JP2007185917A - Manufacturing method for printing plate for flexography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making a laser engraved plate with a wide halftone-dot reproducing area, which is excellent in printing quality, particularly, dot-gain quality. <P>SOLUTION: This method for manufacturing a printing plate for flexography by laser-engraving a printing original plate layer (A) is characterized in that laser engraving is performed by combining different laser engraving conditions together in such a manner that at least one halftone-dot area ratio point, where a halftone-dot area ratio of one printed image is in the range of 5-40%, serves as a boundary. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides relief image formation for flexographic printing plates by laser engraving, formation of surface patterns such as embossing, relief image formation for printing such as tiles, conductors of electronic components, semiconductors, insulators, pattern formation, reflection of optical components Pattern formation of functional materials such as prevention films, color filters, (near) infrared cut filters, and alignment films, underlayers, light emitting layers, electron transport layers in the production of display elements such as liquid crystal displays or organic electroluminescence displays, The present invention relates to a method of laser engraving a laser engraving printing original plate suitable for forming a coating film / pattern of a sealing material layer to form a printing plate.

Flexographic printing is used for printing on packaging materials such as cardboard, paper containers, paper bags, flexible packaging films, wallpaper, decorative materials such as decorative boards, and labels, and the ratio is increasing among various printing methods.
The flexographic printing method is to supply ink from an ink supply unit called anilox to the convex part of a printing plate with three-dimensional irregularities, and then apply the ink to the convex part of paper, film, cardboard, etc. In this method, ink is transferred to a printing medium. A good print quality in flexographic printing is that there is no blur in the solid portion and the ink is sufficiently loaded, and at the same time, the halftone portion is bright and the dot gain is low. However, in order to increase the ink shielding property of the solid part, the printing pressure is increased, and high printing results in crushing the dots in the halftone part, resulting in an increase in dot gain. It is difficult to obtain.

  Photosensitive resins are often used for the production of printing plates used for flexographic printing, and the negative film is exposed using a liquid photosensitive resin or a solid photosensitive resin molded into a plate shape. A method has been used in which a non-crosslinked portion is washed off with a developing solution after irradiating light through a negative film to cause a cross-linking reaction after being placed on a functional resin. 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, and then light is irradiated through the mask to cause a crosslinking reaction. Later, a so-called flexo CTP technology was developed in which the non-crosslinked portion of the sun-irradiated portion was washed away with a developer, and its adoption has been progressing due to improved printing plate production efficiency.

In recent years, a plate making technique that does not require a development step in the plate making process has been proposed. As a method therefor, a method of directly engraving a printing original plate with a laser is disclosed in Japanese Patent Laid-Open Nos. 2004-314334 and 2004. -262136 (Patent Document 2) and JP-A-2004-262135 (Patent Document 3).
When engraving a printing original plate directly with a laser, a YAG laser that oscillates in the near infrared wavelength region or a carbon dioxide gas laser that oscillates in the infrared region is often used. In particular, a carbon dioxide laser is often used for laser engraving because it is efficiently absorbed by the resin constituting the printing original plate.

  In the printing plate obtained by laser engraving, the dot height of the halftone dot portion and the height of the line portion may be different, Flexo & Gravure Int'l 2-2005 (pages 10 to 16) (non-patent literature) 1). Here, it is also described that the highlight portion cannot be printed when the dot height of the halftone dot portion is too lower than the height of the line portion. By making the dot height of the halftone dot portion lower than the height of the line portion or the solid portion, it can be expected that the pressure in printing is absorbed by the line portion and the solid portion, and the thickness of the halftone dot portion is reduced. When the halftone dots are lowered in order to reduce the thickness of the halftone dot portions, there is a problem that the print area is small and the low halftone dot area rate portion cannot be printed.

  Japanese Patent Laid-Open No. 2002-244289 (Patent Document 4) absorbs ethylene propylene diene monomer rubber, elastomer binder, monomer, photoinitiator and infrared rays as an element that directly engraves the desired relief surface required for flexographic printing with a laser. Reinforced elastomers of elastomer compositions containing additives containing silicon-oxygen or phosphorus-oxygen functionality. It also describes that the relief of the printing plate can be modified in many ways, not only the gradient of the relief that slowly drops to affect the dot gain of the plate, but also a very steep gradient. However, as described in Flexo & Gravure Int'l 2-2005 (pages 10 to 16), there is a problem that a low halftone dot region may not be printed by applying a very steep gradient. there were.

  Patent Literature 3, Patent Literature 2, and Patent Literature 1 propose a photosensitive resin composition capable of laser engraving and a printing original plate capable of laser engraving. However, in each publication, there is no description about the influence of laser engraving conditions on print quality, and there is no description about combining laser engraving conditions.

  In JP-A-2002-268228 (Patent Document 5), by adding a compound that absorbs ultraviolet rays in the range of 320 nm to 420 nm to the slip layer on the photosensitive resin layer, the shoulder angle of the convex line is controlled. It is stated that a printed matter with less weight can be obtained. However, since the laser engraving plate directly forms an image with a laser, it does not have a slip layer, and even when it is provided, the effect cannot be expected.

  Japanese Unexamined Patent Application Publication No. 2004-264818 (Patent Document 6) proposes a flexographic printing plate including a printed image and a relief element having a height difference defined in a non-image area. In this patent document 6, it is described that a non-image area is controlled by using a relief element having a specified altitude difference with respect to an image area. However, the purpose of providing an altitude difference in the relief element is to control the stamp, and further, there is a description of providing a halftone dot height in a printed image or combining halftone dots having different halftone dot heights. Absent.

  In each of JP-A-11-153865 (Patent Document 7) and JP-A-2003-98652 (Patent Document 8), a photosensitive composition for flexographic printing having a non-infrared shielding layer that can be excised with an infrared laser is disclosed. Proposed. Japanese Patent Laid-Open No. 2000-289180 (Patent Document 9) discloses an ultraviolet shielding film which is non-adhesive and can be removed by an infrared laser on a photosensitive resin layer having a uniform seamless thickness and adhesiveness. Is wound in a cylindrical shape in the circumferential direction, laminated, and after removing the seam portion, the ultraviolet shielding layer is removed with an infrared laser to form an image, and a plate making process is performed to create a seamless flexographic printing plate Proposals have been proposed for how to do this. Each of these publications describes a method of directly drawing image information converted into digital information with an infrared laser, or a photosensitive structure suitable for it. However, there is no description of improving the printing quality by changing the laser drawing conditions, and further combining the laser drawing conditions.

  In addition to the printing plate for flexographic printing, as a method for producing a printed material, use of a laser beam is proposed in Japanese Patent Laid-Open Nos. 6-234262 (Patent Document 10) and Japanese Patent Laid-Open No. 2001-146064 (Patent Document 11). ing. Each of these reports proposes engraving the printed part using laser light, but there is no description about flexographic printing, halftone dot, or any combination of engraving conditions.

  Japanese Patent Laid-Open No. 2-102048 (Patent Document 12) proposes a laser plate making apparatus in letterpress plate making in which the plate making scan direction is the contour tangent direction of the plate convex portion and the modulation direction of laser output is the contour direction. In Patent Document 12, it is described that a relief having an arbitrary number of steps and angles is created. However, there is no description about combining dot height and laser engraving conditions.

Japanese Patent Laying-Open No. 2003-53928 (Patent Document 13) proposes a method and apparatus for manufacturing a printing block. In this apparatus, it is proposed to engrave using a plurality of beams, but there is no description about combining the height of the halftone dots and the laser engraving conditions.
As described above, the present situation is that a method for producing a laser engraving plate having excellent print quality, particularly dot gain quality, and a wide dot reproduction area has not been found.

