JP2008225446A - Manufacturing method of original plate for letterpress printing, manufacturing method of letterpress printing plate, and composition for forming ink-receiving layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an original plate for letterpress printing which enables adjustment of spreading and light-shielding properties of light-shielding ink and peeling properties of a cover sheet as a protective layer and a manufacturing method thereof, and a composition for forming an ink-receiving layer, and to provide a manufacturing method of a letterpress printing plate. <P>SOLUTION: The original plate for letterpress printing includes a photosensitive resin layer and the ink-receiving layer provided on the photosensitive resin layer, and the ink-receiving layer contains at least two or more kinds of hydroxy alkyl cellulose differing in mass average molecular weight from each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink receiving layer forming composition for forming an ink receiving layer capable of holding a light-shielding ink, a relief printing original plate having an ink receiving layer formed using the ink receiving layer forming composition, and a relief printing plate. The present invention relates to a method for producing a printing plate.

  Photosensitive resins are generally used for letterpress printing plates such as flexographic printing plates. Specifically, the relief printing plate is a plate-like member in which at least a photosensitive resin layer is provided on a support. This photosensitive resin is generally composed of an elastomeric binder, at least one photopolymerizable monomer and a photopolymerization initiator.

  In the production of the flexographic printing plate, first, a film (mask) having a negative pattern of an image such as characters and images to be printed is placed on the photosensitive resin layer, and the actinic radiation is passed through the mask. Irradiate the photosensitive resin layer. The portion irradiated with actinic radiation is cured by a photopolymerization reaction. Thereafter, when the uncured portion is washed away with a developer, a convex pattern corresponding to the image remains. As a result, a flexographic printing plate is completed. In flexographic printing, ink is attached to the tip of the convex pattern and pressed against a printing medium such as paper to obtain a printed matter.

  However, since the mask is manufactured using a photochemical reaction using silver halide, the manufacturing is costly and the process is complicated. In addition, a technique has been proposed in which a negative pattern is printed by a printing apparatus such as an ink jet printer or a laser printer using an ultraviolet-absorbing light-shielding ink directly on the surface of the photosensitive resin layer. However, in this technique, since the light-shielding ink is directly printed on the surface of the photosensitive resin layer, the printed portion may be blurred or repelled, and a clear print pattern may not be obtained.

  Therefore, a relief printing original plate in which a photosensitive resin layer having photosensitivity to light in a predetermined wavelength region and an ink receiving layer in which a light shielding pattern is formed in the layer by a light shielding ink are laminated on a support. There is disclosed a relief printing original plate in which an ink receiving layer is transparent to light in a predetermined wavelength range and has a light-shielding ink retaining ability (see Patent Document 1).

As the component constituting the ink receiving layer of the relief printing original plate, a resin having a light-shielding ink retention ability and soluble or dispersible in a water-soluble or water-soluble organic solvent, or a resin that swells with these solvents is preferably used. Yes.
JP 2005-316325 A (published on November 10, 2005)

  Examples of components constituting the ink receiving layer described in Patent Document 1 include polyvinyl acetals such as polyvinyl butyral, polyvinyl pyrrolidone, polyacrylamide, polyurethane, polyvinyl propyl alcohol, and hydroxypropyl cellulose. However, in the ink receiving layer using these components, it is difficult to adjust the ink bleeding property, the light shielding property, and the peelability of the cover sheet as the protective layer.

  The present invention has been made in view of the above problems, and by controlling the ink bleeding property, the light shielding property, and the peelability of the cover sheet as a protective layer, the printing characteristics according to the type of ink can be obtained. An object of the present invention is to provide a relief printing original plate and a method for producing the same, a method for producing the relief printing plate, and a composition for forming an ink receiving layer.

The letterpress printing original plate according to the present invention is a letterpress printing original plate containing a photosensitive resin layer and an ink receiving layer provided on the photosensitive resin layer,
The ink receiving layer contains at least two hydroxyalkyl celluloses having different mass average molecular weights.

The method for producing a relief printing plate according to the present invention includes a pattern formation step of forming a light shielding pattern on the ink receiving layer of the relief printing original plate according to the present invention using a light shielding ink that blocks an exposure wavelength,
An irradiation step of irradiating the photosensitive resin layer with light in the wavelength region of the exposure wavelength, using the light shielding pattern as a mask, and
A resin layer forming step of forming a resin layer having a convex pattern for printing by removing a non-irradiated region of the photosensitive resin layer in an uncured state without being exposed to light in the wavelength region of the exposure wavelength, including.

  The composition for forming an ink receiving layer according to the invention contains at least two hydroxyalkyl celluloses having different mass average molecular weights.

  The method for producing a relief printing original plate according to the present invention includes forming an ink receiving layer on a photosensitive resin layer by heat melting.

  The relief printing original plate according to the present invention has at least two or more types of ink receiving layers containing hydroxyalkyl cellulose having different mass average molecular weights. Thus, an ink bleeding, light-shielding property, and peelability of a cover sheet as a protective layer can be adjusted, thereby providing a relief printing original plate capable of realizing printing characteristics according to the type of ink. be able to.

  In addition, the composition for forming an ink receiving layer according to the present invention includes the production of an ink receiving layer having improved ink bleeding by including at least two hydroxyalkyl celluloses having different mass average molecular weights. Can do.

  The method for producing a relief printing plate according to the present invention can adjust the ink bleeding property, the light shielding property, and the peelability of the cover sheet, which is a protective layer, by using the above relief printing original plate.

  Hereinafter, detailed embodiments of the present invention will be described.

1. Ink-Receiving Layer-Forming Composition The ink-receiving layer-forming composition of the present invention contains at least two hydroxyalkyl celluloses having different mass average molecular weights.

(Hydroxyalkyl cellulose)
Hydroxyalkyl cellulose is a component capable of holding a light-shielding ink, and the light-shielding ink holding ability varies depending on the molecular weight. Therefore, in this way, by including at least two or more kinds of hydroxyalkyl celluloses having different mass average molecular weights, the ink bleeding property, the light shielding property in the ink receiving layer and the peelability of the cover sheet as the protective layer can be adjusted. Accordingly, it is possible to realize printing characteristics corresponding to the type of ink.

The range of the weight average molecular weight of the hydroxyalkyl cellulose includes (A) 1 × 10 ^{4 to} 3 × 10 ⁵ and (B) 4 × 10 ⁵ to 1 × 10 ⁶ , preferably (A) 1 × 10 ⁵ to 2 × 10 ⁵ , (B) 8 × 10 ^{5 to} 9 × 10 ⁵ .

  The hydroxyalkyl cellulose is not particularly limited as long as it can play the above role. For example, the alkyl group is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and at least one of hydroxypropylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose can be used.

