JP2008105429A - Manufacturing method of printing plate and removal method of razor engraving tails - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for not only easily safely removing powdery and viscous liquid engraving tails which is generated when a relief image is manufactured by direct laser engraving and can be easily safely removed, and also to provide a method for removal of the laser engraving tails. <P>SOLUTION: The method for manufacturing the printing plate and the method for removing the laser engraving tails are featured by containing processes of: preparing a sheet like printing original plate by optically building a photosensitive resin composition; preparing the printing plate by irradiating laser beams on the printing original plate to form a purpose pattern; and brushing the surface of the obtained printing plate in a water series developing on a surface of the obtained printing plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention forms an image pattern by irradiating a laser engraving printing original plate suitable for forming a relief image for a flexographic printing plate by laser engraving, forming a pattern for surface processing such as embossing, and forming a relief image for printing such as a tile. The present invention relates to a method for producing a printing plate, and a method for removing powdery and viscous liquid engraving residue generated in the process and remaining on the surface of the printing plate.

  Flexographic printing used for packaging materials such as cardboard, paper containers, paper bags, flexible packaging films, wallpaper materials, decorative materials such as decorative boards, and label printing has increased its specific gravity among various printing methods. For the production of the printing plate used for this, a photosensitive resin is usually used, and a liquid resin or a solid resin plate formed into a sheet shape is used, a photomask is placed on the photosensitive resin, and the mask is used. A method of irradiating light through the substrate to cause a crosslinking reaction and then washing off the non-crosslinked portion with a developer has been used. In recent years, a thin light-absorbing layer called a black layer has been provided on the surface of a photosensitive resin, and this is irradiated with laser light to form a mask image directly on the photosensitive resin plate. Later, a technique called so-called flexo CTP was developed in which the non-crosslinked portion of the light non-irradiated portion was washed away with a developing solution, and its adoption has been progressing from the effect of improving the printing plate production efficiency. However, this technique also has a limited efficiency improvement effect, such as the development process remaining, and development of a technique that directly forms a relief image on a printing original plate using a laser and does not require development is required. .

  As the method, a method of engraving a printing original plate directly with a laser can be mentioned. Producing letterpress printing plates and stamps by this method has already been performed, and materials used therefor are also known.

  In the case of a printing original plate using a non-photosensitive resin, a portion irradiated with a laser beam is removed. However, a seizure of the resin occurs, and a phenomenon in which engraving residue adhering to the surface cannot be removed occurs. This tendency becomes stronger as the image pattern becomes finer. For example, in the fine dot pattern, the engraving residue is not removed and the pattern is buried.

  Also, when using thermoplastic elastomers, engraving with a laser having an oscillation wavelength in the infrared region melts even the resin that greatly deviates from the laser beam diameter due to heat, so a high-resolution engraving pattern Can not form. Therefore, it is essential to reinforce mechanically by adding a filler to the thermoplastic elastomer layer. For the purpose of mechanical reinforcement of the thermoplastic elastomer layer and improvement of laser light absorption, carbon black having a particularly high mechanical reinforcement effect is mixed in a large amount. However, since a large amount of carbon black is mixed, light transmittance is always sacrificed when photochemical reinforcement is attempted using light. Therefore, when these materials are laser-engraved, a large amount of debris (including liquid viscous material) that is difficult to remove is generated, and not only does it take a long time to process, but also the relief edge (resin edge) And the problem that the shape of the halftone dot is broken. Further, in the laser engraving method, removal of these engraving residue is an extremely important process. Even if an image pattern formed at the corner is left with engraving residue, it becomes defective during printing, and when viscous liquid residue remains and the surface tack is large, paper dust adheres to the printing plate during printing, and printing problems occur. It becomes a factor of.

Therefore, a method for producing a printing plate that can be easily removed from the powdery and viscous liquid engraving residue generated on the surface of the plate, which is generated when directly producing a relief image by laser engraving, and having a small tack on the printing surface, and As a method for removing laser engraving debris, viscous liquid debris generated by melting or decomposition of the resin is absorbed and removed with an inorganic porous material, and the powdery or viscous form existing on the plate surface with high-pressure hot water or high-pressure steam. There has been proposed a method for floating and removing the liquid scum (see Patent Document 1).
Japanese Patent Laid-Open No. 2004-37866

  However, the inclusion of the inorganic porous material has caused problems such as poor image reproducibility and poor working environment by using high-temperature and high-pressure water or steam.

