Flexographic printing plate master and method for manufacturing flexographic printing plates

Abstract

The present invention addresses the problem of providing: a flexographic printing plate original plate in which the sensitivity of a heat-sensitive image formation layer is high, and with which it is possible to suppress the formation of white spots in a line drawing when printed on a flexographic printing plate; and a method for manufacturing a flexographic printing plate in which said flexographic printing plate original plate is used. This flexographic printing plate original plate has, in the stated order, a support, a photosensitive resin layer, a barrier layer, and the heat-sensitive image formation layer, wherein: the barrier layer contains a first infrared ray absorbing dye; the heat-sensitive image formation layer contains a UV ray absorbing agent and a second infrared ray absorbing dye; and the amount of a compound that has substantially no absorption in the region of the barrier layer having a wavelength of 900–1200 nm, and has absorption in the region having a wavelength of 300–400 nm, is at least 0 mass% and less than 0.1 mass% of the mass of the barrier layer.

Description

[Technical Field]

[0001] The present invention relates to a flexographic printing plate master and a method for manufacturing a flexographic printing plate using the same. [Background technology]

[0002] A flexographic printing plate typically consists of a photosensitive resin layer made of a photosensitive resin composition on a support made of polyester film or the like. Flexographic printing plates are manufactured by exposing the surface of the photosensitive resin layer of this plate to a predetermined image, and then removing the resin from the unexposed areas.

[0003] In so-called analog flexographic printing plates, a negative film with a predetermined image already formed on it is placed on a photosensitive resin layer, and the predetermined image is exposed to the surface of the photosensitive resin layer through this negative film. In contrast, a flexographic printing plate using the LAM (Laser ablation mask) method has a thermal image forming layer (infrared ablation layer) pre-formed on top of a photosensitive resin layer. Digitized negative image information is directly drawn onto the thermal image forming layer using an infrared laser to create a desired negative pattern, and then a predetermined image is exposed to the surface of the photosensitive resin layer through this negative pattern.

[0004] As an example of such a LAM-type flexographic printing plate, Patent Document 1 describes a flexographic printing plate in which a support, a photosensitive resin layer, and an infrared ablation layer containing a binder polymer and an infrared absorbing substance are laminated. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-137515 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present inventors investigated the flexographic printing plate described in Patent Document 1 and found that there is room for improvement in the sensitivity of the drawing formed on the thermal image forming layer (infrared ablation layer). Furthermore, the inventors have revealed that when a high-intensity ultraviolet (UV) exposure machine is used, if a fine line pattern is formed as the image portion on the photosensitive resin layer, white areas will occur in the printed line drawing.

[0007] Therefore, the object of the present invention is to provide a flexographic printing plate master that has high sensitivity of the thermal image forming layer and can suppress the occurrence of white gaps in line drawings when made into a flexographic printing plate, and a method for manufacturing a flexographic printing plate using the same. [Means for solving the problem]

[0008] The inventors of the present invention conducted diligent studies to achieve the above objectives and found that when both the barrier layer and the thermal image-forming layer contain infrared absorbing dyes, and the content of a compound that may be included in the barrier layer, which has substantially no absorption in the wavelength region of 900 to 1200 nm and absorption in the wavelength region of 300 to 400 nm, is between 0% by mass and less than 0.1% by mass relative to the mass of the barrier layer, the sensitivity of the thermal image-forming layer is high, and the occurrence of white spots in line drawings when made into a flexographic printing plate can be suppressed, thus completing the present invention. In other words, the inventors have found that the above problem can be solved by the following configuration.

[0009] [1] A flexographic printing plate having a support, a photosensitive resin layer, a barrier layer, and a thermal image forming layer in this order, The barrier layer contains a first infrared absorbing dye, The thermal image forming layer contains an ultraviolet absorber and a second infrared absorbing dye. A flexographic printing plate master in which the content of a compound in the barrier layer that has substantially no absorption in the wavelength region of 900 to 1200 nm and absorption in the wavelength region of 300 to 400 nm is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer. [2] The flexographic printing plate according to [1], wherein both the first infrared absorbing dye and the second infrared absorbing dye are compounds that have absorption at a wavelength of 1070 nm and have a mass extinction coefficient of 50 L / (g·cm) or more at a wavelength of 1070 nm. [3] The flexographic printing plate described in [2], wherein both the first infrared absorbing dye and the second infrared absorbing dye are compounds represented by formula (1) described later. [4] The flexographic printing plate according to [2] or [3], wherein both the barrier layer and the thermal image forming layer contain a third infrared absorbing dye having absorption at a wavelength of 830 nm. [5] The photosensitive resin layer contains monomers, polymerization initiators, base polymers, and water-dispersible particles. Water-dispersible particles have a carbon-carbon double bond, A flexographic printing plate according to any one of [1] to [4], wherein the number of carbon-carbon double bonds on the surface of the water-dispersible particles is 21 or less. [6] A method for manufacturing a flexographic printing plate having a non-image portion and an image portion, A mask formation step is performed to form an image on the thermal image forming layer of a flexographic printing plate according to any of [1] to [4], and to form a mask, Following the mask formation process, an exposure process is performed in which the photosensitive resin layer of the flexographic printing plate is exposed to the image through the mask. A method for manufacturing a flexographic printing plate, comprising an exposure step followed by a developing step in which the plate is developed using a developing solution to form non-image areas and image areas. [7] The method for manufacturing a flexographic printing plate according to [6], wherein the developing solution contains 50% by mass or more of water. [8] A method for manufacturing a flexographic printing plate according to [6] or [7], wherein the developing solution contains a surfactant represented by formula (2) described later. [Effects of the Invention]

