JP2006208529A - Negative photosensitive lithographic printing plate for laser exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative photosensitive lithographic printing plate for laser exposure having proper printing durability and large development latitude. <P>SOLUTION: The negative photosensitive lithographic printing plate for laser exposure has on an aluminum support a photosensitive layer, containing at least a polymer having a polymerizable vinyl phenyl group at a side chain and having a carboxyl group containing monomer as a copolymerization component, and a polymerization initiator, wherein the aluminum support has micropits, having an opening diameter of 0.02-0.3 μm formed in a surface thereof and the number of the micropits per unit area satisfies Formula (1): N>1/(A×2), where N represents the number of micropits per mm<SP>2</SP>, and A represents an average opening area (mm<SP>2</SP>) of micropits, having an opening diameter of 0.02-0.3 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a negative photosensitive lithographic printing plate.

  In general, a negative photosensitive lithographic printing plate having an aluminum plate as a support is obtained by applying a photosensitive composition on the support, exposing to exposure to activating light through a negative, etc., curing the exposed area, and using a developer. A cured coating having an oleophilic surface is formed on an aluminum support having a hydrophilic surface by dissolving and removing the unexposed portion while leaving the exposed portion.

  As the above-mentioned photosensitive composition, a combination of a diazo resin and a polymer compound is widely used. By Yonezawa Teruhiko, “Introduction to PS Version” (published by the Printing Society of Japan), Mototaro Nagamatsu and Hideo Inui. , “Photosensitive polymer” (published by Kodansha), Ayao Yamaoka, Mototaro Matsunaga, “Photopolymer Technology” (published by Nikkan Kogyo), etc.

  Further, various companies have proposed CTP systems that directly expose image data on a printing plate by using a laser beam directly without interposing a film by the progress of computers in recent years. For example, as disclosed in JP-A-7-20629, JP-A-7-271029, etc., an infrared absorber is subjected to photothermal conversion, and the exposed portion is locally heated to a high temperature. A lithographic printing plate in which an image portion is formed by crosslinking a resin and a novolac resin. Further, there are lithographic printing plates utilizing a photopolymerization reaction containing a polymerization initiator, a photosensitizing dye, and a polymerizable monomer, which are described in “Printing Magazine”, vol. 78, p. 9, 1995.

  However, the above-described photosensitive lithographic printing plate has a problem that it is difficult to ensure stability such as sensitivity and long-term storage stability. For this reason, the oxygen barrier property is enhanced on the upper part of the photosensitive layer, and surface scratches are prevented. It is common practice to provide an overlayer made of the desired polyvinyl alcohol or the like. Due to the presence of such an over layer, there is a problem of deterioration in image quality due to light scattering during laser exposure, and when developing, a pre-water washing step for removing the over layer is required prior to alkali development. In addition, there is a problem in that a process for applying an overlayer is necessary after the photosensitive layer is applied.

  In order to improve these problems, there is no overlayer, polymerization initiator, dye sensitizer and polymerizable compound, polymerization by radicals generated from the polymerization initiator with light energy absorbed by the dye sensitizer JP-A-2001-290271 (Patent Document 1), JP-A-2001-272778, (Patent Document 2), and JP-A-2002-28734 (Patent Document 3) as techniques using polymerization of a functional compound. A photosensitive composition containing a polymer having a phenyl group substituted with a vinyl group in the side chain, a photo radical generator, and a sensitizing dye is disclosed. In a lithographic printing plate using such a photosensitive composition, generally, when the development temperature is increased or the development process is performed for a longer time, the image portion is likely to be lost, the development temperature is decreased, or the development is performed. If the development process is performed for a short time, the photosensitive layer tends to remain in the non-image area. In general, it is preferable that the range of development conditions (temperature, time) (hereinafter referred to as “development latitude”) for performing plate making with no loss of image and good dissolution of non-image areas is preferable.

  The wide development latitude has an advantage that, for example, in the development processing of a lithographic printing plate, plate making with good printing performance can be performed even when a large amount of plate making is carried out, even when the developer is deteriorated. Further, depending on the type of commercially available automatic processor, the structure may be slightly different, but in this case as well, there is an advantage that plate making with good printing performance can be performed.

As a method for ensuring sufficient printing durability and stain resistance, in the field of general photosensitive lithographic printing plates, it is known to make the surface shape of an aluminum support a specific shape. For example, JP-A-8-300844 (Patent Document 4) describes a triple structure having a large wave, a medium wave, and a small wave that defines the opening diameters of the medium wave and the small wave. Japanese Patent Application Laid-Open No. 11-99758 (Patent Document 6) and Japanese Patent Application Laid-Open No. 11-208138 (Patent Document 8) describe that the diameter of a small wave is defined in a large and small double structure. Japanese Patent Application Laid-Open No. 11-167207 (Patent Document 7) describes a technique for providing finer protrusions in addition to large and small double recesses (pits). Japanese Patent No. 2023476 (Patent Document 10) describes a double structure that defines an opening diameter. JP-A-8-300844 (Patent Document 4) describes a double structure that defines a factor a30 indicating the smoothness of the surface. Japanese Patent Application Laid-Open No. 10-35133 (Patent Document 5) describes a structure that defines a ratio of pit diameters to be superimposed in a plurality of electrochemical surface roughening treatments (hereinafter referred to as “electrolytic surface roughening treatment”). Has been. Japanese Patent Application Laid-Open No. 2004-284304 (Patent Document 9) defines a ratio between the opening diameter and the depth of a double structure that defines the opening diameter.
JP 2001-29071 A JP 2001-272778 A JP 2002-28734 A JP-A-8-300844 Japanese Patent Laid-Open No. 10-35133 JP 11-99758 A JP 11-167207 A Japanese Patent Laid-Open No. 11-208138 JP 2004-284304 A Japanese Patent No. 2023476

  An object of the present invention is to provide a laser-sensitive negative lithographic printing plate provided with a photosensitive layer containing at least a polymer having a polymerizable styrene group in the side chain and a polymerization initiator. To provide a lithographic printing plate.

