JP2008246913A - Laser-engraved original printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser-engraved original printing plate, which does not generate printing defects and shows a superior resolution. <P>SOLUTION: This original printing plate can be engraved by laser and is made of a photosensitive resin composition containing (A) a hydrophobic polymer obtained from a water dispersive latex, (B) a photopolymer compound and (C) a photopolymerization initiator. After the composition is photo-crosslinked, the hydrophobic polymer as the component (A) is found in the fine particle shape with 0.03 to 2 μm average particle dia. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printing original plate for laser engraving. Specifically, it is a photosensitive resin composition containing (A) a hydrophobic polymer obtained from an aqueous dispersion latex, (B) a photopolymerizable compound, and (C) a photopolymerization initiator. The present invention relates to a laser-engravable printing original plate, wherein the hydrophobic polymer as the component (A) is present in the form of fine particles having an average particle size of 0.03 μm to 2 μm after crosslinking. When the printing original plate of the present invention is used, engraving residue generated at the time of laser engraving is small, dots having an ideal shape can be formed with high resolution, and printing with a long run is possible.

  Conventionally, a printing plate for flexographic printing used for printing packaging materials, building materials, and the like has been conventionally exposed to a printing original plate made of a photosensitive resin according to an image to crosslink the resin in the exposed portion, and then the unexposed portion in the unexposed portion. In recent years, printing plates by laser engraving that directly form a relief image on a printing original plate using a laser are becoming widespread in order to improve the efficiency of printing plate production. In the printing plate manufacturing process by laser engraving, unevenness is formed on the plate surface by irradiating the printing original plate with a laser beam according to the image to decompose the image forming material in the irradiated portion. At this time, a viscous resin residue is generated due to the decomposition of the image forming material in the laser irradiation portion, and a part thereof is scattered also in the non-laser irradiation portion. Since these resin wastes cause problems when left on the printing plate, they are removed from the printing plate by sucking with a dust collector provided near the laser device during laser irradiation and / or by washing the printing plate after laser irradiation. Removed.

  Conventionally, printing masters for laser engraving are known which comprise a resin composition in which a photopolymerizable compound and a photopolymerization initiator are blended with synthetic rubber or natural rubber (see Patent Documents 1 and 2). However, since this printing original plate is mainly composed of rubber, the original plate itself has high adhesiveness, and the resin residue generated by laser irradiation remains attached to the plate without being removed by suction during laser irradiation or cleaning after laser irradiation. Easy to remain. If the resin residue remains attached to the laser non-irradiated portion (convex portion) of the printing plate, this portion is a portion to which ink is applied at the time of printing, which may cause printing defects. In addition, if the resin residue remains attached to the bottom of the laser-irradiated portion (recessed portion) of the printing plate, the depth of the halftone dot will decrease, and if it remains attached to the side surface of the recessed portion, the reproducibility of the halftone dot will decrease. In either case, the resolution may be lowered.

In order to cope with this problem, the mechanical properties of the printing original plate can be improved by adding a laser-absorbing colored filler such as carbon black to the resin composition, or by adding a colorless transparent filler such as silica fine powder. There has been proposed a technique for improving and consequently reducing the adhesiveness (see Patent Document 3). However, the method of blending a laser-absorbing filler such as carbon black uses a colored filler, so that there is a problem that the resin composition becomes opaque and cannot be sufficiently cured by light irradiation. there were. In addition, the method of blending a filler such as silica fine powder is colorless and transparent, so that the problem as in the case of blending carbon black does not occur, but in order to sufficiently reduce the adhesiveness of the printing original plate, a large amount There was a problem that a filler was required and the moldability and physical properties of the printing original plate were remarkably impaired. Thus, since the addition of the filler adversely affects the moldability and physical properties of the printing original plate, development of a method capable of reducing the adhesiveness of the printing original plate without adding the filler has been demanded. .
Japanese Patent No. 2846954 JP-A-11-338139 Special table 2004-533343

  The present invention was devised in view of the current state of the prior art, and its purpose is to reduce engraving debris generated during laser engraving, to form dots with an ideal shape with high resolution, and for long runs. It is to provide a printing original plate that can be printed.

