JP5448882B2 - Planographic printing plate precursor and plate making method - Google Patents

Description

  The present invention relates to a lithographic printing plate precursor and a plate making method using the same. More specifically, the present invention relates to a lithographic printing plate precursor that can be directly made by laser image exposure and a plate making method for developing the lithographic printing plate precursor on-press.

In general, a lithographic printing plate comprises an oleophilic image area that receives ink in the printing process and a hydrophilic non-image area that receives dampening water. Lithographic printing utilizes the property that water and oil-based inks repel each other, so that the oleophilic image area of the lithographic printing plate is the ink receiving area, and the hydrophilic non-image area is dampened with the water receiving area (ink non-receiving area). In this method, a difference in ink adhesion is caused on the surface of the lithographic printing plate, and after ink is applied only to the image area, the ink is transferred to a printing medium such as paper and printed.
In order to produce this lithographic printing plate, conventionally, a lithographic printing plate precursor (PS plate) in which an oleophilic photosensitive resin layer (image recording layer) is provided on a hydrophilic support is used. After exposure through a mask such as a film, development with an alkaline developer is performed to leave the image recording layer corresponding to the image area, and dissolve and remove the unnecessary image recording layer corresponding to the non-image area. And obtained a lithographic printing plate.

  Due to recent advances in this field, lithographic printing plates are now available with CTP (computer to plate) technology. That is, a lithographic printing plate can be obtained by scanning and exposing a lithographic printing plate precursor directly using a laser or a laser diode without a lith film, and developing it.

  Along with the above progress, problems related to the lithographic printing plate precursor have been changed to improvements in image formation characteristics, printing characteristics, physical characteristics and the like corresponding to the CTP technology. In addition, due to increasing interest in the global environment, environmental issues related to waste liquids associated with wet processing such as development processing have been highlighted as another issue related to lithographic printing plate precursors.

For the above environmental problems, simplification and no processing of development or plate making are directed. A method using polarity conversion of the image recording layer is known as a process for making the plate making non-processed. For example, Patent Document 1 discloses an image forming method in which an image forming element including a polymer binder containing a betaine side chain is subjected to thermal image formation and immediately treated with dampening water and ink without a development step. In this method, the surface of the image recording layer receives fountain solution before the thermal image formation, but after the thermal image formation, the fountain solution is repelled and becomes ink-receptive, so that it is not necessary to remove the image recording layer.
Further, as one simple plate making method, a method called “on-press development” is performed. That is, after the exposure of the lithographic printing plate precursor, conventional development is not performed, but it is mounted on a printing machine as it is, and unnecessary portions of the image recording layer are removed at the initial stage of a normal printing process.

  In the simplification of the plate making operation as described above, a system using a lithographic printing plate precursor and a light source that can be handled in a bright room or under a yellow light is preferable in terms of ease of work. A solid-state laser such as a semiconductor laser or a YAG laser emitting an infrared ray of 1200 nm is used. Further, a UV laser can be used.

  As a lithographic printing plate precursor capable of on-press development, for example, in Patent Documents 2 and 3, a lithographic printing plate having an image recording layer (thermosensitive layer) containing a microcapsule containing a polymerizable compound on a hydrophilic support. The original edition is listed. In Patent Document 2, it is proposed to utilize the fact that the outer wall of the microcapsule is broken by heat used for image formation and a thermally reactive compound such as a polymerizable compound comes out of the capsule. Patent Document 4 describes a lithographic printing plate precursor in which an image recording layer (photosensitive layer) containing an infrared absorber, a radical polymerization initiator, and a polymerizable compound is provided on a support. Furthermore, Patent Document 5 has a polymer binder containing a polymerizable compound and a graft polymer having a polyethylene oxide chain as a side chain on a support, and the binder is suspended in the polymerizable composition. An on-press developable lithographic printing plate precursor provided with an image recording layer, which is characterized by being present as discrete particles, is described.

  The image forming method using such a polymerization reaction has improved the printing durability compared to the image forming method in which thermoplastic hydrophobic polymer fine particles are coalesced (fused) with heat. From the practical point of view, the on-press developability, stain resistance and printing durability are not yet sufficient.

Special table 2008-509245 gazette JP 2001-277740 A JP 2001-277742 A JP 2002-287334 A JP 2009-234268 A

  The object of the present invention is that image recording by laser exposure is possible, it has good on-machine developability, is excellent in stain resistance, and has excellent resistance to resistance compared with the case of using conventional radical polymerization. An on-press development type lithographic printing plate precursor having printability and a lithographic printing method using the lithographic printing plate precursor.

1. On the support, (A) a polymer compound having a side chain containing a betaine structure, (B) an infrared absorber, (C) a polymerization initiator, and (D) an ethylenically unsaturated polymerizable compound, and printing A lithographic printing plate precursor comprising an image recording layer which can be removed by ink and / or fountain solution.
2. 2. The lithographic printing plate precursor as described in 1 above, wherein the polymer compound is organic polymer fine particles.
3. 2. The lithographic printing plate precursor as described in 1 above, wherein the polymer compound is a binder, and the image recording layer further comprises (E) organic fine particles.
4). 4. The lithographic printing plate precursor as described in 3 above, wherein the organic fine particles are microcapsules or microgels.
5. The lithographic printing plate precursor as described in any one of 1 to 4 above, wherein the betaine structure is carbobetaine, sulfobetaine, or phosphobetaine.
6). 6. The lithographic printing plate precursor as described in 5 above, wherein the betaine structure is carbobetaine or sulfobetaine.
7). The lithographic printing plate precursor as described in any one of 1 to 5 above, wherein the polymer compound comprises at least one monomer unit selected from the following general formulas (1) to (4).

(In the above formula, R ₁ , R ₄ , R ₇ and R ₁₀ each independently represent a hydrogen atom, a halogen atom or a substituent having 1 to 12 carbon atoms, and L ₁ , L ₂ , L ₃ and L ₄ are Each independently represents a single bond or a divalent linking group, X ₁ represents an alkylene group, a substituted alkylene group, or a divalent linking group having a polyalkylene oxide group, and Y ₁ represents an alkylene group or a substituted alkylene group. , R ₂ , R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ , R ₁₂ and R ₁₃ are each independently an alkyl group having 1 to 6 carbon atoms which may have a substituent, Represents an alkenyl group, an alkynyl group, a cycloalkyl group or an aryl group (R ₂ , R ₃ and Y ₁ ), (R ₅ , R ₆ and Y ₁ ), (R ₈ , R ₉ and Y ₁ ), and ( R ₁₁ to R ₁₃ and responsibility in each group _{Y 1)} Two members to the may form a heterocyclic ring.)

8). In the general formulas (1) and (2), R ₁ and R ₄ each independently represent a hydrogen atom or a methyl group, and L ₁ and L ₂ each independently represent —COO—, —OCO—, —O—. , —CO—NR ₁₄ — or a phenylene group, R ₁₄ is a hydrogen atom, or an optionally substituted alkyl group, cycloalkyl group, aryl group or aralkyl group having 1 to 12 carbon atoms. The lithographic printing plate precursor as described in 7 above, wherein
9. The lithographic printing plate precursor as described in any one of 1 to 8 above, wherein the polymer compound comprises a monomer unit represented by the following general formula (5).

(In the above formula, R ₁₅ represents a hydrogen atom, a halogen atom, or a substituent having 1 to 12 carbon atoms, and R ₁₆ represents a group having an ester group, an amide group, a cyano group, a hydroxy group, or an aryl group. .)

10. In the general formula (5), R ₁₅ is a hydrogen atom or methyl, and R ₁₆ is an ester group, an amide group, a cyano group, or a group having a phenyl group which may have a substituent. The lithographic printing plate precursor as described in 9 above.
11. The lithographic printing plate precursor as described in 9 or 10 above, wherein in the general formula (5), R ₁₆ contains a polyalkyleneoxy group.
12 1 to 11 above, wherein the polymer compound further comprises a monomer unit having at least one ethylenically unsaturated polymerizable group represented by the following general formulas (6) to (8) in the side chain. The lithographic printing plate precursor as described in any one of the above items.

(In the formula, X and Y each independently represent an oxygen atom or —N (R ₂₈ ) —. Z represents an oxygen atom, —N (R ₂₈ ) — or a phenylene group. R _{17 to} R ₂₈ each represent Independently represents a monovalent substituent)

13. The lithographic printing plate precursor as described in any one of 1 to 12 above, further comprising a protective layer on the image recording layer.
14 The lithographic printing plate precursor as described in 13 above, wherein the protective layer contains an inorganic stratiform compound.
15. The lithographic printing plate precursor as described in any one of 1 to 14 above is image-exposed with an infrared laser and then mounted on a printing machine, or is mounted on a printing machine and image-exposed with an infrared laser and printed on the lithographic printing plate precursor A method for making a lithographic printing plate precursor by supplying ink and fountain solution to remove unexposed portions of the image recording layer.

In the present invention, the above-described problem can be solved by including a polymer compound having a side chain containing a betaine structure in an image recording layer for forming an image using a polymerization reaction.
Although the mechanism of action of the present invention is not clear, the following is presumed. In the unexposed area, the interaction with the fountain solution is improved by the high hydrophilicity of the betaine structure introduced into the polymer compound, and the presence of the organic polymer fine particles can give good on-machine developability, In addition, the stain resistance was improved. Furthermore, the printing durability was greatly improved unexpectedly, because not only the monomer unit having a betaine structure was thermally decomposed and hydrophobized in the exposed area, but also the dampening water permeability was lowered. It is presumed that the decomposition product contains radical chemical species to promote radical polymerization and increase the curability of the image.

  According to the present invention, an on-press development type lithographic plate having good on-press developability, excellent stain resistance, and very excellent printing durability compared to the case of using conventional radical polymerization. A print version can be provided.

  The components and components of the lithographic printing plate precursor according to the invention will be described below.

[Lithographic printing plate precursor]
The lithographic printing plate precursor according to the invention is characterized in that it contains at least the following (A) to (D) on a support and has an image recording layer that can be removed by printing ink and / or fountain solution.
(A) Polymer compound having a side chain containing a betaine structure (B) Infrared absorber (C) Polymerization initiator (D) Ethylenically unsaturated polymerizable compound Thereby, it has good on-press developability, Moreover, an on-press development type lithographic printing plate precursor having excellent stain resistance and further excellent printing durability as compared with the case of using conventional radical polymerization can be obtained.

