JP2006002061A - Crosslinkable resin composition for laser engraving and original plate of crosslinkable resin printing plate for laser engraving and method for producing relief printing plate and relief printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose an original plate of a printing plate capable of directly carrying out printing by laser engraving, having suitability not only as resin relief-printing application having suitability for oil ink, but also as flexographic printing in which printing is carried out by weak printing pressure. <P>SOLUTION: The crosslinkable resin composition for laser engraving comprises a hydrophilic polymer (A1) containing hydroxyethylene, a hydrophilic polymer (A2) other than (A1), an ethylenic unsaturated monomer (B), a polymerization initiator (C) and a plasticizer (D) as units. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crosslinkable resin composition suitable for laser engraving, a crosslinkable resin printing plate precursor, a method for producing a relief printing plate using the same, and a relief printing plate.

  As a method for forming a relief plate by forming irregularities on the surface, a photosensitive elastomer composition or a photosensitive resin composition is used, these compositions are exposed to ultraviolet light through an original film, and an image portion is selectively selected. The so-called “analog plate-making” method is well known in which an uncured portion is removed using a developer.

  The photosensitive elastomer composition contains an elastomeric polymer such as a synthetic rubber as a carrier, and the resulting relief plate is flexible, so that it is called a flexographic plate. The flexographic plate is suitable for water-based inks, alcohol inks, ester inks and solventless UV inks using an ink vehicle that does not erode rubber. Since flexographic plates are flexible, they have printability on printed materials with large surface irregularities and low-strength packaging materials. However, since they are easily deformed by stress, it is necessary to reduce the printing pressure. On the other hand, the photosensitive resin composition uses a plastic resin (plastic) as a carrier. The resulting relief plate is hard and is called a resin relief (letter press), and is distinguished from a flexographic plate. A commercially available resin relief plate is a water development type or an alcohol development type, and contains a water-soluble resin or an alcohol-soluble resin, respectively. The ink mainly used is an oil-based ink using an ink vehicle that does not erode these resins, or a solventless UV ink. Since the resin relief printing plate is hard, it is possible to apply a strong printing pressure, and clear and sharp printing can be performed by thickening the ink.

  In many cases, analog plate making requires an original film using a silver salt material, and thus requires production time and cost of the original film. Furthermore, since chemical processing is required for developing the original image film and processing of the development waste liquid is also required, there is a disadvantage in environmental hygiene.

  As a technique for solving the problems associated with analog plate making, a flexographic printing plate precursor in which a laser-sensitive mask layer element capable of forming an image mask in situ is provided on a photosensitive elastomer layer or a photosensitive resin layer. Resin relief printing plate precursors have been proposed (see, for example, Patent Documents 1 and 2). In the plate making method of these original plates, laser irradiation is performed based on image data controlled by a digital device, an image mask is formed on the spot from a mask layer element, and thereafter, through an image mask as in analog plate making. This is a plate making method in which the photosensitive elastomer layer (or photosensitive resin layer) and the image mask are developed and removed by exposure with ultraviolet light, and is referred to as “CTP method” in the flexographic printing plate and resin relief printing industry. The CTP method solves the problems related to the production process of the original film described above, but has a problem related to the treatment of the waste liquid generated in the development of the photosensitive elastomer layer and the photosensitive resin layer. Furthermore, in the case of a flexographic plate, a chlorine-based solvent such as trichlorethylene is often used for development, which is disadvantageous in terms of work hygiene.

  As a means for solving the problems related to the development process and development waste liquid, a so-called “thermal development method” has been proposed in which the photosensitive elastomer layer is heated and the uncured portion is softened and removed (see, for example, Patent Document 3). . Since this method does not use a developing solution, it is preferable in terms of work environment, and the development waste can be incinerated without the need for special separation processing. However, the heat development method has a problem that the development speed is remarkably slower than that of the solvent development method, so that the work efficiency is low and a complicated and expensive development facility is required.

  As another means for solving the problems relating to the development process and the development waste liquid, many direct engraving plate making using laser, so-called “laser engraving” has been proposed. Laser engraving literally engraves with a laser to form reliefs, and has the advantage that the relief shape can be freely controlled, unlike relief formation using an original film. For example, it is possible to sculpt deeply a portion where the extracted character portion is reproduced on the printed matter, or sculpture with a shoulder so that the halftone dot is not collapsed by losing the printing pressure at the portion reproducing the fine halftone dot.

  Patent Documents 4 to 7 disclose a flexographic printing plate precursor capable of laser engraving or a flexographic printing plate obtained by laser engraving. In these documents, a monomer is mixed with an elastomeric rubber as a binder, the mixture is cured by a thermal polymerization mechanism or a photopolymerization mechanism, and then laser engraving is performed to obtain a flexographic plate. These are flexographic printing plates suitable for water-based inks and ester inks, and are not suitable for resin letterpress applications in which oil-based inks are mainly used.

Patent Documents 8 to 10 disclose resin letterpress original plates capable of laser engraving or resin letterpress obtained by laser engraving. Patent Document 8 exemplifies a photosensitive resin composition containing polyamide or partially saponified polyvinyl alcohol alone as a polymer. According to the formulation shown in the examples, the hardness of the printing plate after photocuring is a general hardness as a resin relief plate, but is clearly hard as a flexographic plate and unsuitable for flexographic printing. . Patent Document 9 and Patent Document 10 are clearly intended for resin relief printing, and are similarly unsuitable for flexographic printing.
Japanese Patent No. 2773847 (pages 3-9) JP-A-9-171247 (pages 3-7) JP 2002-357907 (pages 7-18) Japanese Patent No. 2846954 (pages 1-7) JP-A-11-338139 (page 2-6) US Patent Application Publication No. 2003/180636 (pages 1-9) EP 1288864 (pages 2-6) JP-A-11-170718 (page 4) JP 2000-168253 A (page 2-6) JP 2001-328365 A (page 2-9)

  The purpose of the present invention is to propose a printing plate precursor capable of direct plate making by laser engraving, which is suitable not only for resin letterpress applications suitable for oil-based inks but also for flexographic printing plates that are printed with weak printing pressure. There is to do.

In order to solve the above problems, according to the present invention, a crosslinkable resin printing plate precursor mainly having the following constitution is provided. That is,
"Hydrophilic polymer (A1) containing hydroxyethylene as a constituent unit, hydrophilic polymer (A2) other than (A1), ethylenically unsaturated monomer (B), polymerization initiator (C) and plasticizer (D) It is a crosslinkable resin composition for laser engraving.

Furthermore, the manufacturing method of the relief printing plate which mainly has the following structures is provided. That is,
“At least (1a) a step of irradiating the crosslinkable resin printing plate precursor for laser engraving of the present invention with an actinic ray to crosslink the crosslinkable relief layer, (2) a relief printing comprising the step of laser engraving the crosslinked relief layer Process for producing a plate. "Or" At least (1b) a step of heating the crosslinkable relief printing plate precursor for laser engraving of the present invention to crosslink the crosslinkable relief layer, and (2) a step of laser engraving the crosslinked relief layer. A method for producing a relief printing plate comprising

  According to the present invention, it is possible to easily provide a relief printing plate having suitability for both resin relief printing and flexographic printing. If a crosslinkable resin is used, it can be applied not only to resin relief plates and flexographic plates, which are printing plates having a convex relief, but also to intaglio plates, planographic plates, and stencil plates, but the application range is not limited to these. Absent.

  Embodiments of the present invention will be described below.

  The crosslinkable resin printing plate precursor for laser engraving in the present invention has a structure in which an adhesive layer, a crosslinkable relief layer, an optional slip coat layer, and an optional protective film are optionally laminated on a support.

  The crosslinkable resin printing plate precursor for laser engraving of the present invention becomes a printing plate precursor to be laser engraved by crosslinking the crosslinkable relief layer, and becomes a relief printing plate by laser engraving the printing plate precursor. The relief printing plate of the present invention is not only a resin relief plate that is suitable for oil-based inks and printed with a strong printing pressure, but also a flexographic printing plate that has flexible properties and is printed with a weak printing pressure (kiss touch). Can also be used. The relief printing plate of the present invention can be used as a resin relief plate by using a carrier resin that is resistant to an oily solvent (printing by a relief printing press), and the relief printing plate (especially the relief layer) has flexibility. By applying, it is possible to apply to flexographic printing.