[0010] According to the present invention, there can be provided a flexographic printing plate original plate having a high sensitivity of a heat-sensitive image forming layer and capable of suppressing the occurrence of white voids in line drawings when made into a flexographic printing plate, and a method for manufacturing a flexographic printing plate using the same.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the flexographic printing plate original plate of the present invention. [Figure 2A] FIG. 2A is a schematic cross-sectional view showing one step in an example of the method for manufacturing a flexographic printing plate of the present invention. [Figure 2B] FIG. 2B is a schematic cross-sectional view showing one step in an example of the method for manufacturing a flexographic printing plate of the present invention. [Figure 2C] FIG. 2C is a schematic cross-sectional view showing one step in an example of the method for manufacturing a flexographic printing plate of the present invention. [Figure 2D] FIG. 2D is a schematic cross-sectional view showing one step in an example of the method for manufacturing a flexographic printing plate of the present invention. [Figure 3A] FIG. 3A is a schematic cross-sectional view showing one step in an example of the method for manufacturing a known flexographic printing plate. [Figure 3B] FIG. 3B is a schematic cross-sectional view showing one step in an example of the method for manufacturing a known flexographic printing plate. [Figure 3C] FIG. 3C is a schematic cross-sectional view showing one step in an example of the method for manufacturing a known flexographic printing plate. [Figure 3D] FIG. 3D is a schematic cross-sectional view showing one step in an example of the method for manufacturing a known flexographic printing plate.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. Furthermore, in this specification, each component may be represented by a single substance or by a combination of two or more substances. When two or more substances are used in combination for each component, the content of that component refers to the total content of the combined substances, unless otherwise specified.

[0013] [Flexographic printing plate original] The flexographic printing plate of the present invention is a flexographic printing plate having a support, a photosensitive resin layer, a barrier layer, and a thermal image forming layer in this order. Furthermore, the barrier layer contains a first infrared-absorbing dye. Furthermore, the above-mentioned thermal image-forming layer contains an ultraviolet absorber and a second infrared absorbing dye. Furthermore, the content of a compound in the barrier layer that substantially does not absorb in the wavelength region of 900 to 1200 nm and absorbs in the wavelength region of 300 to 400 nm (hereinafter also referred to as "UV-absorbing impurity") is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer.

[0014] Figure 1 is a schematic cross-sectional view showing an example of a flexographic printing plate according to the present invention. The flexographic printing plate 10 shown in Figure 1 comprises a support 1, a photosensitive resin layer 2, a barrier layer 3, and a thermal image forming layer 4 in that order. Furthermore, the flexographic printing plate master of the present invention may have a cover sheet 5, as shown in Figure 1.

[0015] In the present invention, as described above, if both the barrier layer and the thermal image forming layer contain an infrared absorbing dye, and the amount of UV absorbing impurities that may be contained in the barrier layer is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer, the sensitivity of the thermal image forming layer is high, and the occurrence of white spots in line drawings can be suppressed when a flexographic printing plate is made. Although this is not entirely clear, the inventors speculate the following: First, the reason why the sensitivity of the thermal image forming layer is increased is thought to be because, instead of using pigments such as carbon black as the infrared absorbing material, dyes with small particle sizes are incorporated, making ablation by infrared light more likely to progress. On the other hand, white areas in line drawings are thought to occur due to the following reasons. In other words, as shown in Figures 3A to 3D, if there is no barrier layer, when an image is formed on the thermal image forming layer 4, residue 4a of the thermal image forming layer is generated (see Figure 3B). Subsequently, when the photosensitive resin layer 2 is exposed, the effect of the residue 4a creates exposed areas 2c and weakly exposed areas 2d (see Figure 3C). After development, the image is formed with the edges 2e of the exposed areas 2c raised (see Figure 3D), making it difficult to apply pressure to the center of the printed line drawing, which is thought to cause white spots. This becomes apparent when a high-intensity UV exposure machine is used, suggesting that during exposure, monomer components in the weakly exposed areas 2d migrate to the edges of the exposed areas 2c. In contrast, when using the flexographic printing plate of the present invention, as shown in Figures 2A to 2D, the presence of the barrier layer 3 suppresses the generation of residue in the thermal image forming layer 4. Furthermore, regarding the residue 3a of the barrier layer, since the amount of UV-absorbing impurities that can be contained in the barrier layer is extremely small, in the subsequent exposure process, only the exposed areas 2b are formed, and the weakly exposed areas are not formed, thus suppressing whiteout in the line drawing. In Figures 2A to 2D and 3A to 3D, a floor 2a is formed on the photosensitive resin layer 2 by back exposure from the support 1 side before forming an image on the thermal image forming layer 4. The infrared-absorbing dyes will be described in detail below, followed by a detailed description of the layer configuration of the flexographic printing plate master of the present invention.

[0016] [First infrared absorbing dye / Second infrared absorbing dye] The first infrared-absorbing dye contained in the barrier layer and the second infrared-absorbing dye contained in the thermal image forming layer are not particularly limited as long as they are solvent-soluble dyes, and examples include nitroso compounds and their metal complex salts, polymethine dyes (cyanine dyes), squarylium dyes, thiol nickel complex salts, phthalocyanine dyes, triallylmethane dyes, immonium dyes, diimmonium dyes, naphthoquinone dyes, and anthraquinone dyes. Furthermore, from the viewpoint of excellent developability in aqueous developers and less contamination of the developing machine, it is preferable to use water-soluble dyes. From the viewpoint of a wide range of structural options and the ability to select dyes that are both durable and water-soluble, it is preferable to use dyes that are soluble in organic solvents.

[0017] In the present invention, it is preferable that both the first infrared absorbing dye and the second infrared absorbing dye are compounds (hereinafter also referred to as "specific dyes") that have absorption at a wavelength of 1070 nm and a mass extinction coefficient at a wavelength of 1070 nm of 50 L / (g·cm) or more, in order to increase the sensitivity of the thermal image forming layer. Furthermore, the above-mentioned specific dye is more preferably characterized by a mass extinction coefficient of 50 to 200 L / (g·cm), and even more preferably by 50 to 100 L / (g·cm). Here, the mass extinction coefficient refers to the value calculated using the following method. First, 10 mg of the infrared-absorbing dye to be measured is diluted with 1 L of methyl ethyl ketone to obtain the measurement solution. Next, the absorption spectrum of the obtained measurement solution is measured in the infrared absorption range (200 nm to 3300 nm). The measurement instrument used is the UH4150 manufactured by Hitachi High-Tech Science Corporation. Next, the mass extinction coefficient at a wavelength of 1070 nm is determined from the obtained absorption spectrum (unit: L / g·cm). Specifically, the transmittance T (%) at a cell length L (cm) in a solution of a specified concentration C (g / L) is measured, and the mass extinction coefficient k is calculated using the following formula. Mass extinction coefficient k = A / CL (unit: L / (g·cm)) Absorbance A=-log 10 (T)

[0018] In the present invention, it is preferable that the specified dyes, as the first infrared absorbing dye and the second infrared absorbing dye, are compounds represented by the following formula (1), in order to further increase the sensitivity of the thermal image forming layer. [ka]

[0019] In formula (1) above, R represents a monovalent organic group, and multiple Rs may be the same or different from one another. Also, in equation (1) above, X - represents a monovalent anion, and multiple X - They may be the same or different from one another.