(A) Polymer compound having side chain containing betaine structure (a1) Monomer unit having betaine structure The betaine structure of the polymer compound used in the image recording layer is carbobetaine, sulfobetaine or phosphobetaine. Is preferred. Specifically, the polymer compound preferably includes any of monomer units represented by the following general formulas (1) to (4).

In the above formula, R ₁ , R ₄ , R ₇ and R ₁₀ each independently represent a hydrogen atom, a halogen atom or a substituent having 1 to 12 carbon atoms, and L ₁ , L ₂ , L ₃ and L ₄ are each Independently represents a single bond or a divalent linking group, X ₁ represents an alkylene group, a substituted alkylene group, or a divalent linking group having a polyalkylene oxide group, Y ₁ represents an alkylene group or a substituted alkylene group, R ₂ , R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ , R ₁₂ and R ₁₃ are each independently an alkyl group having 1 to 6 carbon atoms which may have a substituent, alkenyl Represents a group, an alkynyl group, a cycloalkyl group or an aryl group. Any of the groups (R ₂ , R ₃ and Y ₁ ), (R ₅ , R ₆ and Y ₁ ), (R ₈ , R ₉ and Y ₁ ), and (R _{11 to} R ₁₃ and Y ₁ ) May be combined to form a heterocyclic ring.

As the substituents that each group as R ₂ , R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ , R ₁₂ and R ₁₃ and the alkylene group as X ₁ and Y ₁ may have, , Alkyl group, aryl group, heteroaryl group, alkenyl group, alkynyl group, aralkyl group, halogen atom, hydroxy group, alkoxy group, aryloxy group, mercapto group, alkylthio group, arylthio group, alkyldithio group, amino group, acyloxy group , Carbamoyloxy group, sulfoxy group, ureido group, oxycarbonylamino group, formyl group, acyl group, carbonyl group, oxycarbonyl group, carbamoyl group, sulfinyl group, sulfonyl group, sulfo group (—SO ₃ H) and its conjugate base Groups (hereinafter referred to as sulfonate groups), sulfinamoyl groups, phosphono groups (—PO ₃ H ₂ ) and its conjugate base group (hereinafter referred to as phosphonate group), phosphonooxy group (—OPO ₃ H ₂ ) and its conjugate base group (hereinafter referred to as phosphonateoxy group), cyano group, nitro group, etc. Is mentioned.

  In order for the printed matter to exhibit good stain resistance, among the general formulas (1) to (4), the monomer unit represented by the general formula (1) or the general formula (2) is preferable.

Preferred embodiments in the above formula are shown below.
R ₁ , R ₄ , R ₇ and R ₁₀ are preferably independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Is more preferable, and a hydrogen atom or a methyl group is most preferable.
L ₁ , L ₂ , L ₃ and L ₄ are each independently a single bond, —COO—, —OCO—, —CO—, —O—, —CO—NR ₁₄ —, —NR ₁₄ —CO—, divalent Is preferably a single bond, —COO—, —OCO—, —CO—, —O—, —CO—NR ₁₄ —, or an arylene group. It is more preferable that it is —COO—, —OCO—, —O—, —CO—NR ₁₄ — or a phenylene group.
R ₁₄ is a hydrogen atom or an alkyl group, cycloalkyl group, aryl group or aralkyl group having 1 to 12 carbon atoms which may have a substituent, and has a hydrogen atom or a substituent. It is more preferably an alkyl group, a cycloalkyl group or an aryl group having 1 to 6 carbon atoms, which is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent. More preferably.

X ₁ is an optionally substituted alkylene group having 1 to 12 carbon atoms, or — (CH ₂ CH ₂ —O) _n —, — (CH (CH ₃ ) CH ₂ —O). _n -, or _- is preferably an alkylene group having 1 to 10 carbon atoms a divalent linking group containing a polyalkylene oxide group represented by _{- (CH 2 CH (CH 3} ) -O) n Or a divalent linking group containing a polyethylene oxide group represented by — (CH ₂ CH ₂ —O) _n —, which is an alkylene group having 1 to 8 carbon atoms, or — Most preferably, it is a divalent linking group containing a polyethylene oxide group represented by (CH ₂ CH ₂ —O) _n —.
Here, n is preferably 1 to 50, more preferably 1 to 30, and particularly preferably 1 to 10. Here, n may be single or a mixture of a plurality of types, and in the case of a mixture, n represents an average value.

Y ₁ is preferably an alkylene group having 1 to 12 carbon atoms which may have a substituent, more preferably an alkylene group having 1 to 8 carbon atoms which may have a substituent, Particularly preferred is an alkylene group having 1 to 6 carbon atoms.
Are R ₂ , R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ , R ₁₂ and R ₁₃ independently an alkyl group having 1 to 3 carbon atoms that may have a substituent? Or (R ₂ , R ₃ and Y ₁ ), (R ₅ , R ₆ and Y ₁ ), (R ₈ , R ₉ and Y ₁ ), and (R _{11 to} R ₁₃ and Y ₁ ) It is preferably a 5- or 6-membered heterocyclic ring in which any _two of R ₂ , R ₂ , R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ , R ₁₂ and R ₁₃ are independent. Methyl groups or ethyl groups, or (R ₂ , R ₃ and Y ₁ ), (R ₅ , R ₆ and Y ₁ ), (R ₈ , R ₉ and Y ₁ ), and (R _{11 to} R More preferably, any two of each group of ₁₃ and Y ₁ ) are bonded to form a pyrrolidine ring or a piperidine ring.

Below, the preferable example of the monomer unit which has a betaine structure in a side chain is given. In the formula, R represents a hydrogen atom or a methyl group, L represents —COO— or —CONH—, X ₁ , X ₂ and X ₃ independently represent a methyl group or an ethyl group, and l represents 1 to 10 An integer is represented, m represents an integer of 1 to 8, and n represents an integer of 1 to 6. )

  More specific examples include the following structures, but the present invention is not limited to these.

  As for the monomer unit having a side chain containing a betaine structure, only one type may be used in the polymer compound according to the present invention, or two or more types may be included. The monomer unit containing these betaine structures is preferably contained in the polymer compound in an amount of 5 to 70% by mass, and 5 to 60% by mass from the viewpoint of on-press developability and stain resistance of non-image areas. More preferably, it is the range of 8-50 mass%.

(A2) Other monomer units constituting the polymer compound The polymer compound of the present invention contains a monomer unit represented by the following general formula (5) in addition to the monomer unit having the betaine structure in the side chain. Is preferred.

In the above formula, R ₁₅ represents a hydrogen atom, a halogen atom, or a substituent having 1 to 12 carbon atoms, and R ₁₆ represents a group having an ester group, an amide group, a cyano group, a hydroxy group, or an aryl group.

Preferred embodiments in the above formula are shown below.
R ₁₅ is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and a hydrogen atom or a methyl group. Is most preferred.
R ₁₆ is preferably an ester group, an amide group, a cyano group or a phenyl group which may have a substituent. Substituents include alkyl groups, aryl groups, heteroaryl groups, alkenyl groups, alkynyl groups, aralkyl groups, halogen atoms, hydroxy groups, alkoxy groups, aryloxy groups, mercapto groups, alkylthio groups, arylthio groups, alkyldithio groups, amino groups. Group, acyloxy group, carbamoyloxy group, sulfoxy group, ureido group, oxycarbonylamino group, formyl group, acyl group, carbonyl group, oxycarbonyl group, carbamoyl group, sulfinyl group, sulfonyl group, sulfo group (—SO ₃ H) And its conjugate base group (hereinafter referred to as sulfonate group), sulfinamoyl group, phosphono group (—PO ₃ H ₂ ) and its conjugate base group (hereinafter referred to as phosphonate group), phosphonooxy group (—OPO ₃ H _2). ) And its conjugate base group (hereinafter referred to as phosphine) Referred to as Natookishi group), a cyano group, a nitro group, and the like.

Specific examples of the monomer corresponding to the monomer unit of the general formula (5) include styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, methacrylonitrile, vinyl carbazole. And acrylate or methacrylate having a polyalkylene structure. Among these, styrene, acrylonitrile and methyl methacrylate are particularly preferable.
The polymer compound in the present invention may contain a plurality of monomer units from these.
These monomer units are preferably contained in the polymer compound in an amount of 30 to 95% by mass, more preferably 40 to 95% by mass, and most preferably in the range of 50 to 92% by mass. is there.

In the polymer compound of the present invention, good on-press developability can be achieved when R _{16 in the} general formula (5) contains a polyalkyleneoxy group. The polyalkyleneoxy group is preferably a polyethyleneoxy group or a polypropyleneoxy group, and particularly preferably a polyethyleneoxy group. Here, the number of repeating units of the alkyleneoxy group is preferably 1 to 100, more preferably 2 to 80, and particularly preferably 4 to 50.
Although the preferable example of such a monomer unit is shown below, this invention is not limited to these.

(In the formula, n represents an integer of 1 to 50, and R ₁ and R ₂ independently represent a hydrogen atom or a methyl group.)

  More specific examples include the following structures, but the present invention is not limited to these.

  The monomer unit having a side chain containing a polyalkyleneoxy group is preferably contained in the polymer compound in an amount of 1 to 70% by mass, more preferably 2 to 50% by mass, and 3 to 40%. It is particularly preferable that it is contained by mass%.

Furthermore, the polymer compound used in the present invention preferably has an ethylenically unsaturated polymerizable group in the side chain in order to improve the film strength of the image area. In particular, R _{16 in the} general formula (5) is more preferably a group containing an ethylenically unsaturated polymerizable group selected from the following general formulas (6) to (8).
These groups can be introduced into the polymer by polymer reaction or copolymerization. For example, a reaction between an acrylic polymer or polyurethane having a carboxy group in the side chain and polyurethane and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be used.

(In the formula, X and Y each independently represents an oxygen atom or —N (R ₂₈ ) —. Z represents an oxygen atom, —N (R ₂₈ ) — or a phenylene group. R _{17 to} R ₂₈ each represent Independently represents a hydrogen atom or a monovalent substituent.)

  The content of ethylenically unsaturated polymerizable groups in the polymer compound (content of unsaturated double bond capable of radical polymerization by iodine titration) is preferably 0.1 to 10.0 mmol per gram of polymer compound, More preferably, it is 1.0-7.0 mmol, Most preferably, it is 2.0-5.5 mmol. Within this range, good sensitivity and good storage stability can be obtained.

  Specific examples of the monomer unit having an ethylenically unsaturated polymerizable group in the side chain include, for example, the structures shown below, but the present invention is not limited thereto.

