Printing method

Abstract

A method for producing a printed matter having two or more printed layers is provided, which is excellent in productivity and can suppress deterioration and discoloration of a substrate due to irradiation with electron beams, and can realize a wide range of hues. [Solution] A method for producing a printed matter having a first printing layer and a second printing layer formed sequentially on a substrate, the method comprising: step 1 of applying one or more types of active energy ray-curable offset printing inks to the surface of the substrate to form a first ink coating; step 2 of applying one or more types of active energy ray-curable flexographic printing inks to the surface of the substrate on which the first ink coating obtained in step 1 has been formed to form a second ink coating; and step 3 of irradiating with an electron beam after step 2 to simultaneously cure the first ink coating and the second ink coating, thereby forming a first printing layer consisting of the cured product of the first ink coating and a second printing layer consisting of the cured product of the second ink coating.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a method for producing a printed matter. [Background technology]

[0002] Demand for packaging materials, primarily used in the food and daily necessities sectors, is expected to continue to grow in line with global population growth. Currently, gravure printing is the mainstream method for printing flexible packaging materials. Gravure printing produces prints with a vivid appearance. However, gravure printing uses inks that contain large amounts of solvent, which requires a large amount of energy to dry the ink solvent and treat the exhaust, placing a heavy burden on the environment. Furthermore, market needs in recent years have shifted from traditional mass production and mass consumption to small lots, a wide variety of products, and short delivery times. Gravure printing, on the other hand, is a printing method suited to large-lot printing, but the cost of printing plates and plate-making is expensive, which tends to increase the production costs of printed materials. Therefore, offset printing, which has low plate and plate-making costs, is easily adaptable to small lots and short delivery times, and is therefore advantageous in terms of cost of printed materials, has been attracting attention in recent years.

[0003] Offset printing is a printing method that is widely used as a system for supplying printed materials at high speed, in large quantities, and at low cost, and the ink used during printing may be either solvent-based or non-solvent-based. In recent years, from the perspectives of environmental issues and responding to carbon neutrality, active energy ray-curable inks that cure instantly upon irradiation with active energy rays have been attracting attention, and offset printing using such inks is also being studied.

[0004] In the production of packaging materials used in fields such as food and daily necessities, the printing process is generally carried out by high-speed printing using a roll-to-roll method. From the viewpoint of increasing productivity in the printing process, the quick-drying property of the ink is important. Therefore, offset printing using active energy ray-curable ink is expected to be used in the production of printed materials used in packaging materials. For example, Patent Document 1 discloses a method for producing packaging materials, which includes a step of printing ultraviolet-curable or electron beam-curable ink on paper or plastic film by offset printing.

[0005] In recent years, among active energy ray-curable inks, UV-curable inks containing photopolymerization initiators and curing systems for UV-curable inks have become mainstream on the market. UV-curable inks do not contain volatile components and cure instantly when irradiated with UV energy rays. This means that the drying process can be shortened without using thermal energy, which not only has environmental benefits but also has the advantages of energy savings and high productivity.

[0006] However, for packaging materials used in the fields of food and daily necessities, it is undesirable to add a photopolymerization initiator to the ink in order to prevent contamination of the contents due to migration, etc. Therefore, as a curing method using active energy rays that does not contain a photopolymerization initiator, an electron beam curing method that does not require a photopolymerization initiator is expected to become more widespread.

[0007] Furthermore, when using an actinic radiation-curable ink to form a multilayer printed matter having two or more printed layers on a substrate, a typical method involves applying an ink to the substrate and curing it to form a first printed layer, and then applying and curing another ink on the first printed layer made of the cured ink to form a second printed layer. For example, Patent Document 2 discloses a printing method using an offset printing machine in which UV (ultraviolet) curable ink is applied to a substrate, the ink is cured by UV irradiation, and then post-processing such as silk screen printing or flexographic printing is performed. However, from the perspective of production efficiency, improvements are desired for methods that require curing each time the ink is applied. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-358788 [Patent Document 2] International Publication No. 2014 / 083722 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, the electron beam curing method in the production of printed matter has the advantage that it does not require the addition of a photopolymerization initiator to the active energy beam-curable ink. However, because the electron beam curing method has a higher irradiation energy than ultraviolet light, it is prone to problems such as damage to the substrate and discoloration of the substrate. When actually printing on a substrate, there are always non-printed areas at the edges of the substrate. Such non-printed areas are particularly susceptible to damage from electron beams, making the problems of substrate discoloration and substrate deterioration unavoidable. From the perspective of industrializing the production of printed matter, substrate discoloration and substrate deterioration cause reduced productivity, and therefore improvement is desired.

[0010] Furthermore, for example, when electron beams are used as a curing method in the production of a printed matter having a first printed layer and a second printed layer in that order on a substrate, there is a limit to the range of hues that can be achieved in the printed matter. One reason for the narrowing of the hue (color gamut) is thought to be that the first printed layer, which is formed by curing ink with electron beams, is affected by the electron beams irradiated when the second printed layer is formed. From the perspective of production efficiency, improvements are desired for the method of curing ink each time it is applied.

[0011] Furthermore, in the manufacture of surface-printed printed materials, a second printed layer may be formed using varnish for the purpose of surface protection after the formation of the first printed layer. In response to this, a method of improving the color tone can be considered by providing a plastic film (sealant) instead of the second printed layer (a surface protective layer formed using varnish). However, printed materials provided with a plastic film as a surface protective layer are undesirable from the standpoints of recycling and CO2 reduction.

