JP2011215476A - Composition for forming protective layer, and photosensitive planographic printing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planographic printing original plate for thermal negative plate having high sensitivity and high resolution in an IR region and excellent safe light properties in UV and visible light regions and having a photosensitive layer having excellent adhesion resistance and scratch resistance between planographic printing original plates.SOLUTION: The planographic printing original plate has the protective layer formed by applying a protective layer forming composition containing at least diacetone acrylamide copolymerization modified polyvinyl alcohol containing 0.1 to 15 mol% diacetone acrylamide unit, a surfactant represented by a general formula (I) and a matting agent having 1 to 10 μm average particle diameter on the photosensitive layer formed on a supporting body.

Description

  The present invention relates to a lithographic printing plate precursor, and particularly to a negative lithographic printing plate precursor for so-called direct plate making which can be directly made from a digital signal of a computer or the like.

  Conventionally, as a lithographic printing plate precursor, one having a constitution in which a lipophilic photosensitive resin layer is provided on a hydrophilic support is widely used. As the plate making method, usually, a method of obtaining a desired printing plate by dissolving and removing a non-image portion after mask exposure through a lith film has been used.

  Recently, digitization techniques that electronically process, store, and output image information using a computer have become widespread. Various new image output methods corresponding to such digitization technology have come into practical use. As a result, computer-to-plate (CTP) technology that scans highly directional light such as laser light according to digitized image information and directly produces a printing plate without going through a lithographic film is eagerly desired. Therefore, obtaining a lithographic printing plate precursor adapted to this is an important technical issue.

  As such a lithographic printing plate precursor capable of scanning exposure, a configuration in which a photosensitive layer containing a photosensitive composition capable of generating active species such as radicals by laser exposure on a hydrophilic support has been proposed and marketed. Has been. This lithographic printing plate precursor is subjected to laser scanning exposure based on digital information to generate active species, which causes the photosensitive layer to undergo physical or chemical changes to insolubilize it, and subsequently develop the negative lithographic printing. You can get the original version.

  Patent Document 1 is known as an example of a photosensitive composition in which a water-soluble polymer is laminated on a photosensitive layer. However, the lithographic printing plate using the protective layer described in Patent Document 1 has a large amount of waste liquid from the water-washed layer because the protective layer is washed and removed with a water-washed layer after laser exposure and then developed. From the aspect of environmental response, early improvement is necessary. Patent Document 2 discloses a protective layer containing a mica compound in a specific polyvinyl alcohol resin. The specific high saponification degree polyvinyl alcohol described in this document exhibits high oxygen barrier properties, and thus not only becomes highly sensitive and easily exposed to light, but also has poor solubility in water. Therefore, there is a problem in operation due to the precipitation of polyvinyl alcohol in the washing layer or in the developer. In addition, although the mica compound has an ultraviolet blocking effect, it is an inorganic compound, and thus it stays in the developing tank and requires a large burden for pipe cleaning.

  On the other hand, shortening the time required for the exposure process is important as the productivity in the plate making operation of a photopolymerization type lithographic printing plate precursor that is easy to develop. In the exposure process, a laminated body in which an interleaf sheet having an anti-adhesion function between the original plates and an anti-scratching function caused by rubbing the surface of the relatively soft protective layer with the aluminum support is usually inserted between the original plates. Supplied. Therefore, the slip sheet removal time in the exposure process has been a cause of inefficiency. In order to improve the efficiency in this exposure process, it is sufficient to omit the process of removing the slip sheet by using a laminate that does not insert the slip sheet between the master plates. There has been a desire for improvements in adhesion and scratches caused by rubbing the surface of the protective layer with the aluminum support.

  In addition, as a resin composition for a paper coating agent, a monofunctional hydrazine compound is added to a saponified product of a diacetone acrylamide-fatty acid vinyl ester copolymer, or a diacetone acrylamide-fatty acid vinyl ester copolymer is used. It has been reported that a saponified product is blended with a polyfunctional hydrazide compound and a maleic acid copolymer (Patent Documents 3 to 4).

JP 11-38633 A JP 2006-301565 A JP 2002-146141 A JP 2003-313383 A

  The object of the present invention is to provide a photosensitive layer having high sensitivity and high resolution in the infrared region, excellent safe light properties in the ultraviolet and visible light regions, and excellent adhesion resistance and scratch resistance between lithographic printing plate precursors. Is to provide a lithographic printing plate precursor for a thermal negative plate.

（上式中、Ｒ^１及びＲ^２は、独立して炭素原子数１〜５のアルキル基であり、Ｒ^３及びＲ^４は、独立して炭素原子数１〜５のアルキル基であり、ｐ及びｑは同一であっても異なっていてもよい１〜３の整数であり、ｍ及びｎは同一であっても異なっていてもよい零又は正の整数であり、ｍ＋ｎは０〜６０である。）
で表される界面活性剤と、平均粒径１〜１０μｍのマット剤を少なくとも含有する、平版印刷版原版の保護層形成用組成物を提供する。
また、本発明は、支持体上に、（Ａ）赤外線吸収剤、（Ｂ）アルカリ可溶性樹脂、（Ｃ）重合性開始剤、及び（Ｄ）重合性化合物を少なくとも含有する画像形成用組成物を塗布して形成された感光層と、該感光層上にこの保護層形成用組成物を塗布して形成された保護層とを備えた平版印刷版原版を提供する。 As a result of intensive studies, the present inventor has made the protective layer for protecting the photosensitive layer contain a specific polyvinyl alcohol, an acetylene glycol surfactant and a matting agent having an average particle diameter of 1 to 10 μm as described above. The inventors have found that the object can be achieved and have completed the present invention.
The present invention relates to diacetone acrylamide copolymer-modified polyvinyl alcohol containing 0.1-15 mol% of diacetone acrylamide units, and the following general formula (I):

(In the above formula, R ¹ and R ² are independently alkyl groups having 1 to 5 carbon atoms, R ³ and R ⁴ are independently alkyl groups having 1 to 5 carbon atoms, p And q is an integer of 1 to 3 which may be the same or different, m and n are zero or a positive integer which may be the same or different, and m + n is 0 to 60. .)
A composition for forming a protective layer of a lithographic printing plate precursor comprising at least a surfactant represented by the formula (1) and a matting agent having an average particle diameter of 1 to 10 μm.
The present invention also provides an image-forming composition containing at least (A) an infrared absorber, (B) an alkali-soluble resin, (C) a polymerizable initiator, and (D) a polymerizable compound on a support. Provided is a lithographic printing plate precursor comprising a photosensitive layer formed by coating, and a protective layer formed by applying the protective layer-forming composition on the photosensitive layer.