  The crosslinkable relief layer in the present invention comprises a crosslinkable resin composition. The crosslinkable resin composition means a composition that can be crosslinked by irradiating an actinic ray or by heating. By crosslinking the composition, abrasion of the relief layer during printing can be prevented, and a relief printing plate having a sharp shape after laser engraving can be obtained.

  The crosslinkable resin composition contains a hydrophilic polymer (A) serving as a carrier, an ethylenically unsaturated monomer (B), a polymerization initiator (C), and a plasticizer (D). Furthermore, polymerization inhibitors, dyes, pigments, surfactants, ultraviolet absorbers, fragrances, antioxidants and the like may be added as optional components.

  As the hydrophilic polymer (A), one having resistance to oil-based ink is used. A hydrophilic polymer means a polymer that dissolves or swells in water. Hydrophilic resins are generally resistant to oil-based inks and are preferably used. Examples of such resins include polyvinyl alcohols, cellulose resins, acrylic resins, polyamide resins introduced with hydrophilic groups such as polyethylene oxide, and the like.

  When these hydrophilic polymers are used as a single type of carrier for the crosslinkable resin composition, the intermolecular force between the hydrophilic polymers is strengthened due to the similarity of the hydrogen bond strength and polarity. For this reason, the relief layer obtained becomes hard and it is difficult to express the flexibility required for the flexographic plate. As a result of intensive studies, surprisingly, the relief layer was successfully made flexible by using a plurality of hydrophilic polymers in combination. Specifically, the relief layer can be made flexible by using a hydrophilic polymer (A1) containing hydroxyethylene as a structural unit and a hydrophilic polymer (A2) other than (A1). Multiple polymers with significant differences in polarity and structure will act as plasticizers for each other.

  Examples of the hydrophilic polymer (A1) containing hydroxyethylene as a structural unit include polyvinyl alcohol and vinyl alcohol / vinyl acetate copolymer (partially saponified polyvinyl alcohol), and these modified products also fall under this category. As (A1), a single polymer may be used, or a plurality of types may be mixed and used. Examples of modified products include polymers in which at least some of the hydroxyl groups have been modified to carboxyl groups, polymers in which some of the hydroxyl groups have been modified to (meth) acryloyl groups, polymers in which at least some of the hydroxyl groups have been modified to amino groups, and side chains. Examples thereof include ethylene glycol, propylene glycol, and polymers introduced with these dimers.

  A polymer in which at least a part of the hydroxyl group is modified to a carboxyl group can be obtained by esterification with polyvinyl alcohol or partially saponified polyvinyl alcohol and a polyfunctional carboxylic acid such as succinic acid, maleic acid or adipic acid. .

  A polymer in which at least a part of the hydroxyl group is modified to a (meth) acryloyl group can be obtained by adding a glycidyl group-containing ethylenically unsaturated monomer to the carboxyl group-modified polymer, or polyvinyl alcohol or partially saponified polyvinyl alcohol and (meth) acrylic. It can be obtained by esterification with an acid.

  A polymer in which at least a part of the hydroxyl group is modified with an amino group can be obtained by esterification with polyvinyl alcohol or partially saponified polyvinyl alcohol and a carboxylic acid containing an amino group such as carbamic acid.

  Polymers with ethylene glycol, propylene glycol, and their multimers introduced in the side chain are heated with polyvinyl alcohol or partially saponified polyvinyl alcohol and glycols under sulfuric acid catalyst, and by-product water is removed from the reaction system. It can be obtained by removing.

  Among these polymers, a polymer in which at least a part of the hydroxyl group is modified to a (meth) acryloyl group is particularly preferably used. By directly introducing an unreacted crosslinkable functional group into the polymer component, the strength of the relief layer can be increased without using a large amount of a polyfunctional monomer as the ethylenically unsaturated monomer (B) described later. This is because both flexibility and strength can be achieved.

  The weight average molecular weight (in terms of polystyrene by GPC measurement) of the hydrophilic polymer (A1) is preferably 10,000 to 500,000. If the weight average molecular weight is 10,000 or more, the form retainability as a single resin is excellent, and if it is 500,000 or less, it is easy to dissolve in a solvent such as water, which is convenient for preparing a crosslinkable resin composition.

  The hydrophilic polymer (A2) other than (A1) is a polymer that does not contain hydroxyethylene as a structural unit and has a polarity that is compatible with (A1), that is, a hydrophilic polymer. means. Polyamide obtained by polymerization of only adipic acid, 1,6-hexanediamine, and ε-caprolactam is water-insoluble and clearly differs in polarity from (A1). A hydrophilic polyamide into which a hydrophilic group such as polyethylene glycol or piperazine has been introduced exhibits compatibility with (A1) due to the action of the hydrophilic group, and is therefore used as a hydrophilic polymer (A2) other than (A1). It is suitable for. That is, since the hydrophilic polyamide is compatible with (A1), it can easily enter between the molecules of (A1), and both molecules (A1) and (A2) are affected by the hydrophobic portion of the hydrophilic polyamide. The intermolecular force between them is weakened, resulting in a softening of the polymer. A polyamide having a polyethylene glycol unit is obtained by reacting ε-caprolactam and / or adipic acid with a polyethylene glycol modified with both terminal amines, and a hydrophilic polyamide having a piperazine skeleton is obtained by reacting with piperazine. Moreover, the hydrophilic polyamide by which the crosslinkable functional group was introduce | transduced into the polymer is obtained by making the amide group of hydrophilic polyamide react with the epoxy group of glycidyl methacrylate. These hydrophilic polymers (A2) may be used alone or in combination of two or more.

  The ethylenically unsaturated monomer (B) is a compound that can be cross-linked by radical polymerization, and plays a role of imparting strength to the relief layer. Examples of the component (B) include the following. 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, β-hydroxy-β ′-(meth) (Meth) acrylate having a hydroxyl group such as acryloyloxyethyl phthalate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) Alkyl (meth) acrylates such as acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate, chloroethyl (meth) Alkyl alkyl (meth) acrylates such as acrylate, chloropropyl (meth) acrylate, alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, phenoxyethyl acrylate Alkoxyalkylene glycols (meth) such as phenoxyalkyl (meth) acrylates such as nonylphenoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate Acrylate, (meth) acrylamide, diacetone (meth) acrylamide, N, N′-methylenebis (meth) acrylate (Meth) acrylamides such as luamide, 2,2-dimethylaminoethyl (meth) acrylate, 2,2-diethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethyl Compounds having only one ethylenically unsaturated bond such as aminopropyl (meth) acrylamide, di (meth) acrylate of polyethylene glycol such as diethylene glycol di (meth) acrylate, such as dipropylene glycol di (meth) acrylate Polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycerol tri (meth) acrylate Such as poly (meth) acrylates and glycidyl (meth) acrylates obtained by addition reaction of compounds with ethylenically unsaturated bonds and active hydrogen such as unsaturated carboxylic acids and unsaturated alcohols to relate, ethylene glycol diglycidyl ether Polyhydric (meth) acrylamides such as polyvalent (meth) acrylates and methylenebis (meth) acrylamides obtained by the addition reaction of unsaturated epoxy compounds with compounds having active hydrogen such as carboxylic acids and amines, and many compounds such as divinylbenzene. And compounds having two or more ethylenically unsaturated bonds, such as a polyvalent vinyl compound. In this invention, these can be used individually or in combination of 2 or more types.

  As these ethylenically unsaturated monomers (B), if a polyfunctional monomer having two or more functional groups is used in a large amount, the hardness of the printing plate is increased and the flexibility necessary for flexographic printing cannot be obtained. It is preferable to suppress. Among monofunctional monomers, relatively high molecular weight monomers are preferably used because they contribute to softening of the printing plate. The selection of these monomers is facilitated with the aid of the introduction of unreacted crosslinkable functional groups into the hydrophilic polymer (A) described above.