  An object of the present invention is to provide a method capable of safely removing engraving residue without containing an inorganic porous material in a photosensitive resin composition.

In order to solve the above problems, the present inventors have intensively studied and studied, and as a result, have finally completed the present invention. That is, the present invention is as follows.
(1) A printing plate from which the engraving residue generated in the laser engraving process has been removed, with the formation of 2 points of convex and concave characters, 30 μm wide thin line, 100 μm diameter independent point and 156 lpi, 1% halftone dot This is a laser engraving printing plate.

  By adopting the present invention, the engraving residue can be removed safely with good image reproducibility, which greatly contributes to the industry.

  Hereinafter, preferred embodiments of the present invention will be described in more detail. In the present invention, a combination of a printing original plate formed by photocrosslinking a photosensitive resin composition and an aqueous developer brushing cleaning method is extremely effective for removing engraving residue. In addition, the printing original plate used in the present invention is preferably easily melted or decomposed by irradiation with laser light, and is preferably provided with a device for easily removing viscous liquid residue generated by melting or decomposition.

  In the present invention, it is preferable to brush the surface of the engraving plate in an aqueous developer after a laser engraving step of irradiating the printing original plate with a laser beam to form a target pattern. By performing the brushing, powdered debris and liquid debris generated in the laser engraving process can be removed. In particular, the viscous liquid residue can be removed from the plate surface by brushing, which is effective in removing the viscous liquid residue. As the aqueous developer in the present invention, water can be used alone, but a solution in which water and a surfactant are mixed, an aqueous solution in which inorganic salts are dissolved, alkaline ionized water, or the like may be used as a cleaning solution. . Further, the temperature of the aqueous developer may be a temperature at which a normal photosensitive resin original plate is developed, and is generally 20 to 45 ° C, preferably 25 to 43 ° C. The aqueous developer may be reused after removing engraving residue with a mesh filter, an oil adsorption mat filter, a nonwoven fabric filter, or a paper filter.

  In the present invention, the resin constituting the printing original plate is preferably a resin that is easily liquefied or easily decomposed. In particular, it is preferable to use a photosensitive resin composition in which a network structure is formed by a photocrosslinking reaction using a resin having a relatively small number average molecular weight.

Below, the photosensitive resin composition used by this invention is demonstrated in detail.
In the present invention, (A) the hydrophobic polymer obtained from at least two types of water-dispersed latex constituting the photosensitive resin layer is the hydrophobic polymer itself obtained by removing water from the water-dispersed latex. In the present invention, it is necessary to use two or more types.

  Specifically, it is a latex selected from at least two of the following. Polybutadiene latex, natural rubber latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, polychloroprene latex, polyisoprene latex, polyurethane latex, methyl methacrylate-butadiene copolymer latex, vinylpyridine polymer latex, butyl Examples thereof include water-dispersed latex polymers such as polymer latex, thiocol polymer latex and acrylate polymer latex, and polymers obtained by copolymerizing these polymers with other components such as acrylic acid and methacrylic acid. Among these, an aqueous dispersion latex polymer containing a butadiene skeleton or an isoprene skeleton in the molecular chain is preferably used from the viewpoint of hardness and rubber elasticity. Specifically, polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and polyisoprene latex are preferable.

Component (B) of the hydrophilic polymer, -COOH, -COOM (M is monovalent, divalent, or trivalent metal ion or substituted or unsubstituted ammonium ion), - OH, -NH _2, -S
Those having hydrophilic groups such as O ₃ H and phosphate ester groups are preferred. Specifically, (meth)
Polymer of acrylic acid or its salt, copolymer of (meth) acrylic acid or its salt and alkyl (meth) acrylate, copolymer of (meth) acrylic acid or its salt and styrene, (meth) acrylic acid Or a copolymer of its salt and vinyl acetate, a copolymer of (meth) acrylic acid or its salt and acrylonitrile, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide, hydroxyethyl cellulose, polyethylene oxide, polyethyleneimine, -COOM group And polyurethanes having -COOM groups, polyamic acids having -COOM groups, and salts or derivatives thereof. These may be used alone or in combination of two or more.
In the present invention, it is preferred that the hydrophilic polymer of component (B) and at least one hydrophobic polymer of component (A) each have a common skeleton structure.

