Photosensitive resin printing plate precursor and method for manufacturing printing plate using the same

Abstract

Provided is a photosensitive resin printing plate precursor capable of inhibiting peeling of a photosensitive resin layer. The photosensitive resin printing plate precursor is a photosensitive resin printing plate precursor having at least a support and a photosensitive resin layer containing at least a polymer (A) having an ethylenic double bond, a compound (B) having an ethylenic double bond, and a photopolymerization initiator (C), the photosensitive resin layer having at least a first photosensitive resin layer containing a printing surface and a second photosensitive resin layer containing the inside of the photosensitive resin layer, the ethylenic double bond equivalent F1 (g / eq) of the (A) component in the first photosensitive resin layer being greater than the ethylenic double bond equivalent F2 (g / eq) of the (A) component in the second photosensitive resin layer.

Description

Technical Field

[0001] This invention relates to photosensitive resin printing plate originals and methods for manufacturing printing plates using the same. Background Technology

[0002] As a method for forming relief on a photosensitive resin printing plate, the image portion is selectively cured by irradiating the photosensitive resin layer with ultraviolet light through an image mask or original film, and then removing the uncured portion using a developer.

[0003] As a technique to improve the printing durability of photosensitive resin printing plates with relief, a photosensitive resin printing plate master has been proposed, which is a photosensitive resin printing plate master having at least a support and a photosensitive resin layer. The photosensitive resin layer contains a partially saponified polyvinyl alcohol compound, a polyamide having basic nitrogen, a compound having olefinic double bonds, and a photopolymerization initiator. The photosensitive resin layer includes at least a lower layer and a printing surface layer, which sequentially have the aforementioned support, the aforementioned lower layer, and the aforementioned printing surface layer. Furthermore, as the aforementioned partially saponified polyvinyl alcohol compound, the printing surface layer contains a partially saponified polyvinyl alcohol compound with an average degree of polymerization of 1200 to 2600, and the lower layer contains a partially saponified polyvinyl alcohol compound with an average degree of polymerization of 400 to 800 (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2017 / 038970 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Through the research of the inventors, it has been found that although the photosensitive resin printing plate master described in Patent Document 1 improves printing durability, there is a problem in the plate-making process for forming relief that interlayer delamination can easily occur locally or over the entire surface of the photosensitive resin layer. This is believed to be due to the high crosslinking density of the partially saponified polyvinyl alcohol compounds in the printing surface layer. Therefore, upon exposure, the photocuring of the partially saponified polyvinyl alcohol compounds in the printing surface layer preferentially occurs between each other, making it difficult for the photocuring of the partially saponified polyvinyl alcohol compounds in the lower layer to occur. In this situation, if the developing solution penetrates between the printing surface layer and the lower layer during development, the printing surface layer is easily peeled off into a film, resulting in interlayer delamination.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a photosensitive resin printing plate original capable of suppressing the peeling of the photosensitive resin layer.

[0010] Problem-solving methods

[0011] To achieve the above objectives, the present invention mainly comprises the following contents.

[0012] A photosensitive resin printing plate master, comprising at least a support and a photosensitive resin layer.

[0013] The photosensitive resin layer contains at least:

[0014] Polymers with olefinic double bonds (A), compounds with olefinic double bonds (B), and photopolymerization initiators (C)

[0015] The photosensitive resin layer has at least a first photosensitive resin layer including the printed surface and a second photosensitive resin layer including the interior of the photosensitive resin layer.

[0016] The olefin double bond equivalent F1 (g / eq) of component (A-1) in the first photosensitive resin layer is greater than the olefin double bond equivalent F2 (g / eq) of component (A-2) in the second photosensitive resin layer.

[0017] Invention Effects

[0018] The photosensitive resin printing plate original according to the present invention can suppress the peeling of the photosensitive resin layer. Detailed Implementation

[0019] The photosensitive resin printing plate original of the present invention (hereinafter, sometimes referred to as "printing plate original") has at least a support and a photosensitive resin layer. Here, the photosensitive resin layer refers to a layer containing a polymer (A) having olefinic double bonds, a compound (B) having olefinic double bonds, and a photopolymerization initiator (C), as described later. By having a photosensitive resin layer, for example, ultraviolet light can be irradiated in an image manner to form a desired relief on the support. Two or more photosensitive resin layers may also be present. The support serves to hold the photosensitive resin layer and the relief.

[0020] In the original printing plate of the present invention, the photosensitive resin layer contains at least a polymer (A) having olefinic double bonds (hereinafter sometimes referred to as "(A) component"), a compound (B) having olefinic double bonds (hereinafter sometimes referred to as "(B) component"), and a photopolymerization initiator (C) (hereinafter sometimes referred to as "(C) component"). When the photosensitive resin layer is irradiated with light, free radicals are generated from component (C) in the photosensitive resin layer. The generated free radicals can cause free radical polymerization between component (B) and / or component (A), forming an emboss for obtaining the desired printed image through a cross-linked structure. In addition, component (A), as the matrix of the photosensitive resin layer and the emboss, has the function of imparting structural strength to them. Furthermore, by giving component (A) olefinic double bonds and through free radical polymerization with component (C), photocuring can be further promoted, and image reproducibility can be improved.