  By combining the above (A) and (B), it is possible to satisfactorily control ink bleeding. Moreover, it is preferable that mass ratio of said (A) and said (B) is (A) :( B) = 55: 45-95: 5. More preferably, (A) :( B) = 70: 30 to 90:10. If the ratio of (A) to (B) is in the above range, the bleeding property can be controlled well. In the present invention, adjusting the bleeding property means controlling the ease of bleeding and the difficulty of bleeding so that the optimum bleeding property can be obtained according to the ink to be held. For example, when using an ink that has a relatively large penetrant content and easily blots, it is preferable that the ratio of (A) is high within the above range, and an ink that has a relatively small penetrant content and hardly blots is used. In some cases, it is preferable that the proportion of (A) is low.

(Organic solvent)
The ink receiving layer forming composition of the present invention may further contain an organic solvent. By containing the organic solvent, it is possible to easily apply the ink-receiving layer-forming composition onto the photosensitive resin layer. The organic solvent is a solvent for dissolving or dispersing hydroxyalkyl cellulose, and is not particularly limited as long as it is a solvent capable of fulfilling the above role. Examples of the organic solvent include lower alcohols such as methanol, ethanol, isopropyl alcohol and isobutyl alcohol, ethers such as dibutyl ether, isopropyl ether and tetrahydrofuran, acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone and cyclohexanone. And ketones such as ethyl acetate, esters such as ethyl acetate, n-propyl acetate and n-butyl acetate, and aromatic hydrocarbons such as benzene, toluene and xylene. These organic solvents can be used alone or in combination.

(Other ingredients)
The composition for forming an ink receiving layer according to the present invention may contain a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerin, and sorbitol in addition to the above components. By including the polyhydric alcohol in the ink receiving layer, it is possible to improve the followability to the flexographic printing plate without impairing the recording characteristics of the water-based ink. In this case, the content of the polyhydric alcohol is preferably 40 parts by mass or less, more preferably 5 to 25 parts by mass with respect to 100 parts by mass of the resin in the ink receiving layer. When it is within the above range, the recording characteristics of the water-based ink can be improved.

  The ink receiving layer may contain a pigment in order to improve ink absorbability and prevent blocking. In addition to inorganic pigments such as silica, clay, talc, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, titanium oxide, synthetic zeolite, alumina, smectite, styrene resin, urethane resin, benzoguanamine resin, silicone resin, Organic pigments such as resin beads made of acrylic resin or the like, or hollow resin beads made of these as raw materials can be mentioned. Moreover, these can be used 1 type or in mixture of 2 or more types. The addition amount of the pigment is usually about 3 to 200 parts by mass with respect to 100 parts by mass of the total resin in the ink receiving layer composition.

  Further, the ink receiving layer forming composition may contain additives such as a leveling agent, an ultraviolet absorber, an antioxidant, and a chelating agent.

  An example of the ink that is particularly preferably used for the ink receiving layer formed using the ink receiving layer forming composition of the present invention will be described. Here, a light-shielding ink having characteristics that can absorb exposure light used for patterning a photosensitive resin layer, which will be described later, and block transmission, and that is well fixed to the ink receiving layer is exemplified. Specific examples include light-shielding inks containing water-soluble dyes, oil-based dyes, disperse dyes, organic solvent-soluble pigments, and the like that have high absorbability for light in the wavelength range of 300 nm to 450 nm.

  The water-soluble dye has a high absorption in the range of 300 nm or more and 450 nm or less in the absorption spectrum in water, and the solubility in water is usually 5% by mass or more, preferably 7% by mass or more. What is necessary is just to select suitably. Specific examples of such pigments include water-soluble copper phthalocyanine dyes, yellow dyes and brown dyes. Two or more of these water-soluble dyes may be used in combination.

  Examples of the water-soluble copper phthalocyanine dye include C.I. I. Direct Blue 86, 87, 199, C.I. I. Acid Blue 249 and the like, preferably C.I. I. Direct blue 86,199.

  Examples of the water-soluble yellow dye include C.I. I. Acid Yellow 17, 19, 23, 25, 39, 40, 42, 44, 49, 49, 61, 64, 76, 79, 100, 127, 135, 143, 151, 159, 169, 174, 190, 195 196, 197, 199, 218, 219, 220, 227, C.I. I. Direct yellow 1, 8, 11, 12, 24, 26, 27, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 110, 132, 142, 144, etc. Direct yellows 132 and 142 are preferable.

  Examples of the water-soluble brown dye include C.I. I. Direct Brown 1, 2, 6, 25, 27, 33, 37, 39, 59, 60, 62, 95, 99, 100, 104, 106, 112, 113, 115, 167, 169, 175, 195, 210, etc. And preferably C.I. I. Direct Brown 195.

  The water-soluble copper phthalocyanine dye usually has an absorption maximum at 550 to 650 nm and 300 to 400 nm, and the water-soluble yellow or brown dye usually has an absorption maximum at 350 to 450 nm. In addition, since the wavelength of the light source that can be used in the method for producing a relief printing plate of the present invention is usually 300 to 400 nm, the water-soluble copper phthalocyanine dye is used in order to efficiently absorb and shield the irradiated light. It is preferable to use a water-soluble yellow dye and / or a brown dye in combination.

  Specific examples of the oil-based dye include oil yellow 105, 107, 129, 3G, GGS, varifast yellow 1101, 1105, 4120 (all manufactured by Orient Chemical Co., Ltd.), Eisenspiron Red BEH, GEH, C-GH (both manufactured by Hodogaya Chemical Co., Ltd.) and the like.

  Furthermore, an ink containing a pigment such as carbon black can also be used.

For example, when the water-soluble dye is used, the light-shielding ink used in the present invention contains the water-soluble dye and is prepared using water as a medium. The water-soluble dye preferably contains a small amount of anions such as Cl ⁻ and SO ₄ ^2−, and the standard of the content is 5 as the total amount of Cl ⁻ and SO ₄ ^{2− in} the phthalocyanine dye. It is 1% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, and 1% by mass or less in the ink. In order to produce a water-soluble dye low in Cl ⁻ and SO ₄ ²⁻ , for example, a usual method using a reverse osmosis membrane, or a dried product or wet cake of a water-soluble dye is stirred in a mixed solvent of alcohol and water, What is necessary is just to desalinate by methods, such as filtration and drying. The alcohol used is a lower alcohol having 1 to 4 carbon atoms, preferably an alcohol having 1 to 3 carbon atoms, more preferably methanol, ethanol or 2-propanol. Moreover, you may employ | adopt the method of cooling and desalting after heating to the boiling point of the alcohol to be used in the case of the desalting process by alcohol. The content of Cl ⁻ and SO ₄ ²⁻ can be measured, for example, by ion chromatography.

  As the light-shielding ink that can be held by the ink receiving layer of the present invention, an ink having a small content of heavy metals (ions) such as zinc and iron and metals (cations) such as calcium and silica contained in the water-soluble dye is used. Are preferred (except for metals in the skeleton of the dye structure, for example copper in the phthalocyanine skeleton). The content is, for example, about 500 ppm or less for each of the heavy metals (ions) such as zinc and iron and the metals (cations) such as calcium and silica in the purified and dried pigment. The contents of heavy metals (ions) and metals (cations) can be measured by ion chromatography, atomic absorption, or ICP (Inductively Coupled Plasma) emission spectrometry.

