JP2015003440A - Platemaking method of photosensitive lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a platemaking method of a photosensitive lithographic printing plate capable of improving edge fouling caused by adhesion of ink onto the end of a printing plate, when performing lithographic printing on a wider paper than the width of the printing plate.SOLUTION: In a platemaking method of a photosensitive lithographic printing plate having a photosensitive layer on an aluminum support, for manufacturing a printing plate for performing lithographic printing on a wider paper than the width of the printing plate by using neutral dampening water, after exposing the aluminum support surface by exposing and developing the photosensitive lithographic printing plate, a plate surface protection agent containing at least malonic acid and/or citric acid is imparted onto the aluminum support surface.

Description

  The present invention relates to a method for making a photosensitive lithographic printing plate. More specifically, the present invention relates to a plate making method of a photosensitive lithographic printing plate that can improve edge stains that occur when lithographic printing is performed on paper having a width wider than that of the printing plate.

  Lithographic printing uses the oleophilic pattern formed on the plate surface and the hydrophilic surface properties of the non-image area. When ink and dampening water are supplied simultaneously on the plate surface, the ink is placed on the pattern having an oleophilic surface. It utilizes the selective transfer. The ink transferred onto the pattern is then transferred to an intermediate called a blanket, and printing is performed by transferring the ink from the intermediate to a printing paper.

  When printing on paper that is narrower than the width of the printing plate as in a normal sheet-fed printing press, this is not a problem because the edge of the printing plate does not become the printing surface. However, when printing on wide paper, the edge of the printing plate also becomes the printing surface, so the ink adhering to the edge is transferred to the printing surface and becomes dirty (edge contamination), which impairs the commercial value of the printed matter. There was a case.

  As a method for preventing such edge contamination, for example, Japanese Patent Publication No. 57-46754 discloses a method of scraping off the corners of the end of an aluminum support with a file or a knife, and Japanese Patent Laid-Open No. 9-52466. A lithographic printing plate is disclosed in which a corner formed by a surface having a hydrophilic layer of an aluminum support and an end face of the aluminum support is formed by a convex curved surface. Japanese Examined Patent Publication No. 62-61946 discloses a method of applying a desensitizing solution to the end face of the end portion, and Japanese Patent Application Laid-Open No. 2001-92153 (Patent Document 1) discloses an emulsion type plate containing soybean polysaccharides. JP-A-2005-262878 (Patent Document 2) discloses a protective agent containing a specific anionic surfactant.

  On the other hand, the fountain solution used in lithographic printing is generally a surface conditioner mainly composed of phosphoric acid, a pH adjusting agent (buffer) such as phosphate and nitrate, and a hydrophilic polymer compound such as gum arabic. It mainly comprises a non-image area protective agent, alcohols such as isopropyl alcohol, surface tension reducing agents such as surfactants, and other preservatives such as organic amines and organic halogens. The fountain solution thus constructed is usually in the acidic or alkaline region, but the acidic or alkaline fountain solution can cause skin irritation when it comes into contact with the human body during handling such as during printing operations. There is. Furthermore, the waste liquid must be treated to a level that meets the effluent standards by neutralizing with alkali or acid.

  As dampening water that can solve the above-mentioned problems, for example, as disclosed in JP-A No. 2004-106531, JP-A No. 2005-028853, JP-A No. 2010-120302, etc., the pH is 5-9 Neutral fountain solution in the area is known. However, when lithographic printing is performed on paper having a width wider than that of the printing plate using a neutral fountain solution, the above-mentioned edge stains tend to occur particularly easily, and it is extremely difficult to improve this. There was a need for improvement.

JP 2001-92153 A JP 2005-262878 A

  The present invention is a photosensitizer capable of improving edge smearing caused by ink adhering to the edge of a printing plate when lithographic printing is performed on a paper having a width wider than that of the printing plate using a neutral dampening solution. An object of the present invention is to provide a method for making a lithographic printing plate.

The above object of the present invention has been achieved by the following invention.
A method for making a photosensitive lithographic printing plate having a photosensitive layer on an aluminum support for producing a printing plate for lithographic printing on paper wider than the printing plate width using a neutral fountain solution. The photosensitive lithographic printing plate is exposed and developed to expose the surface of the aluminum support, and then the surface of the aluminum support is provided with a plate surface protective agent containing at least malonic acid and / or citric acid. Plate making method.