[0012] In view of these circumstances, the present invention provides a method for producing a printed matter having two or more printed layers, which suppresses deterioration and discoloration of a substrate due to irradiation with an electron beam, can achieve a wide range of hues, and is highly productive. [Means for solving the problem]

[0013] The present inventors have conducted extensive research into methods for producing printed materials using actinic radiation-curable inks. As a result, they have found that forming two or more ink coatings on a substrate by wet trapping and simultaneously curing these ink coatings with electron beams can solve the above-mentioned problems without discoloring the substrate and with a wide color gamut. Here, "wet trapping (also referred to as wet-on-wet)" refers to a printing method in which one color of ink is applied and then immediately overlaid with another color of ink. In wet trapping printing, the underlying ink is applied while the other color of ink is still wet or uncured, making the combination of inks important for preventing trapping defects. The present inventors have found that using an offset printing ink as the underlying ink and a flexographic printing ink as the upper ink layer can achieve good wet trapping printing without trapping defects. Furthermore, they discovered that when a printed matter is produced by printing offset ink using wet trapping, and then printing flexographic varnish and curing it using an electron beam, there is no discoloration of the substrate, and the resulting printed matter has coating film properties equivalent to those of a printed matter containing only varnish and a sealant, leading to the completion of the present invention.

[0014] That is, embodiments of the present invention relate to the following: However, the present invention is not limited to the following embodiments and includes various embodiments. <1> A method for producing a printed matter having a first printed layer and a second printed layer sequentially on a substrate, comprising: Step 1: applying one or more active energy ray-curable offset printing inks to the surface of a substrate to form a first ink coating film; Step 2 of applying one or more active energy ray-curable flexographic printing inks to the surface of the substrate on which the first ink coating film obtained in step 1 has been formed, to form a second ink coating film; a step 3 after the step 2 in which an electron beam is irradiated to simultaneously cure the first ink coating film and the second ink coating film, thereby forming a first printed layer made of the cured product of the first ink coating film and a second printed layer made of the cured product of the second ink coating film; A method for producing a printed matter comprising the steps of:

[0015] <2> In the step 3, the acceleration voltage of the electron beam is 50 to 250 kV. <1> A method for producing a printed matter according to claim 1.

[0016] <3> In the step 3, the irradiation dose of the electron beam is 10 to 60 kGy. <1> or <2> A method for producing a printed matter according to claim 1.

[0017] <4> The printing speed is 50 to 300 m / min. <1> ~ <3> A method for producing a printed matter according to any one of the above.

[0018] <5> The method of claim 1, wherein the method does not include a step of irradiating the active energy ray to cure the active energy ray-curable offset printing ink between the steps 1 and 2. <1> ~ <4> A method for producing a printed matter according to any one of the above.

[0019] <6> The active energy ray-curable offset printing ink contains a resin, a polyfunctional (meth)acrylate, and a colorant. <1> ~ <5> A method for producing a printed matter according to any one of the above.

[0020] <7> The active energy ray-curable flexographic printing ink includes an active energy ray-curable white ink for flexographic printing. <1> ~ <6> A method for producing a printed matter according to any one of the above.

[0021] <8> The active energy ray-curable flexographic printing ink contains an active energy ray-curable flexographic printing varnish. <1> ~ <6> A method for producing a printed matter according to any one of the above.

[0022] <9> The substrate is a paper substrate or a transparent film substrate. <1> ~ <8> A method for producing a printed matter according to any one of the above.

[0023] <10> The thickness of the paper base material is 50 μm to 150 μm. <9> A method for producing a printed matter according to claim 1.

[0024] <11> The transparent film substrate has a thickness of 1 μm to 35 μm. <9> A method for producing a printed matter according to claim 1.

[0025] <12> The printed matter is used for packaging materials, <1> ~ <11> A method for producing a printed matter according to any one of the above. [Effects of the Invention]

[0026] According to an embodiment of the present invention, there is provided a method for producing a printed matter having two or more printed layers, which suppresses deterioration and discoloration of a substrate due to irradiation with an electron beam, can achieve a wide range of hues, and is highly productive. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and the present invention also includes embodiments that are implemented within the scope of the present invention.

[0028] One embodiment of the present invention relates to a method for producing a printed matter having a first printed layer and a second printed layer formed in that order on a substrate. The method for producing a printed matter of this embodiment includes a printing step of sequentially applying an active energy ray-curable offset printing ink and an active energy ray-curable flexographic printing ink to the surface of the substrate, and a curing step of irradiating an ink coating film having a structure of substrate / active energy ray-curable offset printing ink / active energy ray-curable flexographic printing ink obtained in the printing step with an electron beam.

[0029] More specifically, the method for producing a printed matter of the present embodiment is a method for producing a printed matter having a first printed layer and a second printed layer sequentially on a substrate, the method comprising: Step 1: applying one or more active energy ray-curable offset printing inks to the surface of a substrate to form a first ink coating film; Step 2 of applying one or more active energy ray-curable flexographic printing inks to the surface of the substrate on which the first ink coating film obtained in step 1 has been formed, to form a second ink coating film; a step 3 after the step 2 in which an electron beam is irradiated to simultaneously cure the first ink coating film and the second ink coating film, thereby forming a first printed layer made of the cured product of the first ink coating film and a second printed layer made of the cured product of the second ink coating film; The present invention relates to a method for producing a printed matter having the above-mentioned steps.

[0030] According to the method for producing a printed matter of this embodiment, the active energy ray-curable offset printing ink and the active energy ray-curable flexographic printing ink are cured simultaneously, which makes it possible to easily improve productivity and easily suppress damage to the substrate, thereby suppressing defects such as color change and deterioration of the substrate caused by irradiation with electron beams.