JP 2004-314334 A JP 2004-262136 A JP 2004-262135 A JP 2002-244289 A JP 2002-268228 A JP 2004-264818 A Japanese Patent Laid-Open No. 11-15386 JP 2003-98652 A JP 2000-289180 A JP-A-6-234262 JP 2001-146064 A Japanese Patent Laid-Open No. 2-102048 JP 2003-53928 A CHRISTIAN WEBER, Flexo & Gravure Int'l, No. 2-2005, Germany, G & K TechMedia GmbH. Published in June 2005, pages 10-16

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a laser engraving plate having a wide halftone dot reproduction region that is excellent in printing quality, particularly dot gain quality.

The present inventor has intensively studied and is a method for producing a printing plate for flexographic printing by laser engraving the printing original plate layer (A), and has a dot area ratio of 5% to 40% in one printed image. The method for producing a printing plate for flexographic printing, characterized in that laser engraving is performed by combining different laser engraving conditions with at least one halftone dot area ratio as a boundary. We found a method to create a laser engraving plate with a wide dot reproduction area.

The present invention is as follows.
1. A method for producing a printing plate for flexographic printing by laser engraving a printing original plate layer (A), wherein at least one halftone dot area ratio of halftone dot area ratio of 5% to 40% in one printed image A method for producing a printing plate for flexographic printing, characterized by combining laser engraving with different laser engraving conditions.
2. 1. The difference between halftone dot height and solid part height is changed. A method for producing a printing plate for flexographic printing according to 1.
3. 1. The height of the dot portion is equal to or lower than the solid portion height in the range of greater than 0 μm and less than or equal to 500 μm. A method for producing a printing plate for flexographic printing according to 1.
4). 1. The halftone dot angle is changed. A method for producing a printing plate for flexographic printing according to 1.
5). 3. In a region where the halftone dot area ratio is 70% or less, the halftone dot angle is changed in a range where the halftone dot angle is not less than 0 ° and not more than 60 °. A method for producing a printing plate for flexographic printing according to 1.
6). 1. A printing original plate layer (A) is laminated on a cylindrical support. To 5. The manufacturing method of the printing plate for flexographic printing in any one of.
7). The printing original plate layer (A) consists of curing a photosensitive resin, a resin (a-1) having a number average molecular weight of 1,000 or more and 300,000 or less, and having a polymerizable unsaturated group in the molecule with a number average molecular weight of less than 1,000. 1. A photosensitive resin composition (a) containing an organic compound (a-2) and a photopolymerization initiator (a-3) is photocured to form a printing original plate layer (A). To 6. The manufacturing method of the printing plate for flexographic printing in any one of.

  According to the present invention, the present invention can provide a method for producing a laser engraving plate having a wide dot reproduction area and excellent print quality, particularly dot gain quality.

Hereinafter, the present invention will be specifically described with a focus on preferred embodiments thereof.
In the present invention, one print image refers to a print image represented by one piece of block data created by using a block creating device such as a computer. A composition is described in “until new printing is possible” (edited by Fuji Photo Film Co., Ltd., published in 1999), that is, a state where a plate can be made in a manuscript such as a photograph or a letter. However, when printing is performed with a plurality of colors of ink, a printing plate corresponding to each color is manufactured, so that plate-making data for each color is created for each color from the data under one plate. In the present invention, each color print image printed by the plate-making data for each color is also created as a different printing plate, so that each one is an image.

  The halftone dot in the present invention refers to a halftone dot defined in “New Edition Printing Encyclopedia” (edited by the Japan Printing Society, published in 1974). That is, it is a point formed on a net negative / net positive, a net letterpress, and its printed matter through a net screen or contact screen, and the density of the original is reproduced by the size of the halftone dot.

  For the printing original layer (A) in the present invention, a known laser-engravable original can be used. For example, a printing original made of natural rubber, silicon rubber, or ethylene-propylene rubber can be used. Alternatively, the printing original plate layer (A) may be obtained by photocuring a solid photosensitive resin or a liquid photosensitive resin. However, from the viewpoint of production efficiency and printing quality of the printing original layer (A), it is preferable to cure the photosensitive resin to obtain the printing original layer (A). Furthermore, it is more preferable to use a liquid type photosensitive resin in terms of the amount of laser engraving residue generated. For example, JP 2004-314334 A, JP 2004-262136 A, JP 2004-262135 A, JP-A-2004-255812 and JP-A-2004-255811 describe that direct engraving by a laser using a liquid type photosensitive resin is used, and it can also be used in the present invention.

  The photosensitive resin composition (a) that can be used in the present invention contains a resin (a-1), an organic compound (a-2) having a polymerizable unsaturated group, and a photopolymerization initiator (a-3). It is preferably in a liquid state at ° C. The photosensitive resin composition (a) is molded into a sheet or cylinder, and then irradiated with light, cured to form a printing original plate layer (A), and a printing plate can be obtained by direct engraving with a laser.

  The resin (a-1) is preferably liquid at 20 ° C. The liquid resin here means a polymer that has the property of being easily deformed by flow and solidified into a deformed shape by cooling. When an external force is applied, it is instantly deformed according to the external force. However, it is a term corresponding to an elastomer having the property of recovering its original shape in a short time when external force is removed. If resin (a-1) is liquid resin at 20 degreeC, the photosensitive resin composition will also be liquid. The photosensitive resin composition (a) capable of obtaining good thickness accuracy and dimensional accuracy when the relief image forming original plate obtained from this is molded into a cylindrical shape, preferably has a viscosity at 20 ° C. of 10 Pa · s to 10 kPa.・ S or less. More preferably, it is 50 Pa · s or more and 5 kPa · s or less. If it is 10 Pa · s or more, the mechanical strength of the produced printing original plate is sufficient, and even when it is deformed into a cylindrical printing original plate, the shape can be easily held and processed. If the viscosity is 10 kPa · s or less, it is easily deformed even at room temperature and easy to process. The photosensitive resin composition (a) that can be used in the present invention is easy to mold into a cylindrical printing original plate, and the process is simple.

  The composition of the resin (a-1) of the present invention is not particularly limited. The number average molecular weight of the resin (a-1) is preferably from 1,000 to 100,000, more preferably from 2,000 to 50,000, still more preferably from 5,000 to 50,000. If the number average molecular weight of the resin (a-1) is 1000 or more, the original plate produced by crosslinking later maintains strength, and the relief image produced from this original plate is strong. When used as a printing plate, it is used repeatedly. Can withstand. The upper limit of the number average molecular weight of the resin (a-1) is preferably 100,000 or less. If it is 100,000 or less, the viscosity of the photosensitive resin composition (a) does not increase excessively, and a complicated method such as overheating extrusion is used when preparing a sheet-shaped or cylindrical laser-engraving printing original plate. unnecessary. The number average molecular weight referred to here is a value measured by gel permeation chromatography (GPC) and calibrated with polystyrene having a known molecular weight.

  As the resin (a-1) to be used, a resin that is easily liquefied or a resin that is easily decomposed is preferable. As the resin that easily decomposes, α-methylstyrene, α-methoxystyrene, acrylic esters, methacrylates, ester compounds, ether compounds, nitro compounds, carbonate compounds, carbamoyl compounds, It is preferable that hemiacetal ester compounds, oxyethylene compounds, aliphatic cyclic compounds, and the like are included. Especially ethers such as polyethylene glycol, polypropylene glycol, polytetraethylene glycol, aliphatic polycarbonates, aliphatic carbanates, polymethyl methacrylate, polystyrene, nitrocellulose, polyoxyethylene, polynorbornene, polycyclohexanediene hydrogenated product, Alternatively, a polymer having a molecular structure such as a dendrimer having many branched structures is a representative example of those that are easily decomposed. A polymer containing a large number of oxygen atoms in the molecule is preferred from the viewpoint of degradability. Among these, a compound having a carbonate group, a carbamate group, or a methacryl group in the polymer main chain is preferable because of its high thermal decomposability. For example, a polyamide synthesized using (poly) carbonate diol or (poly) carbonate diamine as a raw material can be cited as a polymer having good thermal decomposability. These polymer main chains and side chains may contain a polymerizable unsaturated group. In particular, when a reactive functional group such as a hydroxyl group, an amino group, or a carboxyl group is present at the terminal, it is easy to introduce a polymerizable unsaturated group at the terminal of the main chain.

