Photosensitive resin relief printing plate master and method for manufacturing relief printing plates using the same

Abstract

To provide a photosensitive resin printing plate precursor which can suppress peeling of a photosensitive resin layer.SOLUTION: A photosensitive resin printing plate precursor has at least a support and a photosensitive resin layer, wherein the photosensitive resin layer contains 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 has at least a first photosensitive resin layer including a printed surface and a second photosensitive resin layer including a photosensitive resin layer therein, and an ethylenic double bond equivalent F1 (g / eq) of the component (A) in the first photosensitive resin layer is larger than an ethylenic double bond equivalent F1 (g / eq) of the component (A) in the second photosensitive resin layer.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] A commonly used method for forming reliefs on photosensitive resin printing plates involves irradiating the photosensitive resin layer with ultraviolet light via an image mask or original film to selectively harden the image portion, and then removing the unhardened portion using a developing solution.

[0003] As a technique to improve the print durability of a photosensitive resin printing plate with a relief formed on it, a photosensitive resin printing plate master (see, for example, Patent Document 1) has been proposed, which has at least a support and a photosensitive resin layer, wherein the photosensitive resin layer contains a partially saponified polyvinyl alcohol compound, a polyamide having basic nitrogen, a compound having an ethylenically double bond, and a photopolymerization initiator, and the photosensitive resin layer includes at least a lower layer and a printing surface layer, and the support, the lower layer and the printing surface layer are in this order, and the partially saponified polyvinyl alcohol compound having an average degree of polymerization of 1200 to 2600 is contained in the printing surface layer, and the lower layer has an average degree of polymerization of 400 to 800. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2017 / 038970 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Through our investigations, we have found that although the photosensitive resin printing plate master described in Patent Document 1 improves print durability, there is a problem in that partial or complete delamination is likely to occur in the photosensitive resin layer during the plate-making process that forms the relief. This is thought to be because the crosslinking density of the partially saponified polyvinyl alcohol compounds in the printing surface layer is high, so upon exposure, photocuring of the partially saponified polyvinyl alcohol compounds in the printing surface layer proceeds preferentially, and photocuring of the partially saponified polyvinyl alcohol compounds in the lower layer does not proceed easily. In this case, when the developing solution penetrates between the printing surface layer and the lower layer during development, the printing surface layer becomes prone to peeling off in a film-like manner, and delamination occurs.

[0006] The present invention was discovered in view of the above circumstances, and aims to provide a photosensitive resin printing plate master that can suppress the peeling of the photosensitive resin layer. [Means for solving the problem]

[0007] To achieve the above objective, the present invention mainly has the following configuration. A photosensitive resin relief printing plate master having at least a support and a photosensitive resin layer, The photosensitive resin layer comprises only a first photosensitive resin layer including the printed surface and a second photosensitive resin layer including the interior of the photosensitive resin layer. The first photosensitive resin layer and the second photosensitive resin layer each contain a polymer (A) having an ethylenically double bond, a compound (B) having an ethylenically double bond, and a photopolymerization initiator (C), The aforementioned component (A) contains polyvinyl alcohol having an ethylenic double bond and / or partially saponified polyvinyl alcohol, A photosensitive resin relief printing plate master, wherein the ethylenically equivalent F1 (g / eq) of component (A-1) in the first photosensitive resin layer is greater than the ethylenically equivalent F2 (g / eq) of component (A-2) in the second photosensitive resin layer, and the weight-average molecular weight M1 of (A-1) is greater than or equal to the weight-average molecular weight M2 of (A-2). [Effects of the Invention]

[0008] According to the photosensitive resin printing plate original of the present invention, peeling of the photosensitive resin layer can be suppressed. [Modes for carrying out the invention]

[0009] The photosensitive resin printing plate master of the present invention (hereinafter sometimes referred to as "printing plate master") comprises at least a support and a photosensitive resin layer. Here, the photosensitive resin layer refers to a layer containing a polymer having an ethylenically double bond (A), a compound having an ethylenically double bond (B), and a photopolymerization initiator (C), which will be described later. By having a photosensitive resin layer, a desired relief can be formed on the support by, for example, irradiating it with ultraviolet light in an image-like manner. There may be two or more photosensitive resin layers. The support has the function of holding the photosensitive resin layer and the relief.

