JP5165327B2 - Water-soluble composition and planographic printing plate precursor using the same - Google Patents

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 in accordance with digitized image information and directly produces a printing plate without going through a lithographic film is eagerly desired. 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. Since polyvinyl alcohol described in this document is a colorless and transparent resin, the difficulty in defect inspection is a major cause of narrowing the manufacturing conditions, and early improvement is desired.

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.
JP 11-38633 A JP 2006-301565 A

  Accordingly, the object of the present invention is to provide high sensitivity in the infrared region, high resolution, excellent safe light property in the ultraviolet / visible region, defect inspection, and adhesion resistance and scratch resistance between lithographic printing plate precursors. It is to provide a lithographic printing plate precursor for a thermal negative plate having excellent properties.

  As a result of extensive research, the present inventor contains colloidal silica having a purity of 99.9% or more and a primary particle diameter of 400 nm or less as a composition for forming a protective layer, and a water-soluble dye. Thus, the inventors have found that the above object can be achieved and have completed the present invention.

That is, the present invention is a composition for forming the protective layer of a lithographic printing plate precursor provided with a photosensitive layer and a protective layer on a support, having a saponification degree of 86 mol% or more and a sulfonic acid modification rate of 1 % Of polyvinyl alcohol, a purity of 99.9% or more, a colloidal silica having a primary particle diameter of 400 nm or less, and a water-soluble dye, and the water-soluble dye comprises (1) 45 water-soluble acidic yellow dye. A mixture of 5% by weight to 30% by weight of a water-soluble acidic purple dye and (3) 10% by weight to 50% by weight of a water-soluble acidic blue dye. It is a water-soluble composition .
The lithographic printing plate precursor according to the invention also contains, on the support, (A) an infrared absorber, (B) an alkali-soluble resin, (C) a polymerizable initiator, and (D) a polymerizable compound. A photosensitive layer formed by applying a composition and a protective layer formed by applying the water-soluble composition are provided.

  As described in detail below, the water-soluble composition according to the present invention can provide a protective layer exhibiting high strength, high oxygen barrier properties and high water solubility by using a specific acidic polyvinyl alcohol. At the same time, the planographic printing plate itself can be made highly sensitive. In addition, the water-soluble composition according to the present invention contains colloidal silica having a purity of 99.9% or more and a primary particle size of 400 nm or less, so that the surface of the protective layer formed by coating the water-soluble composition is formed. In addition, the colloidal silica fine particles are localized on the surface, and the water resistance, scratch resistance, adhesion resistance and oxygen barrier property can be greatly improved. Moreover, the phenomenon (safelight performance) that makes it easy to be exposed to unnecessary visible light by using specific acidic polyvinyl alcohol can be blocked by containing a water-soluble dye in a specific ratio in the protective layer. It was possible, and the defective part could be well distinguished visually.

Hereinafter, embodiments of the present invention will be described. However, the embodiments described below do not limit the present invention. The water-soluble composition according to the present invention is a composition for forming the protective layer of a lithographic printing plate precursor provided with a photosensitive layer and a protective layer on a support. The sulfonic acid-modified polyvinyl alcohol used in the composition is a polyvinyl alcohol having a saponification degree of 86 mol% or more and a sulfonic acid modification rate of 1% or less.
Although it does not specifically limit as a manufacturing method of sulfonic acid modification polyvinyl alcohol, For example, copolymerization components, such as vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and 2-acrylamido-2-methylpropane sulfonic acid, are used. , Saponification after copolymerization with vinyl ester compound, synthesis by Michael addition of vinyl sulfonic acid or its salt, 2-acrylamido-2-methylpropane sulfonic acid or its salt to polyvinyl alcohol, etc. Can do.

  The sulfonic acid-modified polyvinyl alcohol is commercially available from, for example, Kuraray Co., Ltd., Nippon Synthetic Chemical Industry Co., Ltd., and Nippon Vinegar Poval Co.

  The content of the sulfonic acid-modified polyvinyl alcohol used in the water-soluble composition according to the present invention is preferably 50% by mass to 99.9% by mass with respect to the total solid content mass of the protective layer, and more preferably the lower limit. Is 70% by weight. By setting it as 70 mass% or more, a sensitivity and scratch resistance can be improved more.

