JP2015125290A - Photosensitive composition and lithographic printing plate precursor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithographic printing plate precursor for a thermal negative plate having a photosensitive layer that has high sensitivity and excellent reproducibility in FM screening, and excels in print durability and chemical resistance in a minute image part, safe light property in UV and visible ray regions, and storage stability, and to provide a photosensitive composition for the photosensitive layer.SOLUTION: The photosensitive composition comprises at least: an alkali-soluble resin having a monomer unit expressed by formula (I); at least one silane coupling agent selected from a group represented by the general formulae (II-1) to (II-5); an infrared absorbent; a tetraphenyl borate in which a phenyl group may be substituted; a radical polymerizable initiator excluding a tetraphenyl borate; and a polymerizable compound having an ethylenic double bond.

Description

  The present invention relates to a lithographic printing plate precursor, and more particularly to a so-called negative lithographic printing plate precursor for direct plate making that 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 technology that electronically processes, stores, and outputs image information using a computer has 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 a version.

  Recently, due to the innovative progress of CTP technology, the frequency of use of high-definition FM screening has increased, and better paper quality has been demanded. However, since FM screening forms an image with a collection of minute images, it is very difficult to improve the printing durability and chemical resistance of the minute images. For example, Patent Document 1 is generally known as a method for improving printing durability. According to Patent Document 1, an aluminum substrate and a photosensitive layer provided thereon are added by adding a very small amount of a silane coupling agent having an unsaturated double bond to a photopolymerizable composition that reacts in the ultraviolet / visible light region. It is stated that the adhesiveness of the ink is improved and the printing durability is improved as a result. However, in such a photosensitive layer, the printing durability of an extremely large image portion corresponding to 65 to 110 lines was certainly improved, but the printing durability and chemical resistance of a micro image used in FM screening were improved. Has not been confirmed. In recent years, Patent Documents 2, 3, and 4 are known as methods for improving the printing durability of a thermal negative photosensitive composition that reacts in the infrared region. According to these patent documents, it is stated that by using a specific alkali-soluble polymer, a high-density and strong cross-linked structure is quickly formed, and high sensitivity and excellent printing durability are realized. However, these patent documents also have not confirmed the printing durability and chemical resistance of micro-images. In particular, unlike a photopolymerizable composition that reacts in the ultraviolet / visible light region, a thermal negative lithographic printing plate omits a polymerization acceleration step called preheating, and therefore, image curing becomes insufficient at a low exposure and becomes minute. As the image becomes insufficient in printing durability, chemical resistance tends to deteriorate as a result. From the above, in order to perform high-quality printing using FM screening, improvement in the printing durability and chemical resistance of the minute image portion is an essential condition, and there is room for early improvement. Furthermore, there was room for early improvement in safelight suitability and storage stability in the ultraviolet and visible regions.

Japanese Patent Laid-Open No. 04-161957 JP 2004-109851 A JP 2007-272079 A JP 2007-272134 A

  Accordingly, an object of the present invention is to provide a photosensitive layer having high sensitivity and excellent FM screening reproducibility, printing durability and chemical resistance of a minute image area, safelight suitability in the ultraviolet / visible region, and storage stability. It is to provide a lithographic printing plate precursor for a thermal negative plate and a photosensitive composition for the photosensitive layer thereof.

（上式中、Ｒ^１及びＲ^２は水素原子又は置換基を有してもよい炭素数１〜１０のアルキル基を示し、Ｌ^１及びＬ^２は置換基を有してもよい炭素数１〜１０のアルキレン基、又は置換基を有してもよい炭素数６〜１５のアリーレン基を示す。）
で表わされる単量体単位を有するアルカリ可溶性樹脂と、下記一般式（ＩＩ−１）〜（ＩＩ−５）

（上式中、Ｒ^３は独立して水素原子又はメチル基を示し、Ｘは独立して炭素数１〜４のアルコキシ基を示し、ｎは独立して１〜３の整数である。）
で表わされる群から選択される少なくとも１種のシランカップリング剤と、赤外線吸収剤と、フェニル基が置換されていてもよいテトラフェニルホウ酸塩と、テトラフェニルホウ酸塩ではないラジカル重合開始剤と、エチレン性二重結合を有する重合性化合物とを少なくとも含有する感光性組成物を提供する。
また、本発明は、支持体と、該支持体の上に当該感光性組成物を用いて形成された感光層とを備えるネガ型平版印刷版原版を提供する。 The present invention relates to the following formula (I)

(In the above formula, R ¹ and R ² represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent, and L ¹ and L ² may have ¹ substituent. Represents an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 15 carbon atoms which may have a substituent.)
An alkali-soluble resin having a monomer unit represented by the following general formulas (II-1) to (II-5):

(In the above formula, R ³ independently represents a hydrogen atom or a methyl group, X independently represents an alkoxy group having 1 to 4 carbon atoms, and n is independently an integer of 1 to 3).
And at least one silane coupling agent selected from the group represented by the formula: And a photosensitive composition containing at least a polymerizable compound having an ethylenic double bond.
The present invention also provides a negative lithographic printing plate precursor comprising a support and a photosensitive layer formed on the support using the photosensitive composition.

  According to the negative lithographic printing plate precursor provided with the photosensitive layer formed using the photosensitive composition of the present invention, the unsaturated double bond site in the silane coupling agent and the alkali-soluble resin upon irradiation with an infrared laser. A very high-density cross-linked structure is obtained by high-speed polymerization with a specific unsaturated double bond site therein. On the other hand, the silyl group portion in the silane coupling agent is self-condensed during coating of the photosensitive film, causing a complicated structural change, and it is considered that a stronger photosensitive film is generated by the interaction between these inorganic compounds in the photosensitive film. . Furthermore, the photosensitive composition of the present invention contains tetraphenylborate, which may have a phenyl group substituted, thereby stabilizing the infrared absorber, radical polymerization initiator and the like of the photosensitive layer for unknown reasons. From the above, the photosensitive layer formed using the photosensitive composition of the present invention is excellent in the printing durability and chemical resistance of the minute image area, and also in the safelight suitability and storage stability in the ultraviolet and visible regions. An excellent high-quality printing plate can be obtained.