  According to the present invention, there is provided a method for making a photosensitive lithographic printing plate capable of improving edge stains generated when lithographic printing is performed on paper having a width wider than that of the printing plate using a neutral fountain solution. be able to.

  The present invention is described in detail below. The photosensitive lithographic printing plate used in the plate making method of the present invention has a photosensitive layer on an aluminum support.

  The aluminum support of the photosensitive lithographic printing plate is a pure aluminum plate or an alloy plate containing aluminum as a main component and a trace amount of foreign elements. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is preferably 10% by mass or less. The thickness of the aluminum support is about 0.1 to 0.6 mm. This thickness can be changed as appropriate according to the size of the printing press, the size of the printing plate, and the desire of the user.

  A more preferred aluminum support is a roughened aluminum support having an anodized film. Here, the roughened aluminum support having an anodized film includes an aluminum support generally used for a lithographic printing plate. The aluminum support generally used for lithographic printing plates has a roughened surface to improve wettability (water retention) against dampening water during printing and to improve adhesion to the photosensitive layer. Is done. This roughening treatment (so-called graining) is performed by mechanically roughening treatment such as ball graining, wire graining or brush graining, or by chemically dissolving aluminum with chloride, fluoride or the like. A chemical surface roughening treatment, an electrolytic surface roughening treatment performed by electrochemically dissolving aluminum, and a surface roughening method using these methods in combination are known. For example, JP-A-48-28123, JP-A-53-123204, JP-A-54-146234, JP-A-55-25381, JP-A-55-132294, JP-A-56. -55291, JP-A-56-150593, JP-A-56-28893, JP-A-58-167196, US Pat. No. 2,344,510, US Pat. No. 3,861. No. 9,917, U.S. Pat. No. 4,301,229, and the like. As for the surface shape of the aluminum support, U.S. Pat. No. 2,344,510 discloses a grained structure in which mechanical roughening and electrolytic roughening are performed in a superimposed manner, U.S. Pat. No. 4,301,229. Is the cumulative frequency distribution of the pit diameter and the centerline average roughness, US Pat. No. 3,861,917 is the depth of the rough surface, and Canadian Patent 955449 is the height of the crest of the rough surface. The diameter, West German Patent 1,813,443 describes the level difference of the rough surface. After such roughening treatment, anodization treatment is performed in an electrolytic solution such as sulfuric acid, phosphoric acid, nitric acid or a mixture thereof.

The conditions for the anodizing treatment vary depending on the electrolyte used, and thus cannot be determined unconditionally. 5 to 60 A / dm ² , voltage 1 to 100 V, and electrolysis time 10 to 200 seconds are appropriate.

Is preferably an amount of the anodized film is 1 to 10 g / ^{m 2,} more preferably from 1.5~7g / ^{m 2,} particularly preferably from 2-5 g / ^{m 2.} An alkali etching treatment can be performed after the roughening treatment and before the anodizing treatment.

  Further, in the present invention, after the anodizing treatment, the aluminum support may be hydrophilized. Examples of the hydrophilic treatment liquid include an aqueous solution containing an alkali metal silicate, an aqueous solution containing a metal fluoride and a phosphate, and an aqueous solution containing polyvinylphosphonic acid. Further, as a hydrophilic treatment method, a method of immersing an aluminum plate in a treatment liquid, a method of supplying the treatment liquid to an aluminum plate by a shower, or an aluminum plate using a gravure roll, an extrusion bar or the like There is a method of applying to the surface.

  The photosensitive lithographic printing plate used in the plate making method of the present invention has a photosensitive layer on the above aluminum support. As the photosensitive layer, either a negative type or a positive type photosensitive layer can be used. However, when lithographic printing is performed on paper having a width wider than that of the printing plate, the end portion of the printing plate is also formed on the printing surface. Therefore, when a positive photosensitive layer is used, it is necessary to remove the photosensitive layer at the periphery of the printing plate by so-called burning. When a negative photosensitive layer is used, it is not necessary to burn out (because the peripheral photosensitive layer can be easily removed by development). Therefore, the lithographic printing plate of the present invention has a negative photosensitive layer. A photosensitive layer of the type is preferably used.

  In the present invention, the negative photosensitive layer is preferably a photosensitive layer containing a compound having a polymerizable double bond group. The compound having a polymerizable double bond group can be used by mixing one or more compounds selected from a polymer group and a low molecular compound group.