  Colloidal silica having a purity of 99.9% or more and a primary particle size of 400 nm or less used in the present invention tends not to be uniformly dispersed in the protective layer but to be localized on the surface of the water-soluble protective layer. is there. The following theory does not limit the technical scope of the present invention at all, but due to this specific tendency, the protective layer is not directly affected, and scratch resistance, adhesion resistance, oxygen barrier properties are not affected. It can be considered that the photosensitive layer can be improved and protected from external moisture. The purity of the colloidal silica in the water-soluble composition according to the present invention is considered to improve the storage stability of the lithographic printing plate precursor according to the present invention. That is, it is presumed that the alkali metal and heavy metal contained in the conventional colloidal silica cause deterioration of the polymerizable initiator, resulting in deterioration of storage stability. From the viewpoint of improving these, it is preferably 99.999% or more, more preferably 99.9999% or more. The purity of the colloidal silica in the water-soluble composition according to the present invention can be measured by an inductively coupled plasma measurement method.

  The colloidal silica used in the water-soluble composition according to the present invention is particularly preferably one synthesized by a sol-gel method using high-purity alkoxysilane as a raw material.

  Colloidal silica used in the water-soluble composition according to the present invention is, for example, from Fuso Chemical Industry Co., Ltd. under trade names such as PL-1MA, PL-1TOL, PL-2LPGME, SP-03B, and SP-1B. It is commercially available.

  The primary particle diameter of the colloidal silica used in the water-soluble composition according to the present invention is excellent in dispersibility and applicability at about 10 nm to 400 nm. The primary particle diameter of the colloidal silica in the water-soluble composition according to the present invention is a value measured by a BET specific surface area measuring device.

  The colloidal silica used in the water-soluble composition according to the present invention may be used by mixing with other colloidal silica or a matting agent unless the performance is deteriorated. As other colloidal silica, synthetic colloidal silica manufactured by Fuji Silysia Chemical Co., Ltd. can be used, for example. Examples of the matting agent include zinc oxide, titanium oxide, alumina powder, starch, starch, polymer particles (for example, particles such as polymethyl methacrylate and polystyrene), and the like. The amount of the matting agent contained in the protective layer is preferably 0.01% by mass to 30% by mass, and a more preferable upper limit is 10% by mass.

  It is preferable that content of the colloidal silica used for the water-soluble composition concerning this invention is 0.01 mass%-50 mass% with respect to the total solid content mass of a protective layer. A more preferred lower limit is 1% by mass, and a more preferred upper limit is 30% by mass. If it is less than 1% by mass, colloidal silica may not be localized on the surface of the protective layer. If it exceeds 30% by mass, the coating performance of the protective layer may be deteriorated.

The water-soluble composition according to the present invention contains a water-soluble dye. By including a water-soluble dye, it is possible to improve a phenomenon (safe light performance) that is easily exposed to unnecessary visible light.
The water-soluble dye includes (1) 45% by mass to 85% by mass of a water-soluble acidic yellow dye, (2) 5% by mass to 30% by mass of a water-soluble acidic purple dye, and (3) It is preferable to use a specific dye mixture obtained by mixing three kinds of water-soluble acidic blue dyes at a ratio of 10% by mass to 50% by mass. The specific dye mixture is mixed at a specific ratio, so that the absorption spectrum, absorbance, etc. are optimized, which not only significantly improves the safelight performance, but also increases the contrast and facilitates visual defect inspection. There is an advantage of becoming.

The said specific dye mixture is obtained by mixing the water-soluble dye marketed by Orient Chemical Industry Co., Ltd. and Hodogaya Chemical Industry Co., Ltd. in said specific ratio, for example.
The water-soluble acidic yellow dye is a compound having an absorption wavelength region in the range of 300 to 550 nm and a maximum absorption wavelength in the range of 420 to 490 nm, and examples thereof include edible yellow 4 and edible yellow 5.
The water-soluble acidic purple dye is a compound having an absorption wavelength region in the range of 400 to 700 nm and a maximum absorption wavelength in the region of 500 to 590 nm. For example, red 401 and purple 401 are listed.
The water-soluble acidic blue dye is a compound having an absorption wavelength region in the range of 500 to 700 nm and a maximum absorption wavelength in the region of 600 to 690 nm. Examples include Blue No. 2, Blue No. 205, Blue No. 202, Blue No. 203, and the like.

