Laminate for producing water-developable flexographic printing original plate

Abstract

Provided is a laminate for producing a flexographic printing original plate, said laminate containing a photosensitive resin layer having a strong surface-adhesion force and being of a type in which a functional resin layer is separately provided. Even when the laminate is stored in an environment where the temperature and humidity change significantly, it is possible to appropriately peel a cover film from the photosensitive resin layer. Comprising a laminate of a base film, a photosensitive resin layer and a cover film in that order, this laminate for producing a water-developable flexographic printing original plate is characterised in that a release layer is provided between, and in contact with, the photosensitive resin layer and the cover film, and the release layer contains an addition-type silicone polymer and a curing catalyst.

Description

Water-developable laminate for producing flexographic printing plates

[0001] The present invention relates to a high-resolution, water-developable laminate for producing a flexographic printing original plate, which is made by laminating a base film, a photosensitive resin layer, and a cover film in this order, and which allows the cover film to be appropriately peeled from the photosensitive resin layer.

[0002] A typical flexographic printing plate precursor is composed of a laminate of a base film, a photosensitive resin layer, a mask layer, and a cover film, laminated in this order, as shown in Figure 1. The cover film is intended to prevent the mask layer from becoming dirty or scratched during storage from the time the flexographic printing plate precursor is manufactured until it is actually used to create a printing plate. Therefore, at the time of use, the cover film is removed, and as shown in Figure 2, a desired pattern is drawn on the mask layer with an infrared laser, followed by irradiating the mask layer with ultraviolet light to harden the photosensitive resin layer according to the pattern of the mask layer, and finally, the flexographic printing plate is obtained by developing it with a developer such as water.

[0003] In this general method, a release layer (not shown) is provided between the cover film and the mask layer to ensure proper removal of the cover film. Materials used for the release layer include amino resins (see Patent Document 1) and acrylic resins (see Patent Document 2), which can form a uniform layer between the cover film and the mask layer.

[0004] On the other hand, in recent years, there has been an increasing demand for flexographic printing original plates with even higher resolution, and the resolution of the mask layer of the above-mentioned general flexographic printing original plates is limited, and improvements are being sought. In response to such demands, a method has been proposed in which the mask layer is separated from the photosensitive resin layer, the mask layer is provided on a polarizing film to form a separate laminate, and a pattern is drawn on the mask layer in this separate laminate, which is then laminated on the photosensitive resin layer (see Patent Document 3). Specifically, as shown in Figure 3, a laminate 1 having a base film, a photosensitive resin layer, and a cover film laminated in this order, and a laminate 2 having a mask layer and a polarizing film laminated in this order are prepared, and as shown in Figure 4, a desired pattern is drawn on the mask layer of laminate 2 with a high-resolution laser, and laminate 2 is laminated on top of the photosensitive resin layer of laminate 1 from which the cover film has been removed, with the drawn mask layer side facing the photosensitive resin layer, and integrated. After that, ultraviolet light is irradiated from the polarizing film side of laminate 2 to harden the photosensitive resin layer in accordance with the pattern of the drawn mask layer, and finally development is performed to obtain a flexographic printing plate.

[0005] In addition to the method of Patent Document 3 described above, other known methods include using a mask layer separated from a photosensitive resin layer, such as a mask layer on which an image of a high-resolution negative film or the like is formed, or a heat-sensitive mask layer on which an image is formed by laser ablation, or a method using these mask layers, on which another photosensitive resin layer having a different hardness from the resin of the photosensitive resin layer, another photosensitive resin layer having a different photopolymerizable unsaturated group concentration or photoinitiator concentration from the resin of the photosensitive resin layer, or another photosensitive resin layer having a different surface energy from the resin of the photosensitive resin layer is laminated. In the present invention, these mask layers and other photosensitive resin layers are collectively referred to as "functional resin layers."

[0006] In this method of separately providing a functional resin layer, unlike the general method, a cover film for protection during storage is provided on the photosensitive resin layer of the laminate 1. Peeling of the cover film from the photosensitive resin layer of this laminate 1 basically poses almost no problem when stored in an environment with little change in temperature and humidity. For this reason, in the conventional method of separately providing a functional resin layer, a release layer was not provided.

[0007] However, because the photosensitive resin layer contains liquid components such as crosslinking monomers and low-Tg polymers, the surface adhesive strength of the photosensitive resin layer tends to increase when stored in an environment with frequent temperature and humidity changes. In particular, in recent years, due to growing environmental considerations, there has been an increasing demand for water-developable flexographic printing plates that use water as a developer rather than organic solvents. However, when the photosensitive resin layer is made highly hydrophilic and water-developable to make the flexographic printing plate water-developable, the surface adhesive strength of the photosensitive resin layer tends to further increase. Therefore, in a laminate used for manufacturing a water-developable flexographic printing plate using a method in which a functional resin layer is separately provided, the photosensitive resin layer of the laminate 1 strongly adheres to the cover film during storage in an environment with frequent temperature and humidity changes, which causes a problem in which the cover film cannot be properly peeled off from the photosensitive resin layer.

[0008] Patent No. 5903854 Publication Patent No. 6135040 Publication Special Publication No. 2010-534345

[0009] The present invention has been made to solve the problems of the conventional art, and its object is to provide a water-developable laminate for producing a flexographic printing original plate in which the above-mentioned functional resin layer including the photosensitive resin layer having strong surface adhesive strength is separately provided, which allows the cover film to be properly peeled off from the photosensitive resin layer even when stored in an environment with large changes in temperature and humidity.