[0010] In the printing plate master of the present invention, the photosensitive resin layer contains at least a polymer (A) having an ethylenically double bond (hereinafter sometimes referred to as "component (A)"), a compound (B) having an ethylenically double bond (hereinafter sometimes referred to as "component (B)"), and a photopolymerization initiator (C) (hereinafter sometimes referred to as "component (C)"). When light is irradiated onto the photosensitive resin layer, free radicals are generated from component (C) in the photosensitive resin layer. The generated free radicals undergo radical polymerization with component (B) and / or component (A), forming a crosslinked structure that can create a relief for obtaining a desired printed image. Furthermore, component (A) acts as a matrix for the photosensitive resin layer and the relief, providing them with structural strength. Moreover, because component (A) has an ethylenically double bond, radical polymerization with component (C) can further accelerate photocuring and improve image reproducibility.

[0011] In this invention, component (A) refers to a substance having an ethylenically 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 measurement. In this invention, the weight-average molecular weight is measured using a gel permeation chromatograph-multiangle light scattering photometer manufactured by Wyatt Technology under conditions of a column temperature of 40°C and a flow rate of 0.7 mL / min.

[0012] Component (A) is preferably soluble or dispersible in the solvent used in the developing solution. 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, polyester, polyacrylic acid derivatives, polyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, and polyamide. Two or more of these may be used. Among these, polymers that are dispersible or soluble in water are preferred because they can contribute to reducing environmental impact and reducing the impact on the human body. Preferred polymers that are dispersible or soluble in water include polymers having hydrophilic groups and polymers whose main chain itself is water-swellable or water-soluble. Examples of hydrophilic groups include carboxyl groups, amino groups, hydroxyl groups, phosphate groups, sulfonic acid groups, and salts thereof. 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. Examples of polymers in which the polymer main chain itself is water-swellable or water-soluble include polyvinyl alcohol, partially saponified polyvinyl alcohol, vinyl alcohol-sodium acrylate copolymer, vinyl alcohol-sodium methacrylate copolymer, polyvinylpyrrolidone, polyether-containing polyamide, tertiary nitrogen atom-containing polyamide, polyether, cellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starch, starch-sodium polyacrylate graft, saponified starch-polyacrylonitrile graft, cellulose-polyacrylic acid graft, partially crosslinked sodium polyacrylate, polyethylene glycol, and polyethylene glycol derivatives. Among these, polyvinyl alcohol and partially saponified polyvinyl alcohol are preferred due to their low industrial cost and high solubility in water, which allows for improved image reproduction.Furthermore, tertiary nitrogen atom-containing polyamides are preferred due to their high physical strength, improved print durability, and balance between strength and solubility in solvents. Partially saponified polyvinyl alcohol is more preferred.

[0013] (A) Component (A) preferably has an ethylenically active double bond in its side chain from the viewpoint of further improving image reproducibility. Examples of groups having an ethylenically active double bond include vinyl groups, acryloyl groups, and methacryloyl groups. It may have two or more of these groups.

[0014] Methods for introducing ethylenically active double bonds into the aforementioned polymers include, for example, in the case of partially saponified polyvinyl alcohol, (1) reacting partially saponified polyvinyl alcohol with an acid anhydride to introduce reactive groups such as carboxyl groups into the polymer side chains starting from the hydroxyl groups of the partially saponified polyvinyl alcohol, and then reacting these reactive groups 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 groups of this polymer with an unsaturated epoxy compound. In the case of polyamides, for example, a method can be used to introduce a structure containing a tertiary nitrogen atom, such as a piperazine ring, into the polyamide skeleton, and then adding an ethylenically active double bond by quaternization of the nitrogen using glycidyl methacrylate and / or glycidyl acrylate.

[0015] In the present invention, it is necessary that the ethylenically double bond equivalent of component (A) on the side of the photosensitive resin layer opposite to the support (hereinafter sometimes referred to as the "printed surface") is greater than the ethylenically double bond equivalent of component (A) inside the photosensitive resin layer. As described above, if the crosslinking density of component (A) on the printed surface in the photosensitive resin layer is high, exposure will preferentially cause photocuring of the printed surface, making it difficult for photocuring to proceed inside the photosensitive resin layer. In this case, development will cause the developer to penetrate between the inside of the photosensitive resin layer and the printed surface, making the printed surface more prone to peeling. In the present invention, by reducing the crosslinking density of the printed surface relative to the inside of the photosensitive resin layer, that is, by making the ethylenically double bond equivalent of component (A) on the printed surface greater than the ethylenically double bond equivalent of component (A) inside the photosensitive resin layer, the photocuring of component (A) can be uniformly advanced from the printed surface to the inside. This is because, while light irradiated from the printed surface is attenuated as it passes through the photosensitive resin layer, and radical generation becomes less likely inside the printed surface, increasing the internal crosslinking density allows for sufficient photocuring of the inside of the photosensitive resin layer. As a result, peeling of the photosensitive resin layer can be suppressed.

