Flexographic printing plate precursor, flexographic printing plate and method for producing printed material using the same

Abstract

To provide a flexographic printing plate precursor that enables production of a flexographic printing plate with superior print durability, which exhibits resistance to printing omissions due to foreign matter even during long-run printing.SOLUTION: A flexographic printing plate precursor has a relief forming layer that contains a resin (A) with ionic groups and a surfactant (B) with a hydrocarbon group of 10 or more carbon atoms and ionic groups capable of forming counterions with the resin (A).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a flexographic printing plate precursor, a flexographic printing plate and a method for producing the same, and a method for producing a printed matter using the same. [Background technology]

[0002] Taking advantage of its flexibility, flexographic printing is widely used in applications such as paper containers, labels, soft packaging, and electronics. Flexographic printing is a printing method in which ink is applied to the apexes of the raised relief of a flexographic printing plate, and the relief is pressed against the substrate, thereby transferring the ink from the relief to the substrate. If foreign matter such as dust, dirt, or paper powder adheres to the relief at this time, the ink does not adhere to the area around the foreign matter, and the ink is not transferred to the substrate, resulting in a printing defect known as a print defect.

[0003] In view of this, as a technique for reducing adhesion of foreign matter such as dust, dirt, and paper powder to the relief, there has been proposed, for example, a photosensitive resin original plate for flexographic printing, which comprises a photosensitive resin layer composed of a water-developable photosensitive resin composition for flexographic printing, which comprises at least (a) polyamide and / or polyamide block copolymer, (b) a crosslinking agent having one or more unsaturated groups, (c) a photopolymerization initiator, and (d) a fatty acid, wherein the (d) fatty acid is one or a mixture of two or more selected from fatty acids having 12 to 22 carbon atoms, and the ratio of the (d) fatty acid in the photosensitive resin composition is 0.5 to 8.0 wt %, a support, and an adhesive layer for adhering them (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 43006 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the photosensitive resin original plate for flexographic printing disclosed in Patent Document 1 has a problem in that fatty acids in the photosensitive resin layer are easily extracted into the ink during the printing process, and when the flexographic printing plate is used for long runs or repeatedly, foreign matter tends to adhere to the plate, causing printing defects due to the foreign matter.

[0006] In view of the above problems, the present invention has an object to provide a flexographic printing plate precursor that can provide a flexographic printing plate having excellent printing durability and is less susceptible to printing defects caused by foreign matter even in long-run printing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention mainly has the following configuration. <1> A flexographic printing plate precursor having a relief-forming layer containing a resin (A) having an ionic group and a surfactant (B) having a hydrocarbon group having 10 or more carbon atoms and an ionic group capable of forming a counter ion with the resin (A). <2> The ionic group has a carboxyl group and / or a carboxylate salt. <1> 1. The flexographic printing plate precursor according to claim 1. <3> The surfactant (B) has a structure represented by the following general formula (1): <1> or <2> 1. The flexographic printing plate precursor according to claim 1.

[0008] [ka]

[0009] (In the above general formula (1), R1 represents an alkyl group or an alkenyl group having 10 or more carbon atoms. R2 represents a hydrogen atom, an alkyl group having 1 to 28 carbon atoms, or a benzyl group. R3 and R4 may be the same or different and represent an alkyl group having 1 to 5 carbon atoms. An - indicates a monovalent anion.) <4> The relief-forming layer further contains a hydroxycarboxylic acid (C). <1> ~ <3> 10. The flexographic printing plate precursor according to claim 9, <5> The hydroxycarboxylic acid (C) contains diglucosyl gallic acid. <4> 1. The flexographic printing plate precursor according to claim 1. <6> <1> ~ <5> 2. A method for producing a flexographic printing plate, comprising a step of partially removing the relief-forming layer of the flexographic printing plate precursor according to any one of claims 1 to 11 to form a relief. <7> A flexographic printing plate having a relief layer containing a resin (A) having an ionic group and a surfactant (B) having a hydrocarbon group having 10 or more carbon atoms and an ionic group capable of forming a counter ion with the resin (A). <8> <7> 2. A method for producing a printed matter, comprising the steps of: depositing ink on the relief of the flexographic printing plate according to claim 1; and transferring the ink to a substrate. <9> The ink is an ultraviolet-curable ink and / or an electron beam-curable ink. <8> A method for producing the printed matter described above. Effect of the Invention

[0010] According to the flexographic printing plate precursor of the present invention, a flexographic printing plate excellent in printing durability and less prone to printing voids due to foreign matter even during long-run printing can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The flexographic printing plate precursor (hereinafter may be referred to as "printing plate precursor") according to the present invention is a precursor of a flexographic printing plate (hereinafter may be referred to as "printing plate") used in flexographic printing, and preferably has at least a support and a relief-forming layer in this order. A primer layer, an adhesive layer, etc. may be present between the support and the relief-forming layer.

[0012] The support serves to support the relief-forming layer. The support is preferably made of a material that is flexible and has excellent dimensional stability. Specific examples include plastic sheets such as polyester, and metal plates such as steel, stainless steel, and aluminum. Two or more of these may be used.

[0013] The thickness of the support is preferably in the range of 100 to 350 μm from the viewpoints of ease of handling and flexibility.

[0014] The relief-forming layer is a layer that becomes a relief in a flexographic printing plate. Examples of the relief-forming layer include a photosensitive resin layer that undergoes polymerization by absorption of electromagnetic energy rays such as ultraviolet light and becomes insoluble in a developer, and a resin layer that can be engraved into a desired shape by electromagnetic energy rays such as laser light. The photosensitive resin layer can form a desired relief by, for example, irradiating it with ultraviolet light in an imagewise manner. Among these, a photosensitive resin layer is preferred from the viewpoints of productivity and image reproducibility of the printing plate.