The object of the present invention is to provide a photosensitive layer containing at least a polymerization initiator and a polymer having a polymerizable vinylphenyl group in a side chain and a carboxyl group-containing monomer as a copolymerization component on an aluminum support. In a negative photosensitive lithographic printing plate printing plate for laser exposure, fine pits having an opening diameter of 0.02 to 0.3 μm are formed on the surface of the aluminum support, and each unit area of the fine pits Was achieved by satisfying the following formula 1.
N> 1 / (A × 2) (Formula 1)
In the formula, N represents the number of micro pits of 0.02 to 0.3 μm per 1 mm ² , and A represents the average opening area (mm ² ) of micro pits having an opening diameter of 0.02 to 0.3 μm.

  According to the present invention, in a negative photosensitive lithographic printing plate for laser exposure in which a photosensitive layer containing at least a polymer having a polymerizable vinylphenyl group in the side chain and a polymerization initiator is provided on an aluminum support, the development latitude is wide. A negative photosensitive lithographic printing plate for laser exposure can be provided.

  As a result of various studies on the surface treatment of an aluminum support, the present inventors have made a negative for laser exposure provided with a photosensitive layer containing at least a polymer having a polymerizable vinylphenyl group in the side chain and a polymerization initiator. In the type photosensitive lithographic printing plate, it has been found that the use of an aluminum support having fine pits and frequent occurrence of pits is effective in preventing image loss and can widen the development latitude. .

The present invention will be described in detail below. The number of fine pits having an opening diameter of 0.02 to 0.3 μm according to the present invention is such that the number N per 1 mm ² satisfies the above formula 1, and the average number of minute pits having an opening diameter of 0.02 to 0.3 μm is N. The opening area A is obtained from a photograph taken by adjusting the brightness and contrast so that minute pits having an opening diameter of 0.02 to 0.3 μm can be clearly photographed with a scanning electron microscope at 50,000 times. As a specific method, the photograph is converted into a digital image by a scanner, and then converted into an image-processed monochrome two-tone image. Here, all pits other than minute pits having an opening diameter of 0.02 to 0.3 μm are erased. At this time, when the pit shape is not a perfect circle, the opening diameter of a portion having a short length is targeted.

The number of pits is counted from this image, and N is calculated in terms of the number per 1 mm ² . Further, the number of bits of the white portion and black portion of the monochrome two-tone image is counted to obtain the area ratio of the black portion which is the pit portion, and the total area of the pit is calculated. By dividing this total area by the number of pits N, an average opening area A is obtained. That is, Equation 1 means that the frequency of pit generation according to the opening diameter is 2 for the surface area of aluminum and the opening area of the pit is 1 or more.

  It is preferable that the micro pits having an opening diameter of 0.02 to 0.3 μm have many micro pits having an opening diameter of 0.1 μm or less. Further, the micro pit having an opening diameter of 0.02 to 0.3 μm according to the present invention may have a superposed structure in which a pit having an opening diameter of about 0.02 μm exists in a pit having an opening diameter of about 0.3 μm. In this case, the smaller pit is the target of calculation. The center depth or height of the minute pit having an opening diameter of 0.02 to 0.3 μm is 1/3 or more, preferably about 1/2 to 3 of the opening diameter of the pit.

  The aluminum support having fine pits having an opening diameter of 0.02 to 0.3 μm according to the present invention is a method of manufacturing an aluminum support used in a general lithographic printing plate. Various processes are combined with surface treatment conditions. It can be made by things. As a manufacturing method thereof, for example, there are a method of combining the conditions of the electrolytic surface roughening treatment and the conditions of the desmut treatment, a method of selecting a liquid composition in the anodizing treatment, or a method of performing a post-treatment after the anodizing treatment.

In the case of producing by combining the electrolytic surface roughening treatment condition and the desmut treatment condition, for example, a 1% by mass hydrochloric acid solution is used as the electrolytic solution, the treatment temperature is 40 ° C., the voltage is 12 V, and the quantity of electricity is 450 coulomb / dm. After the electrolytic surface-roughening treatment in No. ² , it can be obtained by performing a desmut treatment at 25 ° C. or lower using a 2% by mass aqueous sodium hydroxide solution, and then performing a general anodizing treatment.

Moreover, when producing by selection of the liquid composition of an anodizing process, for example, after a general roughening process and a desmut process, it is processed using the liquid mixture of 25 mass% sulfuric acid and 5 mass% phosphoric acid. It can be obtained by anodizing at a temperature of 30 ° C., a current density of 0.1 to 10 A / dm ² , and a voltage of 5 to 30 V.

  Furthermore, when producing by selection of a post-process, it can obtain by processing with a 90 degreeC or more hot water after a general roughening process, a desmut process, and an anodizing process, for example.

  The surface treatment method used for general lithographic printing plates will be described below. As the aluminum plate, an aluminum alloy plate containing a small amount of pure aluminum and various metals such as silicon, magnesium, iron, copper, zinc, manganese, chromium and titanium is used.

  In order to use the aluminum plate as a support for an offset printing plate, surface treatment is performed before applying the photosensitive layer. In the surface treatment, degreasing, roughening, desmutting, and anodizing are generally performed. These treatments are usually carried out continuously using an aluminum coil, and water washing is added as necessary after each treatment.

  The degreasing treatment is performed so that the oxide film generated by contact with oil or air during rolling of the aluminum surface is removed, the surface of the clean aluminum plate is exposed, and the subsequent steps can be processed evenly. . Examples of the degreasing treatment include solvent degreasing using trichlorethylene, perchlorethylene, etc., alkali degreasing using sodium hydroxide, sodium carbonate, sodium metasilicate, trisodium phosphate, tetrasodium pyrophosphate, soap, or a mixture thereof. In addition, there are methods such as emulsion degreasing combined with surfactant, kerosene, triethanolamine, sodium hydroxide and the like, and electrolytic degreasing called final degreasing to remove contamination that cannot be removed by the above chemical degreasing.