  The protective layer-forming composition according to the present invention can obtain a protective layer exhibiting film surface strength, oxygen barrier property, and high water solubility by using a specific copolymerized polyvinyl alcohol, and can improve the lithographic printing plate itself. Sensitivity can be achieved. In addition, the water-soluble composition according to the present invention contains an acetylene glycol surfactant and a matting agent having an average particle size of 1 to 10 μm, so that the surface of the protective layer formed by applying the water-soluble composition. The surface can be localized to improve scratch resistance and peelability.

Hereinafter, embodiments of the present invention will be described. However, the embodiments described below do not limit the present invention.
The composition for forming a protective layer according to the present invention is a composition for forming a protective layer for protecting the photosensitive layer of a lithographic printing plate. This composition contains diacetone acrylamide copolymer-modified polyvinyl alcohol containing 0.1-15 mol% of diacetone acrylamide units.
The diacetone acrylamide copolymer-modified polyvinyl alcohol is not particularly limited as long as it contains 0.1 to 15 mol% of diacetone acrylamide units, but preferably 0.1 to 15 mol% of diacetone acrylamide and 85 to 99.9 mol. % Of the fatty acid vinyl ester is polymerized to saponify the copolymer, and the preferable degree of saponification is 85.0 to 99%. Examples of the fatty acid vinyl ester include vinyl esters such as acetic acid, formic acid, propionic acid, and pivalic acid, and vinyl acetate is preferable. A part of the fatty acid vinyl ester unit is in the range of 0.1 to 20 mol%, unsaturated monocarboxylic acid such as crotonic acid, acrylic acid, methacrylic acid or the like, ester, salt, anhydride, amide or nitrile, maleic acid, Unsaturated dicarboxylic acids such as itaconic acid and fumaric acid or salts thereof, unsaturated dibasic acid monoalkyl esters such as monomethyl maleate and monomethyl itaconic acid, α-olefins having 2 to 30 carbon atoms, alkyl vinyl ethers, vinyl Other monomer units such as pyrrolidones may be substituted.
As the production method, for example, a known method such as saponification of a polymer obtained by copolymerizing vinyl acetate and diacetone acrylamide can be used (Patent Document 3 and Patent Document 4).

  The viscosity of the diacetone acrylamide copolymer-modified polyvinyl alcohol containing 0.1 to 15 mol% of diacetone acrylamide units is preferably 30 to 150 (mPa · s), more preferably 35, in a 4 mass% aqueous solution at 20 ° C. ~ 60 (mPa · s). The viscosity is measured with a B-type viscometer (RB-80L manufactured by Toki Sangyo Co., Ltd.).

  The content of diacetone acrylamide copolymer-modified polyvinyl alcohol used in the protective layer forming composition is 60 to 95% by mass in the solid component in the protective layer forming composition, that is, in the protective layer to be formed. The lower limit is more preferably 70% by mass. By setting it as 70 mass% or more, a sensitivity, water resistance, and scratch resistance can be improved more.

Ｒ^１及びＲ^２は、独立して炭素原子数１〜５のアルキル基、好ましくは炭素原子数２〜５のアルキル基、特に好ましくはイソアミル基である。Ｒ^３及びＲ^４は、独立して炭素原子数１〜５のアルキル基であり、好ましくはメチル基である。
ｐとｑは、同一であっても異なっていてもよい１〜３の整数であり、好ましくは２〜３の整数であり。特に好ましくは２である。すなわち、付加するアルキレンオキサイドとしては、エチレンオキサイドおよびプロピレンオキサイドが好ましく、特に好ましくはエチレンオキサイドである。
ｍおよびｎは同一であっても異なっていてもよい零又は正の整数であり、ｍ＋ｎは０〜６０、好ましくは０〜３０、さらに好ましくは２〜２０である。
一般式（Ｉ）で表される界面活性剤は、例えば、日信化学工業社より市販されているオルフィンシリーズ等を挙げることが出来る。例えば、Ｅ．１００４（式（１）においてＲ^１＝Ｒ^２＝イソブチル、Ｒ^３＝Ｒ^４＝メチル、ｋ＝２、ｍ＋ｎ＝３.５）、Ｅ．１０１０（ｍ＋ｎ＝１０以外はＥ．１００４と同じ）、ＰＤ−００１、ＰＤ−００２Ｗ、ＰＤ−００４、ＰＤ−００５、ＥＸＰ．４００１、ＥＸＰ．４２００、ＥＸＰ．４１２３、ＷＥ−００３、ＳＰＣ、ＡＦ−１０３、ＡＦ−１０４、ＡＫ−０２、ＳＫ−１４、ＰＤ−００３、ＰＤ−２０１、ＰＤ−３０１、Ｂ、Ｐ、Ａ等の商品名にて市販されている。 The composition for forming a protective layer also contains an acetylene glycol surfactant represented by the following general formula (I). By including the surfactant represented by the general formula (I), the coating performance of the protective layer can be improved and a stable film thickness can be formed. In addition, it seems to form a tough film by hydrogen bonding with specific diacetone acrylamide copolymer-modified polyvinyl alcohol.

