JP4299199B2 - Negative photosensitive lithographic printing plate - Google Patents

Description

  The present invention relates to a negative photosensitive lithographic printing plate having a photopolymerizable photosensitive layer on an aluminum plate.

  Conventionally, a negative type lithographic printing plate using a diazo resin or the like is provided with a photosensitive layer on an aluminum plate which has been subjected to a silicate treatment in advance, and an alkaline developer having a relatively low pH (generally pH is 12 or less) after UV exposure. Development has been carried out. In such a processing method with a low pH developer, compared with a processing method with a high pH developer generally containing a silicate that is carried out in a positive type, alkali erosion of the image area during development is less likely to occur, As a printing plate, because it has good ink fillability and high printing durability, it has been actively used in newspaper printing, particularly where high printing durability is required, and in the business form printing field using ultraviolet curable ink.

  On the other hand, in recent years, computer-to-plate (CTP) technology has been developed to output directly on a printing plate without outputting it on film based on digital data created on a computer, and various types equipped with various lasers as output machines. Plate setters and photosensitive lithographic printing plates compatible with these have been actively developed. In particular, in an output device using a semiconductor laser or a YAG laser that emits light in the near infrared region of 750 nm or more, a high-power laser with a light source output of several hundreds mW to several watts is mounted, so the energy is extremely high. Image formation is possible. Such a photosensitive lithographic printing plate compatible with CTP cannot be used in the system using the above-mentioned conventional type diazo resin because the sensitivity is still insufficient. As an alternative system, for example, JP-A-7-20629 is disclosed. Potential acid generators, as described in JP-A-7-271029, JP-A-9-185160, JP-A-9-197671, JP-A-9-222731, JP-A-9-239945, JP-A-10-142780, etc. Of latent acid generators using the heat generated by photothermal conversion in the combination of UV and near-infrared absorbing dyes, and negative-type image formation using acid-catalyzed thermal crosslinking using the acid generated in this laser irradiation part A method is disclosed. Alternatively, as a system in which photon mode recording, which is an application of conventional high-sensitivity photopolymer technology, is applied to near-infrared light, for example, JP-A Nos. 2000-122274, 2000-131833, 2000-181559, 2000 No. 194124 discloses a negative type with high sensitivity by using various dyes that spectrally sensitize the photopolymerization initiator in near infrared light in a photopolymer system containing a photopolymerization initiator and an ethylenically unsaturated compound. Recording material is given.

  In particular, Japanese Patent Application Laid-Open Nos. 2001-290271 (Patent Document 1) and 2002-278066 (Patent Document 2) use a polymer having an ethylenic double bond in the side chain in the photosensitive layer, thereby achieving high sensitivity. In addition, examples of printing plates compatible with CTP having excellent printing durability are disclosed. However, as a developer used for these, JP 2002-278083 (Patent Document 3), 2002 278084, JP 2002-278085 A (Patent Document 4) and the like describe that a highly alkaline developer having a pH exceeding 12 is used.

  In the various systems described above, when an aluminum plate subjected to silicate treatment is used as an aluminum support, as in the case of diazo resin, the adhesion between the photosensitive layer and the aluminum support is poor, and development Since the image part that is the exposed part is lost during processing, or when printing is performed after development, there is a problem that printing durability is poor, so it is necessary to use an aluminum plate that is not subjected to silicate processing. There wasn't.

  The silicate treatment on the aluminum surface is a preferred treatment for improving the water retention of the non-image area in offset printing and preventing the occurrence of background stains. However, for various photosensitive lithographic printing plates corresponding to the near-infrared laser beam as described above, it is difficult to use a silicate-treated aluminum plate for the above-mentioned reason, so that silicate treatment is performed during development processing. Specifically, it was necessary to introduce a silicate into the developer, and to develop at a high pH. When treated with a high pH developer containing such a silicate, problems such as ink fillability and printing durability tend to occur, and problems such as being unsuitable for printing using UV curable inks occur. did.

  Further, as another problem when using a high pH developer, generally, in a developer having a pH of 12 or more, there is a problem that the developability deteriorates because the pH decreases with time due to absorption of carbon dioxide in the atmosphere. In order to compensate for this, it is necessary to frequently replenish the developer. Furthermore, since the developer having such a high pH is extremely dangerous and harmful, special care must be taken in handling, storage and transportation.

