Printing method

Abstract

The present invention addresses the problem of providing a production method in which printed matter of stable quality is obtained even by continuous printing, by combining a specific flexographic printing plate with an actinic-ray-curable ink.　In this production method for printed matter are used: a flexographic printing plate comprising a substrate and a resin layer having a printing relief; and an actinic-ray-curable ink comprising at least one polyfunctional (meth)acrylate and a pigment. The production method for printed matter satisfies the following (A) to (C). (A) The resin layer having a printing relief includes a compound A having an SP value, as calculated by the Fedors method, of 10.0 or greater, in an amount of 30 mass% or larger. (B) The polyfunctional (meth)acrylate has an SP value, as calculated by the Fedors method, of 8.0-9.5. (C) The ink has a content of the polyfunctional (meth)acrylate satisfying said SP value of 40-85 mass%.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a printed matter and an actinic energy ray-curable ink. [Background technology]

[0002] With the global population growing, demand for flexible packaging, primarily used for packaging food and household goods, is expected to continue to grow. Flexible packaging is generally described as a process in which plastic film is printed, then laminated to form a bag. Gravure printing, currently the mainstream method for flexible packaging printing in Asia, produces visually vibrant prints, while flexographic printing, the mainstream method for flexible packaging printing in Europe, is characterized by its simple operation and high productivity due to high-speed printing. However, both methods use inks containing large amounts of solvent, which requires a large amount of energy to dry the ink solvent and treat the exhaust, placing a significant burden on the environment. Furthermore, in recent years, there has been a demand for reduced volatile components in inks in response to environmental concerns and carbon neutrality.

[0003] For this reason, the use of actinic ray-curable inks, which do not contain volatile components and cure instantly upon irradiation with actinic ray, is being promoted in flexographic printing (Patent Document 1). In flexible packaging printing, which is performed by roll-to-roll printing, the quick drying of the ink is important, and actinic ray-curable flexographic printing, which uses actinic ray-curable inks, not only has environmental advantages but also saves energy and is highly productive because it shortens the drying process without using thermal energy.

[0004] Generally, actinic radiation-curable inks cure instantly upon exposure to actinic radiation, and therefore contain (meth)acrylates as their primary ingredient rather than solvents. In flexographic printing, ink is applied to the apex of the relief (protruding portion) and then pressed against the substrate to transfer the ink for printing. However, if the (meth)acrylates in the ink penetrate the relief portion of the flexographic printing plate, it swells with continued printing, causing the halftone dots to become thicker than they were at the start of printing and deteriorating print quality. Ink also tends to accumulate at the edges of the protruding portions, and a printing defect known as plate entanglement, in which ink adheres to areas other than the image lines, becomes more likely to occur with continued printing.

[0005] For this reason, a method has been proposed for suppressing ink entanglement by using a water-developable photosensitive flexographic printing plate precursor containing a fluorine-containing compound having an ionic functional group (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 69736 [Patent Document 2] International Publication No. 2018 / 88336 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 2, a certain degree of ink entanglement suppression effect can be achieved by improving the flexographic printing plate, but since plate entanglement is essentially a phenomenon that is affected by both the plate characteristics and the ink characteristics, the suppression effect may be limited depending on the ink.

[0008] Therefore, an object of the present invention is to provide a production method that can obtain printed matter of stable quality even in continuous printing by combining a specific flexographic printing plate with an active energy ray-curable ink. [Means for solving the problem]

[0009] That is, the present invention is a method for producing a printed matter using a flexographic printing plate including a substrate and a resin layer on which a printing relief is formed, and an actinic ray-curable ink including at least one type of polyfunctional (meth)acrylate and a pigment, wherein the method satisfies the following (A) to (C): (A) The resin layer on which the printing relief is formed contains 30% by mass or more of a compound A having an SP value of 10.0 or more as calculated by the Fedors method. (B) The polyfunctional (meth)acrylate has an SP value of 8.0 or more and 9.5 or less, as calculated by the Fedors method. (C) The content of the polyfunctional (meth)acrylate satisfying the SP value in the ink is 40% by mass or more and 85% by mass or less.