  The polymer compound of the present invention has a monomer unit having a sulfonamide group in the side chain in order to satisfy developability, non-image portion fine line reproducibility, suppression of residue generation, and printing durability when using UV ink. It may be copolymerized. Specific examples of the monomer for such a monomer unit include compounds described in paragraph numbers [0024] to [0027] of JP-A No. 2009-241258.

  In addition, a lipophilic group such as an alkyl group, an aryl group, an aralkyl group, or an alkenyl group can be introduced into the polymer compound of the present invention in order to control the inking property. Specifically, a lipophilic group-containing monomer such as an alkyl methacrylate may be copolymerized.

  The polymer compound in the present invention preferably has a mass average molar mass (Mw) of 2000 or more, more preferably 5000 or more, and still more preferably 10,000 to 300,000.

The polymer compound of the present invention may be present as a binder or polymer fine particles as an existing form in the image recording layer. When present as fine particles, the average particle size is preferably 0.01 to 3.0 μm.
The content of the polymer compound in the image recording layer is from 5 to 90% by mass, preferably from 5 to 80% by mass, more preferably from 10 to 70% by mass, based on the total solid content of the image recording layer. preferable.

  Specific examples of the polymer compound in the present invention are listed in the following table, but are not limited thereto. The mass average molar mass (Mw) in the table is measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

(B) Infrared Absorber The infrared absorbent has a function of converting absorbed infrared light into heat and a function of exciting with infrared light to transfer electrons and / or energy to a polymerization initiator described later. The infrared absorber used in the present invention is a dye having an absorption maximum at a wavelength of 760 to 1200 nm.

As the dye, commercially available dyes and known dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Is mentioned.
Particularly preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further, cyanine dyes and indolenine cyanine dyes are preferred, and particularly preferred examples include cyanine dyes represented by the following general formula (a).

In the general formula (a), X ¹ represents a hydrogen atom, a halogen ^{atom, -N (R 9) (R} 10), - X ² -L ¹ or a group shown below. Here, R ⁹ and R ¹⁰ may be the same or different and each may have a substituent, an aryl group having 6 to 10 carbon atoms, an alkyl group having 1 to 8 carbon atoms, a hydrogen atom R ⁹ and R ¹⁰ may be bonded to each other to form a ring. Of these, a phenyl group is preferred (—NPh ₂ ). X ² represents an oxygen atom or a sulfur atom, and L ¹ represents a hydrocarbon group having 1 to 12 carbon atoms, a heteroaryl group, or a hydrocarbon group having 1 to 12 carbon atoms including a hetero atom. In addition, a hetero atom here shows N, S, O, a halogen atom, and Se. In the group shown below, Xa ^- has Za described later ^- is defined as for, R ^a represents a hydrogen atom, an alkyl group, an aryl group, a substituted or unsubstituted amino group, substituted or unsubstituted amino group and a halogen atom .

R ¹ and R ² each independently represents a hydrocarbon group having 1 to 12 carbon atoms. From the storage stability of the image recording layer coating solution, R ¹ and R ² are preferably hydrocarbon groups having 2 or more carbon atoms. R ¹ and R ² may be connected to each other to form a ring, and when forming a ring, it is particularly preferable to form a 5-membered ring or a 6-membered ring.

Ar ¹ and Ar ² may be the same or different and each represents an aryl group which may have a substituent. Preferred aryl groups include a benzene ring and a naphthalene ring. Moreover, as a preferable substituent, a C12 or less hydrocarbon group, a halogen atom, and a C12 or less alkoxy group are mentioned. Y ¹ and Y ² may be the same or different and each represents a sulfur atom or a dialkylmethylene group having 12 or less carbon atoms. R ³ and R ⁴ may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferred substituents include alkoxy groups having 12 or less carbon atoms, carboxy groups, and sulfo groups. R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 12 or less carbon atoms. From the availability of raw materials, a hydrogen atom is preferred. Za ⁻ represents a counter anion. However, Za ⁻ is not necessary when the cyanine dye represented by formula (a) has an anionic substituent in its structure and charge neutralization is not necessary. Preferred Za ⁻ is a halide ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ion, particularly preferably a perchlorate ion, in view of the storage stability of the image recording layer coating solution. , Hexafluorophosphate ions, and aryl sulfonate ions.

Specific examples of the cyanine dye represented by formula (a) that can be suitably used include compounds described in paragraphs [0017] to [0019] of JP-A No. 2001-133969, and JP-A No. 2002-023360. Paragraph numbers [0016] to [0021] of JP-A No. 2002-040638, compounds described in paragraph Nos. [0012] to [0037] of JP-A No. 2002-040638, preferably paragraph Nos. [0034] of JP-A No. 2002-278057 [0041], compounds described in paragraph numbers [0080] to [0086] of JP 2008-195018 A, most preferably compounds described in paragraph numbers [0035] to [0043] of JP 2007-90850 A Is mentioned.
In addition, compounds described in paragraph numbers [0008] to [0009] of JP-A No. 5-5005 and paragraph numbers [0022] to [0025] of JP-A No. 2001-222101 can also be preferably used.

  Moreover, these infrared absorbers may use only 1 type, may use 2 or more types together, and may use infrared absorbers other than infrared absorbers, such as a pigment, together. As the pigment, compounds described in paragraph numbers [0072] to [0076] of JP-A-2008-195018 are preferable.

  The content of the infrared absorber in the image recording layer in the present invention is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 5.0% by mass of the total solid content of the image recording layer.

(C) Polymerization initiator The (C) polymerization initiator used in the present invention is a compound that initiates and accelerates the polymerization of (D) an ethylenically unsaturated polymerizable compound. As the polymerization initiator that can be used in the present invention, a radical polymerization initiator is preferable, and a known thermal polymerization initiator, a compound having a bond with a small bond dissociation energy, a photopolymerization initiator, and the like can be used.

  Examples of the radical polymerization initiator in the present invention include (a) an organic halide, (b) a carbonyl compound, (c) an azo compound, (d) an organic peroxide, (e) a metallocene compound, and (f) an azide compound. (G) hexaarylbiimidazole compound, (h) organic borate compound, (i) disulfone compound, (j) oxime ester compound, (k) onium salt compound.

  (A) As the organic halide, compounds described in paragraph numbers [0022] to [0023] of JP-A-2008-195018 are preferable.

  (B) As the carbonyl compound, compounds described in paragraph [0024] of JP-A-2008-195018 are preferable.

  (C) As the azo compound, for example, an azo compound described in JP-A-8-108621 can be used.

  (D) As the organic peroxide, for example, compounds described in paragraph [0025] of JP-A-2008-195018 are preferable.

  As the (e) metallocene compound, for example, the compound described in paragraph [0026] of JP-A-2008-195018 is preferable.

(F) Examples of the azide compound include 2,6-bis (4-azidobenzylidene) -4-methylcyclohexanone.
(G) As the hexaarylbiimidazole compound, for example, a compound described in paragraph [0027] of JP-A-2008-195018 is preferable.

  (H) As the organic borate compound, for example, a compound described in paragraph [0028] of JP-A-2008-195018 is preferable.

  (I) Examples of the disulfone compound include compounds described in JP-A No. 61-166544.

  (J) As the oxime ester compound, for example, compounds described in paragraph numbers [0028] to [0030] of JP-A-2008-195018 are preferable.

  (K) Examples of the onium salt compounds include S.I. I. Schlesinger, Photogr. Sci. Eng. , 18, 387 (1974), T.A. S. Bal et al, Polymer, 21, 423 (1980), diazonium salts described in JP-A-5-158230, ammonium described in US Pat. No. 4,069,055, JP-A-4-365049, and the like. Salt, phosphonium salts described in U.S. Pat. Nos. 4,069,055 and 4,069,056, EP 104,143, U.S. Patent Application Publication No. 2008/0311520 JP-A-2-150848, JP-A-2008-195018, or J.P. V. Ivonium salt described in Crivello et al, Macromolecules, 10 (6), 1307 (1977), European Patents 370,693, 233,567, 297,443, 297,442, US Patent 4,933,377, 4,760,013, 4,734,444, 2,833,827, German Patent 2,904,626, 3,604,580 Sulphonium salts described in the respective specifications of U.S. Pat. V. Crivello et al, J.A. Polymer Sci. , Polymer Chem. Ed. , 17, 1047 (1979), a selenonium salt described in C.I. S. Wen et al, Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988), and onium salts such as azinium salts described in JP-A-2008-195018.

  Of these, more preferred are onium salts, especially iodonium salts, sulfonium salts and azinium salts. Although the specific example of these compounds is shown below, it is not limited to this.

  As an example of the iodonium salt, a diphenyl iodonium salt is preferable, and a diphenyl iodonium salt substituted with an electron donating group such as an alkyl group or an alkoxyl group is particularly preferable, and an asymmetric diphenyl iodonium salt is more preferable. Specific examples include diphenyliodonium = hexafluorophosphate, 4-methoxyphenyl-4- (2-methylpropyl) phenyliodonium = hexafluorophosphate, 4- (2-methylpropyl) phenyl-p-tolyliodonium = hexa. Fluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium = tetrafluoroborate, 4-octyloxy Phenyl-2,4,6-trimethoxyphenyliodonium = 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, bis ( -t- butylphenyl) iodonium tetraphenylborate and the like.

  Examples of sulfonium salts include triphenylsulfonium = hexafluorophosphate, triphenylsulfonium = benzoylformate, bis (4-chlorophenyl) phenylsulfonium = benzoylformate, bis (4-chlorophenyl) -4-methylphenylsulfonium = Examples thereof include tetrafluoroborate, tris (4-chlorophenyl) sulfonium = 3,5-bis (methoxycarbonyl) benzenesulfonate, and tris (4-chlorophenyl) sulfonium = hexafluorophosphate.

  Examples of azinium salts include 1-cyclohexylmethyloxypyridinium = hexafluorophosphate, 1-cyclohexyloxy-4-phenylpyridinium = hexafluorophosphate, 1-ethoxy-4-phenylpyridinium = hexafluorophosphate, 1-cyclohexyl (2-ethylhexyloxy) -4-phenylpyridinium = hexafluorophosphate, 4-chloro-1-cyclohexylmethyloxypyridinium = hexafluorophosphate, 1-ethoxy-4-cyanopyridinium = hexafluorophosphate, 3,4 -Dichloro-1- (2-ethylhexyloxy) pyridinium = hexafluorophosphate, 1-benzyloxy-4-phenylpyridinium = hexafluorophosphate, 1-phenethylo Ci-4-phenylpyridinium = hexafluorophosphate, 1- (2-ethylhexyloxy) -4-phenylpyridinium = p-toluenesulfonate, 1- (2-ethylhexyloxy) -4-phenylpyridinium = perfluorobutanesulfonate 1- (2-ethylhexyloxy) -4-phenylpyridinium bromide, 1- (2-ethylhexyloxy) -4-phenylpyridinium tetrafluoroborate.

