Manufacturing methods for printed materials

Abstract

The present invention provides a method for manufacturing printed materials having two or more printing layers that suppresses the deterioration and discoloration of the substrate due to electron beam irradiation, enables a wide range of colors, and offers excellent productivity. [Solution] A method for manufacturing a printed material 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 the substrate to form a first ink coating; step 2 applying one or more active energy ray curable flexographic printing inks to the surface of the substrate on which the first ink coating obtained in step 1 is formed to form a second ink coating; and step 3, after step 2, irradiating with an electron beam to simultaneously cure the first ink coating and the second ink coating to form a first printed layer made of a cured product of the first ink coating and a second printed layer made of a cured product of the second ink coating.

Description

Technical Field

[0001] Embodiments of the present invention relate to a method for manufacturing printed matter.

Background Art

[0002] Packaging materials mainly used in the fields of food and daily necessities are expected to have an expanding demand in the future with the global population increase. Currently, in the printing of flexible packaging materials, gravure printing is the mainstream. In gravure printing, printed matter with vivid appearance can be obtained. However, since gravure printing uses ink containing a large amount of solvent, a large amount of energy is required for drying and exhaust treatment of the ink solvent, resulting in a large environmental load. Furthermore, in recent years, market needs have changed from conventional mass production and mass consumption to small lots, many varieties, and short delivery times. In contrast, gravure printing is a printing method suitable for large-lot printing, and since the plate cost and plate-making cost are high, the production cost of printed matter tends to be high. Therefore, in recent years, offset printing, which has a low plate cost and plate-making cost, is easy to handle small lots and short delivery times, and is advantageous in terms of the cost of printed matter, has attracted attention.

[0003] Offset printing is a printing method widely popular as a system for supplying printed matter at high speed, in large quantities, and at low cost. The ink used during printing may be either solvent-based or non-solvent-based. In recent years, from the viewpoints of environmental issues and response to carbon neutrality, active energy ray-curable inks that instantaneously cure by irradiation with active energy rays have attracted attention, and studies on offset printing using such inks have also been advanced.

[0004] In the manufacture of packaging materials used in fields such as food and household goods, the printing process is generally carried out by high-speed printing in a roll-to-roll format. From the viewpoint of increasing productivity in the above printing process, the quick-drying properties of the ink are important. For this reason, offset printing using active energy ray-curable inks is expected to be used in the manufacture of printed materials used for packaging. For example, Patent Document 1 discloses a method for manufacturing packaging materials that includes a step of printing ultraviolet-curable or electron beam-curable ink onto paper or plastic film by offset printing.

[0005] In recent years, among active energy ray curing inks, UV-curing inks containing photopolymerization initiators and curing systems for UV-curing inks have become the mainstream in the market. UV-curing inks do not contain volatile components and cure instantly when exposed to ultraviolet energy rays. Therefore, it is possible to shorten the drying process without using thermal energy, and in addition to environmental advantages, it has the advantages of energy saving and high productivity.

[0006] However, for packaging materials used in fields such as food and daily necessities, the addition of photopolymerization initiators to inks is undesirable from the standpoint of preventing contamination of contents due to migration, etc. Therefore, as a curing method using active energy rays that does not contain photopolymerization initiators, the expansion of electron beam curing methods that do not require photopolymerization initiators is expected.

[0007] Furthermore, when forming a multilayer printed material having two or more printing layers on a substrate using an active energy ray curing ink, a method is generally used in which the ink is applied to the substrate and cured to form a first printing layer, and then the ink is applied to the first printing layer, which is made of cured ink, and cured to form a second printing layer. For example, Patent Document 2 discloses a printing method using an offset printing press in which UV (ultraviolet) curing ink is applied to the substrate, the ink is cured by UV irradiation, and then printing such as screen printing or flexographic printing is performed as a post-processing step. However, the method of curing the ink each time it is applied is desirable to improve from the viewpoint of production efficiency. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2004-358788 [Patent Document 2] International Public Gazette 2014 / 083722 [Overview of the project] [Problems that the invention aims to solve]

[0009] As mentioned above, electron beam curing in the manufacturing of printed materials has the advantage of not requiring the addition of a photopolymerization initiator to active energy ray curable inks. However, because electron beam curing uses higher irradiation energy than ultraviolet light, it is prone to problems such as damage to the substrate and discoloration of the substrate. When printing on a substrate, there are always unprinted areas at the edges of the substrate. These unprinted areas are particularly susceptible to damage from electron beams, making substrate discoloration and deterioration unavoidable. Substrate discoloration and deterioration reduce productivity from the perspective of industrializing the manufacturing of printed materials, and therefore improvement is desired.