  The polymerization initiator (C) acts as an initiator for crosslinking of the ethylenically unsaturated monomer (B). However, when a crosslinking functional group is introduced into the hydrophilic polymer (A), the polymerization initiator (C) is used for crosslinking of (A). Also contribute. As such a polymerization initiator, it is preferable to use a photopolymerization initiator that generates radicals by irradiating active light such as ultraviolet light, but a thermal polymerization initiator that generates radicals by heating is used. It may be used.

  As photopolymerization initiators, acetophenone compounds such as diethoxyacetophenone, benzyldimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, benzoin compounds such as benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, o -Benzophenone compounds such as methyl benzoylbenzoate, 4-benzoyl-4'-methyl-diphenyl sulfide, thioxanthone compounds such as 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, triethanolamine , Triisopropanolamine, ethyl 4-dimethylaminobenzoate, 4,4′-bisdiethylaminobenzophenone, 4,4′-bis And amine compounds such as methylamino benzophenone (Michler's ketone), benzyl dimethyl ketal, benzyl-based, camphorquinone, 2-ethyl anthraquinone, such as 9,10-phenanthrenequinone is preferably used. You may use these individually or in combination of 2 or more types.

  Thermal polymerization initiators include acetyl peroxide, cumyl peroxide, tert-butyl peroxide, benzoyl peroxide, lauroyl peroxide, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, tert-butyl hydroperoxide, tert peracetate. -Peroxides such as butyl, tert-butyl perbenzoate, 2,2'-azobispropane, 1,1'-azo (methylethyl) diacetate, 2,2'-azobisisobutyramide, 2,2 An azo compound such as' -azobisisobutyronitrile, benzenesulfonyl azide, 1,4-bis (pentamethylene) -2-tetrazene and the like are preferably used. You may use these individually or in combination of 2 or more types.

  The plasticizer (D) has a function of softening the relief layer and needs to have good compatibility with the hydrophilic polymer (A). In general, a highly hydrophilic compound has good compatibility with a hydrophilic polymer. Among the highly hydrophilic compounds, for example, those having a structure in which a hydrophilic group and a hydrophobic group are alternately continued, such as an ether compound containing a hetero atom in a straight chain or a secondary amine, are preferably used. The presence of a hydrophilic group such as —O— or —NH— expresses compatibility with the hydrophilic polymer (A1), and other hydrophobic groups weaken the intermolecular force of the hydrophilic polymer (A1). This is to work for flexibility. Further, those having few hydroxyl groups capable of forming hydrogen bonds with the hydrophilic polymer (A1) are preferably used. Such compounds include ethylene glycol, propylene glycol, and dimers, trimers, and single and multimers of tetramers and higher, 2 such as diethanolamine and dimethylolamine. Secondary amines. Among these, ethylene glycols (monomers, dimers, trimers, and multimers) that have low steric hindrance, excellent compatibility, and low toxicity are particularly preferably used as the plasticizer (D).

  Ethylene glycols are roughly classified into three types according to their molecular weights. The first is ethylene glycol as a monomer, the second is diethylene glycol as a dimer and the triethylene glycol as a trimer, and the third is a polyethylene glycol having a tetramer or higher. Polyethylene glycol is often marketed under the name with an average molecular weight at the end, and is broadly classified into liquid polyethylene glycol having a molecular weight of 200 to 700 and solid polyethylene glycol having a molecular weight of 1000 or more.

  As a result of investigation, it was found that the lower the molecular weight of the plasticizer, the higher the effect of softening the resin. From this, ethylene glycol as the first group, diethylene glycol and triethylene glycol as the second group, and tetraethylene glycol (tetramer) included in the third group are particularly preferable. The plasticizers (D) that are preferably used are diethylene glycol, triethylene glycol, and tetraethylene glycol because they are low in toxicity, have no extraction from the resin composition, and are excellent in handleability. A mixture of two or more of these is also preferably used.

  The total content of the hydrophilic polymer (A1) and the hydrophilic polymer (A2) in the crosslinkable relief layer is preferably 30% by weight to 80% by weight, preferably 40% by weight based on the total solid content of the crosslinkable relief layer. -70 wt% is more preferred. By making the total content of components (A1) and (A2) 30% by weight or more, it is possible to prevent cold flow of the original plate, and by making it 80% by weight or less, other components may be insufficient. This is because printing durability sufficient for use as a relief printing plate can be obtained.

  The content of the hydrophilic polymer (A1) is preferably 15% by weight to 79% by weight and more preferably 30% by weight to 65% by weight with respect to the total solid content of the crosslinkable relief layer. By setting the content of component (A1) to 15% by weight or more, printing durability sufficient for use as a relief printing plate can be obtained, and by setting it to 79% by weight or less, other components are not deficient in flexo. This is because flexibility sufficient for use as a printing plate can be obtained.

  The content of the hydrophilic polymer (A2) is preferably 1% by weight to 15% by weight and more preferably 3% by weight to 10% by weight with respect to the total solid content of the crosslinkable relief layer. By setting the content of the component (A2) to 1% by weight or more, the hydrophilic polymer (A1) can be efficiently softened to obtain flexibility sufficient for use as a flexographic plate, and the component (A2) Due to its toughness characteristics, printing durability sufficient for use as a relief printing plate can be obtained, and by reducing the content to 15% by weight or less, the amount of sticky engraving residue from which the component (A2) is generated can be reduced. Can do.

  The content of the ethylenically unsaturated monomer (B) in the crosslinkable relief layer is preferably 10 wt% to 60 wt%, more preferably 15 wt% to 40 wt%, based on the total solid content of the crosslinkable relief layer. . When the content of component (B) is 10% by weight or more, printing durability sufficient for use as a relief printing plate is obtained, and when it is 60% by weight or less, flexibility sufficient for use as a flexographic printing plate is obtained. It is because it is obtained.

  The content of the polymerization initiator (C) in the crosslinkable relief layer is preferably 0.01% by weight to 10% by weight, and preferably 0.1% by weight to 3% by weight with respect to the total solid content of the crosslinkable relief layer. More preferred. When the content of the component (C) is 0.01% by weight or more, the crosslinkable relief layer is rapidly crosslinked, and when it is 10% by weight or less, other components are not insufficient, and the relief printing plate This is because the printing durability sufficient to be used as is obtained.

  The content of the plasticizer (D) in the crosslinkable relief layer is preferably 5% by weight to 40% by weight and more preferably 10% by weight to 25% by weight with respect to the total solid content of the crosslinkable relief layer. When the content of component (D) is 5% by weight or more, a flexible relief printing plate can be obtained, and when it is 40% by weight or less, other components are not deficient and used as a relief printing plate. This is because sufficient printing durability can be obtained.

  The crosslinkable relief layer can be obtained by forming the crosslinkable resin composition into a sheet shape or a sleeve shape.

  The material used for the support in the present invention is not particularly limited, but those that are dimensionally stable are preferably used. For example, metals such as steel, stainless steel, and aluminum, polyesters (for example, PET, PBT, PAN), and polyvinyl chloride. Examples thereof include plastic resins, synthetic rubbers such as styrene-butadiene rubber, and plastic resins reinforced with glass fibers (such as epoxy resins and phenol resins). As the support for the relief printing plate, a PET (polyethylene terephthalate) film or a steel substrate is preferably used. The form of the support is determined by whether the crosslinkable relief layer is in the form of a sheet or a sleeve.

  An adhesive layer may be provided between the crosslinkable relief layer and the support for the purpose of enhancing the adhesive force between the two layers. The material used for the adhesive layer may be any material that strengthens the adhesive force after the crosslinkable relief layer is crosslinked, and preferably has a strong adhesive force before the crosslinkable relief layer is crosslinked. . Here, the adhesive force means both the adhesive force between the support / adhesive layer and the adhesive layer / crosslinkable relief layer.

  The adhesive force between the support / adhesive layer is the peel force per 1 cm width of the sample when the adhesive layer and the crosslinkable relief layer are peeled from the laminate comprising the support / adhesive layer / crosslinkable relief layer at a rate of 400 mm / min. Is preferably 1.0 N / cm or more or non-peelable, and more preferably 3.0 N / cm or more or non-peelable.