On the other hand, using a silicate-treated aluminum plate as a support for a negative photosensitive lithographic printing plate for near infrared laser is disclosed in JP-A Nos. 2001-272787 (Patent Document 5) and 2003-114532 ( Patent Document 6). However, these techniques require a new intermediate layer containing an aluminum compound or a silicone compound in order to improve the adhesion between the silicate film and the photosensitive layer. The conventional silicate processing is generally performed at a high temperature of 70 ° C. or higher using sodium silicate. In the silicate processing using such sodium silicate, the photosensitive layer of the present invention and aluminum are used. Strong adhesion to the plate cannot be obtained.
JP 2001-290271 A JP 2002-278066 A JP 2002-278083 A JP 2002-278085 A JP 2001-272787 A JP 2003-114532 A

  Accordingly, an object of the present invention is to provide a negative photosensitive lithographic printing plate in which the adhesion between the aluminum plate and the photosensitive layer is strong, the printing durability is high, and the non-image area is not stained. The present invention provides a negative photosensitive lithographic printing plate having high printing durability without providing an intermediate layer or the like. Further, it can be processed with a developer having a relatively low pH of pH 12 or less, and stains can be prevented. The present invention provides a negative photosensitive lithographic printing plate that does not occur.

The above object of the present invention has been basically achieved by the following invention.
Explicitly pole oxidized aluminum plate, a polymer having an ethylenic double bond in a side chain, a monomer or oligomer having two or more ethylenic double bonds in the molecule, a photopolymerization initiator, and near visible light In a negative photosensitive lithographic printing plate having a photosensitive layer containing a sensitizer having absorption in an infrared wavelength region, the aluminum plate contains potassium silicate after anodization and contains SiO ₂ / M _2. O (M represents an alkali metal) vinyl in der is, the polymer is a side chain containing an ethylenic double bond in the side chain which molar ratio is processed with a processing solution in the 0.5 to 3.5 of A photosensitive lithographic printing plate which is a polymer having a phenyl group .

  According to the present invention, the printing durability of a negative photosensitive lithographic printing plate for near-infrared laser can be improved, and the scumming of non-image areas can be improved. In addition, development processing can be performed at a relatively low pH of 12 or less. In addition, productivity is improved because there is no need to provide an intermediate layer or the like.

  Hereinafter, the present invention will be described in detail. The photosensitive layer of the present invention contains at least a polymer having an ethylenic double bond in the side chain as a polymer. Such ethylenic double bonds include vinyl groups, allyl groups, and vinylphenyl groups.

  Examples of the monomer having a vinyl group and an allyl group include vinyl (meth) acrylate, vinyl (meth) acrylamide, allyl (meth) acrylate, allyl (meth) acrylamide, and the like. A copolymer is used.

  The polymer having a vinylphenyl group in the side chain is a polymer having a group represented by the following general formula in the side chain. In the present invention, a polymer having a vinylphenyl group in the side chain is particularly preferably used.

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 represents 0 or 1, m ₁ represents an integer of 0 to 4, and k ₁ represents an integer of ₁ to 4.

The chemical formula 1 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 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.). Further, the linking group Z ₁ preferably includes a heterocyclic ring, and k ₁ is preferably 1 or 2.

  The polymer having a group as shown in the above example is preferably soluble in an alkaline aqueous solution, and therefore a polymer containing a carboxyl group-containing monomer as a copolymerization component is particularly preferable. In this case, the ratio of the group represented by Chemical Formula 1 in the copolymer composition is preferably 1% by mass or more and 95% by mass or less in the total composition of 100% by mass. The range of 5-95 mass% is more preferable, and the range of 10-90 mass% is more preferable. Similarly, the proportion of the carboxyl group-containing monomer in the copolymer is preferably 5% by mass or more and 99% by mass or less, and more preferably in the range of 10 to 90% by mass. If the ratio is less than this, the copolymer may not be dissolved in the alkaline aqueous solution.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, acrylic acid 2-carboxyethyl ester, methacrylic acid 2-carboxyethyl ester, crotonic acid, maleic acid, fumaric acid, maleic acid monoalkyl ester, and fumaric acid monoalkyl. Examples include esters, 4-carboxystyrene and the like.