[0010] To achieve this objective, the present inventors first considered providing a release layer between the photosensitive resin layer and the cover film. Next, they used an amino resin (Patent Document 3) or an acrylic resin (Patent Document 4), which have been used as release layers in the above-mentioned general methods, as this release layer. However, they found that the water-developable photosensitive resin layer had such strong surface adhesion that the cover film could not be properly peeled off even with such a release layer. Therefore, the present inventors used a release layer containing an addition-type silicone polymer and a curing catalyst, which could not be used in general methods, and found that the cover film could be properly peeled off even with a water-developable photosensitive resin layer, thereby completing the present invention.

[0011] That is, the present invention was completed based on the above findings and has the following configurations (1) to (7). (1) A water-developable laminate for producing a flexographic printing plate comprising a base film, a photosensitive resin layer, and a cover film laminated in this order, wherein a release layer is provided between the photosensitive resin layer and the cover film in contact with both, and the release layer contains an addition type silicone polymer and a curing catalyst. (2) A laminate for producing a flexographic printing plate according to (1), wherein the addition type silicone polymer contains an alkenyl group at its terminal and / or side chain. (3) A laminate for producing a flexographic printing plate according to (1), wherein the curing catalyst is a hydrosilylation catalyst. (4) A laminate for producing a flexographic printing plate according to any one of (1) to (3), wherein the surface roughness (Ra) of the surface of the release layer in contact with the photosensitive resin layer is 0.01 to 0.2 μm. (5) The laminate for producing a flexographic printing plate according to any one of (1) to (3), wherein the peel strength when the cover film together with the release layer from the laminate for producing a flexographic printing plate is pulled at an angle of 90° at a speed of 1000 mm / min is 2.0 g / 20 mm to 50.0 g / 20 mm. (6) The laminate for producing a flexographic printing plate according to any one of (1) to (3), wherein the photosensitive resin layer contains a conjugated diene polymer, a photopolymerizable unsaturated compound, and a photopolymerization initiator. (7) A method for producing a flexographic printing plate, wherein the cover film together with the release layer is peeled from the laminate for producing a flexographic printing plate according to any one of (1) to (3), and then the resin layer surface of the functional resin layer is directly laminated on the photosensitive resin layer to produce a flexographic printing plate.

[0012] The laminate for producing a flexographic printing plate of the present invention has excellent releasability and storage stability of the release layer even when stored in an environment with large changes in temperature and humidity, and allows the cover film to be properly peeled from the photosensitive resin layer. Therefore, the laminate for producing a flexographic printing plate of the present invention can be suitably used in combination with a functional resin layer for stably producing a water-developable flexographic printing plate with high resolution.

[0013] Fig. 1 shows an example of the layer structure of a laminate constituting a flexographic printing plate precursor used in a general method. Fig. 2 shows an example of the manufacturing process of a flexographic printing plate manufactured using the laminate of Fig. 1. Fig. 3 shows an example of the layer structure of a laminate for manufacturing a flexographic printing plate precursor used in a method in which a functional resin layer is separately provided. Fig. 4 shows an example of the manufacturing process of a flexographic printing plate manufactured using the laminate of Fig. 3. Fig. 5 shows an example of the layer structure of a laminate for manufacturing a flexographic printing plate precursor of the present invention.

[0014] The laminate for producing a flexographic printing plate of the present invention has the same function as the laminate 1 (see Figure 3) for producing a flexographic printing plate using the method of separately providing a functional resin layer, and is characterized in that, in a laminate in which a base film, a photosensitive resin layer, and a cover film are laminated in this order, as shown in the upper part of Figure 5, a release layer is provided between the photosensitive resin layer and the cover film in contact with both of them. The release layer is also characterized in that it contains an addition type silicone polymer and a curing catalyst.

[0015] The base film of the laminate of the present invention is preferably a flexible material with excellent dimensional stability, such as polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, or polycarbonate film. Among these, polyethylene terephthalate film, which has excellent dimensional stability and high viscoelasticity, is particularly preferred. The thickness of the base film is preferably 50 to 350 μm, more preferably 100 to 350 μm, in view of mechanical properties, shape stability, and ease of handling of the printing plate. If necessary, a known adhesive layer may be provided between the base film and the photosensitive resin layer to improve adhesion between them.

[0016] The photosensitive resin layer of the laminate of the present invention is not particularly limited as long as it is water-developable, and for example, a layer containing (a) a conjugated diene polymer, (b) a photopolymerizable unsaturated compound, and (c) a photopolymerization initiator can be used. In the present invention, since the development step is carried out using an aqueous developer, it is preferable that the photosensitive resin layer further contains (d) a hydrophilic compound. As a photosensitive resin composition containing the components (a) to (d), for example, the one described in JP-A-2005-148588 can be suitably used.