  As a result of intensive studies to achieve the above object, the present inventors have used a printing original plate in which the hydrophobic polymer component after photocrosslinking is present in the form of fine particles having an average particle size of 0.03 μm to 2 μm. As a result, it was found that these problems can be overcome, and the present invention has been completed.

That is, according to the present invention, there is provided a laser-engravable printing original plate characterized by the following:
(A) Hydrophobic polymer obtained from water-dispersed latex (B) Photopolymerizable compound (C) A photosensitive resin composition containing a photopolymerization initiator, wherein the photosensitive resin composition is photocrosslinked A laser-engravable printing original plate, wherein the hydrophobic polymer as the component (A) is present in the form of fine particles having an average particle size of 0.03 to 2 μm.

  According to a preferred embodiment of the present invention, in the photosensitive resin composition after photocrosslinking, the area ratio occupied by fine particles of 0.3 μm to 3 μm is 20% to 80%, and is at least one kind of hydrophobic polymer. Is a hydrophobic polymer having a degree of crosslinking of 40% or more. Further, the printing plate of the present invention has a tote shape or a cylindrical shape.

  In the laser-engravable printing original plate of the present invention, the hydrophobic polymer is present in the form of fine particles. For this reason, removal of engraving residue generated in laser engraving can be extremely easily performed. Also, an ideal dot shape can be formed with high resolution by laser engraving. Conventionally, laser engraving printing masters that have been used in the past are difficult to remove engraving debris generated by laser engraving because the hydrophobic polymer does not exist in the form of fine particles. It occurred.

  The printing original plate of the present invention is very suitable as a raw material for the laser engraving printing original plate, and comprises (A) a hydrophobic polymer (B) photopolymerizable compound (C) photopolymerization initiator obtained from an aqueous dispersion latex. The photosensitive resin composition contained, and after photo-crosslinking the photosensitive resin composition, the hydrophobic polymer as the component (A) exists in the form of fine particles having an average particle size of 0.03 μm to 2 μm. It is what.

  (A) The hydrophobic polymer obtained from the water-dispersed latex is present in the form of fine particles having an average particle size of 0.03 to 2 μm. “Present in the form of fine particles” means that, for example, morphological observation and phase distribution evaluation can be performed using a scanning probe microscope SPM to confirm the existence as independent fine particles. The fine particles preferably have a form dispersed in the photopolymerizable compound as the component (B). It is essential that the average particle size of the fine particles is 0.03 μm to 2 μm. Preferably, they are 0.06 micrometer-1 micrometer. More preferably, it is 0.1 micrometer-0.4 micrometer. When the average particle diameter of the fine particles exceeds 2 μm, it becomes difficult to remove engraving residue generated by laser engraving, and high resolution cannot be expressed.

  In the photosensitive resin composition after photocrosslinking, the area ratio of the fine particles is preferably 20% to 80%, more preferably 40% to 60%. If the area ratio is less than 20%, it becomes difficult to remove engraving residue, and at the same time, the rubber elasticity is lost, resulting in poor printability. On the other hand, when it exceeds 80%, the density of crosslinking caused by the component (B) becomes insufficient. For this reason, the resin plate cannot exhibit sufficient strength to withstand printing.

  Of the hydrophobic polymers present in the form of fine particles, at least one is preferably one having a crosslinking degree of 40% or more, and more preferably 70% or more. By using a hydrophobic polymer having a crosslinking degree of 40% or more, removal of engraving residue can be facilitated. Moreover, it becomes easy to form a fine particle state.

