Photosensitive resin relief printing plate precursor and method for manufacturing a relief printing plate 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 precursor and a method for producing a printing plate using the same. [Background technology]

[0002] A commonly used method for forming a relief on a photosensitive resin printing plate precursor involves irradiating the photosensitive resin layer with ultraviolet light through an image mask or original film to selectively harden the image area, and then removing the unhardened area using a developer.

[0003] As a technique for improving the printing durability of a photosensitive resin printing plate on which a relief is formed, there has been proposed a photosensitive resin printing plate precursor having at least a support and a photosensitive resin layer, the photosensitive resin layer containing a partially saponified polyvinyl alcohol compound, a polyamide having a basic nitrogen, a compound having an ethylenic double bond, and a photopolymerization initiator, the photosensitive resin layer including at least a lower layer and a printing surface layer, the support, the lower layer, and the printing surface layer being in this order, and the partially saponified polyvinyl alcohol compound containing a compound having an average degree of polymerization of 1200 to 2600 in the printing surface layer and a compound having an average degree of polymerization of 400 to 800 in the lower layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 038970 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have found that although the photosensitive resin printing plate precursor described in Patent Document 1 improves printing durability, there is a problem in that delamination easily occurs partially or entirely in the photosensitive resin layer during the platemaking process for forming a relief. This is thought to be because the crosslink density of the partially saponified polyvinyl alcohol compound in the printing surface layer is high, so that photocuring of the partially saponified polyvinyl alcohol compounds in the printing surface layer proceeds preferentially with each other upon exposure, and photocuring of the partially saponified polyvinyl alcohol compound in the lower layer proceeds less easily. In this case, when the developer penetrates between the printing surface layer and the lower layer upon development, the printing surface layer is easily peeled off in a film-like form, causing delamination.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photosensitive resin printing plate precursor capable of suppressing peeling of the photosensitive resin layer. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention mainly has the following configuration. A photosensitive resin printing plate precursor having at least a support and a photosensitive resin layer, The photosensitive resin layer comprises at least The composition contains 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 printing surface and a second photosensitive resin layer including an inside of the photosensitive resin layer; A photosensitive resin printing plate precursor, in which an ethylenic double bond equivalent F1 (g / eq) of the (A) component (A-1) in the first photosensitive resin layer is greater than an ethylenic double bond equivalent F2 (g / eq) of the (A) component (A-2) in the second photosensitive resin layer. Effect of the Invention

[0008] According to the photosensitive resin printing plate precursor of the present invention, peeling of the photosensitive resin layer can be suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The photosensitive resin printing plate precursor of the present invention (hereinafter, may be referred to as "printing plate precursor") has at least a support and a photosensitive resin layer. Here, the photosensitive resin layer refers to a layer containing a polymer (A) having an ethylenic double bond, a compound (B) having an ethylenic double bond, and a photopolymerization initiator (C) described below. By having the photosensitive resin layer, a desired relief can be formed on the support, for example, by irradiating with ultraviolet light in an imagewise manner. Two or more photosensitive resin layers may be provided. The support has the function of holding the photosensitive resin layer and the relief.

[0010] In the printing plate precursor of the present invention, the photosensitive resin layer contains at least a polymer (A) having an ethylenic double bond (hereinafter, sometimes referred to as "component (A)"), a compound (B) having an ethylenic double bond (hereinafter, sometimes referred to as "component (B)"), and a photopolymerization initiator (C) (hereinafter, sometimes referred to as "component (C)"). 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 undergo radical polymerization with component (B) and / or component (A) to form a relief for obtaining a desired printed image by a crosslinked structure. In addition, component (A) has the effect of imparting structural strength to the photosensitive resin layer and the relief as a matrix. Furthermore, since component (A) has an ethylenic double bond, photocuring can be further promoted by radical polymerization with component (C), thereby improving image reproducibility.