  The polymer used in the present invention is synthesized as a multi-component copolymer by introducing other monomer components into the copolymer in addition to the monomer having an ethylenic double bond in the side chain and the monomer having a carboxyl group. , It can also be preferably used. In such cases, monomers that can be incorporated into the copolymer include styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-carboxystyrene, 4-aminostyrene, chloromethylstyrene, and 4-methoxystyrene. Styrene derivatives such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, methacrylic acid alkyl esters such as dodecyl methacrylate, phenyl methacrylate, benzyl methacrylate, etc. Methacrylic acid aryl ester or alkyl aryl ester, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methoxydiethylene glycol monomethacrylate Asteryl, methacrylic acid methoxypolyethylene glycol monoester, methacrylic acid ester having alkyleneoxy group such as methacrylic acid polypropylene glycol monoester, amino group-containing methacrylic acid ester such as 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate Or the same examples as the corresponding methacrylic acid esters as acrylic esters, or vinylphosphonic acid as a monomer having a phosphoric acid group, amino group-containing monomers such as allylamine and diallylamine, or vinylsulfonic acid And salts thereof, allylsulfonic acid and salts thereof, methallylsulfonic acid and salts thereof, styrenesulfonic acid and salts thereof, 2-acrylamido-2-methylpropanesulfonic acid and Monomers having a sulfonic acid group such as a salt of, monomers having a nitrogen-containing heterocycle such as 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazole, N-vinylcarbazole, or monomers having a quaternary ammonium base 4-vinylbenzyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, quaternized product of dimethylaminopropylacrylamide with methyl chloride, quaternized product of N-vinylimidazole with methyl chloride, 4-vinyl Benzylpyridinium chloride, etc., or acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, dimethylacrylamide, diethylamine Acrylamide or methacrylamide derivatives such as chloramide, N-isopropylacrylamide, diacetone acrylamide, N-methylol acrylamide, N-methoxyethyl acrylamide, 4-hydroxyphenyl acrylamide, acrylonitrile, methacrylonitrile, phenylmaleimide, hydroxyphenylmaleimide, Vinyl acetates such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl benzoate, vinyl ethers such as methyl vinyl ether, butyl vinyl ether, others, N-vinyl pyrrolidone, acryloyl morpholine, tetrahydrofur Furyl methacrylate, vinyl chloride, vinylidene chloride, allyl alcohol, vinyl trimethoxysilane It may be used glycidyl methacrylate and various monomers as arbitrary copolymerization monomers. The proportion of these monomers in the copolymer may be any as long as the preferred proportion of the group and carboxyl group-containing monomer represented by Chemical Formula 1 in the copolymer composition described above is maintained. It can be introduced at a rate.

  The molecular weight of the polymer used in the present invention is preferably in the range of 1,000 to 1,000,000, more preferably in the range of 10,000 to 300,000 in terms of weight average molecular weight.

  Examples of the polymer having a vinylphenyl group in the side chain according to the present invention are shown below. In the formula, the number represents the mass% of each repeating unit in the copolymer total composition of 100 mass%.

  The photosensitive layer of the present invention contains a monomer or oligomer having two or more ethylenic double bonds. The molecular weight of the monomer or oligomer is 10,000 or less, preferably 5000 or less. Examples of the compound include compounds having two or more ethylenic double bonds such as acryloyl group, methacryloyl group, and vinylphenyl group.

  Examples of the monomer or oligomer having an acryloyl group or a methacryloyl group as an ethylenic double bond include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, tetraethylene glycol di (meth) acrylate, trisacryloyloxyethyl isocyanurate, tripropylene glycol di (meth) acrylate, ethylene glycol glycerol tri (meth) acrylate, glycerol epoxy tri (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate, trimethylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra ( Data) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pyrogallol triacrylate.

  A monomer or oligomer having a vinylphenyl group as an ethylenic double bond 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.

The above general formula will be described in more detail. As the linking group for Z ₂ , 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, or a group in which two or more are combined. Here, R ₅ and R ₆ represent a hydrogen atom, an alkyl group, an aryl group, or the like. Furthermore, the above 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 above general formula, 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 having 2-10. Although a specific example is shown below, it is not limited to these examples.

  The content of the monomer or oligomer as described above is preferably in the range of 1 to 100% by mass and more preferably in the range of 5 to 50% by mass with respect to the polymer having an ethylenic double bond in the side chain.

