JP2008026358A - Photosensitive lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic printing plate excellent in long-term storage stability and excellent also in image quality and thin line reproducibility. <P>SOLUTION: The negative lithographic printing plate has a photopolymerizable photosensitive layer on a support, wherein the photosensitive lithographic printing plate contains a polymerization initiator having a structure represented by formula (I) or (II) in the photosensitive layer. In the formula (I), R<SB>1</SB>-R<SB>3</SB>each represent alkyl, aryl, cycloalkyl, alkoxy or aryloxy, may be the same or different and may link together to form a ring. In the formula (II), X represents a compound capable of forming a complex with borane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lithographic printing plate. More specifically, the present invention relates to a lithographic printing plate capable of forming an image using a scanning exposure device such as a laser based on a digital signal.

  In the photosensitive composition, the molecular structure undergoes a chemical change by a photoreaction, and as a result, a physical phenomenon (physical property) changes. This chemical change by the action of light includes cross-linking, polymerization, decomposition, depolymerization, functional group conversion, etc., and there are various such as solubility, adhesiveness, refractive index, substance permeability and phase change. Such photosensitive compositions have been put into practical use in a wide range of fields such as printing plates, resists, paints, coating agents, and color filters. Furthermore, it has been utilized and developed in the field of photoresist using photoengraving technology (photolithography). Photoresists utilize changes in solubility due to photoreactions, and more precise material design is required due to high resolution requirements.

  A widely used type of lithographic printing plate has a photosensitive coating applied to an aluminum base support. In this coating film, the exposed coating film portion is cured, and the unexposed coating film portion is eluted by the development process. Such a plate is called a negative printing plate. Lithographic printing utilizes the oleophilic and hydrophilic surface properties of the pattern formed on the surface of the printing plate and the background, and when supplying ink and dampening water simultaneously to the printing plate on the printing press in lithographic printing, It utilizes the selective transfer of ink onto a pattern having an oleophilic surface. The ink transferred onto the pattern is then transferred to an intermediate body called a blanket, and further transferred to a printing paper for printing.

  Many studies have been made on a photosensitive composition that forms a relief image by utilizing the above-described change in solubility due to a photoreaction, and has been put into practical use. Among them, in a system in which a radical is generated by using a polymerization initiator to form a relief image by performing a crosslinking reaction, the reaction proceeds quickly and the exposed portion becomes insoluble, which is advantageous when used as a printing plate. Become.

  As a system for generating radicals by using the above polymerization initiator, for example, a recording medium having a thermopolymerizable recording layer containing a photothermal conversion substance, a thermopolymerizable resin and a thermopolymerization initiator on a support is disclosed. . (For example, refer to Patent Document 1.) However, azobisnitrile compounds and organic peroxides used as polymerization initiators have a problem that it is difficult to ensure stability such as sensitivity and long-term storage stability. . Also, the printing durability was not satisfactory.

  A photosensitive composition containing a complex of a cationic dye and a borate anion as a polymerization initiator is disclosed. (For example, refer to Patent Document 2.) Although the mechanism is not clear, this complex functions as a polymerization initiator by absorbing energy and generating radicals. When this complex is used, the sensitivity is increased, but there is a problem in storage stability with time.

  A lithographic printing plate is disclosed in which a photosensitive layer contains an organic boron salt, a dye for sensitizing the organic boron salt, and a polymer having a phenyl group substituted with a vinyl group in the side chain. (For example, refer to Patent Document 3.) Although a printing plate with high sensitivity and improved printing durability can be obtained, there are still problems in storage with time and image quality.

In order to solve the above problem, a polymerizable composition containing a polymerization initiator having a specific structure, a photothermal conversion agent, and a polymerizable compound is disclosed. (For example, refer to Patent Document 4) However, there is a problem in the image quality of the obtained printing plate.
JP-A-8-108621 JP-A-62-143044 JP 2001-290271 A JP 2004-102112 A

  An object of the present invention is to provide a lithographic printing plate which is excellent in storage stability with time and excellent in image quality and fine line reproducibility.

  The object of the present invention is to provide a negative lithographic printing plate having a photopolymerizable photosensitive layer on a support, and a polymerization initiator having a structure represented by the following general formula (I) or (II) in the photosensitive layer. Achieved with lithographic printing plates including.