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

[0012] The (A) component is preferably soluble or dispersible in a 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, polyester, polyacrylic acid derivatives, polyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, and polyamide. Two or more of these may be used. Among these, water-dispersible or soluble polymers are preferred because they contribute to reducing environmental load and reducing effects on the human body. As water-dispersible or soluble polymers, polymers having hydrophilic groups and polymer main chains themselves having water swelling or water solubility are preferred. Examples of hydrophilic groups include carboxyl groups, amino groups, hydroxyl groups, phosphoric acid groups, sulfonic acid groups, and salts thereof. Examples of the polymer having a hydrophilic group include carboxylated styrene butadiene latex, polymers of aliphatic conjugated dienes having a carboxyl group, emulsion polymers of ethylenically unsaturated compounds having a phosphoric acid group and / or a carboxyl group, polyurethanes containing sulfonic acid groups, etc. Examples of the polymers whose main chain itself is water-swellable or water-soluble include polyvinyl alcohol, partially saponified polyvinyl alcohol, vinyl alcohol-sodium acrylate copolymers, vinyl alcohol-sodium methacrylate copolymers, polyvinylpyrrolidone, polyether-containing polyamides, tertiary nitrogen atom-containing polyamides, polyethers, cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, starch, starch-sodium polyacrylate grafts, saponified starch-polyacrylonitrile grafts, cellulose polyacrylic acid grafts, partially crosslinked sodium polyacrylate, polyethylene glycol, polyethylene glycol derivatives, etc. Among these, polyvinyl alcohol and partially saponified polyvinyl alcohol are preferably used because they are industrially available at low cost and have high solubility in water, thereby enabling image reproducibility to be improved.In addition, a tertiary nitrogen atom-containing polyamide is preferably used from the viewpoints of high physical strength, improved printing durability, and balance between strength and solubility in a solvent. Partially saponified polyvinyl alcohol is more preferable.

[0013] From the viewpoint of further improving image reproducibility, it is preferable that the component (A) has an ethylenic double bond in a side chain. Examples of groups having an ethylenic double bond include a vinyl group, an acryloyl group, and a methacryloyl group. Two or more of these may be included.

[0014] Examples of methods for introducing ethylenic double bonds into the above-mentioned polymers include, in the case of partially saponified polyvinyl alcohol, (1) a method in which partially saponified polyvinyl alcohol is reacted with an acid anhydride, a reactive group such as a carboxyl group is introduced into the polymer side chain starting from the hydroxyl group of the partially saponified polyvinyl alcohol, and an unsaturated epoxy compound is reacted with the reactive group, and (2) a method in which a copolymer of vinyl acetate and an unsaturated carboxylic acid, an unsaturated carboxylate, and / or an unsaturated carboxylate ester is partially saponified, and a carboxyl group of this polymer is reacted with an unsaturated epoxy compound. In addition, in the case of polyamide, a method in which a structure containing a tertiary nitrogen atom such as a piperazine ring is introduced into the polyamide skeleton, and an ethylenic double bond is added by quaternization of the nitrogen using glycidyl methacrylate and / or glycidyl acrylate is included.

[0015] In the present invention, it is necessary that the ethylenic double bond equivalent of the (A) component on the surface of the photosensitive resin layer opposite to the support (hereinafter, sometimes referred to as the "printed surface") is larger than the ethylenic double bond equivalent of the (A) component inside the photosensitive resin layer. As described above, when the crosslink density of the (A) component on the printed surface in the photosensitive resin layer is high, the photocuring of the printed surface proceeds preferentially upon exposure, and the photocuring of the inside of the photosensitive resin layer proceeds less easily. In this case, the developer penetrates between the inside of the photosensitive resin layer and the printed surface upon development, making the printed surface more likely to peel off. In the present invention, the crosslink density of the printed surface is made smaller than that of the inside of the photosensitive resin layer, that is, the ethylenic double bond equivalent of the (A) component on the printed surface is made larger than the ethylenic double bond equivalent of the (A) component inside the photosensitive resin layer, so that the photocuring of the (A) component can proceed uniformly from the printed surface to the inside. This is because the light irradiated from the printed surface side is attenuated when passing through the photosensitive resin layer, and radicals are less likely to be generated inside the printed surface, but by increasing the crosslink density inside, the inside of the photosensitive resin layer can be sufficiently photocured, thereby preventing peeling of the photosensitive resin layer.