[0020] Examples of monovalent organic groups represented by R in formula (1) above include alkyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkenyl groups, and -NR groups. 11 R 12 (R 11 and R 12 Each of these independently represents a hydrogen atom or a hydrocarbon group. Examples include ( ), and these groups may further have substituents. Examples of alkyl groups include linear or branched alkyl groups having 1 to 18 carbon atoms, specifically methyl, ethyl, propyl, butyl, pentyl, tert-pentyl, and n-hexyl groups. Examples of the cycloalkyl group include monocyclic or polycyclic cycloalkyl groups having 3 to 20 carbon atoms, specifically, cyclopentyl group, cyclopentylmethyl group, cyclopentylethyl group, cyclohexyl group, cyclohexylmethyl group, cyclohexylethyl group, and the like. Examples of the aryl group include aryl groups having 6 to 14 carbon atoms, specifically, for example, phenyl group, methylphenyl group, tolyl group, xylyl group, naphthyl group, anthryl group, phenanthryl group, pyrenyl group, and the like. Examples of the aralkyl group include aralkyl groups having 7 to 20 carbon atoms, specifically, benzyl group, phenethyl group, 2-phenylethan-2-yl group, naphthylmethyl group, and the like. Examples of the alkenyl group include alkenyl groups having 3 to 20 carbon atoms, specifically, vinyl group, allyl group, and the like. R 11 and R 12 Examples of the hydrocarbon group represented by one embodiment of and include, for example, the above alkyl group and the above aryl group.

[0021] X in the above formula (1) - Examples of the monovalent anion represented by include, for example, ClO4 - PF6 - BF4 - and bis(trifluoromethanesulfonyl)imide anion represented by the following formula, and the like. Also, as the monovalent anion in X - anions described in

[0016] to

[0023] of JP-A No. 2011-38007 can also be used.

Chemical formula

[0022] 〔Third infrared absorbing dye〕 In the present invention, when the first infrared absorbing dye and the second infrared absorbing dye are the specified dyes described above, it is preferable that both the barrier layer and the thermal image forming layer further contain a third infrared absorbing dye having absorption at a wavelength of 830 nm, for the reason that the sensitivity of the thermal image forming layer becomes higher. Here, as the third infrared-absorbing dye, a dye having absorption at a wavelength of 830 nm can be appropriately selected from known infrared-absorbing dyes and used, for example, azo dyes, squarylium dyes, croconate dyes, triarylamine dyes, thiazolium dyes, indolium dyes, oxonol dyes, oxazolium dyes, cyanine dyes, merocyanine dyes, phthalocyanine dyes, indocyanine dyes, indotricarbocyanine dyes, oxatricarbocyanine dyes, thiocyanine dyes, thiatricarbocyanine dyes, merocyanine dyes Examples include dyes, cryptocyanine dyes, naphthalocyanine dyes, polyaniline dyes, polypyrrole dyes, polythiophene dyes, chalcogenopyrilolarylidene and bi(chalcogenopyrilol)polymethine dyes, oxyindolidine dyes, pyrylium dyes, pyrazolin azo dyes, oxazine dyes, naphthoquinone dyes, anthraquinone dyes, quinoneimine dyes, methine dyes, arylmethine dyes, squalane dyes, oxazole dyes, croconin dyes, porphyrin dyes, and any of these dyes in a substituted or ionic form. The third infrared absorbing dye is preferably a cyanine dye, and more preferably a closed-type cyanine dye, for the reasons that the effects of the present invention are superior. Examples of such dyes include IR-813 (p-toluenesulfonate) (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0023] [Barrier layer] The barrier layer of the flexographic printing plate master of the present invention is a layer containing the first infrared absorbing dye described above, and functions as an infrared ablation layer together with the heat-sensitive image-forming layer described later. Furthermore, the barrier layer is a layer in which the amount of UV-absorbing impurities that may be contained in the barrier layer is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer.

[0024] <Content of the first infrared absorption dye> The content of the above-mentioned first infrared absorption dye contained in the barrier layer is preferably 2 to 75% by mass, more preferably 5 to 70% by mass, based on the mass of the barrier layer, that is, the total mass of the solid content of the composition used for formation.

[0025] <UV absorption impurities> The UV absorption impurities that may be contained in the barrier layer are, as described above, compounds that substantially have no absorption in the wavelength range of 900 to 1200 nm and have absorption in the wavelength range of 300 to 400 nm. Here, "substantially having no absorption" means that the absorbance at a cell length of 1 cm of a 1.0 g / liter dichloromethane solution of the UV absorption impurities is 5.0 or less, preferably 2.0 or less, and more preferably 0 to 1.0. In addition, the content of the UV absorption impurities is 0% by mass or more and less than 0.1% by mass, but it is preferably 0% by mass, that is, not containing the UV absorption impurities.

[0026] <Thermally decomposable compound> The barrier layer preferably contains a thermally decomposable compound as a binder. [[ID=二十一]] [[ID=二十二]]Examples of the thermally decomposable compound include ammonium nitrate, potassium nitrate, sodium nitrate, nitrocellulose, polyvinylpyrrolidone, azo compounds, diazo compounds, hydrazine derivatives, acrylic resins, metals, and metal oxides. Among these, it is preferably a polymer compound in terms of the coating property of the solution, etc., and more preferably polyvinylpyrrolidone, nitrocellulose, and acrylic resin. The content of the thermally decomposable compound is preferably 80% by mass or less, more preferably 15 to 60% by mass, based on the mass of the barrier layer, that is, the total mass of the solid content of the composition used for formation.