  The polymerization initiator is preferably added in an amount of 0.1 to 50% by mass, more preferably 0.5 to 30% by mass, and particularly preferably 0.8 to 20% by mass with respect to the total solid content of the image recording layer. be able to. Within this range, good sensitivity and good stain resistance of the non-image area during printing can be obtained.

(D) Ethylenically unsaturated polymerizable compound The ethylenically unsaturated polymerizable compound used for the image recording layer in the present invention is an addition polymerizable compound having at least one ethylenically unsaturated double bond, and has a terminal ethylenically unsaturated compound. It is selected from compounds having at least one, preferably two or more saturated bonds. These have chemical forms such as monomers, prepolymers, ie dimers, trimers and oligomers, or mixtures thereof.

  Examples of monomers include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), esters and amides thereof, preferably unsaturated carboxylic acids. An ester of an acid and a polyhydric alcohol compound and an amide of an unsaturated carboxylic acid and a polyvalent amine compound are used. In addition, an addition reaction product of an unsaturated carboxylic acid ester or amide having a nucleophilic substituent such as a hydroxy group, an amino group or a mercapto group with a monofunctional or polyfunctional isocyanate or epoxy, and a monofunctional or polyfunctional compound. A dehydration condensation reaction product with a functional carboxylic acid is also preferably used. Further, an addition reaction product of an unsaturated carboxylic acid ester or amide having an electrophilic substituent such as an epoxy group or an epoxy group with a monofunctional or polyfunctional alcohol, amine or thiol, a halogen group or In addition, a substitution reaction product of an unsaturated carboxylic acid ester or amide having a leaving substituent such as a tosyloxy group and a monofunctional or polyfunctional alcohol, amine or thiol is also suitable.

  As another example, it is also possible to use a group of compounds substituted with unsaturated phosphonic acid, styrene, vinyl ether or the like instead of the unsaturated carboxylic acid. These are disclosed in JP-T-2006-508380, JP-A-2002-287344, JP-A-2008-256850, JP-A-2001-342222, JP-A-9-179296, JP-A-9-179297. JP-A-9-179298, JP-A-2004-294935, JP-A-2006-243493, JP-A-2002-275129, JP-A-2003-64130, JP-A-2003-280187, It is described in references including Kaihei 10-333321.

  Specific examples of the monomer of the ester of a polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as ethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, Examples include trimethylolpropane triacrylate, hexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate, isocyanuric acid ethylene oxide (EO) -modified triacrylate, and polyester acrylate oligomer. Methacrylic acid esters include tetramethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, pentaerythritol trimethacrylate, bis [p- (3-methacryloxy-2-hydroxypropoxy) phenyl ] Dimethylmethane, bis- [p- (methacryloxyethoxy) phenyl] dimethylmethane, and the like. Specific examples of amide monomers of polyvalent amine compounds and unsaturated carboxylic acids include methylene bis-acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, 1,6-hexamethylene bis-methacrylic. Examples include amide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, and xylylene bismethacrylamide.

In addition, urethane-based addition-polymerizable compounds produced by using an addition reaction between an isocyanate and a hydroxy group are also suitable, and specific examples thereof include, for example, one molecule described in Japanese Patent Publication No. 48-41708. A vinyl containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxy group represented by the following general formula (b) to a polyisocyanate compound having two or more isocyanate groups. A urethane compound etc. are mentioned.
^{_{CH 2 = C (R 4)}} COOCH 2 CH (R 5) OH (b)
(However, R ⁴ and R ⁵ represent H or CH _3. )

  Also, urethanes described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-2003-344997, and JP-A-2006-65210. Acrylates, JP-B 58-49860, JP-B 56-17654, JP-B 62-39417, JP-B 62-39418, JP-A 2000-250211, JP-A 2007-94138 Urethane compounds having an ethylene oxide-based skeleton described in the publication, and urethane compounds having a hydrophilic group described in US Pat. No. 7,153,632, JP-T 8-505958, JP-A 2007-293221, and JP-A 2007-293223. Are also suitable.

  Among them, tris (acryloyloxyethyl) isocyanurate, bis (acryloyloxyethyl) hydroxyethyl isocyanurate, etc. are excellent in the balance between the hydrophilicity involved in on-press developability and the polymerization ability involved in printing durability. Isocyanuric acid ethylene oxide modified acrylates are particularly preferred.

  Details of the method of use such as the structure of these ethylenically unsaturated polymerizable compounds, whether they are used alone or in combination, and the amount added can be arbitrarily set according to the performance design of the final lithographic printing plate precursor. The polymerizable compound is preferably used in the range of 5 to 75% by mass, more preferably 10 to 70% by mass, and particularly preferably 15 to 60% by mass with respect to the total solid content of the image recording layer.

(E) Organic fine particles In the present invention, organic fine particles can be contained in the image recording layer in order to improve on-press developability. The organic fine particles in the present invention are at least selected from hydrophobic thermoplastic polymer fine particles, thermoreactive polymer fine particles, polymer fine particles having a polymerizable group, microcapsules enclosing a hydrophobic compound, and microgel (crosslinked polymer fine particles). One is preferable. Among these, polymer fine particles and microgels having a polymerizable group are preferable. The organic fine particles in the present invention may be discrete particles of the polymer compound of the present invention, and in a particularly preferred embodiment, the organic fine particles contain at least one ethylenically unsaturated polymerizable group. Due to the presence of such organic fine particles, an effect of improving the printing durability of the exposed portion and the on-press developability of the unexposed portion can be obtained.

Hydrophobic thermoplastic polymer fine particles include Research Disclosure No. 1 of January 1992. 331,003, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250 and European Patent No. 931647 are suitable. Can be cited as
Specific examples of polymers constituting such polymer fine particles include ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinyl carbazole, and polyalkylene structures. Mention may be made of homopolymers or copolymers of monomers such as acrylates or methacrylates or mixtures thereof. Among them, more preferable examples include a copolymer containing polystyrene, styrene and acrylonitrile, and polymethyl methacrylate.
The average particle size of the hydrophobic thermoplastic polymer fine particles used in the present invention is preferably 0.01 to 3.0 μm.

  Examples of the heat-reactive polymer fine particles used in the present invention include polymer fine particles having a heat-reactive group, and these form a hydrophobized region by crosslinking due to a heat reaction and a functional group change at that time.

  The thermoreactive group in the polymer fine particles having a thermoreactive group used in the present invention may be any functional group that performs any reaction as long as a chemical bond is formed, but is preferably a polymerizable group, Examples include ethylenically unsaturated groups that undergo radical polymerization reactions (eg, acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, etc.), cationic polymerizable groups (eg, vinyl groups, vinyloxy groups, epoxy groups, oxetanyl groups, etc.) ), An isocyanate group that performs an addition reaction or a block thereof, an epoxy group, a vinyloxy group, and a functional group having an active hydrogen atom that is a reaction partner thereof (for example, an amino group, a hydroxy group, a carboxy group, etc.), a condensation reaction Carboxy group to be carried out and reaction partner hydroxy group or amino group, acid anhydride to carry out ring-opening addition reaction and reaction An amino group or a hydroxyl group a manual may be mentioned as suitable.

  As the microcapsules used in the present invention, for example, as described in JP-A Nos. 2001-277740 and 2001-277742, all or part of the constituent components of the image recording layer are encapsulated in the microcapsules. Is. The constituent components of the image recording layer can also be contained outside the microcapsules. Furthermore, it is preferable that the image recording layer containing the microcapsule includes a hydrophobic constituent component in the microcapsule and a hydrophilic constituent component outside the microcapsule.

  In this invention, the aspect containing a crosslinked resin particle, ie, a microgel, may be sufficient. This microgel can contain a part of the constituent components of the image recording layer in at least one of the inside and the surface thereof, and in particular, an embodiment in which a reactive microgel is formed by having a radical polymerizable group on the surface thereof, This is particularly preferable from the viewpoint of image formation sensitivity and printing durability.

  As a method for microencapsulating or microgelling the constituent components of the image recording layer, known methods can be applied.

  The average particle size of the microcapsules or microgel is preferably 0.01 to 3.0 μm. 0.05-2.0 micrometers is still more preferable, and 0.10-1.0 micrometer is especially preferable. Within this range, good resolution and stability over time can be obtained.

  The organic fine particle content is preferably in the range of 5 to 90% by mass of the total solid content of the image recording layer.

(F) Other components The image recording layer in the invention may further contain other components as required.

(1) Low molecular weight hydrophilic compound The image recording layer in the invention may contain a low molecular weight hydrophilic compound in order to improve the on-press developability without reducing the printing durability.
As the low molecular weight hydrophilic compound, for example, as the water-soluble organic compound, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and the like glycols and ether or ester derivatives thereof, glycerin, Polyols such as pentaerythritol and tris (2-hydroxyethyl) isocyanurate, organic amines such as triethanolamine, diethanolamine and monoethanolamine and salts thereof, organic sulfones such as alkylsulfonic acid, toluenesulfonic acid and benzenesulfonic acid Acids and salts thereof, organic sulfamic acids such as alkylsulfamic acid and salts thereof, organic sulfuric acids such as alkylsulfuric acid and alkylethersulfuric acid and salts thereof, phenylphosphonic acid Organic phosphonic acids and salts thereof, tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, organic carboxylic acids and salts thereof such as amino acids, betaines, and the like.

  Among these, in the present invention, it is preferable to contain at least one selected from the group consisting of polyols, organic sulfates, organic sulfonates, and betaines.