  The polymer compound having a polymerizable double bond group is a polymer compound formed by an arbitrary repeating unit, and is a polymer compound in which a polymerizable double bond group is bonded to a side chain through an arbitrary linking group. is there. Among them, a polymer compound having a vinyl group as a polymerizable double bond group is preferably used, and a polymer compound in which a phenyl group substituted with a vinyl group is bonded to the main chain directly or via an arbitrary linking group is particularly preferably used. It is done. In addition, it is preferable to introduce a carboxyl group, a sulfo group, a quaternary ammonium group, or the like that is connected to the main chain via an arbitrary connecting group. The carboxyl group or sulfo group may form a salt (for example, sodium salt, potassium salt, lithium salt, ammonium salt, etc.). These linking groups are not particularly limited, and include any group, atom, or a combination thereof.

  In the phenyl group substituted by the vinyl group, the phenyl group may be substituted, and the vinyl group is a halogen atom, carboxyl group, sulfo group, nitro group, cyano group, amide group, amino group, alkyl group. , An aryl group, an alkoxy group, an aryloxy group and the like may be substituted.

  For example, JP-A-2002-278066, JP-A-2002-287340, JP-A-2003-215801 and the like are described in detail regarding polymer compounds having a phenyl group substituted with a vinyl group as a polymerizable double bond group. It can be used in the present invention. Although the specific example is shown below, it is not limited to these.

  The polymer compound having a polymerizable double bond group preferably has a weight average molecular weight in the range of 1,000 to 1,000,000, more preferably in the range of 50,000 to 600,000. In the present invention, the polymer compound having a polymerizable double bond group may be used alone or in combination of two or more kinds.

  Next, the low molecular weight compound having a polymerizable double bond group preferably used in the present invention will be described. The low molecular compound having a polymerizable double bond group in this case can be preferably used as long as it is a compound that undergoes polymerization by radicals generated by photolysis of a photopolymerization initiator. Furthermore, when a low molecular weight compound having two or more polymerizable double bond groups in the molecule is used, a crosslinked product is generated as a result of polymerization by radicals. Therefore, a negative photosensitive lithographic printing plate When the material is constituted, it forms a cross-linked hard image portion film, so that it can be used very preferably to give a printing plate having excellent printing durability and ink transferability. Examples of low molecular weight compounds having a polymerizable double bond group that can be used for such purposes include 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and tetraethylene glycol. Polyfunctional acrylic monomers such as diacrylate, trisacryloyloxyethyl isocyanurate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and the like, or an acryloyl group, Polyester (meth) acrylate, epoxy (meth) acrylate, and the like are similarly used as various oligomers into which a methacryloyl group is introduced. It is also possible to use a compound having both a polymerizable double bond and a urethane bond. Specific examples of the compound having both a polymerizable double bond and a urethane bond are shown below.

  In the low molecular compound having a polymerizable double bond group, it is also preferable to use a low molecular compound having a phenyl group substituted with a vinyl group as the polymerizable double bond group. Although the specific example is shown below, it is not limited to these.

  Examples of other elements contained in the photosensitive layer used in the present invention include a photopolymerization initiator. Conventionally known compounds can be used as the photopolymerization initiator. For example, trihaloalkyl-substituted compounds (for example, s-triazine compounds and oxadiazole derivatives as trihaloalkyl-substituted nitrogen-containing heterocyclic compounds, trihaloalkylsulfonyl compounds), organic boron salts, hexaarylbiimidazoles, titanocene compounds, thios Examples thereof include compounds and organic peroxides. Among these photopolymerization initiators, trihaloalkyl-substituted compounds and organic boron salts are particularly preferably used. More preferably, a combination of a trihaloalkyl-substituted compound and an organic boron salt is used. A combination of a trihaloalkyl-substituted compound and an organic boron salt is preferable because sensitivity can be further improved.

  The trihaloalkyl-substituted compound that is a photopolymerization initiator is specifically a compound having at least one trihaloalkyl group such as a trichloromethyl group or a tribromomethyl group in the molecule. Preferred examples include the trihaloalkyl group. S-triazine derivatives and oxadiazole derivatives may be mentioned as compounds in which is bonded to a nitrogen-containing heterocyclic group, or trihaloalkylsulfonyl in which the trihaloalkyl group is bonded to an aromatic ring or a nitrogen-containing heterocyclic ring via a sulfonyl group Compounds.

