JP2025000091A - Flexographic printing plate precursor, flexographic printing plate and method for producing printed material using the same - Google Patents

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

The present invention relates to a flexographic printing plate precursor, a flexographic printing plate and its manufacturing method, and a method for manufacturing a printed matter using the same.

Taking advantage of its flexibility, flexographic printing is widely used in applications such as paper containers, labels, and soft packaging, as well as 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 will not adhere to the areas around the foreign matter, and the ink will not be transferred to the substrate, resulting in a printing defect known as a print defect.

As a result, as a technique for reducing adhesion of foreign matter such as dust, dirt, and paper powder to the relief, for example, a water-developable photosensitive resin composition for flexographic printing containing 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 (d) the 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 (d) the fatty acid in the photosensitive resin composition is 0.5 to 8.0% by weight, a photosensitive resin layer composed of the water-developable photosensitive resin composition for flexographic printing, a support, and an adhesive layer for adhering them (see, for example, Patent Document 1) have been proposed.

WO 2016/43006

However, the photosensitive resin original plate for flexographic printing disclosed in Patent Document 1 has the problem that fatty acids in the photosensitive resin layer are easily extracted into the ink during the printing process, and when used for long-run printing or repeatedly, the flexographic printing plate is prone to adhesion of foreign matter, resulting in printing defects caused by the foreign matter.

In view of the above problems, the present invention aims to provide a flexographic printing plate precursor that can produce a flexographic printing plate with excellent printing durability and that is less susceptible to print defects caused by foreign matter even in long-run printing.

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 flexographic printing plate precursor according to <1>, wherein the ionic group is a carboxy group and/or a carboxylate.
<3> The flexographic printing plate precursor according to <1> or <2>, wherein the surfactant (B) has a structure represented by the following general formula (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 -} represents a monovalent anion.)
<4> The flexographic printing plate precursor according to any one of <1> to <3>, wherein the relief forming layer further contains a hydroxycarboxylic acid (C).
<5> The flexographic printing plate precursor according to <4>, wherein the hydroxycarboxylic acid (C) is diglucosyl gallic acid.
<6> A method for producing a flexographic printing plate, comprising a step of partially removing a relief-forming layer of the flexographic printing plate precursor according to any one of <1> to <5> 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 <7>; and transferring the ink to a substrate.
<9> The method for producing a printed matter according to <8>, wherein the ink is an ultraviolet-curable ink and/or an electron beam-curable ink.

The flexographic printing plate precursor of the present invention makes it possible to obtain a flexographic printing plate with excellent printing durability and with less chance of print defects due to foreign matter even in long-run printing.

The flexographic printing plate precursor (hereinafter sometimes referred to as "printing plate precursor") according to the present invention is a precursor of a flexographic printing plate (hereinafter sometimes 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.

The support serves to support the relief-forming layer.
The support is preferably made of a material having flexibility and excellent dimensional stability. Specific examples include a plastic sheet such as polyester, and a metal plate such as steel, stainless steel, and aluminum. Two or more of these may be used.

From the standpoint of ease of handling and flexibility, the thickness of the support is preferably in the range of 100 to 350 μm.

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 upon 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 of the printing plate and image reproducibility.

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 a hydrocarbon group having 10 or more carbon atoms and the resin (A) (hereinafter, sometimes referred to as "surfactant (B)"). The surfactant (B) has the effect of suppressing the adhesion of dust, dirt, paper powder, etc., which cause print defects due to foreign matter, to the relief in the printing plate described later. The resin (A) acts as a binder resin that maintains the shape of the relief-forming layer, and 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 the 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 even in long-run printing in the printing plate, and improve print durability. In addition, it is preferable to contain a hydroxycarboxylic acid (C), which makes it easier to retain the surfactant (B) in the relief-forming layer, thereby further improving the printing durability of the printing plate.