[0016] In the present invention, the photosensitive resin layer comprises at least a first photosensitive resin layer including the printed surface (hereinafter sometimes referred to as the "first layer") and a second photosensitive resin layer including the interior of the photosensitive resin layer (hereinafter sometimes referred to as the "second layer"). From the above viewpoint, it is necessary that the ethylenically equivalent F1 (g / eq) of component (A) (A-1) in the first layer is greater than the ethylenically equivalent F2 (g / eq) of component (A) (A-2) in the second layer. This makes it possible to suppress peeling of the photosensitive resin layer.

[0017] Here, the ethylene double bond equivalent of component (A) is represented by the polymer molar weight per mole of ethylene double bonds in the polymer of component (A). In the present invention, the printing surface refers to a portion from the surface on the opposite side of the photosensitive resin layer to the support up to a depth of 5 μm toward the support side. Further, the inside of the photosensitive resin layer refers to a portion from a position at a depth of 50 μm to a position at a depth of 100 μm from the interface between the photosensitive resin layer and the support toward the printing surface side. When the structure of component (A) is known, the ethylene double bond equivalent can be calculated by dividing the theoretically weight per mole by the number of ethylene double bonds contained in one molecule of the polymer. Also, 1 The ethylene double bond equivalent can be calculated by analyzing the molar number of ethylene double bonds in the polymer by 1H-NMR and dividing the sample weight used for the analysis by the detected molar number of ethylene double bonds.

[0018] 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 relief surface of the printing plate can be moderately suppressed, and the printing reproducibility can be improved. On the other hand, by setting F1 to 19,000 g / eq or less, the photocuring of the printing surface can proceed sufficiently, and the image reproducibility and printing resistance can be further improved.

[0019] F2 can be arbitrarily selected within the range where F1 is larger than F2.

[0020] The ratio of F1 to F2 (F1 / F2) is preferably greater than 1.0 and 5.0 or less. By setting F1 / F2 to 5.0 or less, the crosslinking density of the printing surface in the photosensitive resin layer can be moderately increased, and the image reproducibility can be further improved.

[0021] In the present invention, it is preferable that the weight-average molecular weight M1 of A-1 is equal to or greater than the weight-average molecular weight M2 of A-2. In the development process described later, the uncured portion of the photosensitive resin layer is removed. In this process, the smaller the weight-average molecular weight of component (A), the easier it is to remove. In particular, if the weight-average molecular weight of component (A) inside the photosensitive resin layer is small, the unexposed portion can be removed in a short time, even to areas close to the support, and the development time can be shortened. On the other hand, in the printed surface that comes into contact with the developer, it is preferable that the weight-average molecular weight is large from the viewpoint of improving resistance to the developer. For this reason, in the present 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, print 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 layer and the second layer can be reduced, the development time can be kept appropriately short, and peeling of the photosensitive resin layer can be further suppressed. Here, M1 and M2 can be determined by GPC measurement, as mentioned above.

[0022] The weight-average molecular weight M1 of A-1 is preferably 20,000 or more, and more preferably 70,000 or more, from the viewpoint of further suppressing peeling of the photosensitive resin layer and further improving print durability. On the other hand, M1 is preferably 200,000 or less from the viewpoint of processability of the photosensitive resin layer.

[0023] M2 can be arbitrarily selected, preferably such that M1 and M2 satisfy the above relationship.

[0024] In the present invention, it is preferable that the first layer and the second layer are adjacent to each other. When the first layer and the second layer are directly adjacent, the (A) component (A-2) of the second layer, which has a high crosslink density, directly forms a chemical bond with the (A) component (A-1) in the first layer, including the printed surface, upon exposure. This allows the first layer to be fixed more firmly, and the peeling of the photosensitive resin layer can be further suppressed.