[0010] Furthermore, for example, when using electron beams as a curing method in the manufacture of printed materials having a first printed layer and a second printed layer sequentially on a substrate, there are limitations to the range of colors in the printed material. One reason for the narrowing of the color range is that the first printed layer, formed by curing the ink with electron beams, is affected by the electron beams irradiated during the formation of the second printed layer. In the first place, the method of curing the ink each time it is applied needs improvement from the standpoint of production efficiency.

[0011] Furthermore, in the production of printed materials with a surface-printed structure, a second printed layer is sometimes formed using varnish after the first printed layer is formed, for the purpose of surface protection. In contrast, a method to improve the hue can be considered by providing a plastic film (sealant) instead of the second printed layer (a surface protection layer formed using varnish). However, printed materials with a plastic film as a surface protection layer are undesirable from the standpoint of recycling and CO2 reduction.

[0012] In view of these circumstances, the present invention provides a method for manufacturing printed materials having two or more printing layers that suppresses deterioration and discoloration of the substrate due to electron beam irradiation, enables a wide range of colors, and offers excellent productivity. [Means for solving the problem]

[0013] The inventors of the present invention conducted various studies on methods for manufacturing printed materials using active energy ray-curable inks. As a result, they found that by forming two or more ink coatings on a substrate using wet trapping and simultaneously curing these ink coatings with an electron beam, the above problems can be solved without substrate discoloration and with a wide color gamut. Here, "wet trapping (also called wet-on-wet)" refers to a printing method in which one color of ink is applied immediately after the application of one color of ink. In wet trapping printing, the combination of inks is important to prevent trapping defects because the upper layer of ink is applied while the lower layer of ink is still wet or uncured. The inventors of the present invention found that by using offset printing ink for the lower layer and flexographic printing ink for the upper layer, it is possible to perform wet trapping printing successfully without trapping defects. Furthermore, we discovered that when offset ink is printed using wet trapping, and then flexonis is printed and cured using an electron beam to produce a printed material, there is no discoloration of the substrate, and the printed material has coating properties equivalent to those of a printed material with a sealant, even with only varnish. This led to the completion of the present invention.

[0014] In other words, 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 manufacturing a printed material having a first printed layer and a second printed layer sequentially on a substrate, Step 1 involves applying one or more active energy ray-curable offset printing inks to the surface of a substrate to form a first ink coating, Step 2 involves applying one or more active energy ray curable flexographic printing inks to the surface of the substrate on which the first ink coating obtained in step 1 is formed, thereby forming a second ink coating. A method for manufacturing a printed material, comprising: step 2 above, step 3, in which an electron beam is irradiated to simultaneously cure the first ink coating and the second ink coating, thereby forming a first printed layer consisting of the cured first ink coating and a second printed layer consisting of the cured second ink coating.

[0015] <2> In step 3, the acceleration voltage of the electron beam is 50 to 250 kV, <1> A method for manufacturing printed materials as described above.

[0016] <3> In step 3, the irradiation dose of the electron beam is 10 to 60 kGy, <1> or <2> A method for manufacturing printed materials as described above.

[0017] <4> The printing speed is 50-300 m / min, as described above. <1> ~ <3> A method for manufacturing printed materials as described in any one of the following.

[0018] <5> The above-mentioned process does not include a step between step 1 and step 2 in which an active energy ray is irradiated to cure the active energy ray-curable offset printing ink. <1> ~ <4> A method for manufacturing printed materials as described in any one of the following.

[0019] <6> The active energy ray curable offset printing ink comprises a resin, a polyfunctional (meth)acrylate, and a colorant. <1> ~ <5> A method for manufacturing printed materials as described in any one of the following.

[0020] <7>The method for manufacturing a printed matter according to any one of <1> to <6> above, wherein the active energy ray-curable flexographic ink contains an active energy ray-curable white flexographic ink.

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

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

[0023] <10>The method for manufacturing a printed matter according to <9> above, wherein the thickness of the paper substrate is 50 μm to 150 μm.

[0024] <11>The method for manufacturing a printed matter according to <9> above, wherein the thickness of the transparent film substrate is 1 μm to 35 μm.

[0025] <12>The method for manufacturing a printed matter according to any one of <1> to <11> above, wherein the printed matter is used as a packaging material.

Advantages of the Invention

[0026] According to an embodiment of the present invention, there is provided a method for manufacturing a printed matter having two or more printing layers, which can suppress deterioration and discoloration of a substrate due to irradiation with an electron beam, can achieve a wide range of hues, and is excellent in productivity.

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and embodiments implemented within a range not changing the gist of the present invention are also included.

[0028] One embodiment of the present invention relates to a method for manufacturing a printed material having a first printed layer and a second printed layer sequentially on a substrate. The method for manufacturing a printed material according to this embodiment comprises 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 a substrate, and a curing step of irradiating the ink coating film obtained in the printing step, which has the configuration of substrate / active energy ray curable offset printing ink / active energy ray curable flexographic printing ink, with an electron beam.