  The adhesive strength of the adhesive layer / crosslinkable relief layer is that when the adhesive layer is peeled from the adhesive layer / crosslinkable relief layer at a rate of 400 mm / min, the peel force per 1 cm width of the sample is 1.0 N / cm or more or cannot be peeled off. It is preferable that it is 3.0N / cm or more, or more preferably non-peelable.

  The crosslinkable relief layer becomes a part where a relief is formed after crosslinking, and the relief surface functions as an ink deposit part. Since the relief layer after cross-linking is reinforced by cross-linking, scratches and dents that affect printing on the surface of the relief layer are hardly generated. However, the crosslinkable relief layer before cross-linking is often insufficient in strength, and the surface is likely to have scratches and dents. For the purpose of preventing scratches and dents on the surface of the crosslinkable relief layer, a protective film may be provided on the surface of the crosslinkable relief layer.

  If the protective film is too thin, the effect of preventing scratches and dents cannot be obtained. If the protective film is too thick, handling becomes inconvenient and the cost increases. Therefore, the thickness of the protective film is preferably 25 μm to 500 μm, and more preferably 50 μm to 200 μm.

  As the protective film, a known material as a protective film for a printing plate, for example, a polyester film such as PET (polyethylene terephthalate), or a polyolefin film such as PE (polyethylene) or PP (polypropylene) can be used. The surface of the film may be plain or matted.

  When providing a protective film on a crosslinkable relief, the protective film must be peelable. If the protective film cannot be peeled or is difficult to adhere to the crosslinkable relief layer, a slip coat layer may be provided between both layers.

  The material used for the slip coat layer is a resin that is soluble or dispersible in water, such as polyvinyl alcohol, polyvinyl acetate, partially saponified polyvinyl alcohol, hydroxyalkyl cellulose, alkyl cellulose, polyamide resin, etc. It is preferable that Among these, partially saponified polyvinyl alcohol having a saponification degree of 60 to 99 mol%, hydroxyalkyl cellulose having 1 to 5 carbon atoms in the alkyl group, and alkyl cellulose are particularly preferably used from the viewpoint of tackiness.

  When the protective film is peeled from the crosslinkable relief layer (and slip coat layer) / protective film at a speed of 200 mm / min, the peel force per 1 cm is preferably 5 to 200 mN / cm, and 10 to 150 mN / cm is Further preferred. If it is 5 mN / cm or more, it can work without peeling off the protective film during the work, and if it is 200 mN / cm or less, the protective film can be peeled without difficulty.

  Next, a method for obtaining a crosslinkable resin printing plate precursor for laser engraving (that is, a laminate of at least a support and a crosslinkable relief layer) will be described. Although it does not specifically limit, For example, after preparing the solution of the crosslinkable resin composition for laser engraving, removing a solvent from this solution, the method of melt-extruding on a support body is mentioned. Alternatively, a method of casting a solution of the crosslinkable resin composition for laser engraving on a support and drying it in an oven to remove the solvent from the solution may be used.

  Thereafter, a protective film may be laminated on the crosslinkable relief layer as necessary. Lamination can be performed by pressure-bonding the protective film and the crosslinkable relief layer with a heated calender roll or the like, or by bringing the protective film into close contact with the crosslinkable relief layer impregnated with a small amount of solvent on the surface.

  When using a protective film, a method of first laminating a crosslinkable relief layer on the protective film and then laminating the support may be employed.

  When providing an adhesive layer, it can respond by using the support body which apply | coated the adhesive layer. When providing a slip coat layer, it can respond by using the protective film which apply | coated the slip coat layer.

  The solution of the crosslinkable resin composition for laser engraving uses, for example, a hydrophilic polymer (A1) containing hydroxyethylene as a structural unit, a hydrophilic polymer (A2) other than (A1), and a plasticizer (D) in a suitable solvent. It can be prepared by dissolving and then dissolving the ethylenically unsaturated monomer (B) and the polymerization initiator (C). The solvent is preferably a mixed solvent of water and alcohol so that both the polymer component and the monomer component can be dissolved. Since most of the solvent components need to be removed at the stage of producing the original plate, it is preferable to use a low molecular alcohol (e.g., ethanol) that easily volatilizes and to keep the total amount of solvent added as small as possible. The amount of the solvent added can be suppressed by raising the temperature of the system, but if the temperature is too high, the monomer component (B) tends to undergo a polymerization reaction, so the solution preparation temperature is preferably 30 ° C to 80 ° C. .

  The crosslinkable resin printing plate precursor for laser engraving obtained as described above can produce a relief printing plate through the following steps in sequence.

  The first example includes (1a) a step of irradiating a crosslinkable resin printing plate precursor for laser engraving with actinic rays to crosslink the crosslinkable relief layer, and (2) a step of laser engraving the crosslinkable relief layer. Become.

  The second example includes (1b) a step of heating a crosslinkable relief printing layer for laser engraving to heat the crosslinkable relief layer, and (2) a step of laser engraving the crosslinked crosslinkable relief layer.

  Furthermore, you may include the following process as needed. Subsequent to step (2), (3) rinsing the engraved surface with water or a liquid containing water as a main component, (4) drying the engraved crosslinkable relief layer, and (5) a crosslinkable relief layer A step of further crosslinking.

  Step (1) is a step of crosslinking the crosslinkable relief layer portion of the crosslinkable resin printing plate precursor for laser engraving. The crosslinkable relief layer of the present invention comprises a hydrophilic polymer (A), an ethylenically unsaturated monomer (B), a polymerization initiator (C) and a plasticizer (D), and step (1) is a polymerization initiator. This is a step of polymerizing the ethylenically unsaturated monomer (B) by the action of (C). The polymerization initiator (C) is a radical generator, and the trigger for generating radicals is roughly classified into a photopolymerization initiator and a thermal polymerization initiator depending on light or heat.

  When the crosslinkable relief layer contains a photopolymerization initiator, the crosslinkable relief layer can be crosslinked by irradiating the crosslinkable relief layer with an actinic ray that triggers the photopolymerization initiator. The irradiation with actinic rays is generally performed on the entire crosslinkable relief layer. Visible light, ultraviolet light, or an electron beam is mentioned as actinic light, but ultraviolet light is the most common. If the support side of the crosslinkable relief layer is the back side, the surface may only be irradiated with actinic rays. However, if the support is a transparent film that transmits actinic rays, it is preferable to irradiate the back side with actinic rays. . When the protective film is present, the exposure from the surface may be performed while the protective film is provided, or may be performed after the protective film is peeled off. Since polymerization inhibition occurs in the presence of oxygen, the crosslinkable relief layer may be covered with a vinyl chloride sheet and evacuated and then irradiated with actinic rays.

  When the crosslinkable relief layer contains a thermal polymerization initiator, the crosslinkable relief layer can be crosslinked by heating the crosslinkable resin printing plate precursor for laser engraving. Examples of the heating means include a method of leaving the original plate in a hot air oven or a far infrared oven for a predetermined time, or a method of contacting a heated roll for a predetermined time.

  In the step (1a) using light, although an apparatus for irradiating actinic rays is relatively expensive, there is almost no restriction on the material as a raw material of the original because the original does not become high temperature. The step (1b) using heat has an advantage that an extra expensive apparatus is not required, but since the original plate becomes high temperature, the thermoplastic polymer that becomes flexible at high temperature may be deformed during heating. The raw materials to be used must be carefully selected.

  By crosslinking the crosslinkable relief layer, there is an advantage that firstly the relief formed after laser engraving becomes sharp, and secondly, the adhesiveness of engraving residue generated during laser engraving is suppressed. When an uncrosslinked crosslinkable relief layer is laser engraved, unintended portions are easily melted and deformed due to residual heat propagated around the laser irradiated portion, and a sharp relief cannot be obtained. In addition, as a general property of a material, a material having a low molecular weight becomes liquid rather than solid, that is, the adhesiveness becomes strong. The engraving residue generated when engraving the crosslinkable relief layer becomes more tacky as more low molecular weight materials are used. Since the ethylenically unsaturated monomer (B), which is a low molecule, becomes a polymer by crosslinking, the generated engraving residue tends to be less tacky.