  As the latex (A) used in the present invention, a conventionally known latex can be used. Latex is an emulsion in which a polymer such as natural rubber, synthetic rubber or plastic is colloidally dispersed in water by the action of an emulsifier. Depending on the production process, (i) a natural product produced by the metabolic action of plants. A natural rubber latex is classified into (ii) a synthetic rubber latex synthesized by an emulsion polymerization method, and (iii) an artificial latex obtained by emulsifying and dispersing a solid rubber in water. Only (ii) synthetic rubber latex and (iii) artificial latex, and (i) does not include natural rubber latex.

  Specific examples include polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and the like. These latexes may be modified with (meth) acrylic or carboxy as desired. In addition, since many various synthetic | combination or natural latex is marketed as a crosslinked latex, what is necessary is just to select an appropriate thing from there. Moreover, latex can also use 2 or more types together.

  The photopolymerizable compound (B) constituting the resin composition of the present invention has a role of polymerizing and crosslinking by light irradiation to form a dense network for maintaining the shape on the printing original plate. As the photopolymerizable compound (B) used in the present invention, a photopolymerizable oligomer is preferable. Here, the photopolymerizable oligomer is a conjugated diene-based ethylenic polymer in which an ethylenically unsaturated group is bonded to the terminal and / or side chain of the conjugated diene-based polymer and has a number average molecular weight of 1000 or more and 10,000. Refers to:

  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. Examples of such a conjugated diene unsaturated compound homopolymer or a copolymer of a conjugated diene unsaturated compound and a monoethylenically unsaturated compound include a butadiene polymer, an isoprene polymer, a chloroprene polymer, a styrene-chloroprene copolymer, Acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, methyl methacrylate-isoprene copolymer, methyl methacrylate-chloroprene copolymer, methyl acrylate-butadiene copolymer, methyl acrylate-isoprene copolymer, Examples thereof include methyl acrylate-chloroprene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-chloroprene-styrene copolymer, and the like. Of these, butadiene polymers, isoprene polymers, and acrylonitrile-butadiene copolymers are preferable, and butadiene polymers and isoprene polymers are particularly preferable in terms of rubber elasticity and photocurability.

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

  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 / g in the polymer. It is. 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.

  As the photopolymerizable compound (B) of the present invention, photopolymerizable compounds such as acrylates and methacrylates that are generally used can be used in addition to those exemplified above. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) Alkyl (meth) acrylates such as acrylate, cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate, halogenated alkyl (meth) acrylates such as chloroethyl (meth) acrylate and chloropropyl (meth) acrylate, methoxyethyl (meth) Alkoxyalkyl (meth) acrylates such as acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate, noni Phenoxyalkyl (meth) acrylates such as phenoxyethyl (meth) acrylate can be mentioned, and particularly preferred are n-lauryl methacrylate, alkyl (C12-13) methacrylate, tridecyl methacrylate, alkyl (C12-15) methacrylate and the like. Can be mentioned.

  The (C) photopolymerization initiator constituting the resin composition of the present invention has a role as an initiator for the photopolymerization / crosslinking reaction of the (B) photopolymerizable compound. As the photopolymerization initiator (C) used in the present invention, any photopolymerization initiator can be used as long as it can polymerize a polymerizable carbon-carbon unsaturated group by light irradiation. Those having a function of generating radicals by autolysis or hydrogen abstraction are preferably used. Specifically, for example, benzoin alkyl ethers, benzophenones, anthraquinones, benzyls, acetophenones, diacetyls and the like can be used.

  In the resin composition of the present invention, the blending ratio of (A) latex, (B) photopolymerizable compound and (C) photopolymerization initiator is preferably 20 to 90% by mass, more preferably 40, (A) latex. -80 mass%, (B) the photopolymerizable compound is preferably 5-70 mass%, more preferably 20-60 mass%, and (C) the photopolymerization initiator is preferably 0.1-10 mass%. %, More preferably 0.1 to 7% by mass.

  In the resin composition of the present invention, optional components such as a hydrophilic polymer, a plasticizer, and / or a polymerization inhibitor can be blended as desired in addition to the above-mentioned three components (A) to (C).

