In Printing Method 1, a flexographic printing unit was installed on the first cylinder of a printing press (CI-8 manufactured by COMEXI), and offset printing units were installed on the second to fifth cylinders. Hot air drying was performed only between the first and second cylinders.

[0096] [Printing Method 2] In printing method 2, all of the first to fifth cylinders of a printing press (ONYX XS manufactured by UTECO) were used as flexographic printing units, and hot air drying was carried out between each cylinder.

[0097] [Printing Method 3] In printing method 3, all of the first to fifth cylinders of a printing press (UTECO ONYX XS) were used as flexographic printing units, and drying was not performed between the cylinders.

[0098] [Printing Method 4] In printing method 4, all of the first to fifth cylinders of a printing press (CI-8 manufactured by COMEXI) were used as offset printing units, and drying was not performed between the cylinders.

[0099] [Printing Method 5] In Printing Method 5, flexographic printing units were installed on the first and eighth cylinders of a printing press (CI-8 manufactured by COMEXI), and offset printing units were installed on the second to fifth cylinders. Hot air drying was performed only between the first and second cylinders. An active energy ray-curable overprint varnish was installed on the eighth cylinder.

[0100] <Ink raw materials> (Pigment, pigment dispersant) White pigment: Typec CR57 (manufactured by Ishihara Sangyo Kaisha) Black pigment: MA-11 (manufactured by Mitsubishi Chemical Corporation) Indigo pigment: Lionor Blue FG7330 (manufactured by Toyo Color Co., Ltd.) Crimson pigment: Lionor Red TT5701G (manufactured by Toyo Color Co., Ltd.) Yellow pigment: Lionor Yellow TT1405G (manufactured by Toyo Color Co., Ltd.) Extender pigment: A-11 (manufactured by Yamaguchi Mica Co., Ltd.) Pigment dispersant: "Disperbyk" (registered trademark) 111 (manufactured by BYK-Chemie).

[0101] (Monomers) Monomer 1: pentaerythritol triacrylate ("Miramer" (registered trademark) M340, manufactured by MIWON Corporation) Monomer 2: trimethylolpropane triacrylate ethylene oxide adduct ("Miramer" (registered trademark) M3190, manufactured by MIWON Corporation) Monomer 3: (meth)acrylate having an alicyclic skeleton, tricyclodecane dimethanol diacrylate ("Miramer" (registered trademark) M262, manufactured by MIWON Corporation) Monomer 4: 1,6-hexanediol diacrylate ("NK Ester" (registered trademark) A-HD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0102] (Oligomer) Oligomer: urethane acrylate (UF-8001G manufactured by Kyoeisha Chemical Co., Ltd.).

[0103] (Acrylic Resin) Acrylic resin: A copolymer of 25% by mass of methyl methacrylate, 25% by mass of styrene, and 50% by mass of methacrylic acid, to which 0.6 equivalents of glycidyl methacrylate have been added in reaction with a carboxyl group (weight average molecular weight: 34,000, acid value: 102 mgKOH / g).

[0104] (Polymerization inhibitor) Polymerization inhibitor: p-methoxyphenol (manufactured by Wako Pure Chemical Industries, Ltd.).

[0105] (Water, Solvent) Water: Pure water (manufactured by Wako Pure Chemical Industries, Ltd.) Solvent 1: 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.), boiling point 83°C Solvent 2: Propylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), boiling point 188°C.

[0106] (Wax) Wax: "KTL" (registered trademark) 4N (manufactured by Kitamura Co., Ltd.).

[0107] <Preparation of Inks> White ink was prepared according to the formulation shown in Table 1, and black, cyan, magenta, and yellow color inks were prepared according to the formulation shown in Table 2. The ink ingredients listed below were weighed and mixed using a bead mill for the flexographic ink and a three-roll mill for the offset ink to prepare the inks.

[0108] <Active energy ray curable overprint varnish> EB varnish: OPV EB UMatt UQ1601 manufactured by Sun Chemical Co., Ltd.

[0109] <Printing substrate> Substrate 1: PET film (S-46 manufactured by Polyplex, thickness 12 μm) Substrate 2: PE film (PE3K-H manufactured by Futamura Chemical, thickness 25 μm) Substrate 3: Biaxially oriented polypropylene (OPP) film ("AlOx-Lyte" manufactured by Jindal Film, thickness 20 μm).

[0110]

[0111]

[0112] [Examples 1 to 5 and Comparative Example 1] Surface printing was carried out using the printing method, white ink and color ink set shown in Table 3, and substrate 1 (PET film) as the substrate.

[0113] In Example 1, by performing inter-cylinder drying of the white ink (A), peeling did not occur even with the high-viscosity offset ink used in post-printing, demonstrating good printability. Furthermore, the density of the color inks was stable even during continuous printing.

[0114] In Example 2, in which the amount of solvent in the ink (A) was small compared to Example 1, and in Example 3, in which the boiling point of the solvent in the ink (A) was high, the increase in viscosity of the white ink after drying was small, and the printability was rated B.