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 impact can be reduced. A water-swellable or water-soluble resin refers to a polymer having a hydrophilic group, and examples of the hydrophilic group include a hydroxyl group, an amino group, an amide group, a carboxyl group, a phosphate group, and an ethylene glycol skeleton. 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 viewpoints of water solubility and processability.

From the viewpoint of water developability, the degree of saponification of the partially saponified polyvinyl alcohol is preferably 60 mol% or more and 90 mol% or less. Here, the degree of saponification can be calculated by subjecting a partially saponified polyvinyl alcohol aqueous solution having a concentration of 3% by mass 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.

Because partially saponified polyvinyl alcohol has hydroxyl groups, when printing on paper containing cellulose fibers as the main component as the 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).

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

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

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.

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

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 can suppress the extraction of the surfactant (B) into the ink. Here, the surfactant (B) has a hydrocarbon group having 10 or more carbon atoms, and can suppress interactions with, for example, hydroxyl groups of cellulose fibers in paper powder. This suppresses the adhesion of the relief to the printing plate, and suppresses adhesion of dust, dirt, paper powder, and other particles that cause print omissions due to foreign matter to the relief, thereby suppressing print omissions due to foreign matter even in long-run printing, and improving print durability.

Examples of the ionic group in the surfactant (B) include the anionic groups and cationic groups exemplified above as the ionic groups in the resin (A). 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.

Examples of the hydrocarbon group having 10 or more carbon atoms in the surfactant (B) include an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an aryl group, and an arylalkyl group. Some of these hydrogen atoms may be substituted, and examples of the substituent include a nitro group, a thiol group, and an amino group. From the viewpoint of suppressing adhesion of dust, dirt, paper powder, etc., which cause print omissions due to foreign matter, to the relief, suppressing print omissions due to foreign matter even in long-run printing, and improving print durability, the number of carbon atoms in 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 number of carbon atoms in the hydrocarbon group is preferably 24 or less.

Examples of the surfactant (B) include cationic surfactants such as 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.

The surfactant (B) preferably has a structure represented by the following general formula (1):

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

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

R3 and R4 may be the same or different and represent 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.

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.

As the surfactant (B) having the structure represented by the general formula (1), for example, mono-long chain alkyl quaternary ammonium salts (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) are preferred, and specific examples 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 preferred.

The solid content of 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, in order to further suppress adhesion of dust, dirt, paper powder, and the like, which are the cause of print defects due to foreign matter, to the relief and to further improve print durability. On the other hand, the solid content of 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, in order to improve image reproducibility and, in the case of a photosensitive resin layer, to suppress foaming during development.

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 also 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.

Examples of hydroxycarboxylic acids (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 groups of the partially saponified polyvinyl alcohol and the hydroxyl groups of the hydroxyl carboxylic acid (C), and therefore the surfactant (B) is more stably held in the relief-forming layer. Those having three or more hydroxyl groups are more preferred, and those having six or more hydroxyl groups are even more preferred. Examples of hydroxycarboxylic acids having two or more hydroxyl groups per carboxy group in the molecule include γ-resorcylic acid, monoglucosyl gallic acid, citric acid, gallic acid, hyaluronic acid oligosaccharides, colominic acid oligosaccharides, and diglucosyl gallic acid. Among these, diglucosyl gallic acid, which has six or more hydroxyl groups per carboxy group in the molecule, is more preferred.

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 are the cause of 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.

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.

As the photopolymerization initiator, one that has the function of generating radicals by self-decomposition or hydrogen abstraction upon light absorption is preferably used. Examples include benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, and diacetyls. 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.

A 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 compounds 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.

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

The relief-forming layer may further contain, as necessary, plasticizers or rubber particles to impart flexibility, polymerization inhibitors, dyes, pigments, defoamers, ultraviolet absorbers, fragrances, etc.

The thickness of the relief-forming layer is preferably 0.3 mm or more, and in the printing plate described below, 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.

The printing plate precursor according to the present invention preferably has a cover film on the relief-forming layer, which protects the surface of the relief-forming layer and further suppresses adhesion of foreign matter and the like. 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.

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.