[0015] The relief-forming layer contains a resin (A) having an ionic group (hereinafter, sometimes referred to as "resin (A)") and a surfactant (B) having an ionic group capable of forming a counter ion with the resin (A) and a hydrocarbon group having 10 or more carbon atoms (hereinafter, sometimes referred to as "surfactant (B)"). The surfactant (B) has the effect of suppressing the adhesion of the relief to the relief in the printing plate described later, and suppressing adhesion of dust, dirt, paper powder, etc., which cause print defects due to foreign matter, to the relief. The resin (A) acts as a binder resin that maintains the shape of the relief-forming layer, and also holds the surfactant (B) in the relief-forming layer by ionic bonding with the ionic group of the surfactant (B). This effect is the same in the relief of the printing plate described later, and has the effect of suppressing extraction of the surfactant (B) into the ink. In other words, the combination of the resin (A) and the surfactant (B) can suppress print defects due to foreign matter in the printing plate even in long-run printing, and improve print durability. Furthermore, it is preferable that the relief-forming layer contains a hydroxycarboxylic acid (C), which makes it easier to retain the surfactant (B) in the relief-forming layer, thereby enabling the printing durability of the printing plate to be further improved.

[0016] In the case of a photosensitive resin layer, the resin (A) is preferably a water-swellable or water-soluble resin, and since development can be performed using water as a developer, the environmental load can be reduced. The water-swellable or water-soluble resin refers to a polymer having a hydrophilic group, and the hydrophilic group is preferably a hydroxyl group, an amino group, an amide group, a carboxyl group, a phosphoric acid group, an ethylene glycol skeleton, or the like. Two or more of these may be contained. Examples of water-swellable or water-soluble polymers include partially saponified polyvinyl alcohol, polyamide, polyvinylpyrrolidone, polyether, and water-soluble polyester. Two or more of these may be contained. Among these, partially saponified polyvinyl alcohol is preferred from the viewpoint of water solubility and processability.

[0017] The degree of saponification of the partially saponified polyvinyl alcohol is preferably 60 mol% or more and 90 mol% or less from the viewpoint of water developability. Here, the degree of saponification can be calculated by subjecting a 3% by mass aqueous solution of partially saponified polyvinyl alcohol to a complete saponification treatment with an excess of 0.5 mol / l aqueous sodium hydroxide solution, and then measuring the amount of sodium hydroxide required for complete saponification by titration with 0.5 mol / l hydrochloric acid.

[0018] Since partially saponified polyvinyl alcohol has hydroxyl groups, when printing is performed on paper containing cellulose fibers as a printing substrate, conventional printing plates tend to cause paper powder to adhere to the relief surface due to hydrogen bonds between the hydroxyl groups in the cellulose fibers and the hydroxyl groups of the partially saponified polyvinyl alcohol in the relief. In the present invention, printing durability can be improved even when partially saponified polyvinyl alcohol is used as resin (A).

[0019] Examples of the ionic group contained in the resin (A) include anionic groups and cationic groups. Examples of the anionic group include carboxy groups, sulfonyl groups, phosphoric acid groups, and derivatives such as salts thereof. Examples of the cationic group include quaternary ammonium, tertiary amine, and salts thereof. Two or more of these may be included. These ionic groups may be bonded to the side chain of the resin, or may be included as a part of the main chain. Among these, carboxy groups and carboxylates are preferred from the viewpoint of ease of resin synthesis. Examples of a method for introducing a carboxy group into a partially saponified polyvinyl alcohol include a method in which a partially saponified polyvinyl alcohol is reacted with an acid anhydride, and a carboxy group is introduced into the partially saponified polyvinyl alcohol side chain starting from the hydroxyl group of the partially saponified polyvinyl alcohol. In this method, the amount of the carboxy group introduced can be easily adjusted to a desired range by the amount of the acid anhydride added and the reaction time.

[0020] In the case of a photosensitive resin layer, the resin (A) preferably has an ethylenic double bond in a side chain from the viewpoint of sensitivity. Examples of groups having an ethylenic double bond include vinyl groups, acryloyl groups, and methacryloyl groups. Two or more of these may be included.

[0021] As a method for introducing an ethylenic double bond into the side chain of the above-mentioned partially saponified polyvinyl alcohol having a carboxy group, for example, a method of reacting an unsaturated epoxy compound with the carboxy group can be mentioned.

[0022] The content of the resin (A) in the relief-forming layer is preferably 20% by weight or more and 80% by weight or less based on the solid content.

[0023] The surfactant (B) has an ionic group capable of forming a counter ion with the resin (A), and is therefore held in the relief-forming layer by ionic bonds with the resin (A). This action is the same in the relief of the printing plate described below, and the surfactant (B) can be suppressed from being extracted into the ink. Here, the surfactant (B) has a hydrocarbon group having 10 or more carbon atoms, and thus can suppress interactions with, for example, hydroxyl groups of cellulose fibers of paper powder. This suppresses the adhesion of the relief to the printing plate, and suppresses adhesion of dust, dirt, paper powder, and the like, which are the cause of print voids due to foreign matter, to the relief, thereby suppressing print voids due to foreign matter even in long-run printing, and improving print durability.

[0024] The ionic group in the surfactant (B) may be an anionic group, a cationic group, or the like, exemplified as the ionic group in the resin (A) described above. When the resin (A) has an anionic group, a cationic group is preferred, and when the resin (A) has a cationic group, an anionic group is preferred. Among the cationic groups, quaternary ammonium is preferred.