[0029] The method for manufacturing a printed material according to this embodiment is, more specifically, a method for manufacturing a printed material having a first printed layer and a second printed layer sequentially on a substrate, Step 1 involves applying one or more active energy ray-curable offset printing inks to the surface of a substrate to form a first ink coating, Step 2 involves applying one or more active energy ray curable flexographic printing inks to the surface of the substrate on which the first ink coating obtained in step 1 is formed, thereby forming a second ink coating. The present invention relates to a method for manufacturing a printed material, comprising step 3, after step 2, irradiating with an electron beam to simultaneously cure the first ink coating and the second ink coating, thereby forming a first printed layer consisting of the cured first ink coating and a second printed layer consisting of the cured second ink coating.

[0030] According to the printing method of this embodiment, productivity can be easily improved and damage to the substrate can be easily suppressed by simultaneously curing the active energy ray-curable offset printing ink and the active energy ray-curable flexographic printing ink. As a result, defects such as color changes and deterioration of the substrate caused by electron beam irradiation can be suppressed.

[0031] The method for manufacturing printed materials according to this embodiment may include other steps in addition to the printing and curing steps described above, as necessary. For example, it may further include a step of performing a surface treatment on the substrate, 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 that is carried out independently of other steps, and may include other steps if the intended purpose of that step is achieved. However, the method for manufacturing printed materials according to this embodiment is characterized in that, in the printing step, there is no step between step 1 and step 2 in which an active energy ray is irradiated to cure the active energy ray-curable offset printing ink.

[0032] In the method for manufacturing printed materials 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 mentioned above may be, for example, art paper, coated paper, cast paper, synthetic paper, and newspaper. The plastic film may be, for example, polyethylene terephthalate, polyethylene, polyolefins such as polypropylene, and polyamides. Furthermore, the metal may be aluminum, zinc, or copper, and may be in the form of a metal film or a metal vapor-deposited film. In some embodiments, the substrate may be paper, paper laminated with a plastic film, or paper having a metal vapor-deposited film. In other embodiments, the substrate may be a plastic film or a plastic film having a metal vapor-deposited film. Among these, paper or a transparent plastic film (also called a transparent film) can be preferably used as the substrate.

[0033] The printed material may be either front-printed or back-printed. The substrate can be selected according to the desired structure of the printed material. When the printed material is printed on the front surface, the substrate may be paper, a plastic film, or a metal-deposited film. When the substrate is paper, the first printed layer preferably includes a pattern such as a picture or characters formed using colored ink, and the second printed layer may be a transparent layer formed using varnish 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] Furthermore, if the printed material is reverse-printed, the substrate may be a plastic film, and a transparent film is preferred. When the substrate is a plastic film, the first printing layer preferably includes a pattern such as a picture or characters formed using colored ink, and the second printing layer may be a base layer formed using 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. Also, 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. In addition, a decrease in the curing speed of the ink film can be easily suppressed.

[0036] In the method for manufacturing printed materials of this embodiment, one or more active energy ray-curable flexographic printing inks are printed on the uncured ink film of the active energy ray-curable offset printing ink printed on the substrate in step 1 without curing the ink film. Therefore, in step 2, it is necessary to suppress the migration of active energy ray-curable flexographic printing ink (hereinafter referred to as flexographic ink) onto the coating of the active energy ray-curable offset printing ink (hereinafter referred to as offset ink). Accordingly, it is preferable to appropriately adjust the relationships between the various physical properties of the offset ink and the flexographic ink.

[0037] Generally, when forming an upper ink film on top of an uncured lower ink film, the viscosity of the ink forming the upper film is made lower than the viscosity of the ink forming the lower film. By adjusting the viscosity of each ink in this way, problems such as ink migration and color mixing can be suppressed. In contrast, the offset ink and flexographic ink used in this embodiment have significantly different viscosities, with the viscosity of the offset ink being clearly 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 of the offset ink used in step 1 at 25°C may preferably be 30 to 50 mN / m, more preferably 35 to 45 mN / m. On the other hand, the surface tension X2 of the flexographic ink used in step 2 at 25°C may preferably be 30 to 50 mN / m, more preferably 35 to 45 mN / m. The above surface tensions X1 and X2 are values ​​obtained by measuring the cured film of each ink at 25°C, and it is preferable that X2 is smaller than X1.

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

[0040] From the viewpoint of ensuring good curing of the offset ink coating and the flexographic ink coating, it is preferable to appropriately adjust the thickness of the respective coating, the composition of the ink, etc. In some embodiments, 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. On the other hand, 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 manufacturing printed materials of this embodiment, the active energy ray-curable offset printing ink used in step 1 and the active energy ray-curable offset printing flexographic ink used in step 2 are not particularly limited. Various offset inks and flexographic inks well 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 active energy ray-curable offset printing ink (offset ink) used in step 1 comprises a resin, a polymerizable compound, and a colorant. The above resin preferably includes one or more selected from the group consisting of allyl resin, diallyl phthalate resin, rosin, maleated rosin, acrylic rosin, rosin-modified resin, epoxy resin, polyester resin, polyurethane resin, alkyd resin, and petroleum resin.