  The Shore A hardness of the crosslinkable relief layer after crosslinking is preferably 50 ° to 90 °. By using a relief layer having a Shore A hardness of 50 ° or more, even if a fine halftone dot formed by engraving is subjected to a strong printing pressure of a relief printing press, it does not collapse and can be printed normally. By using a relief layer having a Shore A hardness of 90 ° or less, it is possible to prevent faint printing in a solid portion even in flexographic printing with a kiss touch.

  (2) The step of laser engraving the crosslinkable relief layer is a step of scanning the crosslinkable relief layer by controlling the laser head with a computer based on the digital data of the image to be formed. . When irradiated with an infrared laser, the molecules in the crosslinkable relief layer undergo molecular vibrations and generate heat. When a high-power laser such as a carbon dioxide laser or YAG laser is used as an infrared laser, a large amount of heat is generated in the laser irradiation area, and molecules in the crosslinkable relief layer are selectively removed by molecular cutting or ionization. That is, a sculpture is made. The advantage of laser engraving is that the engraving depth can be set arbitrarily, so that the structure can be controlled three-dimensionally. For example, the relief can be prevented from falling by printing pressure by engraving with a shallow or shoulder on the part where fine halftone dots are printed, and the groove part where fine cut characters are printed should be engraved deeply. Therefore, it becomes difficult for the ink to be buried in the groove, and it is possible to suppress the crushing of the extracted characters.

  When the engraving residue adheres to the engraving surface, a step (3) of rinsing the engraving surface with water or a liquid containing water as a main component and washing away the engraving residue may be added. As a means for rinsing, a method of spraying high-pressure water, a method of brushing the engraved surface mainly in the presence of water with a known batch-type or transport-type brush-type washing machine as a photosensitive resin letterpress developing machine, etc. If the engraving residue cannot be removed, a rinsing solution to which soap is added may be used.

  When the step (3) of rinsing the engraved surface is performed, it is preferable to add a step (4) of drying the engraved crosslinkable relief layer and volatilizing the rinse liquid.

  Furthermore, you may add the process (5) which further bridge | crosslinks a crosslinkable relief layer as needed. By performing the additional crosslinking step (5), the relief formed by engraving can be further strengthened.

  The relief printing plate produced by the production method of the present invention can be printed with oil-based ink or UV ink by a relief printing machine, and can also be printed with UV ink by a flexographic printing machine.

  Hereinafter, the present invention will be described in detail with reference to examples.

<Preparation of a support coated with an adhesive layer>
70 parts by weight of “Byron” 31SS (toluene solution of unsaturated polyester resin, manufactured by Toyobo Co., Ltd.) and 2 parts by weight of “PS-8A” (benzoin ethyl ether, manufactured by Wako Pure Chemical Industries, Ltd.) The mixture was heated at 30 ° C. for 2 hours and then cooled to 30 ° C., and 7 parts by weight of ethylene glycol diglycidyl ether dimethacrylate was added and mixed for 2 hours. Further, 25 parts by weight of “Coronate” 3015E (ethyl acetate solution of polyvalent isocyanate resin, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 14 parts by weight of “EC-1368” (industrial adhesive, manufactured by Sumitomo 3M Co., Ltd.) This was added to obtain a coating solution composition for the first adhesive layer.

  50 parts by weight of “Gohsenol” KH-17 (polyvinyl alcohol having a saponification degree of 78.5% to 81.5%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) is mixed with “Solmix” H-11 (alcohol mixture, Nippon Alcohol Co., Ltd.). )) 200 parts by weight and 200 parts by weight of water After dissolving at 70 ° C. for 2 hours, 1.5 parts by weight of “Blenmer” G (glycidyl methacrylate, manufactured by NOF Corporation) was added to After mixing for a while, 3 parts by weight of (dimethylaminoethyl methacrylate) / (2-hydroxyethyl methacrylate) / (methacrylic acid) copolymer (copolymerization ratio: 67/32/1), “Irgacure” 651 (benzyldimethyl ketal) Ciba Geigy Co., Ltd.) 5 parts by weight, “epoxy ester” 70PA (propylene glycol diglycidyl ether acrylic) 21 parts by weight of a phosphoric acid adduct (manufactured by Kyoeisha Chemical Co., Ltd.) and 20 parts by weight of ethylene glycol diglycidyl ether dimethacrylate were added and mixed for 90 minutes. After cooling to 50 ° C., “Florard” TM FC-430 (Sumitomo 3M) 0.1 part by weight was added and mixed for 30 minutes to obtain a coating solution composition for the second adhesive layer.

  The coating liquid composition for the first adhesive layer was applied on a “Lumirror” T60 (polyester film, manufactured by Toray Industries, Inc.) having a thickness of 250 μm used as a support with a bar coater so that the film thickness after drying was 40 μm. Then, after removing the solvent by placing it in an oven at 180 ° C. for 3 minutes, a coating solution composition for the second adhesive layer is applied on the bar coater so that the dry film thickness is 30 μm. The laminate was dried for 3 minutes to obtain a laminate of the second adhesive layer / first adhesive layer / support.

<Preparation of protective film coated with slip coat layer>
“GOHSENOL” AL-06 (polyvinyl alcohol having a saponification degree of 91% to 94%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 4 parts by weight 55 parts by weight of water, 14 parts by weight of methanol, 10 parts by weight of n-propanol and n- Butanol was dissolved in 10 parts by weight of a mixed solvent to obtain a coating liquid composition for a slip coat layer.

  On the polyester film “Lumirror” S10 (manufactured by Toray Industries, Inc.) having a thickness of 100 μm, the above coating composition for the slip coat layer was applied using a bar coater so that the dry film thickness was 1.0 μm. And dried at 100 ° C. for 25 seconds to obtain a laminate of a slip coat layer / protective film.

<Synthesis of hydrophilic polyamide resin 1>
10 parts by weight of ε-caprolactam, 90 parts by weight of N- (2-aminoethyl) piperazine and nylon salt of adipic acid and 100 parts by weight of water were placed in a stainless steel autoclave, and the internal air was replaced with nitrogen gas at 180 ° C. Heating was carried out for 1 hour, then water was removed, and a hydrophilic polyamide resin 1 having a relative viscosity (1 g of polymer dissolved in 100 ml of chloral hydrate and measured at 25 ° C.) of 2.50 was obtained.

<Synthesis of hydrophilic polyamide resin 2>
60 parts by weight of an equimolar salt of α, ω-diaminopolyoxyethylene and adipic acid obtained by adding acrylonitrile to both ends of polyethylene glycol having a number average molecular weight of 600 and reducing it with hydrogen, 20 parts by weight of ε-caprolactam and 20 parts by weight of an equimolar salt of hexamethylenediamine and adipic acid is melt-polymerized to obtain a hydrophilic polyamide resin 2 having a relative viscosity (viscosity of 1 g of polymer dissolved in 100 ml of chloral hydrate and measured at 25 ° C.) of 2.50. Obtained.

<Synthesis of modified polyvinyl alcohol>
In a flask equipped with a condenser, partially saponified polyvinyl alcohol “GOHSENOL” KL-05 (degree of saponification 78.5% to 82.0%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 50 parts by weight, succinic anhydride 2 After adding 10 parts by weight of acetone and 10 parts by weight of acetone and heating at 60 ° C. for 6 hours, the cooling tube was removed to volatilize the acetone, followed by a purification step of eluting unreacted succinic anhydride with 100 parts by weight of acetone. After performing twice, it dried under reduced pressure at 60 degreeC for 5 hours, and obtained the modified polyvinyl alcohol which the succinic acid ester-bonded to the hydroxyl group.