[0025] Examples of the hydrocarbon group having 10 or more carbon atoms in the surfactant (B) include alkyl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, aryl groups, and arylalkyl groups. Some of these hydrogen atoms may be substituted, and examples of the substituent include nitro groups, thiol groups, and amino groups. From the viewpoint of suppressing adhesion of dust, dirt, paper powder, etc., which cause print voids due to foreign matter, to the relief, suppressing print voids due to foreign matter even in long-run printing, and improving print durability, the carbon number of the hydrocarbon group is 10 or more, and preferably 16 or more. On the other hand, from the viewpoint of dispersibility in the photosensitive resin layer, the carbon number of the hydrocarbon group is preferably 24 or less.

[0026] The surfactant (B) is a cationic surfactant, and examples thereof include quaternary ammonium salts such as alkyl quaternary ammonium salts and alkyl ether quaternary ammonium salts, tertiary amines such as hydroxyether alkylamines, ether amines, and alkylamidoamines, and salts thereof. Two or more of these may be contained. Among these, alkyl quaternary ammonium salts are preferred.

[0027] The surfactant (B) preferably has a structure represented by the following general formula (1).

[0028] [ka]

[0029] In the above general formula (1), R1 represents an alkyl group or an alkenyl group having 10 or more carbon atoms. Among these, an alkyl group is preferable, and a linear alkyl group is more preferable. The number of carbon atoms of the alkyl group is preferably 16 or more and 28 or less.

[0030] R2 represents a hydrogen atom, an alkyl group having 1 to 28 carbon atoms, or a benzyl group. Among these, an alkyl group is preferable, and a linear alkyl group is more preferable. The number of carbon atoms in the alkyl group is preferably 1 to 6, and more preferably 1.

[0031] R3 and R4 may be the same or different and each represents an alkyl group having 1 to 5 carbon atoms. The alkyl group is preferably a linear alkyl group. The number of carbon atoms in the alkyl group is more preferably 1.

[0032] An - represents a monovalent anion. Examples of the monovalent anion include halide ions such as chloride ion and bromide ion, and organic anions such as ethyl sulfate ion and methyl carbonate ion. Among these, halide ions are preferred, and chloride ions are more preferred.

[0033] As the surfactant (B) having a structure represented by the general formula (1), for example, a mono-long-chain alkyl quaternary ammonium salt (wherein R1 is an alkyl group having 10 to 28 carbon atoms, R2 is an alkyl group having 1 to 6 carbon atoms, and R3 and R4 are alkyl groups having 1 to 5 carbon atoms) is preferable, and specific examples thereof include alkyl trimethyl ammonium chlorides such as lignoceryl trimethyl ammonium chloride, behenyl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, lauryl trimethyl ammonium chloride, and decyl trimethyl ammonium chloride. Two or more of these may be contained. Among these, behenyl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, and cetyl trimethyl ammonium chloride are preferable.

[0034] The content of solids in the surfactant (B) in the relief-forming layer is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 1.0% by weight or more, based on the solids, from the viewpoints of further suppressing adhesion of dust, dirt, paper powder, and the like, which cause printing defects due to foreign matter, to the relief and further improving printing durability. On the other hand, the content of solids in the surfactant (B) is preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less, based on the solids, from the viewpoints of improving image reproducibility and, in the case of a photosensitive resin layer, suppressing foaming during development.

[0035] When the surfactant (B) has a cationic group, it is preferable that the relief-forming layer further contains a hydroxycarboxylic acid (C). The cationic group of the surfactant (B) and the carboxyl group of the hydroxycarboxylic acid (C) form an electrically neutralized stable compound by ionic bonding, so that the surfactant (B) is more stably held in the relief-forming layer. In addition, when a partially saponified polyvinyl alcohol is used as the resin (A), the hydroxycarboxylic acid (C) is held in the relief layer by hydrogen bonding between the hydroxyl group of the partially saponified polyvinyl alcohol and the hydroxyl group of the hydroxycarboxylic acid (C), so that the surfactant (B) is more stably held in the relief-forming layer. This action is the same in the relief of the printing plate described later, and the extraction of the surfactant (B) into the ink can be further suppressed, and the printing durability can be further improved.

[0036] Examples of the hydroxycarboxylic acid (C) include aliphatic hydroxycarboxylic acids such as lactic acid, citric acid, tartaric acid, malic acid, hydroxyacetic acid, 3-hydroxypropionic acid, 8-hydroxyoctanoic acid, 15-hydroxypentadecanoic acid, and 16-hydroxyhexadecanoic acid, and aromatic hydroxycarboxylic acids such as gallic acid, salicylic acid, 3-hydroxy-2-phenylpropanoic acid, benzilic acid, 4-hydroxybenzoic acid, and γ-resorcylic acid. , hyaluronic acid oligosaccharides such as hyaluronic acid tetrasaccharide, hyaluronic acid hexasaccharide, hyaluronic acid octasaccharide, hyaluronic acid decasaccharide, and hyaluronic acid dodecasaccharide; colominic acid oligosaccharides such as N-acetylneuraminic acid dimer α(2-8), N-acetylneuraminic acid trimer α(2-8), N-acetylneuraminic acid tetramer α(2-8), and N-acetylneuraminic acid pentamer α(2-8); monoglucosyl gallic acid, diglucosyl gallic acid, and the like. Two or more of these may be included. Among these, those having two or more hydroxyl groups per carboxyl group in the molecule are preferred, and when partially saponified polyvinyl alcohol is used as the resin (A), the hydroxyl carboxylic acid (C) is more strongly held in the relief layer due to multiple hydrogen bonds between the hydroxyl group of the partially saponified polyvinyl alcohol and the hydroxyl group of the hydroxyl carboxylic acid (C), so that the surfactant (B) is more stably held in the relief-forming layer. More preferably, it has 3 or more hydroxyl groups, and even more preferably, it has 6 or more hydroxyl groups. Examples of hydroxycarboxylic acids having 2 or more hydroxyl groups per carboxy group in the molecule include γ-resorcylic acid, monoglucosyl gallic acid, citric acid, gallic acid, hyaluronic acid oligosaccharide, colominic acid oligosaccharide, and diglucosyl gallic acid. Among these, diglucosyl gallic acid having 6 or more hydroxyl groups per carboxy group in the molecule is more preferred.

