Original photosensitive resin printing plate

Abstract

The objective of the present invention is to provide a photosensitive resin printing plate precursor in which an infrared-sensitive layer has excellent scratch resistance. The present invention is a photosensitive resin printing plate precursor having, on a support, a photosensitive resin layer, an intermediate layer, and an infrared-sensitive layer in this order, wherein the intermediate layer contains a polyvinyl alcohol having a saponification degree of 60-100 mol % and an average polymerization degree of 1,200-3,000.

Description

Technical Field

[0001] The present invention relates to a photosensitive resin printing plate original.

Background Art

[0002] CTP (computer to plate) technology, known as digital image forming technology, has become common in the fields of letterpress printing and flexographic printing. In CTP technology, after forming an image mask on the mask layer element of a photosensitive resin printing plate original having a mask layer element by digital data, an active light beam is irradiated through the image mask onto the photosensitive resin layer, and the photosensitive resin layer is partially photocured to form a relief uneven pattern.

[0003] As a photosensitive resin printing plate original suitable for such CTP technology, there is provided a photosensitive resin printing plate original in which at least a photosensitive resin layer (A) containing a resin soluble or dispersible in water and a monomer curable by ultraviolet rays, and a water-insoluble heat-sensitive mask layer (C) containing an infrared absorbing substance are laminated in this order, and the water penetration time of the heat-sensitive mask layer (C) is 50 to 400 seconds (for example, see Patent Document 1), or a water-developable photosensitive relief printing plate original in which at least (A) a support, (B) a photosensitive resin layer, (C) an oxygen-blocking dividing layer, and (D) a water-soluble or water-dispersible heat-sensitive mask layer containing carbon black are sequentially laminated, wherein (B) the photosensitive resin layer contains a synthetic polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, the synthetic polymer compound contains a polyamide or a polyether urethane urea containing a tertiary nitrogen atom, and (C) the oxygen-blocking dividing layer contains a polyvinyl alcohol having a saponification degree of 60 to 85 mol% and a polymerization degree of 200 to 800 (for example, see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the above-described technology, a photosensitive resin printing plate master having an infrared-sensitive layer such as a thermal mask layer requires excellent scratch resistance for the infrared-sensitive layer, as scratches on the infrared-sensitive layer during handling can form unwanted uneven patterns on the photosensitive resin layer.

[0006] The present invention aims to provide a photosensitive resin printing plate master with excellent scratch resistance in the infrared-sensitive layer. [Means for solving the problem]

[0007] The present invention relates to a photosensitive resin printing plate master having a photosensitive resin layer, an intermediate layer, and an infrared-sensitive layer in that order on a support, wherein the intermediate layer contains polyvinyl alcohol with a saponification degree of 60 to 100 mol% and an average degree of polymerization of 1,200 to 3,000, and the infrared-sensitive layer has a saponification degree 84 ~100 mol%, average degree of polymerization 1,300 It contains approximately 3,000 units of polyvinyl alcohol, and the degree of saponification of polyvinyl alcohol in the infrared-sensitive layer is 3 mol% or more greater than the degree of saponification of polyvinyl alcohol in the intermediate layer. The photosensitive resin layer contains polyvinyl alcohol and (meth)acrylate. This is a photosensitive resin printing plate. [Effects of the Invention]

[0008] The photosensitive resin printing plate master of the present invention exhibits excellent scratch resistance in the infrared-sensitive layer. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the present invention will be described in detail below.

[0010] The photosensitive resin printing plate master of the present invention (hereinafter sometimes abbreviated as "printing plate master") has a photosensitive resin layer, an intermediate layer, and an infrared-sensitive layer on a support in this order. The support has the function of holding the photosensitive resin layer in the printing plate master. The photosensitive resin layer has the function of forming a relief pattern corresponding to the image mask by irradiation with active light through the image mask. The infrared-sensitive layer has the function of forming the image mask by partially decomposing and evaporating (ablation) by infrared light. The intermediate layer has the function of adhering the photosensitive resin layer and the infrared-sensitive layer to close contact and suppressing the migration of low molecular weight components from the photosensitive resin layer to the infrared-sensitive layer, thereby improving the scratch resistance of the infrared-sensitive layer. Here, "scratch resistance of the infrared-sensitive layer" means the scratch resistance of the infrared-sensitive layer in the printing plate master unless otherwise specified.

[0011] The printing plate master of the present invention may further have an easy-adhesion layer between the support and the photosensitive resin layer, if necessary, to enhance the adhesion between the support and the photosensitive resin layer. Furthermore, a protective layer may be provided on the infrared-sensitive layer to suppress damage to the infrared-sensitive layer due to external forces, thereby further improving the scratch resistance of the infrared-sensitive layer in the printing plate master.