  The hydrophilic polymer has an effect of improving the printing property by improving the affinity between the printing plate and the water-based ink when the flexographic printing is performed using the produced printing plate. The hydrophilic polymer that can be used in the resin composition of the present invention is -COOH, -COOM (M is a monovalent, divalent, or trivalent metal ion or a substituted or unsubstituted ammonium ion), -OH , —NH 2, —SO 3 H, and those having a hydrophilic group such as a phosphate ester group are preferred. Specifically, a polymer of (meth) acrylic acid or a salt thereof, (meth) acrylic acid or a salt thereof and an alkyl (meta ) A copolymer of acrylate, a copolymer of (meth) acrylic acid or a salt thereof and styrene, a copolymer of (meth) acrylic acid or a salt thereof and vinyl acetate, a (meth) acrylic acid or a salt thereof Copolymer with acrylonitrile, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide, hydroxyethyl cellulose, polyethylene Side, polyethyleneimine, polyurethane having -COOM group, polyureaurethane having -COOM group, include the polyamic acid and their salts or derivatives having a -COOM group. These may be used alone or in combination of two or more. The blending ratio of the hydrophilic polymer in the resin composition of the present invention is preferably 20% by mass or less, and more preferably 15% by mass or less. If the blending ratio of the hydrophilic polymer exceeds the above upper limit, the water resistance of the produced printing plate is lowered, and the water-based ink resistance may be lowered.

  The plasticizer has an effect of improving the fluidity of the resin composition and an effect of adjusting the hardness of the produced printing original plate. The plasticizer that can be used in the resin composition of the present invention is preferably a compound having good compatibility with (A) latex, and more preferably a polyene compound that is liquid at room temperature or a compound having an ester bond. Examples of the polyene compound that is liquid at room temperature include liquid polybutadiene, polyisoprene, and maleated products and epoxidized products obtained by modifying terminal groups or side chains thereof. 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. The blending ratio of the plasticizer in the resin composition of the present invention is preferably 30% by mass or less, and more preferably 20% by mass or less. When the blending ratio of the plasticizer exceeds the above upper limit, the mechanical properties and solvent resistance of the printing plate are remarkably lowered, and the printing durability may be lowered.

  The polymerization inhibitor has an effect of increasing the thermal stability of the resin composition. The polymerization inhibitor that can be used in the resin composition of the present invention may be a conventionally known one, and examples thereof include phenols, hydroquinones, and catechols. The blending ratio of the polymerization inhibitor in the resin composition of the present invention is preferably 0.001 to 3% by mass, and more preferably 0.001 to 2% by mass.

  Further, as optional components other than these, a colorant, an antioxidant and the like can be added within a range not impairing the effects of the present invention.

  The resin composition of the present invention is prepared by mixing the above-described three essential components (A) to (C) and optionally an optional component. At that time, an organic solvent such as toluene may be added as desired to facilitate mixing. Further, in order to complete the mixing, it is desirable to sufficiently knead under a heating condition using a kneader. It is preferable that heating conditions are about 50-110 degreeC. Moreover, it is preferable that the organic solvent added at the time of mixing and the water contained in the components are removed under reduced pressure after kneading.

  Next, the printing original plate capable of laser engraving of the present invention will be described. The printing original plate of the present invention is obtained by molding the resin composition of the present invention prepared as described above into a sheet or cylinder, and then irradiating the molded product with light to crosslink and cure. is there.

  As a method for molding the resin composition of the present invention into a sheet or cylinder, a conventionally known resin molding method can be used. For example, the resin composition of the present invention can be used on a suitable support or in a printing machine. The method of apply | coating on a cylinder and pressurizing with a heat press machine etc. can be mentioned. As the support, a material having flexibility and excellent dimensional stability is preferably used, and examples thereof include polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, and polycarbonate. The thickness of the support is from 50 to 250 μm, preferably from 100 to 200 μm, from the viewpoints of mechanical properties and shape stability of the printing original plate. Further, if necessary, a known adhesive conventionally used for this type of purpose may be provided on the surface in order to improve the adhesion between the support and the resin layer. The pressurization condition is preferably about 20 to 200 kg / cm 2, and the temperature condition during pressurization is preferably about room temperature to about 150 ° C. The thickness of the formed product may be appropriately determined depending on the size and properties of the printing original plate to be produced, and is not particularly limited, but is usually about 0.1 to 10 mm.