R ¹ and R ² are independently an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 2 to 5 carbon atoms, and particularly preferably an isoamyl group. R ³ and R ⁴ are each independently an alkyl group having 1 to 5 carbon atoms, preferably a methyl group.
p and q are the integers of 1-3 which may be the same or different, Preferably they are an integer of 2-3. Particularly preferred is 2. That is, as the alkylene oxide to be added, ethylene oxide and propylene oxide are preferable, and ethylene oxide is particularly preferable.
m and n are zero or positive integers which may be the same or different, and m + n is 0 to 60, preferably 0 to 30, and more preferably 2 to 20.
Examples of the surfactant represented by the general formula (I) include the Olphine series commercially available from Nissin Chemical Industry. For example, E.I. 1004 (in formula (1), R ¹ = R ² = isobutyl, R ³ = R ⁴ = methyl, k = 2, m + n = 3.5), E.I. 1010 (same as E.1004 except m + n = 10), PD-001, PD-002W, PD-004, PD-005, EXP. 4001, EXP. 4200, EXP. 4123, WE-003, SPC, AF-103, AF-104, AK-02, SK-14, PD-003, PD-201, PD-301, B, P, A, etc. Yes.

  The content of the surfactant represented by the general formula (I) used in the protective layer forming composition is 0.1 to 10% by mass in the protective layer (in the solid component amount of the protective layer forming composition), Preferably it is 0.1-5.0 mass%.

  The composition for forming a protective layer is used by mixing with a matting agent. The matting agent controls releasability and slipperiness when lithographic printing plates are stacked. As the matting agent, for example, zinc oxide, titanium oxide, alumina powder, starch, starch, polymer particles (for example, particles of polymethyl methacrylate, polystyrene, acrylic resin, etc.) can be used. From the viewpoint of releasability, the average particle size of the matting agent contained in the protective layer is preferably 1 to 10 μm. The average particle size is based on the measurement of a particle size distribution measuring device (Coulter counter).

  The content of the matting agent used in the protective layer forming composition is preferably 0.01 to 30% by mass in the protective layer (in the solid component amount of the protective layer forming composition). More preferably, it is 10 mass%.

The composition for forming a protective layer may contain hydrogenated lecithin. It is localized on the surface of the protective layer, does not directly affect the protective layer, and can improve scratch resistance, adhesion resistance, oxygen barrier properties and protect the photosensitive layer from external moisture Conceivable.
Hydrogenated lecithin is produced by hydrogenating the fatty acid part of lecithin using various phospholipids extracted from animals and plants as raw materials. The ratio of hydrogenation in the fatty acid moiety of lecithin is preferably 90 to 100%. Lecithin is various phospholipids extracted from animals and plants, and includes phosphatidylcholine (PC, L-α-lecithin), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidic acid (PA), and the like. .
Hydrogenated lecithin is commercially available, for example, from Sakai Oil Co., Ltd. under the trade names SLP-White H, SLP-PC70H, SLP-PC92H, SLP-LPC70H, and SLP-White Reso H.
The average particle size of the hydrogenated lecithin is preferably 10 nm to 20 μm, more preferably about 100 nm to 10 μm, which is excellent in dispersibility and coatability. The average particle size is based on the number average particle size measured by the light scattering method.

  The content of hydrogenated lecithin used in the protective layer-forming composition is preferably 0.01 to 30% by mass (in the solid component amount of the protective layer-forming composition) in the protective layer, and more preferably the lower limit. Is 1% by mass. Within this range, hydrogenated lecithin is localized on the surface of the protective layer, but if it exceeds 30% by mass, the coating performance of the protective layer may deteriorate.

The composition for forming a protective layer of the present invention is a water-soluble composition, and may further contain a known water-soluble dye, nonionic surfactant, fluorine-based surfactant, and antifoaming agent as necessary. I can do it.
In the protective layer of the present invention, known additives such as a water-soluble plasticizer can be added to improve the coating properties and the physical properties of the film. For example, propionamide, cyclohexanediol, glycerin, sorbitol, polyethylene glycol and the like can be mentioned. A water-soluble (meth) acrylic polymer can also be added.

  The protective layer composition of the present invention can form a protective layer on the photosensitive layer of the lithographic printing plate precursor by coating or the like. In the case of coating, water is mainly used as a coating solution, but a solvent having excellent affinity with water may be mixed. In particular, alcohols are preferable, and methanol, ethanol, propanol, isopropyl alcohol, and the like are preferable. These solvents are used alone or in combination of two or more. Moreover, although the density | concentration which apply | coats the composition for protective layer formation is dependent on the application | coating method, it is desirable that the total solid content density | concentration shall be 1 to 50%.

The lithographic printing plate precursor according to the present invention comprises, on a support, (A) an infrared absorber, (B) an alkali-soluble resin, (C) a polymerizable initiator, and (D) an image forming compound containing a polymerizable compound. A photosensitive layer formed by applying the composition is provided.
The infrared absorber used as the component (A) is not particularly limited as long as it is a compound that can absorb light from an image exposure light source and convert the energy into heat, but has an absorption maximum in a wavelength range of 650 to 1300 nm. In particular, an infrared absorbing dye having an absorption maximum and a molar extinction coefficient ε of 10 ⁵ or more is particularly effective. The infrared absorbent is used to promote the generation of radicals by causing heat or photoelectron transfer generated from the infrared absorbent upon irradiation with light. For this reason, a photosensitive layer becomes a negative photosensitive layer by which the solubility with respect to alkaline aqueous solution reduces by laser exposure by containing an infrared absorber further.

  Examples of infrared absorbing dyes include cyanine dyes, squalium dyes, croconium dyes, azurenium dyes, phthalocyanine dyes, naphthalocyanine dyes, polymethine dyes, naphthoquinone dyes, thiopyrylium dyes, dithiol metal complex dyes, anthraquinones Of these, dyes based on dyes, indoaniline metal complex dyes, and intermolecular CT dyes are preferred.

  The content of the infrared absorber used in the image forming composition is preferably 0.1 to 10% by mass, more preferably 0.6 to 8.0% by mass in the total solid content of the image forming composition. is there. When the content is 0.6% by mass or more, the sensitivity is particularly high, and when the content is 10% by mass or less, particularly 8.0% by mass or less, the developability of the non-image part (unexposed part) is particularly improved.

  The alkali-soluble resin used as the component (B) is used for improving printing durability and chemical resistance in an exposed area (image area) in a thermal negative plate. The alkali-soluble resin preferably has a pH of 8.0 to 13.0, a temperature of 20 to 35 ° C., and a dissolution time of 12 to 50 seconds, and is completely soluble in an alkaline aqueous solution. The alkali-soluble resin is desirably soluble or swellable with respect to the alkali agent. The alkali agent refers to all alkali agents described later. As such a polymer compound, a copolymer of an acrylic acid derivative, a polyurethane resin, and the like are preferable. Further, an alkali-soluble resin having an ethylenic double bond in the side chain is more soluble in a highly sensitive and alkaline developer.