  The dye or pigment is contained in the light-shielding ink in an amount of 5 to 20% by mass, preferably 5 to 15% by mass.

  The light-shielding ink used in the present invention can further contain a water-soluble organic solvent as necessary within a range that does not impair the effects of the present invention. This water-soluble organic solvent is used as a dye dissolving agent, a drying inhibitor (wetting agent), a viscosity modifier, a penetration accelerator, a surface tension modifier, an antifoaming agent, and the like. Other ink preparation agents include, for example, antiseptic / antifungal agents, pH adjusters, chelating reagents, rust inhibitors, UV absorbers, viscosity adjusters, dye solubilizers, surface tension adjusters, antifoaming agents, dispersants, And the like, and known additives. The content of the water-soluble organic solvent is 0 to 60% by mass, preferably 10 to 50% by mass with respect to the entire ink, and the ink preparation agent is 0 to 25% by mass, preferably 0 with respect to the entire ink. ˜20 mass%.

  Examples of water-soluble organic solvents that can be used in the light-shielding ink include C1-C4 alkanols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol, and N, N-dimethyl. Carboxamides such as formamide or N, N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexahydropyrimido-2- Heterocyclic ketones such as ON, ketones such as acetone, methyl ethyl ketone, 2-methyl-2-hydroxypentan-4-one, or cyclic ethers such as ketoalcohol, tetrahydrofuran, dioxane, ethylene glycol, 1,2- or 1,3 -Propylene glycol, 1, -Or (C2-C6) alkylene units such as 1,4-butylene glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, thiodiglycol, polyethylene glycol, polypropylene glycol, etc. Monomer, oligomer or polyalkylene glycol or thioglycol glycerin, polyol (triol) such as hexane-1,2,6-triol, ethylene glycol monomethyl ether or ethylene glycol monoethyl ether or ethylene glycol monobutyl ether, diethylene glycol monomethyl ether or diethylene glycol Monoethyl ether or diethylene glycol monobutyl ether or Polyhydric alcohol (C1 -C4) alkyl ethers such as triethylene glycol monomethyl ether or triethylene glycol monoethyl ether, gamma-butyrolactone or dimethyl sulfoxide.

  Examples of antiseptic / antifungal agents include organic sulfur, organic nitrogen sulfur, organic halogen, haloallylsulfone, iodopropargyl, N-haloalkylthio, nitrotyryl, pyridine, 8-oxyquinoline, Benzthiazole, isothiazoline, dithiol, pyridine oxyd, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiadiazine, anilide, adamantane, dithiocarpamate, brominated Indanone-based compounds, benzyl bromacetate-based compounds, inorganic salt-based compounds, and the like can be given. Examples of the organic halogen compound include sodium pentachlorophenol, examples of the pyridine oxido compound include sodium 2-pyridinethiol-1-oxide, and examples of the inorganic salt compound include anhydrous sodium acetate. Examples of the isothiazoline-based compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, and 5 -Chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, 2-methyl-4-isothiazoline-3-one calcium chloride, etc. Can be mentioned. Other antiseptic / antifungal agents include sodium sorbate sodium benzoate and the like (for example, Proxel GXL (5), Proxel XL-2 (5), etc., manufactured by Avecia).

  As the pH adjuster, any substance can be used as long as it can control the pH of the ink within the range of 6.0 to 11.0 for the purpose of improving the storage stability of the ink. For example, alkanolamines such as diethanolamine, triethanolamine, tris (hydroxymethyl) aminomethane, hydroxides of alkali metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium carbonate, sodium carbonate And alkali metal carbonates such as potassium carbonate.

  Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like. Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and tolyltriazole.

  Examples of the ultraviolet absorber include a compound that emits fluorescence by absorbing ultraviolet rays typified by a benzophenone compound, a benzotriazole compound, a cinnamic acid compound, a triazine compound, a stilbene compound, or a benzoxazole compound, so-called Optical brighteners can also be used.

  Examples of the viscosity modifier include water-soluble polymer compounds in addition to water-soluble organic solvents, and examples thereof include polyvinyl alcohol cellulose derivatives, polyamines, and polyimines.

  Examples of the dye solubilizer include urea, ε-caprolactam, ethylene carbonate, and the like.

  Examples of the surface tension adjusting agent include a surfactant, and examples thereof include an anionic surfactant, an amphoteric surfactant, a cationic surfactant, and a nonionic surfactant. Anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acyl amino acids and salts thereof, N-acyl methyl taurates, alkyl sulfates polyoxyalkyl ether sulfates Salt, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol type phosphate ester, alkyl type phosphate ester, alkyl allyl sulfone hydrochloride, diethyl sulfosuccinate, Examples include diethylhexylsylsulfosuccinate and dioctylsulfosuccinate. Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives. Amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine, and other imidazoline derivatives. Is mentioned. Nonionic surfactants include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene Ethers such as alkyl ethers, polyoxyallylalkyl alkyl ethers, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquis Esters such as oleate, polyoxyethylene monooleate, polyoxyethylene stearate, 2, 4, 7, -Acetylene glycol systems such as tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol, etc. For example, Nibushin Chemical's Serbuinol 104, 82, 465, Olfine STG, etc.) can be mentioned. These ink preparation agents are used alone or in combination. In addition, the surface tension of the light-shielding ink used in the present invention is usually 25 to 70 mN / m, more preferably 25 to 50 mN / m or less. The viscosity of the light-shielding ink is preferably 30 mPa · S or less, and more preferably 20 mPa · S or less.

  As the antifoaming agent, a fluorine-based or silicone-based compound can be used as necessary.

  In producing this light-shielding ink, there is no particular limitation on the order in which the respective drugs are dissolved. In preparing the light-shielding ink, the water to be used is preferably a substance with few impurities, such as ion exchange water or distilled water. Furthermore, if necessary, microfiltration using a membrane filter or the like may be performed to remove impurities. In addition, when used as an ink for an ink jet printer, it is preferable to perform microfiltration. The pore size of the filter for performing microfiltration is usually 1 to 0.1 microns, preferably 0.8 to 0.2 microns.

  In order to record an image pattern on the ink receiving layer using the light-shielding ink, a container containing the light-shielding ink is set at a predetermined position of the ink jet printer, and the ink receiving layer is formed by a normal method using the ink jet printer. Can be recorded. Examples of the ink jet printer include a piezo printer using mechanical vibration, and a bubble jet (registered trademark) printer using a pressure when bubbles are generated in ink by heating.

  This light-shielding ink does not precipitate or separate during storage. Therefore, when this light-shielding ink is used in an ink jet printer, the discharge port of the ink jet recording head is not blocked. The light-shielding ink used in the present invention does not cause a change in physical properties even under constant recirculation for a relatively long time by a continuous ink jet printer or intermittent use by an on-demand ink jet printer.