[0037] The content of hydroxycarboxylic acid (C) in the relief-forming layer is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 1.0% by weight or more, based on the solid content, from the viewpoint of further suppressing adhesion of dust, dirt, paper powder, etc., which cause printing defects due to foreign matter, to the relief and further improving printing durability. On the other hand, the content of hydroxycarboxylic acid (C) is preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less, based on the solid content, from the viewpoint of improving image reproducibility.

[0038] When the relief-forming layer is a photosensitive resin layer, the photosensitive resin layer preferably contains a photopolymerization initiator and a compound having an ethylenic double bond.

[0039] As the photopolymerization initiator, one having a function of generating radicals by self-decomposition or hydrogen abstraction due to light absorption is preferably used. For example, benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, diacetyls, etc. may be mentioned. Two or more of these may be contained. The content of the photopolymerization initiator in the photosensitive resin layer is preferably 0.5 to 10% by weight of the solid content.

[0040] The compound having an ethylenic double bond refers to a compound having an ethylenic double bond and a molecular weight of less than 10,000. The molecular weight of the compound having an ethylenic double bond is preferably 2,000 or less. Examples of the compound having an ethylenic double bond include (meth)acrylates described in International Publication No. 2017 / 038970, glycerol di(meth)acrylate, (meth)acrylic acid adduct of propylene glycol diglycidyl ether, and tetrahydrofurfuryl (meth)acrylate. Two or more of these may be contained. Here, (meth)acrylate is a general term for acrylate and methacrylate, and (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0041] The content of the compound having an ethylenic double bond in the photosensitive resin layer is preferably 1 to 30% by weight based on the solid content.

[0042] The relief-forming layer may further contain, as necessary, a plasticizer or rubber particles for imparting flexibility, a polymerization inhibitor, a dye, a pigment, a defoaming agent, an ultraviolet absorbing agent, a fragrance, and the like.

[0043] The thickness of the relief-forming layer is preferably 0.3 mm or more, and in the printing plate described later, it is possible to provide sufficient relief depth and improve printability. The thickness of the relief-forming layer is more preferably 0.5 mm or more. On the other hand, the thickness of the relief-forming layer is preferably 5 mm or less, and in the case of a photosensitive resin layer, it is possible to allow the active light during exposure to reach the bottom sufficiently, thereby improving image reproducibility. The thickness of the relief-forming layer is more preferably 3 mm or less.

[0044] The printing plate precursor according to the present invention preferably has a cover film on the relief forming layer, which can protect the surface of the relief forming layer and further suppress adhesion of foreign matter, etc. The relief forming layer may be in contact with the cover film, or one or more layers may be present between the relief forming layer and the cover film. Examples of layers between the relief forming layer and the cover film include an anti-adhesion layer that prevents adhesion of the surface of the relief forming layer.

[0045] As the cover film, for example, a plastic sheet such as polyester or polyethylene is preferably used. The thickness of the cover film is preferably 10 to 150 μm. The surface of the cover film may be roughened to improve the adhesion of the original film.

[0046] When the printing plate precursor according to the present invention has a relief-forming layer that is a photosensitive resin layer, the printing plate precursor may further have a heat-sensitive mask layer on the photosensitive resin layer. The heat-sensitive mask layer is preferably one that blocks ultraviolet light, absorbs infrared laser light during drawing, and is instantly sublimated or ablated in whole or in part by the heat. This creates a difference in optical density between the laser-irradiated and non-irradiated areas, allowing the printing plate precursor to function in the same way as a conventional original film.

[0047] In addition, an adhesive strength adjusting layer may be provided between the heat-sensitive mask layer and the photosensitive resin layer to improve the adhesion between the heat-sensitive mask layer and the photosensitive resin layer, and a peeling auxiliary layer may be provided between the heat-sensitive mask layer and the cover film to suppress cohesive failure of the heat-sensitive mask layer when the cover film is peeled off.

[0048] Next, the method for producing a printing plate precursor according to the present invention will be described taking as an example a case in which the printing plate precursor has a primer layer, an adhesive layer and a photosensitive resin layer.

[0049] First, the components forming the primer layer, such as resin and isocyanate compound, and the solvent are thoroughly mixed by stirring to prepare a primer layer composition solution. Examples of the solvent include toluene and ethyl acetate. Two or more of these may be used. The obtained primer layer composition solution is cast onto a support and thermally cured to form a primer layer.

[0050] Next, an adhesive layer is formed on the primer layer. For example, the adhesive layer can be formed by casting an adhesive layer composition solution on the primer layer and drying it. The adhesive layer composition solution can be obtained by, for example, dissolving a water-swellable or water-soluble polymer in a water / alcohol mixed solvent by heating, adding a compound having an ethylenic double bond, a photopolymerization initiator, and additives as necessary, and stirring to thoroughly mix the mixture.

[0051] When the adhesive layer contains a compound having an ethylenic double bond and a photopolymerization initiator, the dried adhesive layer may be irradiated with active energy rays such as ultraviolet rays. The active energy rays to be irradiated are preferably ultraviolet rays, and examples of light sources used for ultraviolet irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, and chemical lamps.