In the photosensitive composition of the present invention, the polymerizable compound producing the monomer unit of the general formula (I) is, for example, an addition reaction between a polymerizable compound having an alcoholic hydroxyl group and an isocyanate compound having an unsaturated double bond. Can be obtained from In General Formula (I), L ¹ and L ² represent an alkylene group having 1 to 10 carbon atoms which may have a substituent, or an arylene group having 6 to 15 carbon atoms which may have a substituent. . Examples of the substituent that R ¹ , R ² , L ¹ and L ² may have include a halogen atom, particularly a chlorine or bromine atom, a hydroxyl group, a nitro group, a carboxyl group, an amino group, a cyano group, or a sulfate group. In the case where L ¹ and L ² are an arylene group, it may be either a monocyclic structure or a condensed structure, and may have an alkyl group having 1 to 4 carbon atoms such as a methyl group as a substituent.
R ¹ and R ² are particularly preferably a hydrogen atom or a methyl group. L ¹ and L ² are particularly preferred alkylene groups such as ethyl, propyl, isopropyl, butyl and isobutyl, particularly preferred arylene groups include phenyl and naphthyl, and particularly preferred substituents that the arylene group may have. Includes a methyl group, chlorine and bromine.

  The content of the monomer unit of the general formula (I) is preferably 5 to 70 mol%, more preferably 10 to 60 mol% in the alkali-soluble resin. In the case of 5 mol% or more, particularly 10 mol% or more, a tough and highly flexible image can be obtained when an image is formed. 70 mol% or less, particularly 60 mol% or less, is preferable because it is easy to dissolve in an alkaline aqueous solution and the development speed is not increased and the sensitivity is not decreased.

（上式中、Ｒ^４及びＲ^５は水素原子又は置換基を有してもよい炭素数１〜１０、好ましくは炭素数１〜３のアルキル基を示し、Ｍは置換基を有してもよい炭素数１〜１０、好ましくは炭素数２〜３のアルキレン基を示す。） Moreover, in the photosensitive composition of this invention, it is preferable that alkali-soluble resin contains the monomer unit of the following general formula (III) or general formula (IV) further. This is because the glass transition point (Tg) of the entire alkali-soluble resin is significantly increased by containing the monomer unit of the general formula (III) or (IV), and a tough image can be formed.

(In the above formula, R ⁴ and R ⁵ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms which may have a substituent, and M may have a substituent. A good C1-C10, Preferably C2-C3 alkylene group is shown.)

The compound which produces the monomer unit of the general formula (III) or (IV) can be obtained, for example, from the reaction between an alcohol compound having a specific alicyclic structure and an acrylate ester having an unsaturated double bond. The compound which produces the monomer unit of the general formula (III) or (IV) is commercially available from, for example, Hitachi Chemical Co., Ltd. In R ⁴ and R ⁵ , the alkyl group may be linear, branched or cyclic, and examples of the substituent that the alkyl group may have include a halogen atom, particularly a chlorine or bromine atom, a hydroxyl group, a nitro group, A carboxyl group, an amino group, a cyano group, or a sulfate group is mentioned.

  The content of the monomer unit of the general formula (III) or (IV) is preferably 1 to 55 mol%, more preferably 5 to 40 mol%, still more preferably 10 to 30 mol% in the alkali-soluble resin. is there. When the amount is 5 mol% or more, particularly 10 mol% or more, the solution is stable with respect to an aqueous alkali solution used as a developer, and an image having high chemical resistance is obtained when an image is formed. 40 mol% or less, particularly 30 mol% or less, is preferable because it easily dissolves in an alkaline aqueous solution, and does not increase the development speed and decrease the sensitivity.

As other monomers having a polymerizable unsaturated bond group added to these components as necessary, for example, monomers listed in the following (1) to (10) are desirable.
(1) 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.
(2) A monomer having a sulfonamide group. For example, m-aminosulfonylphenyl methacrylate, N- (p-aminosulfonylphenyl) methacrylamide, N- (p-aminosulfonylphenyl) acrylamide.
(3) A monomer having an active imide group. For example, N- (p-toluenesulfonyl) methacrylamide and N- (p-toluenesulfonyl) acrylamide.
(4) 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.
(5) α, β-unsaturated carboxylic acid. For example, acrylic acid, methacrylic acid, and maleic anhydride.
(6) A monomer having an allyl group. For example, allyl methacrylate and N-allyl methacrylamide.
(7) 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.
(8) 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.
(9) Styrenes. For example, styrene, α-methylstyrene, chloromethylstyrene and the like.
(10) N-vinylpyrrolidone, N-vinylcarbazole, 4-vinylpyridine, acrylonitrile, methacrylonitrile and the like.
One of these compounds may be used alone, or two or more of the same group of compounds (1) to (10) may be combined, or two or more of the different groups of compounds may be used in combination.
The content of monomer units generated from other monomers added as necessary to form the alkali-soluble resin is preferably 1 to 40 mol%, more preferably 5 to 40 mol% in the alkali-soluble resin. is there.

  There is no restriction | limiting in particular about the manufacturing method of alkali-soluble resin, It can manufacture similarly to the manufacturing method of a normal vinyl type or acrylic type copolymer. For example, a desired copolymer can be obtained by dissolving each monomer component in an appropriate solvent, adding a conventionally used radical polymerization initiator, and performing polymerization by heating as necessary. The copolymer thus obtained has a polystyrene calculated weight average molecular weight of 10,000 to 200,000, preferably 20,000 to 100,000, as measured by gel permeation chromatography (GPC). If the weight average molecular weight is less than 10,000, the image portion is likely to swell and the mechanical strength is insufficient. If it exceeds 200,000, it is not preferable because stains due to poor development are likely to occur.

  Examples of the solvent used for forming the alkali-soluble resin include methyl cellosolve, propylene glycol monomethyl ether, dioxane, methyl ethyl ketone, cyclohexanone, N, N-dimethylformamide, N, N-dimethylacetamide and the like. Examples of the radical polymerization initiator used for the polymerization of the copolymer include 2,2′-azobis (2-methylbutyronitrile), benzoyl peroxide, and the like. As addition amount, it is 0.1-1.0 mass% with respect to the whole quantity of a monomer.