[0017] The (a) conjugated diene polymer is preferably a conjugated diene polymer obtained from a water-dispersed latex, and conventionally known synthetic polymer compounds used in flexographic printing original plates can be used. The water-dispersed latex preferably contains one or more latexes selected from the group consisting of butadiene latex, acrylonitrile-butadiene latex, styrene-butadiene latex, and isoprene latex. It is more preferable to contain both butadiene latex and acrylonitrile-butadiene latex from the viewpoint of water developability. When using a conjugated diene polymer obtained from a water-dispersed latex, it is preferable that the polymer is intramolecularly crosslinked. If desired, the polymer may be modified with (meth)acrylic, carboxy, silicone, fluorine, or the like. A wide variety of synthetic and natural latexes are commercially available for water-dispersed latex, and an appropriate one can be selected from these.

[0018] As the (b) photopolymerizable unsaturated compound, any known compound used in flexographic printing original plates can be used, but it is preferable that the compound contains a photopolymerizable monomer such as a (meth)acrylate having a number-average molecular weight of 100 to 600, and further preferably contains a photopolymerizable oligomer such as a (meth)acrylate having a number-average molecular weight of more than 600 to 20,000. The photopolymerizable oligomer is not particularly limited as long as it has a number-average molecular weight in the range of more than 600 to 20,000, and examples thereof include butadiene oligomers or isoprene oligomers to which a (meth)acrylate group has been added, and urethane (meth)acrylates.

[0019] (c) Photopolymerization initiators that have the function of generating radicals by self-decomposition or hydrogen abstraction upon light absorption are preferably used. Examples of such photopolymerization initiators include benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, and diacetyls. Examples include benzophenone, chlorobenzophenone, benzoin, acetophenone, benzil, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzil dimethyl ketal, benzil diethyl ketal, benzil diisopropyl ketal, anthraquinone, 2-ethylanthraquinone, 2-methylanthraquinone, 2-allylanthraquinone, 2-chloroanthraquinone, thioxanthone, 2-chlorothioxanthone, and 1-hydroxycyclohexan-1-yl phenyl ketone. The photopolymerization initiator is preferably a compound consisting of two types of compounds: a benzyl alkyl ketal and a benzophenone, in order to efficiently use the light energy from post-exposure and exposure with a germicidal lamp.

[0020] (d) Hydrophilic compounds are used to improve water developability. For example, they are compounds having a hydrophilic group in the molecule, such as carboxylic acid, carboxylate, sulfonic acid, sulfonate, hydroxyl group, amino group, phosphate group, ethylene oxide, or propylene oxide, and are themselves water-soluble or water-dispersible. The hydrophilic compound may be a low-molecular-weight compound, an oligomer, a high-molecular-weight compound, or a hydrophilic polymer. Specific examples of the hydrophilic compound include polyhydric alcohols, polycarboxylic acids, ester compounds of polycarboxylic acids, acrylic polymers, polyalkylene glycol-modified polymers, urethane polymers, polyamide polymers, and polyester polymers. When a hydrophilic copolymer is used, internally crosslinked polymer particles containing units derived from a hydrophilic unsaturated monomer are preferred. Examples of these polymer particles include water-dispersed latexes prepared by dispersing polymer particles obtained by emulsion polymerization of a hydrophilic unsaturated monomer and, if necessary, other monomers copolymerizable therewith, in water as dispersoids.

[0021] In addition to the components (a) to (d) described above, the photosensitive resin layer of the laminate of the present invention may contain other components, such as plasticizers, ultraviolet absorbers, thermal polymerization inhibitors (stabilizers), surface tension modifiers, thermoplastic resin elastomers, solid rubbers, dyes, pigments, antifoaming agents, and anti-aggregation agents, as appropriate, for the purpose of improving various properties, within the range that does not impair the effects of the present invention.

[0022] The cover film of the laminate of the present invention is preferably a material that is flexible but has excellent dimensional stability, and examples of such materials include thermoplastic resin supports such as polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene terephthalate film. Among these, polyethylene terephthalate film, which has excellent dimensional stability and high viscoelasticity, is particularly preferred. The thickness of the cover film is preferably 50 to 350 μm, more preferably 70 to 250 μm, in terms of mechanical properties, shape stability, and ease of handling during printing plate making.

[0023] The release layer of the laminate of the present invention contains an addition type silicone polymer and a curing catalyst as a curing agent. The addition type silicone polymer is preferably a silicone polymer having an alkenyl group at the end and / or side chain. Examples of the alkenyl group include vinyl, allyl, propenyl, hexenyl, octenyl, and decenyl groups, with vinyl, allyl, and hexenyl being preferred in terms of curability. Commercially available examples of addition type silicone polymers include KS-3650, KS-774, KS-775, KS-778, KS-779H, KS-843, KS-847, KS-847H, KS-847T, KS-838, KS-856, X-62-2422, X-62-2461, X62-2829, X-62-1387, X-62-5039, X-62-5040, KNS-3051, X-62-1496, KNS320A, KNS316, and X-62-1, manufactured by Shin-Etsu Chemical Co., Ltd. 574A / B, X-62-7052, X-62-7028A / B, X-62-7619, X-62-7213, and SD7220, SD7226, SD7223, SD7292, SD7333, SRX211, SRX357, SRX345, LTC750A, LTC760A, LTC851, LTC759, LTC755, LTC761, LTC856, LTC310, LTC303E, LTC300B, and LTC350G manufactured by Dow Corning Toray Co., Ltd.