In general formula (I), R ₁ , R ₂ , and R ₃ represent an alkyl group, an aryl group, a cycloalkyl group, an alkoxy group, and an aryloxy group, which may be the same or different, and are linked to form a ring. You may do it.

  In general formula (II), X represents a compound capable of forming a complex with borane.

  According to the present invention, a lithographic printing plate having excellent storage stability with time and excellent image quality and fine image printing reproducibility can be obtained.

  Hereinafter, the present invention will be described in detail. The present invention is characterized in that a polymerization initiator having a structure represented by the following general formula (I) or (II) is used. By using these compounds, it is possible to obtain a lithographic printing plate having excellent storage stability and excellent image quality and fine image printing reproducibility.

In general formula (I), R ₁ , R ₂ , and R ₃ represent an alkyl group, an aryl group, a cycloalkyl group, an alkoxy group, and an aryloxy group, which may be the same or different, and are linked to form a ring. You may do it.

  Examples of the polymerization initiator represented by the general formula (I) include triethyl borane, triisopropyl borane, tributyl borane, tri-sec-butyl borane, triisobutyl borane, tripentyl borane, trihexyl borane, trioctyl borane, tri Examples thereof include decylborane, tridodecylborane, tricyclopentylborane, tricyclohexylborane, butoxydibutylborane, diethylmethoxyborane, butyldicyclohexylborane, triisoamylborane, S-alpinborane, and R-alpinborane.

  In general formula (II), X represents a compound capable of forming a complex with borane.

  Examples of the compound represented by X in the general formula (II) include diethylamine, dibutylamine, isobutylamine, hexamethylenediamine, N, N-dimethylaniline, N, N-diethylaniline, pyridine, ethanolamine, methyl Examples thereof include sulfide and diethyl sulfide.

  In general formula (I), S-alpin borane, diethylmethoxyborane, R-alpin borane, and in general formula (II), borane-dimethyl sulfide complex, borane-N, N-diethylaniline complex, borane- It is preferred to use one or more compounds selected from the group consisting of pyridine complexes. These are shown below.

  Among the polymerization initiators described above, S-alpin borane, diethyl methoxyborane, and R-alpin borane are particularly preferable because they have excellent storage stability over time.

  The content of the polymerization initiator described above is preferably in the range of 1% by mass to 50% by mass with respect to the dry solid content of the photosensitive layer.

  The photosensitive layer according to the present invention preferably contains a polymer. As the polymer, a polymer having a polymerizable double bond in the side chain can be preferably used. Examples of the polymer having a polymerizable double bond in the side chain include JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-48-64183, JP-B-49-43191. And JP-A-52-30490, JP-A-2001-290271, and JP-A-2006-111860.

  A particularly preferable polymer is a polymer having a phenyl group substituted with a vinyl group in the side chain. When a polymer having a phenyl group substituted with a vinyl group in the side chain is used, it effectively cross-links by recombination of styryl radicals generated by the generated radicals, so there is no need for heat treatment with high sensitivity. A negative photosensitive material having high printing durability can be produced. More specifically, the polymer having a phenyl group substituted with a vinyl group as a polymerizable double bond in the side chain has a group represented by the following in the side chain.

In the formula, Z ₁ represents a linking group, and R ₁₁ , R ₁₂ , and R ₁₃ 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 ₁₄ represents a substitutable group or atom. n represents 0 to ₁ , m ₁ represents an integer of 0 to 4, and k ₁ represents an integer of ₁ to 4.

The chemical formula 6 will be described in more detail. The linking group Z ₁ preferably contains a heterocyclic ring, and other groups and atoms such as oxygen atom, sulfur atom, alkylene group, alkenylene group, arylene group, —N (R ₁₅ ) —, —C (O) —. O—, —C (R ₁₆ ) ═N—, —C (O) —, a sulfonyl group, and the following structures may be contained alone or in a state where two or more are combined. Here, R ₁₅ and R ₁₆ 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 6 is shown below, it is not limited to these examples.

Some of the groups represented above are preferred. That is, it is preferable that R ₁₁ and R ₁₂ are hydrogen atoms and R ₁₃ is a hydrogen atom or a lower alkyl group having 4 or less carbon atoms (methyl group, ethyl group, etc.). k ₁ is preferably 1 or 2.