[0043] Polyfunctional (meth)acrylate compounds can be suitably used as the polymerizable compounds mentioned above. Specific examples of polyfunctional (meth)acrylate compounds include dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, and trimethylolpropane ethoxytriacrylate.

[0044] The above-mentioned coloring agent may be either a pigment or a dye, but a pigment is preferably used. Examples of pigments may be yellow pigment, red pigment, blue pigment, black pigment, and white pigment. One of these pigments may be used alone, or two or more may be used in combination. Offset ink may further contain various additives as needed, such as wear-resistant agents, lubricants, pigment dispersants, and polymerization inhibitors.

[0045] In some embodiments, when an offset ink composed of a combination of the previously exemplified resin and a polyfunctional (meth)acrylate compound is used, the ink tends to cure well even when the electron beam irradiation energy is low. In some embodiments, it is preferable that the offset ink used in step 1 is substantially free of solvents such as water and organic solvents. In this specification, "substantially solvent-free" means that no intentionally added solvents are present, and does not mean that solvents introduced during the ink manufacturing process are completely excluded. Based on the total mass of the offset ink, the solvent content may preferably be 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. By making the offset ink substantially solvent-free, changes in ink viscosity can be easily suppressed, and good coating film formation can be achieved.

[0046] The offset ink used in step 1 can be manufactured according to methods well known in the art. For example, offset ink can be manufactured by mixing a pigment, a (meth)acrylate compound, and a diallyl phthalate resin together in a kneader, and then dispersing the resulting mixture in a disperser. Various additives such as wear-resistant additives, lubricants, pigment dispersants, and polymerization inhibitors may be added as needed. When using additives, they should be added to the kneader along with the pigment, etc., in the manufacturing method described above. Alternatively, it is also possible to manufacture offset ink by pre-mixing each material such as the pigment, performing preliminary stirring, and then adding them to the kneader. Furthermore, as with the resin varnish described in the examples below, it is also possible to add components other than the pigment in the form of a varnish obtained by pre-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 a colored ink such as yellow, red, cyan, or black. In yet another embodiment, the offset ink may be a transparent ink (varnish). In step 1, one or more of these offset inks can be used in combination.

[0048] (Flexographic ink) In some embodiments, the active energy ray-curable flexographic printing ink (flexographic ink) used in step 2 preferably contains at least a polymerizable compound, and further contains a resin and various additives. Examples of various additives include wear-resistant agents, lubricants, pigment dispersants, polymerization inhibitors, etc. The flexographic ink may further contain a coloring agent such as a white pigment, if necessary. In some embodiments, the flexographic ink may be a white ink. In other embodiments, the flexographic ink may be a transparent ink (flexonis).

[0049] The polymerizable compounds that constitute the flexographic ink are not particularly limited. In one embodiment, polymerizable compounds with a molecular weight of 100 to 6,000 can be suitably used. Specific examples of polymerizable compounds include polyfunctional (meth)acrylate compounds such as trimethylolpropane ethoxytriacrylate, tripropylene glycol diacrylate, and glycerin propoxytriacrylate. One of these can be suitably used alone, or two or more can be suitably used in combination.

[0050] The resins that can be used in flexographic inks may be either thermosetting resins or thermoplastic resins. 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., ethylcellulose, 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. One of these resins may be used alone, or two or more may be used in combination.

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

[0052] In the printing process, 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 refers to the moving speed of the substrate and can be adjusted as appropriate.

[0053] In the method for manufacturing printed materials of this embodiment, there is no step between step 1, which is the printing step, and step 2, in which an active energy ray is irradiated to cure the offset ink coating. Instead, in step 3 (curing step), the offset ink coating and the flexographic ink coating are cured simultaneously by irradiating them with an electron beam. Therefore, productivity can be easily improved. Electron beam irradiation can be performed using methods well known in the art. For example, electron beam irradiation can be performed using an electron beam irradiation device that is common in the art.

[0054] The offset inks and flexographic inks used in this embodiment are active energy ray curing type, and therefore can be cured not only by electron beams but also by irradiation with other active energy rays such as ultraviolet light. However, when using ultraviolet light, it is necessary to add a photopolymerization initiator to the ink. Photopolymerization initiators tend to be a cause of migration, which is a problem that needs to be addressed in fields such as food packaging materials. On the other hand, the printing method of this embodiment uses electron beams, which do not require a photopolymerization initiator, and therefore has the advantage of being highly productive, as well as easily providing printed materials that can be suitably used in fields where the 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 deep into the ink coating, making it easy for uneven curing to occur between the surface and the deeper parts of the ink coating. Also, if the irradiation dose is too low, the amount of radicals generated will be insufficient, and the curing performance tends to be poor. On the other hand, if the acceleration voltage and irradiation dose are too high, the impact on the substrate will be greater, and the substrate will be more susceptible to damage. Therefore, it is preferable to adjust the electron beam irradiation considering the curing performance of the ink and the damage to the substrate.