[0010] The present invention also relates to an active energy ray-curable ink containing at least one type of polyfunctional (meth)acrylate and a pigment, wherein the polyfunctional (meth)acrylate has an SP value of 8.0 or more and 9.5 or less as calculated by the Fedors method, and the polyfunctional (meth)acrylate contains tricyclodecane dimethanol diacrylate, and the content of the polyfunctional (meth)acrylate satisfying the SP value in the ink is 40% by mass or more and 85% by mass or less. [Effects of the Invention]

[0011] According to the method for producing printed matter of the present invention, by combining a specific flexographic printing plate with an active energy ray-curable ink, deformation of the plate due to ink components is suppressed, dot thickening and ink entanglement are suppressed, and printed matter of stable quality can be obtained even in continuous printing. In addition, the obtained printed matter exhibits excellent film adhesion. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be specifically described below. In the present invention, "or more" means the same as or greater than the indicated numerical value. Furthermore, "or less" means the same as or smaller than the indicated numerical value. Furthermore, "(meth)acrylate" is a general term including acrylate and methacrylate.

[0013] The present invention is a method for producing a printed matter using a flexographic printing plate including a substrate and a resin layer on which a printing relief is formed, and an actinic ray-curable ink including at least one type of polyfunctional (meth)acrylate and a pigment, wherein the method satisfies the following (A) to (C): (A) The resin layer on which the printing relief is formed contains 30% by mass or more of a compound A having an SP value of 10.0 or more as calculated by the Fedors method. (B) The polyfunctional (meth)acrylate has an SP value of 8.0 or more and 9.5 or less, as calculated by the Fedors method. (C) The content of the polyfunctional (meth)acrylate satisfying the SP value in the ink is 40% by mass or more and 85% by mass or less.

[0014] Satisfying the above conditions (A) to (C) means that the SP values ​​of the main components of the resin layer on which the printing relief is formed and the actinic energy ray-curable ink are different from each other, and therefore have low affinity. Because these main components have low compatibility with each other, the polyfunctional (meth)acrylate is less likely to swell the resin layer on which the printing relief is formed, suppressing deformation of the printing plate during continuous printing and stabilizing print quality.

[0015] The SP value (solubility parameter) in the present invention is a value calculated by the Fedors method (Robert F. Fedors, Polymer Engineering and Science, 14, 147-154 (1974)), and can be calculated using the following formula (1). δ=(E / V)1 / 2 …Equation (1) In equation (1), δ is the SP value, E is the cohesive energy (cal / mol), and V is the molar volume (cm3 / mol).

[0016] [Flexographic printing plate] The flexographic printing plate comprises a substrate and a resin layer on which a printing relief is formed.

[0017] (base material) The substrate is preferably one that has excellent dimensional stability against heat and physical stress, and may be a plastic sheet such as polyester, or a metal plate such as steel, stainless steel, or aluminum.

[0018] The thickness of the substrate is preferably 100 μm or more and 350 μm or less from the viewpoint of handleability and flexibility. If it is 100 μm or more, the handleability as a support is improved, and if it is 350 μm or less, the flexibility as a flexographic printing plate is improved.

[0019] (resin layer) The resin layer on which the printing relief is formed contains a compound A having an SP value of 10.0 or more as calculated by the Fedors method. The SP value of the compound A is preferably 12.0 or more, since this results in lower compatibility with ink and stable continuous printing quality.

[0020] Conventional general flexographic plates are made from rubber components, are highly hydrophobic, and have an SP value of less than 10, which makes them similar in polarity to actinic ray-curable inks and makes them prone to swelling. If a (meth)acrylate with a higher polarity, i.e., an SP value of more than 10, were combined, similar swelling suppression could be expected, but (meth)acrylates with polar groups have high viscosity, making it practically difficult to adjust the viscosity of actinic ray-curable inks to a level suitable for flexographic printing.