As a copolymer of an acrylic acid derivative used as an alkali-soluble resin, for example, a monomer selected from the following (m1) to (m10) is used as a conventionally known graft copolymerization method, block copolymerization method, random copolymerization method. It can be obtained by copolymerization using a polymerization method or the like.
(M1) A monomer having a phenolic hydroxyl group. For example, N- (4-hydroxyphenyl) acrylamide, N- (4-hydroxyphenyl) methacrylamide, p-isopropenylphenol, o-hydroxyphenyl acrylate, m-hydroxyphenyl acrylate, p-hydroxyphenyl acrylate, o-hydroxy Phenyl methacrylate, m-hydroxyphenyl methacrylate, and p-hydroxyphenyl methacrylate.
(M2) A monomer having a sulfonamide group. For example, m-aminosulfonylphenyl methacrylate, N- (p-aminosulfonylphenyl) methacrylamide, N- (p-aminosulfonylphenyl) acrylamide.
(M3) A monomer having an active imide group. For example, N- (p-toluenesulfonyl) methacrylamide and N- (p-toluenesulfonyl) acrylamide.
(M4) A monomer having an aliphatic hydroxyl group. For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxy-3-phenoxypropyl methacrylate.
(M5) α, β-unsaturated carboxylic acid. For example, acrylic acid, methacrylic acid, and maleic anhydride.
(M6) A monomer having an allyl group. For example, allyl methacrylate and N-allyl methacrylamide.
(M7) Alkyl acrylates or alkyl methacrylates. For example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, They are butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate, and glycidyl methacrylate.
(M8) Acrylamides or methacrylamides. For example, acrylamide, N-methylol acrylamide, N-ethyl acrylamide, N-hexyl acrylamide, N-cyclohexyl acrylamide, N-hydroxyethyl acrylamide, N-phenyl acrylamide, methacrylamide, N-methylol methacrylamide, N-ethyl Methacrylamide, N-hexylmethacrylamide, N-cyclohexylmethacrylamide, N-hydroxyethylmethacrylamide, N-phenylmethacrylamide.
(M9) Styrenes. For example, styrene, α-methylstyrene, chloromethylstyrene and the like.
(M10) N-vinylpyrrolidone, N-vinylcarbazole, 4-vinylpyridine, acrylonitrile, methacrylonitrile and the like.

  Although it does not specifically limit as a polyurethane resin used as alkali-soluble resin, The glass transition temperature (Tg) of a polymer exists in the range of 50-180 degreeC, More preferably, it is 70-150 degreeC. If the Tg is less than 50 ° C., film formability, that is, a uniform surface of the photosensitive layer may be difficult to form, and surface stickiness may easily occur. On the other hand, when Tg exceeds 180 ° C., alkali solubility is deteriorated, and development defects may easily occur. In the present specification, the glass transition temperature (Tg) is a value measured using a differential scanning calorimeter DSC-60 (manufactured by Shimadzu Corporation). In addition, the weight average molecular weight (Mw) of the said polyurethane resin is not specifically limited, The conventionally used arbitrary polyurethane resin can be used.

  In general, the alkali-soluble polyurethane resin is a polyurethane resin having a side chain carboxyl group as described in JP-A No. 2002-311579, and an addition reaction of glycidyl methacrylate with the carboxyl group is performed at the terminal. An alkali-soluble polyurethane resin having a polymerizable double bond is particularly desirable.

  The alkali-soluble resins used in the image forming composition may be used alone or in combination of two or more. The content is preferably 20 to 95% by mass, more preferably 25 to 90% by mass in the total solid content of the image forming composition. When the content is less than 20% by mass, the printing durability may be deteriorated, and when it is 95% by mass or more, the sensitivity may be deteriorated.

  As the radical polymerizable initiator used as the component (C), known compounds can be used. For example, organic boron salts, trihaloalkyl-substituted compounds, hexaarylbisimidazoles, titanocene compounds, ketoxime compounds, thio compounds, organic peroxides, onium salts (iodonium salts and diazonium salts described in JP-A-2003-114532) , Sulfonium salts) and the like. Among these radical polymerizable 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 content of the radical polymerizable initiator as described above is preferably in the range of 1 to 40% by weight, more preferably in the range of 1 to 20% by weight, based on the total solid content of the image forming composition.

By containing the polymerizable compound used as the component (D), it is considered that the film strength is improved, the sensitivity is excellent and the adhesion to the support is excellent, and the printing durability is improved.
As the polymerizable compound, various compounds can be used, from a monomer having a molecular weight of 1000 or less to an oligomer having a molecular weight of 1000 or more and a polymer region. Examples of such compounds include esters of unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.) and aliphatic polyhydric alcohol compounds, unsaturated carboxylic acids and aliphatic polyhydric compounds. Examples thereof include amides with polyvalent amine compounds, urethanes with unsaturated alcohols and isocyanate compounds, esters with unsaturated carboxylic acids and epoxy compounds, and the like.

  More specifically, examples of the polymerizable compound include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene glycol. Dimethacrylate, butylene glycol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, neopentyldiol diacrylate, neopentyldiol dimethacrylate, polypropylene glycol diacrylate, methoxydiethylene glycol methacrylate, methoxytetraethylene glycol methacrylate, methoxypolyethylene Glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol hexaacrylate.

  The content of the polymerizable compound is preferably 1 to 80% by weight, more preferably 2 to 70% by weight, based on the total solid content of the image forming composition. When the content is 1% by weight or more, the sensitivity becomes faster, and when it is 80% by weight or less, scratch resistance of the image portion (exposed portion) is further improved, which is preferable.

  In addition to the above components, the image forming composition may further include a colorant, a leuco dye, a grease-sensitive resin, a polymerization inhibitor, a surfactant, a plasticizer, and the like as long as the effects of the present invention are not impaired. Can be added.