  Next, the molded resin composition is irradiated with light to polymerize and crosslink the (B) photopolymerizable compound in the resin composition, thereby curing the molded product to obtain a printing original plate. 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 printing original plate thus obtained is attached to the surface of the plate mounting drum of the laser engraving apparatus, and the irradiated portion of the original plate is decomposed by laser irradiation according to the image to form a concave portion, whereby a printing plate is manufactured. In the printing original plate of the present invention, since the hydrophobic polymer is present in the form of fine particles, the resin residue generated by laser irradiation is less likely to adhere to the plate surface, and printing defects and resolution reduction due to resin residue adhesion are effectively prevented. Is done.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

The characteristics were measured by the following method:-Average particle size and area ratio of fine particles Print original plate (thickness 1.7 mm) with a UV exposure machine (manufactured by A & V, lamp equipped with Philips 10R, illuminance 9 mW / cm ² ) The photosensitive resin composition was photocrosslinked by exposing every minute. Thereafter, the cover film and the anti-adhesion layer are peeled off, and the cured photosensitive layer is sliced in a frozen state using an ultramicrotome, and after drying, the slice surface, that is, the internal structure is scanned using a scanning probe microscope SPM. Evaluated. SPA300 (Seiko Instruments, SPI3800N system) was used for SPM. The measurement mode was DFM mode, and DF3 was used as the cantilever. Phase images were observed simultaneously with morphological observation in the DFM mode. Using an image analyzer V20 (an image processing device manufactured by Toyobo Co., Ltd.), the phase difference image is converted into a white color by using the TOKS method, and the other part is black. The average particle size and area ratio were determined.
(2) Crosslinking degree 3 g of the latex solution was accurately calculated on a 100 μm thick PET film, dried at 100 ° C. for 1 hour, then immersed in a toluene solution at 25 ° C. for 48 hours, and dried at 110 ° C. for 2 hours. Measured by calculating mass% of insoluble matter.

Example 1
(A) 90 parts by mass of styrene-butadiene latex as a latex (NALSTAR SR-101 manufactured by Nippon A & L: cross-linking degree 95%, average particle size 0.13 μm, nonvolatile content 46%), (B) oligobutadiene acrylate as a photopolymerizable compound (Molecular weight about 2700) 16 parts by weight, monofunctional methacrylate 10 parts by weight, trifunctional methacrylate 2 parts by weight, (C) benzyldimethyl ketal 1 part by weight as a photopolymerization initiator, liquid plastic butadiene rubber (molecular weight about 2,000) ) 10 parts by weight, 10 parts by weight of PFT-3 (compound with a molecular weight of about 20,000 having a urethane urea structure, nonvolatile content 25%) manufactured by Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer, hydroquinone monomethyl ether as a polymerization inhibitor 0.1 parts by mass in a container with 15 parts by mass of toluene And, then kneaded at 105 ° C. with a pressure kneader, followed by reducing the pressure to remove toluene and water to obtain a resin composition.

  Next, the obtained resin composition is a film in which a polyester adhesive layer is coated on a polyethylene terephthalate film having a thickness of 125 μm, and a film in which an adhesion preventing layer (polyvinyl alcohol) is coated on the same polyethylene terephthalate film (adhesive layer). The sheet-like molded product having a thickness of 1.7 mm was obtained by sandwiching the adhesive layer so that the anti-adhesion layer was in contact with the resin composition, and pressurizing with a heat press at 105 ° C. and a pressure of 100 kg / cm 2 for 1 minute. Next, this sheet-like molded product was exposed for 10 minutes on the front and back sides with an ultraviolet exposure machine (light source: 10R manufactured by Philips) and cured by crosslinking to prepare a printing original plate.