[0021] Therefore, in the present invention, the SP value of the flexographic printing plate is increased by the compound A, and a polyfunctional (meth)acrylate having an SP value lower than that of the compound A is contained in the actinic ray-curable ink described below. This makes it possible to adjust the viscosity of the actinic ray-curable ink to a value suitable for flexographic printing, while suppressing deformation of the plate due to ink components.

[0022] The compound A is preferably at least one selected from nitrile butadiene rubber, urethane rubber, chlorinated polyethylene, vinyl acetate rubber, polyvinyl alcohol, polyamide, polyurethane, polyvinylpyrrolidone, polyether, and polyester. These rubbers and resins have a highly hydrophilic functional group in the main chain or can be easily introduced into the side chain, and can suppress swelling due to ink.

[0023] The compound A preferably has at least one of a hydroxyl group and an ethylene oxide group, since these highly hydrophilic functional groups have low compatibility with hydrophobic functional groups.

[0024] Furthermore, it is preferable that the compound A does not contain a (meth)acrylate group. When the compound A does not contain a (meth)acrylate group, the affinity with the polyfunctional (meth)acrylate that is the main component of the ink of the present invention can be reduced.

[0025] The resin layer contains 30% by mass or more of the compound A. By containing 30% by mass or more, preferably 50% by mass or more of the compound A, compatibility with ink is reduced and continuous printing quality is stabilized. In addition, to leave room for adding additives such as photopolymerization initiators and ultraviolet absorbers, the content of the compound A is preferably 99.5% by mass or less.

[0026] The resin layer may also contain a plasticizer to adjust the hardness of the printing relief.

[0027] Furthermore, the resin layer preferably has a swelling ratio of 5% by mass or less after contact with 1,6-hexanediol diacrylate at 25°C for 24 hours. 1,6-Hexanediol diacrylate has an SP value of 9.5. Having a swelling ratio of 5% by mass or less after contact with 1,6-hexanediol diacrylate under the above conditions results in low swelling with the compound and low swelling with the ink used in the method for producing printed matter of the present invention, resulting in stable continuous printing quality.

[0028] [Active energy ray curable ink] The active energy ray-curable ink used in the method for producing a printed matter of the present invention and the active energy ray-curable ink of the present invention (hereinafter, when explaining the characteristics common to both, they will be collectively referred to as "the active energy ray-curable ink of the present invention") contain at least one or more types of polyfunctional (meth)acrylate and a pigment.

[0029] (Multifunctional (meth)acrylate) The polyfunctional (meth)acrylate contained in the actinic ray-curable ink used in the method for producing printed matter of the present invention preferably contains an alicyclic skeleton or an aliphatic skeleton having 6 to 18 carbon atoms, as this reduces swelling of the flexographic printing plate used in the present invention. In particular, it is preferable to contain tricyclodecane dimethanol diacrylate, which has low swelling properties and also high adhesion to substrates.

[0030] The polyfunctional (meth)acrylate contained in the active energy ray-curable ink of the present invention includes tricyclodecane dimethanol diacrylate.

[0031] Specific examples of the polyfunctional (meth)acrylate include, in the case of bifunctional compounds, 1,6-hexanediol di(meth)acrylate (SP value 9.5), 1,9-nonanediol di(meth)acrylate (SP value 9.4), 1,10-decanediol di(meth)acrylate (SP value 9.3), tripropylene glycol di(meth)acrylate (SP value 9.3), polypropylene glycol di(meth)acrylate (SP value 9.1), neopentyl glycol di(meth)acrylate (SP value 9.2), and dicyclopentadiene tricyclodecane dimethanol di(meth)acrylate (SP value 9.2), and in the case of trifunctional compounds, propylene oxide adduct of trimethylolpropane tri(meth)acrylate (SP value 9.4) can be mentioned. Among these, tricyclodecane dimethanol diacrylate is preferred.