[0027] The film thickness of the barrier layer is preferably 0.1 to 6 μm, more preferably 0.2 to 3 μm.

[0028] [Thermal image forming layer] The thermal image-forming layer of the flexographic printing plate master of the present invention is a layer containing an ultraviolet absorber and the second infrared-absorbing dye described above, and functions as an infrared ablation layer.

[0029] <Content of the second infrared-absorbing dye> The content of the second infrared absorbing dye described above in the thermal image forming layer is preferably 2 to 75% by mass, and more preferably 5 to 70% by mass, relative to the mass of the thermal image forming layer, i.e., the total mass of the solids of the composition used for formation.

[0030] <UV absorber> Suitable ultraviolet absorbers included in the thermal image forming layer include, for example, compounds that have absorption in the 300 nm to 400 nm range. Examples of the above-mentioned compounds include, for example, benzotriazole compounds, triazine compounds, benzophenone compounds, and carbon black. Furthermore, specific examples of the above compounds include, for example, metal compounds such as iron powder, diamine metal complexes, dithiol metal complexes, phenolthiol metal complexes, mercaptophenol metal complexes, arylaluminum metal salts, inorganic compounds containing crystal water, copper sulfate, chromium sulfide, and silicate compounds; and metal oxides such as titanium dioxide, vanadium oxide, manganese oxide, iron oxide, cobalt oxide, and tungsten oxide. Of these, it is preferable to use a benzophenone compound or carbon black.

[0031] The amount of ultraviolet absorber is preferably 0.1 to 75% by mass, and more preferably 1 to 50% by mass, relative to the mass of the thermal image forming layer, i.e., the total mass of the solids of the composition used for formation.

[0032] <Thermal decomposable compounds> The thermal image-forming layer preferably contains a thermally decomposable compound as a binder. The pyrolytic compounds are the same as those described in the barrier layer section above, and their preferred examples and content are also the same.

[0033] The thickness of the heat-sensitive image-forming layer is preferably 0.1 to 6 μm, and more preferably 0.5 to 3 μm.

[0034] [Photosensitive resin layer] The photosensitive resin layer of the flexographic printing plate master of the present invention is not particularly limited and can be formed using conventionally known photosensitive resin compositions, for example, a resin composition containing water-dispersible latex, rubber, photopolymerizable monomer, photopolymerization initiator, surfactant, etc.

[0035] In the present invention, it is preferable that the photosensitive resin layer contains a monomer, a polymerization initiator, a base polymer, and water-dispersible particles, the water-dispersible particles have carbon-carbon double bonds, and the number of carbon-carbon double bonds on the surface of the water-dispersible particles is 21 or less, in order to further suppress the occurrence of white areas in line drawings when made into a flexographic printing plate. This is because, when forming the photosensitive resin layer, the fusion of water-dispersible particles that may occur during coating and drying is suppressed, making it possible to remove any unwanted image formation caused by the weakly exposed areas mentioned above through development. Such photosensitive resin layers are described in paragraphs

[0016] to

[0044] of International Publication No. 2020 / 158778. The description in the above document is incorporated herein by reference.

[0036] The thickness of the photosensitive resin layer is preferably 0.2 to 6 mm.

[0037] [Support] The material used for the support of the flexographic printing plate master of the present invention is not particularly limited, but materials with high dimensional stability are preferably used. Examples include metals such as steel, stainless steel, and aluminum; polyester (e.g., PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate)), PI (polyimide), polyamide, LCP (liquid crystal polymer), and PAN (polyacrylonitrile); plastic resins such as polyvinyl chloride; synthetic rubbers such as styrene-butadiene rubber; glass fiber-reinforced plastic resins (such as epoxy resins and phenolic resins); cloth, paper, and the like. From the viewpoint of dimensional stability and availability, the support material is preferably a polymer film or a cloth, and more preferably a polymer film. The form of the support material is determined by whether the polymer layer is in the form of a sheet or a sleeve.

[0038] As for the fabric, natural fibers such as cotton, linen, silk, and wool, and synthetic fibers such as acetate, vinylon, vinylidene, polyvinyl chloride, acrylic, polypropylene, polyethylene, polyurethane, fluorine-based filaments, polyclar, rayon, nylon, polyamide, and polyester can be used to create woven fabrics, knitted fabrics, and nonwoven fabrics, as well as plain weaves and twill weaves. Examples of polymer films include films made from various polymers such as polyester (e.g., PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate)), PI (polyimide), polyamide, LCP (liquid crystal polymer), PAN (polyacrylonitrile); plastic resins such as polyvinyl chloride; synthetic rubbers such as styrene-butadiene rubber; and glass fiber-reinforced plastic resins (such as epoxy resins and phenolic resins). Among these, polyester films are preferred from the viewpoint of dimensional stability and other factors. Examples of the above-mentioned polyester films include PET film, PBT film, and PEN film, but from the viewpoint of dimensional stability and other factors, PET (polyethylene terephthalate) film is preferred.

[0039] The thickness of the support film is not particularly limited, but from the viewpoint of dimensional stability and handling, it is preferably 5 to 3000 μm, more preferably 50 to 2000 μm, and even more preferably 100 to 1000 μm.