  The resin (a-1) may have a polymerizable unsaturated group in the molecule. Particularly preferred are polymers having an average of 0.7 or more polymerizable unsaturated groups per molecule, and more than 1 is more preferred. If the average is 0.7 or more per molecule, the obtained printing original plate is excellent in mechanical strength, and the relief shape is difficult to collapse during laser engraving. Furthermore, its durability is good and it can withstand repeated use, which is preferable. The term “intramolecular” as used herein includes the case where a polymerizable unsaturated group is directly attached to the terminal of the polymer main chain, the terminal of the polymer side chain, the polymer main chain or the side chain.

  Examples of the resin (a-1) include polyolefins such as polyethylene and polypropylene, polydienes such as polybutadiene and polyisoprene, polyhaloolefins such as polyvinyl chloride and polyvinylidene chloride, polystyrene, polyacrylonitrile, polyvinyl alcohol, and polyvinyl acetate. , Polyvinyl acetal, polyacrylic acid, poly (meth) acrylic acid esters, poly (meth) acrylamide, C-C chain polymers such as polyvinyl ether, polyethers such as polyphenylene ether, polyethylene terephthalate, polycarbonate, polyacetal One, two or more selected from the group consisting of polymers having a hetero atom in the main chain such as polyurethane, nylon, polyurea and polyimide can be used. . As a form in the case of using a plurality of polymers, either a copolymer or a blend may be used.

  In particular, when a flexible relief image is required as in flexographic printing plate applications, the resin (a-1) is partially a liquid resin having a glass transition temperature of 20 ° C. or lower, more preferably a glass transition temperature of 0 ° C. or lower. It is preferable to use a liquid resin. Examples of such liquid resins include hydrocarbons such as polyethylene, polybutadiene, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene, polyesters such as adipate and polycaprolactone, polyethylene glycol, polypropylene glycol, and polytetraethylene glycol. And polyethers such as aliphatic polycarbonates, silicones such as polydimethylsiloxane, polymers of (meth) acrylic acid and / or derivatives thereof, and mixtures and copolymers thereof. The content is preferably 30 wt% or more based on the entire resin (a-1).

  As a method for producing the resin (a-1), for example, a method in which a polymerizable unsaturated group is directly introduced into the molecular end may be used. Alternatively, a hydroxyl group, an amino group, an epoxy group, a carboxyl group may be used. A plurality of groups capable of binding to the reactive group of the above component having a molecular weight of about several thousand having a plurality of reactive groups such as a group, an acid anhydride group, a ketone group, a hydrazine group, an isocyanate group, a cyclic carbonate group, and an ester group. After reacting with a binder (for example, polyisocyanate in the case of a hydroxyl group or amino group), adjusting the molecular weight and converting to a terminal binding group, the group reacting with this terminal binding group and polymerizable unsaturated A method of introducing a polymerizable unsaturated group at the terminal by reacting with an organic compound having a group is preferred.

  The organic compound (a-2) of the present invention is a compound having an unsaturated bond involved in the radical polymerization reaction, and the number average molecular weight is 1000 or less considering the ease of dilution with the resin (a-1). preferable. Examples of the organic compound (a-2) include olefins such as ethylene, propylene, styrene and divinylbenzene, acetylenes, (meth) acrylic acid and derivatives thereof, haloolefins, unsaturated nitriles such as acrylonitrile, (meth) Acrylamide and derivatives thereof, allyl compounds such as allyl alcohol and allyl isocyanate, unsaturated dicarboxylic acids such as maleic anhydride, maleic acid and fumaric acid and derivatives thereof, vinyl acetates, N-vinylpyrrolidone, N-vinylcarbazole, cyanate esters Among them, (meth) acrylic acid and derivatives thereof are preferable examples from the viewpoint of the abundance of the kind and price.

The derivatives include alicyclics such as cycloalkyl-, bicycloalkyl-, cycloalkene-, bicycloalkene-, aromatics such as benzyl-, phenyl-, phenoxy-, alkyl-, halogenated alkyl-, alkoxyalkyl- , Hydroxyalkyl-, aminoalkyl-, tetrahydrofurfuryl-, allyl-, glycidyl-, alkylene glycol-, polyoxyalkylene glycol-, (alkyl / allyloxy) polyalkylene glycol- and esters of polyhydric alcohols such as trimethylolpropane Etc.
In this invention, the organic compound (a-2) which has these polymerizable unsaturated bonds can select the 1 type (s) or 2 or more types according to the objective. For example, when used as a printing plate, it has at least one long-chain aliphatic, alicyclic or aromatic derivative as an organic compound used to suppress swelling with respect to an organic solvent such as alcohol or ester which is a solvent for printing ink. It is preferable. In order to increase the mechanical strength of the printing original plate obtained from the resin component of the present invention, the organic compound (a-2) preferably has at least one aliphatic or aromatic derivative. In this case, the organic compound It is preferably 20 wt% of the total amount of (a-2), more preferably 50 wt% or more.

In order to increase the resilience of the printing plate, for example, a methacrylic monomer as described in JP-A-7-239548 can be used, or technical knowledge of a known photosensitive resin for printing can be used depending on the purpose. .
A well-known photoinitiator can be used for a photoinitiator (a-3). As the photopolymerization initiator, a hydrogen abstraction type photopolymerization initiator and / or a decay type photopolymerization initiator can be used.

  As the hydrogen abstraction type photopolymerization initiator, a known hydrogen abstraction type photopolymerization initiator can be used, and although it is not limited, it is preferable to use an aromatic ketone. Aromatic ketone is efficiently converted into an excited triplet state by photoexcitation, and this excited triplet state has been proposed to generate a radical by extracting hydrogen from the surrounding medium. The hydrogen abstraction type photopolymerization initiator used in the present invention may be any compound as long as it is a compound that generates radicals by extracting hydrogen from the surrounding medium through an excited triplet state. Examples of aromatic ketones include benzophenones, Michler ketones, xanthenes, thioxanthones, and anthraquinones, and it is desirable to use at least one compound selected from these groups. Benzophenones refer to benzophenone or its derivatives, specifically 3,3 ', 4,4'-benzophenone tetracarboxylic anhydride, 3,3', 4,4'-tetramethoxybenzophenone, and the like. Michler ketones refer to Michler and its derivatives. Xanthene refers to a derivative substituted with xanthene and an alkyl group, a phenyl group, or a halogen group, and examples thereof include ethylthioxanthone, methylthioxanthone, and chlorothioxanthone. Anthraquinones are anthraquinone and derivatives substituted with an alkyl group, a phenyl group, or a halogen group.