[0012] The printing plate master of the present invention is characterized by containing polyvinyl alcohol in the intermediate layer with a saponification degree of 60 to 100 mol% and an average degree of polymerization of 1,200 to 3,000. Here, the saponification degree and average degree of polymerization of the polyvinyl alcohol in the present invention are values ​​measured according to JIS K 6726-1994 (Test Method for Polyvinyl Alcohol). Furthermore, when the intermediate layer contains two or more types of polyvinyl alcohol, the saponification degree and average degree of polymerization of the polyvinyl alcohol refer to the saponification degree and average degree of polymerization of the two or more types of polyvinyl alcohol as a whole, respectively.

[0013] By setting the saponification degree of polyvinyl alcohol in the intermediate layer to 60 mol% or higher, solubility in a water-based developer can be improved. In particular, if the infrared-sensitive layer described later can be removed with a water-based developer, the photosensitive resin layer, intermediate layer, and infrared-sensitive layer together can be developed with a water-based developer. A saponification degree of 65 mol% or higher is preferable. On the other hand, a saponification degree of polyvinyl alcohol in the intermediate layer of 97 mol% or lower is preferable, as this can improve adhesion with the photosensitive resin layer.

[0014] Furthermore, if the average degree of polymerization of the polyvinyl alcohol in the intermediate layer is less than 1,200, the intermediate layer is prone to embrittlement due to swelling caused by the migration of low molecular weight components from the photosensitive resin layer. When the intermediate layer becomes embrittlement, low molecular weight components also migrate to the infrared-sensitive layer, reducing the scratch resistance of the infrared-sensitive layer. An average degree of polymerization of 1,400 or higher is preferable. On the other hand, by setting the average degree of polymerization of the polyvinyl alcohol in the intermediate layer to 3,000 or less, the intermediate layer can be easily formed.

[0015] The thickness of the intermediate layer is preferably 0.1 to 3 μm. By setting the thickness of the intermediate layer to 0.1 μm, the scratch resistance of the infrared-sensitive layer can be further improved. A thickness of 0.3 μm or more is more preferable. On the other hand, by setting the thickness of the intermediate layer to 3 μm or less, a relief with a deep depth can be formed for recessed images, improving the reproducibility of images such as cut-out letters. A thickness of 2 μm or less is more preferable. Here, the thickness of the intermediate layer in this invention can be measured by magnifying and observing the cross-section of the printing plate using a transmission electron microscope or a scanning electron microscope. Alternatively, if the coating amount per unit area is known, it can also be calculated from the coating amount and specific gravity.

[0016] Next, the infrared-sensitive layer will be described. The infrared-sensitive layer has the functions of: (1) efficiently absorbing an infrared laser, causing part or all of the layer to evaporate or melt away due to the heat, resulting in a difference in optical density between the irradiated portion and the non-irradiated portion of the layer, that is, a decrease in the optical density of the irradiated portion; and (2) practically blocking ultraviolet light. Here, practically blocking ultraviolet light means that the optical density of the infrared-sensitive layer is 2.0 or more, and more preferably 2.5 or more. The optical density is generally represented by D and is defined by the following formula. D = log 10 (100 / T) = log 10 (I0 / I) Here, T is the transmittance (unit: %), I0 is the incident light intensity during transmittance measurement, and I is the transmitted light intensity.

[0017] The optical density in the present invention refers to a value calculated from the measured value of the transmitted light intensity with the incident light intensity kept constant. The optical density can be measured by a Macbeth transmission densitometer "TR-927" (manufactured by Kollmorgen Instruments Corp.) using an orthochromatic filter.

[0018] The infrared-sensitive layer preferably contains an infrared-absorbing substance. Further, it preferably contains polyvinyl alcohol.

[0019] As the infrared-absorbing substance, a substance having absorption characteristics in the wavelength range of 750 nm to 20,000 nm is preferred. Examples include black pigments such as carbon black, carbon graphite, and cyanine black, inorganic pigments such as manganese oxide, iron oxide, chromium oxide, and copper chromite, and dyes such as phthalocyanine, substituted phthalocyanine derivatives, cyanine dyes, merocyanine dyes, polymethine dyes, and metal thiolate dyes. Two or more of these may be contained. Among these, carbon black is preferred from the viewpoints of ablation efficiency and ultraviolet absorption performance.

[0020] Carbon black preferably has an anionic group. By having an anionic group, the dispersibility of carbon black can be enhanced without using a dispersant. As the anionic group, a sulfo group and a carboxyl group are preferable. The sulfo group has a large dissociation constant in water and has a great effect of suppressing the aggregation of carbon black in the infrared-sensitive layer composition dispersion liquid described later. On the other hand, the carboxyl group can suppress the aggregation of carbon black due to solvent shock, which easily occurs when an organic solvent such as a lower alcohol is added to the infrared-sensitive layer composition dispersion liquid described later, and can suppress coating defects of the infrared-sensitive layer.

[0021] Carbon black having a carboxyl group as an anionic group preferably has a lactone group. The carboxyl group has a low dissociation constant in water and is easily affected by the functional groups and pH of other components. Therefore, carbon black having a carboxyl group tends to aggregate easily. In contrast, by having a lactone group that has hydrophilicity but no ionicity, the lactone group serves as a steric hindrance to the electrostatic interaction with other components and has an effect of suppressing aggregation. Therefore, carbon black having a carboxyl group and a lactone group is excellent in dispersibility in polyvinyl alcohol and can suppress coating defects of the infrared-sensitive layer.