When the printing plate precursor according to the present invention has a relief-forming layer that is a photosensitive resin layer, it 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 it to function in the same way as a conventional original film.

Furthermore, an adhesive strength adjustment layer may be provided between the heat-sensitive mask layer and the photosensitive resin layer, which can improve adhesion between the heat-sensitive mask layer and the photosensitive resin layer. Also, a peeling auxiliary layer may be provided between the heat-sensitive mask layer and the cover film, which can suppress cohesive failure of the heat-sensitive mask layer when the cover film is peeled off.

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

First, the components that form the primer layer, such as a resin and an isocyanate compound, and a 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 resulting primer layer composition solution is cast onto a support and thermally cured to form a primer layer.

Next, an adhesive layer is formed on the primer layer. Examples of methods for forming the adhesive layer include a method in which an adhesive layer composition solution is cast onto the primer layer and then dried. The adhesive layer composition solution can be obtained, for example, by dissolving a water-swellable or water-soluble polymer in a water/alcohol mixed solvent with heating, adding a compound having an ethylenic double bond, a photopolymerization initiator, and additives as necessary, and stirring to thoroughly mix.

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 light. The active energy rays to be irradiated are preferably ultraviolet light, and examples of light sources 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.

Next, a photosensitive resin layer is formed on the adhesive layer. Examples of methods for forming the photosensitive resin layer include a method of casting a photosensitive resin layer composition solution and drying it, 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.

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 on a support, the relief layer containing the aforementioned resin (A) and surfactant (B). 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 for the plate to contain the aforementioned hydroxycarboxylic acid (C), which makes it easier to retain the surfactant (B) in the relief-forming layer, thereby further improving print durability.

Next, a method for producing a flexographic printing plate according to the present invention will be described. The flexographic printing plate of 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 using 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 parts 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 of the printing plate and image reproducibility.

First, the exposure process will be described. In the case of a so-called CTP plate having a heat-sensitive mask layer, if the printing plate precursor has a cover film, it is peeled off, 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 of a printing plate precursor not having 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 irradiating ultraviolet light 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.

Next, the development process will be described. The exposed printing plate precursor is immersed in a developer, and the uncured parts of the photosensitive resin layer are removed with the developer using a brush-type or spray-type developer, thereby forming a relief image on the substrate. The developer preferably contains water, and may contain additives such as surfactants as necessary. The developer temperature during development is preferably 15 to 40°C.

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

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 applying ink to the relief of the flexographic printing plate obtained by the above-mentioned method, and a step of transferring the ink to a substrate. Examples of flexographic printing machines include in-line type, center drum type, and stack type.

As the ink, ultraviolet curing ink and electron beam curing ink are preferred. As the ultraviolet curing ink, for example, those containing a pigment, a resin such as an acrylic oligomer, an acrylate monomer, a polymerization initiator, etc. are preferred, 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) are included. As the electron beam curing ink, for example, those containing a pigment, a resin such as an acrylic oligomer, an acrylate monomer, etc. are preferred, and more specifically, for example, flexographic printing inks such as "GelFlex EB" (registered trademark) (manufactured by SAKATA INX) are included.

The materials used in each example and comparative example are listed below.

(Resin (A) having ionic groups)
(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 then dried to obtain Resin 1 having a carboxy group as an ionic group. The acid value was measured to be 10.0 mgKOH/g.

(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, manufactured by Mitsui Chemicals Fine Co., Ltd.)
The evaluation methods used in each of the Examples and Comparative Examples are shown below.

(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 printing plate precursors 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, so that the support side was 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 heat-sensitive mask layer.

Next, using a batch-type exposure and development machine Tomiflex (manufactured by Tomihaku Sangyo Co., Ltd.), the plate was exposed to an accumulated light amount of about 16,000 mJ/ ^cm2 , and then developed for 60 seconds using tap water adjusted to 25°C as a developer. Thereafter, the plate was dried at 60°C for 10 minutes using an oven. Thereafter, exposure (post-exposure) was performed with an accumulated light amount of 16,000 mJ/ ^cm2 to obtain a flexographic printing plate.