[0031] The method for producing a printed matter of this embodiment may include other steps in addition to the printing step and curing step, as necessary. For example, it may further include a step of subjecting the substrate to surface treatment, such as corona discharge treatment or plasma treatment, prior to the printing step. In this specification, the term "step" is not limited to a form implemented independently of other steps, and may include other steps as long as the intended purpose is achieved in that step. However, the method for producing a printed matter of this embodiment is characterized in that the printing step does not include a step of irradiating active energy rays to cure the active energy ray-curable offset printing ink between steps 1 and 2.

[0032] In the method for producing a printed matter of this embodiment, the substrate is not particularly limited. For example, the substrate may be one selected from the group consisting of paper, plastic film, and metal, or a combination thereof. The paper may be, for example, art paper, coated paper, cast paper, synthetic paper, or newsprint. The plastic film may be, for example, polyolefins such as polyethylene terephthalate, polyethylene, and polypropylene, or polyamides. Furthermore, the metal may be aluminum, zinc, or copper, and may be in the form of a metal film or a metal-deposited film. In some embodiments, the substrate may be paper, paper laminated with a plastic film, or paper with a metallized film. In some embodiments, the substrate may be a plastic film or a plastic film with a metallized film. Among these, paper or a transparent plastic film (also called a transparent film) can be preferably used as the substrate.

[0033] The printed matter may be either front-printed or reverse-printed. The substrate can be selected depending on the desired structure of the printed matter. When the printed matter is surface-printed, the substrate may be paper, a plastic film, or a metallized film. When the substrate is paper, the first printed layer preferably includes a pattern such as a picture or letters formed using colored ink, and the second printed layer may be a transparent layer formed using varnish to serve as a surface protective layer. When the substrate is a plastic film, the first printed layer preferably includes a pattern formed using colored ink and white ink, and the second printed layer may be a surface protective layer formed using varnish.

[0034] When the printed matter is reverse-printed, the substrate may be a plastic film, preferably a transparent film. When the substrate is a plastic film, the first printed layer preferably includes a pattern such as a picture or letters formed using a colored ink, and the second printed layer may be a base layer formed using a white ink.

[0035] The thickness of the substrate is not particularly limited. For example, when paper is used alone as the substrate (referred to as a paper substrate), the thickness of the paper substrate may be preferably 50 μm to 150 μm, more preferably 70 μm to 120 μm, and even more preferably 90 μm to 100 μm. When a plastic film (transparent film) is used alone (referred to as a transparent film substrate), the thickness of the transparent film substrate may be preferably 1 μm to 35 μm, more preferably 5 μm to 25 μm, and even more preferably 10 μm to 20 μm. When the thickness of the substrate is adjusted to the above range, deterioration of the substrate due to electron beams can be easily suppressed. Furthermore, a decrease in the curing speed of the ink film can be easily suppressed.

[0036] In the method for producing a printed matter of this embodiment, one or more types of actinic ray-curable flexographic printing ink are printed on the uncured ink coating without curing the actinic ray-curable offset printing ink coating printed on the substrate in step 1. Therefore, in step 2, it is necessary to prevent the actinic ray-curable flexographic printing ink (hereinafter referred to as flexographic ink) from migrating to the actinic ray-curable offset printing ink (hereinafter referred to as offset ink) coating. Therefore, it is preferable to appropriately adjust the relationships between the various physical property values ​​of the offset ink and the flexographic ink.

[0037] Generally, when an upper ink film is formed on an uncured lower ink film, the viscosity of the ink forming the upper ink film is set lower than the viscosity of the ink forming the lower ink film. Adjusting the viscosity of each ink in this manner can prevent problems such as ink migration and color mixing. In contrast, the offset ink and flexographic ink used in this embodiment have significantly different viscosities, with the viscosity of the offset ink being significantly higher than that of the flexographic ink. Therefore, after performing step 1 using the offset ink, step 2 can be successfully performed using the flexographic ink.

[0038] In some embodiments, from the viewpoint of wettability to the substrate, the surface tension X1 at 25°C of the offset ink used in step 1 may be preferably 30 to 50 mN / m, more preferably 35 to 45 mN / m. On the other hand, the surface tension X2 at 25°C of the flexographic ink used in step 2 may be preferably 30 to 50 mN / m, more preferably 35 to 45 mN / m. The surface tensions X1 and X2 are values ​​obtained by measuring the cured film of each ink at 25°C, and X2 is preferably smaller than X1.

[0039] In some embodiments, the surface free energy Y1 at 25°C of the offset ink used in step 1 may be preferably 30 to 50 mN / m, more preferably 35 to 45 mN / m. On the other hand, the surface free energy Y2 at 25°C of the flexographic ink used in step 2 may be preferably 30 to 50 mN / m, more preferably 35 to 45 mN / m. The surface tensions Y1 and Y2 are values ​​obtained by measuring a cured film of each ink at 25°C, and Y2 is preferably smaller than Y1.

[0040] From the viewpoint of smoothly promoting the curing of the offset ink coating film and the flexographic ink coating film, it is preferable to appropriately adjust the thickness of each coating film, the composition of the ink, etc. In some embodiments, the thickness of the offset ink coating (uncured) may be preferably 1 to 10 μm, more preferably 2 to 7.5 μm, and even more preferably 3 to 5 μm, while the thickness of the flexographic ink coating may be preferably 1 to 15 μm, more preferably 2 to 10 μm, and even more preferably 3 to 7 μm.

