JP2005319758A - Lithographic printing method, and lithographic printing plate original plate used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic printing method which can directly record an image from digital data by using a lithographic printing plate original plate being able to record images with an infrared laser, and can perform an on-board development. <P>SOLUTION: This lithographic printing method has a process in which this lithographic printing plate original plate having a recording layer containing at least (A) an infrared ray absorbing agent (B) a polymerization initiator represented by general formula (1) and (C) a polymeric compound is exposed with the infrared laser, and a printing process in which printing is performed by feeding an oily ink and a water-soluble component to the lithographic printing plate original plate after the exposure without applying any kind of developing treatment. In the middle of the printing process, a non-exposed section of the recording layer is eliminated. In general formula (1), X represents a bivalent combining group, and Y, Q and Z each independently represent a monovalent substituent comprising a hydrogen atom or a non-metal atom. X preferably represents a carbonyl group, a sulfone group or a sulfoxide group, Y preferably represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a benzoyl group or a heterocyclic group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithographic printing plate precursor and a lithographic printing method using the same. Specifically, a lithographic printing plate precursor capable of direct plate making that can be directly made by scanning an infrared laser based on a digital signal from a computer or the like, and the lithographic printing plate precursor subjected to a development processing step The present invention also relates to a lithographic printing method in which development is performed directly on a printing 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 has been widely used. Normally, after exposing a lithographic printing plate precursor through an original image such as a lithographic film, the image recording layer in the image area remains, and the image recording layer in the non-image area is dissolved with an alkaline developer or an organic solvent. The lithographic printing plate is obtained by carrying out plate making by a method of exposing the surface of the hydrophilic support by removing it.

  In the conventional plate-making process of a lithographic printing plate precursor, a step of dissolving and removing the non-image area with a developing solution or the like corresponding to the image recording layer is necessary after exposure. One of the problems has been to make it unnecessary or simplified. In particular, in recent years, the disposal of waste liquid discharged with wet processing has become a major concern for the entire industry due to consideration for the global environment, and there is an increasing demand for the solution of the above problems.

On the other hand, as one of simple plate making methods, an image recording layer that can remove a non-image portion of a lithographic printing plate precursor in a normal printing process is used. A method called on-press development has been proposed in which a part is removed to obtain a lithographic printing plate.
As a specific method of on-press development, for example, a method using a lithographic printing plate precursor having an image recording layer that can be dissolved or dispersed in a dampening water, an ink solvent, or an emulsion of a dampening water and an ink, A method of mechanically removing the image recording layer by contact with rollers or a blanket cylinder of a printing press, cohesion of the image recording layer or adhesion between the image recording layer and the support by penetration of dampening water, ink solvent, etc. An example is a method in which after the force is weakened, the image recording layer is mechanically removed by contact with rollers or a blanket cylinder.
In the present invention, unless otherwise specified, the “development process step” refers to using a device other than a printing press (usually an automatic developing machine) and bringing a liquid (usually an alkaline developer) into contact therewith. Refers to the process of removing the infrared laser unexposed portion of the lithographic printing plate precursor to expose the surface of the hydrophilic support, and “on-press development” refers to a process using a printing machine (typically printing ink and / or printing ink). Or a dampening solution) to remove the infrared laser unexposed portion of the lithographic printing plate precursor and expose the surface of the hydrophilic support.

  However, when an image recording layer of a conventional image recording system using ultraviolet rays or visible light is used, the image recording layer does not fix even after exposure. For example, the lithographic plate after exposure until it is mounted on a printing press. It was necessary to take a time-consuming method such as storing the printing plate precursor completely in a light-shielded state or under constant temperature conditions.

  On the other hand, in recent years, digitization techniques for electronically processing, storing, and outputting image information using a computer have become widespread, and various new image output methods corresponding to such digitization techniques have been put into practical use. It is becoming. Along with this, digitized image information is carried by high-convergence radiation such as laser light, and the lithographic printing plate precursor is scanned and exposed with that light, directly without using a lithographic film. Computer-to-plate technology for manufacturing is attracting attention. Therefore, obtaining a lithographic printing plate precursor adapted to such a technique is one of the important technical issues.

  As described above, in recent years, the simplification, drying, and no processing of plate making operations have become more desirable than ever in terms of consideration for the global environment and adaptation to digitalization. It is coming.

Recently, high-power lasers such as semiconductor lasers and YAG lasers have become available at low cost, so these high-power lasers can be used as a method for producing lithographic printing plates by scanning exposure that can be easily incorporated into digitization technology. The method used as a means is promising.
In the conventional plate-making method, imagewise exposure is performed on a photosensitive lithographic printing plate precursor at low to medium illuminance, and image recording is performed by image-like physical property change due to a photochemical reaction in an image recording layer. In contrast, in the method using the above-described high-power laser, a large amount of light energy is irradiated to the exposure region in an extremely short time, and the light energy is efficiently converted into heat energy. In the process, a thermal change such as a chemical change, a phase change, a change in form or structure is caused, and the change is used for image recording. Accordingly, image information is input by light energy such as laser light, but image recording is performed in a state in which reaction by heat energy is taken into account in addition to light energy. Usually, such a recording method using heat generated by high power density exposure is called heat mode recording, and changing light energy to heat energy is called photothermal conversion.