Example 2
(A) 27 parts by mass of styrene-butadiene latex (NALSTAR SR-101 manufactured by Nippon A & L: Crosslink degree: 95%, average particle size: 0.13 μm, nonvolatile content: 46%) as latex, (B) oligobutadiene acrylate as photopolymerizable compound (Molecular weight about 2700) 23 parts by weight, monofunctional methacrylate 10 parts by weight, trifunctional methacrylate 2 parts by weight, (C) benzyldimethyl ketal 1 part by weight as a photopolymerization initiator, liquid plastic butadiene rubber (molecular weight about 2,000) ) 10 parts by weight, 10 parts by weight of PFT-3 (compound with a molecular weight of about 20,000 having a urethane urea structure, nonvolatile content 25%) manufactured by Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer, hydroquinone monomethyl ether as a polymerization inhibitor 0.1 parts by mass in a container with 15 parts by mass of toluene And, then kneaded at 105 ° C. with a pressure kneader, followed by reducing the pressure to remove toluene and water to obtain a resin composition. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

Example 3
(A) Nitrile-butadiene latex as latex (Nippon A &L's Siatex NA-105S: degree of cross-linking 35%, average particle size 0.16 μm, non-volatile content 50%) 100 parts by mass, (B) oligobutadiene as photopolymerizable compound 15 parts by weight of acrylate (molecular weight of about 2700), 10 parts by weight of monofunctional methacrylate, 5 parts by weight of trifunctional methacrylate, (C) 1 part by weight of benzyldimethyl ketal as a photopolymerization initiator, liquid butadiene rubber (molecular weight of about 2, 000) 6 parts by weight, 10 parts by weight of PFT-3 (a compound having a urethane urea structure having a molecular weight of about 20,000, nonvolatile content of 25%) manufactured by Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer, hydroquinone monomethyl as a polymerization inhibitor 0.1 parts by weight of ether and 15 parts by weight of toluene in a container In mixed, then kneaded at 105 ° C. with a pressure kneader, followed by toluene and water was removed under reduced pressure to obtain a resin composition. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

Example 4
(A) Methyl methacrylate-butadiene latex as a latex (NALSTAR MR-170 manufactured by Nippon A & L Co., Ltd .: 100% crosslinking, average particle size 0.15 μm, nonvolatile content 45%) 180 parts by mass, (B) Oligobutadiene as a photopolymerizable compound 30 parts by weight of acrylate (molecular weight of about 2700), 5 parts by weight of monofunctional methacrylate, 3 parts by weight of trifunctional methacrylate, (C) 1 part by weight of benzyldimethyl ketal as a photopolymerization initiator, and Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer 10 parts by weight of PFT-3 (a compound having a urethane urea structure with a molecular weight of about 20,000, nonvolatile content of 25%) and 0.1 part by weight of hydroquinone monomethyl ether as a polymerization inhibitor were mixed in a container together with 15 parts by weight of toluene. Then knead at 105 ° C using a pressure kneader, and By removed in vacuo rear toluene and water to obtain a resin composition. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

Example 5
(A) Styrene-butadiene latex (JSR S2990S: degree of cross-linking 80%, average particle size 0.70 μm, non-volatile content 69%) 73 parts by mass as latex (B) oligobutadiene acrylate (molecular weight about 2700) as photopolymerizable compound ) 15 parts by weight, 10 parts by weight of monofunctional methacrylate, 5 parts by weight of trifunctional methacrylate, (C) 1 part by weight of benzyldimethyl ketal as a photopolymerization initiator, and 6 parts by weight of liquid butadiene rubber (molecular weight of about 2,000) as a plasticizer 10 parts by mass of PFT-3 (a compound having a urethane urea structure and a molecular weight of about 20,000, nonvolatile content of 25%) manufactured by Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer, 0.1 mass of hydroquinone monomethyl ether as a polymerization inhibitor Part in a container with 15 parts by weight of toluene, then pressurizing kneader Kneaded at 105 ° C. and have, then under reduced pressure to remove toluene and water to obtain a resin composition. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