[0024] The addition type silicone polymer having an alkenyl group may also contain a hydrosilyl group (SiH) in the molecule. Commercially available examples include KS-3650, KS-843, KS-847, KS-847H, KS-847T, X62-2829, and KS838 manufactured by Shin-Etsu Chemical Co., Ltd., and SD7333, SRX357, SRX345, LTC310, LTC303E, LTC300B, LTC350G, LTC750A, LTC851, LTC759, LTC755, LTC761, and LTC856 manufactured by Dow Corning Toray Co., Ltd.

[0025] These addition type silicone polymers may be used alone or in combination of two or more. Furthermore, addition type silicone polymers without alkenyl groups may be contained within a range that does not impair performance. In this case, high molecular weight polymers that are less likely to bleed out are preferred.

[0026] Since the release layer contains an addition-type silicone polymer, it preferably contains a polyorganosiloxane compound (crosslinking agent) having a hydrosilyl group (SiH). The inclusion of such a polyorganosiloxane compound (crosslinking agent) facilitates the addition reaction, resulting in excellent releasability. A specific example of this compound is 1,3,5,7-tetramethylcyclotetrasiloxane.

[0027] The curing catalyst forms a crosslinked structure of the silicone polymer and has the effect of suppressing aggregation of the silicone polymer on the surface of the release layer or in the release layer. A hydrosilylation catalyst is preferred as the curing catalyst. The hydrosilylation catalyst is not particularly limited as long as it has catalytic activity for the hydrosilylation reaction, but examples include simple platinum, solid platinum supported on a carrier such as alumina, silica, or carbon black, chloroplatinic acid, complexes of chloroplatinic acid with alcohols, aldehydes, ketones, etc., platinum-olefin complexes, platinum-vinylsiloxane complexes, platinum-phosphine complexes, and platinum-phosphite complexes. Examples of catalysts other than platinum compounds include RhCl(PPh) ３ , RhCl ３ , RhAl ２ O ３ , RuCl ３ , IrCl ３ , FeCl ３ , AlCl ３ , PdCl ２ ・2H ２ O, NiCl ２ , TiCl ４Among these, in terms of release effect, platinum catalysts such as simple platinum, solid platinum supported on alumina, silica, or carbon black carriers, platinum-olefin complexes, platinum-vinylsiloxane complexes, platinum-phosphine complexes, and platinum-phosphite complexes are preferred. Platinum complexes such as platinum-vinylsiloxane complexes and platinum-olefin complexes are more preferred. These catalysts may be used alone or in combination of two or more.

[0028] Specific platinum catalysts may be produced by known methods or may be purchased commercially. Platinum-vinylsiloxane complexes can be produced by conventional methods such as those disclosed in Japanese Patent Publication No. 47-23679 and Japanese Patent Laid-Open Publication No. 11-128748. Commercially available platinum catalysts include PL-3 and CAT-PL-50T manufactured by Shin-Etsu Chemical Co., Ltd., and SRX212 manufactured by Dow-Toray Industries, Inc.

[0029] The amount of curing catalyst in the release layer is preferably 0.01 to 5.0 parts by weight, more preferably 0.015 to 4.0 parts by weight, and even more preferably 0.02 to 3.0 parts by weight, per 100 parts by weight of the addition-type silicone polymer. If the amount of curing catalyst is too small, the curing reaction does not proceed sufficiently, resulting in a large amount of residual Si—H groups, resulting in increased peel strength. Furthermore, the presence of unreacted organopolysiloxane can serve as a migratory component, potentially resulting in migration of the unreacted organopolysiloxane to the photosensitive resin layer to which the functional resin is bonded, resulting in reduced adhesive strength. Furthermore, when a functional resin layer is provided on a photosensitive resin layer, irradiated ultraviolet light can be scattered, resulting in reduced image reproducibility, or poor adhesion between the photosensitive resin layer and the functional resin layer can easily lead to peeling of the functional resin layer.

[0030] The release layer may contain a resin other than the addition type silicone polymer as long as it does not impair releasability. For example, it may contain a thermosetting resin such as an acrylic resin, a photocurable resin having a photopolymerizable unsaturated group, a phenolic resin, an epoxy resin, or a melamine resin. By containing a resin other than the addition type silicone polymer, it is possible to easily control the adhesion to the cover film and the peel strength of the release layer.

[0031] In addition to the addition-type silicone polymer and the curing catalyst, the release layer may contain a release force adjuster such as a silane coupling agent, a crosslinking agent, a tackifier, a plasticizer, or a softener for the purpose of adjusting the peel strength. Furthermore, other additives may be blended within a range that does not affect the releasability. For example, an anti-degradant, a filler, a colorant, an antioxidant, a surfactant, an antistatic agent, etc. may be blended.

[0032] The release layer can be produced by applying a coating liquid for forming a release layer onto a cover film. Conventional coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating can be used as the coating method. The coating liquid for forming a release layer can be prepared, for example, by mixing an addition-type silicone polymer and a curing catalyst with a solvent. Examples of solvents that can be used include ketones (e.g., methyl ethyl ketone), aromatic compounds (e.g., toluene), and the like. These can be used alone or in combination of two or more.

[0033] The thickness of the release layer is preferably 0.01 μm to 2 μm, more preferably 0.03 μm to 1.5 μm, and even more preferably 0.05 μm to 1 μm. If the thickness is too small, the release force may not be sufficiently adjusted. On the other hand, if the thickness is too large, streaks are likely to occur during production.