  The photopolymerizable compound of component (C) exists as a continuous layer. In the present invention, the photopolymerizable compound is preferably a photopolymerizable oligomer, and the photopolymerizable oligomer is a polymer in which an ethylenically unsaturated group is bonded to the terminal and / or side chain of a conjugated diene polymer. The number average molecular weight is 1000 or more and 10,000 or less. Specifically, it refers to a compound having the following structure in the molecular structure.

  The conjugated diene polymer constituting the conjugated diene ethylenic polymer is composed of a homopolymer of a conjugated diene unsaturated compound or a copolymer of a conjugated diene unsaturated compound and a monoethylenically unsaturated compound. As a homopolymer of such a conjugated diene unsaturated compound or a copolymer of a conjugated diene unsaturated compound and a monoethylenically unsaturated compound, a butadiene polymer, an isoprene polymer, a chloroprene polymer, a styrene-chloroprene copolymer, Acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-isoprene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-isoprene copolymer, methyl methacrylate-chloroprene copolymer, acrylic acid Methyl-butadiene copolymer, methyl acrylate-isoprene copolymer, methyl acrylate-chloroprene copolymer, methyl acrylate-chloroprene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile copolymer Ropuren - styrene copolymer, and the like. Of these, a butadiene polymer, an isoprene polymer, and an acrylonitrile-butadiene copolymer are preferable from the viewpoint of rubber elasticity and photocurability, and a butadiene polymer and an isoprene polymer are particularly preferable.

  The method for introducing the terminal and / or side chain ethylenically unsaturated group of the conjugated diene polymer is not particularly limited. For example, (1) a hydroxyl group-terminated conjugated diene polymer obtained using hydrogen peroxide as a polymerization initiator. Monoethylenically unsaturated carboxylic acid such as (meth) acrylic acid or the like is ester-bonded to the terminal hydroxyl group by dehydration reaction, or monoethylenically unsaturated carboxylic acid such as methyl (meth) acrylate or ethyl (meth) acrylate (2) Conjugated diene heavy compounds obtained by copolymerizing an ethylenically unsaturated compound containing an unsaturated carboxylic acid (ester) at least partly with a conjugated diene compound. Examples include a method of reacting ethylenically unsaturated alcohol such as allyl alcohol and vinyl alcohol with the coalescence. .

  The amount of the ethylenically unsaturated group in the conjugated diene-based ethylenic polymer is preferably 0.005 to 2.0 meq / g, particularly preferably 0.01 to 2.0 meq in the polymer. If it exceeds 2.0 meq / g, the hardness will be too high and sufficient elasticity will be difficult to obtain, and the ink transportability of the solid part during printing will be reduced. If it is less than 0.005 meq / g, the hardness becomes too low and it becomes difficult to obtain a sufficient hardness, the dot gain in printing increases, and the printing accuracy decreases.

  In the present invention, photopolymerizable compounds such as acrylates and methacrylates that are generally used can be added as necessary within a range that does not impair the effects of the present invention.

  In the present invention, the photosensitive resin composition is one in which a photopolymerization initiator is added as the component (D). Any photopolymerization initiator can be used as long as it can polymerize a polymerizable carbon-carbon unsaturated group by light. Especially, what has the function to produce | generate a radical by self-decomposition or hydrogen abstraction by light absorption is used preferably. For example, benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, diacetyls and the like. As a compounding quantity of a photoinitiator, the range of 0.1-50 weight part is preferable with respect to 100 weight part of (A) component.

  A plasticizer can be further added to the photosensitive resin composition in the present invention. The plasticizer is not particularly limited as long as it generally has a property of softening the plate material, but those having good compatibility with the component (A) and the component (B) are preferable. More preferred are polyene compounds which are liquid at room temperature and compounds having an ester bond. Examples of the polyene compound which is liquid at room temperature include liquid polybutadiene, polyisoprene, and maleated products and epoxidized products having their end groups or side chains modified. Examples of the compound having an ester bond include phthalic acid ester, phosphoric acid ester, sebacic acid ester, adipic acid ester, and polyester having a molecular weight of 1000 to 3000.

  When these plasticizer components are added, 0 to 100 parts by weight is preferable with respect to 100 parts by weight of component (A) from the viewpoint of obtaining sufficient strength as a solid plate before photocrosslinking.