According to the present invention, the monomer unit represented by the general formula (I) having a monomer unit of the general formula (III) or (IV) or a monomer unit derived from another monomer as necessary. Alkali-soluble resins having the above may be used alone or in combination of two or more. In terms of image formation, the alkali-soluble resin is preferably 10 to 40% by mass in the solid content of the photosensitive composition.
Preferable examples of the alkali-soluble resin having a monomer unit represented by the general formula (I) include the following (I-1) to (I-4). The number written next to the parenthesis indicates the range of mole percentage.

  The alkali-soluble resin having a monomer unit represented by the general formula (I) may be used in combination with other alkali-soluble resins. Other alkali-soluble resins are preferably methacrylic acid or acrylic acid derivative copolymers or polyurethane resins. The other alkali-soluble resin is preferably 5 to 30% by mass in the solid content of the photosensitive composition.

The copolymer of methacrylic acid or acrylic acid derivative is a methacrylic acid or acrylic acid copolymer having a side chain carboxyl group, and glycidyl methacrylate, 4-hydroxylbutyl acrylate glycidyl ether, acrylic acid 2- ( An alkali-soluble copolymer having a polymerizable double bond at the terminal by addition reaction of 2-vinyloxyethoxy) ethyl, 2- (2-vinyloxyethoxy) ethyl methacrylate or the like is particularly preferable.
The introduction ratio of glycidyl methacrylate and the like is preferably 20 to 70 mol%, more preferably 30 to 60 mol%, based on the carboxyl group in the copolymer. When the introduction ratio is less than 20 mol%, the sensitivity may be remarkably lowered. When the introduction ratio exceeds 70 mol%, the developability may be deteriorated.

  The polystyrene calculated weight average molecular weight of the copolymer of methacrylic acid or acrylic acid derivative by gel permeation chromatography (GPC) measurement is preferably 1,000 to 500,000, particularly preferably 1,500 to 300,000. . When the weight average molecular weight is 1,000 or more, particularly 1,500 or more, a particularly sufficient coating film can be obtained. When the weight average molecular weight is 500,000 or less, particularly 300,000 or less, the solubility of the exposed portion in an alkaline developer is improved. It can be developed particularly well.

  Although it is not particularly limited, as a polyurethane resin that is preferably contained in the photosensitive composition of the present invention, the glass transition temperature (Tg) of the polymer is 50 ° C to 180 ° C, more preferably 70 ° C to The temperature is in the range of 150 ° C., which is not preferable because film formability, that is, a uniform photosensitive layer surface may be difficult to form, and surface stickiness may easily occur. Further, when Tg is higher than 180 ° C., alkali solubility is deteriorated, and development failure may occur easily. Here, in this specification, the glass transition temperature (Tg) was measured using a differential scanning calorimeter DSC-60 (manufactured by Shimadzu Corporation). In addition, the average molecular weight (Mw) of the said polyurethane resin is not specifically limited, The conventionally used arbitrary 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 No. 2002-311579, wherein the carboxyl group has glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, Particularly, an alkali-soluble polyurethane resin having a polymerizable double bond at the terminal by addition reaction of 2- (2-vinyloxyethoxy) ethyl acrylate, 2- (2-vinyloxyethoxy) ethyl methacrylate, or the like desirable.

  Specific examples of the diisocyanate compound preferably used in synthesizing an alkali-soluble polyurethane resin having a polymerizable double bond at the terminal include those shown below. That is, as the 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 of the alkali-soluble polyurethane resin 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 of the diol compound having a carboxyl group in the alkali-soluble polyurethane resin is preferably 20 to 50 mol%, more preferably 25 to 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.

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 obtained 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 not having a 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 diol compound to be used is preferably 0.8: 1 to 1.2: 1. When an isocyanate group remains at the end of the polymer, 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.

The silane coupling agent used in the photosensitive composition of the present invention is at least one selected from the group represented by formulas (II-1) to (II-5).
The silane coupling agent can be produced by a urethane bond reaction between a silane coupling agent having an isocyanate group and a methacrylate or acrylate having a hydroxyl group.

  Examples of silane coupling agents having an isocyanate group include isocyanate propyltriethoxysilane, isocyanatepropylmethyldiethoxysilane, isocyanatepropyldimethylethoxysilane, isocyanatepropyltrimethoxysilane, isocyanatepropylmethyldimethoxysilane, isocyanatepropyldimethylmethoxysilane, and isocyanatepropyltrisilane. Propoxy silane, isocyanate propyl methyl dipropoxy silane, isocyanate propyl dimethyl propoxy silane, isocyanate propyl tributoxy silane, isocyanate propyl methyl dibutoxy silane, isocyanate propyl dimethyl butoxy silane, etc. Propyltrie Kishishiran, isocyanate propyl trimethoxysilane is particularly preferred.

  As the methacrylate or acrylate having a hydroxyl group, hydroxyethyl methacrylate, hydroxyethyl acrylate, glycerol dimethacrylate, glycerol acrylate methacrylate, trimethylolpropane dimethacrylate, trimethylolpropane diacrylate, pentaerythritol trimethacrylate, pentaerythritol triacrylate, dipenta Examples include erythritol pentamethacrylate and dipentaerythritol pentaacrylate. Any of the above methacrylates or acrylates is suitable because industrial products are easily available.

  In performing the urethane bond forming reaction, the reaction temperature is preferably 30 to 150 ° C, more preferably 50 to 100 ° C. If it is less than 30 degreeC, reaction may become slow and it may become inefficient, and when it exceeds 150 degreeC, there exists a possibility that superposition | polymerization of a methacryl group or an acryl group may arise.

  In performing the urethane bond forming reaction, a solvent and a reaction catalyst may be used as necessary. A solvent will not be specifically limited if it does not have an isocyanate group and a hydrolyzable silyl group, and Preferably a hydrocarbon type solvent and an aromatic solvent are mentioned. The reaction catalyst may be any compound known as a urethanization catalyst, and generally includes tertiary amines, tin compounds and the like.