[0016] In the present invention, the photosensitive resin layer has at least a first photosensitive resin layer (hereinafter, sometimes referred to as "first layer") including a printing surface and a second photosensitive resin layer (hereinafter, sometimes referred to as "second layer") including the inside of the photosensitive resin layer. From the above viewpoint, it is necessary that the ethylenic double bond equivalent F1 (g / eq) of the (A) component (A-1) in the first layer is larger than the ethylenic double bond equivalent F2 (g / eq) of the (A) component (A-2) in the second layer. This can suppress peeling of the photosensitive resin layer.

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

[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 appropriately suppressed, and printing reproducibility can be improved. On the other hand, by setting F1 to 19,000 g / eq or less, photocuring of the printing surface can be sufficiently promoted, and image reproducibility and printing durability can be further improved.

[0019] F2 can be arbitrarily selected within the range in which F1 is greater than F2.

[0020] The ratio of F1 to F2 (F1 / F2) is preferably greater than 1.0 and equal to or less than 5.0. By making F1 / F2 equal to or less than 5.0, the crosslink density of the printing surface of the photosensitive resin layer can be appropriately increased, and 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 developing step described below, the uncured portion of the photosensitive resin layer is removed. In this step, the smaller the weight average molecular weight of the (A) component, the easier it tends to be removed. In particular, the smaller the weight average molecular weight of the (A) component inside the photosensitive resin layer, the easier it is to remove the unexposed portion in a short time, even in the region close to the support, and the shorter the development time. On the other hand, in the printing surface that contacts the developer, it is preferable that the weight average molecular weight is large from the viewpoint of improving resistance to the developer. Therefore, in the present invention, the ratio of M1 to M2 (M1 / M2) is preferably 1.0 or more and 6.5 or less. By making M1 / M2 1.0 or more, it is possible to further improve the printing durability. On the other hand, by making M1 / M2 6.5 or less, it is possible to reduce the difference in developability between the first layer and the second layer, keep the development time appropriately short, and further suppress peeling of the photosensitive resin layer. Here, M1 and M2 can be determined by GPC measurement as described above.

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

[0023] M2 can be arbitrarily selected, preferably so 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. By directly adjoining the first layer and the second layer, the (A) component (A-2) of the second layer having a high crosslink density forms a direct chemical bond with the (A) component (A-1) in the first layer including the printing surface upon exposure, so that the first layer can be fixed more firmly and peeling of the photosensitive resin layer can be more suppressed.

[0025] The thickness of the first layer is preferably 5 μm or more, which can prevent chipping during the development process, whereas the thickness of the first layer is preferably 100 μm or less, which can facilitate sufficient photocuring of the second layer even when the amount of actinic radiation exposure is small, further improve adhesion with the second layer, and further prevent delamination of the photosensitive resin layer.

[0026] The thickness of the second layer is preferably 100 μm or more, which can ensure the height of the relief of the printing plate and suppress the so-called bottoming out phenomenon in which ink adheres to the surface of the support during printing, while the thickness of the second layer is preferably 2.0 mm or less, which can improve printing reproducibility.

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

[0028] Examples of the (B) component include (meth)acrylates described in International Publication No. 2017 / 038970, glycerol di(meth)acrylate, (meth)acrylic acid adduct of propylene glycol diglycidyl ether, and tetrahydrofurfuryl (meth)acrylate. Two or more of these may be contained. Here, (meth)acrylate is a general term for acrylate and methacrylate, and (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

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

[0030] As the photopolymerization initiator (C), one having a function of generating radicals by self-decomposition or hydrogen abstraction due to light absorption is preferably used. For example, benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, diacetyls, etc. may be mentioned. Two or more of these may be contained.

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

[0032] The photosensitive resin layer may contain, in addition to the components (A) to (C), a compatibility aid, a polymerization inhibitor, a dye, a pigment, a surfactant, an antifoaming agent, an ultraviolet absorbing agent, a fragrance, and the like, if necessary.

[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 bleeding out of low molecular weight components can be suppressed, and the flexibility of the photosensitive resin layer can be improved. Examples of the compatibility aid include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, and derivatives thereof. The content of the compatibility aid in the photosensitive resin layer is preferably 30% by mass or less.