  In general, the roughening treatment is to give unevenness to the surface. Mechanical roughening methods such as brush graining, ball graining and liquid honing, and chemical roughening methods by chemical etching with hydrochloric acid or nitric acid. Alternatively, an electrolytic surface roughening method by electrochemical etching with these acids, or a method of roughening by combining them is known.

The electric power supplied to the aluminum plate in the electrolytic surface-roughening method varies depending on the composition of the electrolytic solution, the temperature, the distance between the electrodes, and the like. The current density on the processing surface is 5 to 60 A / dm ² , and the amount of electricity is 50 to 4000 coulombs. Moreover, the temperature of electrolyte solution is 0-60 degreeC, and the distance of an electrode and an aluminum plate is the range of 1-10 cm.

  As the electrolytic solution, nitric acid or a salt thereof, hydrochloric acid or a salt thereof, or an aqueous solution of one or a mixture of two or more thereof can be used. If necessary, sulfuric acid, phosphoric acid, chromic acid, boric acid, organic acids or their salts, nitrates, chlorides, ammonium salts, amines, surfactants, other corrosion accelerators, corrosion inhibitors, stabilization It is used by adding an agent.

  As the concentration of the electrolytic solution, the concentration of the above acids is 0.1 to 10% by mass, and the concentration of aluminum ions in the electrolytic solution is maintained in the range of 0 to 10 g / liter. Also, in the electrolytic surface roughening treatment, aluminum melts and acids are consumed due to the progress of electrolysis, so that a part of the electrolytic solution is discarded so that the composition of the electrolytic solution does not deviate from the predetermined setting range. It is common to replenish acids.

  The desmut process is a process for dissolving and removing the smut generated by the roughening process. After the roughening treatment, the smut dissolves and the pit surface appears by desmutting. In desmut treatment, alkali agents such as sodium hydroxide, acids such as phosphoric acid, sulfuric acid, nitric acid, perchloric acid, or a mixture thereof can be used, but there are differences in the ability to remove smut. The removal ability is adjusted according to the concentration or processing temperature.

  The roughened and desmutted aluminum plate is then anodized. In the offset printing plate support, a porous anodic oxide film is formed as an oxide film in order to improve the water retention of the surface and the adhesion of the photosensitive layer.

  As the anodic oxidation electrolyte, an acid having a low solubility of the formed oxide film is preferable, and sulfuric acid, oxalic acid, chromic acid, phosphoric acid, or a mixture thereof can be used. The size of the micropores of the anodic oxide film produced during anodic oxidation varies depending on the type of acid, and is usually about 0.01 μm, and the opening diameter of the present invention is outside the range of 0.02 to 0.3 μm. However, depending on the method of anodizing treatment, micropores having an opening diameter in the range of 0.02 to 0.3 μm can be produced, and in that case, it is an object of the present invention.

Since the anodic oxide film is formed only on the anode, a direct current is usually used as the current. As conditions for anodization, the liquid concentration is 1 to 40% by mass, the current density is 0.1 to 10 A / dm ² , and the voltage is 5 to 30 V. The current is supplied by the direct feeding method or the indirect feeding method. The thickness of the anodic oxide film is changed depending on the current density and time, and is appropriately adjusted depending on the printing durability grade of the printing plate. The temperature affects the hardness of the anodized film, and the hardness is higher at a lower temperature, but is inferior in flexibility, so that it is usually anodized at a temperature near room temperature. After the anodizing treatment, a water washing treatment is performed.

  In general lithographic printing plates, post-treatment is performed after anodizing treatment as necessary. Post-treatment methods include, for example, a method of hydrothermal treatment, a method of immersing in an aqueous solution of polyvinylphosphonic acid disclosed in British Patent No. 1,230,447, a method of immersing in a silicate solution, A method of providing an undercoat layer of a hydrophilic polymer is known.

  In the present invention, the composition of the photosensitive layer provided on the aluminum support will be described in detail later, but at least a polymer having a polymerizable vinylphenyl group in the side chain and a carboxyl group-containing monomer as a copolymerization component, and It contains a photopolymerization initiator, and preferably further contains a polymerizable monomer. Furthermore, a sensitizing dye, a polymerization inhibitor, a surfactant, a color pigment, and the like are added as necessary. Accordingly, the coating solution for the photosensitive layer contains the above-described chemicals in a state dissolved or dispersed in an organic solvent.

  The concentration of all the above-mentioned drugs in the coating solution is prepared at a concentration of about 5 to 30% by mass. Among them, the polymer concentration is preferably 1 to 25% by mass. The dry film thickness of the photosensitive layer is preferably formed in the range of 0.5 to 10 μm, particularly preferably in the range of 1 to 5 μm. Therefore, the coating amount of the coating solution is set from the preset thickness of the photosensitive layer and the polymer concentration in the coating solution.

  Examples of the coating method include roll coating, dip coating, air knife coating, gravure coating, hopper coating, blade coating, and wire doctor coating.

  The organic solvent having a boiling point of less than 110 ° C. containing 50% by mass or more of the total organic solvent used in the coating liquid of the present invention is particularly limited as long as it is an organic solvent having a boiling point of less than 110 ° C. under atmospheric pressure. Can be used instead of things. For example, acetone, methyl ethyl ketone, methanol, ethanol, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, cyclohexane, methyl acetate, ethyl acetate and the like can be mentioned. Particularly preferred organic solvents include tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane. It is necessary to contain 50% by mass or more with respect to the total organic solvent, preferably 70% by mass or more, and more preferably 80% by mass or more.

  In addition to the organic solvent, it is one of the preferred embodiments to contain a high boiling point solvent of 110 ° C. or higher depending on various purposes such as the stability of the dispersion in the coating liquid and the coating surface stability aid. For example, N.A. N dimethylformamide, cyclohexanone, ethylene glycol monoethyl ether and the like are preferably used. However, a large amount remaining in the photosensitive layer is not preferable because it causes deterioration of storage stability with time and deterioration of printing durability as printing performance as described above. The content needs attention and is preferably 30% by mass or less, more preferably 20% or less of the total organic solvent.