[0021] In this invention, component (A) refers to a component having an olefinic double bond and a weight-average molecular weight of 10,000 or more. Here, the weight-average molecular weight of component (A) can be determined by GPC. In this invention, a gel permeation chromatography-multi-angle light scattering spectrophotometer manufactured by Wyatt Technology was used to determine the weight-average molecular weight at a column temperature of 40°C and a flow rate of 0.7 mL / min.

[0022] (A) The component is preferably soluble or dispersible in the solvent used in the developer. Examples of such polymers include styrene-butadiene copolymers, polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, polyurethane, cellulose derivatives, polyesters, polyacrylic acid derivatives, polyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, polyamides, etc. Two or more of these can be used. Among them, polymers that can be dispersed or dissolved in water are preferred from the perspective of helping to reduce environmental impact and reduce the impact on human health. As polymers that can be dispersed or dissolved in water, polymers having hydrophilic groups and polymers whose polymer backbone itself has water swelling or water solubility are preferred. Examples of hydrophilic groups include carboxyl groups, amino groups, hydroxyl groups, phosphate groups, sulfonic acid groups, and their salts. Examples of polymers with hydrophilic groups include carboxylated styrene-butadiene latex, polymers of aliphatic conjugated dienes with carboxyl groups, emulsion polymers of olefinic unsaturated compounds with phosphate and / or carboxyl groups, and polyurethanes containing sulfonic acid groups. Examples of polymers whose main chain itself has water-swellable or water-soluble properties include polyvinyl alcohol, partially saponified polyvinyl alcohol, vinyl alcohol-sodium acrylate copolymers, vinyl alcohol-sodium methacrylate copolymers, polyvinylpyrrolidone, polyether-containing polyamides, polyamides containing tertiary nitrogen atoms, polyethers, cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, starch, starch-sodium polyacrylate grafted compounds, starch-polyacrylonitrile grafted compounds (saponified), cellulose-polyacrylic acid grafted compounds, partially crosslinked sodium polyacrylate, polyethylene glycol, and polyethylene glycol derivatives. Among these, polyvinyl alcohol and partially saponified polyvinyl alcohol are preferred from the perspectives of industrial availability at low cost and further improvement of image reproducibility due to high water solubility. Furthermore, considering the high physical strength, improved printability, and the balance between strength and solvent solubility, polyamides containing tertiary nitrogen atoms are preferred. Partially saponified polyvinyl alcohol is even more preferred.

[0023] From the perspective of further improving image reproducibility, component (A) is preferably found to have an olefinic double bond in its side chain. Examples of groups having an olefinic double bond include vinyl, acryloyl, and methacryloyl groups. Two or more of these groups may be present.

[0024] As a method for introducing olefinic double bonds into the above-mentioned polymers, for example, in the case of partially saponified polyvinyl alcohol, methods such as (1) reacting partially saponified polyvinyl alcohol with an acid anhydride, introducing reactive groups such as carboxyl groups into the polymer side chain starting from the hydroxyl groups of the partially saponified polyvinyl alcohol, and then reacting the reactive groups with unsaturated epoxy compounds; and (2) partially saponifying a copolymer of vinyl acetate with unsaturated carboxylic acids, unsaturated carboxylates, and / or unsaturated carboxylic acid esters, and then reacting the carboxyl groups of the polymer with unsaturated epoxy compounds. In addition, in the case of polyamides, methods such as introducing structures containing tertiary nitrogen atoms, such as piperazine rings, into the polyamide backbone, and then adding olefinic double bonds by quaternizing the nitrogen of glycidyl methacrylate and / or glycidyl acrylate.

[0025] In this invention, the olefinic double bond equivalent of component (A) in the side of the photosensitive resin layer opposite to the support (hereinafter, sometimes referred to as the "printing surface") needs to be greater than the olefinic double bond equivalent of component (A) inside the photosensitive resin layer. As described above, when the crosslinking density of component (A) in the printing surface is high in the photosensitive resin layer, photocuring of the printing surface preferentially occurs upon exposure, making photocuring inside the photosensitive resin layer difficult. In this case, upon development, the developing solution penetrates between the interior of the photosensitive resin layer and the printing surface, making the printing surface easy to peel off. In this invention, by reducing the crosslinking density of the printing surface relative to the interior of the photosensitive resin layer, i.e., making the olefinic double bond equivalent of component (A) in the printing surface greater than the olefinic double bond equivalent of component (A) inside the photosensitive resin layer, photocuring of component (A) can be uniformly carried out from the printing surface to the interior. This is because light irradiated from the printed side attenuates as it passes through the photosensitive resin layer, and free radicals are less likely to be generated inside the layer than on the printed side. Therefore, by increasing the internal cross-linking density, the photosensitive resin layer can be fully photocured inside. This, in turn, can suppress the peeling of the photosensitive resin layer.

