Manufacturing method of 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

[Technical field]

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

[0002] From the viewpoint of protecting the contents and preventing damage to the packaging during transportation and storage, flexible packaging is used mainly for packaging food and daily necessities, and demand is expected to continue to grow in the future due to the global population increase. In general, flexible packaging is made by printing on the base plastic film, then laminating the printed matter and sealant with an adhesive, and then processing it into a bag (making a bag).

[0003] Generally, a laminate made by combining various films such as polyolefin, polyester, polyamide, etc. is used as a packaging material depending on the functionality required after the bag is made, such as strength, heat resistance, etc. In recent years, with the increase in environmental awareness, there is a demand for recyclable packaging materials, and monomaterials made of only the same type of film material are attracting attention.

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

[0005] On the other hand, front-printed materials, where the printed side is the front side of the bag, require durability of 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, which is currently the mainstream method for printing on flexible packaging, produces prints that look vivid, but because it uses inks that contain large amounts of solvent, it requires a large amount of energy to dry the ink solvent and to treat the exhaust, which places a large burden on the environment.In addition, different inks are generally used for reverse printing and front printing, each adjusted to have different film strength and lamination suitability according to their respective characteristics, so they cannot be used interchangeably.

[0007] Meanwhile, in recent years, attempts have been made to carry out EB flexographic printing and EB offset printing, in which ink is cured by irradiation with active energy rays, particularly electron beams (EB), in flexible packaging printing (Patent Documents 1 and 2). In general, flexible packaging printing is performed by roll-to-roll printing, so the quick drying of the ink is important, and active energy ray curing printing methods have the environmental advantage of containing almost no solvent, as well as the energy saving and high productivity of shortening the drying process without using thermal energy. In addition, curing by electron beam irradiation has excellent transparency and does not require a photopolymerization initiator in the ink, so there is a reduced risk of odor of the printed matter and migration of initiator decomposition components to the contents, and is also excellent in terms of safety in terms of protecting the contents of the flexible packaging. However, electron beam irradiation equipment is expensive and large in size compared to ultraviolet irradiation equipment, so it is not installed on each printing cylinder like ultraviolet irradiation equipment, but is installed after the final printing cylinder to cure the ink all at once. 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 that imparts wet-on-wet printability to active energy ray-curable flexographic ink. According to this, a preprinted active energy ray-curable flexographic ink is printed on a film, dried to a gel state, and then a postprinted active energy ray-curable flexographic ink is printed, maintaining good trapping properties, and colors are applied over the film, and finally cured by EB irradiation. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2004-358788 A [Patent Document 2] WO 2019 / 69736 [Patent Document 3] Patent No. 5959855 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the technology disclosed in Patent Document 3, a removable solvent is added to the ink for the purpose of imparting wet-on-wet printability, so that the ink physical properties change not only when it is dried but also when it is stored or in the printing machine due to the evaporation of the solvent. As a result, there are problems with continuous printing stability, such as the density of process colors being easily changed, the density and halftone dot shape being unstable during continuous printing, and there being a large variation in density within the same printed surface.

[0011] Therefore, an object of the present invention is to provide a method for producing a surface-printed material that is excellent not only in suitability for wet-on-wet printing but also in continuous printing stability. [Means for solving the problem]

[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 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 ink that contains substantially no water or solvent. Effect of the Invention

[0013] According to the method for producing a printed matter of the present invention, it is possible to perform surface printing with excellent wet-on-wet printability and density stability. In addition, the obtained printed matter exhibits excellent hiding power and abrasion resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be specifically described below. In the present invention, "or more" means that the value is the same as or larger than the value indicated. Also, "or less" means that the value is the same as or smaller than the value indicated. Also, "(meth)acrylate" is a general 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 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 ink that contains substantially no water or solvent.

[0016] Generally, in surface printing, the 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, requires good fluidity 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 printing using the wet-on-wet process, if the tack (viscosity, cohesive strength) of the later-printed ink is not lower than that of the pre-printed ink, 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 high fluidity of white.

[0018] In the technology disclosed in Patent Document 3, a removable solvent is contained in the ink and dried between cylinders, which is peeled off in post-printing, preventing color mixing and realizing wet-on-wet printing suitability. However, because each ink contains a removable solvent, fluctuations in the ink 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 used as the base color, the image is generally solid, the amount of ink supplied is large, and high density is required, so fluctuations in the ink properties have little effect. However, for color inks such as process colors other than white and spot colors, 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 is the base color contains volatile water or solvent to give it high fluidity, and a drying process is provided before the post-printing, so that it is peeled off during the post-printing and color mixing is suppressed. Furthermore, the color inks such as the post-printing process colors and special colors contain substantially no volatile components, so there is little fluctuation in the ink physical properties, including viscosity, and the ink supply amount is less likely to fluctuate during continuous printing, improving the stability of print quality.