[0040] [Cover sheet] The flexographic printing plate of the present invention may have a cover sheet, as shown in Figure 1. Such cover sheets are not particularly limited, but are preferably transparent polymer films, and may be single layers or laminated with two or more layers. Here, "transparent" as used in this invention means that the transmittance of visible light is 60% or more, preferably 80% or more, and particularly preferably 90% or more. Examples of polymer film materials include cellulose polymers; acrylic polymers having acrylic acid ester polymers such as polymethyl methacrylate and lactone ring-containing polymers; thermoplastic norbornene polymers; polycarbonate polymers; polyester polymers such as polyethylene terephthalate, polyethylene naphthalate, and fluoropolyester polymers; styrene polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin); polyolefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and polybutadiene; vinyl chloride polymers; amide polymers such as nylon and aromatic polyamides; imide polymers; sulfone polymers; polyethersulfone polymers; polyetheretherketone polymers; polyphenylene sulfide polymers; vinylidene chloride polymers; vinyl alcohol polymers; vinyl butyral polymers; arylate polymers; polyoxymethylene polymers; epoxy polymers; or polymers which are mixtures of these polymers.

[0041] Furthermore, the surface of the cover sheet (the surface on which the thermal image forming layer is formed) may be treated with a release agent to suppress adhesion of the thermal image forming layer and improve the peelability of the cover sheet. Such a release agent may be applied to the surface of the cover sheet to form a release layer. Examples of release agents include silicone-based release agents and alkyl-based release agents.

[0042] The film thickness of the cover sheet is preferably 25 to 250 μm.

[0043] [Functional Layer] The flexographic printing plate master of the present invention may include an arbitrary functional layer between the photosensitive resin layer and the barrier layer described above. The functional layer described above is not particularly limited, but it is preferable to use a water-soluble polymer in order to block oxygen in the atmosphere, which can cause polymerization inhibition during UV exposure, and to suppress mass transfer between the heat-sensitive image-forming layer and the photosensitive resin layer. Examples of water-soluble polymers include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, water-soluble cellulose derivatives, polyethylene glycol, poly(meth)acrylonitrile, and polyamide. Furthermore, the above-mentioned functional layer may contain additives to the extent that they do not adversely affect performance. Examples of the above-mentioned additives include plasticizers and various stabilizers. Furthermore, in order to mitigate the shortcomings of the above-mentioned functional layer, additives such as defoaming agents and leveling agents may be added, to the extent that they do not adversely affect performance.

[0044] [Method for manufacturing flexographic printing plates] The present invention relates to a method for manufacturing a flexographic printing plate, which has a non-image portion and an image portion. A mask forming step is to form an image on the heat-sensitive image forming layer of the flexographic printing plate master of the present invention described above, and to form a mask, Following the mask formation step described above, an exposure step is performed in which the photosensitive resin layer of the flexographic printing plate master of the present invention described above is exposed in an image-like manner through the mask described above. The process includes a developing step, which follows the exposure step, in which the image is developed using a developing solution to form non-image areas and image areas.

[0045] [Mask Forming Process] The mask formation step described above is a step in which an image is formed on the thermal image forming layer to form a mask to be used in the exposure step described later. As mentioned above, the barrier layer of the flexographic printing plate master of the present invention functions as an infrared ablation layer together with the thermal image forming layer, so when an image is formed on the thermal image forming layer, an image is also formed on the barrier layer at the same time. Here, when an infrared laser is irradiated onto the thermal image-forming layer, heat is generated by the action of a second infrared-absorbing dye. This heat decomposes the thermally decomposable compound, causing the thermal image-forming layer to be removed, or laser-melted. Therefore, by selectively laser-melting the heat-sensitive image-forming layer based on image data, an image mask capable of forming a latent image in the photosensitive resin layer can be obtained.

[0046] Infrared laser irradiation uses lasers with an oscillation wavelength in the range of 750 nm to 3000 nm. Examples of such lasers include solid-state lasers such as ruby ​​lasers, alexandrite lasers, perovskite lasers, Nd-YAG lasers, and emerald glass lasers; semiconductor lasers such as InGaAsP, InGaAs, and GaAsAl; and dye lasers such as rhodamine dyes. Furthermore, fiber lasers, which amplify these light sources using fibers, can also be used. Of these, it is preferable to use an exposure light source with an oscillation wavelength of 900 to 1200 nm, and more preferably a fiber laser, because this results in higher sensitivity of the thermal image forming layer.

[0047] [Exposure process] The above exposure step is a step of exposing the photosensitive resin layer in the shape of an image through the mask obtained in the above mask formation step, and by irradiating the photosensitive resin layer with ultraviolet light in the shape of an image, crosslinking and / or polymerization can be induced in the areas irradiated with ultraviolet light, thereby curing the layer.

[0048] [Development process] The above development process involves developing the image using a developing solution to form non-image areas and image areas.

[0049] The developer used in the above development process is not particularly limited, and conventionally known developers can be used. However, from the viewpoint of reducing environmental impact, it is preferable to use a developer containing 50% by mass or more of water (hereinafter also referred to as "aqueous developer"). The developer may be an aqueous solution or a suspension (for example, an aqueous dispersion). Furthermore, the water content in the aqueous developer is preferably 80 to 99.99% by mass, and more preferably 90 to 99.9% by mass, relative to the total mass of the aqueous developer.

[0050] In the present invention, it is preferable that the aqueous developer contains a surfactant represented by the following formula (2). [ka]

[0051] In formula (2) above, A represents an alkylene group having 2 to 4 carbon atoms, and R 1 A represents a hydrogen atom or substituent, and n represents an integer from 1 to 100. When n is an integer from 2 to 100, multiple As may be the same or different from one another.

[0052] In formula (2) above, A represents an alkylene group having 2 to 4 carbon atoms, but it is preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an ethylene group or an n-propylene group.

[0053] R in equation (2) above 1Examples of substituents represented by one embodiment include alkyl groups, alkoxy groups, alkylcarbonyl groups, alkoxycarbonyl groups, alkylcarbonyloxy groups, alkylamino groups, dialkylamino groups, alkylamide groups, alkenyl groups, alkynyl groups, halogen atoms, cyano groups, nitro groups, alkylthiol groups, and N-alkylcarbamate groups, with alkyl groups being preferred among them. Preferred alkyl groups for substituents are, for example, alkyl groups having 1 to 6 carbon atoms, and more preferably alkyl groups having 1 to 4 carbon atoms. Specifically, examples include methyl groups, ethyl groups, propyl groups, and n-butyl groups. Note that R in equation (2) above 1 This represents a hydrogen atom or a substituent, but it is preferable to use a hydrogen atom because it results in good dispersibility of the developing residue.