[0034] The surface roughness (Ra) of the surface of the release layer that comes into contact with the photosensitive resin layer is preferably 0.01 to 0.2 μm. By setting the surface roughness within this range, the surface roughness of the photosensitive resin layer surface can be reduced. As a result, air bubbles and wrinkles are less likely to be mixed in when the release layer comes into close contact with the functional resin layer, and defects can be reduced on the laminate surface with the functional resin layer. The surface roughness of the surface of the release layer that comes into contact with the photosensitive resin layer of the present invention refers to the surface roughness of the release layer that comes into contact with the photosensitive resin layer.

[0035] The laminate of the present invention preferably has a peel strength of 2.0 g / 20 mm to 50.0 g / 20 mm when the cover film and the release layer are pulled at an angle of 90° at a speed of 1000 mm / min. A more preferred peel strength is 3.0 g / 20 mm to 20.0 g / 20 mm. By setting the peel strength within this range, the release layer can be properly and uniformly peeled from the photosensitive resin layer.

[0036] Furthermore, it is preferable that the temperature dependency of the measured value of the peel strength (measured value at 10°C - measured value at 30°C) is small. By reducing the temperature dependency of the measured value, it is possible to reduce fluctuations in peel strength due to temperature. Specifically, the difference between the measured values ​​of the peel strength at temperatures of 10°C and 30°C (measured value at 10°C - measured value at 30°C) is preferably 30.0 grams / 20 mm or less, more preferably 10.0 grams / 20 mm or less.

[0037] Next, a method for producing a flexographic printing plate blank from the laminate of the present invention will be described. The laminate of the present invention shown in the upper part of Figure 5 can be efficiently produced into a flexographic printing plate blank by directly laminating the resin layer surface of the functional resin layer shown in the lower part of Figure 5 on the photosensitive resin layer after peeling and removing the cover film together with the release layer. The functional resin layer can be a conventionally known layer in this field, but examples include a mask layer on which an image such as a high-resolution negative film is formed, a heat-sensitive mask layer on which an image is formed by laser ablation, a separate photosensitive resin layer with a different hardness from the resin of the photosensitive resin layer, a separate photosensitive resin layer with a different photopolymerizable unsaturated group concentration or photoinitiator concentration from the resin of the photosensitive resin layer, and a separate photosensitive resin layer with a different surface energy from the resin of the photosensitive resin layer. The functional resin layer may be laminated on a support film. The support film also serves as an oxygen barrier layer. The effects of the present invention are particularly easily achieved when a high-resolution negative film is used as the functional resin layer. In the present invention, the negative film is a mask layer on which an image is formed to be laminated on a photosensitive resin layer, and usually refers to a mask layer provided on a support film.

[0038] In the present invention, a high-resolution negative film refers to one capable of reproducing 1% to 95% of 200-line halftone dots. A preferred high-resolution negative film is one in which a mask image is formed using a laser. A negative film in which a mask image is formed using a laser is preferably one in which the UV transmittance of the heat-sensitive mask layer is partially improved by changing the color development or optical transparency associated with laser heating, since this allows for the formation of finer highlight halftone dots. As described above, the support film in the negative film also serves as an oxygen barrier layer to reduce the effects of oxygen. In addition, to reduce the scattering of UV rays by the support film, a polarizing film may be used as the support film, or a UV absorber or UV-absorbing dye may be incorporated into the support film. High-resolution negative films can be commercially available or produced using known methods. Examples of commercially available high-resolution negative films include DITR4401 film manufactured by Kodak. Known high-resolution negative films include a mask layer in which the refractive index of a support film is controlled (Japanese Patent No. 5,368,432), a heat-sensitive mask layer in which a barrier layer containing an infrared-absorbing compound is provided on a support film (Japanese Patent No. 6,449,854), and a mask layer in which the support of the mask layer can be peeled off and removed (Japanese Patent No. 4,971,311).

[0039] Specific printing plates obtainable from the laminate of the present invention include flexographic printing plates having a photosensitive resin layer on which a mask layer with an image such as a high-resolution negative film is formed, or a heat-sensitive mask layer on which an image is formed by laser ablation, as a functional resin layer; and flexographic printing plates having a photosensitive resin layer on which another photosensitive resin layer with a different hardness from the resin of the photosensitive resin layer, another photosensitive resin layer with a different photopolymerizable unsaturated group concentration or photoinitiator concentration from the resin of the photosensitive resin layer, or another photosensitive resin layer with a different surface energy from the resin of the photosensitive resin layer, as a functional resin layer. Specifically, the laminate of the present invention can be used to produce a flexographic printing plate by directly laminating the resin layer surface of the functional resin layer on the photosensitive resin layer, and if the functional resin layer is a different photosensitive resin layer, a mask layer can be formed thereafter, and the printing plate can be produced through the usual platemaking processes such as ultraviolet exposure, development, drying, and post-exposure. The functional resin layer may be removed during the platemaking process, or it may remain on the photosensitive resin layer as a resin layer without being removed.

[0040] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0041] [Example 1] Preparation of a release film 99 parts by mass of a vinyl group-containing addition silicone polymer (KS-847T: manufactured by Shin-Etsu Chemical Co., Ltd.) and 1 part by mass of a curing catalyst (CAT-PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) were diluted with a methyl ethyl ketone / toluene mixed solvent (mixing mass ratio 1:1) to prepare a coating liquid for a release layer with a concentration of 2% by mass. Next, the coating liquid was applied using a wire bar to a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm to become a cover film so that the coating layer thickness after drying would be 0.1 μm, and the coating was dried and cured at 120 ° C. for 40 seconds to obtain a release film consisting of a release layer and a cover film.