[0052] Next, a photosensitive resin layer is formed on the adhesive layer. Examples of the method for forming the photosensitive resin layer include a method of casting and drying a photosensitive resin layer composition solution, and a method of laminating a separately formed photosensitive resin layer sheet to a support on which a primer layer and an adhesive layer are formed. The photosensitive resin layer composition solution can be obtained, for example, by heating and dissolving the resin (A) in a water / alcohol mixed solvent, adding a surfactant (B) and, if necessary, a hydroxycarboxylic acid (C), a compound having an ethylenic double bond, a photopolymerization initiator, a plasticizer, and other additives, and stirring to thoroughly mix the mixture.

[0053] Next, the flexographic printing plate according to the present invention will be described. The flexographic printing plate according to the present invention preferably has a relief layer containing the above-mentioned resin (A) and surfactant (B) on a support. The combination of resin (A) and surfactant (B) can suppress print defects caused by foreign matter even in long-run printing, and improve print durability. Furthermore, it is preferable that the plate contains the above-mentioned hydroxycarboxylic acid (C), which makes it easier to retain the surfactant (B) in the relief-forming layer, thereby further improving print durability.

[0054] Next, a method for producing a flexographic printing plate according to the present invention will be described. The flexographic printing plate according to the present invention has a step of forming a relief by partially removing the relief-forming layer of the flexographic printing plate precursor according to the present invention (relief-forming step). Examples of the relief-forming step include a method of engraving the relief-forming layer into a desired shape by electromagnetic energy rays such as laser light, and when the relief-forming layer is a photosensitive resin layer, a method having an exposure step of partially photocuring the photosensitive resin layer and a development step of removing the uncured portion of the photosensitive resin layer with a developer. Among these, a method having an exposure step and a development step using a photosensitive resin layer as the relief-forming layer is preferred from the viewpoints of productivity and image reproducibility of the printing plate.

[0055] First, the exposure step will be described. In the case where the printing plate precursor has a heat-sensitive mask layer, that is, a so-called CTP plate, the cover film is peeled off if it has one, and an image corresponding to the original film is drawn using a laser drawing machine, and then the photosensitive resin layer is photocured by irradiating it with ultraviolet light. In the case where the printing plate precursor does not have a heat-sensitive mask layer, the photosensitive resin layer is photocured by irradiating it with ultraviolet light through the original film. As the ultraviolet light, light with a wavelength of 300 to 400 nm is preferable, and examples of lamps used for ultraviolet light irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, and chemical lamps. In particular, when reproducibility of fine thin lines and independent points is required, it is also possible to form a floor layer by short-time exposure (back exposure) from the support side before peeling off the cover film.

[0056] Next, the developing step will be described. The exposed printing plate precursor is immersed in a developer, and the uncured portion of the photosensitive resin layer is removed by the developer using a brush-type developer or a spray-type developer, thereby forming a relief image on the substrate. The developer preferably contains water, and may contain additives such as a surfactant, if necessary. The developer temperature during development is preferably 15 to 40°C.

[0057] After development, it is preferable to dry the film for about 10 minutes at 50 to 70° C. If necessary, post-exposure may be performed by irradiating the film with actinic rays in the atmosphere or in a vacuum.

[0058] Next, a method for producing a printed matter of the present invention will be described. The method for producing a printed matter of the present invention includes a step of adhering ink to the relief of the flexographic printing plate obtained by the above-mentioned method, and a step of transferring the ink to a printing medium. Examples of flexographic printing machines include in-line type, center drum type, and stack type.

[0059] The ink is preferably an ultraviolet curable ink or an electron beam curable ink. The ultraviolet curable ink is preferably one containing, for example, a pigment, a resin such as an acrylic oligomer, an acrylate monomer, a polymerization initiator, etc., and more specifically, for example, commercially available flexographic printing inks such as PHA (manufactured by T&K TOKA Co., Ltd.), "FLASH DRY" (registered trademark) (manufactured by Toyo Ink Co., Ltd.), and "UVAFLEX" (registered trademark) Y77 (manufactured by Zeller+Gmelin). The electron beam curable ink is preferably one containing, for example, a pigment, a resin such as an acrylic oligomer, an acrylate monomer, etc., and more specifically, for example, flexographic printing inks such as "GelFlex EB" (registered trademark) (manufactured by SAKATA INX). EXAMPLES

[0060] The materials used in each of the examples and comparative examples are shown below.

[0061] (Resin having ionic groups (A)) (Synthesis Example 1: Synthesis of Resin 1) "GOHSENOL" (registered trademark) KL-05 (partially saponified polyvinyl alcohol with a degree of saponification of 78.5 to 82.0 mol%, weight average molecular weight of 38,000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was swollen in acetone, and 1.0 mol% of succinic anhydride was added and stirred at 60°C for 6 hours to add a carboxy group to the molecular chain. This polymer was washed with acetone to remove unreacted succinic anhydride and dried to obtain Resin 1 having a carboxy group as an ionic group. The acid value was measured to be 10.0 mgKOH / g.