[0054] In formula (2) above, n represents an integer from 1 to 100, but it is preferably an integer from 1 to 30, more preferably an integer from 5 to 20, and even more preferably an integer from 5 to 15, for the reason that the dispersibility of the developing residue is good.

[0055] [Rinsing process] The present invention preferably includes a rinsing step after the development step, in which the surfaces of the non-image area and the image area formed in the development step are rinsed with water.

[0056] Rinsing methods in the above rinsing process include washing with tap water, spraying with high-pressure water, and using a batch-type or transport-type brush-type washing machine known as a flexographic printing plate developing machine to mainly brush the non-image and image areas in the presence of water. [Examples]

[0057] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.

[0058] [Example 1] [Preparation of Synthetic Latex A] 465.0 g of aqueous dispersion latex (Nipol LX111NF, aqueous dispersion latex of polybutadiene, 55% solids, manufactured by Zeon Corporation) and 327.5 g of distilled water were added to a 1 L three-necked flask, and the mixture was heated to 75°C while stirring under a nitrogen stream. After 30 minutes, an aqueous solution of 9.6 g of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate (VA-057, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in 65.0 g of distilled water was added all at once. After 3 hours, the temperature was raised to 90°C, and after 6 hours, it was allowed to cool to room temperature (23°C). Next, the mixture was filtered using nonwoven filter paper (T-270, manufactured by ADVANTEC) to remove aggregates, and synthetic latex A with a solid content of 30% by mass was prepared. Furthermore, when the amount of carbon-carbon double bonds on the surface of the water-dispersible particles of synthetic latex A (hereinafter also abbreviated as "surface C=C amount") was measured using the method described in paragraph

[0016] of International Publication No. 2020 / 158778, it was found to be 20, as shown in Table 1 below.

[0059] [Preparation of photosensitive resin composition] 103 parts by mass of the above-mentioned synthetic latex A (30% solids content), 11 parts by mass of telechelic polymer (BAC-45, manufactured by Osaka Organic Chemical Industry Co., Ltd.) (polybutadiene with acryloyloxy groups at both ends, Mw=10,000), and 9 parts by mass of 1,9-nonanediol dimethacrylate (NK ester NOD-N, manufactured by Shin Nakamura Chemical Industry Co., Ltd.) were mixed, and the water was evaporated in a dryer heated to 60°C for 3 hours to obtain a mixture containing water-dispersible particles. This mixture, along with 23 parts by mass of butadiene rubber (NF35R, manufactured by Asahi Kasei Corporation), 15 parts by mass of plasticizer (Diana Process Oil PW-32, manufactured by Idemitsu Kosan Co., Ltd.), and 4 parts by mass of surfactant (Rapizol A-90, 90% effective content, manufactured by NOF Corporation), was kneaded for 45 minutes in a kneader set to 110°C. Then, 0.2 parts by mass of a thermal polymerization inhibitor and 8 parts by mass of a photopolymerization initiator (benzyldimethyl ketal, manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the kneader and kneaded for 5 minutes to obtain a photosensitive resin composition.

[0060] [Fabrication of laminates for infrared ablation layers] A coating solution for a heat-sensitive image-forming layer was obtained by adding 90.5 parts by mass of methyl ethyl ketone to 1.2 parts by mass of infrared absorbing dye (CIR-RL, manufactured by Nippon Carlit Co., Ltd.), 1.3 parts by mass of 2,2',4,4'-tetrahydroxybenzophenone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2.6 parts by mass of curcumin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 4.3 parts by mass of nitrocellulose (H1 / 8, manufactured by Taihei Chemical Products Co., Ltd.), and stirring until homogeneous. Next, a coating solution for a heat-sensitive image-forming layer was applied to one side of a 75 μm thick silica-containing PET film (Toyobo Ester® Film U4, manufactured by Toyobo Film Solutions Co., Ltd.) [cover sheet] using a bar coater to achieve a dry thickness of 1.4 μm. After drying, the film was dried in an oven set to 90°C for 2 minutes to obtain a heat-sensitive image-forming layer. Next, 1.3 parts by mass of infrared absorbing dye (CIR-RL, manufactured by Nippon Carlit Co., Ltd.) and 4.5 parts by mass of nitrocellulose (H1 / 8, manufactured by Taihei Chemical Products Co., Ltd.) were added, to which 51.8 parts by mass of acetone and 42.4 parts by mass of cyclopentanone were added, and the mixture was stirred until homogeneous to obtain a coating solution for the barrier layer. Next, a barrier layer coating solution was applied to the upper surface of the heat-sensitive image-forming layer using a bar coater to a thickness of 0.4 μm after drying, and then dried in an oven set to 90°C for 2 minutes to obtain a laminate for infrared ablation layers having a cover sheet, a heat-sensitive image-forming layer, and a barrier layer in that order. Furthermore, CIR-RL (manufactured by Nippon Carlit Co., Ltd.), an infrared absorbing dye, is a compound that absorbs at a wavelength of 1070 nm, and its mass extinction coefficient at a wavelength of 1070 nm was 66.2 L / (g·cm), as shown in Table 1 below. CIR-RL (manufactured by Nippon Carlit Co., Ltd.) is the compound represented by formula (1) described above.

[0061] [Preparation of flexographic printing plates] An adhesive layer was formed on one side of a 125 μm thick PET film (substrate) by applying an adhesive to the substrate. Then, the photosensitive resin composition prepared as described above was sandwiched between the adhesive layer and the side of the laminate for the infrared ablation layer prepared as described above that was coated with a heat-sensitive image-forming layer. By pressing the laminate with a press heated to 80°C so that the thickness of the photosensitive resin composition layer (photosensitive resin layer) was 1.14 mm, a flexographic printing plate master was produced having the substrate, adhesive layer, photosensitive resin layer, barrier layer, and heat-sensitive image-forming layer in this order.