  In the image forming composition, a colorant can be used to make the image easy to see. As the colorant, oil-soluble dyes and basic dyes are preferable. Specifically, Crystal Violet, Malachite Green, Victoria Blue, Methylene Blue, Ethyl Violet, Rhodamine B, Victoria Pure Blue BOH (Hodogaya Chemical Industries), Oil Blue 613 (Orient Chemical Industries), Oil Green, etc. Can be mentioned. The content of these dyes is preferably 0.05 to 5.0% by mass and more preferably 0.1 to 4.0% by mass in the total solid content of the image forming composition. If it is 0.05% by mass or more, particularly 0.1% by mass or more, the photosensitive layer is sufficiently colored and the image is particularly easy to see. If it is 5.0% by mass or less, particularly 4.0% by mass or less, a non-image after development. The remainder of the dye is difficult to remain in the part, which is preferable.

A leuco dye can be added to the photosensitive layer for the purpose of coloring the photosensitive layer and suppressing dissolution in the developer. The leuco dye used in the present invention is preferably a dye containing a lactone ring used in conventional heat-sensitive recording materials. Preferred examples include 3,3-bis (p-dimethylaminophenyl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3- Bis (p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3,3- Bis (p-diethylamino-2-ethoxyphenyl) -4-azaphthalide, 3,6-dimethoxyfluorane, 3-cyclohexylamino-6-chlorofluorane, 3- (N, N-diethylamino) -5-methyl-7 -(N, N-dibenzylamino) fluorane, 3-dimethylamino-5, 7-dimethylfluorane, 3 Dimethylamino-7-methylfluorane, 3-diethylamino-7, 8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chloroaminofluorane, 3-pyrrolidino- 6-methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 2- (N- (3 And '-trifluoromethylphenyl) amino) -6-diethylaminofluorane, 2- (3,6-bis (diethylamino) -9- (o-chloroanilino) xanthyl benzoate lactam, and the like.
The content of the leuco dye is preferably 0.01 to 10% by mass and more preferably 0.05 to 5% by mass in the total solid content of the image forming composition. When the content is 0.01% by mass or more, particularly 0.05% by mass or more, the photosensitive layer is sufficiently colored, and the visibility is excellent. This is preferable because the properties are particularly improved.

  Furthermore, a grease-sensitive resin can be added to the image forming composition in order to improve the grease sensitivity (lipophilicity) of the photosensitive layer. Examples of the fat-sensitive resin include condensates of phenols and aldehydes substituted with an alkyl group having 3 to 15 carbon atoms, or t-butylphenol formaldehyde resin as described in JP-A No. 50-125806. Etc. can be used. The oil-sensitive resin is preferably 0.01 to 10% by mass, more preferably 0.05 to 10% by mass in the total solid content of the image forming composition.

It is desirable to add a small amount of a thermal polymerization inhibitor to the image forming composition in order to prevent unnecessary thermal polymerization of the polymerizable compound. Suitable thermal polymerization inhibitors include hydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,4-thiobis (3-methyl-6-t-butylphenol) 2,2-methylenebis (4-methyl-6-t-butylphenol), N-nitrosophenylhydroxyamine primary cerium salt and the like. The content of the thermal polymerization inhibitor, the total solid content of the image-forming composition, from about 0.01% to about 5 wt% preferred. If necessary, in order to prevent polymerization inhibition by oxygen, higher fatty acid derivatives such as behenic acid and behenamide are added and unevenly distributed on the surface of the layer in the process of drying after coating. Also good. The content of the higher fatty acid derivative is preferably about 0.5% by weight to about 10% by weight in the total solid content of the image forming composition.

  In order to broaden the stability of the processing with respect to the developing conditions, the image forming composition includes a nonionic surfactant as described in JP-A-62-251740 and JP-A-3-208514, Amphoteric surfactants as described in JP-A-59-121044 and JP-A-4-13149 can be added. Preferable examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether and the like. Preferred examples of the amphoteric surfactant include alkyldi (aminoethyl) glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine, and N-tetradecyl-N, N- Betaine type (for example, trade name “Amogen K”: manufactured by Daiichi Kogyo Co., Ltd.) The content of the nonionic surfactant and the amphoteric surfactant in the image forming composition is preferably 0.05 to 15% by mass, more preferably 0.1% in the total solid content of the image forming composition. ˜15 mass%. When it is 0.05% by mass or more, particularly 0.1% by mass or more, the developability is particularly good, and when it is 15% by mass or less, the developability is not slowed.

A plasticizer can also be added to the image forming composition in order to impart flexibility and the like of the coating film. For example, butylphthalyl, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, trioctyl phosphate, tributyl phosphate and the like are used.
The content of the image forming composition of the plasticizer is preferably 0.01 to 10% by mass, more preferably 0.05 to 10% by mass in the total solid content of the image forming composition.

  For the photosensitive layer, a photosensitive lithographic printing plate precursor can be produced by dissolving the components described above as an image forming composition in a solvent and coating the photosensitive layer coating solution on a suitable support. Solvents used here include methanol, ethanol, propanol, methylene chloride, ethyl acetate, tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monoethyl ether, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, dimethyl Examples include, but are not limited to, formamide, dimethyl sulfoxide, dioxane, dioxolane, acetone, cyclohexanone, trichloroethylene, methyl ethyl ketone, and γ-butyl lactone. These solvents are used alone or in combination of two or more. The concentration of the above components (total solid content including additives) in the solvent is preferably 1 to 50% by mass.

Various methods can be used as the coating method, and examples thereof include spin coating, extrusion coating, bar coater coating, roll coating, air knife coating, dip coating, and curtain coating. The coating amount of the photosensitive layer varies depending on the use, but is preferably 0.5 to 5.0 g / m ² at the time of drying.

As the support, for example, a metal plate such as aluminum, zinc, copper, or steel, a metal plate plated or vapor-deposited with chromium, zinc, copper, nickel, aluminum, iron, or the like, paper, plastic film, or glass plate And paper coated with a resin, a plastic film subjected to a hydrophilic treatment, and the like.
As the support, a polyester film or an aluminum plate is preferable, and among them, an aluminum plate that has good dimensional stability and is relatively inexpensive is particularly preferable. A suitable aluminum plate is a pure aluminum plate or an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements, and may be a plastic film on which aluminum is laminated or vapor-deposited. Thus, the composition of the aluminum plate is not specified, and an aluminum plate made of a publicly known material can be appropriately used. The thickness of the aluminum plate is preferably about 0.1 to 0.5 mm, more preferably 0.12 to 0.4 mm.