[0022] From the viewpoint of improving the ablation efficiency, the content of the infrared absorption substance in the infrared-sensitive layer is preferably 5% by mass or more in the total solid content. On the other hand, from the viewpoint of further improving the damage resistance of the infrared-sensitive layer, the content of the infrared absorption substance in the infrared-sensitive layer is preferably 80% by mass or less.

[0023] Further, the infrared-sensitive layer in the present invention preferably contains an ultraviolet absorption substance that shields ultraviolet rays. As the ultraviolet absorption substance, a substance having absorption characteristics in the wavelength range of 300 to 400 nm is preferable, and examples thereof include benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, and the like. Two or more of these may be contained.

[0024] The infrared-sensitive layer preferably contains polyvinyl alcohol, which enhances the dispersibility of the aforementioned infrared-absorbing substance and improves the film-forming characteristics of the infrared-sensitive layer. It also improves adhesion to the aforementioned intermediate layer. The polyvinyl alcohol in the infrared-sensitive layer preferably has a saponification degree of 60 to 100 mol% and an average degree of polymerization of 300 to 3,500. The saponification degree and degree of polymerization of the polyvinyl alcohol in the infrared-sensitive layer are measured according to JIS K 6726-1994 (Polyvinyl Alcohol Test Method), the same as for the intermediate layer. Furthermore, when the infrared-sensitive layer contains two or more types of polyvinyl alcohol, the saponification degree and average degree of polymerization of the polyvinyl alcohol refer to the saponification degree and degree of polymerization of the two or more types of polyvinyl alcohol as a whole, respectively.

[0025] By setting the saponification degree of polyvinyl alcohol in the infrared-sensitive layer to 60 mol% or higher, solubility in a water-based developer can be improved, allowing the photosensitive resin layer, intermediate layer, and infrared-sensitive layer to be developed together using a water-based developer. On the other hand, a saponification degree of polyvinyl alcohol in the infrared-sensitive layer of 97 mol% or lower is preferable, as this improves adhesion with the intermediate layer.

[0026] The degree of saponification of polyvinyl alcohol in the infrared-sensitive layer is preferably greater than the degree of saponification of polyvinyl alcohol in the intermediate layer. Compounds having ethylenic double bonds, which are low molecular weight components contained in the photosensitive resin layer described later, are generally highly lipophilic. By using polyvinyl alcohol with a higher degree of saponification than that in the intermediate layer as the polyvinyl alcohol in the infrared-sensitive layer, the migration of these compounds to the infrared-sensitive layer can be further suppressed, and the scratch resistance of the infrared-sensitive layer can be further improved. The difference between the degree of saponification of polyvinyl alcohol in the infrared-sensitive layer and the degree of saponification of polyvinyl alcohol in the intermediate layer is preferably 1 mol% or more, and more preferably 3 mol% or more.

[0027] Furthermore, by setting the average degree of polymerization of the polyvinyl alcohol contained in the infrared-sensitive layer to 300 or higher, the film strength of the infrared-sensitive layer can be improved, and the scratch resistance of the infrared-sensitive layer in the manufacturing process can be enhanced. Here, the scratch resistance of the infrared-sensitive layer in the manufacturing process refers to the scratch resistance of the infrared-sensitive layer as an intermediate in the manufacturing of printing plates (for example, in the case of a printing plate with a protective layer, the infrared-sensitive layer in the laminate of the protective layer / infrared-sensitive layer). This characteristic differs from the scratch resistance of the infrared-sensitive layer in the printing plate as described above, and contributes to improving the yield in the printing plate manufacturing process. An average degree of polymerization of 1,000 or higher is more preferable. On the other hand, by setting the average degree of polymerization to 3,500 or lower, the infrared-sensitive layer can be easily formed. An average degree of polymerization of 2,500 or lower is more preferable.

[0028] From the viewpoint of more easily forming the infrared-sensitive layer, the polyvinyl alcohol content in the infrared-sensitive layer is preferably 10% by mass or more of the total solids. On the other hand, from the viewpoint of improving ablation efficiency, the polyvinyl alcohol content in the infrared-sensitive layer is preferably 80% by mass or less of the total solids.

[0029] The infrared-sensitive layer may contain other polymers, fillers, surfactants, coating aids, etc., to the extent that they do not impair the effects of the present invention. Examples of other polymers include polyacrylic acid, polyester, polyamide, and derivatives thereof. Two or more of these may be included.

[0030] Next, the photosensitive resin layer will be described. Preferably, the photosensitive resin layer contains at least a binder resin, a compound having an ethylenically double bond, and a photopolymerization initiator. When the photosensitive resin layer is irradiated with light such as ultraviolet light in an image-like manner, free radicals are generated from the photopolymerization initiator in the photosensitive resin layer in the exposed area. The generated free radicals induce radical polymerization between compounds having ethylenically double bonds, and a relief can be formed by crosslinking to obtain the desired printed image. If the binder resin has an ethylenically double bond, radical polymerization also occurs between the binder resin and the compound having an ethylenically double bond. This further promotes photocuring and improves the image reproducibility of the printed plate.