[0025] The thickness of the first layer is preferably 5 μm or more, which can suppress chipping during the development process. On the other hand, the thickness of the first layer is preferably 100 μm or less, which makes it easier to sufficiently photocur the second layer even when the amount of active light irradiation is small, further improves adhesion with the second layer, and further suppresses delamination of the photosensitive resin layer.

[0026] The thickness of the second layer is preferably 100 μm or more, which ensures the height of the relief on the printing plate and suppresses the so-called bottoming-out phenomenon where ink adheres to the support surface during printing. On the other hand, the thickness of the second layer is preferably 2.0 mm or less, which can improve print reproducibility.

[0027] Compound (B) having an ethylenically double bond refers to a compound having an ethylenically double bond and a molecular weight of less than 10,000. The molecular weight of component (B) is preferably 2,000 or less.

[0028] (B) Examples of components 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.

[0029] The content of component (B) in the photosensitive resin layer is preferably 5 to 200 parts by mass per 100 parts by mass of component (A).

[0030] Preferably, the photopolymerization initiator (C) is one that has the function of generating radicals by 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.

[0031] The content of component (C) in the photosensitive resin layer is preferably 0.1 to 20 parts by mass per 100 parts by mass of component (A).

[0032] The photosensitive resin layer may, as needed, contain compatibility aids, polymerization inhibitors, dyes, pigments, surfactants, defoamers, ultraviolet absorbers, fragrances, and the like, along with components (A) to (C) above.

[0033] 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. The content of the compatibility aid in the photosensitive resin layer is preferably 30% by mass or less.

[0034] 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. One 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.

[0035] 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.

[0036] From the viewpoint of handling and flexibility, the thickness of the support is preferably in the range of 100 to 350 μm.

[0037] The support is preferably treated for easy adhesion, which can improve adhesion to the photosensitive resin layer. 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.

[0038] In addition to the aforementioned support and photosensitive resin layer, the printing plate master of the present invention may optionally include a cover film or a thermal mask layer on the photosensitive resin layer.

[0039] By having a cover film on the photosensitive resin layer, the surface of the photosensitive resin layer can be protected and the adhesion of foreign matter can be suppressed. The photosensitive resin layer and the cover film may be in direct contact, or there may be one or more layers such as an anti-adhesion layer between the photosensitive resin layer and the cover film.

[0040] Examples of cover films include plastic sheets made of polyester, polyethylene, polypropylene, etc. The thickness of the cover film is preferably 10 to 150 μm from the viewpoint of handling and flexibility. The surface of the cover film may also be roughened to improve adhesion to the original film. Methods for roughening the surface include sandblasting, chemical etching, and coating with a matte particle-containing coating agent.

[0041] Furthermore, when the printing plate master of the present invention is used in a so-called CTP plate-making method in which laser irradiation is performed based on image data controlled by a digital device, an image mask is formed in place from the mask layer elements, and then exposed and developed, the printing plate master may further have a thermal mask layer. Preferably, the thermal mask layer substantially blocks ultraviolet light, absorbs infrared laser light during drawing, and is instantaneously partially or completely sublimated or melted by the heat. This creates a difference in optical density between the laser-irradiated and unirradiated areas, allowing it to perform a function similar to that of conventional original image films. When the printing plate master has a thermal mask layer, an adhesion adjustment layer may be provided between the photosensitive resin layer and the thermal mask layer, and a release assist layer may be provided between the thermal mask layer and the cover film.

[0042] Examples of thermal mask layers, adhesion adjusting layers, and release aid layers include those described in International Publication No. 2017 / 038970.

[0043] Next, a method for manufacturing a photosensitive resin composition and a printing plate will be described using the example of a case in which a first layer, a second layer, and a cover film are provided on a support.

[0044] For example, components (A), (B), and (C), each having a double bond equivalent of F1, and any other additives as needed, are heated and dissolved in a solvent to obtain a photosensitive resin composition solution for the first layer. A photosensitive resin composition solution for the second layer is obtained in the same manner as for the first layer, except that component (A) having a double bond equivalent of F2 is used. Examples of solvents include water / alcohol mixed solvents.

[0045] If necessary, a photosensitive resin composition solution for the second layer is cast onto a support having an easy-adhesion 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. Furthermore, if necessary, a cover film coated with an anti-adhesion layer is adhered to the first layer to obtain a printing plate.

[0046] Next, a method for manufacturing a printing plate using the printing plate master of the present invention will be described. The manufacturing method of the present invention comprises at least an exposure step of irradiating the photosensitive resin layer of the printing plate master with ultraviolet light to photo-cure the exposed portion of the photosensitive resin layer, and a developing step of removing the uncured portion of the photosensitive resin layer using at least water and / or an organic solvent.