  Specific examples of organic sulfonates include alkyl sulfonates such as sodium n-butyl sulfonate, sodium n-hexyl sulfonate, sodium 2-ethylhexyl sulfonate, sodium cyclohexyl sulfonate, and sodium n-octyl sulfonate. Sodium 5,8,11-trioxapentadecane-1-sulfonate, sodium 5,8,11-trioxaheptadecane-1-sulfonate, 13-ethyl-5,8,11-trioxaheptadecane-1; Alkyl sulfonates containing ethylene oxide chains such as sodium sulfonate, 5,8,11,14-tetraoxatetradecosane-1-sodium sulfonate; sodium benzenesulfonate, sodium p-toluenesulfonate, p-hydroxy Benzenesulfo Acid sodium, sodium p-styrenesulfonate, sodium dimethyl-5-sulfonate isophthalate, sodium 1-naphthylsulfonate, sodium 4-hydroxynaphthylsulfonate, disodium 1,5-naphthalenedisulfonate, 1,3,6 -Aryl sulfonates such as trisodium naphthalene trisulfonate, paragraph numbers [0026] to [0031] of JP 2007-276454 A, and paragraph numbers [0020] to [0047] of JP 2009-154525 A And the compounds described. The salt may be a potassium salt or a lithium salt.

  Organic sulfates include sulfates of alkyl, alkenyl, alkynyl, aryl or heterocyclic monoethers of polyethylene oxide. The number of ethylene oxide units is preferably 1 to 4, and the salt is preferably a sodium salt, potassium salt or lithium salt. Specific examples thereof include compounds described in paragraph numbers [0034] to [0038] of JP-A-2007-276454.

  As the betaines, compounds having 1 to 5 carbon atoms of the hydrocarbon substituent on the nitrogen atom are preferable. Specific examples include trimethylammonium acetate, dimethylpropylammonium acetate, 3-hydroxy-4-trimethyl. Ammonioobylate, 4- (1-pyridinio) butyrate, 1-hydroxyethyl-1-imidazolioacetate, trimethylammonium methanesulfonate, dimethylpropylammonium methanesulfonate, 3-trimethylammonio-1-propanesulfonate, Examples include 3- (1-pyridinio) -1-propanesulfonate.

  The above low molecular weight hydrophilic compound has a small hydrophobic part structure and almost no surface-active action, so that dampening water penetrates into the exposed part of the image recording layer (image part) and the hydrophobicity and film strength of the image part. Ink acceptability and printing durability of the image recording layer can be maintained satisfactorily.

The amount of these low molecular weight hydrophilic compounds added to the image recording layer is preferably 0.5% by mass or more and 20% by mass or less of the total solid content of the image recording layer. More preferably, they are 1 mass% or more and 15 mass% or less, More preferably, they are 2 mass% or more and 10 mass% or less. In this range, good on-press developability and printing durability can be obtained.
These compounds may be used alone or in combination of two or more.

(2) Grease Sensitizer In the image recording layer of the present invention, a lipid sensitizer such as a phosphonium compound, a nitrogen-containing low molecular weight compound, or an ammonium group-containing polymer is used for the image recording layer in order to improve the inking property. be able to. In particular, when an inorganic layered compound is contained in the protective layer, these compounds function as a surface coating agent for the inorganic layered compound, and prevent a decrease in the inking property during printing by the inorganic layered compound.

  Suitable phosphonium compounds include phosphonium compounds described in JP-A-2006-297907 and JP-A-2007-50660. Specific examples include tetrabutylphosphonium iodide, butyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, 1,4-bis (triphenylphosphonio) butanedi (hexafluorophosphate), 1,7-bis (tri Phenylphosphonio) heptane sulfate, 1,9-bis (triphenylphosphonio) nonane = naphthalene-2,7-disulfonate, and the like.

  Examples of the nitrogen-containing low molecular weight compound include amine salts and quaternary ammonium salts. Also included are imidazolinium salts, benzoimidazolinium salts, pyridinium salts, and quinolinium salts. Of these, quaternary ammonium salts and pyridinium salts are preferable. Specific examples include tetramethylammonium = hexafluorophosphate, tetrabutylammonium = hexafluorophosphate, dodecyltrimethylammonium = p-toluenesulfonate, benzyltriethylammonium = hexafluorophosphate, benzyldimethyloctylammonium = hexafluorophosphate. Fert, benzyldimethyldodecyl ammonium = hexafluorophosphate, paragraph numbers [0021] to [0037] of JP-A-2008-284858, paragraph numbers [0030] to [0057] of JP-A-2009-90645 Compound etc. are mentioned.

  The ammonium group-containing polymer may be any polymer as long as it has an ammonium group in its structure, but a polymer containing 5 to 80 mol% of a (meth) acrylate having an ammonium group in the side chain as a copolymerization component is preferable. . Specific examples include the polymers described in paragraph numbers [0089] to [0105] of JP2009-208458A.

  The ammonium salt-containing polymer has a reduced specific viscosity (unit: ml / g) determined by the following measurement method, preferably in the range of 5 to 120, more preferably in the range of 10 to 110, 15 Those in the range of ~ 100 are particularly preferred. When the said reduced specific viscosity is converted into a mass average molecular weight, 10,000-150,000 are preferable, 17000-140000 are more preferable, 20000-130000 are especially preferable.

<Measurement method of reduced specific viscosity>
Weigh 3.33 g of 30% polymer solution (1 g as solid content) into a 20 ml volumetric flask and make up with N-methylpyrrolidone. This solution is allowed to stand for 30 minutes in a thermostatic bath at 30 ° C., put in an Ubbelohde reduced viscosity tube (viscosity constant = 0.010 cSt / s), and the time for flowing down at 30 ° C. is measured. The measurement is performed twice with the same sample, and the average value is calculated. Similarly, in the case of a blank (only N-methylpyrrolidone), the reduced specific viscosity (ml / g) was calculated from the following formula.

Specific examples of the ammonium group-containing polymer are shown below.
(1) 2- (trimethylammonio) ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90 mass average molecular weight 45,000)
(2) 2- (Trimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 mass average molecular weight 60,000)
(3) 2- (Ethyldimethylammonio) ethyl methacrylate = p-toluenesulfonate / hexyl methacrylate copolymer (molar ratio 30/70 mass average molecular weight 45,000)
(4) 2- (trimethylammonio) ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20/80 mass average molecular weight 60,000)
(5) 2- (Trimethylammonio) ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (molar ratio 40/60 mass average molecular weight 7 million)
(6) 2- (butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 25/75 mass average molecular weight 650,000)
(7) 2- (Butyldimethylammonio) ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 mass average molecular weight 650,000)
(8) 2- (butyldimethylammonio) ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 (Mass average molecular weight 75,000)
(9) 2- (butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate / 2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer (molar ratio 15/80/5 (Mass average molecular weight 650,000)

  The content of the sensitizer is preferably 0.01 to 30.0% by mass, more preferably 0.1 to 15.0% by mass and 1 to 10% by mass with respect to the total solid content of the image recording layer. Is more preferable.

(4) Others Further, as other components, surfactants, colorants, baking-out agents, polymerization inhibitors, higher fatty acid derivatives, plasticizers, inorganic fine particles, inorganic layered compounds, co-sensitizers or chain transfer agents, etc. Can be added. Specifically, paragraph numbers [0114] to [0159] of Japanese Patent Application Laid-Open No. 2008-284817, paragraph numbers [0023] to [0027] of Japanese Patent Application Laid-Open No. 2006-091479, and US Patent Publication No. 2008/0311520. The compound and the addition amount described in paragraph [0060] of FIG.

(G) Formation of Image Recording Layer The image recording layer in the present invention may be prepared by using the necessary components described above as described in paragraphs [0142] to [0143] of JP-A-2008-195018, for example. A coating solution is prepared by dispersing or dissolving in a coating solution, which is coated on a support by a known method such as bar coater coating and dried. The image recording layer coating amount (solid content) on the support obtained after coating and drying varies depending on the application, but is generally preferably 0.3 to 3.0 g / m ² . Within this range, good sensitivity and good film characteristics of the image recording layer can be obtained.

(Undercoat layer)
In the lithographic printing plate precursor according to the invention, an undercoat layer (sometimes referred to as an intermediate layer) is preferably provided between the image recording layer and the support. The undercoat layer enhances the adhesion between the support and the image recording layer in the exposed area, and easily peels off the image recording layer from the support in the unexposed area. Contributes to improvement. In the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, thereby preventing the heat generated by the exposure from diffusing to the support and reducing the sensitivity.

  As the compound used for the undercoat layer, those having an adsorptive group capable of being adsorbed on the surface of the support and a crosslinkable group for improving the adhesion to the image recording layer are preferable. Furthermore, compounds having a hydrophilicity-imparting group such as a sulfo group can also be mentioned as suitable compounds. These compounds may be low molecular weight or high molecular weight polymers. Moreover, you may use these compounds in mixture of 2 or more types as needed.

In the case of a high molecular polymer, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferable. The adsorbable adsorptive group to the surface of the support, a phenolic hydroxy group, a carboxy _{group, -PO 3 H 2, -OPO 3} H 2, -CONHSO 2 -, - SO 2 NHSO 2 -, - COCH 2 COCH 3 Is preferred. As the hydrophilic group, a sulfo group is preferable. The crosslinkable group is preferably a methacryl group or an allyl group.
This polymer may have a crosslinkable group introduced by salt formation between the polar substituent of the polymer, a substituent having a counter charge and a compound having an ethylenically unsaturated bond, Other monomers, preferably hydrophilic monomers, may be further copolymerized.
Specifically, a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679 and an ethylenic compound described in JP-A-2-304441. The phosphorus compound which has a heavy bond reactive group is mentioned suitably. Crosslinkable group (preferably ethylenically unsaturated bond group) described in JP-A-2005-238816, JP-A-2005-12549, JP-A-2006-239867, JP-A-2006-215263, surface of support Those containing a low-molecular or high-molecular compound having a functional group that interacts with each other and a hydrophilic group are also preferably used. More preferable are polymer polymers having an adsorbable group, a hydrophilic group, and a crosslinkable group that can be adsorbed on the support surface described in JP-A Nos. 2005-125749 and 2006-188038.

The content of unsaturated double bonds in the polymer resin for the undercoat layer is preferably 0.1 to 10.0 mmol, and most preferably 0.2 to 5.5 mmol per 1 g of the polymer.
The polymer for the undercoat layer preferably has a mass average molar mass of 5000 or more, more preferably 10,000 to 300,000.

  The undercoat layer of the present invention comprises, in addition to the above undercoat compound, a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, an amino group, or a functional group having a polymerization inhibiting ability, in order to prevent contamination over time. Compounds having a group that interacts with the surface of an aluminum support (for example, 1,4-diazabicyclo [2,2,2] octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil , Sulfophthalic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, and the like.

The undercoat layer is applied by a known method. The coating amount (solid content) of the undercoat layer is preferably from 0.1-100 mg / m ^2, and more preferably 1 to 30 mg / m ^2.