<Example 1>
In a three-necked flask equipped with a stirring spatula and a condenser tube, 5 parts by weight of the hydrophilic polyamide resin 1 as a hydrophilic polymer (A2) and 45 parts by weight of the modified polyvinyl alcohol as a polymer (A1) 20 parts by weight of diethylene glycol as an agent (D), 35 parts by weight of water and 12 parts by weight of ethanol as a solvent were added and heated at 70 ° C. for 120 minutes with stirring to dissolve the polymer. Subsequently, 3 parts by weight of “Blemmer” G (glycidyl methacrylate, manufactured by Nippon Oil & Fats Co., Ltd.) was added and stirred at 70 ° C. for 30 minutes. At this stage, the reaction between the epoxy group of “Blemmer” G and the carboxyl group of the modified polyvinyl alcohol is almost completed, and a methacryl group is added to the polymer side chain. Further, as the ethylenically unsaturated monomer (B), 4 parts by weight of “Blenmer” GMR (methacrylic acid adduct of glycidyl methacrylate, manufactured by Nippon Oil & Fats Co., Ltd.), “Light acrylate” 14EG-A (polyacrylate glycol 600 diacrylate, 1 part by weight of Kyoeisha Chemical Co., Ltd., 5 parts by weight of “epoxy ester” 70PA (acrylic acid adduct of propylene glycol diglycidyl ether, Kyoeisha Chemical Co., Ltd.), “Blemer PE” 200 (average molecular weight 200) 15 parts by weight of polyethylene glycol methacrylate (Nippon Yushi Co., Ltd.), 0.1 parts by weight of “Irgacure” 651 (benzyldimethyl ketal, manufactured by Ciba Geigy Co., Ltd.) as the polymerization initiator (C), "Irgacure" 184 (α-hydroxyketone, Ciba Geigy ( )), 1.5 parts by weight as an antifoaming agent, 0.05 parts by weight as a defoaming agent (manufactured by San Nopco), and "Q-1300" (ammonium N-nitrosophenylhydroxylamine) as a polymerization inhibitor , Wako Pure Chemical Industries, Ltd.) was added and stirred for 30 minutes to obtain a solution of a crosslinkable resin composition for laser engraving for a flowable crosslinkable relief layer 1.

<Example 2>
In Example 1 above, the crosslinkable resin composition for laser engraving for the flowable crosslinkable relief layer 2 was prepared in the same procedure except that tetraethylene glycol was used instead of diethylene glycol as the plasticizer (D). A product solution was obtained.

<Example 3>
In Example 1, the same procedure was used except that “PEG # 400” (polyethylene glycol having an average molecular weight of 380 to 420, manufactured by Lion Corporation) was used instead of diethylene glycol as the plasticizer (D). A solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layer 3 having fluidity was obtained.

<Example 4>
In a three-necked flask equipped with a stirring spatula and a condenser tube, 5 parts by weight of the hydrophilic polyamide resin 1 as a polymer (A2), 48 parts by weight of the modified polyvinyl alcohol as a polymer (A1), and a plasticizer ( As D), 20 parts by weight of diethylene glycol, 35 parts by weight of water and 12 parts by weight of ethanol were added as solvents, and the mixture was heated at 70 ° C. for 120 minutes with stirring to dissolve the polymer. Furthermore, as the ethylenically unsaturated monomer (B), 4 parts by weight of “Blenmer” GMR (methacrylic acid adduct of glycidyl methacrylate, manufactured by NOF Corporation), “Light acrylate” 14EG-A (polyacrylate glycol 600 diacrylate, 1 part by weight of Kyoeisha Chemical Co., Ltd., 5 parts by weight of “epoxy ester” 70PA (acrylic acid adduct of propylene glycol diglycidyl ether, Kyoeisha Chemical Co., Ltd.), “Blemmer” PE200 (average molecular weight 200) 15 parts by weight of polyethylene glycol methacrylate (Nippon Yushi Co., Ltd.), 0.1 parts by weight of “Irgacure” 651 (benzyldimethyl ketal, Ciba Geigy Co., Ltd.) as the polymerization initiator (C), “Irgacure "184 (α-hydroxyketone, Ciba Geigy ( )), 1.5 parts by weight as a defoaming agent, 0.05 parts by weight (manufactured by San Nopco Co., Ltd.), and "Q-1300" (ammonium N-nitrosophenylhydroxylamine) as a polymerization inhibitor , Wako Pure Chemical Industries, Ltd.) was added and stirred for 30 minutes to obtain a solution of a crosslinkable resin composition for laser engraving for a flowable crosslinkable relief layer 4.

<Example 5>
In a three-necked flask equipped with a stirring spatula and a condenser tube, 5 parts by weight of the hydrophilic polyamide resin 1 as a polymer (A2), 45 parts by weight of the modified polyvinyl alcohol as a polymer (A1), and a plasticizer ( As D), 20 parts by weight of diethylene glycol, 35 parts by weight of water and 27 parts by weight of ethanol were added and heated at 70 ° C. for 120 minutes with stirring to dissolve the polymer. Subsequently, 3 parts by weight of “Blemmer” G (glycidyl methacrylate, manufactured by Nippon Oil & Fats Co., Ltd.) was added and stirred at 70 ° C. for 30 minutes. At this stage, the reaction between the epoxy group of “Blemmer” G and the carboxyl group of the modified polyvinyl alcohol is almost completed, and a methacryl group is added to the polymer side chain. After cooling the flask temperature to 40 ° C., 4 parts by weight of “Blenmer” GMR (methacrylic acid adduct of glycidyl methacrylate, manufactured by NOF Corporation) as the ethylenically unsaturated monomer (B), “light acrylate” 14EG- 1 part by weight of A (diacrylate of polyethylene glycol 600), 5 parts by weight of “epoxy ester” 70PA (acrylic acid adduct of propylene glycol diglycidyl ether, manufactured by Kyoeisha Chemical Co., Ltd.), “Blenmer” PE200 (average molecular weight) 15 parts by weight of 200 polyethylene glycol methacrylate (Nippon Yushi Co., Ltd.), 1 part by weight of “Nyper” BW (benzoyl peroxide, made by NIPPON OIL Co., Ltd.) as a polymerization initiator (C), antifoaming agent "Formaster" (San Nopco Co., Ltd.) 0.05 parts by weight, and polymerization "Q-1300" (ammonium N-nitrosophenylhydroxylamine, manufactured by Wako Pure Chemical Industries, Ltd.) as a stop agent is added in an amount of 0.005 parts by weight and stirred for 30 minutes. A solution of a crosslinkable resin composition for laser engraving was obtained.

<Comparative Example 1>
In Example 1 above, the hydrophilic polyamide resin 1 as the polymer (A2) was not added, and the addition amount of the modified polyvinyl alcohol as the polymer (A1) was changed from 45 parts by weight to 50 parts by weight. A solution of a crosslinkable resin composition for laser engraving for a crosslinkable relief layer 6 having fluidity was prepared by the procedure.

<Comparative example 2>
In a three-necked flask equipped with a stirring spatula and a condenser tube, 50 parts by weight of the above hydrophilic polyamide resin 2 as a polymer (A2), 20 parts by weight of diethylene glycol as a plasticizer (D), and 14 parts by weight of water as a solvent And 34 parts by weight of ethanol were added and heated at 70 ° C. for 120 minutes with stirring to dissolve the polymer. Next, 3 parts by weight of “Blemmer” G was added and stirred at 70 ° C. for 30 minutes. At this stage, the reaction between the epoxy group of “Blemmer” G and —NH— in the amide group of the hydrophilic polyamide resin 2 is completed, and a methacryl group is added to the polymer. Furthermore, 4 parts by weight of “Blenmer” GMR as an ethylenically unsaturated monomer, 1 part by weight of “light acrylate” 14EG-A (diacrylate of polyethylene glycol 600), 5 parts by weight of “epoxy ester” 70PA, “Blenmer” PE200 15 parts by weight, “Irgacure” 651 as polymerization initiator (C), 0.1 parts by weight, “Irgacure” 184, 1.5 parts by weight, “Formaster” as defoaming agent, 0.05 parts by weight, and As a polymerization inhibitor, 0.005 part by weight of “Q-1300” was added and stirred for 30 minutes to obtain a solution of a crosslinkable resin composition for laser engraving for a flowable crosslinkable relief layer 7.

<Comparative Example 3>
In Comparative Example 2, the same procedure was used except that the hydrophilic polyamide resin 1 was used in place of the hydrophilic polyamide resin 2 as the hydrophilic polymer (A2), and the flowable crosslinkable relief layer 8 was used. A solution of a crosslinkable resin composition for laser engraving was obtained.