[0047] In the exposure process, if a cover film is present, the negative or positive original image film is brought into close contact with the photosensitive resin layer from which the cover film has been removed, and ultraviolet light with a wavelength of 300 to 400 nm is irradiated to photo-cure the exposed portion of the photosensitive resin layer. For ultraviolet irradiation, it is preferable to use, for example, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, or a UV-LED lamp.

[0048] In the development process, it is preferable to dissolve the uncured portion using a spray-type developing device or a brush-type washing machine. Among these, development using a brush-type washing machine is preferred from the viewpoint of efficiently removing the photosensitive resin layer of the uncured portion.

[0049] 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 the unreacted (B) component.

[0050] Printing plates manufactured using the photosensitive resin printing plate master of the present invention can be used for letterpress printing applications using label printing rotary presses and intermittent rotary presses, as well as for dry offset printing and flexographic printing applications. Among these, they can be suitably used for letterpress printing and dry offset printing applications. In particular, in dry offset printing, ink is exchanged between the printing plate and a highly elastic blanket, so fine defects on the surface of the printing plate tend to be easily transferred to the substrate. Since the printing plate of the present invention can suppress the peeling of the photosensitive resin layer, it can suppress printing defects caused by the peeling of the photosensitive resin layer in dry offset printing applications, and is therefore more suitably used in such applications.

[0051] For printing using dry offset printing, metal cans, such as two-piece cans widely used as beverage containers, are preferred. In two-piece metal can printing, since millions of cans are printed continuously on hard metal, high print durability is generally required. The present invention makes it possible to suppress printing defects caused by delamination of the photosensitive resin layer. [Examples]

[0052] The present invention will be specifically illustrated below with reference to examples, but the present invention is not limited to these examples. Example 3 shall be interpreted as a comparative example. The evaluation methods used in the examples and comparative examples are described below.

[0053] (1) Ethylene double bond equivalent of component (A) A dry coating film with a thickness of 300 μm was formed from the solution of component (A) prepared in each example and comparative example by bar coating. 100 mg of the dry coating film was dissolved in a 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 component (A) in the sample used for analysis by the number of moles of detected ethylenically occurring double bonds.

[0054] (2) Weight-average molecular weight of component (A) The weight-average molecular weight of the dried coating obtained by the method described in (1) above was measured using GPC with a Wyatt Technology gel permeation chromatograph-multiangle light scattering photometer under conditions of a column temperature of 40°C and a flow rate of 0.7 mL / min.

[0055] (3) Delamination of the photosensitive resin layer The cover film was peeled off from the printing plates obtained in each example and comparative example. At this time, only the polyester film was peeled off, and the partially saponified polyvinyl alcohol film with a dry thickness of 1 μm remained on the photosensitive resin layer.

[0056] A negative film containing a 300 μm wide line image and a grayscale negative film for sensitivity measurement were vacuum-pressed onto a photosensitive resin layer having a partially saponified polyvinyl alcohol film. Exposure was performed using a FL20SBL-360 20-watt chemical lamp (manufactured by Mitsubishi Electric Osram Corporation) under conditions that resulted in a grayscale sensitivity of 16 ± 1 stops. Subsequently, development was performed using a brush-type washing machine with water at 35°C to 40°C, and the plates were dried at 60°C for 10 minutes to obtain printing plates. The relief surface of the obtained printing plates was observed using a 25x magnifying glass to evaluate whether or not the photosensitive resin layer had peeled off. Here, peeling of the photosensitive resin layer includes delamination between the first and second layers. Tables 1 to 3 show the results, with "none" indicating no peeling and "yes" indicating peeling.

[0057] (4) Image reproducibility The cover film was peeled off from the printing plates obtained in each example and comparative example. At this time, only the polyester film was peeled off, and the partially saponified polyvinyl alcohol film with a dry thickness of 1 μm remained on the photosensitive resin layer.

[0058] A negative film for image reproducibility evaluation and a grayscale negative film for sensitivity measurement, both containing a 150-line, 3% halftone image, were vacuum-pressed onto a photosensitive resin layer having a partially saponified polyvinyl alcohol film. The film was then exposed to a chemical lamp (FL20SBL-360, 20 watts) under conditions that resulted in a grayscale sensitivity of 16 ± 1 stops (main exposure). Subsequently, the film was developed using a brush-type washing machine with 25°C water and dried at 60°C for 10 minutes. Further post-exposure was performed using a chemical lamp (FL20SBL-360, 20 watts) under the same conditions as the main exposure to obtain a printing plate for image reproducibility evaluation.