[0032] The polyfunctional (meth)acrylate includes those having an SP value of 8.0 or more and 9.5 or less, as calculated by the Fedors method. When the polyfunctional (meth)acrylate includes those having an SP value of 9.5 or less, preferably 9.3 or less, compatibility with flexographic printing plates is reduced, resulting in stable continuous printing quality. Furthermore, to reduce compatibility with flexographic printing plates, the polyfunctional (meth)acrylate is not made to have a higher SP value than the SP value of the resin layer, but rather is made to have a lower SP value. This prevents the increase in viscosity of the polyfunctional (meth)acrylate due to the presence of polar groups, making it easy to adjust the viscosity of the actinic ray-curable ink to a value suitable for flexographic printing. Furthermore, when the polyfunctional (meth)acrylate includes those having an SP value of 8.0 or more, excellent photosensitivity patterning properties are achieved.

[0033] The content of the polyfunctional (meth)acrylate in the ink that satisfies the SP value is 40% by mass or more and 85% by mass or less. A content of 40% by mass or more, preferably 50% by mass or more, reduces compatibility with flexographic printing plates, stabilizing continuous printing quality. Furthermore, the content is 85% by mass or less, preferably 80% by mass or less.

[0034] The polyfunctional (meth)acrylate preferably does not contain an alkylene oxide group, which can prevent swelling of the flexographic printing plate.

[0035] The number average molecular weight of the polyfunctional (meth)acrylate is preferably 200 or more and 700 or less, which allows the swelling property of the flexographic printing plate and the curability against active energy rays to be maintained well.

[0036] (oligomer) Oligomers can also be used to impart appropriate viscoelasticity to the ink. Specific examples include oligomers of acrylic resin, polyurethane, polyester, phthalate resin, etc., and those with a weight-average molecular weight of 10,000 or less are preferred.

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

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

[0039] (Photopolymerization initiator) The active energy ray-curable ink of the present invention preferably contains a photopolymerization initiator, because the polyfunctional (meth)acrylate is used to dissolve the photopolymerization initiator, thereby reducing swelling of the flexographic printing plate.

[0040] On the other hand, decomposition products and unreacted products of the photopolymerization initiator can cause odors and contaminate the contents, so depending on the application, radiation-curable inks that do not contain these may be more preferable.

[0041] (Other additives) In addition, additives such as wax, pigment dispersant, antifoaming agent, and leveling agent can be used in the active energy ray-curable ink of the present invention.

[0042] The actinic radiation-curable ink of the present invention preferably does not substantially contain components that can swell flexographic printing plates, such as water and solvents. "Substantially free" here means that the total content of water and solvents in the ink is 0.5% by mass or less.

[0043] The active energy ray-curable ink of the present invention can be synthesized by adding a pigment and any additives to a varnish in which a polyfunctional (meth)acrylate and any oligomer or monofunctional (meth)acrylate are dissolved, and dispersing and mixing the mixture using an attritor, ball mill, sand mill, or the like.

[0044] [Print material] In the method for producing a printed matter of the present invention, the substrate to be printed may be coated paper such as art paper, coated paper, or cast paper, uncoated paper such as fine paper, newsprint, or Japanese paper, or non-absorbing raw material such as synthetic paper, aluminum-deposited paper, metal, or film.

[0045] Examples of the film include polyesters such as polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, and polylactic acid, polyamide, polyimide, polyalkyl(meth)acrylate, polystyrene, poly-α-methylstyrene, polycarbonate, polyvinyl alcohol, polyvinyl acetal, polyvinyl chloride, and polyvinylidene fluoride.

[0046] The film may be subjected to a surface treatment such as burning, easy-adhesion coating, or chemical vapor deposition.

[0047] The thickness of the film is preferably 5 μm or more, more preferably 10 μm or more, in terms of the mechanical strength of the film required for printing, if the film is a single layer film, and is preferably 50 μm or less, more preferably 30 μm or less, in order to reduce the cost of the film.