[0021] (Active energy ray curable ink) A preferred embodiment of the active energy ray-curable ink common to ink (A) and ink (B) will be described.

[0022] The active energy ray-curable ink in 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, the volumetric shrinkage during curing by irradiation with active energy rays 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 dicyclopentadiene tricyclodecane dimethanol di(meth)acrylate.

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

[0025] Also, monofunctional or polyfunctional (meth)acrylates not having an alicyclic skeleton can 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 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 the penta- or higher functional (meth)acrylate include dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ethylene oxide and propylene oxide adducts thereof.

[0031] The active energy ray-curable ink in 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 the resin may be a commercially available product or a synthetic product.

[0032] Acrylic resins can be obtained by polymerizing (meth)acrylate monomers alone or in combination in the presence of a polymerization initiator in an organic solvent. They can also be obtained by copolymerizing styrene, α-methyl-styrene, etc.

[0033] An example of a commercially available acrylic resin is the "Hi-Lo-Su" (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] In addition, 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 an anchor ink or overprint varnish that does not contain a color pigment.

[0039] The active energy ray-curable ink in the present invention, i.e., ink (A) and / or ink (B), preferably contains a wax. When the active energy ray-curable ink contains a wax, the scratch resistance and slipperiness 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. Among these, hydrocarbon waxes are preferred because of their excellent abrasion resistance.

[0041] Examples of the hydrocarbon wax include Fischer-Tropsch wax, polyethylene wax, polypropylene wax, paraffin wax, microcrystalline wax, etc. These waxes can 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. When the content of the wax is 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. When the content of the wax is 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 the flowability 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, a leveling agent, etc.

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

[0045] As the active energy ray-curable ink in the present invention, either flexographic ink or offset ink can be used. 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)) The ink (A) is a volatile active energy ray-curable ink containing water or a solvent.

[0048] Examples of the solvent in the 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 of the solvents may be used in combination. Water and a solvent may also be used in combination.

[0049] It is preferable that the ink (A) 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, it is given an appropriate quick-drying property. Furthermore, by being dried instantly in the subsequent drying step, it is 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. By making the content 10% by mass or more, more preferably 20% by mass or more, peeling off by ink (A) in post-printing after the drying process and color mixing are suppressed. Also, by making the content 50% by mass or less, more preferably 40% by mass or less, quick drying properties are imparted in the drying process.

[0051] Ink (A) has a viscosity of η at 25°C and 0.5 rpm according to the "Viscosity measurement method using a coaxial double cylindrical rotational viscometer" in JIS Z8803:2011. A It is preferable that η is 0.1 Pa·s or more and 5 Pa·s or less. A By setting the viscosity at 0.1 Pa·s or more and 5 Pa·s or less, and more preferably at 0.5 Pa·s or more and 2 Pa·s or less, the fluidity of the ink that will become a colorless or white undercolor will be 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 active energy ray-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 mass% or less.

[0055] Ink (B) has a viscosity of η at 25°C and 0.5 rpm according to the "Viscosity measurement method using a coaxial double cylindrical rotational viscometer" of JIS Z8803:2011. BIt is preferable that η is 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, and more preferably 40 Pa·s or more and 100 Pa·s or less, the fluctuation in the physical properties of color inks such as process colors and spot colors during printing can be kept small.

[0056] Also, η A and η B When the ink composition is within each of the preferred ranges, the tackiness of the inks can be well balanced, and continuous printing stability can be improved.

[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 an offset ink having a high viscosity and not containing a volatile component as the ink (B).

[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 machine) 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 printed material and faces a cylinder for transferring ink and a pressure cylinder. A center drum type printing press is suitable for a wet-on-wet printing process because it does not require a guide roll for transporting the film between the cylinders.

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

[0061] (base material) 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 a single type of polyethylene or polypropylene, or a laminate thereof.

[0063] The film may be subjected to a surface treatment such as burning treatment, 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 required for printing can be effectively obtained. In addition, 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 coated paper such as art paper, coated paper, or cast paper, or an uncoated paper such as fine paper, newsprint, or Japanese paper, or a synthetic paper, aluminum-coated paper, or other paper, a transparent ink may be used instead of a white ink as the ink (A).