[0059] Using a 20x magnification magnifying glass, 150-line, 3% halftone dots formed in a 1cm x 1cm area were observed, and the reproducibility of the halftone dots was evaluated according to the following criteria. A score of 4 or higher was considered acceptable. 5: No defects observed 4: Missing dots are observed in the outermost area of ​​the halftone screen. 3: Missing areas are observed in the outermost perimeter and the area of ​​the second row from the outermost perimeter. 2: A chip is observed in the inner area, including the third row from the outermost edge. 1: Missing areas are observed in more than 20% of the total halftone area.

[0060] (5) Durability A printing plate having a 12 mm diameter solid circular area was obtained by the method described in (4) above, except that a negative film containing a 12 mm diameter cutout circular image was used instead of a negative film containing a 150-line 3% halftone image for image reproducibility evaluation.

[0061] The surface of the obtained printing plate was exposed to steam to create a condition conducive to cracking. Then, using an intermittent rotary printing press LR3 (manufactured by Iwasaki Iron Works Co., Ltd.), "BEST CURE" (registered trademark) UV161 indigo S (manufactured by T&K TOKA Co., Ltd.) was printed on 90 μm thick double-sided coated paper (manufactured by Maru Adhesive Co., Ltd.) under the conditions of printing pressure adjustment handle scale: 5.05 and printing speed: 100 shots / minute. The relief 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. For each print count, no cracks were observed (A) and cracks were observed (B) as shown in Tables 1-3.

[0062] Next, the methods for preparing the materials used in each example and comparative example will be described.

[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 coating liquid 1 for easy-adhesion layer.

[0064] Next, 50 parts by mass of “Gosenol” (registered trademark) KH-17 (polyvinyl alcohol with a saponification degree of 78.5 to 81.5 mol%, manufactured by Mitsubishi Chemical Corporation) was mixed with 200 parts by mass of “Solmix” (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) and 200 parts by mass of water in a mixed solvent at 70°C for 2 hours. Then, 1.5 parts by mass of “Bremmer” (registered trademark) G (glycidyl methacrylate, manufactured by Nippon Oil & Fats Co., Ltd.) was added and mixed for 1 hour. To this, 3 parts by mass of a copolymer (manufactured by Kyoeisha Chemical Co., Ltd.) with a weight ratio of (dimethylaminoethyl methacrylate) / (2-hydroxyethyl methacrylate) 2 / 1, 5 parts by mass of "Irgacure" (registered trademark) 651 (benzyl methyl ketal, manufactured by Ciba-Geigy Co., Ltd.), 21 parts by mass of epoxy ester 70PA (acrylic acid adduct of propylene glycol diglycidyl ether, manufactured by Kyoeisha Chemical Co., Ltd.), and 20 parts by mass of ethylene glycol diglycidyl ether dimethacrylate were added and mixed for 90 minutes. After cooling to 50°C, 0.1 parts by mass of "Megafac" (registered trademark) F-556 (manufactured by DIC Corporation) were added and mixed for 30 minutes to obtain coating liquid 2 for easy adhesion layer.

[0065] On a 250 μm thick "Lumirror" (registered trademark) T60 (polyester film, manufactured by Toray Industries, Inc.), the easy-adhesion coating liquid 1 was applied using a bar coater to a dry film thickness of 40 μm, and the solvent was removed by heating in a 180°C oven for 3 minutes. On top of that, the easy-adhesion coating liquid 2 was applied using a bar coater to a dry film thickness of 30 μm, and the material was heated in a 160°C oven for 3 minutes to obtain a support having an easy-adhesion layer.

[0066] <Creating cover films for analog versions> A 100 μm thick "Lumirror" (registered trademark) S10 (polyester film, manufactured by Toray Industries, Inc.) was 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%, manufactured by Mitsubishi Chemical Corporation) was applied to this roughened surface to a dry film thickness of 1 μm. The film was then dried at 100°C for 25 seconds to obtain a cover film for analog plates.