[0026] In this invention, the photosensitive resin layer has at least a first photosensitive resin layer (hereinafter, sometimes referred to as "first layer") including the printing surface and a second photosensitive resin layer (hereinafter, sometimes referred to as "second layer") including the interior of the photosensitive resin layer. From the above viewpoint, the olefinic double bond equivalent F1 (g / eq) of component (A) (A-1) in the first layer needs to be greater than the olefinic double bond equivalent F2 (g / eq) of component (A) (A-2) in the second layer. Therefore, peeling of the photosensitive resin layer can be suppressed.

[0027] Here, the olefin double bond equivalent of component (A) is expressed as the polymer molar weight of each mole of olefin double bond in the polymer of component (A). Furthermore, in this invention, the aforementioned printing surface refers to the portion of the photosensitive resin layer from the surface opposite to the support towards the support side to a depth of 5 μm. Additionally, the term "interior of the photosensitive resin layer" refers to the portion from the boundary between the photosensitive resin layer and the support towards the printing surface side, from a depth of 50 μm to a depth of 100 μm. When the structure of component (A) is known, the olefin double bond equivalent can be calculated by dividing the theoretical weight per mole by the number of olefin double bonds contained in one polymer molecule. Furthermore, through... 1 H-NMR analysis of the number of moles of olefinic double bonds in polymers, and the equivalent of olefinic double bonds can be calculated by dividing the weight of the sample used in the analysis by the number of moles of olefinic double bonds detected.

[0028] F1 is preferably 1,000 g / eq or more and 19,000 g / eq or less. By setting F1 to 1,000 g / eq or more, the hardness of the embossed surface of the printing plate can be moderately suppressed, improving print reproducibility. On the other hand, by setting F1 to 19,000 g / eq or less, sufficient photocuring of the printed surface can be achieved, further improving image reproducibility and print durability.

[0029] F2 can be chosen arbitrarily within the range where F1 is greater than F2.

[0030] The ratio of F1 to F2 (F1 / F2) is preferably greater than 1.0 and less than or equal to 5.0. By making F1 / F2 less than or equal to 5.0, the crosslinking density of the printing surface in the photosensitive resin layer can be moderately increased, thereby further improving image reproducibility.

[0031] In this invention, the weight-average molecular weight M1 of A-1 is preferably greater than or equal to the weight-average molecular weight M2 of A-2. In the developing process described later, the uncured portion of the photosensitive resin layer is removed. In this process, there is a tendency that the smaller the weight-average molecular weight of component (A), the easier it is to remove. In particular, when the weight-average molecular weight of component (A) within the photosensitive resin layer is small, it is easy to remove the unexposed portion up to the area close to the support in a short time, thus shortening the developing time. On the other hand, in the printing surface in contact with the developer, a large weight-average molecular weight is preferred from the perspective of improving developer resistance. Therefore, in this invention, the ratio of M1 to M2 (M1 / M2) is preferably 1.0 or more and 6.5 or less. By setting M1 / M2 to 1.0 or more, printing durability can be further improved. On the other hand, by setting M1 / M2 to 6.5 or less, the difference in developability between the first and second layers can be reduced, the developing time can be kept moderately short, and the peeling of the photosensitive resin layer can be further suppressed. Here, M1 and M2, as described above, can be determined by GPC measurement.

[0032] From the perspective of further suppressing the peeling of the photosensitive resin layer and further improving print durability, the weight-average molecular weight M1 of A-1 is preferably 20,000 or more, more preferably 70,000 or more. On the other hand, from the perspective of the processability of the photosensitive resin layer, M1 is preferably 200,000 or less.

[0033] M2 can be arbitrarily chosen in a way that M1 and M2 satisfy the above relationship.

[0034] In this invention, it is preferable that the first layer and the second layer are adjacent to each other. By making the first layer and the second layer directly adjacent to each other, the (A) component (A-2) of the second layer with a high crosslinking density directly forms chemical bonds with the (A) component (A-1) in the first layer containing the printing surface through exposure, thus fixing the first layer more firmly and further suppressing the peeling of the photosensitive resin layer.

[0035] The thickness of the first layer is preferably 5 μm or more, which can suppress defects in the developing process. On the other hand, the thickness of the first layer is preferably 100 μm or less, which makes it easier for the second layer to be fully photocured even when the amount of active light irradiation is low, further improving the adhesion with the second layer and further suppressing interlayer delamination of the photosensitive resin layer.

[0036] The thickness of the second layer is preferably 100 μm or more to ensure the height of the relief on the printing plate and suppress the so-called bottoming-out phenomenon (bottoming-out) where ink adheres to the surface of the support during printing. On the other hand, the thickness of the second layer is preferably 2.0 mm or less to improve print reproducibility.

[0037] The compound (B) having an olefinic double bond refers to a compound having an olefinic double bond and a molecular weight of less than 10,000. The molecular weight of component (B) is preferably less than 2,000.

[0038] As component (B), examples include (meth)acrylates, di(meth)acrylates, propylene glycol diglycidyl ether (meth)acrylate adducts, and tetrahydrofurfuryl (meth)acrylate, as described in International Publication No. 2017 / 038970. Two or more of these may be included. Here, (meth)acrylates are a general term for acrylates and methacrylates, and (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0039] The content of component (B) in the photosensitive resin layer is preferably 5 to 200 parts by mass relative to 100 parts by mass of component (A).