[0048] When surface printing is performed on an already laminated multilayer film, the thickness of the film is preferably 50 μm or more and 200 μm or less.

[0049] The form of the printing substrate may be either sheet or roll. When printing on a thin film for flexible packaging, it is preferable to use a roll film and perform roll-to-roll printing.

[0050] [Irradiation process] In the irradiation step of the method for producing a printed matter of the present invention, examples of sources of active energy rays include ultraviolet rays (particularly LED-UV), electron beams, and gamma rays. Radiation such as electron beams and gamma rays generates high-energy secondary electrons in the irradiated material, exciting surrounding molecules and generating reactive species such as radicals. When the irradiated material is an active energy ray-curable ink, radicals are generated in the ink, which then undergoes radical polymerization, resulting in a cured ink film.

[0051] In particular, electron beams generated at low acceleration voltages have sufficient penetration into ink films with thicknesses of 10 μm or less, and can provide the energy necessary for curing. Furthermore, they are preferred because they require no special qualifications for use and are easy to handle.

[0052] The penetration depth of an electron beam is determined by the acceleration voltage, so the acceleration voltage of the electron beam is preferably 50 kV or more, more preferably 90 kV or more, and even more preferably 110 kV or more, so that a sufficient dose of radiation penetrates the ink film. Furthermore, as the penetration depth increases, the dose of radiation imparted to the interior of the printed material also increases, so the acceleration voltage is preferably 300 kV or less, more preferably 200 kV or less, and even more preferably 150 kV or less.

[0053] Furthermore, the higher the electron beam irradiation dose, the greater the amount of radical species generated in the target material, but also the greater the damage to the printed material. Therefore, the irradiation dose is preferably 10 kGy or more and 100 kGy or less, and more preferably 20 kGy or more and 50 kGy or less. [Example]

[0054] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0055] [Evaluation method] (1) Test printing The flexographic printing press (UTECO "ONYX XS" ECO ONE 800) was equipped with an anilox roll (PRAXAIR SURFACE TECHNOLOGIES "NOVA GOLD" 460 lpi, 2.5 ml / m 3 Various flexographic printing plates were attached using a tape ("DUPLO FLEX" 5.3 Medium, manufactured by Lohmann Tape) and cushion tape, and various actinic radiation-curable inks were transferred to a 25 μm-thick PET film ("Lumirror" T-25, manufactured by Toray Industries, Inc.) at a printing speed of 200 m / min. The ink was then cured by electron beam irradiation at an acceleration voltage of 110 kV and an exposure dose of 30 kGy to obtain printed matter. 2000 m of continuous printing was carried out for each standard, and samples were taken at the start of printing and every 500 m printed.

[0056] (2) Swelling rate of the plate A 2cm x 2cm section was cut from the solid area of ​​the plate to be evaluated, approximately 0.8mm deep from the surface, and 1,6-hexanediol diacrylate was brought into contact with the front surface of the solid area for 24 hours at 25°C. The 1,6-hexanediol diacrylate was then wiped off with gauze, and the rate of mass change before and after contact relative to the mass before contact was calculated. The average of the two measurements was taken as the swelling rate.

[0057] (3) Dot thickening Dot gain values ​​were measured using a reflection densitometer (SpectroEye, manufactured by GretagMacbeth) for the 25% halftone dot area of ​​the print. The values ​​were measured for the print at the start and end of printing, and if the change was within ±4%, it was judged that there was no distortion of the halftone dots and that the quality was stable. If the change was within ±2%, it was judged to be extremely good.

[0058] (4) Edition issues The presence or absence of plate entanglement was evaluated in the highlight areas (20% or less halftone dots) of the printed matter. A: Throughout the 2000m of continuous printing, no plate tangling was observed. B: No plate tangling was observed from the start of printing until 1500m, but plate tangling was observed at 2000m. C: No plate tangling was observed from the start of printing until 1000 m, but plate tangling was observed at 1500 m. D: No plate tangling was observed up to 500m from the start of printing, but plate tangling was observed at 1000m. E: Plate tangling was observed 500m after the start of printing.