[0031] Examples of binder resins include styrene-butadiene copolymer, polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, polyurethane, cellulose derivatives, polyester, polyacrylic acid derivatives, polyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, and polyamide. Two or more of these may be used. From the viewpoint of film formation characteristics, water developability, and adhesion to the intermediate layer, polyvinyl alcohol is preferred.

[0032] The degree of saponification of polyvinyl alcohol contained in the photosensitive resin layer is preferably 60 to 95 mol%. By setting the degree of saponification of polyvinyl alcohol in the photosensitive resin layer to 60 mol% or higher, solubility in water-based developers can be improved. In particular, if the aforementioned infrared-sensitive layer can be removed with water-based developers, the photosensitive resin layer, intermediate layer, and infrared-sensitive layer together can be developed with water-based developers. On the other hand, by setting the degree of saponification of polyvinyl alcohol in the photosensitive resin layer to 95 mol% or lower, compatibility with other components in the photosensitive resin layer can be improved, and migration of low molecular weight components to other layers can be suppressed. The degree of saponification is preferably 90 mol% or lower. The degree of saponification of polyvinyl alcohol in the photosensitive layer is the value measured according to JIS K 6726-1994 (Polyvinyl Alcohol Test Method), the same as for the intermediate layer. Furthermore, when the photosensitive layer contains two or more types of polyvinyl alcohol, the degree of saponification of the polyvinyl alcohol refers to the degree of saponification of the two or more types of polyvinyl alcohol as a whole.

[0033] The weight-average molecular weight of polyvinyl alcohol is preferably between 10,000 and 200,000. Here, the weight-average molecular weight can be determined by GPC measurement. More specifically, it can be measured using a Wyatt Technology gel permeation chromatograph-multiangle light scattering photometer under conditions of column temperature: 40°C and flow rate: 0.7 mL / min, using polyethylene oxide and polyethylene glycol as standard samples.

[0034] In the photosensitive resin layer, the polyvinyl alcohol preferably has an ethylenically active double bond in its side chain. Examples of groups having an ethylenically active double bond include vinyl groups, acryloyl groups, and methacryloyl groups. Two or more of these groups may be present.

[0035] Methods for introducing ethylenically active double bonds into polyvinyl alcohol include, for example, (1) reacting the hydroxyl group of polyvinyl alcohol with an acid anhydride to introduce a reactive group such as a carboxyl group into the polymer side chain starting from the hydroxyl group of polyvinyl alcohol, and then reacting that reactive group with an unsaturated epoxy compound; and (2) partially saponifying a copolymer of vinyl acetate with an unsaturated carboxylic acid, an unsaturated carboxylate salt, and / or an unsaturated carboxylic acid ester, and then reacting the carboxyl group of this polymer with an unsaturated epoxy compound.

[0036] The ethylenically active double bond equivalent of polyvinyl alcohol is preferably between 1,000 g / eq and 19,000 g / eq. By setting the ethylenically active double bond equivalent to 1,000 g / eq or higher, the hardness of the relief surface of the printing plate can be moderately suppressed, further improving print reproducibility. On the other hand, by setting the ethylenically active double bond equivalent to 19,000 g / eq or lower, the photocuring of the printed surface can be sufficiently advanced, improving image reproducibility and print durability. Here, if the structure of polyvinyl alcohol is known, the ethylenically active double bond equivalent can be calculated by dividing the theoretical weight per mole by the number of ethylenically active double bonds contained in one molecule of partially saponified polyvinyl acetate. Furthermore, 1 By analyzing the number of moles of ethylenic double bonds in partially saponified polyvinyl acetate using 1H-NMR, the ethylenic double bond equivalent can be calculated by dividing the weight of the sample used for analysis by the number of moles of ethylenic double bonds detected.

[0037] The polyvinyl alcohol content in the photosensitive resin layer is preferably 30 to 85% by mass.

[0038] The photosensitive resin layer may contain, in addition to the aforementioned polyvinyl alcohol, a binder resin having hydrophilic groups that have excellent compatibility with polyvinyl alcohol, or a binder resin whose polymer main chain is water-swellable or water-soluble. Examples of hydrophilic groups include carboxyl groups, amino groups, hydroxyl groups, phosphate groups, sulfonic acid groups, and their salts. Examples of polymers having hydrophilic groups include carboxylated styrene-butadiene latex, polymers of aliphatic conjugated dienes having carboxyl groups, emulsion polymers of ethylenically unsaturated compounds having phosphate groups and / or carboxyl groups, and sulfonic acid group-containing polyurethanes. Furthermore, polymers whose main chain itself is water-swellable or water-soluble include, for example, vinyl alcohol-sodium acrylate copolymers, vinyl alcohol-sodium methacrylate copolymers, polyvinylpyrrolidone, polyether-containing polyamides, tertiary nitrogen atom-containing polyamides, polyethers, cellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starch, starch-sodium polyacrylate grafts, saponified starch-polyacrylonitrile grafts, cellulose-polyacrylic acid grafts, partially crosslinked sodium polyacrylate, polyethylene glycol, polyethylene glycol derivatives, and the like. Two or more of these may be included. Among these, tertiary nitrogen atom-containing polyamides are preferred because they have high physical strength, can further improve print resistance, and offer a good balance between strength and solubility in solvents.