[0042] Preparation of Photosensitive Resin Composition (a) 39 parts by mass of butadiene latex (Nipol LX111NF, non-volatile content 55% by mass, manufactured by Zeon Corporation) as a conjugated diene polymer obtained from a water-dispersed latex, carboxy-modified acrylonitrile-butadiene latex (Nipol LX111NF, non-volatile content 55% by mass, manufactured by Zeon Corporation) (SX1503, nonvolatile content 42% by mass, manufactured by Zeon Corporation) 6 parts by mass, (b) oligobutadiene acrylate (ABU-4, manufactured by Kyoeisha Chemical Co., Ltd.) as a photopolymerizable unsaturated compound 17 parts by mass, trimethylolpropane trimethacrylate (Light Ester TMP, manufactured by Kyoeisha Chemical Co., Ltd.) 6.4 parts by mass, 25 parts by mass of the metal chloride of the diene polymer having a carboxyl group at its end, (c) photopolymerization initiator (Irgacure 651) 1 part by mass, (d) butadiene oligomer (LBR-352, manufactured by Kuraray Co., Ltd.) 5.5 parts by mass, and heat stabilizer (4-methoxyphenol) 0.1 parts by mass were mixed in a container to prepare a dope. The dope was placed in a pressure kneader, and tetrahydrofuran and water were removed under reduced pressure at 80 ° C. to obtain a photosensitive resin composition.

[0043] Preparation of a laminate for producing a flexographic printing plate precursor The above photosensitive resin composition was placed on a polyethylene terephthalate base film (support) (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolymer polyester adhesive to form a photosensitive resin layer. Next, the above release film was placed on top of it with the release layer facing the photosensitive resin layer. They were then pressed together at 100°C using a heat press to obtain a laminate for producing a flexographic printing plate precursor. The total thickness of this laminate was 1.14 mm.

[0044]

[0049] As the functional resin layer, a high-resolution negative film (a mask layer in which the transmittance of ultraviolet light is partially improved by changes in color development or optical transparency due to heating with a laser) was prepared. Specifically, a negative film having a 100 μm thick support film with a 1% to 95% halftone dot density of 200 lines, a minimum independent point diameter of 100 μm, a minimum raised character size of 1 point, a minimum hollow character size of 1 point, and a solid image was prepared from DITR4401 film (manufactured by Kodak), a high-resolution negative film compatible with printing resolutions up to 200 lpi. A TRENDSETTER imager (manufactured by Kodak) capable of SQUAREspot thermal imaging using an 830 nm infrared laser diode was used to prepare a negative film.

[0045] Preparation of Flexographic Printing Plate and Flexographic Printing Plate The cover film was peeled off together with the release layer from the laminate for producing a flexographic printing plate, and the resin layer surface (the surface opposite to the support film) of the functional resin layer was laminated onto the photosensitive resin layer of the laminate for producing a flexographic printing plate to obtain a flexographic printing plate. The obtained printing plate was processed to produce a printing plate by the following method. First, a back exposure was performed for 10 seconds from the support side (polyethylene terephthalate base film) of the printing plate. Subsequently, a main exposure was performed for 7 minutes. After that, the plate was developed for 8 minutes in a developing machine manufactured by A&V Corporation (Stuck System, 1% laundry soap aqueous solution, 40°C), and water droplets on the plate surface were removed with a water-blowing rod. After that, the plate was dried for 10 minutes in a dryer at 60°C. Subsequently, a post-exposure was performed for 7 minutes, and finally, a flexographic printing plate was obtained by irradiating it with a germicidal lamp for 5 minutes.

[0046] [Example 2] A release film was formed in the same manner as in Example 1, except that in the preparation of the coating liquid for the release layer, the vinyl group-containing addition type silicone polymer (KS-847T: manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a 30 mass % toluene solution of a vinyl group-containing addition type silicone polymer (KS-774 manufactured by Shin-Etsu Chemical Co., Ltd.). Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0047] [Example 3] A release film was formed in the same manner as in Example 1, except that in the preparation of the coating liquid for the release layer, the vinyl group-containing addition type silicone polymer (KS-847T: manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a hexenyl group-containing addition type silicone polymer (LTC750A manufactured by Toray Dow Corning Co., Ltd.). Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0048] [Example 4] A release film was formed in the same manner as in Example 1, except that in the preparation of the coating liquid for the release layer, the curing catalyst (CAT-PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a curing catalyst (PL-3: manufactured by Shin-Etsu Chemical Co., Ltd.). Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0049] [Example 5] A release film was formed in the same manner as in Example 1, except that in the preparation of the coating liquid for the release layer, the curing catalyst (CAT-PL-50T: manufactured by Shin-Etsu Chemical) was changed to a curing catalyst (SRX212: manufactured by Dow-Toray Co., Ltd.). Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0050] [Example 6] A release film was formed in the same manner as in Example 1, except that in preparing the coating liquid for the release layer, a crosslinking agent (1,3,5,7-tetramethylcyclotetrasiloxane) was blended in addition to the addition silicone polymer and curing catalyst at the blending ratio shown in Table 1. Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0051] Example 7 A release film was produced in the same manner as in Example 1, except that in the preparation of the coating liquid for the release layer, the vinyl group-containing addition type silicone polymer (KS-847T: manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a mixture of the vinyl group-containing addition type silicone polymer (KS-847T: manufactured by Shin-Etsu Chemical Co., Ltd.) and a hexenyl group-containing addition type silicone polymer (LTC750A manufactured by Dow Corning Toray Co., Ltd.) in a solids mass ratio of 70 / 30. Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0052] [Example 8] A release film was formed in the same manner as in Example 1, except that the blending ratio of the curing catalyst was reduced as shown in Table 1. Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0053] Comparative Example 1 A laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1, except that a cover film without a release layer was used.