  The photosensitive layer of the present invention contains a photopolymerization initiator. Known compounds can be used as the photopolymerization initiator. For example, organic boron salts, trihaloalkyl-substituted compounds (for example, s-triazine compounds and oxadiazole derivatives as trihaloalkyl-substituted nitrogen-containing heterocyclic compounds, trihaloalkylsulfonyl compounds), hexaarylbisimidazoles, titanocene compounds, ketoximes Examples thereof include compounds, thio compounds, and organic peroxides. Among these photopolymerization initiators, organic boron salts and trihaloalkyl-substituted compounds are particularly preferably used. More preferably, an organic boron salt and a trihaloalkyl-substituted compound are used in combination.

  The organic boron anion constituting the organic boron salt is represented by the following general formula.

In the formula, each of R ₁₁ , R ₁₂ , R ₁₃ and R ₁₄ may be the same or different, and represents an alkyl group, aryl group, aralkyl group, alkenyl group, alkynyl group, cycloalkyl group or heterocyclic group. To express. 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.

  Examples of the cation constituting the organic boron salt include alkali metal ions and onium compounds, and preferred are onium salts such as ammonium salts such as tetraalkylammonium salts, sulfonium salts such as triarylsulfonium salts, and triaryls. Examples thereof include phosphonium salts such as alkylphosphonium salts. Examples of particularly preferred organic boron salts are shown below.

  Other preferred photopolymerization initiators include trihaloalkyl-substituted compounds. Specifically, the trihaloalkyl-substituted compound is a compound having at least one trihaloalkyl group such as a trichloromethyl group or a tribromomethyl group in the molecule. As a preferable example, the trihaloalkyl group is a nitrogen-containing complex. Examples of the compound bonded to the ring group include s-triazine derivatives and oxadiazole derivatives, or trihaloalkylsulfonyl compounds in which the trihaloalkyl group is bonded to an aromatic ring or a nitrogen-containing heterocycle via a sulfonyl group. .

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

  The content of the photopolymerization initiator as described above is preferably in the range of 1 to 100% by mass and more preferably in the range of 1 to 40% by mass with respect to the polymer.

  The photosensitive layer of the present invention has absorption in the wavelength region from visible light to near infrared light so as to be compatible with various light sources from visible light to near infrared light, and is a sensitizer that sensitizes the aforementioned photopolymerization initiator. Contains a sensitizer. As the sensitizer, various sensitizing dyes are preferably used. Such sensitizing dyes include 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, styryl, squarylium compound, pyrylium compound, and further described in European Patent No. 0,568,993, US Pat. Nos. 4,508,811, and 5,227,227. Compounds can also be used.

  The photosensitive lithographic printing plate of the present invention preferably contains a sensitizing dye having absorption in near infrared light of 750 nm or more so as to correspond to a near infrared laser. By handling the photosensitive layer with scanning exposure using near-infrared to infrared light (750 to 1100 nm wavelength region) laser light, it is possible to handle it in a bright room (under a fluorescent light-cut fluorescent lamp). It becomes. Specific examples of sensitizing dyes used for sensitizing the photosensitive layer to such near infrared light are shown below.

In recent years, output machines equipped with a blue semiconductor laser having an oscillation wavelength of 400 to 430 nm have become widespread. This output machine has a maximum exposure energy amount of about several tens of μJ / cm ² , and the photosensitive material used is required to have high sensitivity. As a sensitizer for dealing with a blue semiconductor laser, a pyrylium compound or a thiopyrylium compound is preferable.

In the present invention, the content of the sensitizer is suitably about 3 to 300 mg per 1 m ² of the photosensitive lithographic printing plate. Preferably it is 10-200 mg / m < ² >.

  The photosensitive layer of the present invention preferably further contains a compound having a urethane bond and an ethylenic double bond (hereinafter referred to as a urethane compound). By containing the urethane compound, the elution property of the non-image area of the photosensitive layer is improved, and the background stain of the non-image area is further improved. The urethane compound in the present invention has at least one urethane bond represented by the following general formula in the molecule. Moreover, as an ethylenic double bond, an acryloyl group and a methacryloyl group are mentioned, It is preferable to have two or more of these ethylenic double bonds. Furthermore, a compound having 2 or more urethane bonds and 3 or more ethylenic double bonds is preferred.

  Specific examples of the urethane compound described above are shown below.

  In the present invention, the content of the urethane compound is preferably 5 to 60% by mass, particularly 10 to 50% by mass with respect to the polymer having an ethylenic double bond in the side chain described above. A range is preferred.