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 for 1.5 minutes with tap water at 25°C using a platemaking device DX-A3 (manufactured by Takano Co., Ltd.), and then dried for 10 minutes in a hot air dryer at 60°C to obtain a flexographic printing plate.

The halftone dots of the obtained flexographic printing plate, 150 lines/4% halftone dots formed in an area of 1 cm x 1 cm, were observed for the presence or absence of chipping using a magnifying glass of 10 times magnification. Image reproducibility was evaluated according to the following criteria, with a score of 4 or more being considered as passing.
5: No missing dots are found; 4: Missing dots are found in the outermost area; 3: Missing dots are found in the outermost area and the area two rows from the outermost area; 2: Missing dots are found in the internal area including the third row from the outermost area; 1: Missing dots are found in 20% or more of the total dot area.

(2) Printing durability The flexographic printing plate obtained by the method (1) above was mounted on a flexographic printing machine (EF340 manufactured by MPS) equipped with a 991 LPI anilox roll. Using UV Flexographic 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 manufactured by 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: The number of printing holes is less than 5; 4: The number of printing holes is 5 or more but less than 10; 3: The number of printing holes is 10 or more but less than 15; 2: The number of printing holes is 15 or more but less than 20; 1: The number of printing holes is 20 or more.

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 Corporation) and 14 parts by weight of EC-1368 (industrial adhesive, manufactured by Sumitomo 3M Limited) were added and mixed to obtain a primer layer composition solution.

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, and the solution was heated in an oven at 180°C for 3 minutes to remove the solvent, forming a primer layer.

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, after which 1.5 parts by weight of "BLEMMER" (registered trademark) G (glycidyl methacrylate, manufactured by NOF Corporation) were added and mixed for 1 hour, and then dimethylaminoethyl methacrylate/2-hydroxyethyl methacrylate were added. 3 parts by weight of ethylene glycol diglycidyl ether copolymer (weight ratio 2/1) (Kyoeisha Chemical Co., Ltd.), 5 parts by weight of "Irgacure" (registered trademark) 651 (benzyl methyl ketal, BASF Corporation), 21 parts by weight of epoxy ester 70PA (acrylic acid adduct of propylene glycol diglycidyl ether, Kyoeisha Chemical Co., Ltd.), and 20 parts by weight of ethylene glycol diglycidyl ether dimethacrylate were added and mixed for 90 minutes, cooled to 50°C, and then 0.1 parts by weight of "Megafac" (registered trademark) F-556 (DIC Corporation) was added and mixed for 30 minutes to obtain an adhesive layer composition solution.

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, forming an adhesive layer.

Thereafter, exposure treatment was performed from the adhesive layer side using an ultra-high pressure mercury lamp (JP2000T, manufactured by Oak Manufacturing Co., Ltd.) with an integrated light quantity of 1,000 mJ/cm ² to obtain a support composed of the adhesive layer/primer layer/PET film.

[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.

After cooling the solution to 70°C, 5 parts by weight of glycidyl methacrylate was added and stirred for 1 hour.

Next, 11 parts by weight of polyethylene glycol monomethacrylate (NOF Corp., "Blenmer" (registered trademark) AE400) and 10 parts by weight of polyethylene glycol dimethacrylate (NOF Corp., "Blenmer" (registered trademark) AD400) 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.

The obtained photosensitive resin layer composition solution was cast onto the primer layer of the support, adjusting the plate thickness after drying (support + photosensitive resin layer) to 1.14 mm, 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.

[Preparation of cover film for CTP plate]
A peeling auxiliary layer composition solution was obtained by dissolving 11 parts by weight of "GOHSENOL" (registered trademark) KL-05 (partially saponified polyvinyl alcohol having 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.) 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.