[0062] (Surfactant (B)) · TMO (cationic surfactant, octyltrimethylammonium chloride, manufactured by Tokyo Chemical Industry Co., Ltd.) "Kachiogen" (registered trademark) TML (cationic surfactant, 30% by weight aqueous solution of lauryl trimethyl ammonium chloride, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) "Kachiogen" (registered trademark) TMP (cationic surfactant, 30% by weight aqueous solution of cetyltrimethylammonium chloride, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) "Kachiogen" (registered trademark) TMS (cationic surfactant, 25% by weight aqueous solution of stearyl trimethyl ammonium chloride, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) "Nissan Cation" (registered trademark) VB-F (cationic surfactant, 80% by weight ethanol solution of behenyl trimethyl ammonium chloride, manufactured by NOF Corporation) (Hydroxycarboxylic acid (C)) Citric acid (Tokyo Chemical Industry Co., Ltd.) DGA (diglucosyl gallic acid, Mitsui Chemicals Fine Co., Ltd.) The evaluation methods used in each of the Examples and Comparative Examples are shown below.

[0063] (1) Image reproducibility For the printing plate precursors obtained in Examples 1 to 14 and Comparative Example 1, the protective layer of the cover film was peeled off, and the plates were attached to an external drum-type platesetter CDI SPARK (manufactured by Esko Graphics Co., Ltd.) equipped with a fiber laser having an infrared light emission region, with the support side in contact with the drum, and a test pattern (having 150 lines, 4% dots and a 10 cm x 10 cm solid area) was drawn to form an image mask on the thermal mask layer.

[0064] Next, a batch-type exposure and development machine, Tomiflex (manufactured by Tomihaku Sangyo Co., Ltd.), was used to develop the film with an integrated light dose of 16,000 mJ / cm. 2 After exposure to light of about 1000 mJ / cm2, the film was developed for 60 seconds using tap water adjusted to 25°C as the developer. The film was then dried in an oven at 60°C for 10 minutes. 2 After that, a flexographic printing plate was obtained.

[0065] The cover film was peeled off from the printing plate precursor obtained in Example 15, and a test pattern (having 150 lines, 4% dots and a 10 cm x 10 cm solid area) was laser engraved using a direct laser engraving system Adflex Direct 250L (manufactured by Comtex Co., Ltd.). Next, the plate was rinsed with tap water at 25°C for 1.5 minutes using a platemaking device DX-A3 (manufactured by Takano Co., Ltd.), and then dried in a hot air dryer at 60°C for 10 minutes to obtain a flexographic printing plate.

[0066] The resulting flexographic printing plate was inspected for chipping using a 10x magnifying glass to check for the presence or absence of chipping in the 150 line 4% dots formed in an area of ​​1cm x 1cm. Image reproducibility was evaluated according to the following criteria, with a score of 4 or higher being considered a pass. 5: No chipping observed 4: Missing dots are found in the outermost area 3: Chips are found in the outermost area and the area two rows from the outermost area. 2: Chips are found in the inner area including the third row from the outermost circumference. 1: Missing areas are found in 20% or more of the total halftone dot area.

[0067] (2) Printing durability The flexographic printing plate obtained by the method (1) above was attached to a flexographic printing machine (MPS EF340) equipped with a 991LPI anilox roll. Using UV Flexo Red PHA-LO3 / T&K TOKA, which is an ultraviolet-curing ink, the solid density was adjusted to 1.65, and 20,000 m was printed on mirror-coated paper (Oji Tack N Mirror 73 / P22 / G7B, Oji Paper Co., Ltd.) at a speed of 60 m / min. The number of print defects in a 10 cm x 10 cm solid area was observed using a 10x magnifying glass for the prints at 5,000 m, 10,000 m, and 20,000 m. Print defects were evaluated according to the following criteria, and a score of 4 or more at the time of printing 5,000 m was considered to be acceptable. 5: Fewer than 5 missing prints 4: The number of printing defects is between 5 and 10. 3: The number of printing defects is between 10 and 15. 2: The number of printing defects is between 15 and 20. 1: There are 20 or more printing defects.

[0068] Example 1 [Preparation of a support having a primer layer and an adhesive layer] A mixture of 260 parts by weight of "Vylon" (registered trademark) 31SS (toluene solution of saturated polyester resin, manufactured by Toyobo Co., Ltd.) and 2 parts by weight of PS-8A (benzoin ethyl ether, manufactured by Wako Pure Chemical Industries, Ltd.) was heated at 70°C for 2 hours, cooled to 30°C, and 7 parts by weight of ethylene glycol diglycidyl ether dimethacrylate was added and mixed for 2 hours. Furthermore, 25 parts by weight of "Coronate" (registered trademark) 3015E (ethyl acetate solution of polyisocyanate resin, manufactured by Tosoh Co., Ltd.) and 14 parts by weight of EC-1368 (industrial adhesive, manufactured by Sumitomo 3M Co., Ltd.) were added and mixed to obtain a primer layer composition solution.

[0069] The primer layer composition solution was applied using a bar coater onto a 188 μm-thick "Lumirror" (registered trademark) T60 (polyester film, manufactured by Toray Industries, Inc.) so that the thickness after drying would be 40 μm. The solution was then heated in an oven at 180° C. for 3 minutes to remove the solvent, forming a primer layer.

[0070] 50 parts by weight of "GOHSENOL" (registered trademark) KH-17 (partially saponified polyvinyl alcohol with a saponification degree of 78.5 to 81.5 mol%, weight average molecular weight 165,000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) were mixed in a mixed solvent of 200 parts by weight of "SOLMIX" (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) and 200 parts by weight of water at 70°C for 2 hours, and then 1.5 parts by weight of "BLEMMER" (registered trademark) G (glycidyl methacrylate, manufactured by NOF Corporation) was added and mixed for 1 hour. A mixture of 3 parts by weight of "Irgacure" (registered trademark) 651 (benzyl methyl ketal, manufactured by BASF), 21 parts by weight of Epoxy Ester 70PA (acrylic acid adduct of propylene glycol diglycidyl ether, manufactured by Kyoeisha Chemical Co., Ltd.) and 20 parts by weight of ethylene glycol diglycidyl ether dimethacrylate was added and mixed for 90 minutes. The mixture was then cooled to 50°C, after which 0.1 parts by weight of "Megafac" (registered trademark) F-556 (manufactured by DIC Corporation) was added and mixed for 30 minutes to obtain an adhesive layer composition solution.