  The content of the water-soluble dye used in the water-soluble composition according to the present invention is preferably 0.01% by mass to 50% by mass with respect to the total solid content mass of the protective layer, and a more preferable lower limit is 1 mass%, and a more preferable upper limit is 40 mass%. If it is less than 0.01% by mass, the visible light blocking property may be insufficient, and if it exceeds 50% by mass, it may be difficult to dissolve in the protective layer.

  In addition to the water-soluble composition of the present invention, other known nonionic surfactants, fluorosurfactants, and antifoaming agents can be added as necessary.

  Known additives such as a water-soluble plasticizer can be added to the water-soluble composition of the present invention in order to improve coating properties and 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 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) in the image forming composition 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 a wavelength range of 650. An infrared absorbing dye having an absorption maximum in the range of ˜1300 nm, preferably 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, the photosensitive layer used in the present invention is a negative photosensitive layer in which the solubility in an alkaline aqueous solution is reduced by laser exposure by further containing an infrared absorber.

  Examples of the infrared absorbing dye include a cyanine dye, a squalium dye, a croconium dye, an azurenium dye, a phthalocyanine dye, a naphthalocyanine dye, a polymethine dye, a naphthoquinone dye, a thiopyrylium dye, a dithiol metal complex dye, Anthraquinone dyes, indoaniline metal complex dyes, intermolecular CT dyes and the like are preferable.

Although these pigment | dyes can be synthesize | combined by a well-known method, the following commercial items can also be used.
Nippon Kayaku Co., Ltd .: IR750 (anthraquinone), IR002, IR003 (aluminum), IR820 (polymethine), IRG022, IRG033 (diimmonium), CY-2, CY-4, CY-9, CY-10, CY-20
Dai Nippon Ink Chemical Co., Ltd .: Fastogen blue 8120
Midori Chemical Co., Ltd .: MIR-101, 1011 and 1021
In addition, the above dyes are also commercially available from various companies such as Nippon Photosensitive Dye Co., Ltd., Mitsui Chemicals, Showa Denko Co., Ltd., and FUJIFILM Corporation.

（式中、R₃は水素原子または置換基を有してもよいアルキル基、アルコキシ基を示し、R₄は置換基を有してもよいアルキル基またはアルコキシ基を示し、Ｘは電荷中和イオンを示し、ｎは１〜７を表す。） Among the infrared absorbing dyes, an infrared absorbing dye represented by the following general formula (I) is particularly preferable.

(In the formula, R ₃ represents a hydrogen atom or an optionally substituted alkyl group or alkoxy group, R ₄ represents an optionally substituted alkyl group or alkoxy group, and X represents charge neutralization. Represents an ion, and n represents 1 to 7.)

Although the preferable specific example of the infrared rays absorption pigment | dye represented by the said general formula (I) is shown below, the range of the compound is not limited to these.

  The addition amount of the infrared absorber used in the image forming composition is 0.5 to 10% by mass, preferably 0.6 to 8.0% by mass of the photosensitive layer. When the addition amount is 0.5% by mass or more, particularly 0.6% by mass or more, the sensitivity is particularly high, and when it is 10% by mass or less, particularly 8.0% by mass or less, the developability of the non-image area (unexposed area). Is particularly preferable since it improves.

  The alkali-soluble resin used as the component (B) in the image forming composition is used for improving printing durability and chemical resistance in an exposed area (image area) in a thermal negative plate. The alkali-soluble resin used in the present invention is desirably soluble or swellable with respect to an alkali agent. Examples of such a polymer compound include copolymers of acrylic acid derivatives and polyurethane resins. 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 that can be 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.

  In general, a copolymer of an acrylic acid derivative is an acrylic acid copolymer having a side chain carboxyl group, and has a polymerizable double bond at the terminal by addition reaction of glycidyl methacrylate with the carboxyl group. An alkali-soluble acrylic acid copolymer is particularly desirable.