  The polymer having a vinylphenyl group in the side chain and having a carboxyl group-containing monomer as a copolymerization component used in the present invention will be described. As the carboxyl group-containing monomer, acrylic acid, methacrylic acid, acrylic acid 2-carboxyethyl ester, methacrylic acid 2-carboxyethyl ester, crotonic acid, maleic acid, fumaric acid, maleic acid monoalkyl ester, fumaric acid monoalkyl ester, Examples include 4-carboxystyrene and the like.

  The polymer used in the present invention is a polymer having a polymerizable vinylphenyl group in the side chain and a carboxy group-containing monomer as a copolymerization component. The vinylphenyl group is bonded to the main chain directly or through a linking group, and the linking group is not particularly limited, and includes any group, atom, or a combination thereof. The phenyl group may be substituted with a substitutable group or atom, and the vinyl group is a halogen atom, carboxy group, sulfo group, nitro group, cyano group, amide group, amino group, alkyl group, aryl group. , An alkoxy group, an aryloxy group and the like may be substituted. More specifically, the polymer having a vinylphenyl group in the side chain described above has a group represented by the following chemical formula 1 in the side chain.

In the formula, Z ₁ represents a linking group, and R ₁ , R ₂ , and R ₃ are a hydrogen atom, a halogen atom, a carboxy group, a sulfo group, a nitro group, a cyano group, an amide group, an amino group, an alkyl group, and an aryl group. A group, an alkoxy group, an aryloxy group, and the like, and these groups may be substituted with an alkyl group, an amino group, an aryl group, an alkenyl group, a carboxy group, a sulfo group, a hydroxy group, or the like. R ₄ represents a substitutable group or atom. n ₁ represents 0 or 1, m ₁ represents an integer of 0 to 4, and k ₁ represents an integer of ₁ to 4.

The above general formula will be described in more detail. As the linking group for Z ₁ , an oxygen atom, a sulfur atom, an alkylene group, an alkenylene group, an arylene group, —N (R ₅ ) —, —C (O) —O—, —C (R ₆ ) ═N—, Examples include —C (O) —, a sulfonyl group, a heterocyclic group, and a group represented by the following chemical formula 2 alone or in combination of two or more. Here, R ₅ and R ₆ represent a hydrogen atom, an alkyl group, an aryl group, or the like. Furthermore, the above-described linking group may have a substituent such as an alkyl group, an aryl group, or a halogen atom.

Examples of the heterocyclic group include pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, isoxazole ring, oxazole ring, oxadiazole ring, isothiazole ring, thiazole ring, thiadiazole ring, thiatriazole ring, indole ring. , Indazole ring, benzimidazole ring, benzotriazole ring, benzoxazole ring, benzthiazole ring, benzselenazole ring, benzothiadiazole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, quinoxaline ring, etc. A nitrogen-containing heterocyclic ring, a furan ring, a thiophene ring, and the like, and a substituent may be bonded to these heterocyclic rings.
Although the example of group represented by Chemical formula 1 is shown below, it is not limited to these examples.

Among the groups represented by the above chemical formula 1, preferred ones exist. That is, it is preferable that R ₁ and R ₂ are hydrogen atoms and R ₃ is a hydrogen atom or a lower alkyl group having 4 or less carbon atoms (methyl group, ethyl group, etc.). Furthermore, as the linking group for Z ₁ , those containing a heterocyclic ring are preferred, and those in which k ₁ is 1 or 2 are preferred.

  Examples of polymers having a group represented by Chemical Formula 1 and having a carboxy group-containing monomer as a copolymerization component are shown below. In the formula, the number represents the mass% of each repeating unit in the copolymer total composition of 100 mass%.

  The polymer of the present invention may further contain another monomer as a copolymer component. Other monomers include styrene derivatives such as styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-carboxystyrene, 4-aminostyrene, chloromethylstyrene, 4-methoxystyrene, methyl methacrylate, Methacrylic acid alkyl esters such as ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and dodecyl methacrylate, aryl methacrylates or alkylaryl esters such as phenyl methacrylate and benzyl methacrylate , 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methoxydiethylene glycol monoester methacrylate, methoxyethylene methacrylate Methacrylic acid esters having an alkyleneoxy group such as glycol monoester and methacrylic acid polypropylene glycol monoester, amino group-containing methacrylic acid esters such as 2-dimethylaminoethyl methacrylate and 2-diethylaminoethyl methacrylate, or acrylic acid esters Examples of these corresponding methacrylic acid esters, or monomers having a phosphoric acid group such as vinylphosphonic acid, amino group-containing monomers such as allylamine and diallylamine, or vinylsulfonic acid and its salts, allylsulfone Monomers having a sulfonic acid group such as acid and its salt, methallylsulfonic acid and its salt, styrenesulfonic acid and its salt, 2-acrylamido-2-methylpropanesulfonic acid and its salt As monomers having a nitrogen-containing heterocyclic ring such as 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazole, N-vinylcarbazole, or monomers having a quaternary ammonium base, 4-vinylbenzyltrimethylammonium chloride, acryloyloxyethyl Trimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, quaternized product of dimethylaminopropylacrylamide with methyl chloride, quaternized product of N-vinylimidazole with methyl chloride, 4-vinylbenzylpyridinium chloride, or acrylonitrile, methacrylonitrile, Acrylamide, methacrylamide, dimethylacrylamide, diethylacrylamide, N-isopropyl acrylate Acrylamide or methacrylamide derivatives such as amide, diacetone acrylamide, N-methylol acrylamide, N-methoxyethyl acrylamide, 4-hydroxyphenyl acrylamide, acrylonitrile, methacrylonitrile, phenylmaleimide, hydroxyphenylmaleimide, vinyl acetate, chloroacetic acid Vinyl esters such as vinyl, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl benzoate, and vinyl ethers such as methyl vinyl ether and butyl vinyl ether, N-vinyl pyrrolidone, acryloyl morpholine, tetrahydrofurfuryl methacrylate, vinyl chloride , Various monomers such as vinylidene chloride, allyl alcohol, vinyltrimethoxysilane, glycidyl methacrylate, etc. And the like.