  In order to increase the thermal stability of the photosensitive resin composition, a conventionally known polymerization inhibitor may be added. Preferable polymerization inhibitors include phenols, hydroquinones, catechols and the like. These compounding amounts are generally used in the range of 0.001 to 5% by weight with respect to the total photosensitive resin composition.

  Moreover, dye, a pigment, surfactant, an antifoamer, a ultraviolet absorber, a fragrance | flavor, a thickener etc. can be added as another component.

  In the present invention, an existing resin molding method can be used as a method of molding the resin composition into a sheet or cylinder. For example, a casting method, a method of extruding a resin from a nozzle or a die with a machine such as a pump or an extruder, adjusting the thickness with a blade, and adjusting the thickness by calendering with a roll can be exemplified. In that case, it is also possible to perform the molding while heating within a range that does not deteriorate the performance of the resin.

  In the present invention, a cover film can also be used. The cover film is provided to protect the photosensitive resin composition during storage and handling of the original plate, and is removed (peeled) before engraving. In the original plate of the present invention, scratches of the photosensitive resin composition are prevented during the removal of the cover film, that is, during the peeling operation.

  When the cover film is removed before engraving, the constituent materials of such a cover film include: polyester; polyalkylene such as polyethylene and polypropylene; polyacetal; polyimide; polycarbonate; polyphenylene ether; polyethylene oxide; A copolymer of ethylene and vinyl acetate; an amphoteric interpolymer; a cellulose-based polymer such as hydroxyalkyl cellulose and cellulose acetate; a polybutyral; and a cyclic rubber. Here, the amphoteric interpolymers are those described in US Pat. No. 4,293,635. The material may be used alone or in combination of two or more. In addition, self-oxidizing compounds such as nitrocellulose and nitroglycerin; non-self-oxidizing polymers such as alkyl cellulose (eg, ethyl cellulose), polyacrylic acid and alkali metal salts thereof, and combinations thereof can also be used.

  The thickness of the cover film is preferably 10 to 300 μm, particularly preferably 10 to 200 μm.

  In the present invention, a support can also be used. A material having flexibility and excellent dimensional stability is preferably used as the support, and examples thereof include polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, and polycarbonate. The thickness of the support 1 is preferably 50 to 250 μm, preferably 100 to 200 μm from the viewpoint of mechanical properties and shape stability of the original plate. Further, if necessary, a known adhesive conventionally used for this kind of purpose may be provided on the surface in order to improve the adhesion between the support and the photosensitive resin layer.

The method for producing the photosensitive resin laminate of the present invention is not particularly limited, but generally, a photosensitive resin layer is formed on a support by coating, spray coating or the like, or a commercially available photosensitive flexographic printing. One laminate is created by peeling off the protective film from the plate. The laminated body thus obtained is produced by laminating using a heat press machine or the like. The lamination conditions are such that the temperature is room temperature to 150 ° C., preferably 50 to 120 ° C., and the pressure is 20 to 200 kgf / cm ² , preferably 50 to 150 kgf / cm ² .

  The molded photosensitive resin composition is crosslinked by irradiation with light or electron beam to form a printing original plate. Moreover, it can also bridge | crosslink by irradiation of light or an electron beam, shape | molding. Among them, the method of crosslinking using light is preferable because it has advantages such as simple apparatus and high thickness accuracy. Examples of the light source used for curing include a high-pressure mercury lamp, an ultra-high pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, and a xenon lamp, and the curing can be performed by other known methods. The light source used for curing may be one type, but the curability of the resin may be improved by curing using two or more types of light sources having different wavelengths, so two or more types of light sources may be used. There is no problem.