  The introduction rate of glycidyl methacrylate is 20 to 70%, more preferably 30 to 60%, based on the carboxyl group in the copolymer. When the introduction rate is less than 20%, the sensitivity may be significantly lowered, and when the introduction rate is 70% or more, the developability may be deteriorated.

  The Mw of the acrylic acid derivative copolymer is preferably 1,000 to 500,000, particularly preferably 1,500 to 300,000. When the Mw is 1,000 or more, particularly 1,500 or more, a particularly sufficient coating film can be obtained. When the Mw is 500,000 or less, particularly 300,000 or less, the solubility of the exposed portion in the alkaline developer is improved and particularly good. Can be developed.

  Although it does not specifically limit as a polyurethane resin which can be used as alkali-soluble resin, The glass transition temperature (Tg) of a polymer exists in the range of 50 to 180 degreeC, More preferably, it is 70 to 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 average molecular weight (Mw) of the polyurethane resin is not particularly limited, and any conventionally used polyurethane resin can be used.

  Generally, the alkali-soluble polyurethane resin is a polyurethane resin having a side chain carboxyl group as described in JP-A-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.

A polyurethane resin having a side chain carboxyl group, wherein an alkali-soluble polyurethane resin having a polymerizable double bond group at the end is synthesized by a two-step reaction by adding glycidyl methacrylate to the carboxyl group. Can do. First, a polyurethane resin as a basic skeleton is prepared by using a known catalyst having an activity corresponding to the reactivity of the diisocyanate compound, the diol compound having a carboxyl group, and the diol compound having no carboxyl group in an aprotic solvent. It can be synthesized by adding and heating. Next, the alkali-soluble polyurethane resin can be synthesized by addition reaction of glycidyl methacrylate with the obtained polyurethane as the basic skeleton. The molar ratio of the diisocyanate compound and the diol compound to be used is preferably 0.8: 1 to 1.2: 1. When an isocyanate group remains at the polymer terminal, it is treated with an alcohol or an amine. Finally, it is synthesized in a form in which no isocyanate group remains.
The introduction rate of glycidyl methacrylate is 20 to 70%, more preferably 30 to 60%, based on the carboxyl group in the polyurethane that is the basic skeleton in the first stage. When the introduction rate is less than 20%, the effect of high printing durability may be difficult, and when the introduction rate is 70% or more, developability may be deteriorated.

In synthesizing a polyurethane resin used as an alkali-soluble resin, specific examples of diisocyanate compounds preferably used include those shown below. That is, as a diisocyanate compound,
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-xylene diisocyanate, m-xylene diisocyanate, 4,4-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 3,3-dimethylbiphenyl-4,4 -Diisocyanate, hexanemethylene diisocyanate, trimethylhexanemethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4-methylenebis (cyclohexyl isocyanate), methylcyclohexyl-2,4- (or 2,6-) diisocyanate, 1 , 3-bis (isocyanatomethyl) cyclohexane and the like.

  Specific examples of the diol compound having a carboxyl group include those shown below. That is, as a diol compound having a carboxyl group, 3,5-dihydroxybenzoic acid, 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxypropyl) propionic acid, N, N-2,2- Examples include dihydroxyethyl glycine, bis (hydroxymethyl) acetic acid, 4,4-bis (4-hydroxyphenyl) pentanoic acid, tartaric acid and the like.

  The content rate in the polyeletane resin of the said diol compound which has a carboxyl group is 20-50 mol%, More preferably, it is 25-45 mol%. If it is less than 20 mol%, the developability may be deteriorated, and the addition ratio of glycidyl methacrylate is also narrowed. If it exceeds 50 mol%, the image strength during development is deteriorated and at the same time other diol components cannot be contained. There is.