[0041] In the method for producing a printed matter of this embodiment, there are no particular limitations on the actinic ray-curable offset printing ink used in step 1 and the actinic ray-curable flexographic ink for offset printing used in step 2. Various offset inks and flexographic inks known in the art can be used, but specific examples of inks that can be suitably used are described below.

[0042] (offset ink) In some embodiments, the actinic ray-curable offset printing ink (offset ink) used in step 1 contains a resin, a polymerizable compound, and a colorant. The resin preferably includes at least one selected from the group consisting of allyl resin, diallyl phthalate resin, rosin, maleated rosin, acrylated rosin, rosin-modified resin, epoxy resin, polyester resin, polyurethane resin, alkyd resin, and petroleum resin.

[0043] As the polymerizable compound, a polyfunctional (meth)acrylate compound can be suitably used. Specific examples of the polyfunctional (meth)acrylate compound include dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, and trimethylolpropane ethoxy triacrylate.

[0044] The colorant may be either a pigment or a dye, but a pigment is preferably used. The pigment may be, for example, a yellow pigment, a red pigment, a cyan pigment, an ink pigment, or a white pigment. One of these pigments may be used alone, or two or more may be used in combination. The offset ink may further contain various additives such as an anti-wear aid, a lubricant, a pigment dispersant, and a polymerization inhibitor, as required.

[0045] In some embodiments, when an offset ink composed of a combination of the resins exemplified above and a polyfunctional (meth)acrylate compound is used, the ink tends to cure well even when the electron beam irradiation energy is reduced. In some embodiments, the offset ink used in step 1 preferably does not substantially contain solvents such as water or organic solvents. In this specification, "substantially free of solvent" means that no intentionally added solvent is contained, and does not mean that solvents mixed in during the ink manufacturing process or the like are completely excluded. The solvent content, based on the total mass of the offset ink, may be preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. The solvent content is particularly preferably 0.5% by mass or less, and most preferably 0% by mass. When the offset ink is substantially free of solvent, changes in the ink viscosity can be easily suppressed, and coating film formation can be carried out satisfactorily.

[0046] The offset ink used in step 1 can be prepared according to methods well known in the art. For example, the offset ink can be prepared by adding a pigment, a (meth)acrylate compound, and a diallyl phthalate resin to a kneader, mixing them together, and then dispersing the resulting mixture in a disperser. Various additives, such as anti-wear agents, lubricants, pigment dispersants, and polymerization inhibitors, may be added as needed. When additives are used, they can be added to the kneader along with the pigment and other components in the previously described preparation method. Alternatively, the offset ink can be prepared by blending the pigment and other components in advance, pre-mixing the mixture, and then adding it to the kneader. Furthermore, as with the resin varnish described in the examples below, components other than the pigment can be added in the form of a varnish prepared by dissolving each component in a polymerizable compound such as a (meth)acrylate compound.

[0047] In some embodiments, the offset ink may be white ink. In other embodiments, the offset ink may be colored ink such as yellow, red, indigo, or black ink. In still other embodiments, the offset ink may be transparent ink (varnish). In step 1, one or more of these offset inks may be used in combination.

[0048] (Flexographic ink) In some embodiments, the actinic radiation-curable flexographic printing ink (flexographic ink) used in step 2 contains at least a polymerizable compound, and preferably further contains a resin and various additives. Examples of various additives include a wear resistance aid, a lubricant, a pigment dispersant, and a polymerization inhibitor. The flexographic ink may further contain a colorant such as a white pigment, as needed. In some embodiments, the flexographic ink may be a white ink. In other embodiments, the flexographic ink may be a transparent ink (flexographic varnish).

[0049] The polymerizable compound constituting the flexographic ink is not particularly limited. In one embodiment, a polymerizable compound having a molecular weight of 100 to 6,000 can be suitably used. Specific examples of the polymerizable compound include polyfunctional (meth)acrylate compounds such as trimethylolpropane ethoxy triacrylate, tripropylene glycol diacrylate, and glycerin propoxy triacrylate. These compounds can be suitably used alone or in combination of two or more.

[0050] Resins that can be used in flexographic inks may be either thermosetting or thermoplastic. The weight-average molecular weight of the resin is preferably 1,000 to 1,000,000, more preferably 10,000 to 100,000. Specific examples of resins include polyester resins, polyvinyl chloride resins, poly(meth)acrylic acid ester resins, epoxy resins, polyurethane resins, petroleum (based) resins, cellulose derivatives (e.g., ethyl cellulose, cellulose acetate, nitrocellulose), vinyl chloride-vinyl acetate copolymers, polyamide resins, polyvinyl acetal resins, diallyl phthalate resins, polyamide resins, polyvinyl acetal resins, and synthetic rubbers such as butadiene-acrylonitrile copolymers. These resins may be used alone or in combination.

[0051] The flexographic ink used in step 2 can be produced according to methods well known in the art. For example, flexographic varnish can be obtained by dissolving various additives, including a polymerization inhibitor, in a polymerizable compound. In some embodiments, a flexographic varnish containing a polymerizable compound having a molecular weight of 100 to 6,000 and an additive, including a polymerization inhibitor, can be suitably used. The content of the polymerization inhibitor may be 0.01 to 1 part by mass relative to the total mass of the flexographic varnish. In some embodiments, the viscosity of the flexographic varnish at 25°C is preferably adjusted to 100 to 500 Pa·s.

[0052] In the printing step, the printing speed may be preferably 50 to 300 m / min, more preferably 100 to 250 m / min, and even more preferably 120 to 230 m / min. The printing speed means the moving speed of the substrate, and can be adjusted as appropriate.