  The content of the novel silane coupling agent of the general formula (II) is preferably 0.5 to 8.0% by mass, more preferably in the total mass of the solid content of the photosensitive composition that will form the photosensitive layer. Is 1.0-7.0 mass%. When the content is 1.0% by mass or more, printing durability and chemical resistance are particularly improved. On the other hand, if it is less than 0.5% by mass, the printing durability and chemical resistance may be deteriorated, and if it exceeds 8.0% by mass, the development may be poor.

The infrared absorber used in the photosensitive composition of the present invention 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 preferably has a wavelength range of 650 to 1300 nm. In particular, an infrared absorbing dye having an absorption maximum in the above range and an absorption maximum having a molar extinction coefficient ε of preferably 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 composition of this invention 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.

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 Dainippon Ink and Chemicals Co., Ltd .: Fastogen blue 8120 Midori Chemical Co., Ltd .: MIR-101, 1011, 1021, and other companies such as Hayashibara Co., Ltd., Mitsui Chemicals, Showa Denko Co., Ltd. and Fuji Film Co., Ltd. Also, the above dyes are commercially available.

（上式中、Ｒ^６及びＲ^７は水素原子又は置換基を有してもよい好ましくは炭素数１〜１２ のアルキル基又はアルコキシ基を示し、Ｒ^８及びＲ^９は置換基を有してもよい好ましくは炭素数１〜２０のアルキル基又はアルコキシ基を示し、Ｚは電荷中和イオンを示し、ｍは１〜７の整数を表す。Ｒ^６〜Ｒ^９が有してもよい置換基としては、ハロゲン原子、特に塩素もしくは臭素原子、水酸基、ニトロ基、カルボキシル基、アミノ基、シアノ基、又は硫酸基が挙げられる。） Among the infrared absorbing dyes, an infrared absorber represented by the following general formula (V) is particularly preferable.

(In the above formula, R ⁶ and R ⁷ may have a hydrogen atom or a substituent, preferably an alkyl group or alkoxy group having 1 to 12 carbon atoms, and R ⁸ and R ⁹ have a substituent. Or preferably an alkyl group or an alkoxy group having 1 to 20 carbon atoms, Z represents a charge neutralization ion, and m represents an integer of 1 to 7. R ^{6 to} R ⁹ may have a substituent. And a halogen atom, particularly a chlorine or bromine atom, a hydroxyl group, a nitro group, a carboxyl group, an amino group, a cyano group, or a sulfuric acid group.

  Although the preferable specific example of the infrared absorber represented by the said general formula (V) is shown below, the range of the compound is not limited to these.

  The content of the infrared absorber is preferably 0.5 to 10% by mass, more preferably 0.6 to 8.0% by mass in the total mass of the solid content of the photosensitive composition. When the content is 0.5% by mass or more, particularly 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 area (unexposed area). Is particularly preferable since it improves.

  The tetraphenylborate salt in which the phenyl group used in the photosensitive composition of the present invention may be substituted is not particularly limited, and a known compound can be used. In the tetraphenylborate having a phenyl group substituted (hereinafter also referred to as a substituted tetraphenylborate), 1, 2, 3, or 4 phenyl groups have at least one substituent. The substituent is, for example, an alkyl group having 1 to 3 carbon atoms, preferably a methyl group. The substituent may be bonded to the 2, 3, 4, or 5 position of the phenyl group, and it is particularly preferable that the substituent is bonded to the carbon at the 4 position. Examples of the cation constituting the substituted or unsubstituted tetraphenylborate include, but are not limited to, tertiary or quaternary phosphonium ions and organic cations such as secondary or tertiary amines. Examples of the substituted or unsubstituted tetraphenylborate include 2-ethyl-4-methylimidazolium tetraphenylborate (CAS 53831-70-2) (trade name EMZ- K, manufactured by Hokuko Chemical Co., Ltd.) 1,5-diazabicyclo [4.3.0] -5-nonenetetraphenylborate (1,5-diazabicyclo [4.3.0] non-5-ene (DBN) tetraphenylborate) (CAS 627543-58-2) (trade name DBNK, manufactured by Hokuko Chemical Co., Ltd.), tetraphenylphosphonium tetrakis (4-methylphenyl) borate (CAS 181259-35-8) (Trade name TPP-MK, manufactured by Hokuko Chemical Co., Ltd.), tetraphenylphosphonium tetraphenylborate (CAS 15525-15-2) (trade name TPP-K, manufactured by Hokuko Chemical Co., Ltd.), and - Tasharu - butyl phosphonium tetraphenylborate (tri-tert-butylphosphonium tetraphenylborate) (CAS 131322-08-2) (trade name TTBuP-K, Hokko Chemical Industry Co., Ltd.).

  The substituted or unsubstituted tetraphenylborate has an action of stabilizing the infrared absorber and the radical polymerization initiator in the photosensitive layer, and increases the stability of the photosensitive layer with respect to temperature and time. The content of the substituted or unsubstituted tetraphenylborate is preferably 3.0 to 6.0% by mass, more preferably 4.0 to 5.0% by mass in the total mass of the solid content of the photosensitive composition. %. When the content is 3.0% by mass or more, particularly 4.0% by mass or more, safelight suitability and storage stability in the ultraviolet / visible region are improved, and 6.0% by mass or less, particularly 5.0% by mass or less. Then, the chemical resistance of the image area and the printing durability of the image area are particularly improved, which is preferable.

  The radically polymerizable initiator used in the photosensitive composition of the present invention is not particularly limited, and a known compound can be used. For example, organic borate, trihaloalkyl-substituted compound, hexaarylbisimidazole, titanocene compound, ketoxime compound, thio compound, organic peroxide, onium salt (iodonium salt, diazonium described in JP-A-2003-114532) Salt, sulfonium salt) and the like. Among these radical polymerizable initiators, organic borate and trihaloalkyl-substituted compounds are particularly preferably used. More preferably, an organic borate and a trihaloalkyl-substituted compound are used in combination.