  In the photosensitive layer of the present invention, other components may be preferably added for various purposes in addition to the components described above. For example, it is preferable to add various polymerization inhibitors for the purpose of improving storage stability. As the polymerization inhibitor in this case, compounds having various phenolic hydroxyl groups such as hydroquinones, catechols, naphthols, and cresols, quinone compounds, and the like are preferably used, and hydroquinone is particularly preferably used. In this case, the polymerization inhibitor is preferably added in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer.

  In addition, various dyes and pigments are added as elements constituting the photosensitive layer for the purpose of enhancing the visibility of the image, and inorganic fine particles or organic fine particles are added for the purpose of preventing blocking of the photosensitive composition. This is also preferably done.

  The thickness of the photosensitive layer as a lithographic printing plate is preferably formed on an aluminum plate with a dry thickness in the range of 0.5 to 10 microns, and more preferably in the range of 1 to 5 microns. It is extremely preferable for a significant improvement. The photosensitive layer is coated and dried on the support using various known coating methods.

  The photosensitive lithographic printing plate of the present invention uses an aluminum plate as a support. The thickness of the aluminum plate used in the present invention is about 0.1 to 0.6 mm. This thickness can be appropriately changed according to the size of the printing press, the size of the printing plate, and the user's desire.

  The aluminum plate is usually grained to a more preferable shape. Examples of the graining method include mechanical graining (mechanical surface roughening), chemical etching, and electrolytic grain as disclosed in JP-A-56-28893. In addition, electrochemical graining (electrochemical roughening, electrolytic graining), which is electrochemically grained in hydrochloric acid electrolyte or nitric acid electrolyte, or the aluminum surface is scratched with metal wire Mechanical graining methods (mechanical roughening treatment) such as brush grain method, ball grain method to grain the aluminum surface with abrasive balls and abrasives, brush grain method to grain the surface with nylon brush and abrasives, etc. Can be used. These graining methods can be used alone or in combination. For example, a combination of a mechanical surface roughening treatment with a nylon brush and an abrasive and an electrolytic surface roughening treatment with a hydrochloric acid electrolytic solution or a nitric acid electrolytic solution, or a combination of a plurality of electrolytic surface roughening treatments may be mentioned.

  In the case of the brush grain method, the long wavelength component on the surface of the aluminum plate can be selected by appropriately selecting conditions such as the average particle size, maximum particle size, bristle diameter, density, and indentation pressure of the particles used as the abrasive. The average depth of the recesses can be controlled. The recesses obtained by the brush grain method preferably have an average wavelength of 3 to 15 μm and an average depth of 0.3 to 1 μm.

As the electrochemical surface roughening method, an electrochemical method in which graining is chemically performed in a hydrochloric acid electrolytic solution or a nitric acid electrolytic solution is preferable. A preferable current density is 50 to 400 C / dm ² in terms of electricity at the time of anode. More specifically, for example, in an electrolytic solution containing 0.1 to 50% by mass of hydrochloric acid or nitric acid, under conditions of a temperature of 20 to 100 ° C., a time of 1 second to 30 minutes, and a current density of 100 to 400 C / dm ² . This is done using direct current or alternating current. According to the electrolytic surface-roughening treatment, it is easy to impart fine irregularities to the surface, which is suitable for improving the adhesion between the photosensitive layer and the aluminum plate.

  By electrochemical surface roughening after mechanical surface roughening, crater-like or honeycomb-like pits having an average diameter of about 0.3 to 1.5 μm and an average depth of 0.05 to 0.4 μm are formed on an aluminum plate. It can be made to produce on the surface of 80-100% of area ratio. In the case where only the electrochemical surface roughening method is performed without performing the mechanical surface roughening method, the average pit depth is preferably less than 0.3 μm. The provided pits have the effect of improving the resistance to contamination of the non-image area of the printing plate and the printing durability. In the electrolytic surface roughening treatment, an amount of electricity necessary for providing sufficient pits on the surface, that is, the product of the current and the time during which the current flows is an important condition. From the viewpoint of energy saving, it is desirable that sufficient pits can be formed with a smaller amount of electricity. The surface roughness after the roughening treatment is such that the arithmetic average roughness (Ra) measured at a cut-off value of 0.8 mm and an evaluation length of 3.0 mm in accordance with JIS B0601-1994 is 0.2-0. It is preferably 5 μm.

  The grained aluminum plate is preferably subjected to chemical etching. As the chemical etching treatment, acid etching or alkali etching is known, and a chemical etching treatment using an alkaline solution is a particularly excellent method in terms of etching efficiency.