  The collapsible polymerization initiator is a compound in which a cleavage reaction occurs in the molecule after light absorption and an active radical is generated, and is not particularly limited in the present invention. Specific examples include benzoin alkyl ethers, 2,2-dialkoxy-2-phenylacetophenones, acetophenones, acyloxime esters, azo compounds, organic sulfur compounds, and diketones. It is preferable to use at least one compound selected from these groups. Examples of benzoin alkyl ethers include benzoin isopropyl ether, benzoin isobutyl ether, and compounds described in “Photosensitive polymer” (Kodansha, 1977, page 228). Examples of 2,2-dialkoxy-2-phenylacetophenone include 2,2-dimethoxy-2-phenylacetophenone and 2,2-dimethoxy-2-phenylacetophenone. Examples of acetophenones include acetophenone, trichloroacetophenone, 1-hydroxycyclohexylphenylacetophenone, 2,2-diethoxyacetophenone, and the like. Examples of the acyloxime esters include 1-phenyl-1,2-propanedione-2- (o-benzoyl) oxime. Examples of the azo compound include azobisisobutyronitrile, diazonium compound, and tetrazene compound. Examples of organic sulfur compounds include aromatic thiols, mono- and disulfides, thiuram sulfides, dithiocarbamates, S-acyl dithiochelbamates, thiosulfonates, sulfoxides, sulfinates, dithiocarbonates, and the like.

  It is preferable that a photoinitiator (a-3) is 0.1 wt% or more and 10 wt% or less with respect to the whole photosensitive resin composition (a). The addition amount of the hydrogen abstraction type photopolymerization initiator is preferably 0.1 wt% or more and 10 wt% or less of the total amount of the photosensitive resin composition (a), more preferably 0.5 wt% or more and 5 wt% or less. The amount of the collapsible photopolymerization initiator added is preferably 0.1 wt% or more and 10 wt% or less, more preferably 0.3 wt% or more and 3 wt% or less of the entire photosensitive resin composition (a). From the viewpoint of the photocurability of the photosensitive resin, the photopolymerization initiator is preferably a combination of a hydrogen drawing-out photopolymerization initiator and a decay type photopolymerization initiator.

  It is preferable to add an inorganic porous material to the photosensitive resin composition (a) that can be used in the present invention, and it is more preferable particularly when producing a printing original plate for laser engraving. An inorganic porous material is an inorganic particle having fine pores or fine voids in the particle, and is added for the purpose of removing viscous liquid debris generated in large quantities in laser engraving. Yes, the number average particle size, specific surface area, average pore size, pore volume, and loss on ignition greatly affect the performance.

  The inorganic porous body preferably has a number average particle size of 0.1 to 100 μm. When a smaller leaf having a number average particle diameter is used, dust entrains when the original plate obtained from the resin composition of the present invention is engraved with a laser, and the engraving apparatus is easily contaminated. On the other hand, when a larger particle than the above-mentioned number average particle size is used, a defect may occur in the relief image when laser engraving is performed. A more preferable range of the average particle diameter is 0.5 to 20 μm, and a further preferable range is 3 to 10 μm. The average particle size of the porous inorganic absorbent of the present invention can be measured using a laser scattering particle size distribution measuring device.

The range of the specific surface area of the inorganic porous body is preferably 10 m ² / g or more and 1500 m ² / g or less. A more preferable range is 100 m ² / g or more and 800 m ² / g or less. When the specific surface area is 10 m ² / g or more, removal of the liquid residue at the time of laser engraving becomes sufficient, and when it is 1500 m ² / g or less, an increase in the viscosity of the photosensitive resin composition (a) is suppressed, , Thixotropy can be suppressed. The specific surface area is determined from the adsorption isotherm of nitrogen at −196 ° C. based on the BET equation.

  The average pore diameter of the inorganic porous material used in the present invention has a great influence on the amount of liquid residue absorbed during laser engraving. A preferable range of the average pore diameter is 1 nm to 1000 nm, more preferably 2 nm to 200 nm, still more preferably 2 nm to 200 nm, and particularly preferably 2 nm to 50 nm. If the average pore diameter is 1 nm or more, the absorbability of liquid debris generated during laser engraving can be ensured, and if it is 1000 nm or less, the specific surface area of the particles is large and the amount of liquid debris absorbed can be sufficiently ensured.

  In the present invention, the average pore diameter is a value measured using a nitrogen adsorption method. Those having an average pore diameter of 2 to 50 nm are called mesopores, and the ability of porous particles having mesopores to absorb liquid waste is extremely high. The pore size distribution is determined from the nitrogen adsorption isotherm at -196 ° C.

  The pore volume of the inorganic porous material used in the present invention is preferably from 0.1 ml / g to 10 ml / g, more preferably from 0.2 ml / g to 5 ml / g. When the pore volume is 0.1 ml / g or more, the amount of viscous liquid residue absorbed is sufficient, and when the pore volume is 10 ml / g or less, the mechanical strength of the particles can be ensured. In the present invention, a nitrogen adsorption method is used to measure the pore volume.

  In the present invention, there is an oil absorption amount as an index for evaluating the liquid residue adsorption amount. This is defined by the amount of oil absorbed by 100 g of the inorganic porous body. A preferable range of the oil absorption amount of the inorganic porous material used in the present invention is 10 ml / 100 g or more and 2000 ml / 100 g or less, more preferably 50 ml / 100 g or more and 1000 ml / 100 g or less. If the oil absorption is 10 ml / 100 g or more, removal of the liquid residue generated during laser engraving is sufficient, and if it is 2000 ml / 100 g or less, the mechanical strength of the inorganic porous body can be sufficiently secured. The oil absorption was measured according to JIS-K5101.

  The inorganic porous material used in the present invention preferably retains its porosity without being deformed or melted by laser light irradiation in the infrared wavelength region. The loss on ignition when treated at 950 ° C. for 2 hours is preferably 15 wt% or less, more preferably 10 wt% or less.

  The particle shape of the inorganic porous material used in the present invention is not particularly limited, and spherical, flat, needle-like, amorphous, or particles having protrusions on the surface can be used. In particular, spherical particles are preferable from the viewpoint of wear resistance. It is also possible to use particles having hollow inside particles, spherical granules having a uniform pore diameter such as silica sponge, and the like. Although not particularly limited, for example, porous silica, mesoporous silica, silica-zirconia porous gel, porous alumina, porous glass and the like can be mentioned. Moreover, since the pore diameter cannot be defined for a layer having a gap of several to 100 nm such as a layered clay compound, in the present invention, the gap between the layers is defined as the pore diameter.

Furthermore, organic pigments such as pigments and dyes that absorb light of the wavelength of the laser beam can be incorporated into these pores or voids.
Moreover, the surface of the inorganic porous body can be coated with a silane coupling agent, a titanium coupling agent, or other organic compounds, and subjected to a surface modification treatment to make particles more hydrophilic or hydrophobic.
In the present invention, one or two or more of these inorganic porous materials can be selected, and by adding the inorganic porous material, generation of liquid debris during laser engraving, prevention of tacking of the relief printing plate, etc. Improvements are made effectively.

The ratio of the resin (a-1), the organic compound (a-2), and the inorganic porous body in the photosensitive resin composition (a) used in the present invention is usually 100 parts by weight of the resin (a-1). The organic compound (a-2) is preferably 5 to 200 parts by weight, and more preferably 20 to 100 parts by weight. The inorganic porous body is preferably 1 to 100 parts by weight, and more preferably 2 to 50 parts by weight. A more preferable range is 2 to 20 parts by weight.
When the ratio of the organic compound (a-2) is 5 parts by weight or more, the balance between the hardness of the obtained printing plate and the tensile strength and elongation is good. It is possible to suppress the deterioration of thickness accuracy.

  In addition, when the amount of the inorganic porous material is 1 part by weight or more, regardless of the types of the resin (a-1) and the organic compound (a-2), the plate surface tack prevention effect and engraving when laser engraving The effect of suppressing the generation of liquid residue can be sufficiently exhibited. When the amount is 100 parts by weight or more, the printing plate does not become brittle and can maintain transparency, and is particularly used as a flexographic plate. In this case, it is possible to prevent the hardness from becoming too high. When the photosensitive resin composition (a) is cured using light, particularly ultraviolet rays, to produce a laser engraving printing original plate, light transmittance affects the curing reaction. Therefore, it is effective to use a material having a refractive index close to that of the photosensitive resin composition (a).