<Example 6>
After the support coated with the adhesive layer is exposed to 1000 mJ / cm ² from the adhesive layer side with an ultra-high pressure mercury lamp, the adhesive layer is coated with a solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layer 1. Casted to the adhesive layer side of the support, dried in an oven at 60 ° C. for 2 hours, and including the substrate, a crosslinkable relief layer having a thickness of approximately 1100 μm 1 / second adhesive layer / first adhesive layer / support The crosslinkable resin sheet 1 which is a laminated body was obtained. The surface of the obtained crosslinkable relief layer 1 has almost no adhesion and is easy to handle. The thickness of the crosslinkable resin sheet 1 was controlled by installing a spacer having a predetermined thickness on the second adhesive layer, and scraping out the crosslinkable resin composition at a portion protruding from the spacer with a horizontal metal scale.

  Between the crosslinkable resin sheet 1 and the protective film coated with the slip coat layer, a solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layer 1 was developed and heated to 80 ° C. Laminating with a calender roll, crosslinkable resin printing plate precursor 1 for laser engraving (hereinafter referred to as “protective film / slip coat layer / crosslinkable relief layer 1 / second adhesive layer / first adhesive layer / support”) An original 1) was obtained. The clearance of the calender roll was adjusted so that the thickness of the laminate after peeling the protective film from the original plate 1 was 1140 μm. The developed coating liquid composition is allowed to stand for 1 week after lamination, whereby the remaining solvent is diffused or naturally dried to form an additional crosslinkable relief layer 1.

<Examples 7 to 10 and Comparative Examples 4 to 5>
In Example 6 above, the solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layer 1 was changed to the solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layers 2 to 7, respectively. All of the crosslinkable resin sheets 2 to 7 were obtained in the same procedure. The surfaces of the obtained crosslinkable relief layers 2 to 7 have almost no adhesion and are easy to handle.
Then, in Example 6, laser engraved crosslinkable resin printing plate precursors 2 to 7 (hereinafter referred to as the original plate) were all carried out in the same procedure except that crosslinkable resin sheets 2 to 7 were used in place of the crosslinkable resin sheet 1, respectively. 2-7) were obtained respectively.

<Comparative Example 6>
In Example 6 above, the same applies except that the solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layer 1 is changed to the solution of the crosslinkable resin composition for laser engraving for the crosslinkable relief layer 8. Although the crosslinkable resin sheet 8 was produced according to the procedure, the obtained sheet surface had strong adhesion and could not be used. This is because the hydrophilic polyamide resin 1 has a property of easily absorbing moisture.

<Examples 11-15, Comparative Examples 7-8>
(1a) Step of photocrosslinking the crosslinkable relief layer After peeling off the protective films from the original plates 1 to 4 and 6 to 7, respectively, the protective film is peeled off with an ultrahigh pressure mercury lamp (manufactured by Oak Co., Ltd.) having a light source in the ultraviolet region The entire surface was exposed from the side (exposure amount: 4000 mJ / cm ² ), and the crosslinkable relief layers 1 to 4 and 6 to 7 were photocrosslinked.

(1b) Step of thermally crosslinking the crosslinkable relief layer The original plate 5 was heated in a hot air oven set at 110 ° C. for 10 hours to thermally crosslink the crosslinkable relief layer 5. Thereafter, the protective film was peeled off.

(2) Step of Laser Engraving Crosslinked Crosslinkable Relief Layer The engraved machine “Zed mini 1000” (manufactured by Luescher ZED Flexo Ltd.) equipped with a carbon dioxide laser with an output of 250 W is used for the above-mentioned crosslinked original plate 1 7 were mounted so that their support sides were in contact with the outer drum of the engraving machine, and a relief pattern (having a solid portion and a 1% to 99% halftone dot portion) with a resolution of 150 LPI (lines per inch) was engraved. The engraving setting conditions were unified as shoulder width: 0.30 mm, Top Power: 10%, Bottom Power: 100%, and drum surface speed: 300 cm / s. In all the plates, engraving residue was attached to the plate surface. The engraving residue adhering to the obtained engraving plates 1 to 6 was solid and hardly sticky, but the engraving residue adhering to the engraving plate 7 was liquid and strongly sticky. This is because hydrophilic polyamide has a property of generating liquid residue by engraving. Since the liquid engraving residue contaminates the condenser lens of the carbon dioxide laser, when engraving the original plate 7, it is necessary to care for the condenser lens frequently.

(3) Rinsing the engraving surface with water In order to remove engraving residue adhering to the engraving plate, the engraving surface was rinsed with water. Rinse can be done by washing the plate surface with water on the washstand, but it is sufficient to perform rinsing evenly and quickly, and to prevent mixing into the sewer of engraving waste. Washing was carried out for 10 seconds using a machine “FTW430II” (Braj type developing machine equipped with nylon brush, manufactured by Toray Industries, Inc.) (water temperature: 25 ° C.). In this step, the upper slip coat layer of the crosslinkable relief layer is removed. It was confirmed that the engraving residue was removed from any engraving plate.

(4) Step of drying the engraved relief layer In order to remove the water adhering to the water-rinsed engraving plate, it was dried for 10 minutes in a hot air oven heated to 60 ° C.

  Relief printing plates 1 to 7 were obtained through the steps (1a) or (1b) to (4). The relief depth of these engraving plates was about 200 μm to 320 μm.

  Next, the characteristics of the obtained relief printing plate were evaluated. The evaluation results are shown in Tables 1 and 2.

(Measurement of Shore A hardness)
The solid portion of the relief printing plates 1 to 7 (the portion where the relief layer was crosslinked and not engraved) was cut out, and the substrate and the adhesive layer were peeled from the relief printing plate to isolate the crosslinkable relief layer. . Eight isolated crosslinkable relief layers were stacked and the hardness was measured with a Shore A hardness meter. The measurement sample was stored for 24 hours at 25 ° C. in a desiccator and then used for measurement. By changing the plasticizer from medium molecular weight ethylene glycol 400 to low molecular weight diethylene glycol, it was found that the Shore A hardness of 91 ° was softened to 75 ° (comparison of relief printing plates 3 and 1). ). It was found that a polymer having a Shore A hardness of 87 ° was softened to 75 ° by using a mixture of the modified polyvinyl alcohol and water-soluble polyamide instead of the modified polyvinyl alcohol alone (relief printing plate 6). And 1).

(Water resistance evaluation of relief printing plates)
When 50% relief of the halftone dots of the relief printing plates 1 to 7 was confirmed with an optical microscope, it was confirmed that a part of the relief surface of the relief printing plate 4 was dissolved in water. On the other hand, in the relief printing plates 1 to 3 and 5 to 7, it was confirmed that the relief was firmly formed and the relief layer exhibited sufficient resistance against water rinsing. This is because the polymer (A1) or (A2) itself has crosslinkability by adding glycidyl methacrylate as a monomer to the modified polyvinyl alcohol (A1) or hydrophilic polyamide resin (A2) which is a water-soluble polymer, This is because the polymer was changed from water-soluble to water-insoluble by crosslinking. The addition of the monomer to the polymer (A) not only improves the water resistance but also improves the printing durability accompanying the improvement of the crosslinking degree of the relief layer, and thus contributes to the formation of engraving halftone dots described below.

(Check engraving halftone dots)
When the halftone dot portion of the relief printing plate was confirmed with an optical microscope, it was confirmed that a 3% halftone dot of 150 LPI was formed in the relief printing plates 1 to 3 and 5 to 7, but in the relief printing plate 4 3% halftone dots were not formed. This is because the crosslinking density of the relief layer is improved by the monomer addition to the polymer (A).

(Evaluation of printability)
In the relief printing plates 1 to 7, the single resin is water-soluble and resistant to oil components, so printing with UV ink or oil-based ink by a relief printing machine is possible. However, the relief printing plate 6 showed a lack of relief in a part of a 3% halftone dot of 150 LPI at the time of 100,000 label printing. This is because only the polymer component (A1) is used as the polymer component of the crosslinkable relief layer, and the polyamide resin (A2) having tough performance is not used. On the other hand, the relief printing plates 1 to 7 are not resistant to water-based inks often used in flexographic printing because the relief layer swells and deforms, but flexographic printing with UV inks that do not contain a substantial solvent is possible. It is. Therefore, flexographic printing was performed with a UV ink “BestCure Indigo UV Flexo SP” (Indigo Ink, manufactured by T & K TOKA) using a flexographic printing machine “MA-830” (manufactured by Mark Andy). A cushion tape having a thickness of 0.38 mm was used for attaching the relief printing plate to the plate cylinder.