The alkali agent suitably used is not particularly limited, and examples thereof include caustic soda, sodium carbonate, sodium aluminate, sodium metasilicate, sodium phosphate, potassium hydroxide, and lithium hydroxide. The alkaline etching treatment is preferably performed under such a condition that the dissolved amount of Al is 0.05 to 1.0 g / m ² . The other conditions are not particularly limited, but the alkali concentration is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, and the alkali temperature is 20 to 100 ° C. It is preferable that it is, and it is more preferable that it is 30-50 degreeC. The alkali etching treatment is not limited to one method, and a plurality of steps can be combined. In the present invention, an alkali etching treatment can be performed after the mechanical roughening treatment and before the electrochemical roughening treatment. In this case, the dissolution amount of Al is preferably 0.05 to 30 g / m ² .

  After performing the alkali etching treatment, pickling is performed to remove dirt (smut) remaining on the surface. Examples of the acid used include nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrofluoric acid, and borohydrofluoric acid. In particular, as a method for removing smut after the electrolytic surface-roughening treatment, it is preferably brought into contact with 15 to 65 mass% sulfuric acid at a temperature of 50 to 90 ° C. as described in JP-A-53-12739. A method is mentioned.

  Moreover, when performing a chemical etching process with an acidic solution, the acid used for an acidic solution is not specifically limited, For example, a sulfuric acid, nitric acid, and hydrochloric acid are mentioned. The concentration of the acidic solution is preferably 1 to 50% by mass. Moreover, it is preferable that the temperature of an acidic solution is 20-80 degreeC.

  The aluminum plate treated as described above is further subjected to anodizing treatment. The anodizing treatment can be performed by a method conventionally used in this field. Specifically, when direct current or alternating current is applied to an aluminum plate in an aqueous solution or non-aqueous solution of sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, etc., alone or in combination of two or more. An anodized film can be formed on the surface of the aluminum plate.

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, is suitably an electrolysis time of 10 to 200 seconds. Among these anodizing treatments, the method of anodizing at a high current density in a sulfuric acid electrolyte solution described in British Patent 1,412,768 is particularly preferable.

In the present invention, the amount of anodized layer is preferably from 1 to 10 g / m ^2, and more preferably from 1.5~7g / m ^2, particularly preferably from 2-5 g / m ² . After the roughening treatment, an alkali etching treatment can be performed before the electrochemical roughening treatment. In this case, the dissolution amount of Al is preferably 0.05 to 30 g / m ² .

The aluminum plate of the present invention is treated with a treatment solution containing potassium silicate after the anodizing treatment. The treatment liquid used for such treatment contains potassium silicate, and the molar ratio of SiO ₂ / M ₂ O (M represents an alkali metal) is in the range of 0.5 to 3.5. A preferred molar ratio of SiO ₂ / M ₂ O is 0.8 to 3.0, more preferably 1.0 to 2.5, and still more preferably 1.0 to 2.2.

M of SiO ₂ / M ₂ O The above represents an alkali metal, the treatment liquid of the present invention contains a potassium silicate, containing at least potassium as the alkali metal (M). As the alkali metal (M), sodium or lithium may be contained. In the present invention, 50 mol% or more of the alkali metal (M) is preferably potassium, and 70 mol% or more is potassium. Is more preferable, and further 100 mol% is preferably potassium.

The concentration of the silicate in the treatment liquid is preferably in the range of 0.5 to 10% by mass in terms of SiO ₂ , more preferably in the range of 0.8 to 8% by mass, and further preferably in the range of 1 to 6% by mass. .

  It is preferable to add an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide or lithium hydroxide to the treatment liquid. The concentration of the alkali metal hydroxide in the treatment liquid is 0.5 to 5 mass. % Range is preferable, and the range of 1-4 mass% is preferable. Of the alkali metal hydroxides, potassium hydroxide is particularly preferable, and the concentration of potassium hydroxide in the treatment liquid is preferably in the range of 0.5 to 5% by mass, and more preferably in the range of 1 to 4% by mass. Further, the pH at 25 ° C. of the treatment liquid is preferably 12 or more, more preferably 12 to 13.5, and particularly preferably 12.3 to 13.3.

  The temperature of the treatment liquid when treating with the treatment liquid containing potassium silicate described above can be treated at about 5 to 80 ° C., preferably 65 ° C. or less, more preferably 50 ° C. or less, and further 45 degrees C or less is preferable. For the treatment time, for example, the time for immersing the aluminum plate in the treatment liquid is preferably 1 to 60 seconds, and particularly preferably 3 to 50 seconds.