23 parts by weight of carbon black MA100 (manufactured by Mitsubishi Chemical Corporation), 15 parts by weight of "DIANAL" (registered trademark) BR-95 (alcohol-insoluble acrylic resin, manufactured by Mitsubishi Rayon Co., Ltd.), 1 part by weight of plasticizer ATBC (acetyl tributyl citrate, manufactured by J-Plus Co., Ltd.), and 30 parts by weight of methyl isobutyl ketone were mixed in advance and kneaded and dispersed using a three-roll mill to prepare a 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 parts 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 to the carbon black dispersion and stirred for 30 minutes to obtain a heat-sensitive mask layer composition solution.

"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.

The peeling aid 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 aid layer.

Next, the heat-sensitive mask layer composition solution was applied onto the peeling aid layer using a bar coater so that the thickness after drying would be 1.0 μm, and then dried at 140°C for 20 seconds to form a heat-sensitive mask layer.

Furthermore, the adhesive strength adjustment 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 then dried at 120°C for 20 seconds to form an adhesive strength adjustment layer. In this way, a cover film for CTP plates, which is a laminate of adhesive strength adjustment layer/heat-sensitive mask layer/peeling auxiliary layer/protective layer, was obtained.

[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 a 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.

The image reproducibility and printing durability of the obtained printing plate precursor were evaluated using the methods described above, and the results are shown in Table 1.

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 a 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 methods, and the results are shown in Table 1.

Example 3
A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of the photosensitive resin layer], 6.7 parts by weight of TMP was used as the surfactant (B) instead of 8 parts by weight of TMS. 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. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned methods, and the results are shown in Table 1.

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 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. The image reproducibility and printing durability of the obtained printing plate precursor were evaluated by the above-mentioned methods, and the results are shown in Table 1.

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 a 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 methods, and the results are shown in Table 1.

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 a 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 methods, and the results are shown in Table 1.

(Comparative Example 1)
A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of the 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 methods, and the results are shown in Table 1.

(Examples 7 to 11)
A printing plate precursor was obtained in the same manner as in Examples 1 to 5, except that in [Formation of the photosensitive resin layer], 1.5 parts by weight of DGA was further added as the hydroxycarboxylic acid (C). 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 methods, and the results are shown in Table 2.

Example 12
A printing plate precursor was obtained in the same manner as in Example 6, except that in [Formation of the photosensitive resin layer], 1.6 parts by weight of DGA was further added as the hydroxycarboxylic acid (C). 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.

Example 13
A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of the 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 methods, and the results are shown in Table 2.

(Example 14)
A printing plate precursor was obtained in the same manner as in Example 1, except that in [Formation of the photosensitive resin layer], 5.3 parts by weight of DGA was further added as the hydroxycarboxylic acid (C). The content of the surfactant having a 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 methods, and the results are shown in Table 2.

(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, exposure was carried out from each of the support side and the cover film side using a high-intensity chemical lamp (TL-K 40W/10R manufactured by Philips) so that the accumulated light amount was about 12,000 mJ/ ^cm2 , respectively, to obtain a printing plate precursor. The obtained printing plate precursor was evaluated for image reproducibility and printing durability by the above-mentioned method, and the results are shown in Table 2.

Claims (9)

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). The flexographic printing plate precursor according to claim 1, wherein the ionic group is a carboxy group and/or a carboxylate salt. 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):

(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 -} represents a monovalent anion.) The flexographic printing plate precursor according to claim 1 or 2, wherein the relief-forming layer further contains a hydroxycarboxylic acid (C). The flexographic printing plate precursor according to claim 4, which contains diglucosyl gallic acid as the hydroxycarboxylic acid (C). A method for producing a flexographic printing plate, comprising a step of forming a relief by partially removing the relief-forming layer of the flexographic printing plate precursor according to claim 1 or 2. 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). A method for producing a printed matter, comprising the steps of: applying ink to the relief of the flexographic printing plate according to claim 7; and transferring the ink to a substrate. The method for producing a printed matter according to claim 8, in which the ink is an ultraviolet-curable ink and/or an electron beam-curable ink.