The thickness of the original plate used for laser engraving may be arbitrarily set according to the purpose of use, but when used as a printing plate, it is generally preferably 0.1 to 7 mm. In some cases, a plurality of materials having different compositions may be stacked.
In laser engraving, a relief image is created on an original by operating a laser device using a computer as an image to be formed as digital data. Any laser may be used for the laser engraving as long as the original plate includes a wavelength having absorption. However, in order to perform engraving at a high speed, a laser with a high output is desirable. Infrared or infrared emitting solid lasers such as YAG lasers and semiconductor lasers are preferred. In addition, an ultraviolet laser having an oscillation wavelength in the ultraviolet region, such as an excimer laser, a YAG laser wavelength-converted to the third or fourth harmonic, a copper vapor laser, and the like, can be ablated to cut bonds between organic molecules, Suitable for fine processing. The laser may be continuous irradiation or pulse irradiation. In general, resin has absorption in the vicinity of 10 μm of carbon dioxide laser, so it is not essential to add a component that assists in the absorption of laser light, but YAG laser has a wavelength in the vicinity of 1.06 μm. There is not much that has. In that case, it is necessary to add dyes and pigments, which are components that assist in the absorption of these. Examples of such dyes include poly (substituted) phthalocyanine compounds and metal-containing phthalocyanine compounds; cyanine compounds; squarylium dyes; chalcogenopyrylarylidene dyes; chloronium dyes; Indolizine dyes; bis (aminoaryl) polymethine dyes; merocyanine dyes; and quinoid dyes. Examples of pigments include dark inorganic pigments such as carbon black, graphite, copper chromite, chromium oxide, cobalt chrome aluminate, iron oxide, and metal powders such as iron, aluminum, copper, and zinc, and Si, Examples include those doped with Mg, P, Co, Ni, Y, and the like. These dyes and pigments may be used alone, in combination of a plurality, or in any form such as a multilayer structure.

  Next, the present invention will be specifically described using examples, but the present invention is not limited to these examples.

(Preparation of photosensitive resin composition)
(A) component butadiene latex (Nipol LX111NF nonvolatile content 55% made by Nippon Zeon Co., Ltd.) 22 parts by weight, acrylonitrile-butadiene latex (Nipol SX1503 nonvolatile content 43% made by Nippon Zeon Co., Ltd.) 5 parts by weight, (B ) Component hydrophilic polymer (PFT-3
Non-volatile content 25% 5 parts by weight (manufactured by Kyoeisha Chemical Co., Ltd.), 10 parts by weight of (C) component Eugobutadiene acrylate (ABU-2S Kyoeisha Chemical Co., Ltd.), photopolymerization initiator (D) 0.45 parts by weight, 3 parts by weight of lauryl methacrylate as a crosslinking agent, 0.9 parts by weight of dimethylol tricyclodecane diacrylate, 0.03 parts by weight of hydroquinone monomethyl ether as a polymerization inhibitor, and carboxylic acid-based co-polymers as other additives 0.04 part by weight of the polymer was mixed with 15 parts by weight of toluene in a container, and then kneaded at 105 ° C. using a pressure kneader. Thereafter, toluene and water were removed under reduced pressure to obtain a photosensitive resin composition.

(Preparation of original plate)
When the photosensitive resin composition was laminated using a heat press machine and the pattern was engraved using a laser engraving machine, powdered and viscous liquid engraving residue was observed on the printing plate surface. .
Then, after laser engraving, the engraving residue was removed using a developing machine (Stuck System) manufactured by A & V Co., Ltd. The surface of the engraving plate may be brushed in a circular direction for 4 minutes by a method of brushing in an aqueous developer at a temperature of 40 ° C. to remove engraving residue existing on the surface of the printing plate generated in the laser engraving process. did it. In addition, engraving residue was not observed in the halftone dot portion, the pattern shape of the halftone dot portion was conical and good, and no chipping or the like was observed.
The specifications of the brush at this time are as follows.
Hair: Nylon (azuron) 150μm
Hitting Kugi: SUS
Flocking hole diameter: φ25
Flocking density: 120 / hole flocking pitch: 6mm
Script: Melamine resin plywood

Implementation of Post-Processing The above printing plate was washed, dried at 60 ° C. for 10 minutes, and finally irradiated with a germicidal lamp for 5 minutes to remove surface adhesion.
The resulting flexographic printing plate was inspected with a 10x magnifier. The test patterns of 2 points convex and concave characters, 30 μm wide thin line, 100 μm diameter independent point and 156 lpi, 1% halftone dot were formed accurately.

  As described above, the printing original plate formed by photocuring the photosensitive resin composition of the present invention having such a configuration is subjected to laser engraving, and then the surface of the obtained printing plate is brushed in an aqueous developer to form a powder. In addition, since a large amount of viscous liquid residue generated can be easily removed and the tack of the printing plate surface can be reduced, it can be used as a method for producing a printing plate by laser engraving.

Claims (1)

  A printing plate from which the engraving residue generated in the laser engraving process has been removed, with 2 points of convex and concave characters, 30 μm wide thin line, 100 μm diameter independent point and 156 lpi, 1% halftone dot Laser engraving printing plate.