[0053] The method for producing a printed product according to this embodiment does not include a step of curing the offset ink coating by irradiating it with active energy rays between the printing steps of step 1 and step 2. Instead, in step 3 (curing step), the offset ink coating and the flexographic ink coating are simultaneously cured by irradiating them with electron beams. This facilitates improved productivity. Electron beam irradiation can be performed using a method well known in the art. For example, electron beam irradiation can be performed using an electron beam irradiation device commonly used in the art.

[0054] The offset ink and flexographic ink used in this embodiment are actinic ray-curable, and therefore can be cured by irradiation with not only electron beams but also other actinic ray types such as ultraviolet rays. However, when ultraviolet rays are used, a photopolymerization initiator must be added to the ink. Photopolymerization initiators are likely to cause migration, an issue for which improvement is sought in fields such as food packaging materials. On the other hand, the method for producing printed matter of this embodiment uses electron beams, which do not require a photopolymerization initiator, and therefore has the advantage of being excellent in productivity and easily providing printed matter that can be used suitably in fields where suppression of migration is desired.

[0055] When an ink coating is irradiated with an electron beam, a radical polymerization reaction proceeds within the ink coating, forming a cured ink coating (printed layer). The acceleration voltage during electron beam irradiation affects the penetration depth of the electron beam, and the irradiation dose affects the amount of radicals generated in the ink coating. Therefore, if the acceleration voltage is too low, the electron beam will not reach the depths of the ink coating, making it more likely that curing will be uneven between the surface and depths of the ink coating. Furthermore, if the irradiation dose is too low, the amount of radicals generated will be insufficient, and curability will tend to be poor. On the other hand, if the acceleration voltage and irradiation dose are too high, the impact on the substrate will be significant, making the substrate more susceptible to damage. Therefore, it is preferable to adjust the electron beam irradiation taking into account the curability of the ink and damage to the substrate.

[0056] In some embodiments, the acceleration voltage of the electron beam may be preferably 50 to 250 kV, more preferably 70 to 150 kV, and even more preferably 90 to 120 kV. The exposure dose of the electron beam may be preferably 10 to 60 kGy, more preferably 15 to 50 kGy, and even more preferably 20 to 40 kGy. The electron beam irradiation is preferably carried out at an acceleration voltage of 50 to 250 kV and an exposure dose of 10 to 60 kGy. When the acceleration voltage and exposure dose are adjusted within the above ranges, the electron beam can achieve an appropriate penetration depth, allowing the electron beam to reach deep into the ink coating, thereby efficiently curing the ink coating. In addition, damage to the substrate can be easily suppressed.

[0057] In the electron beam irradiation step (the ink coating curing step), the movement speed (also referred to as the printing speed) of the substrate carrying the ink coating may be preferably 50 to 300 m / min, more preferably 100 to 200 m / min, and even more preferably 150 to 200 m / min. The electron beam irradiation step (curing step) is generally carried out in a nitrogen atmosphere to prevent the ink curing from being inhibited by oxygen. Since the electron beam irradiation step (curing step) is carried out in a printing press equipped with an electron beam generator, the interior of the printing press system is maintained in a nitrogen atmosphere. In the production method of this embodiment, in addition to irradiating the electron beam in a nitrogen atmosphere, the influence of oxygen can be suppressed and the curing of the ink coating on the substrate can be favorably promoted by adjusting the printing speed within the above range.

[0058] In some embodiments, it is preferable to adjust the residual oxygen content in the system to 300 ppm or less. A residual oxygen content of 300 ppm or less is a general requirement in conventional printing methods. In the production method of this embodiment, even if the residual oxygen content in the system exceeds 300 ppm, for example, is about 800 ppm, the ink curing can be favorably promoted by adjusting the irradiation conditions and the ink composition.

[0059] The printed matter obtained by the manufacturing method of this embodiment may have a configuration of, for example, paper / a printed layer of offset colored ink / a printed layer of flexo varnish. As another example, the printed matter may have a configuration of transparent film / a printed layer of offset colored ink and a printed layer of offset white ink / flexo varnish. The printed matter can be used for various purposes. For example, the printed matter can be suitably used as packaging material. [Example]

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0061] <1> Preparation of each ink (1) Offset ink preparation example (Preparation of Resin Varnish) The following resin, polymerization inhibitor, and polymerizable compound were mixed in the following ratios and heated to 95°C, and the resin and polymerization inhibitor were dissolved in the polymerizable compound to obtain Resin Varnish 1. The viscosity of Resin Varnish 1 was adjusted to 300 Pa s at 25°C. Resin: Daiso DAP A (Osaka Soda Co., Ltd.) 30 parts by weight Polymerization inhibitor: TBHQ FINE (t-butyl hydroquinone, manufactured by Kusumoto Chemicals Co., Ltd.) 1 part by mass Polymerizable compound: dipentaerythritol hexaacrylate (MIRAMER M600 manufactured by MIWON Co., Ltd.) 69 parts by mass

[0062] (Various offset inks) Various offset inks were obtained by mixing the previously prepared resin varnish 1, (meth)acrylate compounds Monomer 1, Monomer 2, and Monomer 3, pigment, additives (lubricant and pigment dispersant), and polymerization inhibitor in the blending ratios shown in Table 1. The amount of polymerization inhibitor added when preparing the offset ink was adjusted so that the total amount, including the amount of polymerization inhibitor contained in the resin varnish, was 1 part by mass. Specifically, the amounts of polymerization inhibitor listed in Table 1 were added.