Comparative Example 1
(A) Instead of latex, 30 parts by mass of butadiene rubber (BR02 made by Nippon Synthetic Rubber: degree of crosslinking 0%, Mooney viscosity 100 ° C .: 43), nitrile butadiene rubber (N220SH made by Japan Synthetic Rubber: degree of crosslinking 0%, Mooney viscosity) 100 ° C .: 80) 32 parts by mass, (B) 25 parts by mass of oligobutadiene acrylate (molecular weight of about 2700) as a photopolymerizable compound, 4 parts by mass of monofunctional methacrylate, 4 parts by mass of trifunctional methacrylate, (C) photopolymerization initiator 1 part by weight of benzyldimethyl ketal, 17 parts by weight of PFT-3 (a compound having a urethane urea structure with a molecular weight of about 20,000, nonvolatile content of 25%) manufactured by Kyoeisha Chemical Co., Ltd. as a hydrophilic polymer, as a polymerization inhibitor Hydroquinone monomethyl ether 0.1 parts by mass with toluene 60 parts by mass in a container, The kneaded at 105 ° C. with a pressure kneader, followed by vacuum removal of toluene to obtain a resin composition. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

Comparative Example 2
(A) 25 parts by mass of butadiene rubber (BR02 made by Nippon Synthetic Rubber, degree of crosslinking 0, Mooney viscosity 100 ° C .: 43) instead of latex, nitrile butadiene rubber (N220SH made by Japan Synthetic Rubber, degree of crosslinking 0%, Mooney viscosity) 100 ° C .: 80) 32 parts by mass, (B) 35 parts by mass of oligobutadiene acrylate (molecular weight of about 2700) as a photopolymerizable compound, 4 parts by mass of monofunctional methacrylate, 2 parts by mass of trifunctional methacrylate, (C) photopolymerization initiator As benzyl dimethyl ketal 1 part by weight, inorganic fine particles as silica (average primary particle diameter 0.017 μm) 20 parts by weight, and hydrophilic polymer PFT-3 (molecular weight about 20 having urethane urea structure) manufactured by Kyoeisha Chemical Co., Ltd. 000 compounds, nonvolatile content 25%) 17 parts by mass, hydroquinone monomethyl as a polymerization inhibitor The ether 0.1 part by weight were mixed in a container together with 60 parts by weight of toluene, then kneaded at 105 ° C. with a pressure kneader, followed by toluene removed under reduced pressure to obtain a resin composition. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

Comparative Example 3
(A) 100 parts by mass of styrene-butadiene rubber (SL552 manufactured by Nippon Synthetic Rubber, degree of cross-linking 0%, Mooney viscosity 100 ° C .: 55) instead of latex, 20 parts by mass of 1,6 hexanediol diacrylate, 1 part by mass of benzyldimethyl ketal The mixture was mixed with 0.1 part by mass of hydroquinone monomethyl ether as a polymerization inhibitor in a container together with 60 parts by mass of toluene, then kneaded at 105 ° C. using a pressure kneader, and then the toluene was removed under reduced pressure. A composition was obtained. Using this resin composition, a printing original plate was produced in the same manner as in Example 1.

  Next, the printing original plate produced in Examples 1-5 and Comparative Examples 1-3 was wound around the plate mounting drum of the laser engraving apparatus with a double-sided tape, and laser engraving was performed under the following conditions. Simultaneously with the start of laser engraving, the dust collector installed in the vicinity of the laser gun was operated, and the continuously engraved resin debris was discharged out of the apparatus. After laser engraving, the plate removed from the mounting drum was washed with water for 3 minutes with a water-developing plate-only washing machine (Toyobo CRS600, 1% washing soap aqueous solution, water temperature 40 ° C.) and adhered to the plate surface. A small amount of resin residue was removed and dried to obtain a printing plate.