The above-described treatment with the potassium silicate solution of the present invention is a conventional silicate treatment, that is, a treatment method for forming a silicate film on an anodized aluminum plate treated with sodium silicate at a high temperature of 70 ° C. or higher. On the other hand, a microprojection structure is formed on the surface of the aluminum plate, whereby the hydrophilicity of the non-image area can be improved while maintaining the adhesion between the photosensitive layer and the surface of the aluminum plate. In the treatment liquid of the present invention, if the molar ratio of SiO ₂ / M ₂ O becomes too small, corrosion of the aluminum surface becomes severe and water retention deteriorates. Conversely, if the molar ratio becomes too large, a minute protrusion structure is formed on the aluminum surface. Strong adhesion cannot be obtained without being formed.

  As described above, by combining the aluminum plate treated with the present invention and the photosensitive layer of the present invention, strong adhesiveness can be obtained without providing an intermediate layer or the like.

  After the treatment with the potassium silicate solution described above, a water washing treatment is performed. The method of washing with water is not particularly limited, and examples thereof include a spray method and a dipping method. These may be used alone or in combination, or may be used in combination of two or more. The time for the water washing treatment is not particularly limited.

  In the present invention, after anodization, before the treatment with the potassium silicate solution, it is preferable to perform a sealing treatment with water vapor or hot water of 60 ° C. or higher. The sealing treatment conditions with water vapor or hot water can be performed according to a conventional method. By combining this sealing treatment with the treatment with the potassium silicate solution of the present invention, the adhesion between the aluminum plate and the photosensitive layer is further improved.

  The negative photosensitive lithographic printing plate obtained by coating the photosensitive layer on the aluminum plate produced as described above is subjected to inspection exposure with various lasers, and the exposed portion is crosslinked by crosslinking. Since the solubility in the developer is lowered, the pattern of the exposed image is formed by eluting the unexposed portion with an alkaline developer described later.

  Even if the photosensitive lithographic printing plate of the present invention is developed with a developer having a pH of 12 or less, high printing durability and background smudges on non-image areas do not occur. The pH of the developer preferably used in the present invention is 10 to 12, more preferably 11 to 11.8. The pH of the developer is a pH at 25 ° C. As alkaline compounds for adjusting the pH of the developer to a range of 10 to 12, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, water such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide Examples include alkanolamines such as tetraalkylammonium oxide, monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, and N-ethylethanolamine. Of these, alkanolamines are particularly preferable. The content of alkanolamine is preferably in the range of 5 to 100 g per liter of the developer, particularly preferably in the range of 10 to 60 g. The developer of the present invention preferably contains substantially no alkali metal silicate.

  The developer preferably further contains an anionic surfactant, which further improves the dissolution property. Examples of such anionic surfactants include higher fatty acid sulfates, alkyl naphthalene sulfonates, alkyl benzene sulfonates, and dialkyl sulfosuccinates. Among these, alkyl naphthalene sulfonates are preferable. The content of the anionic surfactant is preferably in the range of 1 to 50 g per liter of the developer, and particularly preferably in the range of 3 to 30 g.

  Developers include buffering agents such as phosphoric acid and phosphate, chelating agents such as ethylenediaminetetraacetic acid and diethylenetetraminepentaacetic acid, ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, benzyl alcohol, etc. Various alcohols can be added. After developing using such an alkaline developer, normal gumming is preferably performed using gum arabic, dextrins and the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition,% in an Example means the mass% and a part means a mass part.
<Aluminum plate>
A 0.24 mm thick aluminum plate that has been grained and anodized is subjected to sealing treatment with hot water at 90 ° C. for 30 seconds, and then subjected to conventional silicate treatment or the potassium silicate solution of the present invention. Treated. The processing conditions are shown below.
In addition, although the following potassium silicate aqueous solution used by Tama Chemical Industry Co., Ltd. was used, SiO ₂ contained in the aqueous solution is 20% and KOH is 10%.