[0054] Comparative Example 2 A release film was formed in the same manner as in Example 1, except that in the preparation of the coating liquid for the release layer, the vinyl group-containing addition silicone resin (KS-847T: manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a non-addition silicone polymer (X-52-8046: manufactured by Shin-Etsu Chemical Co., Ltd.). Using the obtained release film, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1.

[0055] [Comparative Example 3] A release film containing an amino resin was produced according to the method for producing a release force adjusting layer described in Japanese Patent No. 5903854. Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0056] [Comparative Example 4] An acrylic resin release film was produced according to the method for producing a release force adjusting layer described in Japanese Patent No. 6135040. Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0057] Comparative Example 5 A release film was formed in the same manner as in Example 1, except that no curing catalyst (CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.) was blended in the coating liquid for the release layer in Example 1. Next, a laminate for producing a flexographic printing original plate was produced in the same manner as in Example 1 using the obtained release film.

[0058] Reference Example 1: A photosensitive resin layer was used that was not water-developable but solvent-developable. First, 100 parts by weight of a block copolymer (Tufprene 912: manufactured by Asahi Kasei Corporation), 10 parts by weight of liquid polybutadiene (NISSO-PB-B-1000: manufactured by Nippon Soda Co., Ltd.), and 2 parts by weight of 2,6-di-t-butyl-p-cresol were kneaded at 170 ° C. using a kneader mixer. The kneading temperature was then lowered to 130 ° C., and 10 parts by weight of 1,6-hexanediol dimethacrylate, 0.01 parts by weight of methylhydroquinone, and 1 part by weight of a photopolymerization initiator (Irgacure 651) were added and kneaded to obtain a solvent-developable photosensitive resin composition. The photosensitive resin composition was applied to a polyethylene terephthalate base film (Toyobo Co., Ltd., E5000, thickness 125 μm) coated with a copolymer polyester adhesive to form a photosensitive resin layer. Next, a film without a release coating (Toyobo Co., Ltd., E5000, thickness 100 μm) was placed on top of the photosensitive resin layer. These were then pressed together at 100°C using a heat press to obtain a laminate for producing flexographic printing plates. The total thickness of this laminate was 1.14 mm. The cover film was peeled off from the resulting laminate for producing flexographic printing plates, and the resin layer surface of the functional resin layer identical to that of Example 1 was laminated onto the photosensitive resin layer of the laminate for producing flexographic printing plates, thereby obtaining a flexographic printing plate. The resulting printing plate was processed to produce a printing plate using the following method. First, a back exposure was performed from the polyester support side of the printing plate for 10 seconds. Subsequently, a main exposure was performed for 7 minutes. The plate was then developed for 8 minutes using a developing machine (Stuck System, manufactured by A&V Corporation, using mineral spirits as the developer) and then dried for 120 minutes in a dryer at 60°C. Subsequently, post-exposure was carried out for 7 minutes, and finally, irradiation with a germicidal lamp was carried out for 5 minutes to obtain a flexographic printing plate.

[0059] The laminates and printing plates of the above-mentioned Examples, Comparative Examples, and Reference Examples were evaluated for the following properties (1) to (6). The evaluation methods were as follows.

[0060] (1) Cover film peel strength (10°C, 30°C) A laminate for producing a flexographic printing plate prepared as a test piece was cut into a size of 120 mm x 20 mm, the edge of the cover film was peeled off with a fingertip, and the test piece was set in a peel tester and pulled at a 90° angle at a speed of 10,000 mm / min to measure the peel strength (grams / 20 mm). The measurement was carried out in an environment of 10°C or 30°C. The peel strength was evaluated as follows: Excellent: Peel strength was within the range of 3.0 grams / 20 mm or more and 20.0 grams / 20 mm or less. Good: Peel strength was outside the above range of Excellent, but within the range of 2.0 grams / 20 mm or more and 50.0 grams / 20 mm or less. Bad: Peel strength was outside both the ranges of Excellent and Good.

[0061] (2) Temperature Dependence of Peel Strength (10°C Measurement Value - 30°C Measurement Value) In order to evaluate the temperature dependency of the peel strength of the release layer, the peel strength was measured at temperatures of 10°C and 30°C, and the difference between these measurements was evaluated. The smaller the difference in the peel strength measurements (10°C Measurement Value - 30°C Measurement Value), the smaller the temperature dependency of the peel strength. The evaluation was made in the following manner. ◎: When the difference in the peel strength measurements is 10 grams / 20 mm or less ○: When the difference in the peel strength measurements is more than 10 grams / 20 mm and 20 grams / 20 mm or less ×: When the difference in the peel strength measurements is more than 20 grams / 20 mm

[0062] (3) Storage stability of peel strength (3 months): After storing the obtained laminate at 30°C and 80% RH for 3 months, the peel strength of the cover film of the laminate was measured at 10°C in the same manner as in (1) Cover film peel strength (10°C, 30°C), and the peel strength was determined.