（式中、Ｒ^１１、Ｒ^１２、Ｒ^１３及びＲ^１４は各々同じであっても異なっていてもよく、アルキル基、アリール基、アラルキル基、アルケニル基、アルキニル基、シクロアルキル基、複素環基を表す。但し、Ｒ^１１、Ｒ^１２、Ｒ^１３及びＲ^１４が全てフェニル基である場合を除く。）
一般式（ＶＩ）は、Ｒ^１１、Ｒ^１２、Ｒ^１３及びＲ^１４のうち一つがアルキル基であり、他の置換基がアリール基であるもの、例えばトリフェニルブチルボレート等が、ラジカル形成の観点から特に好ましい。Ｒ^１１、Ｒ^１２、Ｒ^１３及びＲ^１４の全てがフェニル基であるものを除いているのは、トリフェニルブチルボレート等と比べてラジカルの発生が弱いことが知られており（特開昭62-143044）、感度が低すぎて十分な画像が得られない場合があるためである。 The organic borate anion constituting the organic borate is represented by the following general formula (VI).

(In the formula, R ¹¹ , R ¹² , R ¹³ and R ¹⁴ may be the same or different, and an alkyl group, aryl group, aralkyl group, alkenyl group, alkynyl group, cycloalkyl group, heterocyclic group Except that R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are all phenyl groups.)
In general formula (VI), one of R ¹¹ , R ¹² , R ¹³ and R ¹⁴ is an alkyl group and the other substituent is an aryl group, for example, triphenylbutyl borate, etc. Is particularly preferred. Except for the case where all of R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are phenyl groups, it is known that the generation of radicals is weaker than that of triphenylbutyl borate or the like (JP-A-62). -143044), because the sensitivity is too low to obtain a sufficient image.

  Examples of the cation constituting the organic borate include alkali metal ions and onium compounds. Preferred are onium salts such as ammonium salts such as tetraalkylammonium salts, sulfonium salts such as triarylsulfonium salts, Examples include a reel alkylphosphonium salt. Examples of particularly preferred organic borates 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 1 to 40% by mass, more preferably 1 to 20% by mass with respect to the alkali-soluble resin.

  The polymerizable compound having an ethylenic double bond used in the photosensitive composition of the present invention is not particularly limited, and a known compound can be used. By containing the polymerizable compound, it is considered that the film strength is improved, the sensitivity is high, the adhesiveness with the support is excellent, and the printing durability is also improved.

  As the polymerizable compound having an ethylenic double bond, various compounds from monomers having a molecular weight of 1000 or less to oligomers having a molecular weight of 1000 or more and those having a polymer region can be used. 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 having an ethylenic double bond can be synthesized by a known method, or a commercially available compound can be used. For example, Toa Gosei Co., Ltd., Nippon Oil & Fat Co., Ltd., Kyoeisha Chemical Co., Ltd., Shin-Nakamura Chemical Co., Ltd., Mitsubishi Chemical Co., Ltd., Nippon Kayaku Co., Ltd., Osaka Organic Chemical Industry Co., Ltd., etc. .

  The content of the polymerizable compound having an ethylenic double bond is preferably 1 to 80% by mass, more preferably 2 to 70% by mass, based on the total mass of the solid content of the photosensitive composition. 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.

  The photosensitive composition of the present invention, in addition to the above-mentioned components, as long as the effects of the present invention are not impaired, further, as necessary, colorant, leuco dye, grease-sensitive resin, polymerization inhibitor, piperidine derivative compound, surface activity An agent, a plasticizer, etc. can be contained.

  In the photosensitive composition of the present invention, a colorant can be used in order 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, more preferably 0.1 to 4.0% by mass in the total mass of the solid content of the photosensitive 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.

  The photosensitive composition of the present invention can contain a leuco dye for the purpose of coloring the photosensitive layer and suppressing dissolution in the developer. As the leuco dye, a dye containing a lactone ring used in conventional heat-sensitive recording materials is preferable. 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 mass of the solid content of the photosensitive 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. When the content is 10% by mass or less, particularly 5% by mass or less, the non-image part (exposed part). ) Is particularly preferred since the developability is particularly improved.

Furthermore, the photosensitive composition of the present invention can contain a grease sensitive resin 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 content of the fat-sensitive resin is preferably 0.01 to 10% by mass, more preferably 0.05 to 10% by mass, in the total mass of the solid content of the photosensitive composition.

The photosensitive composition of the present invention, polymerizable ethylenically unsaturated compound having a double bond, i.e., it is desirable to include a small amount of thermal polymerization inhibitor for inhibiting 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-tert-butylphenol), N-nitrosophenylhydroxyamine primary cerium salt and the like. The content of the thermal polymerization inhibitor is preferably 0.01 to 5% by mass in the total mass of the solid content of the photosensitive composition. Further, if necessary, a higher fatty acid derivative such as behenic acid or behenic acid amide may be included to prevent polymerization inhibition by oxygen, and may be unevenly distributed on the surface of the layer in the course of drying after coating. . As for content of a higher fatty acid derivative, 0.5-10 mass% is preferable in the total mass of the solid content in a photosensitive composition.

The photosensitive composition of the present invention can contain a piperidine derivative compound for the purpose of improving storage stability with time. As piperidine derivative compounds, bis (1,2,2,6,6) pentamethyl-4-piperidyl [[3,5-bis (1,1-dimethylether) -4-hydroxyphenyl] methyl] butyl malonate, bis ( 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, 1,2-ethane-bis (N′-3, 3,5,5-tetramethyl-2-piperazinone).
These compounds are commercially available from BASF as TINUVIN 144, TINUVIN 292.
The content of the piperidine derivative is preferably 0.05 to 6.0% by mass, more preferably 1.0 to 5.0% by mass in the total mass of the solid content of the photosensitive composition.

The photosensitive composition of the present invention is described in JP-A-62-251740, JP-A-3-208514, and Japanese Patent Application No. 2006-241033 in order to broaden the processing stability against development conditions. Such nonionic surfactants, amphoteric surfactants described in JP-A-59-121044 and JP-A-4-13149 can be contained. Preferable examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether, fluorine surfactant 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 “Amorgen K” manufactured by Dai-ichi Kogyo Co., Ltd.) and the like. The content of the nonionic surfactant and the amphoteric surfactant is preferably 0.01 to 15% by mass, more preferably 0.01 to 10% by mass in the solid content of the photosensitive composition. When the content is 0.01% by mass or more, developability is particularly good. When the content exceeds 15% by mass, the strength of the image area may be weakened.