  The polymer is preferably soluble in an alkaline aqueous solution, and for that purpose, a polymer containing a carboxyl group-containing monomer as a copolymerization component is particularly preferred. In this case, the proportion of the carboxyl group-containing monomer in the copolymer is preferably 5% by mass or more and 99% by mass or less. If the proportion is less than this, the copolymer may not be dissolved in the alkaline aqueous solution. If it is above, the ratio of the polymerizable double bond in the polymer becomes low, and the effect of introducing the polymer may not be recognized.

  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 mono Examples include alkyl esters, 4-carboxystyrene and the like.

  In addition to the monomer having a carboxyl group, other monomer components may be introduced into the copolymer to be synthesized and used as a multi-component copolymer. 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, dodecyl methacrylate, etc., phenyl methacrylate, benzyl methacrylate Methacrylic acid aryl ester or alkyl aryl ester such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, methoxydiethylene glycol methacrylate Methacrylic acid esters having alkyleneoxy groups such as esters, methoxypolyethylene glycol monoester methacrylate, polypropylene glycol monoester methacrylate, amino group-containing methacrylic groups such as 2-dimethylaminoethyl methacrylate and 2-diethylaminoethyl methacrylate Examples similar to these corresponding methacrylic acid esters as acid esters or acrylic acid esters, vinylphosphonic acid or the like as a monomer having a phosphoric acid group, amino group-containing monomers such as allylamine or diallylamine, or vinyl Sulfonic acid and its salt, Allylsulfonic acid and its salt, Methallylsulfonic acid and its salt, Styrenesulfonic acid and its salt, 2-Acrylamide-2-methylpropanesulfonic acid And monomers having a sulfonic acid group such as a salt thereof, monomers having a nitrogen-containing heterocycle such as 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazole, N-vinylcarbazole, or 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 as monomers, 4- Vinylbenzylpyridinium chloride, etc., or acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, dimethylacrylamide, die Acrylamide or methacrylamide derivatives such as til acrylamide, N-isopropyl acrylamide, diacetone acrylamide, N-methylol acrylamide, N-methoxyethyl acrylamide, 4-hydroxyphenyl acrylamide, and also acrylonitrile, methacrylonitrile, phenylmaleimide, hydroxyphenylmaleimide , Vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl benzoate, etc., vinyl ethers such as methyl vinyl ether, butyl vinyl ether, others, N-vinylpyrrolidone, acryloylmorpholine, tetrahydro Furfuryl methacrylate, vinyl chloride, vinylidene chloride, allyl alcohol, vinyl trimethoxy Run, it can be used glycidyl methacrylate and various monomers as arbitrary copolymerization monomers. The proportion of these monomers in the copolymer can be introduced in any proportion as long as the preferred proportion of the carboxyl group-containing monomer in the copolymer composition described above is maintained.

  There is a preferred range for the molecular weight of the polymer as described above, and the weight average molecular weight is preferably in the range of 1,000 to 1,000,000, and more preferably in the range of 10,000 to 300,000.

  Examples of the polymer 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 lithographic printing plate of the present invention is very suitably used for scanning exposure using a laser beam having a wavelength range of 380 to 1100 nm. Sensitizing dyes used to sensitize a laser in such a wavelength range include cyanine, phthalocyanine, merocyanine, coumarin, porphyrin, spiro compound, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, phenothiazine, polyene, azo Compounds, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, squarylium compounds, pyrylium compounds, and further, European Patent No. 0,568,993, US Patent No. 4,508,811 Nos. 5,227,227 can also be used. Specific examples of the sensitizing dye are shown below, but the present invention is not limited thereto.

The content of the sensitizing dye exemplified above is suitably about 3 to 300 mg per 1 m ² of the photosensitive layer. Preferably it is 10-200 mg / m < ² >.

  The lithographic printing plate of the present invention preferably contains a polyfunctional polymerizable monomer or oligomer polymerizable compound having two or more polymerizable double bonds in the molecule. The molecular weight of the polymerizable compound is 10,000 or less, preferably 5000 or less. Examples of the compound include compounds having two or more polymerizable double bonds such as an acryloyl group, a methacryloyl group, and a phenyl group substituted with a vinyl group.

  Examples of the compound having an acryloyl group or a methacryloyl group as a polymerizable double bond include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and neopentyl glycol di (meth) acrylate. , Tetraethylene glycol di (meth) acrylate, trisacryloyloxyethyl isocyanurate, tripropylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, glycerol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, Trimethylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri Meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pyrogallol triacrylate.