[0039] Compounds containing an ethylenically double bond refer to compounds that have an ethylenically double bond and a molecular weight of less than 10,000. The molecular weight of compounds containing an ethylenically double bond is preferably 2,000 or less.

[0040] 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 adducts of propylene glycol diglycidyl ether, and tetrahydrofurfuryl(meth)acrylate. Two or more of these may be included. Here, (meth)acrylate is a general term for acrylate and methacrylate, and (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0041] The content of compounds having an ethylenic double bond in the photosensitive resin layer is preferably 10 to 60% by weight.

[0042] Preferably, photopolymerization initiators are those that have the function of generating radicals through self-decomposition or hydrogen abstraction upon light absorption. Examples include benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, and diacetyls. Two or more of these may be included.

[0043] The content of the photopolymerization initiator in the photosensitive resin layer is preferably 0.1 to 10% by mass.

[0044] The photosensitive resin layer may optionally contain compatibility aids, ink-repellent agents, polymerization inhibitors, dyes, pigments, surfactants, defoamers, ultraviolet absorbers, fragrances, and the like.

[0045] By including a compatibility aid in the photosensitive resin layer, the compatibility of the components constituting the photosensitive resin layer can be increased, the bleed-out of low molecular weight components can be suppressed, and the flexibility of the photosensitive resin layer can be improved. Examples of compatibility aids include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, and their derivatives. Two or more of these may be included. The content of the compatibility aid in the photosensitive resin layer is preferably 30% by mass or less.

[0046] By including an ink-repellent agent in the photosensitive resin layer, it is possible to suppress ink from seeping into the recesses of the relief during printing and improve reproducibility. Examples of ink-repellent agents include silicone compounds and fluorine-containing compounds. Two or more of these may be included. The content of the ink-repellent agent in the photosensitive resin layer is preferably 5% by mass or less.

[0047] The thermal stability can be improved by including a polymerization inhibitor in the photosensitive resin layer. Examples of polymerization inhibitors include phenols, hydroquinones, catechols, and hydroxyamine derivatives. Two or more of these may be included. The content of the polymerization inhibitor in the photosensitive resin layer is preferably 0.001 to 5% by mass.

[0048] Next, the support material will be described. Examples of support materials include plastic sheets made of polyester, synthetic rubber sheets made of styrene-butadiene rubber, and metal plates made of steel, stainless steel, aluminum, etc. From the viewpoint of handling and flexibility, the thickness of the support material is preferably in the range of 100 to 350 μm.

[0049] The support is preferably treated for easy adhesion, which can improve adhesion to the relief and floor layers. Examples of methods for easy adhesion include mechanical treatment such as sandblasting, physical treatment such as corona discharge, and chemical treatment such as coating. Among these, from the viewpoint of adhesion, it is preferable to provide an easy-adhesion layer by coating.

[0050] The printing plate master of the present invention may optionally have a protective layer on the infrared-sensitive layer.

[0051] Examples of protective layers include plastic sheets made of polyester, polyethylene, polypropylene, etc. The thickness of the protective layer is preferably 10 to 150 μm from the viewpoint of handling and flexibility.

[0052] Next, the method for manufacturing a printing plate according to the present invention will be described using the example of a case in which a support has a photosensitive resin layer, an intermediate layer, an infrared-sensitive layer, and a protective layer.

[0053] For example, a photosensitive resin composition solution is obtained by heating and dissolving polyvinyl alcohol, a compound component having an ethylenic double bond, and other additives in a solvent. Examples of solvents include water / alcohol mixed solvents.

[0054] A photosensitive resin composition solution is cast onto a support having an easily adhesive layer as needed, and dried to form a photosensitive resin layer. Next, a protective layer with an intermediate layer and an infrared-sensitive layer is brought into close contact with the photosensitive resin layer to obtain a printing plate. For example, the protective layer with the intermediate layer and infrared-sensitive layer can be formed by coating the protective layer with an infrared-sensitive layer composition dispersion containing the aforementioned infrared-sensitive layer components, drying it, and then coating it with an intermediate layer composition solution containing the aforementioned intermediate layer components and drying it.

[0055] A method for manufacturing a printing plate using the printing plate master of the present invention will be described. Preferably, the method includes an exposure step to partially photocure the photosensitive resin layer of the printing plate master, and a developing step to remove the uncured portion of the photosensitive resin layer with a liquid containing water.