[0071] The adhesive layer composition solution was applied onto the primer layer using a bar coater so that the thickness after drying would be 30 μm, and the solution was heated in an oven at 160° C. for 3 minutes to remove the solvent, thereby forming an adhesive layer.

[0072] After that, an ultra-high pressure mercury lamp (JP2000T, Oak Manufacturing Co., Ltd.) was used from the adhesive layer side to illuminate the adhesive layer with a cumulative light intensity of 1,000 mJ / cm. 2 The above exposure treatment was carried out to obtain a support composed of an adhesive layer / primer layer / PET film.

[0073] [Formation of photosensitive resin layer] Into a three-neck flask equipped with a stirring spatula and a cooling tube, 40 parts by weight of Resin 1 obtained in Synthesis Example 1, 30 parts by weight of trimethylolpropane (weight average molecular weight: 134) as a plasticizer, 40 parts by weight of an alcohol mixture ("Solmix" (registered trademark) H-11, manufactured by Japan Alcohol Co., Ltd.) as a solvent, and 60 parts by weight of distilled water were placed, and the mixture was heated at 77°C for 2 hours with stirring to dissolve Resin 1 and the plasticizer.

[0074] After the melt was cooled to 70° C., 5 parts by weight of glycidyl methacrylate was added and stirred for 1 hour.

[0075] Next, 11 parts by weight of polyethylene glycol monomethacrylate ("Blenmer" (registered trademark) AE400, manufactured by NOF Corporation) and 10 parts by weight of polyethylene glycol dimethacrylate ("Blenmer" (registered trademark) AD400, manufactured by NOF Corporation) as compounds having an ethylenic double bond, 2 parts by weight of benzyl dimethyl ketal as a photopolymerization initiator, and 8 parts by weight of TMS as a surfactant (B) were added and stirred for 60 minutes to obtain a photosensitive resin layer composition solution.

[0076] The obtained photosensitive resin layer composition solution was cast onto the primer layer of the support, with the plate thickness (support + photosensitive resin layer) adjusted to 1.14 mm after drying, and dried at 60° C. for 2.5 hours to form a photosensitive resin layer on the support. Here, the content of the surfactant having a structure represented by general formula (1), which is the solid content of the surfactant (B) in the photosensitive resin layer, was 2.0% by weight.

[0077] [Cover film production for CTP plates] Eleven parts by weight of "GOHSENOL" (registered trademark) KL-05 (partially saponified polyvinyl alcohol with a saponification degree of 78.5 mol% to 82.0 mol%, weight average molecular weight of 38,000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) were dissolved in 55 parts by weight of water, 14 parts by weight of methanol, 10 parts by weight of n-propanol, and 10 parts by weight of n-butanol to obtain a peeling auxiliary layer composition solution.

[0078] A carbon black dispersion was prepared by kneading and dispersing a mixture of 23 parts by weight of carbon black MA100 (manufactured by Mitsubishi Chemical Corporation), 15 parts by weight of "DIANAL" (registered trademark) BR-95 (an alcohol-insoluble acrylic resin, manufactured by Mitsubishi Rayon Co., Ltd.), 1 part by weight of plasticizer ATBC (acetyl tributyl citrate, manufactured by J-Plus Corporation) and 30 parts by weight of methyl isobutyl ketone in advance using a three-roll mill.

[0079] To the carbon black dispersion, 1 part by weight of AER6071 (epoxy resin, manufactured by Asahi Kasei Chemicals Corporation), 1 part by weight of "U-Ban" (registered trademark) 20SE60 (melamine resin, manufactured by Mitsui Chemicals, Inc.), 0.05 part by weight of Light Ester P-1M (phosphate monomer, manufactured by Kyoeisha Chemical Co., Ltd.), and 100 parts by weight of methyl isobutyl ketone were added and stirred for 30 minutes to obtain a heat-sensitive mask layer composition solution.

[0080] "GOHSENOL" (registered trademark) AL-06 (partially saponified polyvinyl alcohol with a saponification degree of 91 to 94 mol%, weight average molecular weight of 46,500, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was dissolved in a mixed solvent of water:ethanol = 50:50 (weight ratio) to obtain an adhesion adjusting layer composition solution.

[0081] The peeling auxiliary layer composition solution was applied using a bar coater onto a 100 μm thick polyester film "Lumilar" (registered trademark) S10 (manufactured by Toray Industries, Inc.) so that the thickness after drying would be 0.1 μm, and the coating was dried at 120° C. for 20 seconds to form a peeling auxiliary layer.

[0082] Next, the heat-sensitive mask layer composition solution was applied onto the peeling auxiliary layer using a bar coater so as to give a dried thickness of 1.0 μm, and dried at 140° C. for 20 seconds to form a heat-sensitive mask layer.

[0083] Further, the adhesive strength adjusting layer composition solution was applied onto the heat-sensitive mask layer using a bar coater so that the thickness after drying would be 1.0 μm, and the solution was dried for 20 seconds at 120° C. to form an adhesive strength adjusting layer. In this way, a cover film for a CTP plate, which is a laminate of an adhesive strength adjusting layer / heat-sensitive mask layer / peeling auxiliary layer / protective layer, was obtained.