[0063] [Table 1]

[0064] Details of each component listed in Table 1 are as follows: Varnish: Varnish 1 prepared previously Monomer 1: Dipentaerythritol hexaacrylate (MIWON MIRAMER M600) Monomer 2: Ditrimethylolpropanetetraacrylate (EBECRYL 1142, manufactured by Daicel Allnex Co., Ltd.) Monomer 3: Trimethylolpropane triacrylate ethylene oxide adduct (MIWON MIRAMER M3160) Pigments: as described below Anti-wear additive: KTL-4N (PTFE wax, manufactured by Kitamura Co., Ltd.) Pigment dispersant: Solsperse 24000 GR (manufactured by Lubrizol Corporation) Polymerization inhibitor: TBHQ FINE (t-butyl hydroquinone, manufactured by Kusumoto Chemicals Co., Ltd.)

[0065] The specific color offset inks are as follows: (yellow ink) Lionol Yellow 1314 (manufactured by Toyo Color Co., Ltd.) was used as the pigment, and the components were blended according to the blending ratios in Table 1. The blend was then milled using a three-roll mill until the particle size measured by a dispersion particle measuring device (grind meter) was 7.5 microns or less, to obtain a yellow ink.

[0066] (Red ink) Lionol Red 5620 (manufactured by Toyo Color Co., Ltd.) was used as the pigment, and the components were blended according to the blending ratios in Table 1. The blend was then milled using a three-roll mill until the particle size measured by a dispersion particle measuring device (grind meter) was 7.5 microns or less, to obtain a crimson ink.

[0067] (indigo ink) Lionol Blue FG7330 (manufactured by Toyo Color Co., Ltd.) was used as the pigment, and the components were blended according to the blending ratios in Table 1. The blend was then milled using a three-roll mill until the particle size measured by a dispersion particle measuring device (grind meter) was 7.5 microns or less, to obtain an indigo ink.

[0068] (Black ink) MA-11 (manufactured by Mitsubishi Chemical Corporation) was used as the pigment, and the components were blended according to the blending ratios in Table 1. The blend was then milled using a three-roll mill until the particle size measured by a dispersed particle measuring device (grind meter) was 7.5 microns or less, to obtain a black ink.

[0069] (white ink) Using Typec CR50-2 (manufactured by Ishihara Sangyo Kaisha Ltd.) as the pigment, the components were blended according to the blending ratios in Table 1, and the mixture was milled using a three-roll mill until the particle size measured by a dispersed particle measuring device (grind meter) was 7.5 microns or less, to obtain a white ink.

[0070] (2) Preparation example of flexographic ink (varnish) Monomer 3, Monomer 4, and Monomer 5 were mixed as polymerizable compounds, with an anti-wear aid and a polymerization inhibitor in the blending ratios shown in Table 2. This mixture was stirred at a temperature of 50°C for 1 hour using a disper blade at a rotation speed of 1000 rpm to obtain a flexonic varnish.

[0071] [Table 2]

[0072] Details of each component listed in Table 2 are as follows: Monomer 3: Trimethylolpropane ethoxy triacrylate (MIWON, MIRAMER M3160) Monomer 4: Tripropylene glycol diacrylate (manufactured by Daicel Allnex Co., Ltd., TPGDA) Monomer 5: Glycerin propoxytriacrylate (manufactured by Daicel Allnex Co., Ltd., OTA480) Anti-wear additive: KTL-4N (PTFE wax, manufactured by Kitamura Co., Ltd.) Polymerization inhibitor: TBHQ FINE (t-butyl hydroquinone, manufactured by Kusumoto Chemicals Co., Ltd.)

[0073] The viscosity, surface tension, and surface free energy of each of the electron beam (EB) curable offset inks and flexographic inks prepared as described above were measured according to the methods described below. The results are shown in Table 3. <Viscosity> The viscosity was measured at 25°C using an E-type viscometer in accordance with JIS Z8803:2011.

[0074] <Surface tension> A 0.1 ml droplet of ink or varnish was placed on a glass substrate and measured at an ambient temperature of 25°C using a surface tensiometer (KRUSS double titration handy contact angle and surface free energy analyzer MSA).

[0075] <Surface free energy> A 0.1 ml droplet of ink or varnish was placed on a glass substrate and measured at an ambient temperature of 25°C using a surface free energy analyzer (KRUSS double titration handy contact angle and surface free energy analyzer MSA).

[0076] [Table 3]

[0077] <2> Print production Example 1 Using a lithographic and flexographic hybrid printing press (CI-8, manufactured by COMEXI), offset inks of black, indigo, red, and yellow were placed on cylinders 1 to 4, respectively, and flexographic ink (varnish) was placed on cylinder 8. Kintokata Art Paper (Oji Paper Co., Ltd.) was used as the paper substrate, and T414 (Kinyosha Co., Ltd.) was used as the blanket to print each of the inks shown in Table 4 using a wet trapping printing method. In this printing process, a design was printed that had a single solid color area and areas where all the color inks used were overcoated. The printing conditions are as follows: (Printing conditions) Ink feed rate: 50%, Oscillating roller and ink fountain chiller set temperature: 28℃ Pressure cylinder chiller temperature setting: 30℃ Printing speed: 100m / min Residual oxygen content: 200 ppm After printing all the inks, the inks were cured by irradiating them with electron beams using the electron beam irradiation device attached to the printing press. The electron beam irradiation conditions were an acceleration voltage of 110 kV and an exposure dose of 30 kGy.

[0078] Examples 2 to 12 Printing was carried out in the same manner as in Example 1, except that the inks used during printing were changed to the ink combinations shown in Table 4. Furthermore, the inks were cured in the same manner as in Example 1 to obtain printed matter. The printing conditions and the electron beam irradiation conditions during curing were all the same as in Example 1.