  Moreover, the diol compound which does not have a carboxyl group and may have the other substituent which does not react with isocyanate can also be used, Specifically, what is shown below is included. That is, as a diol compound, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polyester polyol, polycarbonate diol, neopentyl glycol, 1,3-butylene glycol, 1 , 6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-bis-β-hydroxyethoxycyclohexane, cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, water Bisphenol F, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, ethylene oxide of bisphenol F Side adduct, propylene oxide adduct of bisphenol F, ethylene oxide adduct of hydrogenated bisphenol A, propylene oxide adduct of hydrogenated bisphenol A, hydroquinone dihydroxyethyl ether, p-xylene glycol, dihydroxyethyl sulfone, bis- (2 -Hydroxyethyl) -2,4-tolylene dicarbamate, bis (2-hydroxyethyl) isophthalate, and the like.

  The alkali-soluble resins used in the image forming composition may be used alone or in combination of two or more. The addition amount is 20 to 95% by mass of the photosensitive layer, preferably 25 to 90% by mass. When the addition amount 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) in the image forming composition, 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 organic boron anion constituting the organic boron salt is represented by the following general formula.

In the formula, each of R ₅ , R ₆ , R ₇ and R ₈ may be the same or different, and represents an alkyl group, aryl group, aralkyl group, alkenyl group, alkynyl group, cycloalkyl group or heterocyclic group. Represent. Of these, it is particularly preferred that one of R ₅ , R ₆ , R ₇ and R ₈ 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 alkylphosphonium salts. Examples of particularly preferred organic boron salts are shown below.

  Other preferred radical polymerizable 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 radical polymerizable initiator as described above is preferably in the range of 1 to 40% by mass, more preferably in the range of 1 to 20% by mass with respect to the alkali-soluble resin.

  By containing the polymerizable compound used as the component (D) in the image forming composition, it is considered that the film strength is improved, the sensitivity is excellent in the adhesion to the support, 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, or 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, for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, 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 methacrylate Relate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol hexaacrylate.

  The polymerizable compound can be synthesized by a known method, or a commercially available product can be used. For example, Toa Gosei Co., Ltd., Nippon Oil & Fats Co., Ltd., Kyoeisha Chemical Co., Ltd., Shin Nakamura Chemical Co., Ltd., Mitsubishi Chemical Co., Ltd., Nippon Kayaku Co., Ltd., Osaka Organic Chemical Co., Ltd., etc.

  The amount of the polymerizable compound added is preferably 1 to 80% by mass, more preferably 2 to 70% by mass, based on the total solid content of the photosensitive layer (that is, based on the total solid content of the photosensitive composition). is there. When the addition amount is 1% by mass or more, the sensitivity becomes faster, and when it is 80% by mass 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, and a plasticizer as long as the effects of the present invention are not impaired. Etc. 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 addition amount of these dyes is preferably 0.05 to 5.0% by mass of the photosensitive layer, and more preferably 0.1 to 4.0% by mass. 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 image forming composition 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-dimethyl Amino-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 ' -Trifluoromethylphenyl) amino) -6-diethylaminofluorane, 2- (3,6-bis (diethylamino) -9- (o-chloroanilino) xanthyl benzoate lactam, and the like.

  The addition amount of the leuco dye is 0.01 to 10% by mass, preferably 0.05 to 5% by mass of the photosensitive layer. When the addition amount 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, and when it is 10% by mass or less, particularly 5% by mass or less, the non-image area (exposed part). ) Is particularly preferred since the developability is 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 ratio of the above-mentioned oil-sensitive resin to the total solid content of the photosensitive layer is preferably 0.01 to 10% by mass, and more preferably 0.05 to 10% by mass.

  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 addition amount of the thermal polymerization inhibitor is preferably about 0.01% by mass to about 5% by mass with respect to the mass of the nonvolatile component in the photosensitive layer. Further, if necessary, a higher fatty acid derivative such as behenic acid or behenic acid amide may be added to prevent polymerization inhibition due to oxygen, and may be unevenly distributed on the surface of the layer in the course of drying after coating. . The addition amount of the higher fatty acid derivative is preferably about 0.5% by mass to about 10% by mass with respect to the non-volatile components in the photosensitive layer.

  In order to broaden the stability of the processing with respect to the developing conditions, the image-forming composition described above is not limited to a nonionic surfactant as described in JP-A Nos. 62-251740 and 3-208514. Amphoteric surfactants such as those 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- Examples include betaine type (for example, trade name “Amorgen K” manufactured by Daiichi Kogyo Co., Ltd.). The proportion of the nonionic surfactant and the amphoteric surfactant in the photosensitive layer is preferably 0.05 to 15% by mass, and more preferably 0.1 to 15% by 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 proportion of the plasticizer in the total solid content of the photosensitive layer is preferably 0.01 to 10% by mass, and more preferably 0.05 to 10% by mass.