  Prior to roughening the aluminum plate, a degreasing treatment with, for example, a surfactant or an alkaline aqueous solution for removing rolling oil on the surface is performed. The surface roughening treatment of the aluminum plate is performed by various methods. For example, a method of mechanically roughening, a method of electrochemically roughening the surface, and a method of selectively dissolving the surface chemically. By the method. As the mechanical method, known methods such as brush polishing, ball polishing, blast polishing, and buff polishing can be used. Further, as an electrochemical surface roughening method, there is a method of performing alternating current or direct current in hydrochloric acid or nitric acid electrolyte. Further, a method combining a mechanical method and an electrochemical method disclosed in JP-A-53-123204 can also be used. The roughened aluminum plate is subjected to an alkali etching treatment and neutralization treatment as necessary, and then subjected to an anodization treatment to enhance the water retention and wear resistance of the surface as desired. In general, sulfuric acid, phosphoric acid, oxalic acid, chromic acid or a mixed acid thereof is used as an electrolyte used for anodizing the aluminum plate.

The treatment conditions for anodization vary depending on the electrolyte used and cannot be specified. However, in general, the concentration of the electrolyte is 1 to 60% by weight, the liquid temperature is 5 to 60 ° C., and the current density is 2 to 50 A / day. dm ² , voltage 1 to 100 V, and electrolysis time 5 seconds to 3 minutes are suitable. If the amount of anodic oxide film is 0.5 to 5.0 g / ^{m 2} is suitable, wear resistance is especially good at 0.5 g / ^{m 2} or more, the 5.0 g / ^{m 2} or less, the pores of the anodic oxidation Dyes and the like are particularly preferred because they are difficult to penetrate.

  After the anodization, the aluminum plate is further subjected to a chemical conversion treatment with, for example, an alkali silicate, sodium phosphate, sodium fluoride, zirconium fluoride, alkyl titanate, trihydroxybenzoic acid alone or in a mixed solution, Sealing treatment by immersion in an aqueous solution or steam bath, coating treatment with an aqueous solution such as strontium acetate, zinc acetate, magnesium acetate, or calcium benzoate, polyvinylpyrrolidone, polyaminesulfonic acid, polyvinylphosphonic acid, polyacrylic acid, Alternatively, chemical conversion or coating treatment of the front or back surface with polymethacrylic acid or the like can be performed as a post-treatment.

  Furthermore, as the above-mentioned support, an aluminum support subjected to the surface treatment described in JP-A-10-297130 can be used.

  As a laser light source for irradiating the lithographic printing plate precursor according to the present invention, a light source having an emission wavelength in the near infrared to infrared region is preferable, and a solid laser or a semiconductor laser is preferable. The emission wavelength is preferably 760 to 1300 nm. Examples of the light source for UV exposure include a carbon arc lamp, a mercury lamp, a metal halide lamp, a xenon lamp, and a chemical lamp. The emission wavelength is preferably 300 to 500 nm.

  As the developer and developer replenisher used for the development of the lithographic printing original plate of the present invention, an aqueous alkaline developer is suitable. Alkaline agents include sodium hydroxide, potassium, ammonium, lithium, sodium silicate, potassium, ammonium, lithium, tribasic sodium phosphate, potassium, ammonium, sodium borate, potassium, Inorganic alkaline agents such as ammonium and sodium carbonate, and organic alkalis such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, sodium octoate, and tetramethylammonium hydroxide Agents and the like. These alkali agents may be used alone or in combination of two or more.

  An activator can be further added to the alkaline aqueous solution. As the activator, an anionic surfactant or an amphoteric surfactant can be used.

Examples of the ionic surfactant include sulfates of alcohols having 8 to 22 carbon atoms (for example, polyoxyethylene alkyl sulfate soda salt), alkyl aryl sulfonates (for example, sodium dodecylbenzenesulfonate, polyoxyethylene dodecylphenyl sulfate). Soda salt, alkyl naphthalene sulfonic acid soda, naphthalene sulfone soda, formalin condensate of naphthalene sulfone soda), sodium dialkyl sulfonate, alkyl ether phosphate, alkyl phosphate, and the like can be used.
In addition, as the amphoteric surfactant, for example, alkylbetaine type and alkylimidazoline type surfactants are preferable. Furthermore, for example, water-soluble sulfites such as sodium sulfite, potassium sulfite, lithium sulfite, and magnesium sulfite can be added to the alkaline aqueous solution.

  In the lithographic printing plate precursor according to the invention, the protective layer is preferably formed by applying the composition for forming a protective layer on the photosensitive layer and drying it. Examples of the method for applying the protective layer forming composition include spin coating, extrusion coating, and bar coater coating. Here, although the protective layer forming composition mainly uses water as a coating solution, a solvent having an excellent affinity with water may be mixed. In particular, alcohols are preferable, and methanol, ethanol, propanol, isopropyl alcohol, and the like are preferable. These solvents are used alone or in combination of two or more. Moreover, although the density | concentration which apply | coats a protective layer forming composition is dependent on the apply | coating method, it is desirable to make total solid content concentration 1-50%.

The present invention will be described more specifically with reference to the following examples. However, the present examples do not limit the present invention.
<Preparation of aluminum plate>
After 0.24 mm thick aluminum (material 1050) was alkali degreased, the surface was polished with a nylon brush while applying a water suspension of permiston and washed thoroughly with water. Next, a 15 wt% sodium hydroxide aqueous solution was poured for 5 seconds at 70 ° C., the surface was etched by 3 g / m ² , then further washed with water, and then electro-roughened at 200 coulomb / dm ² in a 1N hydrochloric acid bath. Processed. Subsequently, after washing with water, the surface was etched again with a 15% by weight aqueous sodium hydroxide solution, washed with water, then immersed in a 20% by weight aqueous nitric acid solution and desmutted. Next, anodization was performed in a 15% by weight sulfuric acid aqueous solution to form a 2.0 g / m ² oxide film. After washing with water, 1% by weight potassium fluoride at 50 ° C. and 10% by weight phosphoric acid. It was post-treated with a mixed solution of monosodium, washed with water and dried.