(Support)
As the support used in the lithographic printing plate precursor according to the invention, a known support is used. Of these, an aluminum plate that has been roughened and anodized by a known method is preferred.
In addition, the above aluminum plate is optionally subjected to micropore enlargement treatment or sealing treatment of an anodized film described in JP-A Nos. 2001-253181 and 2001-322365, and US Pat. 714,066, 3,181,461, 3,280,734 and 3,902,734, or alkali metal silicates as described in U.S. Pat. Surface hydrophilization treatment with polyvinylphosphonic acid or the like as described in each specification of 3,276,868, 4,153,461 and 4,689,272 is appropriately performed and performed. be able to.
The support preferably has a center line average roughness of 0.10 to 1.2 μm.

  If necessary, the support of the present invention includes an organic polymer compound described in JP-A-5-45885 and a silicon alkoxy compound described in JP-A-5-45885 on the back surface. A backcoat layer can be provided.

(Protective layer)
In the lithographic printing plate precursor according to the invention, a protective layer (overcoat layer) is preferably provided on the image recording layer. In addition to the function of suppressing the image formation inhibition reaction by blocking oxygen, the protective layer has a function of preventing scratches in the image recording layer and preventing ablation during high-illuminance laser exposure.

The protective layer having such characteristics is described in, for example, US Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. As the low oxygen permeability polymer used for the protective layer, either a water-soluble polymer or a water-insoluble polymer can be appropriately selected and used, and two or more types can be mixed and used as necessary. it can. Specific examples include polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble cellulose derivatives, poly (meth) acrylonitrile, and the like.
As the modified polyvinyl alcohol, acid-modified polyvinyl alcohol having a carboxylic acid group or a sulfonic acid group is preferably used. Specifically, modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137 are suitable.

Further, in order to enhance the oxygen barrier property, the protective layer preferably contains an inorganic layered compound such as natural mica and synthetic mica as described in JP-A-2005-119273.
Further, the protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coating properties, and inorganic fine particles for controlling surface slipperiness. Further, the protective layer can contain the sensitizer described in the description of the image recording layer.

The protective layer is applied by a known method. The coating amount of the protective layer, the coating amount after drying is preferably in the range of 0.01 to 10 g / ^{m 2,} more preferably in the range of 0.02 to 3 g / ^{m 2,} and most preferably 0. in the range of 02~1g / ^{m 2.}

[Plate making method]
The plate making of the lithographic printing plate precursor according to the invention is preferably carried out by an on-press development method. The on-press development method includes an image exposure process for a lithographic printing plate precursor, a printing process in which an oil-based ink and an aqueous component are supplied and printed without performing any development process on the exposed lithographic printing plate precursor. The image recording layer unexposed portion of the lithographic printing plate precursor is removed in the course of the printing process. Imagewise exposure may be performed on the printing machine after the lithographic printing plate precursor is mounted on the printing machine, or may be separately performed with a plate setter or the like. In the latter case, the exposed lithographic printing plate precursor is mounted on a printing machine without undergoing a development process. Thereafter, by using the printing machine and supplying the oil-based ink and the aqueous component and printing as it is, an on-press development process, that is, an image recording layer in an unexposed area is removed at an early stage of printing, Accordingly, the surface of the hydrophilic support is exposed to form a non-image part. As the oil-based ink and the aqueous component, ordinary lithographic printing ink and fountain solution are used.
This will be described in more detail below.

In the present invention, the light source used for image exposure is preferably a laser. Although the laser used for this invention is not specifically limited, The solid laser and semiconductor laser etc. which irradiate infrared rays with a wavelength of 760-1200 nm are mentioned suitably.
Regarding the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably within 20 microseconds, and the irradiation energy amount is preferably 10 to 300 mJ / cm ² . In the laser, it is preferable to use a multi-beam laser device in order to shorten the exposure time.

  The exposed lithographic printing plate precursor is mounted on a plate cylinder of a printing press. In the case of a printing press equipped with a laser exposure device, image exposure is performed after a lithographic printing plate precursor is mounted on a plate cylinder of the printing press.

  When printing is performed by supplying dampening water and printing ink to the lithographic printing plate precursor exposed imagewise, the image recording layer cured by exposure has a printing ink acceptance having an oleophilic surface in the exposed portion of the image recording layer. Forming part. On the other hand, in the unexposed area, the uncured image recording layer is removed by dissolution or dispersion by the supplied dampening water and / or printing ink, and a hydrophilic surface is exposed in that area. As a result, the fountain solution adheres to the exposed hydrophilic surface, and the printing ink is deposited on the image recording layer in the exposed area and printing is started.

Here, dampening water or printing ink may be supplied to the printing plate first, but printing is first performed in order to prevent the dampening water from being contaminated by the removed image recording layer components. It is preferable to supply ink.
In this way, the lithographic printing plate precursor according to the invention is developed on the machine on an offset printing machine and used as it is for printing a large number of sheets.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

[Synthesis example of polymer compound]
(1) Synthesis of Polymer Compound (P-1) 200 g of 1-methyl-2-pyrrolidone was placed in a 1 L three-necked flask equipped with a condenser and a stirrer, and heated to 75 ° C. under a nitrogen stream. 20 g of polyethylene glycol methyl ether methacrylate (PEGMA ethylene glycol has an average number of repeating units of 45), 10 g of styrene (St), 50 g of acrylonitrile (AN), [2- (methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium Betaine, inner salt (MOE) 12 g, 2-hydroxyethyl methacrylate (HEMA) 6 g, V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) 0.8 g, 1-methyl-2-pyrrolidone 200 g over 2 hours And dripped. After completion of the dropping, the mixture was further stirred for 2 hours, 0.4 g of V-601 was added, and the mixture was reacted for 4 hours. After nitrogen was stopped and the reaction solution was cooled to room temperature, 25 g of 2-methacryloyloxyethyl isocyanate (MOI), 0.3 g of p-methoxyphenol and 0.6 g of dibutyltin dilaurate were added, and the mixture was heated and stirred at 60 ° C. Six hours later, 50 g of methanol was added, unreacted 2-methacryloyloxyethyl isocyanate was deactivated, and the reaction solution was cooled to room temperature.
It was confirmed by ¹ H-NMR spectrum that a double bond was introduced into the side chain by the polymer reaction. It was 63,000 as a result of measuring a mass mean molar mass (Mw) by the gel permeation chromatography method (GPC) which used polyacrylic acid as the standard substance.

(2) Synthesis of polymer compound (P-14) 200 g of 1-methyl-2-pyrrolidone was placed in a 1 L three-necked flask equipped with a condenser and a stirrer and heated to 75 ° C. under a nitrogen stream. 20 g of polyethylene glycol methyl ether methacrylate (PEGMA ethylene glycol has an average repeating unit of 45), 10 g of styrene (St), 50 g of acrylonitrile (AN), [3- (methacryloylamino) propyl] dimethyl- (3-sulfopropyl) ammonium betaine A solution of 12 g of inner salt, 6 g of 2-hydroxyethyl methacrylate (HEMA), 0.8 g of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) and 200 g of 1-methyl-2-pyrrolidone was added dropwise over 2 hours. After completion of the dropping, the mixture was further stirred for 2 hours, 0.4 g of V-601 was added, and the mixture was reacted for 4 hours. After nitrogen was stopped and the reaction solution was cooled to room temperature, 25 g of 2-methacryloyloxyethyl isocyanate (MOI), 0.3 g of p-methoxyphenol and 0.6 g of dibutyltin dilaurate were added, and the mixture was heated and stirred at 60 ° C. Six hours later, 50 g of methanol was added, unreacted 2-methacryloyloxyethyl isocyanate was deactivated, and the reaction solution was cooled to room temperature.
It was confirmed by ¹ H-NMR spectrum that a double bond was introduced into the side chain by the polymer reaction. The mass average molecular weight measured by GPC using polyacrylic acid as a standard substance was 52,000.

(3) Synthesis of polymer compound (P-27) 200 g of 1-methyl-2-pyrrolidone was placed in a 1 L three-necked flask equipped with a condenser and a stirrer and heated to 75 ° C. under a nitrogen stream. 20 g of polyethylene glycol methyl ether methacrylate (PEGMA ethylene glycol has an average repeating unit of about 45), 10 g of styrene (St), 50 g of acrylonitrile (AN), [2- (methacryloyloxy) ethyl] dimethyl- (3-carboxyethyl) ammonium A solution of betaine, inner salt 12 g, 2-hydroxyethyl methacrylate (HEMA) 6 g, V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) 0.8 g, and 1-methyl-2-pyrrolidone 200 g was added dropwise over 2 hours. . After completion of the dropping, the mixture was further stirred for 2 hours, 0.4 g of V-601 was added, and the mixture was reacted for 4 hours. After nitrogen was stopped and the reaction solution was cooled to room temperature, 25 g of 2-methacryloyloxyethyl isocyanate (MOI), 0.3 g of p-methoxyphenol and 0.6 g of dibutyltin dilaurate were added, and the mixture was heated and stirred at 60 ° C. Six hours later, 50 g of methanol was added, unreacted 2-methacryloyloxyethyl isocyanate was deactivated, and the reaction solution was cooled to room temperature.
It was confirmed by ¹ H-NMR spectrum that a double bond was introduced into the side chain by the polymer reaction. The mass average molecular weight measured by GPC using polyacrylic acid as a standard substance was 57,000.

(4) Production of polymer fine particle aqueous dispersion of polymer compound (P-57) A 1000 ml four-necked flask was equipped with a stirrer, thermometer, dropping funnel, nitrogen inlet tube, reflux condenser, and nitrogen gas was introduced. Then, 20 g of polyethylene glycol methyl ether methacrylate (the average repeating unit of PEGMA ethylene glycol was 45), 200 g of distilled water and 200 g of n-propanol were added and heated until the internal temperature reached 70 ° C. Next, 10 g of styrene (St) premixed, 50 g of acrylonitrile (AN), [2- (methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium betaine, 12 g of inner salt, and 2,2′-azobis A mixture of 0.8 g of isobutyronitrile was added dropwise over 1 hour. After completion of the dropwise addition, the reaction was continued for 5 hours, and then 0.4 g of 2,2′-azobisisobutyronitrile was added to raise the internal temperature to 80 ° C. Subsequently, 0.5 g of 2,2′-azobisisobutyronitrile was added over 6 hours. Polymerization had progressed over 98% at the stage of reaction for a total of 20 hours. The particle size distribution of the polymer fine particles had a maximum value at a particle size of 150 nm.