  Particularly preferred examples of compounds in which a trihaloalkyl group is bonded to a nitrogen-containing heterocyclic group and trihaloalkylsulfonyl compounds are shown below.

  Preferred specific examples of the organic boron salt that is a photopolymerization initiator are shown below.

  Further, the photosensitive layer used in the present invention preferably contains a compound for sensitizing the above-mentioned photopolymerization initiator, and as a sensitizing dye used for sensitizing to a laser having a wavelength range of 380 to 1100 nm. Is cyanine, phthalocyanine, merocyanine, coumarin, porphyrin, spiro compound, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, Examples include styryl, squarylium compounds, and pyrylium compounds. Further, compounds described in European Patent Nos. 0,568,993, U.S. Pat. Nos. 4,508,811, and 5,227,227 are also used. It is possible . Specific examples of the sensitizing dye are shown below, but the present invention is not limited thereto.

  As other elements constituting the photosensitive layer used in the present invention, various colorants are preferably added for the purpose of improving visibility. Thereby, so-called plate inspection properties such as visibility after plate making and suitability for an image density measuring machine as a printing plate can be improved. As the colorant, it is preferable to use a dye or a pigment. Specific examples include, for example, phthalocyanine pigments, azo pigments, carbon black, titanium oxide and other pigments, ethyl violet, crystal violet, azo dyes, anthraquinone dyes. And dyes such as cyanine dyes. The addition amount of the dye and the pigment as the colorant in the photosensitive layer is preferably 0.1 to 10% by mass with respect to the total solid content in the photosensitive layer.

  The thickness of the photosensitive layer is preferably formed on the aluminum support with a dry thickness in the range of 0.5 to 10 μm, and more preferably in the range of 1 to 5 μm, in order to greatly improve printing durability. . The photosensitive layer is coated and dried on the support using various known coating methods.

  In the photosensitive lithographic printing plate used in the present invention, it is also preferable to further provide a protective layer on the photosensitive layer. The protective layer has the effect of preventing the surface of the photosensitive layer from scratches, and prevents the entry of low-molecular compounds such as oxygen and basic substances that inhibit the image formation reaction caused by exposure into the photosensitive layer. It has a preferable effect of further improving the exposure sensitivity.

  Such a device relating to the protective layer has been conventionally devised, and is described in detail in US Pat. No. 3,458,311 and JP-A-55-49729. As a material that can be used for the protective layer, for example, a water-soluble polymer compound having relatively excellent crystallinity is preferably used. Specifically, polyvinyl alcohol, polyvinyl pyrrolidone, acidic celluloses, gelatin, gum arabic, and polyacrylic are used. Water-soluble polymers such as acids are known, and among these, using polyvinyl alcohol as a main component gives the best results for basic properties such as oxygen barrier properties and development removability. The polyvinyl alcohol used for the protective layer may be partially substituted with an ester, an ether, and an acetal as long as it contains an unsubstituted vinyl alcohol unit for having necessary oxygen barrier properties and water solubility. Similarly, some of them may have other copolymer components. The protective layer is preferably formed with a dry thickness in the range of 0.1 to 10 μm, and more preferably in the range of 0.2 to 3 μm. The protective layer is coated and dried on the photosensitive layer using various known coating methods.

  The edge of the photosensitive lithographic printing plate thus produced is preferably chamfered. In the present invention, the chamfering process is a process in which the end surface is lower than the entire surface on the side where the photosensitive layer of the photosensitive lithographic printing plate is provided (the side where the image portion exists after image formation). Means. Such a chamfering process is performed on at least two opposite ends of the photosensitive lithographic printing plate. A mode of the chamfering treatment is not particularly limited, but, for example, a method of controlling the shape of the edge surface at the same time that the photosensitive lithographic printing plate is cut into a desired size with a cutting slitter or the like is preferably used.