  Since this light-shielding ink has a wide and high absorption with respect to light in the wavelength region centered on 350 nm, it can shield exposure light used for the production of relief printing plates. Since the dye suitably used for the light-shielding ink has a high solubility in an aqueous solvent, the dye concentration can be increased, whereby a mask pattern having a high light-shielding ability can be formed on the ink receiving layer. In addition, since the pigment crystal is not deposited, the inkjet ejection path is not bent, and the discharge port is not clogged, so that a high-definition mask pattern can be formed using the inkjet system. .

  The composition for forming an ink receiving layer according to the invention includes at least two kinds of hydroxyalkyl celluloses having different mass average molecular weights. Therefore, hydroxyalkyl celluloses having different light-shielding ink holding ability are mixed, and an ink receiving layer capable of adjusting the ink bleeding property can be formed. As a result, the light-shielding ink can be uniformly held in the region where the light-shielding ink is desired to be retained, and a highly accurate pattern can be formed.

2. Letterpress printing original plate The letterpress printing original plate according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a relief printing original plate. As shown in FIG. 1, the relief printing original plate is a laminate having a base material 10, a photosensitive resin layer 20 formed on the base material 10, and an ink receiving layer 30 thereon. Further, although not shown, a cover sheet can be provided on the ink receiving layer, and an easy peeling layer can be provided between the ink receiving layer and the cover sheet, if necessary.

2-1. Substrate As the substrate 10 constituting the original plate for letterpress printing of the present invention, known materials used for ordinary letterpress printing plates satisfying physical performance such as mechanical strength required for printing conditions used as the letterpress printing plate. All substrates in metal plastic film, paper and their composite form can be used. These include polymeric films such as those formed by addition polymerization polymers and linear condensation polymers, transparent foams and fabrics, nonwovens such as glass fiber fabrics, and metals such as steel and aluminum. The substrate is preferably transparent to non-infrared rays so that back exposure is easy. More preferable base materials include polyethylene or polyester film, and polyethylene terephthalate film is particularly preferable. As the film, a film having a thickness of 50 μm to 300 μm, preferably a film having a thickness of 75 μm to 200 μm is used. This base material may be covered with a thin adhesion promoting layer between the photosensitive resin layer as required. As this adhesion promotion layer, for example, a layer made of a mixture of polycarbonate, phenoxy resin and polyvalent isocyanate is suitably used.

2-2. Photosensitive resin layer The photosensitive resin layer used in the present invention is a layer obtained by forming a film using a photosensitive resin composition and curing the film. As a photosensitive resin composition which can be used for this invention, a conventionally well-known thing can be used and it does not specifically limit. For example, the composition containing the following photosensitive resin, a photopolymerizable monomer, and a photoinitiator is mentioned.

(Photosensitive resin)
The photosensitive resin only needs to have a polymerizable unsaturated group that can be cross-linked by light irradiation. Specifically, a resin that crosslinks with a photopolymerizable monomer by a photopolymerization initiator described later is preferably used. It is done. As such a resin, an elastomer resin is preferably used.

  The elastomer resin is a single polymer, copolymer or a mixture thereof, which has an elastomeric property and is soluble, swelled or dispersed in an aqueous or organic solvent developer, and can be removed by washing. Is mentioned. Examples of these binders include polybutadiene, polyisoprene, polydiolefin, vinyl aromatic compound / diolefin copolymer and block copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer, diolefin / Acrylonitrile copolymer, ethylene / propylene copolymer, ethylene / propylene / diolefin copolymer, ethylene / acrylic acid copolymer, diolefin / acrylic acid copolymer, diolefin / acrylate / acrylic acid copolymer, Ethylene / (meth) acrylic acid / (meth) acrylate copolymer, polyamide, polyvinyl alcohol, polyvinyl alcohol / polyethylene glycol graft copolymer, amphoteric interpolymer, alkyl cellulose, hydroxyalkyl cellulose Celluloses such as nitrocellulose, ethylene / vinyl acetate copolymer, cellulose acetate butyrate, polybutyral, cyclic rubber, styrene / acrylic acid copolymer, polyvinyl pyrrolidone, polyvinyl pyrrolidone and vinyl acetate copolymer, chloroprene heavy Polymer, styrene-chloroprene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylonitrile-chloroprene copolymer, methyl methacrylate-butadiene copolymer, methyl methacrylate-isoprene copolymer, methacrylic acid Methyl-chloroprene copolymer, methyl acrylate-butadiene copolymer, methyl acrylate-isoprene copolymer, methyl acrylate-chloroprene copolymer, acrylonitrile-butazi -Styrene copolymer, acrylonitrile-isoprene-styrene copolymer, acrylonitrile-chloroprene-styrene copolymer, epichlorohydrin polymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-propylene oxide copolymer, epichlorohydrin rubber, chlorinated polyethylene , Vinyl chloride copolymer, vinylidene chloride copolymer, chlorinated polypropylene, chlorinated ethylene-propylene rubber, ethyl acrylate-acrylonitrile copolymer, terpene copolymer, butyl acrylate-acrylonitrile copolymer, methyl methacrylate -Acrylonitrile copolymer, butyl acrylate-styrene-acrylonitrile copolymer. The polymers may be used alone or in combination.

  As the elastomer resin, it is preferable to use a styrene / isoprene copolymer or a styrene / butadiene copolymer. By using such an elastomer resin, it is possible to ensure the transparency required for forming the exposure pattern and to further improve the resistance to the printing liquid (ink).

  The compounding amount of the elastomer resin is 10 to 99 parts by mass, preferably 30 to 90 parts by mass with respect to 100 parts by mass of the total composition for the photosensitive resin layer.

(Photopolymerizable monomer)
As the one or more types of monomers contained in the photosensitive resin layer, it is necessary to use a monomer having compatibility with the binder so that a transparent photosensitive resin layer without cloudiness can be formed.

  As the monomer, in addition to the monomer constituting the binder, for example, polybutadiene diacrylate, polybutadiene dimethacrylate, polyisoprene acrylate, polyisoprene methacrylate, α-methylstyrene, m-methylstyrene, p-methoxystyrene, etc. Aromatic vinyl monomers; α, β-ethylenically unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; carbons such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate Acrylates of alkyl alcohols of the number 1 to 23 and the corresponding methacrylates; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and other hydroxy Kill alcohol acrylates and corresponding methacrylates; alkoxyalkylene glycol acrylates and methacrylates such as methoxyethylene glycol and methoxypropylene glycol; monounsaturated polycarboxylic acids such as monoethyl maleate, monomethyl fumarate and monoethyl itaconate Monoesters: Diesters such as dimethyl maleate, diethyl maleate, dibutyl maleate, dioctyl maleate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, dioctyl itaconate Acrylamide such as acrylamide, methacrylamide, N, N′-methylenebisacrylamide, N, N′-hexamethylenebisacrylamide And corresponding methacrylamides; glycol diacrylates and corresponding methacrylates such as ethylene glycol diacrylate, polyalkylene glycol (2 to 23 alkylene glycol units); glycerin, pentaerythritol, trimethylolalkane, tetra Diacrylates, triacrylates, tetraacrylates, oligoacrylates and corresponding methacrylates of trihydric or higher polyhydric alcohols such as methylolalkanes (methane, ethane, propane as alkanes); 2-acryloyloxyethyl succinic acid, Light such as 2-acryloylethylhexahydrophthalic acid, acrylates with acidic functional groups such as 2-acryloyloxyethyl acid phosphate and the corresponding methacrylates; A polymerizable ethylenically unsaturated monomer is mentioned. One of these photopolymerizable ethylenically unsaturated monomers may be used alone, or two or more thereof may be used in combination.