[0059] (5) Laminate peel strength A mixed laminating adhesive (Takelac A626 / Takenate A-50 manufactured by Mitsui Chemicals, Inc.) was applied to the printed matter obtained by the test printing at the start of printing to a film thickness of 3.0 g / m. 2The coated sample was then laminated with a 60 μm thick unstretched polypropylene film (CPP) (ZK-297, manufactured by Toray Advanced Film Co., Ltd.). The sample was then aged at 40°C for 3 days to obtain a laminated sample. The ink-filled area of ​​the laminated sample was cut into 15 mm wide strips, and the peel strength was measured using a Tensilon universal testing machine (RTG-1210, manufactured by Orientec Co., Ltd.) when peeled at a 90° angle at 300 mm / min.

[0060] When the peel strength was less than 1.0 N / 15 mm, the adhesion was evaluated as insufficient; when it was 1.0 N / 15 mm or more but less than 1.5 N / 15 mm, the adhesion was evaluated as somewhat good; when it was 1.5 N / 15 mm or more but less than 2.0 N / 15 mm, the adhesion was evaluated as good; when it was 2.0 N / 15 mm or more but less than 3.0 N / 15 mm, the adhesion was evaluated as fairly good; and when it was 3.0 N / 15 mm or more, the adhesion was evaluated as extremely good.

[0061] [Ink raw materials] Pigment: LIONOL BLUE FG7330 (manufactured by Toyo Color Co., Ltd.) Pigment dispersant: "Disperbyk" (registered trademark) 2012 (manufactured by BYK-Chemie) Multifunctional (meth)acrylate 1:1,9-nonanediol diacrylate ("Light Acrylate" (registered trademark) 1,9ND-A, manufactured by Kyoeisha Chemical Co., Ltd.), SP value 9.4, no alicyclic structure Multifunctional (meth)acrylate 2: tripropylene glycol diacrylate ("Miramer" (registered trademark) M220 manufactured by Miwon), SP value 9.3, no alicyclic skeleton, alkylene oxide group Multifunctional (meth)acrylate 3: polyethylene glycol diacrylate ("Miramer" (registered trademark) M280 manufactured by Miwon), SP value 9.7, no alicyclic skeleton, alkylene oxide group Multifunctional (meth)acrylate 4: Tricyclodecane dimethanol diacrylate ("NK Ester" (registered trademark) A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd.), SP value 9.2, containing an alicyclic skeleton Oligomer: Urethane acrylate (Kyoeisha Chemical Co., Ltd. UF-8001G) Polymerization inhibitor: p-methoxyphenol (manufactured by Wako Pure Chemical Industries, Ltd.).

[0062] [Ink preparation] The ink compositions shown in Table 1, including pigments, polyfunctional (meth)acrylates, oligomers, and other auxiliaries, were weighed and dispersed using a batch sand mill (manufactured by Hayashi Shoten Co., Ltd.) to obtain active energy ray-curable inks 1 to 6.

[0063] [Table 1]

[0064] When commercially available inks were used, the following product numbers were used. Ink 7: PHA (manufactured by T&K TOKA Corporation), containing 40% by mass or more and 80% by mass or less of a multifunctional (meth)acrylate with an SP value of 9.3. Ink 8: PHA-L03 (UV flexographic ink manufactured by T&K TOKA Corporation), containing less than 40% by mass of polyfunctional (meth)acrylate with an SP value of 9.5 or less.