[0040] As the photopolymerization initiator (C), a photopolymerization initiator that generates free radicals through light absorption, self-decomposition, and hydrogen abstraction is preferred. Examples include benzoin alkyl ethers, benzophenones, anthraquinones, benzoyl groups, acetophenones, and diacetyl groups. Two or more of these may be included.

[0041] The content of component (C) in the photosensitive resin layer is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of component (A).

[0042] The photosensitive resin layer may contain compatibility aids, polymerization inhibitors, dyes, pigments, surfactants, defoamers, ultraviolet absorbers, fragrances, etc., together with the aforementioned components (A) to (C) as needed.

[0043] By including a compatibility agent in the photosensitive resin layer, the compatibility of the components constituting the photosensitive resin layer can be improved, the exudation of low molecular weight components can be suppressed, and the softness of the photosensitive resin layer can be improved. Examples of compatibility agents include, for instance, polyols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, and their derivatives. The content of the compatibility agent in the photosensitive resin layer is preferably 30% by mass or less.

[0044] By including a polymerization inhibitor in the photosensitive resin layer, thermal stability can be improved. Examples of polymerization inhibitors include phenols, hydroquinones, catechols, and hydroxylamine derivatives. One or more of these can be included. The preferred content of the polymerization inhibitor in the photosensitive resin layer is 0.001 to 5% by mass.

[0045] Examples of supporting 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.

[0046] Considering processability and flexibility, the thickness of the support is preferably in the range of 100 to 350 μm.

[0047] The support is preferably treated with an easy-to-adhere process to improve its adhesion to the photosensitive resin layer. Examples of easy-to-adhere processing methods include mechanical treatments such as sandblasting, physical treatments such as corona discharge, and chemical treatments such as coating. Among these, from an adhesion perspective, it is preferable to form an easy-to-adhere layer through coating.

[0048] In addition to the aforementioned support and photosensitive resin layer, the printing plate of the present invention may also have a cover film and a thermal mask layer on the photosensitive resin layer as needed.

[0049] By applying a cover film to the photosensitive resin layer, the surface of the photosensitive resin layer can be protected, and the adhesion of foreign matter can be inhibited. The photosensitive resin layer and the cover film can be in direct contact, or there can be one or more anti-adhesion layers between the photosensitive resin layer and the cover film.

[0050] Examples of cover films include plastic sheets made of polyester, polyethylene, polypropylene, etc. From the perspective of processability and flexibility, the thickness of the cover film is preferably 10–150 μm. Furthermore, the surface of the cover film can be roughened to improve adhesion to the original film. Examples of roughening methods include sandblasting, chemical etching, and coating with a coating agent containing matte particles.

[0051] Furthermore, when the printing plate original of the present invention is used in the so-called CTP plate-making method, the printing plate original may also have a thermal mask layer. The CTP plate-making method refers to laser irradiation based on image data controlled by a digital device, where an image mask is formed on-site from the mask layer elements, followed by exposure and development. The thermal mask layer is preferably one that effectively blocks ultraviolet light, absorbs infrared laser light during drawing, and utilizes its heat to cause partial or complete instantaneous sublimation or burning. This creates a difference in optical density between the laser-irradiated and unirradiated areas, allowing it to function similarly to conventional original films. When the printing plate original has a thermal mask layer, an adhesion adjustment layer may be present between the photosensitive resin layer and the thermal mask layer, and a release aid layer may be present between the thermal mask layer and the cover film.

[0052] As a thermal mask layer, adhesion conditioning layer, or peeling aid layer, the layer described in International Publication No. 2017 / 038970 can be cited as an example.

[0053] Next, the method for manufacturing the photosensitive resin composition and the printing plate original will be described using the case where a first layer, a second layer, and a cover film are present on a support as an example.

[0054] For example, components (A), (B), and (C), having a double bond equivalent of F1, and other additives as needed, are heated and dissolved in a solvent to obtain a photosensitive resin composition solution for the first layer. Furthermore, the same operation as for the first layer is performed, except that component (A) having a double bond equivalent of F2 is used, to obtain a photosensitive resin composition solution for the second layer. Examples of solvents include water / alcohol mixtures.

[0055] As needed, a photosensitive resin composition solution for the second layer is cast onto a support having an easy-to-adhere layer and dried to form the second layer. Next, a photosensitive resin composition solution for the first layer is cast onto the second layer and dried to form the first layer. Then, as needed, a cover film coated with an anti-adhesion layer is adhered to the first layer, thereby obtaining the original printing plate.

[0056] Next, a method for manufacturing a printing plate using the original printing plate of the present invention will be described. The manufacturing method of the present invention includes an exposure step in which at least the exposed portions of the photosensitive resin layer of the original printing plate are photocured by irradiating it with ultraviolet light, and a developing step in which at least the uncured portions of the photosensitive resin layer are removed using water and / or an organic solvent.

[0057] In the exposure process, when a cover film is present, a negative or positive original film is adhered to the photosensitive resin layer after the cover film has been peeled off, and ultraviolet light with a wavelength of 300-400 nm is irradiated to photocur the exposed portion of the photosensitive resin layer. For ultraviolet irradiation, preferably, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, UV-LED lamps, etc., are used.