  The monomer has a range of 5 to 30 parts by mass, preferably 10 to 20 parts by mass, when the total amount of the elastomer resin is 100 parts by mass. When the monomer content is less than the above range, the abrasion resistance and chemical resistance of the film after exposure curing are lowered, and when it exceeds the above range, the elastomeric property of the photosensitive resin layer is lowered, which is not preferable as a flexographic printing plate.

(Photopolymerization initiator)
As the photopolymerization initiator, generally known photopolymerization initiators can be used. Examples of such initiators include aromatic ketones such as benzophenone; benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, α-methylol benzoin methyl ether, α-methoxybenzoin methyl ether, 2,4-diethoxy Benzoin ethers such as phenylacetophenone; substituted and unsubstituted polynuclear quinones; 1-hydroxycyclohexyl phenyl ketone, 2,4-dimethoxy-1,2-diphenylethane-1-one, 2-methyl-1- [4- (Methylthio) phenyl] -morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-hydroxy-2-methyl-1-phenyl Propan-1-one, 2,4,6-tri Methylbenzoyldiphenylphosphine oxide, 1- (4- (2-hydroxyethoxy) phenyl) 2-hydroxy-2-methyl-1-propan-1-one, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4 -Dimethylthioxanthone, 3,3-dimethyl-4-methoxybenzophenone, benzophenone, 1-chloro-4-propoxythioxanthone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 4-benzoyl-4'-methyldimethylsulfide, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, 4-dimethylamino Ethyl benzoate buty 4-dimethylaminobenzoate 4-dimethylaminobenzoic acid-2-ethylhexyl, 4-dimethylaminobenzoic acid-2-isoamyl, 2,4'-diethoxyacetophenone, benzyldimethyl ketal, benzyl-β-methoxyethyl acetal, o-benzoylbenzoic acid Methyl, bis (4-dimethylaminophenyl) ketone, 4,4'-bisdiethylaminobenzophenone, 4,4'-dichlorobenzophenone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether , Benzoin isobutyl ether, p-dimethylaminoacetophenone, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, 2- (o-chlorophenyl) -4 5-diphenylimidazolyl dimer, thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, dibenzosuberone, α, α-dichloro-4-phenoxyacetophenone, benzyl-4-dimethylaminobenzoate, 9-phenylacridine, 1, Examples thereof include 7-bis- (9-acridinyl) heptane, 1,5-bis- (9-acridinyl) pentane, 1,3-bis- (9-acridinyl) propane and the like.

  Furthermore, the photosensitive resin composition of the present invention may be added with dyes, pigments, polymerization inhibitors, antioxidants, photodegradation inhibitors, and the like, if necessary, to improve its performance.

(Other ingredients)
Furthermore, additives such as a sensitizer, a thermal polymerization inhibitor, a plasticizer, and a color former can be used in the photosensitive resin composition for forming the photosensitive resin layer, depending on the required properties. Various methods can be used as a method for preparing the photosensitive resin composition. For example, the raw materials to be blended are mixed with an appropriate solvent, for example, halogenated hydrocarbons such as chloroform and tetrachloroethylene, dibutyl ether, isopropyl ether and dioxane. , Ethers such as tetrahydrofuran, acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, cyclohexanone and other ketones, ethyl acetate, n-propyl acetate, n-butyl acetate esters, benzene, toluene, xylene Aromatic hydrocarbons, etc. (solvents such as these organic solvents can be used alone or mixed) are dissolved and mixed, and cast into a mold to evaporate the solvent. Also, there is a kneader without using a solvent The kneaded by a roll mill, an extruder, injection molding machine, it can be formed into a plate having a desired thickness by a press.

  As another aspect of the photosensitive resin composition, a hydrophilic polymer can be used instead of the elastomeric resin described above.

  As such a hydrophilic polymer, for example, a reaction product of an acrylic compound having an N-methylol group and polyvinyl alcohol, a modified polyvinyl alcohol (polyvinyl alcohol / polyacrylate block copolymer, acrylic anhydride was reacted). Modified polyvinyl alcohol, grafted polyvinyl alcohol, etc.), carboxyalkyl cellulose, polyamide having sodium sulfonate group, polyamide having ether bond, polyamide having basic nitrogen or ammonium salt nitrogen, or a mixture thereof.

  Examples of the acrylic compound having an N-methylol group include N-methylol acrylamide, N-methylol methacrylamide, N-methyl-N-methylol acrylamide, N-methyl-N-methylol methacrylamide, N-ethyl-N. -Methylol acrylamide, N-ethyl-N-methylol methacrylamide are mentioned, These are used individually by 1 type or in combination of multiple types.

2-3. Ink Receiving Layer The ink receiving layer 30 used in the present invention is a layer formed using the above-described ink receiving layer forming composition. The ink receiving layer 30 is a coating layer that functions by being directly laminated on the photosensitive resin layer 20. Therefore, it is necessary to comprise from the component which does not have compatibility or reactivity with the photosensitive resin layer 20. Further, as a characteristic of the ink receiving layer 30, the printing ink that forms a light shielding pattern according to the image pattern is held, and oxygen transmission is suppressed so that oxygen does not unnecessarily act on the photosensitive resin layer 20. It has at least two characteristics.

  The ink receiving layer can be formed by heat melting when using an ink receiving layer forming composition that does not contain an organic solvent. Moreover, when using the composition for ink-receiving layer formation containing an organic solvent, it can apply | coat on the photosensitive resin layer, and can form by removing (drying) the organic solvent. Alternatively, the photosensitive resin layer and the ink receiving layer may be formed on separate films (supports) and then bonded together. Details of the formation of the ink receiving layer will be described later.

  The thickness of the ink receiving layer 30 is not particularly limited, but is preferably 70 μm or less as an upper limit in order to prevent curling. The lower limit of the thickness is preferably 5 μm or more in order to prevent ink bleeding, particularly water-based ink bleeding.