  There is a preferable range for the molecular weight of the polymer according to the present invention, and the mass average molecular weight is preferably in the range of 1,000 to 1,000,000, and more preferably in the range of 5,000 to 500,000.

  As the polymerization initiator of the present invention, any compound can be used as long as it is a compound capable of generating radicals by light irradiation. For example, trihaloalkyl-substituted compounds (for example, triazine compounds and oxadiazole derivatives as trihaloalkyl-substituted nitrogen-containing heterocyclic compounds, trihaloalkylsulfonyl compounds), hexaarylbisimidazoles, titanocene compounds, ketoxime compounds, thio compounds, organic compounds A peroxide etc. are mentioned. Among these photopolymerization initiators, organic boron salts are preferably used, and more preferably, organic boron salts and trihaloalkyl-substituted compounds are used. As the organic boron salt preferably used, a compound having an organic boron anion represented by Chemical formula 12 is used.

In the chemical formula 12, R ₁₁ , R ₁₂ , R ₁₃ and R ₁₄ may be the same or different and are each an alkyl group, aryl group, aralkyl group, alkenyl group, alkynyl group, cycloalkyl group, heterocyclic group. Represents. Of these, it is particularly preferred that one of R ₁₁ , R ₁₂ , R ₁₃ and R ₁₄ is an alkyl group and the other substituent is an aryl group.

  As said organic boron salt, it is a salt containing the organic boron anion represented by the chemical formula 12 shown previously, and an alkali metal ion and an onium compound are preferably used as a cation which forms a salt. Particularly preferable examples of the onium salt with an organic boron anion include ammonium salts such as tetraalkylammonium salts, sulfonium salts such as triarylsulfonium salts, and phosphonium salts such as triarylalkylphosphonium salts. Examples of particularly preferred organic boron salts are shown below.

  There is a preferable range for the proportion of the organic boron salt in the photosensitive layer, and the organic boron salt is preferably contained in the range of 0.1 to 50 parts by mass in 100 parts by mass of the photosensitive layer. .

  A preferred polymerization initiator used in combination with the organic boron salt according to the present invention is a trihaloalkyl-substituted compound. The trihaloalkyl-substituted compound mentioned here is specifically a compound having at least one trihaloalkyl group such as a trichloromethyl group or a tribromomethyl group in the molecule, and preferred examples include the trihaloalkyl group. Examples of the compound bonded to the nitrogen heterocyclic group include s-triazine derivatives and oxadiazole derivatives, or a trihaloalkylsulfonyl compound in which the trihaloalkyl group is bonded to an aromatic ring or a nitrogen-containing heterocyclic ring via a sulfonyl group. Can be mentioned.

  Particularly preferred examples of trihaloalkyl-substituted nitrogen-containing heterocyclic compounds and trihaloalkylsulfonyl compounds are shown below.

  When a trihaloalkyl-substituted compound is used, there is a preferred range in the photosensitive layer of the photosensitive lithographic printing plate, and the proportion in the total 100 parts by mass of the photosensitive layer is 0.1 to 50 parts by mass. It is preferably included in the range of parts. Further, these are preferable because the sensitivity is particularly improved when they are contained in the photosensitive layer together with the above-described organic boron salt. In this case, the ratio to the organic boron salt is trihaloalkyl substitution with respect to 1 part by mass of the organic boron salt. The compound is preferably contained in the range of 0.1 to 50 parts by mass.

  The photosensitive layer of the negative photosensitive lithographic printing plate of the present invention preferably contains a polymerizable monomer. By combining this, a higher sensitivity can be realized, and a lithographic printing plate excellent in printing performance can be obtained.

  Examples of the polymerizable monomer include polymerizable compounds having a polymerizable double bond. Examples of preferred polymerizable monomers include 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, trisacryloyloxyethyl isocyanurate, tripropylene glycol diacrylate. Examples thereof include polyfunctional acrylic monomers such as acrylate, ethylene glycol glycerol triacrylate, glycerol epoxy triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

  Alternatively, an oligomer having radical polymerizability is preferably used in place of the above-described polymerizable compound, and polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, etc. as various oligomers into which acryloyl group or methacryloyl group is introduced Are also used in the same manner, but these can also be preferably used as ethylenically unsaturated compounds.

  A more preferable embodiment of the polymerizable monomer includes a polymerizable compound having two or more phenyl groups substituted with vinyl groups in the molecule. When this compound is used, crosslinking is effectively carried out by recombination of styryl radicals generated by the generated radicals, which is extremely preferable for producing a highly sensitive negative photosensitive lithographic printing plate.

  A polymerizable compound having two or more phenyl groups substituted with vinyl groups in the molecule is typically represented by the following general formula.

In the formula, Z ₂ represents a linking group, and R ₂₁ , R ₂₂ and R ₂₃ are a hydrogen atom, a halogen atom, a carboxy group, a sulfo group, a nitro group, a cyano group, an amide group, an amino group, an alkyl group, and an aryl group. An alkoxy group, an aryloxy group, and the like, and these groups may be substituted with an alkyl group, an amino group, an aryl group, an alkenyl group, a carboxy group, a sulfo group, a hydroxy group, or the like. R ₂₄ represents a substitutable group or atom. m ₂ represents an integer of 0 to 4, and k ₂ represents an integer of 2 or more.

Further details will be described. As the linking group for Z ₂ , an oxygen atom, a sulfur atom, an alkylene group, an alkenylene group, an arylene group, —N (R ₂₅ ) —, —C (O) —O—, —C (R ₂₆ ) ═N—, Examples include —C (O) —, a sulfonyl group, a heterocyclic group, or a group in which two or more are combined. Here, R ₂₅ and R ₂₆ represent a hydrogen atom, an alkyl group, an aryl group, or the like. Furthermore, the above-described linking group may have a substituent such as an alkyl group, an aryl group, or a halogen atom.