[0084] [Preparation of printing plate precursor] A mixed solvent of water / ethanol = 50 / 50 (weight ratio) was applied onto the photosensitive resin layer obtained by the above-mentioned method, and the cover film for the CTP plate obtained by the above-mentioned method was pressed onto the photosensitive resin layer with the adhesion adjustment layer facing the photosensitive resin layer, thereby obtaining a printing plate precursor.

[0085] The obtained printing plate precursor was evaluated for image reproducibility and printing durability by the above-mentioned methods, and the results are shown in Table 1.

[0086] Example 2 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 6.7 parts by weight of TML was used as surfactant (B) instead of 8 parts by weight of TMS. The content of the surfactant having the structure represented by general formula (1), which is the solid content of surfactant (B) in the photosensitive resin layer, was 2.0% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0087] Example 3 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 6.7 parts by weight of TMP was used as surfactant (B) instead of 8 parts by weight of TMS. The content of the surfactant having the structure represented by general formula (1), which is the solid content of surfactant (B) in the photosensitive resin layer, was 2.0% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0088] Example 4 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 2.5 parts by weight of VB-F was used as the surfactant (B) instead of 8 parts by weight of TMS. The content of the surfactant having the structure represented by general formula (1), which is the solid content of the surfactant (B) in the photosensitive resin layer, was 2.0% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0089] Example 5 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 0.4 parts by weight of TMS was used as surfactant (B) instead of 8 parts by weight of TMS. The content of the surfactant having the structure represented by general formula (1), which is the solid content of surfactant (B) in the photosensitive resin layer, was 0.1% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0090] Example 6 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 20.7 parts by weight of TMS was used as surfactant (B) instead of 8 parts by weight of TMS. The content of the surfactant having the structure represented by general formula (1), which is the solid content of surfactant (B) in the photosensitive resin layer, was 5.0% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0091] Comparative Example 1 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 2.0 parts by weight of TMO was used as the surfactant (B) instead of 8 parts by weight of TMS. The solid content of the surfactant in the photosensitive resin layer was 2.0% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0092] (Examples 7 to 11) A printing plate precursor was obtained in the same manner as in Examples 1 to 5, except that 1.5 parts by weight of DGA was further added as the hydroxycarboxylic acid (C) in [Formation of the photosensitive resin layer]. The content of DGA in the photosensitive resin layer was 1.5% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 2.

[0093] Example 12 A printing plate precursor was obtained in the same manner as in Example 6, except that 1.6 parts by weight of DGA was further added as the hydroxycarboxylic acid (C) in [Formation of the photosensitive resin layer]. The content of DGA in the photosensitive resin layer was 1.5% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 2.

[0094] Example 13 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 1.5 parts by weight of citric acid was further added as the hydroxycarboxylic acid (C). The content of citric acid in the photosensitive resin layer was 1.5% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 2.

[0095] Example 14 A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of photosensitive resin layer], 5.3 parts by weight of DGA was further added as hydroxycarboxylic acid (C). The content of the surfactant having the structure represented by general formula (1) in the photosensitive resin layer was 1.9% by weight, and the content of DGA in the photosensitive resin layer was 5.0% by weight. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 2.

[0096] Example 15 [Preparation of a support having a primer layer and an adhesive layer] and [Formation of a photosensitive resin layer] were carried out in the same manner as in Example 8. A mixed solvent of water / ethanol = 50 / 50 (weight ratio) was applied onto the photosensitive resin layer, and a polyester film "Lumirror" (registered trademark) S10 (manufactured by Toray Industries, Inc.) having a thickness of 100 μm was pressed as a cover film. Next, a high-intensity chemical lamp (TL-K 40W / 10R manufactured by Philips) was used to irradiate the substrate with an integrated light quantity of 12,000 mJ / cm2 from each of the support side and the cover film side. 2 The obtained printing plate precursor was evaluated for image reproducibility and printing durability by the above-mentioned methods, and the results are shown in Table 2.

[0097] [Table 1]

[0098] [Table 2]

Claims

1. A flexographic printing plate precursor having a relief-forming layer containing a resin (A) having an ionic group and a surfactant (B) having a hydrocarbon group having 10 or more carbon atoms and an ionic group capable of forming a counter ion with the resin (A).

2. The flexographic printing plate precursor according to claim 1 , which has a carboxy group and / or a carboxylate as the ionic group.

3. The flexographic printing plate precursor according to claim 1 or 2, wherein the surfactant (B) has a structure represented by the following general formula (1): 【Chemistry 1】 (In the above general formula (1), R1 represents an alkyl group or an alkenyl group having 10 or more carbon atoms. R2 represents a hydrogen atom, an alkyl group having 1 to 28 carbon atoms, or a benzyl group. R3 and R4 may be the same or different and represent an alkyl group having 1 to 5 carbon atoms. An － indicates a monovalent anion.)

4. The flexographic printing plate precursor according to claim 1 or 2, wherein the relief-forming layer further contains a hydroxycarboxylic acid (C).

5. The flexographic printing plate precursor according to claim 4 , comprising diglucosyl gallic acid as the hydroxycarboxylic acid (C).

6. A method for producing a flexographic printing plate, comprising a step of partially removing the relief-forming layer of the flexographic printing plate precursor according to claim 1 or 2 to form a relief.

7. A flexographic printing plate having a relief layer containing a resin (A) having an ionic group and a surfactant (B) having a hydrocarbon group having 10 or more carbon atoms and an ionic group capable of forming a counter ion with the resin (A).

8. A method for producing a printed matter, comprising the steps of: depositing ink on the relief of the flexographic printing plate according to claim 7; and transferring the ink to a printing substrate.

9. The method for producing a printed matter according to claim 8, wherein the ink is an ultraviolet-curable ink and / or an electron beam-curable ink.

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