  Particularly preferred polymerizable compounds include polymerizable compounds having two or more phenyl groups substituted with vinyl groups in the molecule. When a polymerizable compound having two or more phenyl groups substituted with vinyl groups in the molecule is used, crosslinking is effectively performed by recombination of styryl radicals generated by the generated radicals. A negative photosensitive material having high printing durability can be produced without necessity. A compound having a phenyl group substituted with a vinyl group as a polymerizable double bond is typically represented by the following general formula.

In the formula, Z ₂ represents a linking group, R ₂₁ and R ₂₂ 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 having 1 to 4 carbon atoms, An alkoxy group having 1 to 4 carbon atoms or the like is represented. R ₂₃ is a hydrogen atom, halogen atom, carboxy group, sulfo group, nitro group, cyano group, amide group, amino group, alkyl group, aryl group, alkoxy group, aryloxy group, etc., and these groups are It may be substituted with an alkyl group, amino group, aryl group, alkenyl group, carboxy group, sulfo group, hydroxy group or the like. R ₂₄ represents a substitutable group or atom. m2 represents an integer of 0 to 4, and k2 represents an integer of 2 or more. When m2 is 2 or more, R ₂₄ may be the same or different.

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 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.

  Although a specific example is shown below, it is not limited to these examples.

  The addition amount of the polymerizable compound described above is preferably included in the range of 0.01 parts by mass to 10 parts by mass with respect to 1 part by mass of the polymer having a polymerizable double bond in the side chain. It is particularly preferred that it is contained in the range of 1 part by mass to 1 part by mass.

  In the lithographic printing plate of the present invention, polymerization accelerators represented by amines, thiols, disulfides and the like, chain transfer catalysts, and the like can be added as polymerization accelerators. Specific examples include amines such as N-phenylglycine, triethanolamine, N, N-diethylaniline, and thiols described in US Pat. No. 4,414,312 and Japanese Patent Application Laid-Open No. 64-13144. Disulfides described in JP-A-2-29161, thiones described in U.S. Pat. No. 3,558,322 and JP-A 64-17048, and o- described in JP-A-2-291560. Examples include acylthiohydroxamate and N-alkoxypyridinethiones. The addition amount of the polymerization accelerator is preferably 0.1 to 5% by mass of the total solid content of the polymerization layer. If it is less than this range, the effect cannot be expected. On the other hand, if the amount is too large, the film quality of the polymerized layer tends to deteriorate.

  In the lithographic printing plate of the present invention, it is also preferable to add other components for various purposes in addition to the components described above. In particular, it is preferable to add various polymerization inhibitors for the purpose of preventing thermal polymerization or thermal crosslinking of styryl groups and improving long-term 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 having a polymerizable double bond in the side chain.

  In addition, various dyes and pigments are added as elements constituting a lithographic printing plate for the purpose of enhancing image visibility, and inorganic fine particles or organic fine particles are added for the purpose of preventing blocking of the photosensitive composition. It is also preferably performed.

  Regarding the thickness of the photosensitive layer itself when used as a lithographic printing plate material, it is preferably formed on the support with a dry thickness in the range of 0.5 μm to 10 μm, and more preferably in the range of 1 μm to 5 μm. It is extremely preferable for greatly improving the performance. The photosensitive layer is prepared by mixing a solution containing the above three elements, and is applied onto a support and dried using various known coating methods. As the support, for example, a film or polyethylene-coated paper may be used, but a more preferable support is an aluminum plate that is polished and has an anodized film.

  In order to use a material having a photosensitive layer formed on a support as described above as a printing plate, an alkaline developer is obtained by subjecting the exposed part to exposure or laser scanning exposure and crosslinking the exposed part. Therefore, pattern formation is performed by eluting unexposed portions with an alkaline developer described later.

  The alkaline developer is not particularly limited as long as it is a solution that dissolves the photosensitive layer according to the present invention, but is preferably sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, sodium metasilicate, or potassium metasilicate. Because an aqueous developer in which an alkaline compound such as monoethanolamine, diethanolamine, triethanolamine, triethylammonium hydroxide, etc. is dissolved can selectively dissolve unexposed portions well and expose the lower support surface. Highly preferred. Furthermore, it is also preferable to add various alcohols such as ethanol, propanol, isopropanol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin and benzyl alcohol to the alkaline developer. It is preferable to perform normal gumming using gum arabic etc. after developing using such an alkaline developer.