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

[0057] In the electron beam irradiation step (ink coating film curing step), the moving speed of the substrate having the ink coating film (also referred to as the printing speed) is 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 under a nitrogen atmosphere in order to suppress the inhibition of ink curing by oxygen. Since the electron beam irradiation step (curing step) is carried out in a printing machine equipped with an electron beam generator, the inside of the printing machine system is maintained in a nitrogen atmosphere. In the manufacturing method of the present embodiment, in addition to irradiating the electron beam under a nitrogen atmosphere, by adjusting the printing speed within the above range, the influence of oxygen can be suppressed, and the curing of the ink coating film on the substrate can proceed favorably.

[0058] In some embodiments, it is preferable to adjust the residual oxygen amount in the system to 300 ppm or less. A residual oxygen amount of 300 ppm or less is a general condition required even in conventional printing methods. In the manufacturing method of the present embodiment, when the residual oxygen amount in the system exceeds 300 ppm, for example, even if it is about 800 ppm, the curing of the ink can proceed favorably by adjusting the irradiation conditions and the composition of the ink.

[0059] The printed matter obtained by the manufacturing method of the present embodiment may have, for example, a structure of paper / offset colored ink printing layer / flexographic printing layer. As another example, the printed matter may have a structure of transparent film / offset colored ink printing layer and offset white ink printing layer / flexographic. The printed matter can be used for various applications. For example, the printed matter can be suitably used as a packaging material.

Examples

[0060] The present invention will be described more specifically with reference to the following examples. The present invention is not limited to the following examples as long as it does not exceed the gist thereof. Unless otherwise specified, "parts" represents "parts by mass" and "%" represents "% by mass".

[0061] <1> Preparation of each ink Offset ink preparation example (Preparation of resin varnish) The resin, polymerization inhibitor, and polymerizable compound were mixed in the following proportions while the temperature was raised to 95°C, dissolving the resin and polymerization inhibitor 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 (manufactured by Osaka Soda Co., Ltd.) 30 parts by mass Polymerization inhibitor: TBHQ FINE (t-butylhydroquinone, manufactured by Kusumoto Chemical Co., Ltd.) 1 part by mass Polymerizable compound: Dipentaerythritol hexaacrylate (MIRAMER M600, manufactured by MIWON) 69 parts by mass

[0062] (Various offset inks) Various offset inks were obtained by mixing the previously prepared resin varnish 1 with monomers 1, 2, and 3 (meth)acrylate compounds, pigments, additives (lubricant and pigment dispersant), and polymerization inhibitors in the proportions shown in Table 1. The amount of polymerization inhibitor added during the preparation of the offset inks was adjusted so that the total amount of polymerization inhibitors in the resin varnish and the polymer varnish combined was 1 part by mass. Specifically, the amounts of polymerization inhibitors listed in Table 1 were added.

[0063] [Table 1]

[0064] The details of each component listed in Table 1 are as follows: • Varnish: Varnish 1 prepared earlier • Monomer 1: Dipentaerythritol hexaacrylate (MIWON MIRAMER M600) • Monomer 2: Ditrimethylolpropanetetraacrylate (EBECRYL 1142, manufactured by Daicel Ornex) • Monomer 3: Trimethylolpropane triacrylate ethylene oxide adduct (MIRAMER M3160, manufactured by MIWON) • Pigments: As described below • Wear-resistant additive: KTL-4N (PTFE wax, manufactured by Kitamura Co., Ltd.) • Pigment dispersant: Solsperse 24000 GR (manufactured by Lubrizol Co., Ltd.) • Polymerization inhibitor: TBHQ FINE (t-butylhydroquinone, manufactured by Kusumoto Chemical Co., Ltd.)

[0065] The offset inks for each color are as follows: (Yellow ink) Using Lionol Yellow 1314 (manufactured by Toyo Color Co., Ltd.) as the pigment, each component was mixed according to the mixing ratio shown in Table 1, and the mixture was kneaded using a three-roll press until the particle size was 7.5 microns or less, as measured by a dispersion particle measuring instrument (grindometer), to obtain yellow ink.

[0066] (Red ink) Using Lionol Red 5620 (manufactured by Toyo Color Co., Ltd.) as the pigment, each component was mixed according to the mixing ratio shown in Table 1, and the mixture was kneaded using a three-roll press until the particle size was 7.5 microns or less, as measured by a dispersion particle measuring instrument (grindometer), to obtain red ink.