  The photosensitive layer can be usually obtained 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 coating solution varies depending on the application, but it is preferable that the coating amount is 0.5 to 5.0 g / m ² when dried.

The lithographic printing plate precursor according to the invention comprises the above photosensitive layer and a protective layer on a support. The protective layer can be obtained by dissolving the components described above as the water-soluble composition of the present invention in water or a polar solvent containing water as a main component to form an aqueous solution for forming a protective layer, and applying the solution on the photosensitive layer. it can. The coating amount of the protective layer-forming aqueous solution varies depending on the application, but is preferably 0.5 to 5.0 g / m ² when dried.
As a coating method, the method described above as the photosensitive layer coating method can be employed.

  Examples of the support include 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. Examples thereof include a plate, paper coated with a resin, and a plastic film subjected to a hydrophilic treatment.

  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 applied to the present invention is not specified, and a conventionally known and publicly available aluminum plate can be appropriately used. The thickness of the aluminum plate used in the present invention is approximately 0.1 to 0.5 mm, 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 thus cannot be specified in general. In general, however, the electrolyte concentration is 1 to 60% by mass solution, 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.

The present invention will be described more specifically with reference to the following examples. However, the present examples do not limit the present invention.
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 mass% sodium hydroxide aqueous solution was poured for 5 seconds at 70 ° C., the surface was etched by 3 g / m ² , further washed with water, and then electrolytically roughened at 200 coulomb / dm ² in a 1N hydrochloric acid bath. Processed. Subsequently, the surface was etched again with a 15% by mass aqueous sodium hydroxide solution, washed with water, and then immersed in a 20% by mass nitric acid aqueous solution for desmutting. Next, anodization was performed in a 15% by mass sulfuric acid aqueous solution to form a 2.0 g / m ² oxide film. After washing with water, 1% by mass potassium fluoride at 50 ° C. and 10% by mass phosphoric acid. It was post-treated with a mixed solution of monosodium, washed with water and dried.

[Examples 1-4, Comparative Examples 1-3]
Next, a specific protective layer and specific silica were added to the following photosensitive solution. The following photosensitive solution was applied on the aluminum plate so that the film thickness after drying was 1.6 g / m ² , dried at 90 ° C. for 5 minutes, and then the following protective layer forming aqueous solutions a to i and the following comparisons. One of the aqueous solution photo was applied so that the film thickness was 1.6 g / m ² and dried at 90 ° C. for 3 minutes to obtain a lithographic printing plate.

(Photosensitive layer)
Polymerizable compound (D-1) (0.6 g)
Alkali-soluble resin (C-1) (2.0 g)
Infrared absorber: Infrared absorber (1) (0.05 g)
Radical polymerizable initiator 1: Organoboron salt (B-6) (0.05 g)
Radical polymerizable initiator 2: Triazine compound (T-7) (0.05 g)
Dye: Oil Blue 613 (Orient Chemical Co., Ltd.) (0.15 g)
Solvent: propylene glycol monomethyl ether / tetrahydrofuran = 30 ml / 20 ml

[Aqueous solution for forming protective layer a to d]
Example 1
(Protective layer forming aqueous solution a)
・ Polyvinyl alcohol 100g
(Nippon Vinegar-Poval Co., Ltd. Saponification degree 89 mol%, sulfonic acid modification rate 1% or less)
・ Specific colloidal silica (Fuso Chemical Co., Ltd. purity 99.9% PL-20 (primary particle size 200nm) solid content concentration 24%) 24g
・ Surfactant (Japanese emulsifier, EMALEX 710) 0.1g
・ Edible Yellow No. 4 10g
Water Blak 31 (acid blue dye 30% by mass, acid purple dye 18% by mass, acid yellow dye 52% by mass) 10g
・ Distilled water 1Kg