  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.

(Example)
Using an anodized aluminum plate having a graining treatment with a thickness of 0.24 mm, a photosensitive coating solution represented by the following prescription is applied thereon so that the dry thickness is 2.0 μm, Drying was performed in a dryer at 75 ° C. for 6 minutes.
<Photosensitive coating solution>
Polymer (P-3) 12 parts by mass polymerization initiator (Table 1) 1 part by mass polymerizable compound (C-5) 3 parts by mass sensitizing dye (S-1) 0.5 parts by mass dioxane 70 parts by mass cyclohexane 20 Parts by mass

  Various types of printing plates were prepared by changing the type of polymerization initiator in the photosensitive coating solution as shown in Table 1. For the evaluation, a sample stored immediately after production and stored at 35 ° C. and 80% RH for one month was used.

Using an external drum type plate setter equipped with an 830 nm semiconductor laser, PT-R4000 manufactured by Dainippon Screen Mfg. Co., Ltd., and a sample rotation speed of 1000 rpm, resolution of 2400 dpi, laser irradiation energy of 100 mJ / cm ² , 50 samples were prepared. % Flat screen exposure. After the exposure, development was performed with a developer using an automatic developing machine PD-1310 for PS plate manufactured by Dainippon Screen Mfg. Co., Ltd. as an automatic developing machine. A developer having the following composition was used.
<Developer>
Potassium hydroxide 20g
Potassium silicate 20g
Perex NBL (aromatic anionic surfactant, manufactured by Kao Corporation)
60g
1L of water

  The lithographic printing plate produced as described above was evaluated for image quality and fine line reproducibility. The reproducibility image quality was evaluated by measuring the halftone dot area of the printed matter after printing 200 halftone dot images. The fine line reproducibility is 25 thin line charts of the 200th printed material (charts exposed with fine lines of 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 60, 80, 100 and 200 μm). The fine line reproducibility was evaluated by observing with a double loupe and the fine line width reproduced with ink without interruption. The lower the value, the better the fine line reproducibility. The printing machine is Heidelberg TOK (trademark of offset printing machine manufactured by Heidelberg), the ink is FINE INK New Champion Purple S (manufactured by Dainippon Ink Chemical Co., Ltd.), and the fountain solution is Eu-3 (Fuji Photo Film Co., Ltd.) ) 0.5% aqueous solution of PS fountain solution made by the company). The evaluation results are shown in Table 1.

(Comparative example)
Except that the polymerization initiator was changed as shown in Table 2, various printing plates were prepared in the same manner as in the Examples, and evaluated in the same manner as in the Examples. The results are shown in Table 2.

  As is apparent from the results in Tables 1 and 2, the present invention provides a lithographic printing plate that is excellent in storage stability with time and excellent in image quality and fine line reproducibility.

  As an application example of the present invention, use as a printing plate for lithographic printing can be mentioned. It is easy to handle and can be used for many printed materials because of its excellent storage stability with time and excellent image quality and fine line reproducibility.

Claims (3)

A negative lithographic printing plate having a photopolymerizable photosensitive layer on a support, wherein the photosensitive layer contains a polymerization initiator having a structure represented by the following general formula (I) or (II): Sex lithographic printing plate.

(In general formula (I), R ₁ , R ₂ , and R ₃ represent an alkyl group, an aryl group, a cycloalkyl group, an alkoxy group, and an aryloxy group, which may be the same or different from each other. (It may be formed.)

(In general formula (II), X represents a compound capable of forming a complex with borane.)   The photosensitive lithographic printing plate according to claim 1, comprising a polymer having a polymerizable double bond in a side chain in the photosensitive layer and a sensitizer having absorption in a wavelength region of 380 to 1100 nm.   Compounds represented by the general formula (I) or (II) are S-alpin borane, diethyl methoxy borane, R-alpin borane, borane-methyl sulfide complex, borane-N, N-diethylaniline complex and borane-pyridine complex. 3. The photosensitive lithographic printing plate according to claim 1, wherein the photosensitive layer contains one or more compounds selected from the group consisting of certain compounds.