[0067] (Blue ink) Using Lionol Blue-FG7330 (manufactured by Toyo Color Co., Ltd.) as the pigment, each component was blended according to the mixing ratio shown in Table 1, and the mixture was kneaded using a three-roll press until the particle size was 7.5 microns or less, as measured by a dispersion particle measuring instrument (grindometer), to obtain blue ink.

[0068] (Black ink) MA-11 (manufactured by Mitsubishi Chemical Corporation) was used as the pigment, and each component was mixed according to the mixing ratio shown in Table 1. The mixture was kneaded using a three-roll press with a dispersion particle measuring instrument (grindometer) until the particle size was 7.5 microns or less, and black ink was obtained.

[0069] (White ink) Typake CR50-2 (manufactured by Ishihara Sangyo Co., Ltd.) was used as the pigment, and each component was mixed according to the mixing ratio shown in Table 1. The mixture was kneaded using a three-roll press with a dispersion particle system measuring instrument (grindometer) until the particle size was 7.5 microns or less, and white ink was obtained.

[0070] (2) Example of flexographic ink (varnish) preparation Polymerizable compounds, monomers 3, 4, and 5, along with an anti-wear additive and a polymerization inhibitor, were mixed in the proportions shown in Table 2. This mixture was stirred at 50°C for 1 hour using a disperser blade at a rotation speed of 1000 rpm to obtain flexonis.

[0071] [Table 2]

[0072] The details of each component listed in Table 2 are as follows: • Monomer 3: Trimethylolpropaneethoxytriacrylate (MIWON, MIRAMER M3160) • Monomer 4: Tripropylene glycol diacrylate (manufactured by Daicel Ornex, TPGDA) • Monomer 5: Glycerin propoxytriacrylate (manufactured by Daicel Ornex, OTA480) • Wear-resistant additive: KTL-4N (PTFE wax, manufactured by Kitamura Co., Ltd.) • Polymerization inhibitor: TBHQ FINE (t-butylhydroquinone, manufactured by Kusumoto Chemical Co., Ltd.)

[0073] For each electron beam curable (EB) type offset ink and flexographic ink prepared as described above, viscosity, surface tension, and surface free energy were measured according to the method described below. The results are shown in Table 3. <Viscosity> The measurements were taken using an E-type viscometer at 25°C, 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 the surface tension was measured at an ambient temperature of 25°C using a surface tension meter (KRUSS double titration handheld contact angle / 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 the surface free energy was measured at an ambient temperature of 25°C using a surface free energy analyzer (KRUSS MSA double titration handheld contact angle / surface free energy analyzer).

[0076] [Table 3]

[0077] <2> Manufacturing of printed materials (Example 1) Using a lithographic and flexographic hybrid printing press (CI-8, manufactured by COMEXI), offset inks of black, cyan, magenta, and yellow were set in the 1st to 4th cylinders in that order, and flexographic ink (varnish) was set in the 8th cylinder. Kintou Kata Art Paper (manufactured by Oji Paper Co., Ltd.) was used as the paper substrate, and T414 (manufactured by Kinyosha) was used as the blanket. Printing was performed on this paper substrate using a wet trapping method with each of the inks shown in Table 4. In this printing process, a design was printed that consisted of solid color areas and areas with overlapping inks of all the colors used. The printing conditions are as follows: (Printing conditions) Ink feed rate: 50% Chiller temperature setting for oscillating roller and ink fountain: 28℃ Chiller temperature setting for pressure cylinder: 30℃ Printing speed: 100m / min Residual oxygen level: 200 ppm After printing all the inks, the inks were cured by irradiating them with an electron beam using an electron beam irradiation device attached to the printing press to obtain the printed material. The electron beam irradiation conditions were an acceleration voltage of 110kV and an irradiation dose of 30kGy.

[0078] (Examples 2-12) Except for changing the ink combination used during printing to the one shown in Table 4, printing was performed according to the same method as in Example 1. Furthermore, the ink was cured in the same manner as in Example 1 to obtain the printed material. The printing conditions and the electron beam irradiation conditions during curing were all the same as in Example 1.

[0079] (Comparative Examples 1-3) In the method for manufacturing printed materials of Example 1, instead of the wet trapping printing method, the offset ink was printed, then irradiated with an electron beam to cure the ink (performing curing step 1), and then printed with flexographic ink. Otherwise, the printing conditions were the same as in Example 1, and printed materials were obtained using each ink shown in Table 4. The electron beam irradiation conditions in curing step 1 were an acceleration voltage of 110kV and an irradiation dose of 30kGy. The electron beam irradiation conditions after printing with flexographic ink (electron beam irradiation conditions in curing step 2) were the same as in Example 1, with an acceleration voltage of 110kV and an irradiation dose of 30kGy.