[0056] In the exposure process, if a protective layer is present, the printing plate from which the protective layer has been removed is mounted on a digital imager equipped with an infrared laser such as a fiber laser, and an image mask is formed by decomposing and ablating (ablating) the infrared-sensitive layer. Subsequently, it is preferable to irradiate the exposed portion of the photosensitive resin layer with ultraviolet light of a wavelength of 300 to 400 nm through the image mask formed from the infrared-sensitive layer to photo-cure it. Examples of exposure light sources include high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, and UV-LED lamps.

[0057] In the development process, it is preferable to remove the photosensitive resin layer in the unexposed areas using a liquid containing water. Examples of developing equipment include spray-type developing equipment and brush-type washing machines.

[0058] Furthermore, if necessary, a post-exposure step of irradiating with ultraviolet light after development may be included. The post-exposure step can further strengthen the relief by reacting unreacted compounds having ethylenic double bonds.

[0059] The printing plate master of the present invention and the printing plates obtained using it can be used for letterpress printing applications using label printing rotary presses and intermittent rotary presses, dry offset printing applications, flexographic printing applications, and the like. Among these, they can be used more preferably for letterpress printing applications and dry offset printing applications. [Examples]

[0060] The present invention will be described in detail below with reference to examples. Examples 1-8 and 11-12 should be interpreted as comparative examples. Also, "protective layer / thermal mask layer laminate" in Table 3 should be interpreted as "protective layer / infrared layer laminate".

[0061] <Synthesis of polymers for photosensitive resin layers> (Synthesis Example 1) Partially saponified polyvinyl alcohol "Gosenol" (registered trademark) KL-05 (average degree of polymerization 500, degree of saponification 80 mol%, Mw 38,000), manufactured by Mitsubishi Chemical Corporation, was swollen in acetone. 4.2 parts by mass of succinic anhydride were added to 100 parts by mass of "Gosenol" KL-05, and the mixture was stirred at 60°C for 6 hours to add carboxyl groups to the molecular chains. This polymer was washed with acetone to remove unreacted succinic anhydride and then dried. 100 parts by mass of this polymer was dissolved in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (weight ratio) at 80°C. 6 parts by mass of glycidyl methacrylate were added to this solution to introduce ethylenically active double bonds into the partially saponified polyvinyl alcohol, obtaining a solution of polymer A. The ethylenically active double bond equivalent of the obtained polymer A was 5,611 g / eq, and the weight-average molecular weight was 40,000. The weight-average molecular weight was measured using a Wyatt Technology gel permeation chromatograph-multiangle light scattering photometer under the conditions of column temperature: 40°C and flow rate: 0.7 mL / min, using polyethylene oxide and polyethylene glycol as standard samples. The ethylenic double bond equivalent was calculated by dissolving 30 mg of polymer A in 1 ml of heavy water / heavy methanol mixed solvent to which sodium 3-(trimethylsilyl)propionate-2,2,3,3d4 was added as an internal standard. 1 ¹H-NMR measurements were performed to determine the number of moles of ethylenically occurring double bonds. The ethylenically occurring double bond equivalent was calculated by dividing polymer A in the sample used for analysis by the number of moles of detected ethylenically occurring double bonds.

[0062] (Synthesis Example 2) 20 parts by mass of ε-caprolactam, 80 parts by mass of nylon salt of N-(2-aminoethyl)piperazine and adipic acid, and 100 parts by mass of water were placed in a stainless steel autoclave, the internal air was replaced with nitrogen gas, and the mixture was heated at 180°C for 1 hour. Then the water was removed to obtain a water-soluble polyamide resin, a polyamide resin having tertiary amino groups (polymer B). The weight-average molecular weight of the obtained polymer B, measured in the same manner as in Synthesis Example 1, was 72,000.

[0063] <Fabrication of a support having an easily adhering layer> A mixture of 260 parts by mass of "Byron" (registered trademark) 31SS (toluene solution of unsaturated polyester resin, manufactured by Toyobo Co., Ltd.) and 2 parts by mass of PS-8A (benzoin ethyl ether, manufactured by Wako Pure Chemical Industries, Ltd.) was heated at 70°C for 2 hours, then cooled to 30°C, and 7 parts by mass of ethylene glycol diglycidyl ether dimethacrylate was added and mixed for 2 hours. Furthermore, 25 parts by mass of "Coronate" (registered trademark) 3015E (ethyl acetate solution of polyvalent isocyanate resin, manufactured by Tosoh Corporation) and 14 parts by mass of EC-1368 (industrial adhesive, manufactured by Sumitomo 3M Limited) were added and mixed to obtain a coating solution for an easily adhesive layer.

[0064] A coating liquid for an easy-adhesion layer was applied to a 250 μm thick "Lumirror" (registered trademark) T60 (polyester film, manufactured by Toray Industries, Inc.) using a bar coater so that the film thickness after drying would be 30 μm. The solvent was removed by heating in a 180°C oven for 3 minutes to obtain a support having an easy-adhesion layer.