[0058] In the developing process, it is preferable to use a spray developing device or a brush cleaning machine to wash away the uncured portions. Among these, considering the ability to effectively remove the photosensitive resin layer from the uncured portions, developing using a brush cleaning machine is preferred.

[0059] Furthermore, if necessary, a post-exposure process involving ultraviolet light irradiation can be performed after development. This post-exposure process utilizes the reaction of unreacted component (B) to make the relief more robust.

[0060] The printing plate manufactured using the photosensitive resin printing plate master of the present invention can be used for letterpress printing, dry offset printing, flexographic printing, and other applications using rotary printing presses for label printing, intermittent rotary printing presses, etc. Among these, it is preferably used for letterpress printing and dry offset printing. Particularly in dry offset printing, because ink is exchanged between the printing plate and a highly elastic blanket, there is a tendency for fine defects on the surface of the printing plate to be easily transferred to the substrate. The printing plate of the present invention can suppress the peeling of the photosensitive resin layer; therefore, in dry offset printing applications, it can suppress printing defects caused by the peeling of the photosensitive resin layer, and thus can be used more preferably.

[0061] As the object to be printed by dry offset printing, metal cans such as two-piece cans, which are widely used as beverage containers, are preferred. In two-piece metal can printing, millions of cans are typically printed continuously on a hard metal surface, thus requiring high printing durability. According to the present invention, printing defects caused by interlayer delamination of the photosensitive resin layer can be suppressed.

[0062] Example

[0063] The present invention will now be described in detail through examples, but the present invention is not limited to these examples. Furthermore, the evaluation methods in the examples and comparative examples are listed below.

[0064] (1)(A) Equivalent of olefinic double bonds in component A

[0065] A dried coating film with a thickness of 300 μm was formed by bar coating of a solution of component (A) prepared in the various examples and comparative examples. 100 mg of the dried coating film was dissolved in a heavy water / deuterated methanol mixed solvent with sodium 3-(trimethylsilyl)propionate-2,2,3,3d4 added as an internal standard. 1 H-NMR determination was used to determine the molar number of olefinic double bonds. The olefinic double bond equivalent was calculated by dividing the (A) component in the sample used in the analysis by the number of molars of olefinic double bonds detected.

[0066] (2)(A) Weight-average molecular weight of components

[0067] Using a gel permeation chromatography-multi-angle light scattering spectrophotometer manufactured by Wyatt Technology, the dried coating obtained by the method described in (1) above was subjected to GPC determination at a column temperature of 40°C and a flow rate of 0.7 mL / min, and the weight-average molecular weight was determined.

[0068] (3) Peeling off the photosensitive resin layer

[0069] The cover film is peeled off from the printing plate originals obtained through the various embodiments and comparative examples. At this time, only the polyester film is peeled off, and the partially saponified polyvinyl alcohol film with a dry film thickness of 1 μm remains on the photosensitive resin layer.

[0070] A negative containing a 300 μm wide perforated fine line image and a grayscale negative for sensitivity measurement were vacuum-sealed on a photosensitive resin layer with a partially saponified polyvinyl alcohol film. Exposure was performed using a FL20SBL-360 20-watt chemical lamp (manufactured by Mitsubishi Electric Osram Co., Ltd.) at a grayscale sensitivity of 16 ± 1. Then, a brush cleaner was used as the developing apparatus, and development was performed with water at 35°C to 40°C. The plate was dried at 60°C for 10 minutes to obtain a printing plate. The embossed surface of the obtained printing plate was observed using a 25x magnifying glass to evaluate whether the photosensitive resin layer had peeled off. Here, peeling of the photosensitive resin layer includes peeling between the first and second layers. Cases where peeling was not detected were considered as none, and cases where peeling was detected were considered as present, as shown in Tables 1-3.

[0071] (4) Image reproducibility

[0072] The cover film is peeled off from the printing plate originals obtained through the various embodiments and comparative examples. At this time, only the polyester film is peeled off, and the partially saponified polyvinyl alcohol film with a dry film thickness of 1 μm remains on the photosensitive resin layer.

[0073] On a photosensitive resin layer containing a partially saponified polyvinyl alcohol film, a negative film for image reproducibility evaluation and a grayscale negative film for sensitivity measurement, containing a 150-line, 3% dot image, are vacuum-sealed together. Exposure is performed using a FL20SBL-360 20W chemical lamp at a grayscale sensitivity of 16±1 (main exposure). Then, development is performed using a brush cleaner with water at 25°C, followed by drying at 60°C for 10 minutes. Finally, a post-exposure is performed using a FL20SBL-360 20W chemical lamp under the same conditions as the main exposure to obtain a printing plate for image reproducibility evaluation.

[0074] Using a 20x magnifying glass, observe 3% of the 150-line halftone dots formed in a 1cm x 1cm area, and evaluate the reproducibility of the dots according to the following criteria. A score of 4 or higher is considered acceptable.

[0075] 5: No defects were observed.

[0076] 4: Defects were observed in the dots at the outermost periphery of the network.