[0034] By including a polymerization inhibitor in the photosensitive resin layer, the thermal stability can be improved. Examples of the polymerization inhibitor include phenols, hydroquinones, catechols, and hydroxylamine 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 the support include a plastic sheet made of polyester or the like, a synthetic rubber sheet made of styrene-butadiene rubber or the like, and a metal plate made of steel, stainless steel, aluminum or the like.

[0036] The thickness of the support is preferably in the range of 100 to 350 μm from the viewpoints of ease of handling and flexibility.

[0037] The support is preferably subjected to an easy-adhesion treatment, so that the adhesion to the photosensitive resin layer can be improved. Examples of the easy-adhesion treatment method 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] The printing plate precursor of the invention may, in addition to the above-mentioned support and photosensitive resin layer, have a cover film or a heat-sensitive mask layer on the photosensitive resin layer, if necessary.

[0039] By providing a cover film on the photosensitive resin layer, the surface of the photosensitive resin layer can be protected and adhesion of foreign matter, etc. The photosensitive resin layer and the cover film may be in direct contact with each other, or one or more layers such as an anti-adhesive layer may be provided between the photosensitive resin layer and the cover film.

[0040] Examples of the cover film 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 be roughened to improve adhesion to the original film. Examples of methods for roughening the surface include sandblasting, chemical etching, and coating with a coating agent containing matte particles.

[0041] In addition, when the printing plate precursor 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 on the spot from the mask layer element, and exposed and developed, the printing plate precursor may further have a heat-sensitive mask layer. The heat-sensitive mask layer is preferably one that effectively blocks ultraviolet light, absorbs infrared laser light during drawing, and is instantly sublimated or ablated in part or in whole by the heat. This creates a difference in optical density between the laser irradiated part and the non-irradiated part, allowing it to function similarly to a conventional original film. When the printing plate precursor has a heat-sensitive mask layer, it may have an adhesion adjustment layer between the photosensitive resin layer and the heat-sensitive mask layer, and may have a peeling auxiliary layer between the heat-sensitive mask layer and the cover film.

[0042] Examples of the heat-sensitive mask layer, adhesion adjustment layer, and peeling auxiliary layer include those described in WO 2017 / 038970.

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

[0044] For example, the (A), (B), and (C) components each having a double bond equivalent of F1, and other additives as necessary, are dissolved in a solvent under heating 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 the (A) component having a double bond equivalent of F2 is used. Examples of the solvent include a water / alcohol mixed solvent.

[0045] A solution of the photosensitive resin composition for the second layer is cast onto a support having an easy-adhesion layer as required, and dried to form a second layer. Next, a solution of the photosensitive resin composition for the first layer is cast onto the second layer, and dried to form a first layer. Furthermore, a cover film coated with an anti-tack layer as required is adhered onto the first layer to obtain a printing plate precursor.

[0046] Next, a method for producing a printing plate using the printing plate precursor of the present invention will be described. The production method of the present invention includes an exposure step of irradiating at least the photosensitive resin layer of the printing plate precursor with ultraviolet light to photocure the exposed areas of the photosensitive resin layer, and a development step of removing the uncured areas of the photosensitive resin layer using at least water and / or an organic solvent.

[0047] In the exposure step, a negative or positive original film is attached to the photosensitive resin layer from which a cover film (if any) is peeled off, and the exposed portion of the photosensitive resin layer is photocured by irradiating with ultraviolet light having a wavelength of 300 to 400 nm. For ultraviolet light 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, a UV-LED lamp, or the like.

[0048] In the development step, 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 preferable from the viewpoint of efficiently removing the uncured portion of the photosensitive resin layer.

[0049] Furthermore, if necessary, a post-exposure step of irradiating with ultraviolet light after development may be carried out, which makes it possible to further strengthen the relief by reaction of unreacted component (B) through the post-exposure step.