<Formation of photosensitive layer>
A photosensitive solution having the following composition was applied onto the aluminum plate so that the film thickness after drying was 1.6 g / m ² and dried at 125 ° C. for 30 seconds to form a photosensitive layer.
(Photosensitive solution)
Polymerizable compound: (D-1) (2.0 g)
Alkali-soluble resin: (C-1) (2.0 g)
Infrared absorber: Infrared absorber (1) (0.05 g)
Radical polymerizable initiator 1: Organic boron salt (B-6) (0.05 g)
Radical polymerizable initiator 2: Triazine compound (T-7) (0.05 g)
Dye: Oil blue 613: (manufactured by Orient Chemical Co., Ltd.) (0.15 g)
Solvent: propylene glycol monomethyl ether / tetrahydrofuran = 30 ml / 20 ml

<Synthesis example 1 of specific polyvinyl alcohol>
A flask equipped with a stirrer, thermometer, and dropping funnel reflux condenser was charged with 672 g of vinyl acetate, 10 g of diacetone acrylamide, and 178 g of methanol. After nitrogen substitution in the system, the internal temperature was raised to 60 ° C. Warm up. A solution prepared by dissolving 1 g of 2,2-azobisisobutyronitrile in 50 g of methanol was added to this system to initiate polymerization. A solution obtained by dissolving 55 g of diacetone acrylamide in 35 g of methanol was dropped at a constant rate over 5 hours after the start of polymerization, and 6 hours later, m-dinitrobenzene was added as a polymerization inhibitor to terminate the polymerization. The polymerization yield was 78%. The remaining vinyl acetate was distilled while adding methanol vapor to the resulting reaction mixture to obtain a 50% aqueous methanol solution of a vinyl acetate polymer containing a diacetone acrylamide copolymer component. To 500 g of this mixture, 50 g of methanol and 10 g of a 4% methanol solution of sodium hydroxide were added and mixed well, and a saponification reaction was carried out at 40 ° C. The obtained gel-like material was pulverized, washed thoroughly with methanol and then dried to obtain diacetone acrylamide copolymer-modified PVA. Elemental analysis revealed that the content of diacetone acrylamide units in the resin was 5.0 mol%. This resin had a 4% aqueous solution viscosity of 26.8 mPa · s at 20 ° C. and a saponification degree of 98.4 mol%. In addition, this viscosity was measured by RB-80L (made by Toki Sangyo Co., Ltd.).

<Synthesis examples 2-3 of specific polyvinyl alcohol>
By changing the charged composition, diacetone acrylamide copolymer-modified polyvinyl alcohol as shown in Table 1 was obtained in the same manner as in Synthesis Example 1.

[Water-soluble protective layer coating solution A to D]
<Example 1>
(Coating solution a)
・ Specific polyvinyl alcohol (Synthesis example 1) 140 g
-Specific surfactant (Nippon Chemical Co., Ltd. EXP.4200) 5.0 g
・ Specific matting agent (Sekisui Plastics Co., Ltd. average particle size 8 μm, SSX-110) 5.0 g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) 20.0 g
・ Distilled water 1Kg

<Example 2>
(Coating solution b)
・ Specific polyvinyl alcohol (Synthesis example 2) 140 g
-Specific surfactant (Nippon Chemical Co., Ltd. EXP.4200) 5.0 g
・ Specific matting agent (Sekisui Plastics Co., Ltd. average particle size 8 μm, SSX-110) 5.0 g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) 20.0 g
・ Distilled water 1Kg

<Example 3>
(Coating solution C)
・ Specific polyvinyl alcohol (Synthesis example 3) 140 g
-Specific surfactant (Nippon Chemical Co., Ltd. EXP.4200) 5.0 g
・ Specific matting agent (Sekisui Plastics Co., Ltd. average particle size 8 μm, SSX-110) 5.0 g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) 20.0 g
・ Distilled water 1Kg

<Example 4>
(Coating solution)
・ Specific polyvinyl alcohol (Synthesis example 1) 110 g
-Specific surfactant (Nippon Chemical Co., Ltd. EXP.4200) 5.0 g
・ Specific matting agent (Sekisui Plastics Co., Ltd. average particle size 8 μm, SSX-110) 5.0 g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) None ・ Distilled water 1Kg

<Comparative Example 1>
(Coating solution e)
140 g of control polyvinyl alcohol (ASM-05X saponification degree 95 mol% polymerization degree 500, manufactured by Nihon Vinegar Bipoval)
-Specific surfactant (Nippon Chemical Co., Ltd. EXP.4200) 5.0 g
・ Specific matting agent (Sekisui Plastics Co., Ltd. average particle size 8 μm, SSX-110) 5.0 g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) 20.0 g
・ Distilled water 1Kg

<Comparative example 2>
(To coating solution)
・ Specific polyvinyl alcohol (Synthesis example 1) 140 g
Control surfactant (Rheodor SP-L10: sorbitan laurate manufactured by Kao Corporation) 5.0 g
・ Specific matting agent (Sekisui Plastics Co., Ltd. average particle size 8 μm, SSX-110) 5.0 g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) 20.0 g
・ Distilled water 1Kg

<Comparative Example 3>
(Coating solution)
・ Specific polyvinyl alcohol (Synthesis example 1) 140 g
-Specific surfactant (Nippon Chemical Co., Ltd. EXP.4200) 5.0 g
Control matting agent (average particle size 15-20 μm, MX-1500H manufactured by Soken Chemical Co., Ltd.)
5.0g
・ Hydrogenated lecithin (SLP-PC70H manufactured by Sakai Oil Co., Ltd.) 20.0 g
・ Distilled water 1Kg

[Evaluation methods]
The obtained lithographic printing plate precursor was evaluated as follows.
1. Sensitivity evaluation The obtained lithographic printing plate precursor was exposed with a Trendsetter 800 Quantum manufactured by Kodak Corporation with a resolution of 2400 dpi and an external drum rotation speed of 360 rpm while changing the irradiation energy. After the exposure, a developer (DJN) manufactured by Okamoto Chemical Industry Co., Ltd. was diluted 4 times and developed using a PK-1310 II automatic developing machine at 30 ° C. for 15 seconds. The exposure amount showing 50.5 ± 0.5% with a halftone dot density measuring machine (iC plate II manufactured by Gretag Macbeth Co., Ltd.) was determined as the optimum sensitivity. At this time, the lower the irradiation energy, the higher the sensitivity.