[0067] [Example 1] Partially saponified polyvinyl alcohol "Gosenol" KH-17 (average degree of polymerization 2,200, degree of saponification 80 mol%) manufactured by Mitsubishi Chemical Corporation was swollen in acetone. 3.8 parts by mass of succinic anhydride were added to 100 parts by mass of "Gosenol" KH-17, and the mixture was stirred at 60°C for 6 hours to add carboxyl groups to the molecular chains of the partially saponified polyvinyl alcohol. 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 (mass ratio) at 80°C. 6 parts by mass of glycidyl methacrylate were added to this solution to introduce an ethylenic double bond into the partially saponified polyvinyl alcohol, and a solution of component a-1, which is (A-1), was prepared. The ethylenic double bond equivalent F1 of a-1 measured by the above method was 6,234 g / eq, and the weight-average molecular weight M1 was 1.7 × 10⁻⁶. 5 That was the case.

[0068] Next, the obtained component (A-1) and a mixed solvent of ethanol / water = 30 / 70 (weight ratio) were added in the amounts shown in Table 1 to a three-necked flask equipped with a stirring spatula and a condenser, and heated at 90°C for 2 hours to dissolve. After the resulting mixture was cooled to 70°C, the other components listed in Table 1 were added and stirred for 30 minutes to obtain the first layer solution.

[0069] Next, partially saponified polyvinyl alcohol "Gosenol" KL-05 (average degree of polymerization 500, degree of saponification 80 mol%) 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 of the partially saponified polyvinyl alcohol. 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 (mass ratio) at 80°C. 6 parts by mass of glycidyl methacrylate were added to this solution to introduce an ethylenic double bond into the partially saponified polyvinyl alcohol, preparing a solution of component (A-2), a-2. The obtained a-2 had an ethylenic double bond equivalent F2 of 5,611 g / eq and a weight-average molecular weight M2 of 0.4 × 10⁻⁶. 5 That was the case.

[0070] The second layer solution was obtained in the same manner as the first layer solution, except that (A-2) was used instead of (A-1).

[0071] The second layer solution obtained as described above was cast onto the easy-adhesion layer side of the support having the easy-adhesion layer, and dried at 60°C for 2.5 hours to form the second layer. At this time, the thickness of the plate (polyester film + photosensitive resin layer) after drying was adjusted to 0.90 mm. Subsequently, the first layer solution was cast 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 (polyester film + photosensitive resin layer) after drying was adjusted to 0.95 mm.

[0072] A mixed solvent of water / ethanol = 50 / 50 (mass ratio) was applied to the photosensitive resin layer obtained in this manner, and the cover film for the analog plate was pressed onto the surface to obtain a printing plate master. The results of evaluating the properties of the printing plate using the obtained printing plate master by the above method are shown in Table 1.

[0073] [Example 2] As component (A-2) in the second layer solution, "Gosenol" KH-17 was used, and the amount of succinic anhydride added was 10.9 parts by mass to obtain a-3 (F2: 2,158 g / eq, M2: 1.7 × 10⁻⁶). 5 A printing plate master was obtained in the same manner as in Example 1, except that the ) was used.

[0074] [Example 3] A printing plate master was obtained in the same manner as in Example 2, except that a-2 was used as component (A-1) in the first-stage solution.

[0075] [Example 4] As component (A-1) in the first-stage solution, the amount of succinic anhydride added was 0.8 parts by mass, resulting in a-4 (F1: 22,444 g / eq, M1: 1.7 × 10) 5 A printing plate master was obtained in the same manner as in Example 1, except that the ) was used.

[0076] [Example 5] As component (A-1) in the first-stage solution, the amount of succinic anhydride added was 1.3 parts by mass, resulting in a-5 (F1: 18,703 g / eq, M1: 1.7 × 10) 5 A photosensitive resin printing plate master was obtained in the same manner as in Example 2, except that a different material was used.

[0077] [Example 6] Ten parts by mass of ε-caprolactam, ninety parts by mass of a nylon salt of N-(2-aminoethyl)piperazine and adipic acid, and one hundred parts by mass of water were placed in a stainless steel autoclave. After replacing the internal air with nitrogen gas, the autoclave was heated at 180°C for one hour, and then the water was removed to obtain a polyamide resin having tertiary nitrogen atoms. One hundred parts by mass of this polymer was dissolved in two hundred parts by mass of a mixed solvent of ethanol / water = 30 / 70 (by mass ratio) at 80°C. Two parts by mass of glycidyl methacrylate were added to this solution to introduce an ethylenic double bond into the polyamide resin having tertiary nitrogen atoms, and a solution of component (A-1), a-6, was prepared. The ethylenic double bond equivalent F1 of a-6 measured by the above method was 3,289 g / eq, and the weight-average molecular weight M1 was 1.2 × 10⁻⁶. 5 That was the case.