  The ink receiving layer may contain a resin other than hydroxyalkyl cellulose as long as the above-described performance is not impaired. Such resins include polyvinyl butyral resin, polyester resin (excluding those modified with acrylic), epoxy resin, vinylidene chloride resin, vinyl chloride-acrylic copolymer resin, vinyl chloride-vinyl acetate copolymer resin, chlorine Polyolefin resin, urethane resin, alkyd resin, rubber resin and the like. However, the total amount of hydroxyalkyl cellulose is preferably 80% by mass or more, more preferably 90% by mass or more, based on the total resin components in the ink receiving layer.

  The ink receiving layer may contain a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerin or sorbitol. By including a polyhydric alcohol in the ink receiving layer, the followability to the flexographic printing plate can be improved without impairing the recording characteristics of the water-based ink. The content of the polyhydric alcohol is preferably 40 parts by mass or less, and more preferably 5 to 25 parts by mass with respect to 100 parts by mass of the hydroxyalkyl cellulose in the ink receiving layer.

The oxygen permeation coefficient of the ink receiving layer in the present invention is not particularly limited as long as the pattern profile of the photosensitive resin layer is not deteriorated by oxygen. A preferable range of such an oxygen transmission coefficient is 1 × 10 ^{−17 to} 9 × 10 ⁻⁵ (cm ³ · cm / cm ² · sec · cmHg). The oxygen transmission coefficient may be lowered to the extent that oxygen transmission is almost blocked, but by controlling the oxygen transmission coefficient to allow a small amount of oxygen transmission, the pattern profile of the photosensitive resin layer by exposure and development is controlled. It is also possible to do. For example, if it is set within the range of 1 × 10 ⁻¹⁴ × 9 × 10 ⁻¹⁰ (cm ³ · cm / cm ² · sec · cmHg), a small amount of oxygen is present on the surface of the photosensitive resin layer during exposure of the photosensitive resin layer. Will be present. As a result, the pattern profile of the photosensitive resin layer after exposure and development becomes a tapered taper at the end, and the pattern tip that becomes a printing dot becomes thin. As a result, the printing surface (ink-attached portion) at the front end of the pattern is reduced in area, and the sharpness of printing can be improved.

2-4. Others Further, in the relief printing original plate of the present invention, a cover sheet can be laminated on the ink receiving layer 30 as a protective layer, if necessary. Moreover, an easily peelable layer can be provided between the ink receiving layer and the cover sheet.

  As the cover sheet, any known cover sheet of metal, plastic film, paper, and a composite form thereof, which are used for ordinary relief printing plates, can be used. These include polymeric films such as those formed by addition polymerization polymers and linear condensation polymers, transparent foams and fabrics, nonwovens such as glass fiber nonwovens, and metals such as steel and aluminum. Preferably, a polyethylene film, a polyester film, a polypropylene film, or a laminate of these films is used. As this cover sheet, a film is suitable, and the thickness is preferably 20 μm or more and 200 μm or less.

  Further, by using the ink receiving layer according to the present invention, the peelability when the cover sheet is peeled from the ink receiving layer can be adjusted.

  Further, when the cover sheet provided on the ink receiving layer is peeled off, an easily peelable layer can be provided between the ink receiving layer and the cover sheet in order to prevent the surface of the ink receiving layer from being damaged. . As a material used for the easily peelable layer, a material which is not affected by light in the wavelength region of the exposure wavelength and is transparent and has no adhesiveness can be used. For example, polyamide, polyvinyl alcohol, aminoalkyd, silicone release agent, and combinations thereof can be mentioned.

  The relief printing original plate according to the present invention includes an ink receiving layer formed using the above-described ink receiving layer forming composition. Since the ink repellency of the ink receiving layer is controlled, a light-shielding ink pattern can be accurately formed on the ink receiving layer. In particular, in the case of a relief printing original plate, it is necessary to form a highly accurate pattern on the photosensitive resin layer and to maintain the ink uniformly so as to be surely shielded from light. Therefore, the ink receiving layer needs to have a certain degree of bleeding in order to use the ink efficiently, and to have a certain degree of bleeding in order to ensure pattern accuracy. According to the present invention, since the ink receiving layer capable of adjusting the bleeding property according to the type of ink is provided, it is possible to provide a relief printing original plate capable of forming a highly accurate pattern.

3. 2. Manufacturing method of relief printing original plate and manufacturing method of relief printing plate Next, the manufacturing method of the relief printing original plate and the manufacturing method of the relief printing plate according to the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view for explaining a manufacturing process of a relief printing plate according to the present invention. In the following description, a method for producing a relief printing original plate will be described, and then a method for producing a relief printing plate using the produced relief printing original plate will be described.

3-1. Photosensitive resin layer forming step First, a photosensitive resin composition prepared by mixing a photosensitive resin, a photopolymerizable monomer, a photopolymerization initiator, and other components is formed into a hot melt, and this has a desired thickness. Make a calendar. By placing this photosensitive resin composition on the base material 10 and heating, the photosensitive resin layer 20 is formed on the base material 10 as shown in FIG. As another method, the photosensitive resin layer is extruded between a base material and a temporary cover sheet after melting, mixing, degassing and filtering the photosensitive resin composition using an extruder, A photosensitive resin is formed on the substrate by calendering to a desired thickness, or by placing a substrate and a cover sheet in a mold and injecting a photosensitive resin composition between them. Layers can also be formed.

3-2. Step of forming ink receiving layer Next, the above-described composition for forming an ink receiving layer is prepared. Preparation of the ink receiving layer forming composition is as follows. Prepare a solution obtained by dissolving hydroxyalkyl celluloses having different mass average molecular weights described in the above section in a solvent, and mix these solutions with each other, or solid form hydroxyalkyl cellulose as a solid (powder). For example, it can be performed by various methods such as mixing by mechanical stirring such as a planetary mixer.

When the ink receiving layer forming composition is in a solid form or when the viscosity is high enough to withstand the coating treatment, the ink receiving layer forming composition is provided on the photosensitive resin layer 20, and thereafter The ink receiving layer 30 (see FIG. 2B) can be manufactured by thermally melting the alkyl cellulose. As long as the hydroxyalkyl cellulose can be melted in this heat melting, there is no limitation on the treatment method, but for example, it can be performed by applying heat at a temperature of 150 ° C. to 180 ° C. Moreover, you may press (press), applying heat at the time of heat melting. When ^pressed, it is preferable to press under the conditions of ^{10kg / cm 2 ~20kg / cm 2} .

  On the other hand, a method for producing an ink receiving layer when the ink receiving layer forming composition is a liquid composition will be described. In this case, as shown in FIG. 2B, the ink receiving layer forming composition is directly applied on the photosensitive resin layer 20 and then dried to form the ink receiving layer 30. Thereby, a relief printing original plate can be formed.

  As another method, an ink receiving layer forming composition is applied on a cover sheet and dried to form an ink receiving layer, and this ink receiving layer is pressure-bonded onto the photosensitive resin layer.

  And it can also manufacture by laminating | stacking with the photosensitive resin layer formed on the base material with a heat | fever and / or a pressure except for the temporary cover sheet | seat on the pressure-bonded ink receiving layer. Further, a relief printing original plate can also be produced by sequentially laminating an ink receiving layer, a photosensitive resin layer, and a substrate on a cover sheet.