[0066] The form of the substrate used in the method for producing a printed matter of the present invention may be 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 process) In each transfer step, ink is transferred to a receiving surface of a substrate.

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

[0069] In the transfer step, the method of transferring the ink to the printing surface is preferably flexographic printing for low-viscosity volatile ink, and 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 transferred to a substrate first to achieve surface printing. Surface printing can separate the hardened ink layer from the substrate itself, even in flexible packaging for packaging food or daily necessities, 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 that 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 the viscosity also increases significantly. This results in a higher viscosity and cohesive force than the ink on the post-press cylinder, suppressing peeling and color mixing.

[0073] Generally, the viscosity of the volatile ink is the above-mentioned η A and the viscosity of the non-volatile ink is within the range of the aforementioned η BIn normal wet-on-wet printing, if the viscosity is within the range, the volatile ink of the pre-printing is stripped off by the non-volatile ink of the post-printing, which has an overwhelmingly higher viscosity, resulting in color mixing, making normal printing impossible. However, by continuously printing the non-volatile ink of the post-printing after the drying process of the volatile ink of the present invention, stripping and color mixing due to the ink in the post-printing are suppressed, making it possible to perform continuous printing with stable quality.

[0074] (Overprint varnish transfer process) In the method for producing a printed matter of the present invention, it is preferable to include a 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 (overprint varnish transfer step) between the ink (B) transfer step and the irradiation step.

[0075] The active energy ray-curable overprint varnish protects the printed ink cured product and improves the scratch resistance of the surface-printed product. Depending on the properties of the varnish, it is also possible to impart gloss or matte properties to the design of the printed product.

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

[0077] In the method for producing a printed matter of the present invention, examples of the active energy ray source include ultraviolet rays (particularly LED-UV), electron beams, gamma rays, etc. Radiation such as electron beams and gamma rays generates high-energy secondary electrons in the irradiated material, excites the surrounding molecules, and generates reactive species such as radicals. When the irradiated material is an active energy ray curable ink, radicals are generated in the ink, radical polymerization proceeds, and a cured ink film is formed. In particular, electron beams generated by low acceleration voltage are preferably used because they have sufficient permeability for the ink film thickness of 10 μm or less, can provide the energy required for curing, do not require special qualifications when used, and are easy to handle.

[0078] The penetration depth of the electron beam is determined by the acceleration voltage, so 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, at which a sufficient dose penetrates the ink film. As the penetration depth increases, the dose given 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 material, but the greater the damage to the film. Therefore, the irradiation dose is preferably 10 kGy to 100 kGy, more preferably 20 kGy to 50 kGy. EXAMPLES

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

[0081] <Measurement and evaluation method> (1) Ink viscosity (η A , η B ) The viscosity was measured according to the "Viscosity measurement method using a coaxial double cylindrical rotational viscometer" of JIS Z8803:2011. A cylinder spindle No. 4 was attached to a B-type viscometer (BROOKFIELD DV-II) and the measurement conditions were 25°C and 0.5 rpm.

[0082] (2) Tack value 1.3 ml of ink was applied to the roller of an inkmeter ("INKOGRAPH" TYPE-V manufactured by Tester Sangyo Co., Ltd.), which 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: There is slight peeling of the white ink by the color ink printed after it, or the color ink has become slightly whitish and mixed. C: White ink is peeled off or mixed with the color ink printed later.

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

[0085] (5) Concentration stability In a continuous print run of 4000m, five samples were taken every 1000m 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 of 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 concentration difference is 0.1 or less. B: The maximum density difference is greater than 0.1 and equal to or less than 0.2. C: The maximum density difference is greater than 0.2.

[0086] (6) Removability of printed matter The solid white areas of the print were randomly selected to be 30mm x 18mm in size, and a piece of Nichiban Co., Ltd.'s "Cellotape" (registered trademark) No. 405 (width 18mm) was applied to them. The tape was then peeled off by hand and evaluated according to the following criteria. A: The ink film did not peel off. B: Part of the ink film was peeled off.

[0087] (7) Abrasion resistance of printed matter A randomly selected 3cm x 3cm area of ​​solid white material was rubbed back and forth with a human fingernail 20 times and evaluated according to the following criteria. A: No scratches from nails were found. B: Some ink peeling was observed along the nail marks.