As a method of mixing the inorganic porous material in the photosensitive resin composition (a), a method of directly adding the inorganic porous material in a state where the thermoplastic resin is heated and fluidized, or photopolymerization with the thermoplastic resin. Any method of adding an inorganic porous material to the first kneaded organic organic compound (a-3) may be used. However, it is preferable to avoid a method of mixing the inorganic porous material (a-3) directly with the photopolymerizable organic material (a-3) having a low molecular weight. That is, when this third method is used, the residue absorption performance of the inorganic porous material may be lowered.
In addition, a polymerization inhibitor, an ultraviolet absorber, a dye, a pigment, a lubricant, a surfactant, a plasticizer, a fragrance and the like can be added to the photosensitive resin composition (a) of the present invention depending on the purpose and purpose. .

  The laser-engravable printing original plate of the present invention is preferably one obtained by photocrosslinking and curing a photosensitive material containing inorganic porous fine particles to form a printing original plate layer (A). Therefore, a polymerizable unsaturated group of the organic compound (a-2), or a polymer and a polymerizable unsaturated group of the organic compound (a-2) react to form a three-dimensional crosslinked structure. Insolubilizes in ketone, aromatic, ether, alcohol and halogen solvents. This reaction occurs between the organic compounds (a-2), between the polymers, or between the polymer and the organic compound (a-2), and the polymerizable unsaturated group is consumed.

  In addition, when the photopolymerization initiator is used for crosslinking and curing, the photopolymerization initiator is decomposed by light. Therefore, the cross-linked cured product is extracted with a solvent, and mass-separated by GC-MS (gas chromatography). Analysis method), LC-MS method (method for mass spectrometry of those separated by liquid chromatography), GPC-MS method (method for separation and mass spectrometry by gel permeation chromatography), LC-NMR method (liquid chromatography) By analyzing using the method of analyzing the product separated in (1) by nuclear magnetic resonance spectrum, unreacted photopolymerization initiator and decomposition products can be identified. Furthermore, by using GPC-MS method, LC-MS method, GPC-NMR method, unreacted polymer, unreacted organic compound (a-2), and polymerizable unsaturated group in the solvent extract are reacted. The relatively low molecular weight product obtained in this way can also be identified from the analysis of the solvent extract.

  For the high molecular weight component insoluble in the solvent in which the three-dimensional cross-linked structure is formed, by using the pyrolysis GC-MS method, the site formed by the reaction of the polymerizable unsaturated group is formed as a component constituting the high molecular weight body. It is possible to verify whether it exists. For example, it can be estimated from the mass spectrometry spectrum pattern that there is a site where a polymerizable unsaturated group such as a methacrylate group, an acrylate group, or a vinyl group has reacted. The pyrolysis GC-MS method is a method in which a sample is thermally decomposed and a gas component to be generated is separated by gas chromatography and then mass spectrometry is performed. The decomposition product derived from the photopolymerization initiator and the unreacted photopolymerization initiator are detected together with the unreacted polymerizable unsaturated group or the site obtained by the reaction of the polymerizable unsaturated group in the crosslinked cured product. Then, it can be concluded that the photosensitive resin composition was obtained by photocrosslinking and curing.

The printing original plate layer (A) of the present invention is preferably in the form of a sheet or a cylinder, and a known forming method can be used as a method for forming the printing original plate layer (A). From the viewpoint of production efficiency of the printing original plate layer (A), in the present invention, the photosensitive resin (a) is preferably formed into a sheet shape or a cylindrical shape by a known method and photocured to form a printing original plate layer.
The existing resin molding method can be used for the method of shaping the photosensitive resin composition (a) of the present invention 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 calendaring with a roll can be exemplified. At that time, it is possible to perform molding while heating within a range that does not deteriorate the performance of the resin. Moreover, you may perform a rolling process, a grinding process, etc. as needed.

  Usually, it is often formed on an underlay called a back film made of a material such as polyethylene terephthalate (PET) or nickel, but it may be directly molded on a cylinder of a printing press. In particular, when the printing original plate layer (A) is formed into a sheet, it is preferably formed on the back film. The role of the back film is to ensure the dimensional stability of the printing original layer (A). Therefore, it is necessary to select one having high dimensional stability. When evaluated using the linear thermal expansion coefficient, the upper limit value of a preferable material is 100 ppm / ° C. or less, more preferably 70 ppm / ° C. or less.

  Specific examples of materials include polyester resin, polyimide resin, polyamide resin, polyamideimide resin, polyetherimide resin, polybismaleimide resin, polysulfone resin, polycarbonate resin, polyphenylene ether resin, polyphenylene thioether resin, epoxy resin, and the like. You can also. Further, these resins can be used in a laminated manner. For example, a sheet obtained by laminating a 50 μm thick PET layer on both sides of a 4.5 μm thick wholly aromatic polyamide film may be used. The thickness of the back film is 1 μm or more and 500 μm or less, more preferably 10 μm or more and 500 μm or less, and still more preferably 50 μm or more and 300 μm or less from the viewpoint of handleability.

  Examples of a method for reducing the linear thermal expansion coefficient of the back film include a method of adding a filler, a method of impregnating or coating a resin on a mesh cloth such as wholly aromatic polyamide, or a glass cloth. As the filler, generally used organic fine particles, inorganic fine particles such as metal oxides or metals, organic / inorganic composite fine particles, and the like can be used. In addition, porous fine particles, fine particles having cavities therein, microcapsule particles, and layered compound particles in which a low-molecular compound is intercalated can be used. In particular, metal oxide fine particles such as alumina, silica, titanium oxide, and zeolite, latex fine particles made of polystyrene / polybutadiene copolymer, natural product-based organic fine particles such as highly crystalline cellulose, and the like are useful.

Moreover, an adhesive layer can also be provided between the printing original plate layer (A) and the back film for the purpose of enhancing the adhesion of the printing original plate layer (A) back film. A known adhesive can be used for the adhesive layer, and examples thereof include (meth) acrylic resins, silicone resins, block copolymers having polystyrene blocks, and polyamides. Furthermore, “Encyclopedia of Adhesion / Adhesion” (supervised by Shozaburo Yamaguchi, published by Asakura Shoten Co., Ltd., 1986) can be referred to.
By performing a physical and chemical treatment on the surface of the back film used in the present invention, it is possible to improve the adhesion with the printing original plate layer (A) or the adhesive layer. Examples of the physical treatment method include a sand blast method, a wet blast method in which a liquid containing fine particles is sprayed, a corona discharge treatment method, a plasma treatment method, an ultraviolet ray or vacuum ultraviolet ray irradiation method, and the like. The chemical treatment method includes a strong acid / strong alkali treatment method, an oxidizing agent treatment method, a coupling agent treatment method, and the like.

  When the printing original plate layer (A) is cylindrical, the printing original plate layer molded into a sheet is formed on a cylindrical support with a known double-sided pressure-sensitive adhesive tape, a cushion tape having a double-sided pressure-sensitive adhesive layer, and an adhesive layer. It can also be fixed in a cylindrical shape. Examples of the double-sided pressure-sensitive adhesive tape include a tape obtained by applying an acrylic resin, a methacrylic resin, and a styrene-based thermoplastic elastomer to a film such as a polyester film or a polyolefin film. Furthermore, a commercially available adhesive tape can also be used. Examples of the cushion tape having a double-sided pressure-sensitive adhesive layer include a cushion tape obtained by applying a pressure-sensitive adhesive such as an acrylic resin to a polyolefin resin such as polyethylene or a polyurethane resin foam. Moreover, the cushion tape which has a commercially available double-sided adhesive layer can also be used.