  Here, the particle size distribution is obtained by taking an electron micrograph of polymer fine particles, measuring a total of 5000 fine particle sizes on the photograph, and a logarithmic scale between 0 and the maximum value of the obtained particle size measurement values. And the frequency of appearance of each particle size was plotted and obtained. For non-spherical particles, the particle size of spherical particles having the same particle area as that on the photograph was used as the particle size.

(5) Production of polymer fine particle aqueous dispersion of polymer compound (P-64) A 1000 ml four-necked flask was equipped with a stirrer, thermometer, dropping funnel, nitrogen inlet tube, reflux condenser, and nitrogen gas was introduced. Then, 20 g of polyethylene glycol methyl ether methacrylate (the average repeating unit of PEGMA ethylene glycol was 45), 200 g of distilled water and 200 g of n-propanol were added and heated until the internal temperature reached 70 ° C. Next, 10 g of styrene (St) premixed, 50 g of acrylonitrile (AN), [3- (methacryloylamino) propyl] dimethyl- (3-sulfopropyl) ammonium betaine, 12 g of inner salt, and 2,2′-azobis A mixture of 0.8 g of isobutyronitrile was added dropwise over 1 hour. After completion of the dropwise addition, the reaction was continued for 5 hours, and then 0.4 g of 2,2′-azobisisobutyronitrile was added to raise the internal temperature to 80 ° C. Subsequently, 0.5 g of 2,2′-azobisisobutyronitrile was added over 6 hours. Polymerization had progressed over 98% at the stage of reaction for a total of 20 hours. The particle size distribution of the polymer fine particles had a maximum value at a particle size of 150 nm.

(6) Production of polymer fine particle aqueous dispersion of polymer compound (P-71) A 1000 ml four-necked flask was subjected to a stirrer, thermometer, dropping funnel, nitrogen inlet tube, reflux condenser, and nitrogen gas was introduced. Then, 20 g of polyethylene glycol methyl ether methacrylate (the average repeating unit of PEGMA ethylene glycol was 45), 200 g of distilled water and 200 g of n-propanol were added and heated until the internal temperature reached 70 ° C. Next, 10 g of premixed styrene (St), 50 g of acrylonitrile (AN), [2- (methacryloyloxy) ethyl] dimethyl- (3-carboxyethyl) ammonium betaine, 12 g of inner salt and 2,2′-azobisiso A mixture of 0.8 g of butyronitrile was added dropwise over 1 hour. After completion of the dropwise addition, the reaction was continued for 5 hours, and then 0.4 g of 2,2′-azobisisobutyronitrile was added to raise the internal temperature to 80 ° C. Subsequently, 0.5 g of 2,2′-azobisisobutyronitrile was added over 6 hours. Polymerization had progressed over 98% at the stage of reaction for a total of 20 hours. The particle size distribution of the polymer fine particles had a maximum value at a particle size of 150 nm.

[Examples 1-27 and Comparative Examples 1-2: Production and evaluation of lithographic printing plate precursor]

1. Production of lithographic printing plate precursors (1) to (11) (1) Production of support 10 mass% sodium aluminate aqueous solution for removing rolling oil on the surface of a 0.3 mm thick aluminum plate (material JIS A 1050) After degreasing at 50 ° C. for 30 seconds, three bundle-planted nylon brushes with a bristle diameter of 0.3 mm and a pumice-water suspension with a median diameter of 25 μm (specific gravity 1.1 g / cm ³ ) were used. The aluminum surface was grained and washed thoroughly with water. This plate was etched by being immersed in a 25 mass% sodium hydroxide aqueous solution at 45 ° C for 9 seconds, washed with water, further immersed in 20 mass% nitric acid at 60 ° C for 20 seconds, and washed with water. At this time, the etching amount of the grained surface was about 3 g / m ² .

Next, an electrochemical roughening treatment was performed continuously using an alternating voltage of 60 Hz. The electrolytic solution at this time was a 1% by mass nitric acid aqueous solution (containing 0.5% by mass of aluminum ions) and a liquid temperature of 50 ° C. The AC power supply waveform is electrochemical roughening treatment using a trapezoidal rectangular wave AC with a time TP of 0.8 msec until the current value reaches a peak from zero, a duty ratio of 1: 1, and a trapezoidal rectangular wave AC. Went. Ferrite was used for the auxiliary anode. The current density was 30 A / dm ² at the peak current value, and 5% of the current flowing from the power source was shunted to the auxiliary anode. The amount of electricity in nitric acid electrolysis was 175 C / dm ² when the aluminum plate was the anode. Then, water washing by spraying was performed.

Subsequently, nitric acid electrolysis was performed with an aqueous solution of 0.5% by mass of hydrochloric acid (containing 0.5% by mass of aluminum ions) and an electrolytic solution having a liquid temperature of 50 ° C. under the condition of an electric quantity of 50 C / dm ² when the aluminum plate was the anode. Electrochemical surface roughening treatment was carried out in the same manner as above, followed by washing with water by spraying.
Next, the plate was provided with a direct current anodic oxide film having a current density of 15 A / dm ² and a current density of 15 g / m ² using 15% by mass sulfuric acid (containing 0.5% by mass of aluminum ions) as an electrolytic solution, followed by washing with water. It dried and produced the support body (1).
Thereafter, in order to ensure the hydrophilicity of the non-image area, the support (1) was subjected to a silicate treatment at 60 ° C. for 10 seconds using an aqueous 2.5 mass% No. 3 sodium silicate solution, and then washed with water for support. Body (2) was obtained. The adhesion amount of Si was 10 mg / m ² . The centerline average roughness (Ra) of this substrate was measured using a needle having a diameter of 2 μm and found to be 0.51 μm.

(2) Formation of undercoat layer Next, the following undercoat layer coating solution (1) is applied onto the support (2) so that the dry coating amount is 20 mg / m ² , and used in the following experiments. A support having a layer was prepared.

<Coating liquid for undercoat layer (1)>
-Undercoat layer compound (1) having the following structure: 0.18 g
・ Hydroxyethyliminodiacetic acid 0.10g
・ Methanol 55.24g
・ Water 6.15g

(3) Formation of image recording layer An image recording layer coating solution having the following composition was bar coated on the undercoat layer formed as described above, and then oven-dried at 100 ° C. for 60 seconds to obtain a dry coating amount of 1.0 g. An image recording layer of / m ² was formed.
The image recording layer coating solution (1) was obtained by mixing and stirring the following photosensitive solution (1) and microgel solution (1) immediately before coating.

<Photosensitive solution (1)>
-Polymer compound of the present invention (polymer compounds described in Table 6) 0.240 g
Infrared absorber (1) [the following structure] 0.030 g
・ Polymerization initiator (1) [the following structure] 0.162 g
Ethylenically unsaturated polymerizable compound Tris (acryloyloxyethyl) isocyanurate (NK ester A-9300, manufactured by Shin-Nakamura Chemical Co., Ltd.) 0.192 g
・ Low molecular weight hydrophilic compound Tris (2-hydroxyethyl) isocyanurate 0.062g
・ Low molecular weight hydrophilic compound (1) [the following structure] 0.050 g
-Sensitizing agent Phosphonium compound (1) [the following structure] 0.055 g
・ Sensitizer Benzyl-dimethyl-octylammonium ・ PF ₆ salt 0.018g
-Sensitizing agent Ammonium group-containing polymer [the following structure, reduced specific viscosity 44 cSt / g / ml] 0.035 g
・ Fluorosurfactant (1) [The following structure] 0.008g
・ 2-butanone 1.091g
・ 1-methoxy-2-propanol 8.609g

<Microgel solution (1)>
・ Microgel (1) 2.640 g
・ Distilled water 2.425g

  The structures of the infrared absorber (1), the polymerization initiator (1), the phosphonium compound (1), the low molecular weight hydrophilic compound (1), the ammonium group-containing polymer, and the fluorine-based surfactant (1) are as follows: It is as shown below.

-Synthesis of microgel (1)-
As an oil phase component, trimethylolpropane and xylene diisocyanate adduct (Mitsui Chemical Polyurethane Co., Ltd., Takenate D-110N) 10 g, pentaerythritol triacrylate (Nippon Kayaku Co., Ltd., SR444) 3.15 g, And 0.1 g of Pionein A-41C (manufactured by Takemoto Yushi Co., Ltd.) was dissolved in 17 g of ethyl acetate. As an aqueous phase component, 40 g of a 4 mass% aqueous solution of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-205) was prepared. The oil phase component and the aqueous phase component were mixed and emulsified for 10 minutes at 12,000 rpm using a homogenizer. The obtained emulsion was added to 25 g of distilled water, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours. The microgel solution thus obtained was diluted with distilled water to a solid content concentration of 15% by mass, and this was designated as the microgel (1). When the average particle size of the microgel was measured by a light scattering method, the average particle size was 0.2 μm.

(4) Formation of protective layer After the bar coating of the protective layer coating solution (1) having the following composition was further applied on the image recording layer, it was oven-dried at 120 ° C. for 60 seconds, and the dry coating amount was 0.15 g / m ^2. A lithographic printing plate precursor (1) to (11) was obtained.

<Coating liquid for protective layer (1)>
・ Inorganic layered compound dispersion (1) 1.5 g
-Polyvinyl alcohol (Nippon Synthetic Chemical Industry Co., Ltd. CKS50, sulfonic acid modification,
Saponification degree 99 mol% or more, polymerization degree 300) 6% by mass aqueous solution 0.55 g
・ Polyvinyl alcohol (PVA-405 manufactured by Kuraray Co., Ltd.)
Degree of saponification 81.5 mol%, degree of polymerization 500) 6% by weight aqueous solution 0.03 g
・ Nippon Emulsion Co., Ltd. surfactant (Emalex 710) 1% by weight aqueous solution 0.86g
・ Ion-exchanged water 6.0g

(Preparation of inorganic layered compound dispersion (1))
6.4 g of synthetic mica Somasif ME-100 (manufactured by Coop Chemical Co., Ltd.) was added to 193.6 g of ion-exchanged water, and dispersed using an homogenizer until the average particle size (laser scattering method) became 3 μm. The aspect ratio of the obtained dispersed particles was 100 or more.

2. Preparation of lithographic printing plate precursor (12) Lithographic printing is performed by repeating preparation of lithographic printing plate precursor (1) except that the following image recording layer coating liquid (2) is used instead of image recording layer coating liquid (1). An original plate (12) was obtained.