[0062] [Examples 2 and 4 and Comparative Examples 1-2] A flexographic printing plate was prepared in the same manner as in Example 1, except that the types and content (mass%) of each component in the barrier layer were changed as shown in Table 1 below. The ultraviolet absorber contained in the barrier layer of Example 2 and Comparative Example 1 is 2,2',4,4'-tetrahydroxybenzophenone, as shown in Table 1 below. This compound has substantially no absorption in the wavelength range of 900 to 1200 nm and absorbs in the wavelength range of 300 to 400 nm. Furthermore, the third infrared-absorbing dye contained in the barrier layer and thermal image-forming layer of Example 4 is IR-813 (p-toluenesulfonate) (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a compound that absorbs at a wavelength of 830 nm. In the thermal image-forming layer of Example 4, the amount of nitrocellulose was reduced by the amount to which the third infrared-absorbing dye was added.

[0063] [Example 3] A flexographic printing plate was prepared in the same manner as in Example 1, except that a photosensitive resin composition prepared by the following method was used. [Preparation of photosensitive resin composition] 56 parts by mass of commercially available Nipol LX111NF (55% solids content, manufactured by Nippon Zeon Co., Ltd.), 11 parts by mass of telechelic polymer (BAC-45, manufactured by Osaka Organic Chemical Industry Co., Ltd.) (polybutadiene with acryloyloxy groups at both ends, Mw=10,000), and 9 parts by mass of 1,9-nonanediol dimethacrylate (NK ester NOD-N, manufactured by Shin Nakamura Chemical Industry Co., Ltd.) were mixed, and the water was evaporated in a dryer heated to 60°C for 3 hours to obtain a mixture containing water-dispersible particles. This mixture, along with 23 parts by mass of butadiene rubber (NF35R, manufactured by Asahi Kasei Corporation), 15 parts by mass of plasticizer (Diana Process Oil PW-32, manufactured by Idemitsu Kosan Co., Ltd.), and 4 parts by mass of surfactant (Rapizol A-90, 90% effective content, manufactured by NOF Corporation), was kneaded for 45 minutes in a kneader set to 110°C. Then, 0.2 parts by mass of a thermal polymerization inhibitor and 8 parts by mass of a photopolymerization initiator (benzyldimethyl ketal, manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the kneader and kneaded for 5 minutes to obtain a photosensitive resin composition. Furthermore, for Nipol LX111NF, the surface carbon-carbon content on the surface of the water-dispersible particles was 21.4, as shown in Table 1 below.

[0064] [Comparative Example 3] A flexographic printing plate was prepared in the same manner as in Example 1, except that the laminate for the infrared ablation layer was changed to the one described below. The components of the thermal image forming layer are also listed in Table 1 below. [Fabrication of laminates for infrared ablation layers] 50 parts by mass of acrylic resin (Hyperl M5000, manufactured by Negami Kogyo Co., Ltd.), 50 parts by mass of elastomer (Nipol DN101, NBR, manufactured by Nippon Zeon Co., Ltd.), and 100 parts by mass of carbon black (MA8, manufactured by Mitsubishi Chemical Corporation) as an infrared absorbing pigment were mixed with 600 parts by mass of methyl isobutyl ketone and mixed by stirring with a feather. The resulting mixture was dispersed in a paint shaker, and then methyl isobutyl ketone was further added until the solid content was 15% by mass, thereby obtaining a polymer / carbon black dispersion (coating liquid for a heat-sensitive image forming layer). Next, a thermal image forming layer coating solution was applied to one side of a 75 μm thick silica-containing PET film (Toyobo Ester® Film U4, manufactured by Toyobo Film Solutions Co., Ltd.) [cover sheet] using a bar coater to achieve a dry thickness of 1.0 μm. After drying in an oven set to 140°C for 1 minute, a laminate for an infrared ablation layer was fabricated having a cover sheet and a thermal image forming layer, but without a barrier layer. Furthermore, the mass extinction coefficient of carbon black (MA8, manufactured by Mitsubishi Chemical Corporation), an infrared absorbing pigment, at a wavelength of 1070 nm was 49 L / (g·cm), as shown in Table 1 below.

[0065] [Table 1]

[0066] [evaluation] 〔sensitivity〕 The cover sheet was removed from the prepared flexographic printing plate, and then IR writing was performed on the thermal image forming layer (including the barrier layer in Examples 1 and 2) using an ESKO CDI Spark2530. The amount of light used for drawing is 0-5.0 J / cm². 2 The sensitivity was evaluated by changing the settings within a specified range, and the amount of light used for rendering when Dmin after rendering was 0.07 or less was considered the sensitivity. The results are shown in Table 2 below. A smaller value indicates higher sensitivity.

[0067] [White areas in line drawings] The fabricated flexographic printing plate was exposed to light from the substrate side for 15 seconds from a distance of 15 cm using an exposure device consisting of 15 40W fluorescent lamps (back exposure). Subsequently, a negative pattern was formed on the thermal image forming layer of the infrared ablation layer laminate using an ESKO CDI Spark2530. Subsequently, the laminate for the infrared ablation layer was exposed to light from a distance of 15 cm for 8 minutes using the above exposure apparatus (main exposure). After that, the laminate for the infrared ablation layer was peeled off, and the sodium carbonate concentration was 0.5%, and the surfactant (Pionin D-6120, manufactured by Takemoto Oil Co., Ltd.) (surfactant represented by formula (2) above) (A:-CH2CH2- (ethylene group), R 1 The film was developed for 10 minutes in a brush-type wash machine (at a temperature of 50°C) using an aqueous developer solution adjusted to have a hydrogen atom concentration of 1% (n:20). Subsequently, the material was dried with hot air at 60°C until all moisture was removed. After that, the photosensitive resin layer was exposed to the above-mentioned exposure apparatus from a distance of 15 cm for 8 minutes (post-exposure) to produce a flexographic printing plate. Printing was performed using the above flexographic printing plate, and the white areas of 200 μm wide fine lines were evaluated according to the following criteria. The results are shown in Table 2 below. <Evaluation Criteria> A: No white areas. B: White areas can be observed with a magnifying glass, but they are not visible to the naked eye. C: White areas are visible to the naked eye.