<Processing conditions>
Comparative Example 1; 2% aqueous solution of No. 3 sodium silicate, treated at 70 ° C. for 15 seconds.
Comparative Example 2: Water was added to 100 parts of an aqueous potassium silicate solution to make a total of 1000 parts. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 3.7.
Comparative Example 3 90 parts of KOH was added to 100 parts of an aqueous potassium silicate solution, and the total was made 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 0.37.
Invention 1: 30 parts of KOH was added to 100 parts of an aqueous potassium silicate solution, and the total was made 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 0.93.
Invention 2: 10 parts of KOH was added to 50 parts of an aqueous potassium silicate solution, and the total was made up to 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 1.25.
Invention 3: 20 parts of KOH was added to 100 parts of an aqueous potassium silicate solution, and the total was made up to 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 1.25.
Invention 4: 20 parts of KOH was added to 150 parts of an aqueous potassium silicate solution, and the total was made up to 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 1.6.
Invention 5: 10 parts of KOH was added to 100 parts of an aqueous potassium silicate solution, and the total was made up to 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 1.87.
Invention 6: 10 parts of KOH was added to 150 parts of an aqueous potassium silicate solution, and the total was made up to 1000 parts with water. The SiO ₂ / K ₂ O molar ratio of this treatment liquid is 2.24.
The treatment liquid temperature and treatment time are 30 ° C.-20 seconds for Comparative Examples 2 and 3 and Inventions 1 to 6.

<Preparation of negative photosensitive lithographic printing plate for near infrared laser>
The following photosensitive layer coating solution was applied on the various aluminum plates treated as described above so that the dry thickness was 2.2 microns, and dried in a dryer at 75 ° C. A lithographic printing plate was obtained.
<Photosensitive layer coating solution>
Polymer (P-1; Weight average molecular weight of about 90,000) 10 parts by mass Ethylene double bond monomer (C-5) 2 parts by mass Urethane compound (U-11) 4 parts by mass Photopolymerization initiator 1 (BC-6) ) 2 parts by weight Photopolymerization initiator 2 (BS-1) 1 part by weight Sensitizing dye (S-39) 0.4 part by weight 10% phthalocyanine dispersion 0.5 part by weight Dioxane 70 parts by weight Cyclohexane 20 parts by weight

The lithographic printing plate produced as described above is exposed using a thermal output machine (Dainippon Screen Mfg. Image Setter PT-R4000 (oscillation wavelength 830 nm, output 100 mW)), and then the processor PD-912. Using -M (Dainippon Screen Mfg. Co., Ltd.), the following developer was used for processing at 28 ° C. for 20 seconds, and subsequently a gum solution having the following formulation was applied.
<Developer>
N-ethylethanolamine 37g
Phosphoric acid (85% solution) 10g
60g tetramethylammonium hydroxide (25% solution)
Alkyl naphthalenesulfonic acid Na (35% solution) 30 g
Diethylenetriaminepentaacetic acid 1g
1L with water
pH is 11.3 (25 ° C)
<Gum solution>
Phosphoric acid 1 potassium 20g
Gum arabic 30g
Sodium dehydroacetate 0.5g
EDTA2Na 1g
1L with water

A printing test was conducted on the planographic printing plate prepared as described above.
<Printing test>
The printing machine uses a business form offset rotary printing press (Miyakoshi Co., Ltd.) and prints with UV ink (TOKA's Best Cure UV RNC Red) and a moisturizing liquid (5% isopropyl alcohol). Evaluation was made by 5% halftone dots and the number of printed sheets when a fine line image jump occurred.

  As a result of the above test, the planographic printing plates using the aluminum plates of Comparative Examples 1, 2, and 3 had 10,000 printed sheets, and image skipping occurred in all solid images, halftone dots, and fine lines. On the other hand, in the present inventions 1 and 6, jumping occurred in the halftone dot image with 70,000 images, and in the present inventions 2 to 5, no image jumping occurred in any of the 100,000 images. In addition, the lithographic printing plate of the present invention did not cause any background stains in the non-image area.

Claims (1)

On an anodized aluminum plate, a polymer having an ethylenic double bond in the side chain, a monomer or oligomer having two or more ethylenic double bonds in the molecule, a photopolymerization initiator, and near red from visible light In a negative photosensitive lithographic printing plate having a photosensitive layer containing a sensitizer having absorption in a wavelength region of external light, the aluminum plate contains potassium silicate after anodization and is SiO ₂ / M ₂ O (M represents an alkali metal) all SANYO molar ratio is processed with a processing solution of from 0.5 to 3.5, vinylphenyl polymer in a side chain containing an ethylenic double bond in the side chain A photosensitive lithographic printing plate which is a polymer having a group .