[0050] A printing plate manufactured using the photosensitive resin printing plate precursor of the present invention can be used for letterpress printing using a rotary press for label printing or an intermittent rotary press, dry offset printing, flexographic printing, and the like. Among these, it can be suitably used for letterpress printing and dry offset printing. In particular, in dry offset printing, since ink is transferred between the printing plate and a highly elastic blanket, minute defects on the surface of the printing plate tend to be easily transferred to the printed material. Since the printing plate of the present invention can suppress peeling of the photosensitive resin layer, it can be more suitably used in dry offset printing because printing defects caused by peeling of the photosensitive resin layer can be suppressed.

[0051] As an object to be printed by dry offset printing, metal cans such as two-piece cans that are widely used as beverage containers are preferable. In two-piece metal can printing, since several million cans are generally printed continuously on hard metal, high printing durability is required. According to the present invention, printing defects caused by delamination of the photosensitive resin layer can be suppressed. EXAMPLES

[0052] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Evaluation methods in the examples and comparative examples are described below.

[0053] (1) Ethylenic double bond equivalent of component (A) A dry coating film having a thickness of 300 μm was formed by bar coating from the solution of component (A) prepared in each Example and Comparative Example. 100 mg of the dry coating film was dissolved in a heavy water / heavy methanol mixed solvent containing sodium 3-(trimethylsilyl)propionate-2,2,3,3d4 as an internal standard. 1 H-NMR measurement was performed to measure the number of moles of ethylenic double bonds. The ethylenic double bond equivalent was calculated by dividing the component (A) in the sample used for the analysis by the number of moles of the detected ethylenic double bonds.

[0054] (2) Weight average molecular weight of component (A) The dried coating film obtained by the method described in (1) above was subjected to GPC measurement 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 to measure the weight average molecular weight.

[0055] (3) Photosensitive resin layer peeling The cover film was peeled off from the printing plate precursor obtained in each of the Examples and Comparative Examples. At this time, only the polyester film was peeled off, and the partially saponified polyvinyl alcohol film having a dry thickness of 1 μm remained on the photosensitive resin layer.

[0056] A negative film containing a 300 μm wide cut-out thin line image and a grayscale negative film for sensitivity measurement were vacuum-attached to the photosensitive resin layer having a partially saponified polyvinyl alcohol film, and exposed to light using a chemical lamp FL20SBL-360 20 watts (manufactured by Mitsubishi Electric Osram Co., Ltd.) under conditions of a grayscale sensitivity of 16±1 step. Thereafter, the plate was developed with water at 35° C. to 40° C. using a brush-type washing machine as a developing device, and dried at 60° C. for 10 minutes to obtain a printing plate. The relief surface of the obtained printing plate was observed using a 25x magnifying glass to evaluate the presence or absence of peeling of the photosensitive resin layer. Here, peeling of the photosensitive resin layer includes peeling between the first layer and the second layer. Tables 1 to 3 show cases where no peeling was observed as "no" and cases where peeling was observed as "present."

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

[0058] A negative film for evaluating image reproducibility containing a 150 line 3% halftone dot image and a grayscale negative film for measuring sensitivity were vacuum-contacted onto the photosensitive resin layer having a partially saponified polyvinyl alcohol film, and exposed using a chemical lamp FL20SBL-360 20 watts under conditions that resulted in a grayscale sensitivity of 16±1 stops (main exposure). After that, the plate was developed with water at 25°C using a brush-type washing machine as the developing device, and dried at 60°C for 10 minutes. Furthermore, a 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 evaluating image reproducibility.

[0059] Using a 20x magnifying glass, a 150 line 3% halftone dot formed in an area of ​​1cm x 1cm was observed, and the reproducibility of the halftone dot was evaluated according to the following criteria. A score of 4 points or more was considered to be acceptable. 5: No chipping observed 4: Missing dots are found in the outermost area 3: Chips are found in the outermost area and the area two rows from the outermost area. 2: Chips are found in the inner area including the third row from the outermost circumference. 1: Missing areas are found in 20% or more of the total halftone dot area.

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

[0061] The surface of the obtained printing plate was exposed to water vapor to make it prone to cracking, and then, using an intermittent rotary printing machine 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 Bonding Co., Ltd.) under the conditions of a scale of the printing pressure adjustment handle: 5.05 and a printing speed: 100 shots / min. 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 number of prints, the case where no cracks were observed was rated A, and the case where cracks were observed was rated B, as shown in Tables 1 to 3.