[0088] <Printing unit> One of the following printing units was used as the printing units corresponding to the first to fifth cylinders of the printing press described below.

[0089] (1) Flexographic printing unit The printing plate was made using AWP DEW manufactured by Asahi Kasei, and the corresponding color image was exposed and developed to make the plate. The anilox roller was Nova Gold manufactured by Praxair Surface Technologies.

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

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

[0092] Starting from the upstream side of 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] The same image was used for printing methods 1 to 4, and the solid areas of the process colors were set to the specified print densities (black 1.7, cyan 1.4, magenta 1.3, yellow 1.1), after which 4,000 m of continuous surface-printed color printing was carried out 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 to obtain a printed matter.

[0095] [Print method 1] In printing method 1, a flexographic printing unit was installed on the first cylinder of a printing press (COMEXI CI-8), 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] [Print method 2] In printing method 2, all of the first to fifth cylinders of a printing press (UTECO ONYX XS) were used as flexographic printing units, and hot air drying was performed between each cylinder.

[0097] [Print 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 no drying was performed between the cylinders.

[0098] [Print method 4] In printing method 4, all of the first to fifth cylinders of the printing press (CI-8 manufactured by COMEXI) were offset printing units, and no drying was performed between the cylinders.

[0099] [Print method 5] In printing method 5, flexographic printing units were installed on the first and eighth cylinders of a printing press (COMEXI CI-8), 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 set on the eighth cylinder.

[0100] <Ink raw materials> (Pigments, pigment dispersants) White pigment: Typaque CR57 (manufactured by Ishihara Sangyo Kaisha, Ltd.) Ink pigment: MA-11 (Mitsubishi Chemical Corporation) Indigo pigment: Lionor Blue FG7330 (manufactured by Toyo Color Co., Ltd.) Red pigment: Lionol Red TT5701G (manufactured by Toyo Color Co., Ltd.) Yellow pigment: Lionol 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] (monomer) Monomer 1: Pentaerythritol triacrylate ("Miramer" (registered trademark) M340 manufactured by MIWON) Monomer 2: Trimethylolpropane triacrylate ethylene oxide adduct (MIWON "Miramer" (registered trademark) M3190) Monomer 3: (meth)acrylate having an alicyclic skeleton, tricyclodecane dimethanol diacrylate ("Miramer" (registered trademark) M262 manufactured by MIWON) 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 consisting 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 the carboxyl groups (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 (Wako Pure Chemical Industries, Ltd.) Solvent 1: 2-propanol (Wako Pure Chemical Industries, Ltd.), boiling point 83°C Solvent 2: propylene glycol (Wako Pure Chemical Industries, Ltd.), boiling point 188°C.

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

[0107] <Ink Preparation> The white ink was prepared using the formulation shown in Table 1, and the black, cyan, magenta, and yellow color inks were prepared using the formulation shown in Table 2. The ink ingredients listed below were weighed out and mixed using a bead mill for the flexo ink and a three-roll mill for the offset ink.

[0108] <Active energy ray curable overprint varnish> EB varnish: Sun Chemical OPV EB UMatt UQ1601.

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

[0110] [Table 1]

[0111] [Table 2]

[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 of the post-printing, and good printability was demonstrated. Furthermore, the concentration of the color ink was stable even during continuous printing.

[0114] Compared to Example 1, in Example 2 in which the amount of solvent in the ink (A) was small, 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) as compared with Example 1, good printability and continuous printing stability were also exhibited.

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

[0117] In Comparative Example 1, in which ink (A) was also used for the color inks, good printability was shown for all colors by performing inter-cylinder drying for each color, but the density fluctuation during continuous printing was large and the 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) including white ink was used. In Comparative Example 2, the white ink and the color inks of the previous printing were picked up by the rear cylinder, causing color mixing, and the color inks did not adhere properly, resulting in failure to print normally.

[0121] In Comparative Examples 3 and 4, only offset type ink (B) was used, including white ink. In Comparative Example 3, the white ink was taken up by the rear cylinder, causing color mixing. In addition, the color ink 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] [Table 3]

[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. In addition, 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 overprint varnish, white ink 1, color ink set 1, and substrate 3 (OPP film) as substrate. As in Example 1 using printing method 1, the printability and hiding power were good, and the color ink concentration was stable. Furthermore, the overprint varnish was applied well, with no peeling or peeling due to abrasion. The results are shown in Table 4.

[0126] [Table 4]

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.

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