[0077] 3: Defects were identified in the outermost periphery and the area in the second column from the outermost periphery.

[0078] 2: Defects were observed in the inner region, including the third column from the outermost periphery.

[0079] 1: Defects were observed in more than 20% of the total area of ​​all outlets.

[0080] (5) Printing durability

[0081] Instead of using a negative containing a 12mm diameter hollowed-out circular image, a negative containing a 150-line 3% dot image is used for image reproducibility evaluation. Otherwise, a printing plate with a 12mm diameter solid circular portion is obtained by the method described in (4) above.

[0082] After blowing water vapor onto the surface of the obtained printing plate to create a state prone to cracking, an intermittent rotary printing press LR3 (manufactured by Iwasaki Teikoku Co., Ltd.) was used. The printing pressure adjustment handle was set to 5.05, and the printing speed to 100 prints / minute. The "BEST CURE" (registered trademark) UV161 Blue S (manufactured by T&K TOKA Co., Ltd.) was printed on 90μm thick double-sided coated paper (manufactured by Maru Adhesion Co., Ltd.). The embossed surface of the printing plate after 3000, 5000, 8000, and 10000 prints was observed using a 25x magnifying glass to evaluate the presence or absence of cracks. In each print run, cases where no cracks were observed were designated as A, and cases where cracks were observed were designated as B, as shown in Tables 1-3.

[0083] Next, the methods for preparing the materials used in each embodiment and comparative example will be described.

[0084] <Fabrication of a Support Structure with an Easy-to-Adhede Layer>

[0085] A mixture of 260 parts by weight of "Vilon" (registered trademark) 31SS (toluene solution of unsaturated polyester resin, manufactured by Toyobo Co., Ltd.) and 2 parts by weight of PS-8A (ethyl benzoin ether, manufactured by Wako Pure Chemical Industries, Ltd.) was heated at 70°C for 2 hours, then cooled to 30°C. 7 parts by weight of ethylene glycol diglycidyl ether dimethacrylate were added and mixed for 2 hours. Next, 25 parts by weight of "Coronate" (registered trademark) 3015E (ethyl acetate solution of polyisocyanate resin, manufactured by Toso Co., Ltd.) and 14 parts by weight of EC-1368 (industrial adhesive, manufactured by Sumitomo Silem Co., Ltd.) were added and mixed to obtain an easy-to-adhere coating liquid 1.

[0086] Next, 50 parts by weight of "Gosenol" (registered trademark) KH-17 (polyvinyl alcohol with a saponification degree of 78.5 to 81.5 mol%, manufactured by Mitsubishi Kemica Co., Ltd.) were mixed in a mixed solvent of 200 parts by weight of "Solmix" (registered trademark) H-11 (an alcohol mixture, manufactured by Nippon Alcor Co., Ltd.) and 200 parts by weight of water. After mixing at 70°C for 2 hours, 1.5 parts by weight of "Brenmar" (registered trademark) G (glycidyl methacrylate, manufactured by Nippon Oils & Fats Co., Ltd.) were added, and the mixture was mixed for 1 hour. Add 3 parts by weight of a copolymer (made by Kyoeisha Chemical Co., Ltd.) with a weight ratio of (dimethylaminoethyl methacrylate) / (2-hydroxyethyl methacrylate) of 2 / 1, 5 parts by weight of "Ilugakia" (registered trademark) 651 (benzylmethyl ketal, made by Chiba Gaigye Co., Ltd.), 21 parts by weight of epoxy ester 70PA (acrylate adduct of propylene glycol diglycidyl ether, made by Kyoeisha Chemical Co., Ltd.), and 20 parts by weight of ethylene glycol diglycidyl ether dimethacrylate. Mix for 90 minutes, cool to 50°C, add 0.1 parts by weight of "Megafaq" (registered trademark) F-556 (made by DIC Co., Ltd.), and mix for 30 minutes to obtain coating liquid 2 for easy-to-adhere layer.

[0087] On a 250μm thick "Lumira" (registered trademark) T60 (polyester film, manufactured by Tore Co., Ltd.), the aforementioned easy-to-adhere coating liquid 1 was applied using a bar coater to achieve a dried film thickness of 40μm. The solvent was removed by heating in an oven at 180°C for 3 minutes. On top of this, the aforementioned easy-to-adhere coating liquid 2 was applied using a bar coater to achieve a dried film thickness of 30μm. The film was then heated in an oven at 160°C for 3 minutes to obtain a support with an easy-to-adhere layer.

[0088] <Simulated Version of Covering Film Production>

[0089] On a 100 μm thick "Lumira" (registered trademark) S10 (polyester film, manufactured by Tore Co., Ltd.) roughened to a surface roughness Ra of 0.1 to 0.6 μm, "Gosenol" (registered trademark) AL-06 (partially saponified polyvinyl alcohol with a saponification degree of 91 to 94 mol% and manufactured by Mitsubishi Kemikal Co., Ltd.) was coated with a dry film thickness of 1 μm and dried at 100°C for 25 seconds to obtain a cover film for simulation.