As the laser engraving apparatus, a FlexPose! Direct equipped with a 300 W carbon dioxide laser manufactured by Luescher Flexo was used. The specifications of this apparatus were a laser wavelength of 10.6 μm, a beam diameter of 30 μm, a plate mounting drum diameter of 300 mm, and a processing speed of 1.5 hours / 0.5 m 2. The conditions for laser engraving are as follows. Note that (1) to (3) are conditions specific to the apparatus. Conditions can be arbitrarily set for (4) to (7), and the standard conditions of this apparatus are adopted for each condition.
(1) Resolution: 2540 dpi
(2) Laser pitch: 10 μm
(3) Drum rotation speed: 982 cm / sec (4) Top power: 9%
(5) Bottom power: 100%
(6) Shoulder width: 0.30mm
(7) Relief depth: 0.60 mm
(8) Evaluation image: 150 lpi, halftone dots in 1% increments from 0 to 100%

The following evaluation items were investigated for the obtained printing plate.
(1) Resin residue adhesion to the printing plate surface Using a 10x magnifier, visually check the resin residue adhesion to the printing plate surface. ◎: Almost no adhesion, ○: Slight adhesion , Δ: considerably adhered, x: severely adhered, indicated in four stages.
(2) 150 lpi minimum halftone dot reproducibility 150 lpi minimum halftone dot reproducibility was measured using a 10-fold magnifier.
(3) 150 lpi, 10% halftone dot depth 150 lpi, 10% halftone dot depth was measured using an ultra-depth color 3D shape measuring microscope (VK-9510 manufactured by Keyence Corporation).
(4) Number of printable sheets Printing was performed using a flexographic printing machine. The evaluation was based on the number of printed sheets that can achieve both the highlight portion and the shadow portion.
○: 10,000 sheets or more, Δ: 5000 to 10000 sheets, ×: 5000 sheets or less The evaluation results are shown in Table 1 below.

  From Examples 1 to 5 in which the hydrophobic polymer is present in the form of fine particles from the evaluation results of Table 1, there is little adhesion of resin residue to the printing plate surface, excellent reproducibility of fine halftone dots, and halftone dot depth. It can be seen that a deep printing plate is obtained. On the other hand, in Comparative Examples 1 to 3 in which the hydrophobic polymer is not present in the form of fine particles, a large amount of resin residue remains on the surface of the printing plate. The depth is also significantly inferior compared to Examples 1-5. Further, in Comparative Example 2 in which rubber was used as the elastomer and inorganic fine particles were blended, the amount of resin residue adhered was slightly lower than in Comparative Examples 1 and 3, and the reproducibility of fine halftone dots and the halftone dot depth were also slightly improved. However, it still does not reach Examples 1-5. From the above results, it is clear that the use of the printing original plate of the present invention can effectively suppress the adhesion of resin residue caused by laser irradiation and can produce a printing plate with excellent resolution.

The printing original plate of the present invention can be suitably used as a printing original plate for laser engraving, particularly in the field of flexographic printing, since resin residue generated by laser irradiation hardly remains attached to the plate surface.

Claims (4)

(A) Hydrophobic polymer obtained from water-dispersed latex (B) Photopolymerizable compound (C) A photosensitive resin composition containing a photopolymerization initiator, wherein the photosensitive resin composition is photocrosslinked A laser-engravable printing original plate, wherein the hydrophobic polymer as the component (A) is present in the form of fine particles having an average particle size of 0.03 to 2 μm.   2. The printing original plate according to claim 1, wherein in the photosensitive resin composition after photocrosslinking, the area ratio of fine particles having a particle diameter of 0.03 to 3 [mu] m is 20% to 80%.   The hydrophobic polymer obtained from the water-dispersed latex as the component (A) is at least one hydrophobic polymer having a degree of crosslinking of 40% or more. Original printing. A printing original plate capable of laser engraving, wherein the printing original plate according to claim 1 is in the form of a sheet or a cylinder.