[0062] Next, the methods for producing the materials used in the examples and comparative examples will be described.

[0063] <Preparation of a support having an easy-adhesion layer> A mixture of 260 parts by mass of "Vylon" (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, 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 polyisocyanate resin, manufactured by Tosoh Co., Ltd.) and 14 parts by mass of EC-1368 (industrial adhesive, manufactured by Sumitomo 3M Co., Ltd.) were added and mixed to obtain coating solution 1 for easy adhesion layer.

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

[0065] The above-mentioned coating solution 1 for easy adhesion layer was applied to a 250 μm-thick "Lumirror" (registered trademark) T60 (polyester film, manufactured by Toray Industries, Inc.) using a bar coater so that the film thickness after drying would be 40 μm, and the solvent was removed by heating for 3 minutes in an oven at 180° C. The above-mentioned coating solution 2 for easy adhesion layer was applied thereon using a bar coater so that the film thickness after drying would be 30 μm, and the coating was heated for 3 minutes in an oven at 160° C. to obtain a support having an easy adhesion layer.

[0066] <Creating cover film for analog version> "GOHSENOL" (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 a 100 μm-thick "Lumilar" (registered trademark) S10 (polyester film, manufactured by Toray Industries, Inc.) that had been roughened to a surface roughness Ra of 0.1 to 0.6 μm, to a dry film thickness of 1 μm, and dried at 100° C. for 25 seconds to obtain a cover film for analog plates.

[0067] [Example 1] Partially saponified polyvinyl alcohol "GOHSENOL" KH-17 (average degree of polymerization 2,200, degree of saponification 80 mol%) manufactured by Mitsubishi Chemical Corporation was swollen in acetone, and 3.8 parts by mass of succinic anhydride were added to 100 parts by mass of "GOHSENOL" KH-17, and the mixture was stirred at 60°C for 6 hours to add a carboxyl group 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 mass of this polymer was dissolved at 80°C in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (mass ratio). 6 parts by mass of glycidyl methacrylate were added thereto to introduce an ethylenic double bond into the partially saponified polyvinyl alcohol, and a solution of a-1, which is the component (A-1), was prepared. The ethylenic double bond equivalent F1 of a-1 measured by the above-mentioned method was 6,234 g / eq, and the weight average molecular weight M1 was 1.7 × 10 5 It was.

[0068] Next, the obtained (A-1) component 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 cooling tube, and dissolved by heating at 90 ° C. for 2 hours. The obtained mixture was cooled to 70 ° C., and the other components shown in Table 1 were added and stirred for 30 minutes to obtain a solution for the first layer.

[0069] Next, partially saponified polyvinyl alcohol "GOHSENOL" KL-05 (average polymerization degree 500, saponification degree 80 mol%) manufactured by Mitsubishi Chemical Corporation was swollen in acetone, and 4.2 parts by mass of succinic anhydride were added to 100 parts by mass of "GOHSENOL" KL-05, and the mixture was stirred at 60°C for 6 hours to add a carboxyl group 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 mass of this polymer was dissolved at 80°C in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (mass ratio). 6 parts by mass of glycidyl methacrylate were added thereto to introduce an ethylenic double bond into the partially saponified polyvinyl alcohol, and a solution of a-2, which is the component (A-2), was prepared. The ethylenic 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 5 It was.

[0070] A second layer solution was obtained in the same manner as in the preparation of 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 adhesive layer side of the support having the adhesive layer, and dried at 60°C for 2.5 hours to form a second layer. At this time, the plate thickness after drying (polyester film + photosensitive resin layer) was adjusted to 0.90 mm. Thereafter, the first layer solution was cast onto the second layer, and dried at 60°C for 1 hour to form a first layer including a printing surface. At this time, the plate thickness after drying (polyester film + photosensitive resin layer) was adjusted to 0.95 mm.