[0063] (4) Presence or absence of bleed-out The obtained laminate was stored separately for one month in environments of 20°C, 65% RH and 30°C, 80% RH, and then, when the cover film was peeled off, it was visually judged whether or not the resin bleeds out from the release layer. The presence or absence of bleed-out was evaluated as follows: ○: No bleed-out ×: Bleed-out

[0064] (5) Surface Roughness (Ra) of the Release Layer The surface roughness (Ra) of the release layer is the surface roughness (Ra) of the release layer surface of the release film. The measurement was performed by a confocal method using a confocal laser microscope. Specifically, a Keyence VK9510 confocal laser microscope was used as the confocal laser microscope. The objective lens magnification was 50x. A sample measuring 10 cm long x 10 cm wide was cut out from the release layer, and the sample was placed on the measurement stage of the confocal laser microscope. The surface roughness (Ra) was measured at a total of 20 locations while moving the sample vertically and / or horizontally by approximately 5 mm. The average of these measured surface roughness (Ra) values ​​was taken as the surface roughness (Ra) of the release layer.

[0065] (6) Image reproducibility of printing plate The obtained laminate was stored separately for one month in environments of 20°C, 65% RH and 30°C, 80% RH, and then flexographic printing plates were produced as described above, and image reproducibility was evaluated using each of the obtained flexographic printing plates. ◯: no uneven adhesion (leakage of ultraviolet light), △: partial uneven adhesion, and ×: overall uneven adhesion.

[0066] Table 1 shows the details and evaluation results of the laminates of each of the Examples, Comparative Examples, and Reference Examples.

[0067]

[0068] As can be seen from Table 1, the laminates of Examples 1 to 8, which satisfy the requirements of the present invention, all have cover film peel strengths within an appropriate range, and the difference in peel strength due to temperature (measured at 10°C - measured at 30°C) is small (i.e., temperature dependency is small). Furthermore, even after storage at 30°C for three months, there is little change in the cover film peel strength, demonstrating excellent storage stability. Therefore, the laminates of Examples 1 to 8 allow for easy lamination of a functional resin layer without being affected by seasonal changes, and high-quality printing master plates can be obtained, with the resulting printing plates exhibiting excellent image reproducibility.

[0069] In contrast, in Comparative Example 1, the cover film could not be peeled off because there was no release layer. In Comparative Example 2, the release layer did not contain an addition-type silicone polymer, so the peel strength could not be optimized and bleed-out could not be suppressed. As a result, the image reproducibility of the printing plate was poor and it was not usable as a printing plate. Furthermore, in Comparative Example 3, which used a release layer containing an amino resin, and Comparative Example 4, which used a release layer containing an acrylic resin, the peel strength of the cover film was not within the appropriate range, and peeling of the cover film was difficult, especially at a low temperature of 10°C. In Comparative Example 5, the release coating composition did not contain a curing catalyst, so the peel strength could not be optimized and bleed-out could not be suppressed.

[0070] The laminate for producing a flexographic printing plate of the present invention can achieve excellent cover film peelability even when stored in an environment with varying temperature and humidity, and therefore can provide a water-developable flexographic printing plate precursor that is free from defects such as migration of silicone polymers that cause quality degradation on the surface of the photosensitive resin layer. Therefore, the present invention is extremely useful in the industry in which high-resolution water-developable flexographic printing plates are desired.

Claims

1. A water-developable laminate for producing a flexographic printing plate, which is formed by laminating a base film, a photosensitive resin layer, and a cover film in this order, and which is characterized in that a release layer is provided between the photosensitive resin layer and the cover film in contact with both, and that the release layer contains an addition-type silicone polymer and a curing catalyst.

2. The laminate for producing a flexographic printing original plate according to claim 1, wherein the addition type silicone polymer contains an alkenyl group at its terminal and / or side chain.

3. The laminate for producing a flexographic printing original plate according to claim 1, wherein the curing catalyst is a hydrosilylation catalyst.

4. A laminate for manufacturing a flexographic printing original plate according to any one of claims 1 to 3, characterized in that the surface roughness (Ra) of the surface of the release layer that comes into contact with the photosensitive resin layer is 0.01 to 0.2 μm.

5. A laminate for producing a flexographic printing plate described in any one of claims 1 to 3, characterized in that the peel strength when the cover film together with the release layer is pulled from the laminate for producing a flexographic printing plate at an angle of 90° at a speed of 1000 mm / min is 2.0 g / 20 mm to 50.0 g / 20 mm.

6. A laminate for producing a flexographic printing original plate according to any one of claims 1 to 3, characterized in that the photosensitive resin layer contains (a) a conjugated diene polymer, (b) a photopolymerizable unsaturated compound, and (c) a photopolymerization initiator.

7. A method for producing a flexographic printing plate, characterized in that the cover film is peeled off together with the release layer from the laminate for producing a flexographic printing plate described in any one of claims 1 to 3, and then the resin layer surface of the functional resin layer is directly laminated on the photosensitive resin layer to produce a flexographic printing plate.

Images