  Relief printing plates 1, 2, 4 and 5 having a Shore A hardness of 80 ° or less produced good prints without fading of the solid portion, but the relief printing plates 3, 6 and 7 having a Shore A hardness of 85 ° or more were obtained. Somewhat faint was seen in the solid part. This is because, since the printing plate is hard, the printing plate is not easily deformed by kiss touch, and a slight thickness variation of the printing plate surface in the solid portion is reflected in the printed matter as it is. Since the elements related to the plate cylinder and the cushion tape affect the variation of the printing plate surface, it is difficult for the flexographic printing plate with high hardness to eliminate the blurring of the solid portion only by improving the thickness accuracy. Relief printing plates 3, 6 and 7 which are relatively hard as flexographic plates were able to eliminate blurring of the solid portion by applying excessive printing pressure.

(Evaluation of printed matter)
The halftone dot density of the printed matter obtained by the flexographic printing was measured with a portable digital halftone dot measuring device “PrintDot” (manufactured by X-Rite). For the relief printing plates 1 to 6, the dot gain indicating the degree of dot thickness was 0 to 6%, and it was confirmed that the printing finish was very beautiful. The relief printing plate 7 had a dot gain of 3 to 10%, which was slightly thicker than the relief printing plates 1 to 6 containing a large amount of the polymer (A1) component. The flexographic plate is reproduced with a printed material from the halftone dots reproduced with the printing plate, but tends to be thicker, but the printing plates 1 to 6 obtained by this engraving are hardly thickened. When the halftone dot diameter of the halftone dot 50% (150 LPI) portion of the relief printing plate 1 was observed and measured, a halftone dot relief of 42% was formed on the printing plate (halftone dot diameter: 120 μm). The halftone dot density of the printed material is 52%, and the halftone dot equivalent to the output original is reproduced (dot gain in this case is 2%). In other words, the relief printing plate 1 is automatically engraved with a slightly smaller halftone dot relief at the stage of engraving, the “thickness” characteristic of the relief printing plate occurs at the stage of flexographic printing, and the printed material is a halftone dot of the original. And almost the same print. On the other hand, in the relief printing plate 7 in which the crosslinkable relief layer does not contain the polymer component (A1), a halftone dot (halftone dot diameter: 130 μm) is formed on the printing plate, and the halftone dot density of the printed matter. Is 57% (dot gain is 7%), and the finished print is slightly dark.

<Comparative Examples 9-15>
For the above original plates 1 to 7, (1) without undergoing the step of crosslinking the crosslinkable relief layer, (2) the step of laser engraving, (3) the step of rinsing the engraving plate surface with water, and (4) drying the rinse water The process of performing was performed sequentially. Since the crosslinkable relief layer was uncrosslinked, the crosslinkable relief layer was not dissolved in step (3), and a relief could not be formed.

<Comparative Examples 16-22>
For the original plates 1 to 7, (2) laser engraving step, (1) cross-linking the crosslinkable relief layer, (3) rinsing the engraving plate surface with water, and (4) drying the rinsing water sequentially went. Since the crosslinkable relief layer was engraved by laser engraving without being crosslinked, the obtained relief shape was not sharp and constant. Further, since the cross-linking step (1) was performed with the engraving residue remaining on the plate surface, the engraving residue adhered to the plate surface, and the engraving residue could not be completely removed in the rinsing step (3).

<Comparative Example 23>
About the water-developable photosensitive flexographic printing plate precursor “Treflex” LT114HR (manufactured by Toray Industries, Inc.) After exposure for 1 minute from the support side of the original plate with a developing device with an exposure unit, manufactured by Fuji Photo Film Co., Ltd., the protective film is peeled off from the original plate, and an ultraviolet light permeable PVC sheet is placed on the peeled surface. The bisheet and the original plate were brought into vacuum contact, and the original plate was exposed for 15 minutes through the vinyl chloride sheet to crosslink the photosensitive rubber layer (corresponding to a crosslinkable relief layer). (2) In the same manner as in Example 11, when the crosslinked rubber layer was laser engraved, liquid and highly sticky engraving residue adhered to the plate surface. (3) In the step of rinsing the engraving plate surface with water, the engraving residue was sticky and therefore could not be removed only by washing with water, but could be removed by brushing the plate surface with soapy water. This is because the synthetic rubber which is a polymer component of LT114HR is insoluble in water. (4) After the engraving plate was dried, (5) the engraved surface was exposed with the above-mentioned “FTW350LII” for 10 minutes to additionally crosslink the photosensitive rubber layer. Further, between step (4) and step (5), exposure is performed for 10 minutes with a germicidal lamp having a light emitting region in UVC, and a detack treatment is performed to reduce the adhesiveness of the engraved layer surface.

  Since the relief layer of LT114HR is mainly composed of a rubber component, it is not resistant to oil-based inks and is not suitable for letterpress printing machines. On the other hand, since it has high resistance to water-based inks and UV inks, and the Shore A hardness of the crosslinkable relief layer is 65 °, it is highly suitable for flexographic printing.

  Similarly to Example 11, when the engraved LT114HR was printed with a flexographic printing machine, a printed material without fading at the solid portion was obtained. When the halftone dot density of the printed material was measured with a portable digital halftone dot measuring device “PrintDot” (manufactured by X-Rite), the dot gain indicating the degree of dot thickness was 10 to 20%, which is compared with Examples 11 to 15 As a result, the halftone dots were significantly thicker. When the halftone dot diameter of the LT114HR engraving plate was observed and measured at a halftone dot 50% (150 LPI) portion, a halftone dot relief (halftone dot diameter: 135 μm) was formed on the printing plate. The halftone dot density of the printed material is 66%, and fatness occurs at the printing stage. In other words, the LT114HR is engraved with a halftone relief that faithfully reproduces the laser output data, but at the flexographic printing stage, the “thickness” characteristic of the relief printing plate occurs, and the printed matter is considerably larger than the original halftone dot. The print is dark (dark). Therefore, it is necessary to correct the data for controlling the laser engraving so that the engraving is excessively performed in advance.

Claims (9)

Contains hydrophilic polymer (A1) containing hydroxyethylene as a structural unit, hydrophilic polymer (A2) other than (A1), ethylenically unsaturated monomer (B), polymerization initiator (C) and plasticizer (D) A crosslinkable resin composition for laser engraving. The crosslinkable resin composition for laser engraving according to claim 1, wherein the hydrophilic polymer (A2) contains a hydrophilic polyamide. The crosslinkable resin composition for laser engraving according to claim 1, wherein the plasticizer (D) contains diethylene glycol, triethylene glycol, tetraethylene glycol, or a mixture thereof. The hydrophilic polymer (A1) containing hydroxyethylene as a structural unit contains partially saponified polyvinyl alcohol or partially saponified polyvinyl alcohol obtained by modifying at least a part of hydroxyl groups to carboxyl groups. Crosslinkable resin composition for laser engraving. The hydrophilic polymer (A1) containing hydroxyethylene as a structural unit contains a reaction product of partially saponified polyvinyl alcohol in which at least a part of a hydroxyl group is modified with a carboxyl group and a glycidyl group-containing ethylenically unsaturated monomer. The crosslinkable resin composition for laser engraving according to claim 1. A crosslinkable resin printing plate precursor for laser engraving comprising at least a support and a crosslinkable relief layer comprising the crosslinkable resin composition for laser engraving according to claim 1. At least (1a) a step of irradiating the crosslinkable resin printing plate precursor for laser engraving according to claim 6 with an actinic ray to crosslink the crosslinkable relief layer, and (2) a step of laser engraving the crosslinkable relief layer. A method for producing a relief printing plate comprising A relief comprising at least (1b) a step of crosslinking the crosslinkable relief layer by heating the crosslinkable resin printing plate precursor for laser engraving according to claim 6; and (2) a step of laser engraving the crosslinked crosslinkable relief layer. A method for producing a printing plate. The relief printing plate produced by the method according to claim 7 or 8, wherein the Shore A hardness is 50 ° to 90 °.