[0090] Example 1

[0091] Partially saponified polyvinyl alcohol "Gosenol" KH-17 (average degree of polymerization 2,200, degree of saponification 80 mol%) manufactured by Mitsubishi Kemica Co., Ltd. was swollen in acetone. 3.8 parts by weight of succinic anhydride were added relative to 100 parts by weight of "Gosenol" KH-17, and the mixture was stirred at 60°C for 6 hours, resulting in the addition of carboxyl groups to the molecular chain of the partially saponified polyvinyl alcohol. The polymer was washed with acetone to remove unreacted succinic anhydride and then dried. 100 parts by weight of the polymer were dissolved at 80°C in 200 parts by weight of a mixed solvent of ethanol / water = 30 / 70 (mass ratio). 6 parts by weight of glycidyl methacrylate were added to this solvent to introduce olefinic double bonds into the partially saponified polyvinyl alcohol, preparing a solution of a-1 as component (A-1). The olefinic double bond equivalent F1 of a-1, determined by the aforementioned method, is 6,234 g / eq, and the weight-average molecular weight M1 is 1.7 × 10⁻⁶. 5 .

[0092] Next, the obtained component (A-1) and the mixed solvent of ethanol / water = 30 / 70 (by weight) were added to a three-necked flask equipped with a stirrer and cooling tube in the amounts listed in Table 1, and heated at 90°C for 2 hours to dissolve. After cooling the resulting mixture to 70°C, the other components listed in Table 1 were added, and the mixture was stirred for 30 minutes to obtain the first layer of solution.

[0093] Next, partially saponified polyvinyl alcohol "Gosenol" KL-05 (average degree of polymerization 500, degree of saponification 80 mol%) manufactured by Mitsubishi Kemica Co., Ltd. was swollen in acetone. 4.2 parts by weight of succinic anhydride were added relative to 100 parts by weight of "Gosenol" KL-05, and the mixture was stirred at 60°C for 6 hours, resulting in the addition of carboxyl groups to the molecular chain of the partially saponified polyvinyl alcohol. The polymer was washed with acetone to remove unreacted succinic anhydride and then dried. 100 parts by weight of the polymer were dissolved at 80°C in 200 parts by weight of a mixed solvent of ethanol / water = 30 / 70 (mass ratio). 6 parts by weight of glycidyl methacrylate were added to this solvent to introduce olefinic double bonds into the partially saponified polyvinyl alcohol, preparing a solution of a-2 as component (A-2). The olefinic double bond equivalent F2 of the obtained a-2 was 5,611 g / eq, and the weight-average molecular weight M2 was 0.4 × 10⁻⁶. 5 .

[0094] Except that (A-2) is used instead of (A-1), the second layer solution is obtained in the same manner as the first layer solution.

[0095] The second layer obtained as described above is cast with a solution onto the easy-to-adhere layer side of the support having the easy-to-adhere layer, and dried at 60°C for 2.5 hours to form the second layer. At this time, the thickness of the plate after drying (polyester film + photosensitive resin layer) is adjusted to 0.90 mm. Then, the first layer is cast with a solution onto the second layer, and dried at 60°C for 1 hour to form the first layer including the printing surface. At this time, the thickness of the plate after drying (polyester film + photosensitive resin layer) is adjusted to 0.95 mm.

[0096] A mixed solvent of water / ethanol = 50 / 50 (mass ratio) was coated onto the resulting photosensitive resin layer, and the cover film used for the simulation plate was pressed onto the surface to obtain the printing plate master. The characteristics of the printing plate were evaluated using the obtained printing plate master by the aforementioned method, and the results are shown in Table 1.

[0097] Example 2

[0098] As the (A-2) component in the second layer solution, a-3 (F2: 2,158 g / eq, M2: 1.7 × 10⁻⁶) was obtained by using "Gosenol" KH-17 and setting the amount of succinic anhydride added to 10.9 parts by mass. 5 In addition, the original printing plate was obtained by the same method as in Example 1.

[0099] Example 3

[0100] Except for using a-2 as the (A-1) component in the first layer solution, the original printing plate was obtained by the same method as in Example 2.

[0101] Example 4

[0102] In addition to using a-4 (F1: 22,444 g / eq, M1: 1.7 × 10⁻⁶) obtained by setting the amount of succinic anhydride added to 0.8 parts by mass, 5 Apart from component (A-1) in the first layer solution, the original printing plate was obtained by the same method as in Example 1.

[0103] Example 5

[0104] In addition to using a-5 (F1: 18,703 g / eq, M1: 1.7 × 10⁻⁶) obtained by setting the amount of succinic anhydride added to 1.3 parts by mass, 5 Apart from component (A-1) in the first layer solution, a photosensitive resin printing plate original was obtained by the same method as in Example 2.

[0105] Example 6

[0106] Ten parts by mass of ε-caprolactam, 90 parts by mass of N-(2-aminoethyl)piperazine and nylon salt of adipic acid, and 100 parts by mass of water were added to a stainless steel autoclave. After purging the internal air with nitrogen, the autoclave was heated at 180°C for 1 hour. The water was then removed to obtain a polyamide resin containing tertiary nitrogen atoms. One hundred parts by mass of this polymer were dissolved at 80°C in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (mass ratio). Two parts by mass of glycidyl methacrylate were added to introduce olefinic double bonds into the polyamide resin containing tertiary nitrogen atoms, preparing a solution of a-6 as component (A-1). The olefinic double bond equivalent F1 of a-6, measured by the aforementioned method, was 3,289 g / eq, and the weight-average molecular weight M1 was 1.2 × 10⁻⁶. 5 .