[0065] <Preparation of photosensitive resin layer composition solution> In a three-necked flask fitted with a stirring spatula and a condenser, the polymers shown in Table 1 were added. A mixed solvent consisting of 50 parts by mass of "Solmix" (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) and 50 parts by mass of water was added, and the mixture was heated at 90°C for 2 hours while stirring to dissolve the polymers. After the resulting mixture was cooled to 70°C, the other components shown in Table 1 were added and the mixture was stirred for 30 minutes to obtain a solution of the photosensitive resin layer composition.

[0066] [Table 1]

[0067] <Preparation of infrared-sensitive layer composition dispersion> A 5% by mass aqueous solution of polyvinyl alcohol and a 10% by mass aqueous dispersion of carbon black, as shown in Table 2, were mixed at room temperature with 5 parts by mass of "Solmix" (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) to obtain dispersions of infrared-sensitive layer compositions 1 to 6. The dispersibility of carbon black in the dispersions of infrared-sensitive layer compositions 1 to 6 was good in all cases, and no aggregates larger than 2 μm were observed using a grind gauge.

[0068] [Table 2]

[0069] The evaluation methods in the examples and comparative examples are shown below.

[0070] <Scratch resistance of the infrared-sensitive layer in a protective layer / infrared-sensitive layer laminate> A 25cm x 2cm sample was cut from the infrared-sensitive layer / protective layer laminate, which was an intermediate obtained in each example and comparative example. A carpet material cloth (#4008, manufactured by Shin Nissen Co., Ltd.) was attached to a 500g friction element of a durability tester (RT-300, manufactured by Daiei Kagaku Seiki Co., Ltd.), and the aforementioned sample was rubbed back and forth 20 times. Then, the infrared-sensitive layer on the surface of the sample was observed under magnification using a microscope (KEYENCE VHX2000, 100x lens, transmitted light). The area of ​​each scratch in the observation field was calculated, and the ratio of the total scratch area to the observation field area was calculated. The scratch resistance of the infrared-sensitive layer in the protective layer / infrared-sensitive layer laminate was evaluated according to the following criteria. A: Less than 1% of the scratched area B: Damaged area 1% or more to less than 5% C: Damaged area 5% or more but less than 10% D: Scratch area 10% or more.

[0071] <Number of defects in the infrared-sensitive layer in a protective layer / infrared-sensitive layer laminate> For each example and comparative example, a 30cm x 30cm area of ​​the intermediate infrared-sensitive layer / protective layer laminate was observed using a magnifying glass, and the number of coating defects (repellency defects) of 200μm or larger in the infrared-sensitive layer was counted. A lower number indicates better quality.

[0072] <Scratch resistance of the infrared-sensitive layer in printing plates> The protective layer was peeled off from the printing plates obtained in each example and comparative example, and after being stored for 1 hour in an environment of 25°C and 80RH, a sample measuring 25cm x 2cm was cut out. A carpet material cloth (#4008, manufactured by Shin Nissen Co., Ltd.) was attached to a 500g friction element of a durability tester (RT-300, manufactured by Daiei Kagaku Seiki Co., Ltd.), and the aforementioned sample was rubbed back and forth twice. Then, the infrared-sensitive layer on the surface of the sample was observed under magnification using a microscope (KEYENCE VHX2000, 100x lens, transmitted light). The area of ​​each scratch in the observation field was calculated, and the ratio of the total scratch area to the observation field area was calculated. The scratch resistance of the infrared-sensitive layer on the printing plates was evaluated according to the following criteria, and a score of C or higher was judged as passing. A: Less than 1% of the scratched area B: Damaged area 1% or more but less than 5% C: Damaged area 5% or more but less than 10% D: Scratch area 10% or more.

[0073] <Reproducibility of recessed image> The protective layer was peeled off the printing plate masters obtained in each example and comparative example, and the plates were mounted on the rotating cylindrical drum of a digital imager CDI Spark2530 (manufactured by Esco Graphics Co., Ltd.) with the support side facing inward. 4.0 J / cm 2 Under these conditions, a fiber laser was irradiated to form an image mask containing fine lines with a line width of 300 μm by ablation of the infrared-sensitive layer, and UV-LED exposure was performed through the formed image mask at 22 W for 360 seconds. Subsequently, the image was developed for 100 seconds with water at 25°C to 30°C using a brush-type developing device DX-A3 (manufactured by Takano Machinery Co., Ltd.), dried at 60°C for 10 minutes, and a printing plate was obtained.

[0074] The obtained printed plates were examined using a VK-9500 ultra-deep color 3D shape measuring microscope (manufactured by Keyence Corporation) to magnify and observe recessed images with a line width of 300 μm at a magnification of 25x. The depth was measured at five points, and the average value was calculated. A depth of 50 μm or more was judged to indicate excellent reproducibility of the recessed image. A depth of 70 μm or more was judged to indicate better quality, and a depth of 80 μm or more was judged to indicate extremely good quality.