3-3. Mask image layer formation process (pattern formation process)
Next, as shown in FIG. 2 (c), the ink receiving layer 30 of the relief printing original plate obtained by the above manufacturing method is used in the ink receiving layer 30 by using a light-shielding ink 40 and an ink jet printer (not shown). The light shielding ink 40 is permeated to form an ink permeation area 32 and a light shielding pattern is recorded. The light shielding pattern by the light shielding ink is formed in the layer as the light shielding ink 40 penetrates into the ink receiving layer 30. As a result, the ink receiving layer 30 becomes a mask image layer.

  As a printing apparatus that can be suitably used in the method for producing a relief printing plate of the present invention, an ink jet printer can be suitably used. Printing by an ink jet printer ejects ink from a nozzle onto a recording material such as paper to form characters and images. This printing method is mainly a piezo method in which ink is ejected by applying mechanical vibration to the ink using a piezoelectric element, or ink is ejected by using pressure generated by heating and firing the ink. It can be divided roughly into the method of making it.

3-4. Exposure process (irradiation process)
Next, as shown in FIG. 2 (d), light having a wavelength region of 300 nm to 700 nm is irradiated on the relief printing original plate in which the mask image layer is formed on the photosensitive resin layer 20 (illustrated by arrows). To do. Thereby, the exposure film | membrane which has the irradiation area | region 22 and the non-irradiation area | region 24 in the photosensitive resin layer 20 can be obtained.

  Since the photosensitive resin layer 20 is sensitive to exposure, the light is shielded by the light shielding pattern and is not irradiated and is not irradiated with the non-irradiated region 24 and the irradiated region 22 sensitive to light and cured. Causes a difference in solubility in the developer. For this reason, the photosensitive resin layer located in the non-irradiation region 24 is dissolved and removed by the next development process.

The light applied to the photosensitive resin layer 20 is an electromagnetic wave having a wavelength shorter than that of infrared rays, preferably an electromagnetic wave of visible light and an ultraviolet region, more preferably an electromagnetic wave of 300 nm to 700 nm, and more preferably an electromagnetic wave of 300 nm to 400 nm. is there. Examples of the light source for the irradiation light include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a deuterium lamp, a tungsten lamp (tungsten iodine lamp, WI lamp, WI ₂ lamp), a xenon lamp, and an excimer laser. be able to.

  The exposure conditions in the exposure process of the present invention are not particularly limited. Depending on the method used for exposure, it is possible to appropriately select the exposure time, exposure intensity, and the like.

3-5. Development process (resin layer forming process)
Next, as shown in FIG. 2E, the photosensitive resin layer located in the non-irradiated region 24 of the exposure film is dissolved and removed with a developer to form an image on the relief printing original plate. Thereby, the pattern of the relief printing plate is formed.

  The developer used in the development process may be either an organic solution or an aqueous solution as long as it has the property of dissolving the photosensitive resin layer. The choice of the developer depends on the chemistry of the resin to be removed. Depends on specific properties. Suitable organic solvent developers include aromatic or aliphatic hydrocarbons and aliphatic or aromatic halohydrocarbon solvents, or mixtures of these solvents with suitable alcohols. Further, the developer composed of an aqueous solution contains water or an organic solvent miscible with water and an alkaline material. Examples of the developer include water, esters such as heptyl acetate and 3-methoxybutyl acetate, petroleum fractions, hydrocarbons such as toluene and decalin, chlorine-based solvents such as tetrachloroethylene, and monoethanolamine. And aqueous solutions of amines such as diethanolamine and triethanolamine, sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia and the like. Moreover, it is also possible to use what mixed alcohols, such as propanol, butanol, and pentanol, with these solvents, and washing-out can employ | adopt arbitrary methods, such as immersion, injection from a nozzle, and brushing with a brush. it can.

  Then, a relief printing plate is manufactured by hardening the remaining pattern.

  According to the method for producing a relief printing plate according to the present invention, a light-shielding ink is ejected to an ink receiving layer whose bleeding property is controlled according to the type of ink to form a relief printing plate pattern. Therefore, it is possible to form a pattern with high accuracy without generating an erroneously cured portion that is not desired to be cured, and a relief printing plate having a desired pattern can be manufactured.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, a following example is only the illustration for demonstrating this invention suitably, and does not limit this invention at all. In the following description, “part” and “%” are based on mass unless otherwise specified. The absorbance was measured using a spectrophotometer (D-2000 (trade name), manufactured by Hitachi, Ltd.).

[Examples 1 to 3]
(Formation of ink receiving layer)
HPC-L (hydroxypropylcellulose, mass average molecular weight 125000; manufactured by Nippon Soda Co., Ltd.) was dissolved in methyl ethyl ketone so as to have a solid content concentration of 5%, and an ink receiving layer forming composition (A) (hereinafter referred to as “composition”). Product (A) "). Further, HPC-M (hydroxypropylcellulose, mass average molecular weight 692000; manufactured by Nippon Soda Co., Ltd.) was dissolved in methyl ethyl ketone so as to have a solid content concentration of 5%, and an ink receiving layer forming composition (B) "Composition (B)") was obtained. On a polyethylene terephthalate film (hereinafter referred to as “D layer”) to be a cover sheet having a thickness of 100 μm, the compositions (A) and (B) were mixed in the proportions shown in Table 1, and then the mixed solution was used. Then, it was applied using a bar coater so that the film thickness after drying was 3 μm. The obtained coating film was dried at 100 ° C. for 5 minutes to form an ink receiving layer (hereinafter referred to as “C layer”). The absorbance at 370 nm of this ink receiving layer and D layer was measured and found to be 0.0 (total transmission).

(Formation of photosensitive resin layer)
On the other hand, 100 parts by mass of a styrene-butadiene copolymer having a mass average molecular weight of 240,000 (trade name: D-1155, manufactured by JSR Shell Elastomer Co., Ltd.), liquid 1,2-polybutadiene having a mass average molecular weight of 1,000 (trade name: (Nisso-PB-1000, manufactured by Nippon Soda Co., Ltd.) 70 parts by mass, 10 parts by mass of trimethylolpropane triacrylate, 3 parts by mass of methoxyphenylacetophenone, 0.05 part by mass of 2,6-di-tert-butyl-4-hydroxytoluene In addition, 0.002 part by mass of Oil Blue # 503 (manufactured by Orient Chemical Co., Ltd.) was dissolved in a solvent composed of 0.2 part by mass of tetrahydrofuran to prepare a photosensitive resin composition. The obtained preparation was pressed into an extruder with a high viscosity pump and kneaded in the extruder while being pushed into a polyethylene terephthalate film (hereinafter referred to as “A layer”) to a thickness of 2.84 mm. A photosensitive resin layer (hereinafter referred to as “B layer”) was formed.