[0107] In addition, 100 parts by mass of the aforementioned polyamide resin containing tertiary nitrogen atoms were dissolved at 80°C in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (by weight). Three parts by mass of glycidyl methacrylate were added to this solvent to introduce olefinic double bonds into the polyamide resin containing tertiary nitrogen atoms, thus preparing a solution of a-7 as component (A-2). The resulting a-7 had an olefinic double bond equivalent F2 of 1,315 g / eq and a weight-average molecular weight M2 of 1.2 × 10⁻⁶. 5 .

[0108] Except for using (A-1) and (A-2) thus obtained, the original printing plate is obtained by the same method as in Example 1.

[0109] Comparative Example 1

[0110] In addition to using a-8 (F1: 5,611 g / eq, M1: 1.7 × 10⁻⁶) obtained by setting the amount of succinic anhydride added to 4.2 parts by mass, 5 Apart from component (A-1) in the first layer solution, the original printing plate was obtained by the same method as in Example 1.

[0111] Comparative Example 2

[0112] Except for using a-3 as the (A-1) component in the first layer solution, the original printing plate was obtained by the same method as in Example 1.

[0113] Comparative Example 3

[0114] As component (A-2) in the second layer solution, the aforementioned a-5 was used. Otherwise, the original photosensitive resin printing plate was obtained by the same method as in Example 3.

[0115] The composition and evaluation results of the photosensitive resin layers of each embodiment and comparative example are shown in Tables 1 to 3.

[0116] Table 1

[0117]

[0118] Table 2

[0119]

[0120] Table 3

[0121]

Claims

1. A photosensitive resin printing plate master, which is a photosensitive resin printing plate master having at least a support and a photosensitive resin layer. The photosensitive resin layer contains at least: Polymers with olefinic double bonds (A), compounds with olefinic double bonds (B), and photopolymerization initiators (C); The photosensitive resin layer has at least a first photosensitive resin layer including the printed surface and a second photosensitive resin layer including the interior of the photosensitive resin layer; Both the first and second photosensitive resin layers contain a polymer (A) with olefinic double bonds, a compound (B) with olefinic double bonds, and a photopolymerization initiator (C). The olefin double bond equivalent F1 (g / eq) of component (A-1) in the first photosensitive resin layer is greater than the olefin double bond equivalent F2 (g / eq) of component (A-2) in the second photosensitive resin layer.

2. The original photosensitive resin printing plate according to claim 1, wherein F1 is 1,000 (g / eq) or more and 19,000 (g / eq) or less.

3. The original photosensitive resin printing plate according to claim 1 or 2, wherein the ratio of F1 to F2 (F1 / F2) is greater than 1.0 and less than 5.

0.

4. The original photosensitive resin printing plate according to claim 1 or 2, wherein the weight-average molecular weight M1 of (A-1) is greater than the weight-average molecular weight M2 of (A-2).

5. The original photosensitive resin printing plate according to claim 4, wherein M1 is 20,000 or more and 200,000 or less.

6. The original photosensitive resin printing plate according to claim 4, wherein the ratio of M1 to M2 (M1 / M2) is 1.0 or more and 6.5 or less.

7. The original photosensitive resin printing plate according to claim 5, wherein the ratio of M1 to M2 (M1 / M2) is 1.0 or more and 6.5 or less.

8. The original photosensitive resin printing plate according to claim 1 or 2, wherein the first photosensitive resin layer and the second photosensitive resin layer are adjacent.

9. The original photosensitive resin printing plate according to claim 1 or 2, wherein the thickness of the first photosensitive resin layer is 5 μm or more and 100 μm or less.

10. The original photosensitive resin printing plate according to claim 1 or 2, wherein the thickness of the second photosensitive resin layer is more than 100 μm and less than 2.0 mm.

11. The photosensitive resin printing plate original according to claim 1 or 2, wherein the component (A) contains polyvinyl alcohol, partially saponified polyvinyl alcohol and / or polyamide containing tertiary nitrogen atoms.

12. A method for manufacturing a printing plate, comprising the steps of using a photosensitive resin printing plate master as described in any one of claims 1 to 11: An exposure process in which at least the photosensitive resin layer of the original photosensitive resin printing plate is irradiated with ultraviolet light to photocur the exposed portion of the photosensitive resin layer; and The developing process involves at least the use of water and / or organic solvents to remove uncured portions of the photosensitive resin layer.

13. The method for manufacturing a printing plate according to claim 12, wherein in the developing process, the uncured portion is washed away by a brush cleaning machine.

14. The method for manufacturing a printing plate according to claim 12 or 13, wherein the printing plate is a printing plate for dry offset printing.

15. A dry offset printing method, wherein two metal cans are printed using a printing plate obtained by the method of claim 14.

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