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

[0081] (Comparative Example 9) Offset inks of black, cyan, magenta, and yellow were prepared in the same manner as in Example 1. To 100 parts of each offset ink, 10 parts of Omnirad379EG (manufactured by IGM) were added as a photopolymerization initiator to prepare UV-curable offset inks of each color. Furthermore, a flexonis similar to that in Example 1 was prepared, and 10 parts of Omnirad379EG (manufactured by IGM) were added to 100 parts of the flexonis as a photopolymerization initiator to prepare an ultraviolet-curable flexonis. 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 sequentially applied to Kintou Kata Art Paper (manufactured by Oji Paper Co., Ltd.). Next, as a curing step, the ink coating was cured by irradiating it with ultraviolet light, and a printed material having the same configuration as Example 1 was obtained as shown in Table 4. The above-mentioned curing process using ultraviolet irradiation was carried out using a metal halide lamp under irradiation conditions of 128W.

[0082] (Example 13) A lithographic and flexographic hybrid printing press (CI-8, manufactured by COMEXI) was used, with white, black, cyan, magenta, and yellow offset inks set up in order on cylinders 1 through 5. Flexographic ink (varnish) was set up on cylinder 8. Polyester film PTM12 (manufactured by Unitika) was used as the transparent film substrate, and T414 (manufactured by Kinyosha) was used as the blanket. Printing was performed on this transparent film substrate using a wet trapping method with each of the inks shown in Table 5. In this printing process, a design was printed that consisted of solid color areas and areas with overlapping colors of all the inks used. The printing conditions are as follows: (Printing conditions) Ink feed rate: 50% Chiller temperature setting for oscillating roller and ink fountain: 28℃ Chiller temperature setting for pressure cylinder: 30℃ Printing speed: 100m / min Residual oxygen level: 200 ppm After printing all the inks, the inks were cured by irradiating them with an electron beam using an electron beam irradiation device attached to the printing press to obtain the printed material. The electron beam irradiation conditions were an acceleration voltage of 110kV and an irradiation dose of 30kGy.

[0083] (Examples 14-21) Except for changing the ink combination used during printing to the one shown in Table 5, printing was performed in the same manner as in Example 13. Furthermore, the ink was cured in the same manner as in Example 13 to obtain the printed material. The printing conditions and the electron beam irradiation conditions during curing were all the same as in Example 12.

[0084] (Comparative Examples 10-12) In the printing method of Example 13, instead of the wet trapping printing method, the offset ink was printed, then irradiated with an electron beam to cure the ink (curing step 1 was performed), and then the flexographic ink was printed. Except for this, the printing conditions were the same as in Example 13, and the printed materials were obtained by printing each ink shown in Table 5. The electron beam irradiation conditions in curing step 1 were an acceleration voltage of 110kV and an irradiation dose of 30kGy. The electron beam irradiation conditions after printing with flexographic ink (electron beam irradiation conditions in curing step 2) were the same as in Example 13, with an acceleration voltage of 110kV and an irradiation dose of 30kGy.

[0085] (Comparative Examples 13-15) Prints were obtained by printing each of the inks shown in Table 5 under the same printing conditions as in Example 13. Specifically, a first ink coating was formed using 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 110kV and an irradiation dose of 30kGy.

[0086] (Reference example 1) In Comparative Example 13 (without varnish), the adhesive was applied to the upper surface of the printed layer of the printed material using a bar coater method, and dried at 80°C for 30 seconds, with an application amount of 2.0 g / m². 2 A coating film was formed. As the adhesive, EA-N373A / EA-N373B (both manufactured by Toyo Morton Co., Ltd.) were mixed in a mass ratio of 1 / 2 and used. Next, the printed material to which the adhesive had been applied as described above was bonded to the sealant using a hand roller. For the sealant, an unoriented polypropylene film FHK-2 (manufactured by Futamura Chemical Co., Ltd., 20 μm thick) was used. Subsequently, by aging at 40°C for 24 hours, a printed material having the following structure was obtained: sealant / adhesive / printed layer (ink-cured film) / film substrate.

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

[0088] <Hue> The printed materials obtained in the examples and comparative examples were colorimetrically measured according to the method for measuring color of reflective and transmitted objects, as specified in JIS Z 8722:2009. X-Rite was used for colorimetric measurement, and the L*, a*, and b* values ​​were measured for both solid color areas and layered color areas of the printed materials. Regarding the colorimetric values ​​of printed materials, the extent of the hue gamut was visually judged based on the hue of Japan Color. Specifically, a value of 5 was assigned to a hue that matched the hue of Japan Color. A value of 6-10 was assigned to a hue that extended outward from the hue of Japan Color. Conversely, a value of 4-1 was assigned to a hue that narrowed inward. The hue was evaluated using the above 10-point scale and 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 printed materials obtained in the examples and comparative examples were subjected to 500g x 100 reciprocations in a Japan Society for the Promotion of Science (JSPS) type abrasion resistance tester. The degree of surface abrasion of the printed materials was visually observed and evaluated on a 5-point scale according to the following criteria. (Evaluation Criteria) 5: No scratches whatsoever 4: Slight friction occurs 3: Slight friction occurred 2: Slight abrasion occurs 1: Obvious abrasion occurred