The photosensitive composition of this invention can also contain a plasticizer in order to provide the softness | flexibility etc. of a 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 plasticizer is preferably 0.01 to 10% by mass, more preferably 0.05 to 10% by mass, in the solid content of the photosensitive composition.

  A negative lithographic printing plate comprising a photosensitive layer formed using this photosensitive composition on a support can be provided. The lithographic printing plate precursor can usually be produced by dissolving the above-described components of the photosensitive composition in a solvent to form a photosensitive solution, and coating the photosensitive solution on an appropriate 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 solid content (total solid content including additives) of the photosensitive composition in the photosensitive solution 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 composition varies depending on the use, but is preferably 0.5 to 5.0 g / m ² at the time of drying, that is, with respect to the solid content of the photosensitive composition.

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 applied to the present invention is not specified, and conventionally known and used aluminum plates can be appropriately used. The thickness of the aluminum plate used in the present invention 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. As the electrolyte used for anodizing the aluminum plate, sulfuric acid, phosphoric acid, oxalic acid, chromic acid or a mixed acid thereof is generally used.

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.

More preferably, the lithographic printing plate precursor includes a photosensitive layer formed using the photosensitive composition on a support and a protective layer formed on the photosensitive layer.
The photosensitive layer of the lithographic printing plate precursor is a photopolymerization or heat-polymerizable negative photosensitive layer, and is usually exposed to the air in the atmosphere. A water-soluble protective layer is provided on the image recording layer for the purpose of preventing low molecular weight compounds such as oxygen and basic substances from entering the image recording layer. The water-soluble protective layer in the present invention requires low permeability of low-molecular compounds such as oxygen, and further does not substantially inhibit the transmission of light used for exposure, has excellent adhesion with the image recording layer, and It is desirable that it can be easily removed in the development process after exposure. Such a device relating to the protective layer has been conventionally made, and is described in detail in US Pat. No. 3,458,311 and JP-B-55-49729. As a material that can be used for the protective layer, for example, a water-soluble compound having relatively excellent crystallinity is preferably used. Specifically, polyvinyl alcohol, polyvinyl pyrrolidone, acidic celluloses, gelatin, gum arabic, polyacrylic acid Among these, water-soluble polymers such as those described above are known, but among these, the use of polyvinyl alcohol as a main component gives the best results in terms of basic properties such as oxygen barrier properties and development removability.

The polyvinyl alcohol used for the protective layer may be partially substituted with an ester, an ether and an acetal as long as it contains an unsubstituted vinyl alcohol unit for having necessary oxygen barrier properties and water solubility. Similarly, some of them may have other copolymer components. Specific examples of polyvinyl alcohol include those that are 71-100% hydrolyzed and have a molecular weight in the range of 200-3000. Specifically, Kuraray Co., Ltd. PVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST, PVA-HC, PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220, PVA-224, PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-405, PVA- 420, PVA-613, L-8, JT-05, JP-05, JF-17, manufactured by Nippon Vinegar Poval Co., Ltd., Gohsenol NL-05, NM-11, NM-, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 14, AL-06, P-610,
C-500 etc. are mentioned.

The components of the protective layer (selection of PVA, use of additives), coating amount, and the like are selected in consideration of fogging, adhesion, and scratch resistance in addition to oxygen barrier properties and development removability. In general, the higher the hydrolysis rate of the PVA used (the higher the content of the unsubstituted vinyl alcohol unit in the protective layer), the higher the film thickness, the higher the oxygen barrier property and the more advantageous in terms of sensitivity. However, when the oxygen barrier property is extremely increased, there arises a problem that unnecessary polymerization reaction occurs during production and raw storage, and unnecessary fogging and image line thickening occur during image exposure. In addition, adhesion to the image area and scratch resistance are extremely important in handling the plate. That is, when a hydrophilic layer made of a water-soluble polymer is laminated on an oleophilic photosensitive layer, film peeling due to insufficient adhesive force is likely to occur, and the peeled part causes defects such as poor film hardening due to inhibition of oxygen polymerization. On the other hand, various proposals have been made to improve the adhesion between these two layers. For example, US Patent Application No. 292501 and US Patent Application No. 44563 include an acrylic emulsion or a water-insoluble vinylpyrrolidone-vinyl acetate copolymer in a hydrophilic polymer mainly composed of polyvinyl alcohol. It is described that sufficient adhesiveness can be obtained by mixing 20 to 60% by weight and the like and laminating on the photosensitive layer. Any of these known techniques can be applied to the photosensitive layer composition of the present invention. Such a coating method of the protective layer is described in detail in, for example, US Pat. No. 3,458,311 and JP-B-55-49729. In the photosensitive composition of the present invention, polyvinyl alcohol and polyvinyl pyrrolidone are preferably used in combination from the viewpoints of adhesive strength, sensitivity, and unnecessary fog. The addition ratio (mass ratio) is preferably such that the ratio of polyvinyl alcohol: polyvinylpyrrolidone is 3: 1 or less, that is, the mixing ratio of PVP to PVA is 1/3 or less. The coating weight after drying of the water-soluble protective layer is preferably 1.0 to 3.0 g / m ² .

  The lithographic printing plate precursor according to the invention is not necessarily required to be adjacent to the photosensitive layer and the protective layer as long as it has a photosensitive layer and a protective layer thereon. An intermediate layer may be provided for the purpose of bonding the two.

  Improves detachability between plates when a large number of lithographic printing original plates of the present invention are stacked without interleaving paper, and also improves detachability between interleaving paper and plate even when interleaving interleaving paper Therefore, the surface of the protective layer of the lithographic printing original plate may be matted. As a method of matting the surface of the protective layer, a method of adding a matting agent or the like in the protective layer, a method of spray-coating a solution in which a water-soluble resin or a water-soluble resin and a matting agent are dissolved and dispersed on the surface of the protective layer and so on. Examples of the matting agent include silicon dioxide, zinc oxide, titanium oxide, alumina powder, starch, starch, polymer particles (for example, particles such as polyacrylic acid and polystyrene), and the like.