[0078] Further, 100 parts by mass of the polyamide resin having the tertiary nitrogen atom was dissolved in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (weight ratio) at 80°C. 3 parts by mass of glycidyl methacrylate was added thereto to introduce an ethylenic double bond into the polyamide resin containing the tertiary nitrogen atom, and a solution of a-7 which is the component (A-2) was prepared. The obtained ethylenic double bond equivalent F2 of a-7 was 1,315 g / eq, and the weight average molecular weight M2 was 1.2×10 5 It was thus.

[0079] A printing plate original was obtained in the same manner as in Example 1 except that (A-1) and (A-2) thus obtained were used.

[0080] [Comparative Example 1] As the component (A-1) in the solution for the first layer, a-8 (F1: 5,611 g / eq, M1: 1.7×10 5 ) obtained by setting the addition amount of succinic anhydride to 4.2 parts by mass was used, and a printing plate original was obtained in the same manner as in Example 1.

[0081] [Comparative Example 2] A printing plate original was obtained in the same manner as in Example 1 except that the aforementioned a-3 was used as the component (A-1) in the solution for the first layer.

[0082] [Comparative Example 3] A photosensitive resin printing plate original was obtained in the same manner as in Example 3 except that the aforementioned a-5 was used as the component (A-2) in the solution for the second layer.

[0083] The compositions and evaluation results of the photosensitive resin layers of each Example and Comparative Example are shown in Tables 1 to 3.

[0084]

Table 1

[0085]

Table 2

[0086] Table 3

Claims

1. A photosensitive resin relief printing plate master having at least a support and a photosensitive resin layer, The photosensitive resin layer comprises only a first photosensitive resin layer including the printed surface and a second photosensitive resin layer including the interior of the photosensitive resin layer. The first photosensitive resin layer and the second photosensitive resin layer each contain a polymer (A) having an ethylenically double bond, a compound (B) having an ethylenically double bond, and a photopolymerization initiator (C), The aforementioned component (A) contains polyvinyl alcohol having an ethylenic double bond and / or partially saponified polyvinyl alcohol, A photosensitive resin relief printing plate master, wherein the ethylenically equivalent F1 (g / eq) of component (A) ((A-1)) in the first photosensitive resin layer is greater than the ethylenically equivalent F2 (g / eq) of component (A) ((A-2)) in the second photosensitive resin layer, and the weight-average molecular weight M1 of (A-1) is greater than or equal to the weight-average molecular weight M2 of (A-2).

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

3. The photosensitive resin relief printing plate master according to claim 1 or 2, wherein the ratio of F1 to F2 (F1 / F2) is greater than 1.0 and 5.0 or less.

4. The photosensitive resin relief printing plate according to any one of claims 1 to 3, wherein M1 is 20,000 or more and 200,000 or less.

5. A photosensitive resin relief printing plate according to any one of claims 1 to 4, wherein the ratio of M1 to M2 (M1 / M2) is 1.0 or more and 6.5 or less.

6. A photosensitive resin relief printing plate according to any one of claims 1 to 5, wherein the first photosensitive resin layer and the second photosensitive resin layer are adjacent to each other.

7. A photosensitive resin relief printing plate according to any one of claims 1 to 6, wherein the thickness of the first photosensitive resin layer is 5 μm or more and 100 μm or less.

8. A photosensitive resin relief printing plate according to any one of claims 1 to 7, wherein the thickness of the second photosensitive resin layer is 100 μm or more and 2.0 mm or less.

9. A method for manufacturing a relief printing plate using a photosensitive resin relief printing plate master according to any one of Claims 1 to 8, An exposure step of irradiating the photosensitive resin layer of the photosensitive resin relief printing plate master with ultraviolet light to photo-cure the exposed portion of the photosensitive resin layer, and A method for manufacturing a letterpress printing plate, comprising a developing step of removing uncured portions of the photosensitive resin layer using at least water and / or an organic solvent.

10. The method for manufacturing a relief printing plate according to claim 9, wherein in the developing step, the uncured portion is dissolved by a brush-type washing machine.

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