[0090] <Crack resistance> The printed materials obtained in the examples and comparative examples were folded in both the vertical and horizontal directions, and the amount of print layer removed was visually observed and evaluated on a 5-point scale according to the following criteria. (Evaluation Criteria) 5: No dropouts at all 4: Slight shedding occurred 3: Some dropouts occurred. 2: Some shedding occurs 1: Clear dropouts occurred

[0091] <Color change of the substrate> The color of the unprinted areas (non-printed areas such as the edges of the substrate) of the printed materials obtained in the examples and comparative examples was visually inspected. Using the non-printed areas before electron beam irradiation as a comparison, the color change before and after electron beam irradiation was evaluated according to the following criteria. (Evaluation Criteria) 3: No change at all 2: Slightly discolored 1: Clearly discolored

[0092] [Table 4]

[0093] [Table 5]

[0094] As can be seen from the results shown in Tables 4 and 5, the method for manufacturing printed materials according to the embodiments of the present invention (Examples 1-12 and 13-21) provides printed materials with excellent color spread, substrate color change, and various coating properties such as scratch resistance and crack resistance, regardless of whether the substrate is paper or transparent film. When the printed material obtained in Reference Example 1 was evaluated for scratch resistance and crack resistance in the same manner as described above, it received a rating of "5" for both scratch resistance and crack resistance. From this, it can be seen that, according to the embodiments of the present invention, even printed materials with a varnish-based composition can obtain scratch resistance and crack resistance equivalent to those of printed materials with a sealant. In contrast, the printed materials of Comparative Examples 1-9 and 10-15 showed a significant decrease in at least one of the above-mentioned coating properties. In particular, the printed materials without a second printing layer (Comparative Examples 4-8 and 13-15) showed a significant decrease in coating properties such as scratch resistance and crack resistance. Similarly, when the ink was cured using ultraviolet light instead of an electron beam (Comparative Example 9), the scratch resistance and crack resistance were significantly inferior.

[0095] (Examples 22-33) Based on the manufacturing method of the printed material in Example 1, printed materials were obtained in the same manner as in Example 1, except that the irradiation process conditions were changed as shown in Table 6. The printed materials obtained in Examples 22 to 33 were evaluated for various properties according to the method described above. The results are shown in Table 6.

[0096] [Table 6]

[0097] (Examples 34-45) Based on the manufacturing method of the printed material in Example 13, printed materials were obtained in the same manner as in Example 13, except that the irradiation process conditions were changed as shown in Table 7. The printed materials obtained in Examples 34 to 45 were evaluated for various properties according to the method described above. The results are shown in Table 7.

[0098] [Table 7]

Claims

1. A method for manufacturing a printed material having a first printed layer and a second printed layer sequentially on a substrate, Step 1 involves applying one or more active energy ray-curable offset printing inks to the surface of a substrate to form a first ink coating, Step 2 involves applying one or more active energy ray curable flexographic printing inks to the surface of the substrate on which the first ink coating obtained in step 1 is formed, thereby forming a second ink coating. A method for manufacturing a printed material, comprising: step 2 above, step 3, in which an electron beam is irradiated to simultaneously cure the first ink coating and the second ink coating, thereby forming a first printed layer consisting of the cured first ink coating and a second printed layer consisting of the cured second ink coating.

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

3. The method for manufacturing a printed article according to claim 1, wherein in step 3, the irradiation dose of the electron beam is 10 to 60 kGy.

4. A method for manufacturing a printed material according to claim 1, wherein the printing speed is 50 to 300 m / min.

5. A method for manufacturing a printed material according to claim 1, wherein between step 1 and step 2, there is no step of irradiating with active energy rays to cure the active energy ray-curable offset printing ink.

6. The method for producing a printed article according to claim 1, wherein the active energy ray curable offset printing ink comprises a resin, a polyfunctional (meth)acrylate, and a colorant.

7. The method for manufacturing a printed article according to claim 1, wherein the active energy ray-curable flexographic printing ink includes an active energy ray-curable white flexographic printing ink.

8. The method for manufacturing a printed article according to claim 1, wherein the active energy ray-curable flexographic printing ink includes an active energy ray-curable flexographic printing varnish.

9. The method for manufacturing a printed article according to claim 1, wherein the substrate is a paper substrate or a transparent film substrate.

10. The method for manufacturing a printed article according to claim 9, wherein the thickness of the paper substrate is 50 μm to 150 μm.

11. The method for manufacturing a printed article according to claim 9, wherein the thickness of the transparent film substrate is 1 μm to 35 μm.

12. A method for manufacturing a printed material according to claim 1, wherein the printed material is used as packaging material.

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