(Formation of letterpress printing original plate)
The laminate having the ink receiving layer formed thereon and the laminate having the photosensitive resin layer formed thereon are bonded so that the B layer and the C layer face each other, laminated using a pressure roller, and letterpress printing An original plate was manufactured.

[Examples 4 to 6]
HPC-L and HPC-M used in Examples 1 to 3 were prepared. In Example 4, the mass ratio (HPC-L: HPC-M) was 66:34, and in Example 5, the mass ratio was 80: In Example 6, the mixture was mixed so that the mass ratio was 90:10, and the mixture was stirred and homogenized using a planetary mixer to obtain a composition for forming an ink receiving layer. Then, the composition for forming an ink receiving layer according to Examples 4 to 6 was placed on a polyethylene terephthalate film (hereinafter referred to as “D layer”) serving as a cover sheet having a thickness of 100 μm, and 200 ° C., 20 kg / cm. ^{In step 2} , pressing was performed for 5 minutes so that the film thickness of the ink receiving layer after formation was 3 μm. The absorbance at 370 nm of the ink receiving layer and D layer thus obtained was measured and found to be 0.0 (total transmission).

  Next, in the same manner as in Examples 1 to 3, a photosensitive resin layer was formed, and these were laminated to produce a relief printing original plate.

[Comparative Examples 1 and 2]
In Comparative Examples 1 and 2, a relief printing original plate according to the Comparative Example was formed in the same manner as in Examples 1 to 3, except that the mixing ratio of the composition (A) and the composition (B) was different. The mixing ratio in Comparative Examples 1 and 2 is also shown in Table 1.

(Evaluation 1)
The D layer of the relief printing original plate according to Examples 1 to 6 and Comparative Examples 1 and 2 was peeled off, and a TOKTED ink (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used for the C layer using a flatbed inkjet printer manufactured by Roland DG. Printed selectively on top. The evaluation results are shown in Table 2.

(Evaluation 2)
Subsequently, when the absorbance at 370 nm of the obtained printed part was measured, it was 3.0. Next, back exposure was performed by irradiating ultraviolet light having a center wavelength of 370 nm at 75 mJ / cm ² from the A layer side. Subsequently, main exposure was performed by irradiation from the image layer side at 2500 mJ / cm ² . Development was performed at a liquid temperature of 25 ° C. for 4 minutes using an aromatic hydrocarbon developer (trade name FDO-S2, manufactured by Tokyo Ohka Kogyo Co., Ltd.) as a developer. No redeposition of development residue or the like was observed on the obtained plate surface. After development, after drying at 55 ° C. for 50 minutes, post-treatment is performed using an ultraviolet fluorescent lamp having a central wavelength at 250 nm, and further, ultraviolet light having a central wavelength at 370 nm is irradiated at 3000 mJ / cm ² for post-exposure. The letterpress printing plate was obtained. The state of the obtained relief printing plate was evaluated. The evaluation results are shown in Table 2.

(Evaluation 3)
The state of the relief printing plate was evaluated in the same manner as in Evaluation 2 except that the ink used in Evaluations 1 and 2 was changed to Photo Black Ink ICBK24 (manufactured by EPSON). The evaluation results are shown in Table 2.

(Evaluation 4)
Table 2 shows the peelability of the cover sheet of the relief printing original plates according to Examples 1 to 6 and Comparative Examples 1 and 2. In the peeling test, the cover sheet was peeled from the ink receiving layer by hand.

In Table 2, each symbol indicates the following evaluation result.
Evaluation 1 ○: The blur adjustment was good.
Δ: Some streaks occur, but the adjustment of the bleeding property is at a practical level.
X: Evaluations 2 and 3 in which poor adjustment of bleeding property occurred ○: The light shielding property of the ink is good and there is no erroneously exposed portion.
Δ: Some mis-exposed areas are generated but at a practical level.
×: Ink concealment was poor, mis-exposed part was generated, or ink was excessively blotted and pattern formation could not be evaluated 4 ○: Good peelability and good handling properties
Δ: Slightly poor peelability but good handling at practical level
X: The peelability was too strong and could not be peeled, or the peelability was too weak and the handling property was poor.

  As is clear from Table 2, it was confirmed that the letterpress printing original plate according to the present example is useful because it has good ink bleeding, light shielding properties, and adjustment of the peelability of the cover sheet as a protective layer. It was.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  The relief printing plate obtained by the production method of the present invention can be used for, for example, cardboard printing, flexible packaging printing, label / seal printing, letter press, display, and printing plate for electronic materials.

It is sectional drawing which shows the relief printing plate board | substrate which concerns on embodiment of this invention. It is sectional drawing explaining the manufacturing process of the relief printing plate which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Base material 20 Photosensitive resin layer 22 Irradiation area 24 Non-irradiation area 30 Ink receiving layer 32 Ink penetration area 40 Light-shielding ink

Claims (11)

A letterpress printing original plate containing a photosensitive resin layer and an ink receiving layer provided on the photosensitive resin layer,
The original plate for letterpress printing, wherein the ink receiving layer contains at least two hydroxyalkyl celluloses having different mass average molecular weights.   2. The relief printing original plate according to claim 1, wherein a protective layer is formed on the ink receiving layer.   3. The relief printing original plate according to claim 1, wherein the alkyl group of the hydroxyalkyl cellulose is a linear or branched alkyl group having 1 to 6 carbon atoms.   4. The relief printing original plate according to claim 3, wherein the hydroxyalkylcellulose is hydroxypropylcellulose, hydroxyethylcellulose, or hydroxypropylmethylcellulose. The range of the weight average molecular weight of the hydroxyalkyl cellulose is
(A) 1 × 10 ^{4 to} 3 × 10 ⁵
(B) 4x10 < ⁵ > -1x10 < ⁶ >, The relief printing original plate of any one of Claim 1 thru | or 4 characterized by the above-mentioned.   6. The relief printing original plate according to claim 5, wherein a mass ratio of (A) to (B) is (A) :( B) = 55: 45 to 95: 5. A pattern forming step of forming a light-shielding pattern on the ink receiving layer of the relief printing original plate according to any one of claims 1 to 6, using a light-shielding ink that blocks an exposure wavelength;
An irradiation step of irradiating the photosensitive resin layer with light in the wavelength region of the exposure wavelength, using the light shielding pattern as a mask, and
A resin layer forming step of forming a resin layer having a convex pattern for printing by removing a non-irradiated region of the photosensitive resin layer in an uncured state without being exposed to light in the wavelength region of the exposure wavelength, A method for producing a relief printing plate, comprising:   The method for producing a relief printing plate according to claim 7, wherein a light-shielding ink having an absorptivity at 300 nm to 450 nm is used as the light-shielding ink.   A composition for forming an ink receiving layer, comprising at least two hydroxyalkyl celluloses having different mass average molecular weights.   The composition for forming an ink receiving layer according to claim 9, comprising an organic solvent. A method for producing a relief printing original plate,
A method for producing a relief printing original plate, comprising forming an ink receiving layer on a photosensitive resin layer by heat melting.

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