[0115] In Example 4, in which water was used instead of the solvent in the ink (A) in Example 1, good printability and continuous printing stability were also exhibited.

[0116] In Example 5, which used a monomer containing an alicyclic skeleton, in addition to good printability and continuous printing stability, improvements were also observed in the adhesion and abrasion resistance of the printed matter.

[0117] In Comparative Example 1, in which ink (A) was also used for the color inks, good printability was demonstrated for all colors by performing inter-cylinder drying for each color, but the density fluctuation during continuous printing was large and printing stability was insufficient.

[0118] The printing conditions and evaluation results are shown in Table 3.

[0119] Comparative Examples 2 to 4 Surface printing was carried out using Printing Method 2, a completely wet-on-wet process, the white ink and color ink set shown in Table 3, and Substrate 1 (PET film) as the substrate.

[0120] In Comparative Example 2, only flexographic ink (B) was used, including the white ink. In Comparative Example 2, the white ink and the pre-printed color inks were picked up by the rear cylinder, causing color mixing, preventing the color inks from adhering, and preventing normal printing.

[0121] In Comparative Examples 3 and 4, only offset ink (B) was used, including the white ink. In Comparative Example 3, the white ink was picked up by the rear cylinder, causing color mixing. In addition, the color inks did not adhere, and normal printing was not possible. In Comparative Example 4, the wet-on-wet printability and density stability were rated A, but the leveling of the white ink was poor and the hiding power was insufficient.

[0122] The printing conditions and evaluation results are shown in Table 3.

[0123]

[0124] [Example 7] Surface printing was carried out in the same manner as in Example 5, except that the substrate was changed to Substrate 2 (PE film). Even though the substrate was changed, the printability, hiding power, and density stability were good. Furthermore, there was no peeling or peeling due to abrasion, and the results were good. The results are shown in Table 4.

[0125] Example 8 Surface printing was carried out using Printing Method 5, EB varnish as the overprint varnish, White Ink 1, Color Ink Set 1, and Substrate 3 (OPP film) as the substrate. As in Example 1 using Printing Method 1, printability and hiding power were good, and the color ink density was stable. Furthermore, the application of the overprint varnish was satisfactory, with no peeling or abrasion-induced peeling. The results are shown in Table 4.

[0126]

Claims

1. A method for producing a printed matter, comprising, in this order, an ink (A) transfer step of transferring a colorless or white ink (A) as defined below to a substrate, a drying step of evaporating water or a solvent contained in the ink (A), an ink (B) transfer step of transferring an ink (B) as defined below to a substrate, and an irradiation step of irradiating the transferred ink with active energy rays. Ink (A): A volatile active energy ray curable ink containing water or a solvent. Ink (B): A non-volatile active energy ray curable offset ink that is substantially free of water or solvent.

2. 2. The method for producing a printed matter according to claim 1, wherein the viscosity of the ink (A) at 25°C and a rotation speed of 0.5 rpm is 0.1 Pa·s or more and 5 Pa·s or less, and the viscosity of the ink (B) at 25°C and a rotation speed of 0.5 rpm is 20 Pa·s or more and 200 Pa·s or less.

3. The method for producing a printed matter according to claim 1 or 2, wherein the ink (A) is a flexographic ink.

4. The method for producing a printed matter according to any one of claims 1 to 3, wherein the ink (A) contains water or a solvent having a boiling point of 150°C or lower at 1 atmospheric pressure.

5. The method for producing a printed matter according to any one of claims 1 to 4, wherein the content of water and / or the solvent in the ink (A) is 10% by mass or more and 50% by mass or less in total of the water and the solvent.

6. The method for producing a printed matter according to any one of claims 1 to 5, wherein the ink (A) and / or the ink (B) contains a (meth)acrylate having an alicyclic skeleton.

7. The method for producing a printed matter according to claim 6 , wherein the alicyclic skeleton is at least one selected from a norbornane skeleton, an adamantane skeleton, a tricyclodecane skeleton, and a dicyclopentadiene skeleton.

8. The method for producing a printed matter according to any one of claims 1 to 7, wherein the ink (A) and / or the ink (B) contains wax.

9. The method for producing a printed matter according to any one of claims 1 to 8, wherein the substrate is a non-absorbing stock sheet.

10. The method for producing a printed matter according to any one of claims 1 to 9, wherein the thickness of the substrate is 5 µm or more and 50 µm or less.

11. The method for producing a printed matter according to any one of claims 1 to 10, using a center drum type printing press.

12. The method for producing a printed matter according to any one of claims 1 to 11, further comprising, between the ink (B) transferring step and the irradiation step, an overprint varnish transferring step of transferring an active energy ray-curable overprint varnish to the substrate to which the ink (A) and the ink (B) have been transferred.

13. The method for producing a printed matter according to any one of claims 1 to 12, wherein the substrate is a single type of polyethylene or polypropylene, or a laminate thereof.