[0065] [Raw materials for flexographic printing plates] Binder resin 1: Partially saponified polyvinyl alcohol ("JR-05" manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.) was reacted with 1.0 mol% succinic anhydride, and then all of the carboxylic acid moieties were reacted with glycidyl methacrylate to convert them to (meth)acrylate groups. SP value: 12.4 Binder resin 2: Nitrile butadiene rubber (N220S manufactured by JSR Corporation), SP value 10.1 Monomer 1: polyethylene glycol monomethacrylate (NOF Corporation, "Blenmer" (registered trademark) AE400), SP value 10.4 Monomer 2: 1:2 adduct of tripropylene glycol and glycidyl acrylate (hydroxyl group bifunctional, NOF Corporation "Epoxy Ester" (registered trademark) 200PA), SP value 11.3 Additive: Trimethylolpropane tri(polyethylene glycol) ether (weight average molecular weight: 400, Nippon Nyukazai Co., Ltd. TMP-60), SP value 10.5 Photopolymerization initiator: 1-hydroxycyclohexyl dimethyl ketone Ultraviolet absorber: 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole.

[0066] [Preparation of flexographic printing plate precursor] Various raw materials were weighed according to the composition shown in Table 2 and dissolved in a mixed solvent of alcohol mixture ("Solmix" (registered trademark) H-11, manufactured by Nippon Alcohol Co., Ltd.) and water. The solution was then applied to a 188 μm thick polyester (PET) film ("Panaclea" (registered trademark) ACM188, manufactured by Panac Corporation) with an easy-adhesion layer, with the dry film thickness adjusted to 1.14 mm, and dried at 60° C. for 2.5 hours. A 50 / 50 water / ethanol mixed solvent by mass was applied to the obtained photosensitive resin layer, and a laminated film with a heat-sensitive mask layer was pressure-bonded to obtain flexographic printing plate precursors 1 and 2.

[0067] [Table 2]

[0068] When a commercially available flexographic printing plate precursor was used, the following product numbers were used. Flexographic printing plate precursor 3: DF114HR2 (manufactured by Toray Industries, Inc.), containing 30% by mass or more of a compound with an SP value of 10.0 or more. Flexographic printing plate precursor 4: NX114 (manufactured by KODAK Co., Ltd.), containing no compounds with an SP value of 10.0 or more.

[0069] [Flexographic printing plate production] A high-intensity chemical lamp (Philips TL-K 40W / 10R) was used to illuminate the flexographic printing plate precursor from the substrate side, with an integrated light intensity of 700 mJ / cm. 2Then, an image mask was formed from the heat-sensitive mask layer by laser drawing using an external drum type plate setter (Esco Graphics Corporation, "CDI SPARK" 2530). Then, in the same manner as for the back exposure, a high-intensity chemical lamp (TL-K 40W / 10R) was used in the atmosphere, with an integrated light intensity of 12,000 mJ / cm. 2 The film was then developed for 80 seconds in tap water adjusted to 25°C using a batch exposure developer (Inglese, srl "Inglese" W43) and dried in an oven at 60°C for 10 minutes. It was then exposed to a high-intensity chemical lamp (TL-K 40W / 10R) with an integrated light intensity of 12,000 mJ / cm. 2 A post-exposure was carried out so that the thickness of the flexographic printing plate became 1 / 3 of the thickness of the flexographic printing plate.

[0070] [Example 1] A flexographic printing plate was prepared using flexographic printing plate precursor 3 as the flexographic printing plate precursor, and printing was performed using ink 1 as the ink. The swelling ratio of the flexographic printing plate was small at 2.1%, making it difficult to deform. No ink entanglement was observed during printing, and dot thickening was also very good at 2%. The laminate peel strength was also good at 1.8 N / 15 mm. The results are shown in Table 3.

[0071] [Examples 2 to 6] Printing was carried out in the same manner as in Example 1, except that inks 2 to 5 and 7 were used.

[0072] In all of Examples 2 to 6, continuous printing quality was stable. When the content of polyfunctional (meth)acrylates with an SP value of 9.5 or less was low, ink entanglement tended to occur more easily, while when the content was high, dot thickening tended to increase. In particular, Example 5, which used tricyclodecane dimethanol diacrylate, not only exhibited stable printing quality but also very good adhesion of printed matter. The results are shown in Table 3.