As the adhesive layer, a known adhesive can be used, and a commercially available adhesive can be used. Examples thereof include rubber adhesives such as styrene butadiene rubber (SBR), chloroprene rubber and nitrile rubber, and adhesives that are cured by moisture in the air, such as polyurethane resins and silicone resins containing silyl groups.
In addition, when the printing original plate layer (A) is formed into a cylindrical shape, the printing original plate layer (A) can be directly formed on the cylindrical support. However, from the viewpoint of productivity, it is preferable that the photosensitive resin composition (a) is molded on a cylindrical support by a known method and then photocured, and subjected to rolling treatment and grinding treatment as necessary.

The cylindrical support used in the present invention includes a metal sleeve made of a metal such as nickel, stainless steel, iron, and aluminum, a plastic sleeve, a fiber reinforced plastic sleeve made of glass fiber, carbon fiber, aramid fiber, or the like, and a polymer. A film sleeve or the like can be used.
The thickness of these cylindrical supports can be from 0.1 mm for thin ones and 5 mm or more for thick ones. The cylindrical support generally used in the present invention has a characteristic that the inner diameter of the cylindrical support can be expanded with a compressed air pressure of about 6 bar, and returns to the original inner diameter after the compressed air pressure is released. It is preferable. The sleeve tightening characteristics of the sleeve core layer function on the printing cylinder so that they are fixed on the plate cylinder and can be used without any trouble in printing.

  The formed photosensitive resin composition (a) layer is cross-linked by light irradiation to form a printing original plate layer (A). Moreover, it can also bridge | crosslink by light irradiation, shaping | molding. 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 germicidal lamp, a carbon arc lamp, a xenon lamp, and a metal halide lamp. The light applied to the photosensitive resin composition (a) layer preferably has a light of 200 nm to 300 nm. In particular, since many hydrogen abstraction type photopolymerization initiators have strong light absorption in this wavelength region, it is preferable to have light having a wavelength of 200 nm to 300 nm because the curability of the surface of the cured photosensitive resin layer can be secured. . Although one type of light source may be used for curing, 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. Absent.

The thickness of the printing original layer (A) used for laser engraving may be arbitrarily set according to the purpose, but when used as a printing plate, a thickness of 0.1 to 7 mm is generally preferable. In some cases, a plurality of materials having different compositions may be stacked.
An elastomer cushion layer made of an elastomer can be formed in the lower layer of the printing original plate layer (A) of the present invention. Since the thickness of the layer to be laser engraved is generally 0.1 to several mm, the other lower layers may be made of materials having different compositions. The elastomer cushion layer is preferably an elastomer having a Shore A hardness of 20 to 70 degrees. When the Shore A hardness is 20 degrees or more, the printing quality can be ensured because of appropriate deformation. A more preferred Shore A hardness range is 30 to 60 degrees.

The elastomer cushion layer is not particularly limited and may be anything as long as it has rubber elasticity such as a thermoplastic elastomer, a photocurable elastomer, and a thermosetting elastomer. It may be a porous elastomer layer having nanometer-level micropores. In particular, from the viewpoint of workability, it is preferable to use a liquid type photosensitive resin composition and a material that becomes an elastomer after curing.
Specific examples of the thermoplastic elastomer used in the elastomer cushion layer include styrene-based thermoplastic elastomers such as polystyrene-polybutadiene-polystyrene block copolymer, polystyrene-polyisoprene-polystyrene block copolymer, polystyrene-polyethylene / polybutylene-polystyrene block copolymer, and the like. Examples thereof include olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, ester-based thermoplastic elastomers, amide-based thermoplastic elastomers, silicon-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers.

  Examples of the photocurable elastomer include those obtained by mixing the thermoplastic elastomer with a photopolymerization monomer, a plasticizer and a photopolymerization initiator, and liquid components obtained by mixing a plastomer resin with a photopolymerization monomer, a photopolymerization initiator, and the like. . Moreover, non-sulfur cross-linked rubbers such as sulfur cross-linked rubbers, organic peroxides, phenol resin initial condensates, quinone dioximes, metal oxides, and thioureas can also be used. Further, an elastomer obtained by three-dimensional crosslinking using an oxidizing agent that reacts with a telechelic liquid rubber can also be used.

  By forming the modified layer on the surface of the laser engraving plate, it is possible to reduce the tack of the printing plate surface and improve the ink wettability. Examples of the modifier include a film treated with a compound that reacts with a surface hydroxyl group such as a silane coupling agent or a titanium coupling agent, or a polymer film having porous inorganic particles. As the silane coupling agent and the titanium coupling agent, for example, each coupling agent described in JP-A-2004-314334 can be used.

  In laser engraving, a laser is operated using a computer as an image to be formed as digital data, and a relief image is formed on the original. Any laser can be used for the laser engraving as long as it contains a wavelength that can be absorbed by the original, but a laser with a high output is desirable for engraving at a high speed, such as a carbon dioxide laser or a YAG laser. Infrared emitting solid lasers such as semiconductor lasers are preferred.

  In addition, ultraviolet lasers having a transmission wavelength in the ultraviolet region, such as excimer lasers, YAG lasers that have been converted to the third or fourth harmonic, and copper vapor lasers are capable of ablation processing that breaks the bonds of organic molecules. Suitable for processing. The laser may be continuous irradiation or pulsed laser. 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 helps 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 preferable to add a dye or a pigment, which is a component that assists in absorption.

  Examples of such dyes include poly (substituted) phthalocyanine compounds and metal-containing phthalocyanine compounds; cyanine compounds; squalium dyes, chalcogenopyrroloarylidene dyes; chloronium dyes; metal thiolate dyes; bis (chalcogenopyrrillo) polymethine dyes; And 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, The thing doped with Mg, P, Co, Ni, Y etc. is mentioned. These dyes and pigments may be used alone, in combination of a plurality, or in any form such as a plurality of structures.

  In the present invention, when the laser engraving printing original plate is irradiated with laser light to form a concave pattern, the surface of the laser engraving printing original plate can be heated to assist the laser engraving. Examples of the method for heating the laser engraving printing original plate include a method of heating a cylindrical surface plate of a laser engraving machine using a heater, and a method of directly heating the surface of the laser engraving printing original plate using an infrared heater. The laser engraving property can be improved by this heating step. The degree of heating is preferably in the range of 50 ° C to 200 ° C, more preferably in the range of 80 ° C to 200 ° C, and still more preferably in the range of 100 ° C to 200 ° C.

  In the present invention, it is necessary to combine different laser conditions with at least one halftone dot area ratio of 5% or more and 40% or less of a halftone dot area ratio in one printed image as a boundary. From the viewpoint of print quality, particularly dot gain quality, the halftone dot area ratio is 5% to 40%, preferably 5% to 30%, and more preferably 10% to 30%. This range of 5% or more and 40% or less is preferable because the print reproduction area at the halftone dot can be expanded and the dot gain can be suppressed.

  The halftone dot area ratio in the present invention refers to the halftone dot area ratio described in “Enhanced Printing Encyclopedia” (edited by the Japan Printing Society, published in 1987). That is, the halftone dot area in the halftone tone is the ratio of the unit area, and is usually expressed as a percentage. In the present application, the halftone dot area ratio is a value measured by using the method described in “Enhanced Printing Encyclopedia” (edited by the Japan Printing Association, published in 1987). That is, assuming that each halftone dot density is very high, the transmission (reflection) density within a certain area is measured, and the halftone dot area ratio is converted from this. The conversion method is publicly known and can be used in the present invention. In the present invention, the expression by Murray-Davis described in “Printing Engineering Handbook” (edited by the Japan Printing Society, published in 1983) is used.