  In the plate making method of the photosensitive lithographic printing plate of the present invention, the photosensitive lithographic printing plate described above is exposed and developed to expose the aluminum support surface, and then the malonic acid and / or citric acid is exposed on the aluminum support surface. A plate surface protective agent containing at least

  Light sources used for exposure to form image patterns on photosensitive lithographic printing plates include carbon arc, high pressure mercury lamp, ultra high pressure mercury lamp, low pressure mercury lamp, deep UV lamp, xenon lamp, metal halide lamp, tungsten lamp, halogen lamp, excimer A UV lamp, LED lamp, various fluorescent lamps (white fluorescent lamp, black light, chemical light, etc.) can be used, but scanning exposure with a laser is very preferable in terms of plate making efficiency. Examples of the laser light source include a blue-violet semiconductor laser (violet laser), an argon laser, a helium neon laser, a red LED, a near-infrared laser, and an infrared laser. Among them, a near-infrared laser having a wavelength range of 800 to 830 nm is used. Preferably used. The scanning method may be any of an inner drum method, an outer drum method, a flat scanning method, and the like, but an outer drum method is preferable.

  As a developer for developing the photosensitive lithographic printing plate after exposure, the above-described polymer compound having a polymerizable double bond group has an acidic group such as a carboxyl group or a sulfo group, and the acidic group is a photosensitive layer. In the case where it is in the form of a metal salt or ammonium salt (neutralized salt), it can be developed with a neutral developer having a pH of less than 9. Further, when it is not in the form of a metal salt or an ammonium salt, it can be developed with a conventionally known alkaline developer. By developing using such a developing solution, it becomes possible to expose the surface of the aluminum support that becomes the non-image area.

  The pH of the alkaline developer is preferably 10 or more, and the alkaline developer contains an organic alkaline agent (for example, triethylamine) in addition to an inorganic alkaline agent (for example, sodium hydroxide, sodium carbonate, etc.). In addition, as other additives, various organic solvents such as ethanol, isopropanol, n-butyl cellosolve, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, benzyl alcohol, and anionic, cationic, nonionic, etc. These surfactants can also be added.

  When the polymer compound having a polymerizable double bond group has a neutralized salt of a carboxyl group or a sulfo group, it is possible to develop using pure water as a neutral developer having a pH of less than 9. In the case of a carboxyl group neutralized salt or when a sulfo group neutralized salt cannot be obtained even if it has a sulfo group neutralized salt, an activator is added to the neutral developer for the purpose of improving developability. be able to. Nonionic properties such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, monoglyceride alkyl esters, alkylbenzene sulfonates, alkyl naphthalene sulfonic acids Anionic surfactants such as salts, alkyl sulfates, alkyl sulfonates, sulfosuccinate esters, amphoteric surfactants such as alkyl betaines, amino acids, isopropyl alcohol, benzyl alcohol, ethyl cellosolve, butyl cellosolve, phenyl cellosolve, propylene glycol And water-soluble organic solvents such as diacetone alcohol.

  The development is usually carried out by a known development method such as immersion development, spray development, brush development, ultrasonic development, etc., preferably at a temperature of about 10 to 60 ° C., more preferably about 15 to 45 ° C. for 5 seconds to It takes about 10 minutes. At that time, the protective layer provided as necessary on the photosensitive layer may be removed in advance with water or the like, or may be removed during development.

  After developing with the developer described above to expose the surface of the aluminum support, a stopping step with an acidic aqueous solution, a washing step or the like may be provided, or a drying step may be provided.

  Subsequently, in the plate making method of the present invention, for the purpose of improving the image strength and printing durability, it is also possible to subject the developed image to full post heating or full exposure.

  Next, the plate surface protective agent used in the plate making method of the present invention will be described. The plate surface protective agent of the present invention contains at least malonic acid and / or citric acid. Patent Documents 1 and 2 described above exemplify many inorganic acids and / or organic acids and salts thereof as pH adjusters for maintaining the pH of the plate surface protecting agent at 2.5 to 5. Among these compounds, malonic acid and / or citric acid acts effectively on edge stains that occur when lithographic printing is performed on paper wider than the plate width using neutral dampening water. This is a very specific effect.

  The content of malonic acid and / or citric acid contained in the plate surface protective agent of the present invention is preferably from 0.1 to 50 g / L, more preferably from 1 to 30 g / L in the use solution.

  Although there is no restriction | limiting in particular in pH of the plate surface protection agent of this invention, It is preferable to use in a weak acidic region to an acidic region. In general, the pH of the plate surface protecting agent is preferably 2.5 to 6. However, in order to adjust the pH in this region, apart from the malonic acid and / or citric acid, an inorganic acid, an organic acid and a salt thereof are used. Either or a combination of these can be used. Examples of such compounds include mineral acids such as nitric acid, sulfuric acid, phosphoric acid, and metaphosphoric acid, and organic acids such as acetic acid, p-toluenesulfonic acid, tartaric acid, malic acid, and phytic acid. Examples of the inorganic salt include monobasic sodium phosphate, primary potassium phosphate, primary ammonium phosphate, sodium tripolyphosphate, and the like. These compounds may be used alone or in combination of two or more.