[0073] [Examples 7 and 8] Printing was carried out in the same manner as in Example 1, except that flexographic printing plate precursors 1 and 2 were used as the flexographic printing plate precursors. It was observed that when the swelling ratio of the flexographic printing plate was high, the halftone dots also tended to become thicker. The results are shown in Table 3.

[0074] [Comparative Example 1] Printing was carried out in the same manner as in Example 1, except that commercially available flexographic printing plate precursor 4 was used as the flexographic printing plate precursor. Ink entanglement was observed 500 meters after the start of printing, and dot thickening was significant at 6%, and print quality deteriorated as printing continued. The results are shown in Table 3.

[0075] Comparative Example 2 Printing was carried out in the same manner except that Ink 6 was used. Since Ink 6 contains a polyfunctional (meth)acrylate with a large SP value and high hydrophilicity, the dots appeared to thicken. The results are shown in Table 3.

[0076] Comparative Example 3 A flexographic printing plate was prepared using flexographic printing plate precursor 4 as the flexographic printing plate precursor, and printing was performed using ink 6 as the ink. Although the dots were thickened well, ink entanglement was likely to occur. The results are shown in Table 3.

[0077] Comparative Example 4 A flexographic printing plate was prepared using flexographic printing plate precursor 3 as the flexographic printing plate precursor, and printing was performed using ink 8 as the ink. Although no ink adhesion was observed up to 2000 m after the start of printing, there was a tendency for the halftone dots to become thinner, suggesting that components of the flexographic plate were being extracted into the ink. The results are shown in Table 3.

[0078] [Table 3]

Claims

1. A method for producing a printed matter using a flexographic printing plate including a substrate and a resin layer on which a printing relief is formed, and an actinic ray-curable ink including at least one type of polyfunctional (meth)acrylate and a pigment, wherein the method satisfies the following (A) to (C): (A) The resin layer on which the printing relief is formed contains 30% by mass or more of a compound A having an SP value of 10.0 or more as calculated by the Fedors method. (B) The polyfunctional (meth)acrylate has an SP value calculated by the Fedors method of 8.0 or more and 9.5 or less. (C) The content of the polyfunctional (meth)acrylate satisfying the SP value in the ink is 40% by mass or more and 85% by mass or less.

2. The method for producing a printed matter according to claim 1, wherein the resin layer has a swelling rate of 5% by mass or less after being brought into contact with 1,6-hexanediol diacrylate at 25° C. for 24 hours.

3. The method for producing a printed matter according to claim 1 or 2, wherein the compound A has at least one of a hydroxyl group and an ethylene oxide group.

4. The method for producing a printed matter according to claim 1 or 2, wherein the compound A does not contain a (meth)acrylate group.

5. 3. The method for producing a printed matter according to claim 1, wherein the compound A is at least one selected from the group consisting of nitrile butadiene rubber, urethane rubber, chlorinated polyethylene, vinyl acetate rubber, polyvinyl alcohol, polyamide, polyurethane, polyvinylpyrrolidone, polyether, and polyester.

6. The method for producing a printed matter according to claim 1 or 2, wherein the number average molecular weight of the polyfunctional (meth)acrylate is 200 or more and 700 or less.

7. The method for producing a printed matter according to claim 1 or 2, wherein the polyfunctional (meth)acrylate does not contain an alkylene oxide group.

8. The method for producing a printed matter according to claim 1 or 2, wherein the polyfunctional (meth)acrylate contains an alicyclic skeleton or an aliphatic skeleton having 6 to 18 carbon atoms.

9. The method for producing a printed matter according to claim 1 or 2, wherein the polyfunctional (meth)acrylate is tricyclodecane dimethanol diacrylate.

10. The method for producing a printed matter according to claim 1 or 2, wherein the active energy ray-curable ink contains a photopolymerization initiator.

11. The method for producing a printed matter according to claim 1 or 2, wherein the actinic ray-curable ink is substantially free of water and solvent.

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