[0079] (Comparative Examples 1 to 3) In the method for producing a printed matter of Example 1, instead of using a wet trapping printing method, an electron beam was irradiated after printing of the offset ink to cure the ink (curing step 1), and then flexographic ink was printed. Prints were obtained by printing each of the inks shown in Table 4 under the same printing conditions as in Example 1, except for this. The electron beam irradiation conditions in the curing step 1 were an acceleration voltage of 110 kV and an exposure dose of 30 kGy. The electron beam irradiation conditions after printing of the flexographic ink (electron beam irradiation conditions in curing step 2) were the same as in Example 1, that is, an acceleration voltage of 110 kV and an exposure dose of 30 kGy.

[0080] (Comparative Examples 4 to 8) Printing was performed using each ink shown in Table 4 under the same printing conditions as in Example 1 to obtain a printed product. Specifically, a first ink coating was formed using offset ink alone, and the first ink coating was irradiated with an electron beam without applying flexographic ink, thereby obtaining a printed product. The electron beam irradiation conditions were the same as in Example 1, with an acceleration voltage of 110 kV and an exposure dose of 30 kGy.

[0081] Comparative Example 9 Black, indigo, magenta, and yellow offset inks were prepared in the same manner as in Example 1. 10 parts of Omnirad379EG (manufactured by IGM) were added as a photopolymerization initiator to 100 parts of each offset ink to prepare ultraviolet-curable offset inks of each color. Further, the same flexo varnish as in Example 1 was prepared, and 10 parts of Omnirad379EG (manufactured by IGM) was added as a photopolymerization initiator to 100 parts of the flexo varnish to prepare an ultraviolet-curable flexo varnish. 0.4 ml of each of the offset inks and varnishes obtained as described above was applied to an RI tester, spread evenly, and then applied sequentially to Kintokata Art Paper (Oji Paper Co., Ltd.). Next, in the curing step, the ink was cured by irradiating the ink coating with ultraviolet light, and a printed matter having the same structure as Example 1 was obtained, as shown in Table 4. The curing step by irradiation with ultraviolet light was carried out using a metal halide lamp under irradiation conditions of 128 W.

[0082] Example 13 A lithographic and flexographic hybrid printing press (CI-8, manufactured by COMEXI) was used, and offset inks of white, black, indigo, red, and yellow were applied to cylinders 1 to 5, respectively. Flexographic ink (varnish) was applied to cylinder 8. Polyester film PTM12 (manufactured by Unitika) was used as the transparent film substrate, and each ink shown in Table 5 was printed on this transparent film substrate using a wet trapping printing method with T414 (manufactured by Kinyosha) as the blanket. In this printing process, a design was printed that had a single solid color area and areas where all the color inks used were overcoated. The printing conditions are as follows: (Printing conditions) Ink feed rate: 50%, Oscillating roller and ink fountain chiller set temperature: 28℃ Pressure cylinder chiller temperature setting: 30℃ Printing speed: 100m / min Residual oxygen content: 200 ppm After printing all the inks, the inks were cured by irradiating them with electron beams using the electron beam irradiation device attached to the printing press. The electron beam irradiation conditions were an acceleration voltage of 110 kV and an exposure dose of 30 kGy.

[0083] (Examples 14 to 21) Printing was carried out in the same manner as in Example 13, except that the inks used during printing were changed to the ink combinations shown in Table 5. Furthermore, the inks were cured in the same manner as in Example 13 to obtain printed matter. The printing conditions and the electron beam irradiation conditions during curing were all the same as in Example 12.

[0084] (Comparative Examples 10 to 12) In the method for producing a printed matter of Example 13, instead of using a wet trapping printing method, an offset ink was printed and then irradiated with an electron beam to cure the ink (curing step 1), and then flexographic ink was printed. Printing was performed with each ink shown in Table 5 under the same printing conditions as in Example 13, yielding a printed matter. The electron beam irradiation conditions in curing step 1 were an acceleration voltage of 110 kV and an exposure dose of 30 kGy. The electron beam irradiation conditions after printing the flexographic ink (electron beam irradiation conditions in curing step 2) were the same as in Example 13, that is, an acceleration voltage of 110 kV and an exposure dose of 30 kGy.

[0085] (Comparative Examples 13 to 15) Printing was performed using each ink shown in Table 5 under the same printing conditions as in Example 13 to obtain a printed product. Specifically, a first ink coating was formed using an offset ink, and the first ink coating was irradiated with an electron beam without applying flexographic ink. The electron beam irradiation conditions were the same as in Example 13, with an acceleration voltage of 110 kV and an exposure dose of 30 kGy.

[0086] (Reference example 1) An adhesive was applied to the upper surface of the print layer of the print obtained in Comparative Example 13 (without varnish) by a bar coater method and dried at 80°C for 30 seconds, resulting in a coating amount of 2.0 g / m 2 As the adhesive, EA-N373A and EA-N373B (both manufactured by Toyo-Morton Co., Ltd.) were mixed at a mass ratio of 2 / 1 and used. Next, the printed matter coated with the adhesive as described above was laminated with a sealant using a hand roller. The sealant used was a non-stretched polypropylene film FHK-2 (manufactured by Futamura Chemical Co., Ltd., thickness 20 μm). The resulting mixture was then aged at 40°C for 24 hours to obtain a printed matter having a sealant / adhesive / printed layer (cured ink film) / film substrate structure.

[0087] <3> Evaluation of printed materials The printed materials obtained in the examples and comparative examples were evaluated for various properties according to the following methods. The results are shown in Tables 4 and 5.