  Examples of the heterocyclic group include pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, isoxazole ring, oxazole ring, oxadiazole ring, isothiazole ring, thiazole ring, thiadiazole ring, thiatriazole ring, indole ring. , Indazole ring, benzimidazole ring, benzotriazole ring, benzoxazole ring, benzthiazole ring, benzselenazole ring, benzothiadiazole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, quinoxaline ring, etc. A nitrogen-containing heterocyclic ring, a furan ring, a thiophene ring and the like, and a substituent may be bonded to these.

Among the compounds represented by the formula 17, there are preferable compounds. That is, R ₂₁ and R ₂₂ are hydrogen atoms, R ₂₃ is a hydrogen atom or a lower alkyl group having 4 or less carbon atoms (methyl group, ethyl group, etc.), and k ₂ is preferably a compound of 2-10. Specific examples of the compound represented by Chemical Formula 17 are shown below, but the invention is not limited to these examples.

  There is a preferred range for the proportion of the polymerizable monomer as described above in the photosensitive layer of the negative photosensitive lithographic printing plate, and the polymerizable monomer is 1 to 60 parts by mass in 100 parts by mass of the photosensitive layer. It is preferable that it is contained in the range of 5 mass parts to 50 mass parts.

  It is preferable to add a sensitizing dye to the photosensitive layer of the negative photosensitive lithographic printing plate of the present invention. As the sensitizing dye to be added, those which sensitize the decomposition of the polymerization initiator in a wavelength range of 380 nm to 1300 nm, and various cationic dyes, anionic dyes and neutral dyes having no charge include merocyanine and coumarin. , Xanthene, thioxanthene, azo dyes and the like can be used. Among these, particularly preferable examples are dyes selected from cyanine, carbocyanine, hemicyanine, methine, polymethine, triarylmethane, indoline, azine, thiazine, xanthene, oxazine, acridine, rhodamine, and azamethine dyes as cationic dyes. It is. In combination with these cationic dyes, they are preferably used because of their particularly high sensitivity and excellent storage stability. Furthermore, in recent years, an output machine (plate setter) equipped with a violet semiconductor laser having an oscillation wavelength in the range of 380 to 410 nm has been developed. As a photosensitive system having high sensitivity corresponding to this output machine, a system containing a pyrylium compound or a thiopyrylium compound as a sensitizing dye is preferable. Examples of preferred sensitizing dyes according to the present invention are shown below.

  Examples particularly preferred as a sensitizing dye in a system for imparting photosensitivity to light in the near infrared to infrared wavelength region of 750 nm or more are shown below.

  There is a preferred range in the quantitative ratio of the sensitizing dye and the polymerization initiator as described above. The photopolymerization initiator is preferably used in the range of 0.01 parts by weight to 100 parts by weight with respect to 1 part by weight of the sensitizing dye, more preferably in the range of 0.1 parts by weight to 50 parts by weight. Is preferably used.

  The photosensitive layer of the photosensitive lithographic printing plate of the present invention preferably contains a colorant. It is used for improving the visibility of the image area, and more preferably has absorption in the visible light region in order to improve the safelight property. It is also preferable to contain a colorant in the photosensitive wavelength region for improving the image quality. Examples of these colorants include inorganic pigments, organic pigments, and dyes as described below.

  Examples of inorganic pigments include mica-like iron oxide, red lead, yellow lead, silver vermilion, ultramarine, titanium dioxide, coated mica, stone team chromate, titanium yellow, zinc chromate, molybdenum red, chromium oxide, calcium leadate, and the like. . Organic pigments include carbon black, phthalocyanine pigment, monoazo pigment, disazo pigment, condensed azo pigment, isoindolinone pigment, quinophthalone pigment, nickel azo pigment, perinone pigment, perylene pigment, anthrone pigment, quinacridone pigment, anthraquinone pigment, Examples thereof include thioindigo pigments, dioxazine pigments, indanthrone pigments, and pyranthrone pigments. Examples of the dye include various dyes such as a phthalocyanine dye, a triarylmethane dye, an anthraquinone dye, and an azo dye.

  The above pigments and dyes may be used alone, but two or more of them may be used in combination.

  A polymerization inhibitor can also be preferably added as another element constituting the photosensitive lithographic printing plate. For example, compounds such as quinone and phenol are preferably used, and compounds such as hydroquinone, p-methoxyphenol, catechol, t-butylcatechol, 2-naphthol, and 2,6-di-t-butyl-p-cresol are used. Preferably used. The preferred proportion of these polymerization inhibitors and the aforementioned ethylenically unsaturated compounds is preferably used in the range of 0.001 to 0.1 parts by mass with respect to parts by mass of the ethylenically unsaturated compounds.

  Since the photosensitive layer of the present invention uses a polymer having a phenyl vinyl group and has sufficient sensitivity, it is necessary to provide an over layer made of polyvinyl alcohol or the like for the purpose of enhancing the oxygen barrier property on the upper side of the photosensitive layer. There is no.

  As the developer of the present invention, any aqueous alkaline solution can be used as long as the pH is 8 or more. Examples of the alkali agent include sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide, sodium borate, potassium borate, ammonium borate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium carbonate, Inorganic alkaline agents such as potassium carbonate, ammonium carbonate, dibasic sodium phosphate, dibasic potassium phosphate, dibasic ammonium phosphate, trisodium phosphate, tribasic potassium phosphate and tribasic ammonium phosphate, monomethylamine , Dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine , Monoisopropanolamine, diisopropanolamine, triisopropanolamine, N-ethylethanolimine, Nn-butylethanolamine, Nt-butylethanolamine, Nn-butyldiethanolamine, Nt-butyldiethanolamine N-methylethanolamine, N-methyldiethanolamine, N-aminoethylethanolamine, N-aminoethylpropanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. Examples include organic alkali agents, alkali metal silicates such as sodium silicate, potassium silicate and lithium silicate, and ammonium silicate. These can be used alone or in combination of two or more.

  The developer used in the present invention can be used in combination with other various surfactants, and examples thereof include anionic, cationic, nonionic and amphoteric surfactants. These surfactants used in combination are added to the developer in the range of 0.001 to 10% by mass, more preferably 0.01 to 5% by mass.