<Image recording layer coating solution (2)>
-Polymer fine particle aqueous dispersion of polymer compound (P-57) 20 g
・ Infrared absorber (2) [the following structure] 0.2g
・ Polymerization initiator Irgacure250 (Ciba Specialty Chemicals) 0.5g
・ Ethylenically unsaturated polymerizable compound SR-399 (Sartomer) 1.5g
・ Mercapto-3-triazole 0.2g
・ Byk307 (Byk Chimie) 0.1g
・ Klucel M (Hercules) 4.8g
・ N-propanol 55.0g
・ Water 17.0g

In addition, the compounds described by trade names in the above composition are as follows.
IRGACURE 250: (4-methoxyphenyl) [4- (2-methylpropyl) phenyl] iodonium = hexafluorophosphate (75% by mass propylene carbonate solution)
・ SR-399: Dipentaerythritol pentaacrylate
・ Byk307: Modified dimethylpolysiloxane ・ Klucel M: Hydroxypropyl cellulose

3. Preparation of lithographic printing plate precursors (13) to (27) Polymer fine particles of each polymer compound described in Table 6 instead of polymer fine particle aqueous dispersion of polymer compound (P-57) in image recording layer coating liquid (2) The lithographic printing plate precursors (13) to (27) were obtained by repeating the production of the lithographic printing plate precursor (11) except that the aqueous dispersion was used.

4). Preparation of lithographic printing plate precursor (28) for comparative example In place of the polymer fine particle aqueous dispersion of polymer compound (P-57) in image recording layer coating liquid (2), the following comparative polymer compound (R- A lithographic printing plate precursor (28) for Comparative Example was obtained by repeating the preparation of the lithographic printing plate precursor (12) except that the polymer fine particle aqueous dispersion of 1) was used.

(Production of polymer fine particle aqueous dispersion of comparative polymer compound (R-1))
A 1000 ml four-necked flask was equipped with a stirrer, thermometer, dropping funnel, nitrogen inlet tube, reflux condenser, and nitrogen gas was introduced to perform deoxygenation, while polyethylene glycol methyl ether methacrylate (average of PEGMA ethylene glycol) The repeating unit was 45) 20 g, distilled water 200 g and n-propanol 200 g were added and heated until the internal temperature reached 70 ° C. Next, a premixed mixture of 10 g of styrene (St), 50 g of acrylonitrile (AN), and 0.8 g of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour. After completion of the dropwise addition, the reaction was continued for 5 hours, and then 0.4 g of 2,2′-azobisisobutyronitrile was added to raise the internal temperature to 80 ° C. Subsequently, 0.5 g of 2,2′-azobisisobutyronitrile was added over 6 hours. Polymerization had progressed over 98% at the stage of reaction for a total of 20 hours. The particle size distribution of the polymer fine particles had a maximum value at a particle size of 150 nm.

5. Preparation of lithographic printing plate precursor (29) for comparative example Except for using the following comparative polymer compound (R-2) instead of the polymer compound (P-1) in the image recording layer coating solution (1) Produced a lithographic printing plate precursor (29) for comparative examples by repeating the preparation of the lithographic printing plate precursor (1).

(Production of Comparative Polymer Compound (R-2))
200 g of 1-methyl-2-pyrrolidone was placed in a 1 L three-necked flask equipped with a condenser and a stirrer and heated to 75 ° C. under a nitrogen stream. 20 g of polyethylene glycol methyl ether methacrylate (PEGMA ethylene glycol has an average number of repeating units of 45), 10 g of styrene (St), 50 g of acrylonitrile (AN), 6 g of 2-hydroxyethyl methacrylate (HEMA), V-601 (Wako Pure Chemical Industries, Ltd.) A solution of 0.8 g and 1-methyl-2-pyrrolidone 200 g was added dropwise over 2 hours. After completion of the dropping, the mixture was further stirred for 2 hours, 0.4 g of V-601 was added, and the mixture was reacted for 4 hours. After nitrogen was stopped and the reaction solution was cooled to room temperature, 25 g of 2-methacryloyloxyethyl isocyanate (MOI), 0.3 g of p-methoxyphenol and 0.6 g of dibutyltin dilaurate were added, and the mixture was heated and stirred at 60 ° C. Six hours later, 50 g of methanol was added, unreacted 2-methacryloyloxyethyl isocyanate was deactivated, and the reaction solution was cooled to room temperature.
It was confirmed by ¹ H-NMR spectrum that a double bond was introduced into the side chain by the polymer reaction. It was 60,000 as a result of measuring a mass mean molar mass (Mw) by the gel permeation chromatography method (GPC) which used polyacrylic acid as the standard substance.

6). Evaluation of lithographic printing plate precursor (1) On-press developability The obtained lithographic printing plate precursor was subjected to an external drum rotation speed of 1000 rpm and a laser output of 70% on a Luxel PLANETTER T-6000III manufactured by Fuji Film Co., Ltd. equipped with an infrared semiconductor laser. The exposure was performed under the condition of a resolution of 2400 dpi. The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The obtained exposed original plate was attached to a plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Equality-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) dampening water and Values-G (N) black ink (manufactured by Dainippon Ink & Chemicals, Inc.) After dampening water and ink were supplied by the standard automatic printing start method of LITHRONE 26 and developed on the machine, 100 sheets were printed on Tokuhishi Art (76.5 kg) paper at a printing speed of 10,000 sheets per hour.
The number of print sheets required until the on-press development on the printing press of the unexposed portion of the image recording layer was completed and the ink was not transferred to the non-image portion was measured as on-press developability. The results are shown in Table 6.

(2) Printing durability After the above-described evaluation of on-press developability, the printing was further continued. As the number of printed sheets was increased, the image recording layer was gradually worn out, so that the ink density on the printed material decreased. Printing durability was evaluated using the number of printed copies when the value measured by the Gretag densitometer for the 50% halftone dot area ratio of the FM screen in the printed material was 5% lower than the measured value for the 100th printed sheet. . The results are shown in Table 6.

(3) Stain resistance In the 500th printed material of the above-mentioned printing durability evaluation, the stain resistance is not inferior to “O” or “O” but has no problem in practical use. Was evaluated as “C”, and “×” was used when there was some dirt and a problem in practical use. The results are shown in Table 6.

Claims (15)

  On the support, (A) a polymer compound having a side chain containing a betaine structure, (B) an infrared absorber, (C) a polymerization initiator, and (D) an ethylenically unsaturated polymerizable compound, and printing A lithographic printing plate precursor comprising an image recording layer which can be removed by ink and / or fountain solution.   The lithographic printing plate precursor as claimed in claim 1, wherein the polymer compound is organic polymer fine particles.   The lithographic printing plate precursor as claimed in claim 1, wherein the polymer compound is a binder, and the image recording layer further comprises (E) organic fine particles.   The lithographic printing plate precursor as claimed in claim 3, wherein the organic fine particles are microcapsules or microgels.   The lithographic printing plate precursor as claimed in any one of claims 1 to 4, wherein the betaine structure is carbobetaine, sulfobetaine or phosphobetaine.   The lithographic printing plate precursor as claimed in claim 5, wherein the betaine structure is carbobetaine or sulfobetaine. The lithographic printing plate precursor as claimed in any one of claims 1 to 5, wherein the polymer compound comprises at least one monomer unit selected from the following general formulas (1) to (4).

(In the above formula, R ₁ , R ₄ , R ₇ and R ₁₀ each independently represent a hydrogen atom, a halogen atom or a substituent having 1 to 12 carbon atoms, and L ₁ , L ₂ , L ₃ and L ₄ are Each independently represents a single bond or a divalent linking group, X ₁ represents an alkylene group, a substituted alkylene group, or a divalent linking group having a polyalkylene oxide group, and Y ₁ represents an alkylene group or a substituted alkylene group. , R ₂ , R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ , R ₁₂ and R ₁₃ are each independently an alkyl group having 1 to 6 carbon atoms which may have a substituent, Represents an alkenyl group, an alkynyl group, a cycloalkyl group or an aryl group (R ₂ , R ₃ and Y ₁ ), (R ₅ , R ₆ and Y ₁ ), (R ₈ , R ₉ and Y ₁ ), and ( R ₁₁ to R ₁₃ and responsibility in each group _{Y 1)} Two members to the may form a heterocyclic ring.) In the general formulas (1) and (2), R ₁ and R ₄ each independently represent a hydrogen atom or a methyl group, and L ₁ and L ₂ each independently represent —COO—, —OCO—, —O—. , —CO—NR ₁₄ — or a phenylene group, R ₁₄ is a hydrogen atom, or an optionally substituted alkyl group, cycloalkyl group, aryl group or aralkyl group having 1 to 12 carbon atoms. The lithographic printing plate precursor as claimed in claim 7, wherein The lithographic printing plate precursor as claimed in any one of claims 1 to 8, wherein the polymer compound comprises a monomer unit represented by the following general formula (5).

(In the above formula, R ₁₅ represents a hydrogen atom, a halogen atom, or a substituent having 1 to 12 carbon atoms, and R ₁₆ represents a group having an ester group, an amide group, a cyano group, a hydroxy group, or an aryl group. .) In the general formula (5), R ₁₅ is a hydrogen atom or methyl, and R ₁₆ is an ester group, an amide group, a cyano group, or a group having a phenyl group which may have a substituent. The lithographic printing plate precursor as claimed in claim 9. The lithographic printing plate precursor as claimed in claim 9 or 10, wherein in the general formula (5), R ₁₆ contains a polyalkyleneoxy group. The polymer compound further comprises a monomer unit having at least one ethylenically unsaturated polymerizable group represented by the general formulas (6) to (8) in a side chain. The lithographic printing plate precursor as described in any one of the above items.

(In the formula, X and Y each independently represent an oxygen atom or —N (R ₂₈ ) —. Z represents an oxygen atom, —N (R ₂₈ ) — or a phenylene group. R _{17 to} R ₂₈ each represent Independently represents a monovalent substituent)   The lithographic printing plate precursor as claimed in claim 1, further comprising a protective layer on the image recording layer.   The lithographic printing plate precursor as claimed in claim 13, wherein the protective layer contains an inorganic stratiform compound.   The lithographic printing plate precursor according to any one of claims 1 to 14 is image-exposed with an infrared laser and then attached to a printing machine, or after being attached to a printing machine and image-exposed with an infrared laser to form the lithographic printing plate precursor A method for making a lithographic printing plate precursor by supplying printing ink and fountain solution to remove unexposed portions of the image recording layer.