  A preservative can be added to the plate surface protective agent of the present invention. Preservatives include phenol or derivatives thereof, formalin, imidazole derivatives, sodium dehydroacetate, 4-isothiazolin-3-one, benzotriazole derivatives, amming anidine derivatives, quaternary ammonium salts, pyridine, quinoline, guanidine derivatives, diazine, etc. , Triazole derivatives, oxazole, oxazine derivatives, nitrobromoalcohol 2-bromo-2-ethanol, 1,1-dibromo-1-nitro-2-propanol, and the like are preferably used. The content of the preservative is preferably 0.01 to 10 g / L, more preferably 0.1 to 5 g / L. Two or more types can be combined depending on various molds, bacteria, and the like.

  In order for the preservative to act effectively and to block the influence of ions such as calcium brought from tap water, the plate surface protective agent preferably contains a chelating agent. For example, aminopolycarboxylic acids such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, nitrilotriacetic acid, and potassium salts and sodium salts thereof, and organic phosphones such as 1-hydroxyethane-1,1-diphosphonic acid Examples include acids and alkali metal salts thereof. The content of these chelating agents is preferably 0.01 to 10 g / L, more preferably 0.1 to 2 g / L.

  Furthermore, the plate surface protective agent may contain a wetting agent as necessary. As the wetting agent, ethylene glycol, diethylene glycol, glycerin, propylene glycol, hexylene glycol, dipropyl glycol, trimethylolpropane and the like are used. These wetting agents may be used alone or in combination of two or more. The content of these wetting agents is preferably 0.1 to 50 g / L, more preferably 1 to 30 g / L.

  It is advantageous in production, transportation, storage, etc. that the above-mentioned plate surface protective agent is prepared as a concentrated liquid having a water content less than that in use and is diluted with water during use. The degree of concentration in this case is suitably such that each component does not cause separation or precipitation, and depending on the content, it can usually be concentrated to a concentrated solution: water = 1: 0 to 1:10. Further, as a container, it is preferable to use a material that does not break during transportation for safety, and usually a resin container such as a hard bottle or a cubicener is preferably used.

  The plate surface protective agent is applied to the surface of the aluminum support by a method in which absorbent cotton or the like is impregnated with a plate surface protective agent to perform hand etching, a method of applying a certain amount of plate surface protective agent to the plate surface with a bar coater, and a plate surface protective agent. A method of immersing the printing plate in a stored liquid bath or applying a plate surface protective agent to the surface of the printing plate by a shower method and then squeezing the excess plate surface protective agent with a roll pair can be applied.

  These plate making steps may be processed by the methods described in JP-A Nos. 54-8002, 55-1115045, and 59-58431. That is, after the development treatment, the plate surface protection treatment may be performed after washing, or the plate surface protection treatment may be performed as it is, or the plate surface protection treatment may be performed after the treatment with an aqueous solution containing an acid.

  The printing plate obtained by the plate making method of the present invention is lithographically printed using a neutral fountain solution. Here, “neutral” does not indicate that it is completely neutral (pH 7), and the pH is in the range of more than 5 and less than 9 that satisfies the standard value of the Sewerage Law, preferably the Water Pollution Control Law and Tokyo. It is in the range of 5.8 to 8.6 that satisfies the standard value of the Tokyo Metropolitan Sewerage Ordinance, and does not require neutralization or other treatment during drainage.

  Examples of such neutral fountain solution include neutral fountain solutions described in JP-A-2004-106531, JP-A-2005-28853, JP-A-2010-120302, and the like. Neutral fountain solution available as Eco Seven (Sakata Inx Co., Ltd.), PF-2 (Toyo Ink Co., Ltd.), Trebic Neutral (DIC Co., Ltd.), etc. It is also possible to do.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Preparation of photosensitive lithographic printing plate>
A 0.24 mm thick JIS-A1050 aluminum coil was mechanically roughened using a nylon brush and 400 mesh Pamiston water suspension, immersed in a 4% by weight aqueous sodium hydroxide solution at 60 ° C. for 10 seconds, and washed with water. At 30 ° C., a 40 A · dm ² , 60 Hz single layer alternating current was passed in a 1.1% by mass nitric acid electrolyte for 30 seconds to roughen the surface of the electrolyte, washed with water, and then added to a solution containing 10% by mass phosphoric acid at 50 ° C. After dipping for 2 seconds, it was desmutted and washed with water, and after anodizing in a sulfuric acid aqueous solution at 30 ° C. and 25 mass%, it was washed with water and dried to obtain an aluminum support. The center line surface roughness was 0.58 μm.