  Various development stabilizers can be used in the developer used in the present invention. Preferred examples thereof include polyethylene glycol adducts of sugar alcohols described in JP-A-6-282079, phosphonium salts such as tetrabutylphosphonium bromide, and iodonium salts such as diphenyliodonium chloride. Furthermore, anionic surfactants or amphoteric surfactants described in JP-A-50-51324, water-soluble cationic polymers described in JP-A-55-95946, and JP-A-56-142528 are described. There are water-soluble amphoteric polyelectrolytes that have been described. Further, an organic boron compound to which an alkylene glycol is added as described in JP-A No. 59-84241, a polyethylene glycol having a weight average molecular weight of 300 or more as described in JP-A No. 61-215554, and a cation as described in JP-A No. 63-175858. And a fluorine-containing surfactant having a functional group, a water-soluble ethylene oxide adduct obtained by adding 4 mol or more of an acid or an alcohol or an alcohol disclosed in JP-A-2-39157, and a water-soluble polyalkylene compound.

  It is advantageous in terms of transportation that the developer used in the present invention is a concentrated solution in which the water content is less than that in use, and is diluted with water at the time of 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 about concentrate: water = 1: 0 to 1:10. In addition, since the container is alkaline, it is preferable to use a material that does not permeate carbon dioxide and that does not break during transportation for safety. Usually, a resin container such as a hard bottle or a cubicener is preferably used.

  In the processing method of the present invention, the processing is performed with a normal automatic processor after exposure. The automatic developing machine is generally composed of a developing unit and a post-processing unit, and includes an apparatus for transporting the printing plate, each processing liquid tank and a spray tank, and is assembled by a pump while horizontally transporting the exposed printing plate. Each processing solution is sprayed from a spray nozzle to develop and post-process. Recently, a developing method has been developed in which a printing plate is dipped and conveyed by a submerged guide roll in a developing tank filled with a developing solution, and such a developing method can also be suitably applied to the present invention. . Such an automatic developer can be processed while replenishing the replenisher according to the development processing amount, operating time, and the like.

  The printing plate developed with the developer having such a composition is subjected to post-processing with a washing water, a rinse solution containing a surfactant, a finisher mainly composed of gum arabic or starch derivatives, or a protective gum solution. The In the post-treatment of the printing plate of the present invention, these treatments can be used in various combinations. For example, development → water washing → rinsing liquid treatment containing surfactant or development → water washing → finisher liquid treatment is a rinse liquid or finisher. Less liquid fatigue is preferable. Furthermore, a countercurrent multistage process using a rinse liquid or a finisher liquid is also a preferred embodiment. These post-processing are generally performed using an automatic developing machine including a developing unit and a post-processing unit. As the post-treatment liquid, a method of spraying from a spray nozzle or a method of conveying through a treatment tank filled with the treatment liquid is used. A method is also known in which a small amount of aqueous water is supplied to the plate surface after development and washed with water, and the waste solution is reused as dilution water for the developer stock solution. In such automatic processing, each processing solution can be processed while being replenished with the respective replenishing solution according to the processing amount and operating time. In addition, a so-called disposable processing method in which treatment is performed with a substantially unused post-treatment liquid can also be applied. The planographic printing plate obtained by such processing is loaded on an offset printing machine and used for printing.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples as well as the effects. The part in an Example shows a mass part.

<Preparation of planographic printing plate A of the present invention>
An aluminum plate having a width of 1030 mm and a thickness of 0.24 mm and having an alloy composition of A1050 type is immersed in an aqueous solution of 2 mass% -sodium hydroxide for 30 seconds at 25 ° C., then washed with water, and using an aqueous suspension of nylon brush and palmiston. Brush polishing, washing with water, dipping in a 2% by mass-sodium hydroxide aqueous solution for 30 seconds and washing with water. This was immersed in an indirect power supply type electrolytic cell filled with a mixture of 1% by mass hydrochloric acid and 0.5% by mass of acetic acid at 30 ° C., roughened by AC electrolysis at 12 V, 450 coulomb / dm ² , and washed with water. Then, it is immersed in a 2% by weight-sodium hydroxide aqueous solution at 25 ° C. for 30 seconds, desmutted, washed with water, further anodized using a 30 ° C., 25% by weight-sulfuric acid aqueous solution, washed with water and dried. An aluminum support was prepared.

The surface of the aluminum support was observed at a magnification of 50,000 using a scanning electron microscope. As a result, fine pits having an opening diameter of 0.02 to 0.3 μm per 1 mm ² were observed on the surface of the aluminum plate. There were 6.8 × 10 ⁷ pieces, and when the average opening area A of the minute pits having an opening diameter of 0.02 to 0.3 μm was determined, it was 1.5 × 10 ⁻⁸ mm ² . When 1 / (A × 2) was determined, it was 3.3 × 10 ⁷ pieces, and it was confirmed that this aluminum support satisfied the above-mentioned formula 1.

  A coating solution for the photosensitive layer according to the following formulation was prepared as shown in Table 1, and coated on the aluminum support so that the dry film thickness was 3 μm. Thus, the planographic printing plate A of the present invention was prepared.

<Coating solution for photosensitive layer>
Polymer (P-1; mass average molecular weight of about 90,000) 30 parts 1,3-dioxolane as a solvent for polymer 70 parts Polymerization initiator (BC-5) 4 parts
(BS-1) 2 parts Polymerizable monomer (C-5) 15 parts Pentaerythritol tetraacrylate 10 parts Sensitizing dye (S-33) 0.4 part Polymerization inhibitor 2,6-di-t-butylcresol 0. 2 parts Solvents listed in Table 1 (parts)
4 parts of carbon black with an average particle size of 185 nm

<Preparation of comparative planographic printing plate B>
A comparative lithographic printing plate B was prepared in the same manner as the aluminum support of the lithographic printing plate A except that the desmut temperature was set to 40 ° C. From this aluminum support, fine pits having an opening diameter of 0.02 to 0.3 μm were not observed. Therefore, the aluminum support is not an object of the present invention.