[0075] [Example 1] A photosensitive resin layer composition solution was cast onto the easily adhesive layer of a support having the easily adhesive layer obtained by the method described above, and dried at 60°C for 2 hours to form a photosensitive resin layer with a thickness of 650 μm. The thickness of the photosensitive resin layer was adjusted by placing a spacer of a predetermined thickness on the support having the easily adhesive layer and scraping off the excess photosensitive resin layer composition solution with a horizontal metal ruler.

[0076] A dispersion of the infrared-sensitive layer composition 1 obtained by the method described above was applied to a 100 μm thick "Lumirror" (registered trademark) S10 (polyester film, manufactured by Toray Industries, Inc.), which served as a protective layer, using a bar coater. The mixture was dried at 120°C for 30 seconds to form an infrared-sensitive layer and obtain a protective layer / infrared-sensitive layer laminate. The thickness of the infrared-sensitive layer was adjusted so that the optical density (transmission mode of the Macbeth transmission densitometer "TR-927" (manufactured by Kollmorgen Instruments Corp.)) using an orthochromatic filter with the protective layer value set to zero was 3.0.

[0077] An intermediate layer composition solution was prepared by dissolving 5 mass of polyvinyl alcohol 1 (JL-18E (manufactured by Nippon Vinegar & Polyvinyl Alcohol Co., Ltd., saponification degree 84 mol%, average degree of polymerization 1,800)) in a mixed solvent of 45 parts by mass of water, 20 parts by mass of methanol, 20 parts by mass of n-propanol, and 10 parts by mass of n-butanol at 70°C. This solution was then applied to the infrared-sensitive layer of a protective layer / infrared-sensitive layer laminate using a bar coater so that the film thickness after drying would be 0.1 μm. The mixture was dried at 120°C for 30 seconds to form an intermediate layer, thereby obtaining an intermediate layer / infrared-sensitive layer / protective layer laminate.

[0078] A mixed solvent of 50 parts by mass of water and 50 parts by mass of ethanol was applied to the photosensitive resin layer formed by the method described above. The intermediate layer / infrared-sensitive layer / protective layer laminate was then laminated so that the intermediate layer was on top of the photosensitive resin layer to obtain a printing plate. The results of the evaluation using the method described above are shown in Table 3.

[0079] [Examples 2-5] A printing plate was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was changed as shown in Table 3. The evaluation results are shown in Table 3.

[0080] [Example 6] A printing plate was obtained in the same manner as in Example 3, except that the polyvinyl alcohol in the intermediate layer was changed as shown in Table 3. The evaluation results are shown in Table 3.

[0081] [Examples 7-9] A printing plate master was obtained in the same manner as in Example 2, except that the infrared-sensitive layer was formed using the infrared-sensitive layer composition shown in Table 3. The evaluation results are shown in Table 3.

[0082] [Example 10] A printing plate master was obtained in the same manner as in Example 9, except that the polyvinyl alcohol in the intermediate layer was changed as shown in Table 3. The evaluation results are shown in Table 3.

[0083] [Example 11] A printing plate master was obtained in the same manner as in Example 10, except that the infrared-sensitive layer was formed using the infrared-sensitive layer composition shown in Table 3. The evaluation results are shown in Table 3.

[0084] [Example 12] A printing plate master was obtained in the same manner as in Example 11, except that the infrared-sensitive layer was formed using the infrared-sensitive layer composition shown in Table 3. The evaluation results are shown in Table 3.

[0085] [Comparative Example 1] A printing plate master was obtained in the same manner as in Example 9, except that an intermediate layer was not formed. The evaluation results are shown in Table 3.

[0086] [Comparative Example 2] A printing plate master was obtained in the same manner as in Example 9, except that the polyvinyl alcohol in the intermediate layer was changed as shown in Table 3. The evaluation results are shown in Table 3.

[0087] [Comparative Example 3] A printing plate master was obtained in the same manner as in Example 2, except that the polyvinyl alcohol in the intermediate layer was changed as shown in Table 3. The evaluation results are shown in Table 3.

[0088] [Table 3]

Claims

1. A photosensitive resin printing plate master having a photosensitive resin layer, an intermediate layer, and an infrared-sensitive layer in that order on a support, wherein the intermediate layer contains polyvinyl alcohol with a saponification degree of 60 to 100 mol% and an average degree of polymerization of 1,200 to 3,000, the infrared-sensitive layer contains polyvinyl alcohol with a saponification degree of 84 to 100 mol% and an average degree of polymerization of 1,300 to 3,000, the saponification degree of polyvinyl alcohol in the infrared-sensitive layer is 3 mol% or more greater than the saponification degree of polyvinyl alcohol in the intermediate layer, and the photosensitive resin layer contains polyvinyl alcohol and (meth)acrylate.

2. The photosensitive resin printing plate master according to claim 1, wherein the thickness of the intermediate layer is 0.1 to 3 μm.

3. The photosensitive resin printing plate master according to claim 1 or 2, wherein the infrared-sensitive layer contains carbon black having carboxyl groups and / or sulfo groups.

4. The photosensitive resin printing plate master according to claim 3, wherein the carbon black has carboxyl groups and lactone groups.

Images