  On the aluminum support thus obtained, the following photosensitive layer coating solution was applied and dried to a dry film thickness of 2.3 μm to prepare a photosensitive lithographic printing plate.

<Photosensitive layer coating solution>
Polymer compound having polymerizable double bond group (CP-1)
(10% by mass 1,4-dioxane solution) 100 parts by mass Compound (U-1) having both a polymerizable double bond and a urethane bond 7 parts by mass Low molecular compound (C-5) having a polymerizable double bond group 2 Part by mass Photopolymerization initiator 1 (BC-6) 2 parts by mass Photoinitiator 2 (T-1) 1 part by mass Infrared absorbing dye (S-13) 0.5 part by mass 10% by mass Copper phthalocyanine dispersion 15 Part by mass Fluorosurfactant (FTX-218G) [manufactured by Neos Co., Ltd.] 0.01 part by weight 1,4-dioxane 70 part by mass Cyclohexanone 20 part by mass

  The photosensitive lithographic printing plate produced as described above was cut into a size of 400 mm × 670 mm, and chamfered using a commercially available shearing machine [manufactured by AMADA; M-1245].

  The photosensitive lithographic printing plate subjected to the chamfering treatment is exposed using a thermal image setter PT-R4000 [manufactured by Dainippon Screen Mfg. Co., Ltd .; oscillation wavelength 830 nm], and then an automatic processor P-1310 [large] Nippon Screen Manufacturing Co., Ltd.] was used, and a developing solution having the following formulation was subjected to a treatment at 28 ° C. for 23 seconds. Subsequently, a plate surface treating agent having the following formulation was applied to the printing plate after the developing treatment.

<Developer>
N-ethylethanolamine 35g
Phosphoric acid (85 mass% solution) 10g
Potassium hydroxide (amount to adjust pH to 11.7)
Alkyl naphthalenesulfonic acid Na (35% by mass solution) 30 g
Diethylenetriaminepentaacetic acid 1g
Water was added to make 1L.
pH is 11.7 (25 ° C)

<Plate surface treatment agent>
Phosphoric acid 1 potassium 20g
Gum arabic 30g
Sodium dehydroacetate 0.5g
Organic acid Amounts listed in Table 1 EDTA2Na 1 g
Water was added to make 1L.
The types of organic acids are shown in Table 1.

<Evaluation of edge dirt>
Using the printing machine Heidelberg KORD [trademark of offset printer manufactured by Heidelberg], ink [manufactured by Toyo Ink Co., Ltd .; Thus, printing was performed on paper having a width wider than that of the printing plate. Printing was performed by a method in which the entire surface of the plate was soiled with ink, and then a dampening liquid roll was touched on the plate surface. In addition, it was confirmed that the pH values of the dampening waters of Comparative Examples 1 to 3 and Inventions 1 to 3 used in the present invention were all 7 and neutral.
○: The stain on the edge of the printing plate is eliminated at the 300th sheet after printing.
Δ: Dirt on the end of the printing plate is eliminated after 300 sheets or more and less than 3000 sheets after printing.
X: Dirt on the end of the printing plate is not eliminated even after printing 3000 sheets or more.

  As is apparent from the results in Table 1, according to the present invention, when a lithographic printing is performed on a paper having a width wider than that of the printing plate using a neutral dampening solution, ink adheres to the edge of the printing plate. It can be seen that the resulting edge contamination has been improved.

Claims (1)

  A method for making a photosensitive lithographic printing plate having a photosensitive layer on an aluminum support for producing a printing plate for lithographic printing on paper wider than the printing plate width using a neutral fountain solution. The photosensitive lithographic printing plate is exposed and developed to expose the surface of the aluminum support, and then the surface of the aluminum support is provided with a plate surface protective agent containing at least malonic acid and / or citric acid. Plate making method.