  Furthermore, other functions can be imparted to the protective layer. For example, the addition of a colorant (such as a water-soluble dye) that excels in the transmission of light of the wavelength used for exposure and can efficiently absorb light of a wavelength that does not contribute to image formation, without causing a decrease in sensitivity. -The safelight suitability in the visible region can be further enhanced.

  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 anionic surfactant include sulfates of alcohols having 8 to 22 carbon atoms (for example, polyoxyethylene alkyl sulfate soda salt), alkylaryl 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.

Although the synthesis example of a silane coupling agent and the Example using a photosensitive composition are shown below, this invention is not limited to these.
<Synthesis Example 1: Production of Silane Coupling Agent A belonging to General Formula II-1>
116 g of hydroxyethyl acrylate was charged into a 1 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer, and heated to 80 ° C. Into this, 205 g of 3-isocyanatopropyltrimethoxysilane was added dropwise and stirred at 80 ° C. for 4 hours. Thereafter, it was confirmed by IR measurement that the absorption peak derived from the isocyanate group of the raw material had completely disappeared and an absorption peak derived from the urethane bond was generated instead, and the reaction was terminated. The obtained reaction product was a colorless liquid and had a viscosity of 33 mm ² / s. The 1H-NMR spectrum data and IR spectrum of this compound are as follows.
¹ H NMR (300 MHz, CDCl ₃ , δ (ppm):
0.52 (t, 2H), 1.49 (m, 2H), 3.01 (m, 2H), 3.43 (s, 9H), 4.09 to 4.31 (m, 4H), 5 .73 (d, 1H), 6.02 (m, 1H), 6.30 (d, 1H)
IR spectrum (cm ⁻¹ ):
2945, 1727, 1532, 1410, 1246, 1192, 1084, 810

<Synthesis Example 2: Production of Silane Coupling Agent B belonging to General Formula II-5>
Into a 1 L separable flask equipped with a stirrer, reflux condenser, dropping funnel and thermometer, 524 g of dipentaerythritol pentaacrylate was charged and heated to 80 ° C. Into this, 205 g of 3-isocyanatopropyltrimethoxysilane was added dropwise and stirred at 80 ° C. for 4 hours. Thereafter, it was confirmed by IR measurement that the absorption peak derived from the isocyanate group of the raw material had completely disappeared and an absorption peak derived from the urethane bond was generated instead, and the reaction was terminated. The obtained reaction product was a pale yellow liquid and had a viscosity of 6270 mm ² / s. The 1H-NMR spectrum data and IR spectrum of this compound are as follows.
¹ H NMR (300 MHz, CDCl ₃ , δ (ppm):
0.57 (t, 2H), 1.56 (m, 2H), 3.08 (m, 2H), 3.28 to 3.46 (m, 4H), 3.52 (s, 9H), 3 .98 to 4.26 (m, 12H), 5.80 (m, 5H), 6.05 (m, 5H), 6.34 (m, 5H)
IR spectrum (cm ⁻¹ ):
2944, 1728, 1634, 1408, 1268, 1188, 1062, 984, 808

<Preparation of support>
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.

<Example 1>
Using the following silane coupling agent A, a photosensitive solution having the following composition was prepared. This photosensitive solution was applied on the aluminum plate as the support so that the film thickness after drying was 1.5 g / m ² and dried at 90 ° C. for 3 minutes to form a photosensitive layer. A water-soluble protective layer coating solution having the following composition is applied to the surface of the obtained photosensitive layer with a wire bar and dried at 90 ° C. for 3 minutes with a drying apparatus to form a protective film layer (the coating amount is 2. 0 g / m ² ), a lithographic printing plate precursor was obtained.
(Composition of photosensitive solution)
Silane coupling agent A (0.1 g)
Polymerizable compound (E-1) (0.6 g)
Specific alkali-soluble resin (A-1) (2.0 g)
Infrared absorber: Infrared absorber (1) (0.05 g)
Substituted or unsubstituted tetraphenylborate: 2-ethyl-4-methylimidazolium tetraphenylborate (0.1 g)
Radical polymerizable initiator: Triazine compound (T-7) (0.1 g)
Dye: Oil Blue 613 (manufactured by Orient Chemical Co., Ltd.) (0.05 g)
Solvent: Mixture of 20 ml of propylene glycol monomethyl ether and 20 ml of tetrahydrofuran (composition of water-soluble protective layer coating solution)
Polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., saponification degree 89 mol%, polymerization degree 500) 100 g
Surfactant (Japanese emulsifier, EMALEX 710) 0.03g
Distilled water 50g

<Example 2>
A lithographic printing plate precursor was obtained in the same manner as in Example 1 except that the silane coupling agent B (0.1 g) was used instead of the silane coupling agent A (0.1 g).

<Example 3>
As substituted or unsubstituted tetraphenylborate, tetraphenylphosphonium tetrakis (4-methylphenyl) borate (0.1 g) is used instead of 2-ethyl-4-methylimidazolium tetraphenylborate (0.1 g). A lithographic printing plate precursor was obtained in the same manner as in Example 1 except that it was used.
(Photosensitive solution C)

<Example 4>
As a substituted or unsubstituted tetraphenylborate, 1,5-diazabicyclo [4,3,0] -5-nonenetetra instead of 2-ethyl-4-methylimidazolium tetraphenylborate (0.1 g) A lithographic printing plate precursor was obtained in the same manner as in Example 1 except that phenyl borate (0.1 g) was used.

<Comparative Example 1>
A lithographic printing plate precursor was obtained in the same manner as in Example 1 except that the following comparative silane coupling agent (0.1 g) not belonging to the general formula II was used instead of the silane coupling agent A (0.1 g). .

<Comparative Example 2>
A lithographic printing plate precursor was obtained in the same manner as in Example 1 except that the following comparative alkali-soluble resin (2.0 g) was used instead of the alkali-soluble resin (A-1) (2.0 g).

<Comparative Example 3>
Example 1 except that the organic borate (B-6) (0.1 g) was used instead of the tetraphenylborate 2-ethyl-4-methylimidazolium tetraphenylborate (0.1 g). In the same manner, a lithographic printing plate precursor was obtained.