  When laser engraving using a single laser engraving machine, laser engraving is performed by controlling the laser conditions according to a plurality of laser conditions. Examples of the laser conditions include laser engraving speed, resolution, halftone dot height, halftone dot angle represented by the laser output intensity, the laser oscillator, or the moving speed of the printing original plate layer (A). In particular, it is preferable to change the dot height and the dot angle in the present invention in consideration of the dot gain that affects the print quality.

  The halftone dot height means the resin thickness of the halftone dot portion in the printing original plate layer (A) subjected to laser engraving, and is obtained by measuring the resin thickness. In the printing original plate layer (A) subjected to laser engraving, the printing surface is regarded as the top and the opposite surface is regarded as the bottom. In the present invention, it is expressed as halftone dot height. Similarly, for the solid portion, the solid portion height can be obtained by measuring the resin thickness in the solid portion.

This solid portion and halftone dot height can be measured by a known technique, for example, using a caliper, a micro gauge, or a dial gauge.
In the present invention, it is preferable to change the difference between the halftone dot height and the solid portion height, but the halftone dot portion height is more preferably lower than the solid portion height in the range of 0 μm to 500 μm, It is preferable from the viewpoints of print quality and halftone dot formation that the thickness is preferably changed from 0 to 300 μm, particularly preferably from 0 to 200 μm.
In laser engraving, the difference between the dot height and the solid portion height can be changed by engraving the surface of the portion to be lowered. However, from the viewpoint of dot gain, it is preferable to make the halftone dot portion lower than the solid portion.

Compared to the solid part, halftone dot height is obtained by performing laser engraving by controlling laser oscillation for the part corresponding to the height to be lowered and the part corresponding to the valley for creating dots that form halftone dots. The height can be made lower than the solid part height. More specifically, for the top of the dot portion of the halftone dot portion, laser oscillation is performed only at a height that is lower than the solid portion, and for the portion corresponding to the valley of the dot portion, further laser oscillation is performed, Can be sculpted.
The halftone dot angle is an angle that forms the top of a dot that forms a halftone dot. The halftone dot angle is preferably changed in a range where the halftone dot angle is 0 ° or more and 60 ° or less, and the halftone dot area ratio is 70% or less, more preferably 15 ° or more and 60 ° or less, and even more preferably 30 °. It is 60 degrees or less. Within this range, a dot shape with good print quality, particularly dot gain quality, can be obtained.

The halftone dot angle can be adjusted by three-dimensionally controlling laser oscillation for laser engraving.
In addition, the halftone dot angle is measured by cutting out the halftone dot portion, enlarging the cross section with an optical microscope, and measuring using a protractor, etc., or performing shape observation using a laser scanning type three-dimensional surface shape apparatus. From the observation result, the angle may be measured using a protractor.
The method of changing the laser conditions with at least one halftone dot area ratio of halftone dot area ratio of 5% or more and 40% or less is to perform laser engraving under one condition only below the halftone dot area ratio. Then, it is obtained by performing the dot area ratio which is the boundary or more under different laser engraving conditions. Alternatively, the laser engraving conditions may be automatically switched on the software for controlling laser engraving at the boundary of at least one dot area ratio. In this case, a dot diameter corresponding to the dot area ratio serving as a boundary is calculated in advance, and the laser engraving condition can be determined based on the dot diameter.

  Engraving with a laser can use a known technique, and is described in, for example, Japanese Patent Application Laid-Open No. 2001-146064. The composition data created by a composition creating apparatus such as a computer is read into a laser engraving control device via a floppy (registered trademark) disk, MO disk, CD, DVD, portable hard disk, LAN, or the like. The control device analyzes the composition data according to the machining control program and creates an execution file. Next, the printing original plate layer (A) is placed on a laser engraving machine, and the start of engraving is commanded. Thereafter, the laser head portion is set at the initial processing position, the laser is output to the portion corresponding to the concave portion, and a printing plate can be obtained.

  Laser engraving is carried out in an oxygen-containing gas, generally in the presence of air or an air stream, but can also be carried out in the presence of carbon dioxide or nitrogen gas. After engraving is completed, the powdery or liquid substance slightly generated on the surface of the relief printing plate is irradiated with an aqueous cleaning agent by an appropriate method, for example, a method of washing with water containing a solvent or a surfactant, or a high-pressure spray. You may remove using the method, the method of irradiating a high pressure steam, etc.

  The original plate of the present invention includes a relief image for printing, a stamp / stamp, a design roll for embossing, a relief image for patterning an insulator, a resistor, and a conductor paste used for creating an electronic component, and an antireflection film for an optical component. , Color filters, pattern formation of functional materials such as (near) infrared absorption filters, alignment films, base layers, light-emitting layers, electron transport layers, sealant layers in the production of display elements such as liquid crystal displays or organic electroluminescent displays It can be applied to various uses such as coating film / pattern formation of ceramics, relief images for molds of ceramic products, relief images for displays such as advertisements and display plates, and prototypes / moulds of various molded products.

Hereinafter, although it demonstrates in detail based on an Example, the technical scope of this invention is not limited to these Examples.
Unless otherwise specified, the composition described below is in parts by weight.
(1) Laser engraving Laser engraving was carried out using a carbon dioxide laser engraving machine (trademark: TYPSTAPLAS SN 09, manufactured by BAASEL). For engraving, a pattern including a halftone dot (100 lines per inch, 5%, 10%, 20%, 30%, 50%) and a solid portion (100% area ratio) was created, and laser engraving was performed. If the engraving depth is set large, the area of the top portion of the fine halftone dot pattern cannot be secured, and the shape is broken and unclear, so the engraving depth was set to 0.55 mm.
(2) Printing evaluation Printing evaluation was performed on a polyethylene film with a solvent ink using flexo rotary printing at a printing speed of 100 m / min. The anilox used was 800 line per inch. The printing pressure was adjusted so that no blur was observed in the solid portion (area ratio 100%), and printing was performed.
(3) Printed matter evaluation test The halftone dot area ratio was measured using a halftone dot area ratio measuring device (trademark “VIPFLEX 334”, manufactured by VIPTRONIC GmbH).
(4) Plate thickness measurement A digital indicator (trademark: ABS Digimatic Indicator ID-C112 model, manufactured by Mitutoyo Corporation) was fixed to a stand, and the plate pressure was measured.
(5) Halftone dot angle measurement A halftone dot portion of the printing plate was cut out, and a cross-section was observed using an optical microscope. The halftone dot angle was determined from this cross section.

[Example 1]
(1) Preparation of liquid photosensitive resin composition Trademark “PCDL L4672” (number average molecular weight 1990, OH value) which is a polycarbonate diol manufactured by Asahi Kasei Chemicals Co., Ltd. on a 1 L Sepacel flask equipped with a thermometer, a stirrer and a refluxing device. 56.4) 447.24 g and tolylene diisocyanate 30.83 g were added and reacted at 80 ° C. for about 3 hours, followed by addition of 7.42 g of 2-methacryloyloxyisocyanate and further reaction for about 3 hours. Thus, a resin (A) having a number average molecular weight of 10,000 having a terminal methacrylic group (average number of polymerizable unsaturated groups in the molecule per molecule) was produced. This resin was in the form of a syrup at 20 ° C., and flowed when an external force was applied, and did not recover to its original shape even when the external force was removed.
The resin (A) was used as the resin, and as shown in Table 1, the trademark “Syrosphere C-1504” (hereinafter, referred to as “porous silica”, organic compound, photopolymerization initiator, manufactured by Fuji Silysia Co., Ltd.) Abbreviated C-1504, number average particle diameter 4.5 μm, specific surface area 520 m ² / g, average pore diameter 12 μm, pore volume 1.5 ml / g, loss on ignition 2.5 wt%, oil absorption 290 ml / 100 g), Other additives were added to prepare photosensitive resin 1.
Photosensitive resin 1 was liquid at 20 ° C. The viscosity measured using a B-type viscometer was 5 kPa · s or less at 20 ° C.