Example 2
(Protective layer forming aqueous solution)
・ Polyvinyl alcohol 100g
(Saponification degree 96 mol%, sulfonic acid modification rate 1% or less, manufactured by Nippon Vinegar Poval)
・ Specific colloidal silica (Fuso Chemical Co., Ltd. purity 99.9% PL-7 (primary particle size 70nm) solid content concentration 20%) 15g
・ Surfactant (Japanese emulsifier, Emalex 710) 0.1g
・ Edible Yellow No. 4 10g
・ Water Blak 31 10g
・ Distilled water 1Kg

Example 3
(Aqueous solution for forming a protective layer)
・ Polyvinyl alcohol 100g
(Saponification degree 96 mol%, sulfonic acid modification rate 1% or less, manufactured by Nippon Vinegar Poval)
・ Specific colloidal silica (Fuso Chemical Co., Ltd. purity 99.9% PL-1 (primary particle size 15nm) solid content 12%) 20g
・ Surfactant (Japanese emulsifier, Emalex 710) 0.1g
・ Edible Yellow No. 4 10g
・ Water Blak 31 10g
・ Distilled water 1Kg

Example 4
(Protective layer forming aqueous solution)
・ Polyvinyl alcohol 100g
(Saponification degree 96 mol%, sulfonic acid modification rate 1% or less, manufactured by Nippon Vinegar Poval)
・ Specific colloidal silica (Fuso Chemical Co., Ltd. purity 99.9% PL-1 (primary particle size 15nm) solid content 12%) 20g
・ Surfactant (Japanese emulsifier, Emalex 710) 0.1g
・ Edible Yellow No. 4 4.3g
・ Purple No. 401 1.0g
・ Blue No. 203 4.0g
・ Distilled water 1Kg

[Aqueous solution for comparison]
Comparative Example 1
(Comparison aqueous solution e)
・ Polyvinyl alcohol 100g
(Saponification degree 96 mol%, sulfonic acid modification rate 1% or less, manufactured by Nippon Vinegar Poval)
-Control colloidal silica (Silicia 436 made by Fuji Silysia, purity 99.7%,
(Average particle size 4.1μm) 10g
・ Surfactant (Japanese emulsifier, Emalex 710) 0.1g
・ Edible Yellow No. 4 10g
・ Water Blak 31 10g
・ Distilled water 1kg

Comparative Example 2
(To aqueous solution for comparison)
・ Polyvinyl alcohol 100g
(Saponification degree 96 mol%, sulfonic acid modification rate 1% or less, manufactured by Nippon Vinegar Poval)
・ Specific colloidal silica (Fuso Chemical Co., Ltd. purity 99.9% PL-1 (primary particle size 15nm) solid content 12%) 20g
・ Surfactant (Japanese emulsifier, Emalex 710) 0.1g
・ No specific water-soluble dye.
・ Distilled water 1Kg

Comparative Example 3
(Comparative aqueous solution)
・ Polyvinyl alcohol 100g
(Saponification degree 96 mol%, sulfonic acid modification rate 1% or less, manufactured by Nippon Vinegar Poval)
・ Specific colloidal silica (Fuso Chemical Co., Ltd. purity 99.9% PL-1 (primary particle size 15nm) solid content 12%) 20g
・ Surfactant (Japanese emulsifier, Emalex 710) 0.1g
・ Edible Yellow No. 4 4.3g
・ Purple No. 401 1.0g
・ Blue No. 203 4.5g
・ Distilled water 1Kg

[Evaluation method]
The obtained lithographic printing plate precursor was evaluated as follows.
1. Sensitivity evaluation The obtained lithographic printing plate precursor was exposed on a Trendsetter 800QTM manufactured by Creo, changing the irradiation energy at a resolution of 2400 dpi and an outer drum rotation speed of 360 rpm. After the exposure, a developer (DH-N) manufactured by Fuji Film Co., Ltd. was diluted 4 times and developed at 30 ° C. for 12 seconds using a PK-910II automatic processor. At this time, the lower the irradiation energy, the higher the sensitivity.