[0088] <Hue> The prints obtained in the examples and comparative examples were measured for color in accordance with the method for measuring color - reflected and transmitted object color in JIS Z 8722:2009. X-Rite was used for color measurement, and the L*, a*, and b* values ​​of the single-color solid and multi-colored areas of the prints were measured. The color measurement values ​​of the printed matter were visually judged for the spread of the hue gamut, using the Japan Color hue as the standard. Specifically, a score of 5 was given for a hue that matched the Japan Color hue. A score of 6 to 10 was given for a gamut that expanded outward from the Japan Color hue. On the other hand, a score of 4 to 1 was given for a gamut that narrowed inward. As above, the evaluation was made on a 10-point scale, and the hue was evaluated according to the following criteria. (Evaluation criteria) 5:9~10 4:6~8 3:5 (practical level) 2:3~4 1:1~2

[0089] <Scratch resistance> The prints obtained in the examples and comparative examples were subjected to 500g x 100 strokes in a Gakushin-type abrasion resistance tester. The degree of abrasion on the surface of the prints was then visually observed and evaluated on a 5-point scale according to the following criteria. (Evaluation criteria) 5: No rubbing at all 4: Slight rubbing 3: Slight rubbing occurs 2: Some rubbing occurs 1: Obvious rubbing

[0090] <Crack resistance> The printed materials obtained in the examples and comparative examples were folded lengthwise and widthwise, and the degree of falling off of the printed layer was visually observed and evaluated on a 5-point scale according to the following criteria. (Evaluation criteria) 5: No dropouts 4: Slight dropout 3: A little bit of shedding occurs 2: Some shedding occurs 1: Obvious dropout

[0091] <Color change of the substrate> The color of the printed matter obtained in the examples and comparative examples in the areas where no ink was applied (non-printed areas such as the edges of the substrate) was visually confirmed. Using the non-printed areas before electron beam irradiation as a control, the change in color before and after electron beam irradiation was evaluated according to the following criteria. (Evaluation criteria) 3: No change at all 2: Slight discoloration 1: Clearly discolored

[0092] [Table 4]

[0093] [Table 5]

[0094] As can be seen from the results shown in Tables 4 and 5, the methods for producing printed matter according to the embodiments of the present invention (Examples 1 to 12 and 13 to 21) can provide printed matter with excellent coating properties, such as a wide range of hues, color change in the substrate, and scratch resistance and crack resistance, for both paper and transparent film substrates. The printed matter obtained in Reference Example 1 was evaluated for scratch resistance and crack resistance using the same method as described above, and was rated as "5" for scratch resistance and "5" for crack resistance. This demonstrates that the embodiments of the present invention can provide printed matter using varnish with scratch resistance and crack resistance equivalent to that of printed matter provided with a sealant. In contrast, the printed matter of Comparative Examples 1 to 9 and 10 to 15 showed a significant decrease in at least one of the above-mentioned coating film properties. In particular, the printed matter without a second printed layer (Comparative Examples 4 to 8 and 13 to 15) showed a significant decrease in coating film properties such as scratch resistance and crack resistance. Similarly, when the ink was cured using ultraviolet light instead of electron beams (Comparative Example 9), scratch resistance and crack resistance were significantly poor.

[0095] Examples 22 to 33 Using the method for producing printed matter in Example 1 as a reference, printed matter was obtained in the same manner as in Example 1, except that the conditions for the irradiation step were changed as shown in Table 6. The printed matter obtained in Examples 22 to 33 was evaluated for various properties according to the methods described above. The results are shown in Table 6.

[0096] [Table 6]

[0097] Examples 34 to 45 Using the method for producing printed matter in Example 13 as a reference, printed matter was obtained in the same manner as in Example 13, except that the conditions for the irradiation step were changed as shown in Table 7. The printed matter obtained in Examples 34 to 45 was evaluated for various properties according to the methods described above. The results are shown in Table 7.

[0098] [Table 7]

Claims

1. A method for manufacturing a printed matter having a substrate, a first printed layer formed on the substrate, and a second printed layer formed on the first printed layer, comprising: Step 1: applying one or more active energy ray-curable offset printing inks to a surface of a substrate to form a first ink coating film; a step 2 of applying one or more active energy ray-curable flexographic printing inks, including an active energy ray-curable white flexographic printing ink, to the surface of the substrate on which the first ink coating film obtained in the step 1 has been formed, to form a second ink coating film; A method for producing a printed matter, comprising step 3, after step 2, of irradiating with electron beams to simultaneously harden the first ink coating film and the second ink coating film, thereby forming a first printed layer consisting of the hardened product of the first ink coating film and a second printed layer consisting of the hardened product of the second ink coating film.

2. The method for producing a printed matter according to claim 1, wherein in step 3, the accelerating voltage of the electron beam is 50 to 250 kV.

3. The method for producing a printed matter according to claim 1, wherein in step 3, the electron beam is irradiated with a dose of 10 to 60 kGy.

4. The method for producing a printed matter according to claim 1, wherein the printing speed is 50 to 300 m / min.

5. The method for producing a printed matter according to claim 1 , wherein the method does not include a step of irradiating the active energy ray-curable offset printing ink with active energy rays between the steps 1 and 2.

6. The method for producing a printed matter according to claim 1 , wherein the actinic ray-curable offset printing ink contains a resin, a polyfunctional (meth)acrylate, and a colorant.

7. The method for producing a printed matter according to claim 1 , wherein the substrate is a transparent film substrate.

8. The method for producing a printed matter according to claim 7, wherein the transparent film substrate has a thickness of 1 μm to 35 μm.

9. The method for producing a printed matter according to claim 1 , wherein the printed matter is used as a packaging material.

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