<Evaluation method>
The obtained lithographic printing plate precursor was evaluated as follows.
(1. Sensitivity evaluation)
The resulting lithographic printing plate precursor was exposed with a Trendsetter 800QTM manufactured by Creo at a resolution of 2400 dpi and an outer drum rotating speed of 360 rpm while changing the irradiation energy. After the exposure, a developer (HN-D) manufactured by Fuji Film Co., Ltd. was diluted 4 times and developed at 30 ° C. for 12 seconds using a PK-910II automatic developing machine. At this time, a halftone dot concentration meter iCplate II (manufactured by Gretag Macbeth Co., Ltd.) was used as the exposure sensitivity when the set value 50% flat screen reproduced 50.5 (± 0.5)% in the FM mode.

(2. FM screening test (image reproducibility))
Moreover, it exposed with FM Staccato36 by exposure energy 50mj / cm < ² > with the Trendsetter 800QTM by Creo company similarly to the above. After the exposure, a developer (HN-D) 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. At this time, using a halftone dot concentration meter iCplate II (manufactured by Gretag Macbeth Co.), it was confirmed that the set value 50% flat screen reproduced 50.5 (± 0.5)% in FM mode.

(3. Printing durability test)
In the same manner as described above, a halftone dot image in 1% increments from 1% to 100% obtained at an exposure energy of 50 mj / cm ² was printed on high-quality paper with a commercially available offset ink using a Ryobi printer. The printing was stopped each time 10,000 sheets were printed, and the image portion was enlarged with an electron micrograph, and the number of sheets until a dot image of one dot having a 20 μm square was missing was determined.

(4. Chemical resistance test)
In the same manner as above, a 50% halftone dot image obtained with an exposure energy of 50 mj / cm ² was dropped on Cyber 10 (Nikken Chemical Laboratories) for 30 minutes and wiped with absorbent cotton. ) (Made by Nichiban). Then peel off vigorously. Evaluation was based on how the image area was affected. In Table 1, a sample that did not peel at all was indicated by “◎”, a sample that peeled slightly, “Δ”, and a sample that completely peeled “×”.

(5. Safelight aptitude test in the ultraviolet and visible regions)
The exposed portion of the resulting lithographic printing plate precursor was exposed for 60 minutes every 5 minutes under an illuminance of 400 lux fluorescent lamp or UV cut fluorescent lamp. The irradiation part was shifted and the lithographic printing original plate was exposed for a maximum of 60 minutes. Next, a 50% halftone image was exposed at a resolution of 2400 dpi, an outer drum rotation speed of 360 rpm, and FM25 with a Kodak Trendsetter 800 Quantum. The exposure energy at this time is assumed to be 50.5 (± 0.5)% when the FM mode set value 50% flat screen is reproduced in sensitivity evaluation. Thereafter, development was performed at 30 ° C. for 25 seconds with the above developing solution using a PK-1310 II automatic developing machine. In the evaluation, if the exposure site by the fluorescent lamp was an FM halftone densitometer and the halftone dot concentration obtained by the FM screening test was within 0.5%, the evaluation was accepted.

(6. Storage stability test)
The obtained lithographic printing original plate was stored in an overlapping manner under forced storage conditions at 60 ° C. and 5% humidity for 16 days without sandwiching the slip sheet. Thereafter, the lithographic printing plate precursor was converted to a resolution of 2400 dpi, outer drum rotation speed 360 rpm, FM mode setting value 50% by the above-mentioned sensitivity evaluation, and 50.5 (± 0.5)% of the flat screen by a Kodak Trendsetter 800 Quantum. The exposure was performed with the same irradiation energy as that reproduced. Then, it developed with the said developing solution at 30 degreeC for 25 second using PK-1310 II self-supporting machine. The evaluation was deemed acceptable if the 50% flat screen portion was within 0.5% of the AM halftone densitometer compared to before storage.

As is apparent from Table 1, according to the thermal negative printing plate provided with a photosensitive layer containing a novel silane coupling agent and a specific alkali-soluble resin in the photosensitive composition of the present invention, both are highly sensitive and FM screening images. A lithographic printing plate precursor excellent in reproducibility, in addition to printing durability and chemical resistance in a minute image area, as well as safelight suitability and storage stability in the ultraviolet / visible region was provided.

Claims (7)

Formula (I)

(In the above formula, R ¹ and R ² represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent, and L ¹ and L ² may have ¹ substituent. Represents an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 15 carbon atoms which may have a substituent.)
An alkali-soluble resin having a monomer unit represented by the following general formulas (II-1) to (II-5):

(In the above formula, R ³ independently represents a hydrogen atom or a methyl group, X independently represents an alkoxy group having 1 to 4 carbon atoms, and n is independently an integer of 1 to 3).
At least one silane coupling agent selected from the group represented by: an infrared absorber; tetraphenylborate in which the phenyl group may be substituted; and radical polymerization initiation that is not tetraphenylborate A photosensitive composition containing at least an agent and a polymerizable compound having an ethylenic double bond.   The photosensitive composition of Claim 1 contained in the range of 0.5-8.0 mass% in the solid content of the said photosensitive composition from which the said silane coupling agent will form a photosensitive layer. The alkali-soluble resin is represented by the following general formula (III) or the following general formula (IV):

(In the above formula, R ⁴ and R ⁵ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent, and M represents an alkylene having 1 to 10 carbon atoms which may have a substituent. Group.)
The photosensitive composition of Claim 1 or 2 which further contains the monomer unit represented by these.   The tetraphenylborate is 2-ethyl-4-methylimidazolium tetraphenylborate, 1,5-diazabicyclo [4,3,0] -5-nonenetetraphenylborate, and tetraphenylphosphonium tetrakis (4-methyl). The photosensitive composition according to claim 1, which is at least one selected from phenyl) borate.   The said tetraphenyl borate is contained in the range of 3.0-6.0 mass% in solid content of the said photosensitive composition which will form a photosensitive layer. Photosensitive composition.   A negative lithographic printing plate precursor comprising a support and a photosensitive layer formed on the support using the photosensitive composition according to any one of claims 1 to 5. The negative lithographic printing plate precursor according to claim 6, further comprising a protective layer formed on the photosensitive layer.