2. The lithographic printing plate precursor obtained by the FM screening test was exposed to a high-definition image of FM staccato 36 at a resolution of 2400 dpi and an outer drum rotation speed of 360 rpm with an irradiation energy of 70 mJ / cm ² using a Trendsetter 800QTM manufactured by Creo. After the exposure, a developer (DH-N) manufactured by Fuji Film Co., Ltd. was diluted 4 times and developed at 30 ° C. for 12 seconds using a PK-910II automatic processor. At this time, if banding was not observed visually, it was determined to be acceptable.

3. A slip sheet is sandwiched on a lithographic printing plate precursor obtained by a scratch resistance test, and a weight is applied (100, 200 g) to intentionally damage it. After that, the entire solid image is exposed at a resolution of 2400 dpi, external drum rotation speed of 360 rpm, and irradiation energy of 70 mJ / cm ² with a Crester Trendsetter 800QTM. Thereafter, a developer (DH-N) manufactured by Fuji Film Co., Ltd. was diluted 4 times and developed at 30 ° C. for 12 seconds using a PK-910II automatic processor. At this time, if there was no damage even if a 200 g weight was applied to the part that was intentionally scratched, it was accepted.

4). The lithographic printing plate precursor obtained by the light covering test was shifted to an illuminance of 400 lux and UV-cut light every minute to expose the lithographic printing plate precursor for 30 minutes. Thereafter, a developer (DH-N) manufactured by Fuji Film Co., Ltd. was diluted by 4 and developed at 30 ° C. for 12 seconds using a PK-910II automatic developing machine. In the evaluation method, in order to confirm whether the exposed part is developed, the exposed part is not exposed to light, and the exposed part is ink-filled with newspaper ink (Toyovantian echo ink ink, manufactured by Toyo Ink Industries Co., Ltd.). If the ink does not get on, it is determined to pass.

5. The lithographic printing plate precursor (10 × 10 cm) obtained by the releasability test was overlaid on a lithographic printing plate precursor without interleaving paper in a constant temperature bath at 30 ° C. and 70% humidity, and weighted by 10 kg for one week. Then, when there was no sticking when it took out, it was set as the pass.

6). The lithographic printing plate precursor obtained by the forced storage stability test was stored in layers at 30 ° C., 70% humidity, 45 ° C., and 40% humidity for 3 days without sandwiching the slip sheet. Thereafter, the obtained lithographic printing plate precursor was exposed on a Trendsetter 800QTM manufactured by Creo with a resolution of 2400 dpi and an outer drum rotation speed of 360 rpm while changing the irradiation energy. After the exposure, a developer (DH-N) manufactured by Fuji Film Co., Ltd. was diluted 4 times and developed at 30 ° C. for 12 seconds using a PK-910II automatic processor. At this time, if the sensitivity did not decrease compared to the low-temperature storage product (25 ° C 40% humidity), it was accepted.

7). Defect site test The obtained lithographic printing plate precursor (510x400mm) was considered acceptable if the defects could be identified visually. When it was difficult to see or discriminate, it was rejected.

  As is apparent from Table 1, the water-soluble compositions according to Examples 1 to 4 contain specific polyvinyl alcohol and specific high-purity colloidal silica, so that the resulting lithographic printing plate precursor for thermal negative plate is high. It was found to be excellent in sensitivity, FM suitability, scratch resistance, releasability, and forced storage. Further, the water-soluble composition according to Examples 1 to 4 can further provide a lithographic printing plate precursor for a thermal negative plate having good light coverage and defect inspection by containing a dye mixed at a specific ratio. all right.

Claims (2)

A composition for forming the protective layer of a lithographic printing plate precursor comprising a photosensitive layer and a protective layer on a support,
Polyvinyl alcohol having a saponification degree of 86 mol% or more and a sulfonic acid modification rate of 1% or less, a colloidal silica having a purity of 99.9% or more and a primary particle diameter of 400 nm or less, and a water- soluble dye, (1) 45% to 85% by weight of a water-soluble acidic yellow dye, (2) 5% to 30% by weight of a water-soluble acidic purple dye, and (3) a water-soluble acidic blue dye. the mixture der Ru water-soluble composition of 50 wt% or less than 10 wt%. Photosensitivity formed by applying an image forming composition containing (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 layer and a protective layer formed by applying the water-soluble composition according to claim 1 .