<Preparation of comparative planographic printing plate C>
A comparative lithographic printing plate C was prepared in the same manner as in the above aluminum support of the lithographic printing plate A except that the desmut temperature was set to 30 ° C. The aluminum support has 7.3 × 10 ⁶ micro pits having an opening diameter of 0.02 to 0.3 μm per 1 mm ² , and the micro pits having an opening diameter of 0.02 to 0.3 μm are present. The average opening area A was determined to be 2.0 × 10 ⁻⁸ mm ² . When 1 / (A × 2) was determined, it was 2.5 × 10 ⁶ , and it was confirmed that this aluminum support did not satisfy the formula 1.

<Preparation of comparative planographic printing plate D>
A comparative lithographic printing plate D was prepared in the same manner as in the above aluminum support of the lithographic printing plate A except that the electrolytic surface roughening conditions were 24 V and 950 coulomb / dm ² . From this aluminum support, fine pits having an opening diameter of 0.02 to 0.3 μm were not observed. Therefore, the aluminum support is not an object of the present invention.

<Preparation of planographic printing plate E of the present invention>
In the aluminum support of the above lithographic printing plate B, the lithographic printing plate of the present invention was prepared in the same manner as that described above except that after anodizing treatment and further immersed in hot water at 95 ° C. for 1 minute, washed and dried to prepare an aluminum support. Printing plate E was produced. The aluminum support has 4.5 × 10 ⁸ micro pits having an opening diameter of 0.02 to 0.3 μm per 1 mm ² , and the micro pits having an opening diameter of 0.02 to 0.3 μm are present. The average opening area A was 2.2 × 10 ⁻⁹ mm ² . When 1 / (A × 2) was determined, it was 2.3 × 10 ⁸ pieces, and it was confirmed that this aluminum support satisfied the above-mentioned formula 1.

<Preparation of planographic printing plate F of the present invention>
In the aluminum support of the lithographic printing plate B, a lithographic printing plate F of the present invention was produced in the same manner except that a mixed solution of 25% by mass-sulfuric acid and 5% -mass% phosphoric acid was used as the anodizing solution. . The aluminum support has 1.7 × 10 ⁹ micro pits having an opening diameter of 0.02 to 0.3 μm per 1 mm ² , and the micro pits having an opening diameter of 0.02 to 0.3 μm are present. The average opening area A was 5.9 × 10 ⁻¹⁰ mm ² . When 1 / (A × 2) was determined, it was 8.5 × 10 ⁸ , and it was confirmed that this aluminum support satisfied the above formula 1.

Each prepared lithographic printing plate was subjected to drum rotation speed 1000 rpm resolution 2400 dpi, laser irradiation energy 100 mJ / mm using an external drum type plate setter (PT-R4000 manufactured by Dainippon Screen Mfg. Co., Ltd.) equipped with an 830 nm semiconductor laser. The print test chart image was exposed under the condition of cm ² . After the exposure, Dainippon Screen Mfg. Co., Ltd. PS plate automatic developing machine PD-1310 was used as an automatic developing machine, and the following developing solution was used to carry out a developing process at a liquid temperature of 30 ° C. for 15 seconds, followed by Then, a gum solution having the following formulation was applied.

<Developer>
35% sodium alkylnaphthalene sulfonate
(Surfactant manufactured by Kao Corporation) 30g
KOH 25g
20% potassium silicate aqueous solution (containing 20% SiO ₂ ) 50 g
N-aminoethylethanolamine 30g
1L with water

<Gum solution>
1g potassium phosphate 5g
Gum arabic 25g
Dehydroacetic acid 0.5g
EDTA2Na 1g
1L with water

  The lithographic printing plates A to E produced as described above were evaluated for dissolution properties, image loss after development, and printing durability. For the printing durability test, the printing press uses Heidelberg TOK (trademark of Heidelberg offset printing press), the ink is BEST ONE black H (manufactured by T & KTOKA), and the fountain solution is Astro Mark III (stock) A 1% aqueous solution of a dampening solution manufactured by Nikken Chemical Laboratory was used, and each result was evaluated according to the following evaluation criteria.

Elution: ○: No photosensitive layer remains in the non-image area. Δ: A slight photosensitive layer remains in the non-image area. X: A photosensitive layer remains in the non-image area.

Image missing state ○: Image is not missing at all ×: Image is missing

Printing durability ○: 200,000 sheets or more ×: 50,000 sheets or less (including original missing images)

  In the above development processing, the elution property of the non-image area, the missing state of the image after development, and the printing durability were evaluated in the same manner except that the processing was performed at 30 ° C. for 15 seconds to 30 ° C. for 40 seconds. Each result is shown to Tables 1-3.

  From the above results, the comparative lithographic printing plates B, C, and D exhibited good non-image area elution in 30 ° C. and 15 seconds development, no image was lost, and sufficient printing durability was shown. In the development process at 30 ° C. for 40 seconds, an image is missing. On the other hand, the lithographic printing plates A, E, and F of the present invention have a good elution property in the non-image area, no image loss, and sufficient printing durability in both the development processing at 30 ° C. for 15 seconds and 30 ° C. for 40 seconds. Sex was obtained.

  From the above results, it can be seen that the planographic printing plate of the present invention has a wide development latitude and exhibits good printing durability.

Claims (1)

A negative photosensitivity for laser exposure, in which a polymer having a polymerizable vinylphenyl group in the side chain and a carboxyl group-containing monomer as a copolymerization component and a photosensitive layer containing at least a polymerization initiator are provided on an aluminum support. In the planographic printing plate, fine pits having an opening diameter of 0.02 to 0.3 μm are formed on the surface of the aluminum support, and the number of the fine pits per unit area satisfies the following formula 1. A negative photosensitive lithographic printing plate for laser exposure.
N> 1 / (A × 2) (Formula 1)
In the formula, N represents the number of minute pits having an opening diameter of 0.02 to 0.3 μm per 1 mm ² , and A represents an average opening area (mm ² ) of minute pits having an opening diameter of 0.02 to 0.3 μm. Represents.