2. FM screening test The obtained lithographic printing plate precursor was exposed to a high-definition image of FM staccato 36 at a resolution of 2400 dpi and an external drum rotation speed of 360 rpm with an irradiation energy of 60 mJ / cm ² using a Trendsetter 800 Quantum manufactured by Kodak. After the exposure, a developer (DJN) manufactured by Okamoto Chemical Industry Co., Ltd. was diluted 4 times and developed using a PK-1310 II automatic developing machine at 30 ° C. for 15 seconds. If the variation in dot density at 16 locations on the plate surface was 50.5 ± 0.5% using a dot density measuring device (iC plate II manufactured by Gretag Macbeth Co., Ltd.), the test was accepted.

3. Scratch resistance test A slip sheet is sandwiched on the obtained lithographic printing plate precursor, and a weight is applied (100, 200 g) to intentionally damage it. Thereafter, a full solid image is exposed at a resolution of 2400 dpi, an outer drum rotation speed of 360 rpm and an irradiation energy of 60 mJ / cm ^{2 using a} Trendsetter 800 Quantum manufactured by Kodak. Thereafter, a developer (DJN) manufactured by Okamoto Chemical Co., Ltd. was diluted 4 times and developed at 30 ° C. for 15 seconds using a PK-1310 II automatic developing machine. At this time, if the remaining photosensitive layer was not confirmed at the part that was intentionally scratched, it was judged as acceptable.

4). Light Coverage Test The resulting lithographic printing plate precursor was exposed to 50% halftone dot density by FM screening at a resolution of 2400 dpi, external drum rotation speed of 360 rpm and irradiation energy of 60 mJ / cm ^{2 using a} Trendsetter 800 Quantum manufactured by Kodak. Thereafter, the exposed portion was exposed to an illuminance of 800 lux under a fluorescent lamp every 5 minutes. The shading part was shifted and the lithographic printing plate precursor was exposed for up to 60 minutes. Thereafter, a developer (DJN) manufactured by Okamoto Chemical Co., Ltd. was diluted by 4 and developed using a PK-1310 II automatic developing machine at 30 ° C. for 15 seconds. As the evaluation method, if the exposed part for 30 minutes was ± 0.3% compared with before exposure using an FM halftone densitometer, the evaluation was accepted.

5. Releasability Test The obtained lithographic printing plate precursor (10 × 10 cm) was placed in a constant temperature bath at 30 ° C. and 70% humidity for 1 week, and the lithographic printing plate precursor was overlaid without interleaving paper and subjected to a 10 kg load. After that, when the lithographic printing plate precursor was not stuck when taken out, it was judged as acceptable.

6). Forced storage stability test The obtained lithographic printing plate precursor was repeatedly stored for 3 days under both conditions of 30 ° C., 70% humidity, 45 ° C., and 5% humidity with no interleaving paper sandwiched. Thereafter, the obtained lithographic printing plate precursor was exposed with a Trendsetter 800 Quantum manufactured by Kodak Corporation at a resolution of 2400 dpi and an external drum rotation speed of 360 rpm while changing the irradiation energy. After the exposure, a developer (DJN) manufactured by Okamoto Chemical Industry Co., Ltd. was diluted 4 times and developed using a PK-1310 II automatic developing machine at 30 ° C. for 15 seconds. At this time, it was judged as acceptable if the sensitivity did not decrease compared to a low-temperature storage product (25 ° C., 40% humidity).

7). Development residue test The obtained lithographic printing plate precursor (800 × 1100 mm) was not exposed, the developer (DJN) manufactured by Okamoto Chemical Industry Co., Ltd. was diluted 4 times, and the 4000 plate was obtained at 30 ° C. for 15 seconds using a PK-1310 II automatic processor. Developed. Thereafter, the processing solution was drained, and if there was little deposit in the developing tank, it was judged as acceptable.

  Table 2 shows the evaluation results of the lithographic printing plate present plates obtained in Examples 1 to 4 and Comparative Examples 1 to 3. In the table, “◯” indicates a pass and “x” indicates a failure. “Δ” indicates a level at which the light covering performance and the forced storage performance are different from the acceptable product but have no influence on use.

  As is apparent from Table 2, the water-soluble compositions according to Examples 1 to 3 contain the specific polyvinyl alcohol, the specific surfactant, and the matting agent having a specific size, and thereby obtained thermal negative plates. The lithographic printing plate precursor for use was found to have high sensitivity, FM suitability, scratch resistance, light covering property, releasability, forced storage, and low development residue.

Claims (3)

Diacetone acrylamide copolymer-modified polyvinyl alcohol containing 0.1 to 15 mol% of diacetone acrylamide unit, and the following general formula (I)

(In the above formula, R ¹ and R ² are independently alkyl groups having 1 to 5 carbon atoms, R ³ and R ⁴ are independently alkyl groups having 1 to 5 carbon atoms, p And q is an integer of 1 to 3 which may be the same or different, m and n are zero or a positive integer which may be the same or different, and m + n is 0 to 60. .)
A composition for forming a protective layer for a lithographic printing plate precursor, comprising at least a surfactant represented by the formula (1) and a matting agent having an average particle diameter of 1 to 10 μm.   Furthermore, the composition for protective layer formation of Claim 1 containing hydrogenated lecithin.   It was formed by applying an image forming composition containing at least (A) an infrared absorber, (B) an alkali-soluble resin, (C) a polymerizable initiator, and (D) a polymerizable compound on a support. A lithographic printing plate precursor comprising: a photosensitive layer; and a protective layer formed by applying the protective layer-forming composition according to claim 1 or 2 on the photosensitive layer.