[0068] [Manufacturing suitability] The prepared flexographic printing plates were stored for 24 hours at 50°C and 70% relative humidity. The surface of the flexographic printing plates was then observed and evaluated according to the following criteria. The results are shown in Table 2 below. A is preferable. A: No crystal precipitates B: Crystalline precipitate present

[0069] [Table 2]

[0070] From the results shown in Tables 1 and 2 above, it was found that when the content of a compound (UV-absorbing impurity) in the barrier layer that substantially does not absorb in the wavelength region of 900-1200 nm and absorbs in the wavelength region of 300-400 nm was 0.1% by mass relative to the mass of the barrier layer, the sensitivity of the thermal image forming layer was high and good, but when it was made into a flexographic printing plate, white areas in the line drawing occurred (Comparative Example 1). Furthermore, it was found that when a barrier layer without infrared-absorbing dyes was used, the sensitivity of the thermal image forming layer was poor, resulting in white gaps in the line drawings when the print was made into a flexographic plate (Comparative Example 2). Furthermore, it was found that when a thermal image forming layer containing an infrared-absorbing pigment that does not fall under the category of infrared-absorbing dyes was used without a barrier layer, the sensitivity of the thermal image forming layer was further reduced, resulting in white gaps in the line drawings when the print was made into a flexographic plate (Comparative Example 3). In contrast, it was found that when both the barrier layer and the thermal image-forming layer contain infrared-absorbing dyes, and the content of (UV-absorbing impurities) in the barrier layer is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer, the sensitivity of the thermal image-forming layer is high, and the occurrence of white gaps in line drawings can be suppressed when made into a flexographic printing plate (Examples 1-4). In particular, a comparison between Example 1 and Example 3 revealed that when the surface C=C amount of water-dispersible particles contained in the photosensitive resin layer is 21 or less, the occurrence of white gaps in line drawings can be further suppressed when the plate is made into a flexographic printing plate. Furthermore, a comparison between Example 1 and Example 2 showed that in Example 1, where the content of UV-absorbing impurities in the barrier layer was 0.05% by mass or less relative to the mass of the barrier layer, the occurrence of white spots was more suppressed. Furthermore, a comparison between Example 1 and Example 4 showed that Example 4, in which both the barrier layer and the thermal image-forming layer contained a third infrared absorbing dye having absorption at a wavelength of 830 nm, exhibited superior manufacturability. [Explanation of symbols]

[0071] 1 Support 2 Image-forming layer 2a Floor 2b, 2c exposed area 2d weakly exposed area 2e end 3. Barrier layer 3a Residue of the barrier layer 4. Thermal image forming layer 4a Residue of the thermal imaging layer 5 Cover Sheets 10 Flexographic printing plates

Claims

1. A flexographic printing plate having a support, a photosensitive resin layer, a barrier layer, and a thermal image forming layer in this order, The barrier layer contains a first infrared absorbing dye, The thermal image-forming layer contains an ultraviolet absorber and a second infrared absorbing dye. The content of a compound in the barrier layer that has substantially no absorption in the wavelength region of 900 to 1200 nm and absorption in the wavelength region of 300 to 400 nm is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer. A flexographic printing plate master in which both the first infrared absorbing dye and the second infrared absorbing dye are compounds that have absorption at a wavelength of 1070 nm and have a mass extinction coefficient of 50 L / (g·cm) or more at a wavelength of 1070 nm.

2. The flexographic printing plate according to claim 1, wherein both the first infrared absorbing dye and the second infrared absorbing dye are compounds represented by the following formula (1). 【Chemistry 1】 Here, in equation (1) above, R represents a monovalent organic group, and multiple Rs may be the same or different from one another. X － This represents a monovalent anion, and multiple X － They may be the same or different from one another.

3. The flexographic printing plate according to claim 1 or 2, wherein both the barrier layer and the heat-sensitive image-forming layer contain a third infrared-absorbing dye having absorption at a wavelength of 830 nm.

4. The photosensitive resin layer contains a monomer, a polymerization initiator, a base polymer, and water-dispersible particles. The water-dispersible particles have a carbon-carbon double bond, The flexographic printing plate according to any one of claims 1 to 3, wherein the number of carbon-carbon double bonds on the surface of the water-dispersible particles is 21 or less.

5. A flexographic printing plate having a support, a photosensitive resin layer, a barrier layer, and a thermal image forming layer in this order, The barrier layer contains a first infrared absorbing dye, The thermal image-forming layer contains an ultraviolet absorber and a second infrared absorbing dye. The content of a compound in the barrier layer that has substantially no absorption in the wavelength region of 900 to 1200 nm and absorption in the wavelength region of 300 to 400 nm is 0% by mass or more and less than 0.1% by mass relative to the mass of the barrier layer. The photosensitive resin layer contains a monomer, a polymerization initiator, a base polymer, and water-dispersible particles. The water-dispersible particles have a carbon-carbon double bond, A flexographic printing plate master in which the number of carbon-carbon double bonds on the surface of the water-dispersible particles is 21 or less.

6. A method for manufacturing a flexographic printing plate having a non-image portion and an image portion, A mask forming step in which an image is formed on the heat-sensitive image forming layer of a flexographic printing plate according to any one of claims 1 to 4, and a mask is formed, Following the mask formation step, an exposure step is performed in which the photosensitive resin layer of the flexographic printing plate is exposed to the image through the mask. A method for manufacturing a flexographic printing plate, comprising the above exposure step followed by a developing step in which the plate is developed using a developing solution to form a non-image portion and an image portion.

7. The method for manufacturing a flexographic printing plate according to claim 6, wherein the developing solution contains 50% by mass or more of water.

8. The method for producing a flexographic printing plate according to claim 6 or 7, wherein the developing solution contains a surfactant represented by the following formula (2). 【Chemistry 2】 Here, in equation (2) above, A represents an alkylene group with 2 to 4 carbon atoms, and R １ represents a hydrogen atom or substituent, and n represents an integer from 1 to 100. If n is an integer between 2 and 100, the multiple A's may be the same or different from each other.

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