[0072] A mixed solvent of water / ethanol = 50 / 50 (mass ratio) was applied onto the photosensitive resin layer thus obtained, and the cover film for the analog plate was pressed onto the surface to obtain a printing plate precursor. The printing plate characteristics of the obtained printing plate precursor were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0073] [Example 2] As the (A-2) component in the second layer solution, "GOHSENOL" KH-17 was used, and the amount of succinic anhydride added was 10.9 parts by mass. 5 A printing plate precursor was obtained in the same manner as in Example 1, except that the above-mentioned ink was used instead of the ink.

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

[0075] [Example 4] As the component (A-1) in the first layer solution, a-4 (F1: 22,444 g / eq, M1: 1.7×10 5 A printing plate precursor was obtained in the same manner as in Example 1, except that the above-mentioned ink was used instead of the ink.

[0076] [Example 5] As the component (A-1) in the first layer solution, a-5 (F1: 18,703 g / eq, M1: 1.7×10 5 A photosensitive resin printing plate precursor was obtained in the same manner as in Example 2, except that the above-mentioned mixture was used.

[0077] [Example 6] 10 parts by mass of ε-caprolactam, 90 parts by mass of nylon salt of N-(2-aminoethyl)piperazine and adipic acid, and 100 parts by mass of water were placed in a stainless steel autoclave, and after replacing the air inside with nitrogen gas, the autoclave was heated at 180°C for 1 hour, and then the water was removed to obtain a polyamide resin having tertiary nitrogen atoms. 100 parts by mass of this polymer was dissolved at 80°C in 200 parts by mass of a mixed solvent of ethanol / water = 30 / 70 (mass ratio). 2 parts by mass of glycidyl methacrylate were added to this solution to introduce ethylenic double bonds into the polyamide resin having tertiary nitrogen atoms, and a solution of a-6, which is component (A-1), was prepared. The ethylenic double bond equivalent F1 of a-6 measured by the above-mentioned method was 3,289 g / eq, and the weight average molecular weight M1 was 1.2 × 10 5 It was.

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

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

[0080] [Comparative Example 1] As the component (A-1) in the first layer solution, a-8 (F1: 5,611 g / eq, M1: 1.7 × 10 5 A printing plate precursor was obtained in the same manner as in Example 1, except that the above-mentioned ink was used instead of the ink.

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

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

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

[0084] [Table 1]

[0085] [Table 2]

[0086]

Table 3

Claims

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

2. 2. The photosensitive resin letterpress printing plate precursor according to claim 1, wherein F1 is from 1,000 (g / eq) to 19,000 (g / eq).

3. 3. The photosensitive resin letterpress printing plate precursor according to claim 1, wherein the ratio of F1 to F2 (F1 / F2) is greater than 1.0 and not greater than 5.

0.

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

5. 5. The photosensitive resin letterpress printing plate precursor according to claim 1, wherein the ratio of M1 to M2 (M1 / M2) is 1.0 or more and 6.5 or less.

6. 6. The photosensitive resin relief printing plate precursor according to claim 1, wherein the first photosensitive resin layer and the second photosensitive resin layer are adjacent to each other.

7. 7. The photosensitive resin letterpress printing plate precursor according to claim 1, wherein the first photosensitive resin layer has a thickness of 5 μm or more and 100 μm or less.

8. 8. The photosensitive resin letterpress printing plate precursor according to claim 1, wherein the second photosensitive resin layer has a thickness of 100 μm or more and 2.0 mm or less.

9. 9. The photosensitive resin letterpress printing plate precursor according to claim 1, wherein the component (A) comprises polyvinyl alcohol, partially saponified polyvinyl alcohol, and / or a tertiary nitrogen atom-containing polyamide.

10. A method for producing a relief printing plate using the photosensitive resin relief printing plate precursor according to any one of claims 1 to 9, comprising the steps of: an exposure step of irradiating ultraviolet light onto at least the photosensitive resin layer of the photosensitive resin relief printing plate precursor to photocure the exposed areas of the photosensitive resin layer; and A method for producing a relief printing plate, comprising a developing step of removing uncured portions of a photosensitive resin layer using at least water and / or an organic solvent.

11. The method for producing a relief printing plate according to claim 10, wherein in the developing step, the uncured portions are dissolved out using a brush-type washer.