(2) Preparation of printing original plate This photosensitive resin 1 was formed on a PET film with a thickness of 1.4 mm, and a relief surface of 2000 mJ / cm ^{2 in the} atmosphere using an ALF type 213E exposure machine manufactured by Asahi Kasei Corporation. Then, exposure was performed under the condition of a back surface of 1000 mJ / cm ² to obtain a printing original plate 1. The light used for exposure was ultraviolet fluorescent light (chemical lamp, center wavelength: 370 nm) and germicidal lamp (germicidal lamp, center wavelength: 253 nm).

(3) Laser engraving The original printing plate 1 was laser engraved using a carbon dioxide laser, but the engraving conditions for parameter A were searched while measuring the height of the 5% halftone dot area. Sometimes, the difference between the 5% halftone dot height and the solid part height was 0 mm, and when the parameter B was 70, the 5% halftone dot height was 0.06 mm lower than the solid part halftone dot height.
A halftone dot area having a halftone dot area ratio of less than 20% was subjected to laser engraving with a parameter A of 76, and a halftone dot area of 20% or more was set to a parameter A of 70 to obtain a printing plate 1. After the laser engraving, the engraving residue slightly remaining on the surface was washed with high-pressure steam at a pressure of 5 MPa. Table 2 shows the height of each halftone dot region and the height of the solid portion.

(4) Printed matter evaluation test When printing was performed using the printing plate 1 and the area ratio of each halftone dot portion was determined, it was as shown in Table 2, and a good printed matter in which a 5% halftone dot region was printed was obtained. I was able to get it.

[Comparative Example 1]
(1) Preparation of liquid type photosensitive resin composition A liquid type photosensitive resin composition was prepared in the same manner as in Example 1 to obtain photosensitive resin 1.
(2) Creation of printing original plate The printing original plate was produced similarly to Example 1, and the printing original plate 1 was obtained.
(3) Laser engraving Laser engraving and washing were carried out in the same manner as in Example 1 except that laser engraving was performed with parameter A being set to 70 in the entire halftone dot region, and printing plate 2 was obtained.
(4) Printed matter evaluation test When a printing test was performed using the printing plate 2 in the same manner as in Example 1, 5% halftone dots and 10% halftone dots were not printed, resulting in a narrow reproduction area of the printed matter. It was.

[Example 2]
(1) Preparation of liquid type photosensitive resin composition A liquid type photosensitive resin composition was prepared in the same manner as in Example 1 to obtain photosensitive resin 1.
(2) Creation of printing original plate The printing original plate was produced similarly to Example 1, and the printing original plate 1 was obtained.
(3) Laser engraving Laser engraving is performed in the same manner as in Example 1 except that parameter A is set to 74 when the dot area ratio is less than 10%, and parameter A is set to 72 when the dot area ratio exceeds 10%. The printing plate 3 was obtained by washing.
(4) Printed matter evaluation test When printing was performed using the printing plate 3 and the area ratio of each halftone dot portion was determined, it was as shown in Table 2, and a good printed matter in which a 5% halftone dot region was also printed was obtained. I was able to get it.

[Comparative Example 2]
(1) Preparation of liquid type photosensitive resin composition A liquid type photosensitive resin composition was prepared in the same manner as in Example, and a photosensitive resin 1 was obtained.
(2) Creation of printing original plate The printing original plate was produced similarly to Example 1, and the printing original plate 1 was obtained.
(3) Laser engraving The printing plate 4 was obtained by carrying out laser engraving and washing in the same manner as in Example 1 except that parameter A was set to 80 and laser engraving was performed in the entire halftone dot region.
(4) Printed matter evaluation test A printing test was performed using the printing plate 4 in the same manner as in Example 1. As a result, a printed matter with a large 50% halftone dot was obtained, and a good printed matter could not be obtained.

[Example 3]
(1) Preparation of liquid type photosensitive resin composition A liquid type photosensitive resin composition was prepared in the same manner as in Example, and a photosensitive resin 1 was obtained.
(2) Creation of printing original plate The printing original plate was produced similarly to Example 1, and the printing original plate 1 was obtained.
(3) Laser engraving When the printing original plate 1 was laser engraved using a carbon dioxide laser, the engraving conditions were searched for parameter B while measuring the angle of the 5% halftone dot area, and when parameter B was 20. The angle of the 5% halftone dot was 20 °, and when the parameter B was 40, the angle of the 5% halftone dot was 30 °.
Engraving was performed with a dot area ratio of less than 20% as a parameter B as 40 and a dot area of 20% or more as a parameter B as 20 and a printing plate 5 was obtained. After the laser engraving, the engraving residue slightly remaining on the surface was washed with high-pressure steam at a pressure of 5 MPa. Table 3 shows the height of each halftone dot region and the height of the solid portion.
(4) Printed matter evaluation test When printing was performed using the printing plate 5 and the area ratio of each halftone dot portion was determined, it was as shown in Table 3, and a good printed matter in which a 5% halftone dot region was also printed was obtained. I was able to get it.

[Comparative Example 3]
(1) Preparation of liquid type photosensitive resin composition A liquid type photosensitive resin composition was prepared in the same manner as in Example, and a photosensitive resin 1 was obtained.
(2) Preparation of printing original plate A printing original plate was prepared in the same manner as in Example 1 to obtain a printing original plate 1.
(3) Laser engraving Laser engraving and washing were performed in the same manner as in Example 3 except that the entire halftone dot area was engraved with parameter B set to 20, and a printing plate 6 was obtained.
(4) Printed matter evaluation test When a printing test was conducted in the same manner as in Example 1 except that the printing plate 6 was used, 5% halftone dots and 10% halftone dots were not printed, resulting in a narrow reproduction area of the printed matter. It was.

  The present invention can be suitably used as a production method capable of laser engraving a printing plate with good printing quality from a printing original plate.

The schematic diagram of the printing plate of this invention. The schematic diagram of the engraving parameter used for Examples 1-3 and Comparative Examples 1-3.

Explanation of symbols

1: Halftone dot part 2: Solid part 3: Dot forming halftone dot 4: Dot valley 5: Difference between halftone dot height and solid part height 6: Halftone dot angle

Claims (7)

A method for producing a printing plate for flexographic printing by laser engraving a printing original plate layer (A), wherein at least one halftone dot area ratio of halftone dot area ratio of 5% to 40% in one printed image A method for producing a printing plate for flexographic printing, characterized by combining laser engraving with different laser engraving conditions. The method for producing a printing plate for flexographic printing according to claim 1, wherein the difference between the halftone dot height and the height of the solid portion is changed. 3. The method for producing a printing plate for flexographic printing according to claim 2, wherein the height of the halftone dot portion is lower than the solid portion height in a range of greater than 0 [mu] m and less than or equal to 500 [mu] m. The method for producing a printing plate for flexographic printing according to claim 1, wherein the halftone dot angle is changed. 5. The printing plate for flexographic printing according to claim 4, wherein the halftone dot angle is changed in a range where the halftone dot angle is 0 ° or more and 60 ° or less in a region where the halftone dot area ratio is 70% or less. Manufacturing method. The method for producing a printing plate for flexographic printing according to any one of claims 1 to 5, wherein the printing original plate layer (A) is laminated on a cylindrical support. The printing original plate layer (A) consists of curing a photosensitive resin, a resin (a-1) having a number average molecular weight of 1,000 or more and 300,000 or less, and having a polymerizable unsaturated group in the molecule with a number average molecular weight of less than 1,000. The photosensitive resin composition (a) containing the organic compound (a-2) and the photopolymerization initiator (a-3) is photocured to form a printing original plate layer (A). The manufacturing method of the printing plate for flexographic printing in any one of.

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