  The major advantages of plate-making methods using heat mode recording are that the image recording layer is not exposed to light at normal illuminance levels such as room lighting, and that images recorded by high-illuminance exposure do not necessarily require fixing. It is in. That is, the lithographic printing plate precursor used for heat mode recording is not likely to be exposed to room light before exposure, and image fixing is not essential after exposure. Therefore, for example, if an image recording layer that is insolubilized or solubilized by exposure using a high-power laser is used, and the plate making process in which the exposed image recording layer is imaged to form a lithographic printing plate is carried out by on-machine development, exposure is performed. Later, a printing system is possible in which the image is not affected even if it is exposed to ambient light in the room. Therefore, if heat mode recording is used, it is expected that a lithographic printing plate precursor suitably used for on-press development can be obtained.

In recent years, the development of lasers has been remarkable, and in particular, semiconductor lasers and solid-state lasers that emit infrared light with a wavelength of 760 to 1200 nm can be easily obtained with high output and small size. Such an infrared laser is extremely useful as a recording light source for making a plate directly from digital data such as a computer.
However, many of the photosensitive recording materials that are practically useful as an image recording layer are in the visible light range with a photosensitive wavelength of 760 nm or less, and therefore cannot record images with an infrared laser. For this reason, a material capable of recording an image with an infrared laser is desired.

  As such an image recording material, for example, a lithographic printing plate precursor in which an image forming layer in which hydrophobic thermoplastic polymer particles are dispersed in a hydrophilic binder is provided on a hydrophilic support has been proposed ( For example, see Patent Document 1.) This lithographic printing plate precursor is exposed by an infrared laser, and the hydrophobic thermoplastic polymer particles are coalesced by heat to form an image, which is then mounted on a cylinder of a printing machine, and is dampened with dampening water and / or ink. Although it is possible to perform on-press development and exhibits good on-press developability, in the method of forming an image by mere thermal fusion of fine particles as described above, the formed image strength, particularly the support and the ink There was a problem that the adhesion with the receiving layer was extremely weak and the printing durability was insufficient.

In addition, as another example of a lithographic printing plate precursor capable of such on-press development, a lithographic printing plate containing a microcapsule containing a polymerizable compound on a hydrophilic support (for example, Patent Documents 2 and 3). And a planographic printing plate precursor (see, for example, Patent Document 4) in which a photosensitive layer containing an infrared absorber, a radical polymerization initiator, and a polymerizable compound is provided on a support. Yes.
The image portion obtained by the method of forming an image by using the polymerization reaction as described above has a relatively high image strength because the chemical bond density of the image portion is higher than that of the image portion formed by thermal fusion of the polymer fine particles. However, from a practical point of view, both on-press developability and printing durability are still insufficient and have not yet been put into practical use.
Japanese Patent No. 2938397 JP 2001-277740 A JP 2001-277742 A JP 2002-287334 A

An object of the present invention made in consideration of the above problems is to record an image by infrared laser exposure directly from digital data of a computer or the like using a lithographic printing plate precursor capable of recording an image with a laser emitting infrared rays. Another object of the present invention is to provide a lithographic printing method capable of obtaining a large number of good prints with a practical amount of energy by being subjected to on-press development by being subjected to a printing step without performing any development processing step.
A further object of the present invention is to provide a lithographic printing plate precursor suitably used in the lithographic printing method of the present invention.

As a result of earnest research focusing on the constituent components of the negative type image recording material used in the image recording layer of the lithographic printing plate precursor, the present inventor has found that the above object is achieved by using a compound having a specific structure as a polymerization initiator. And the present invention has been completed.
That is, the lithographic printing method of the present invention comprises, on a support, at least (A) an infrared absorber and (B) a polymerization initiator having a structure represented by the following general formula (1). A lithographic printing plate precursor having an image recording layer that can be recorded by infrared irradiation, imagewise exposure with an infrared laser, and exposure. A printing process for printing by supplying an oil-based ink and an aqueous component to the subsequent lithographic printing plate precursor without any development treatment, and an infrared laser for the lithographic printing plate precursor in the course of the printing process An unexposed portion is removed.

  In General Formula (1), X represents a divalent linking group, and Y, Q, and Z each independently represent a monovalent substituent composed of a hydrogen atom or a nonmetal atom.

  The lithographic printing plate precursor according to claim 4 of the present invention comprises, on a support, at least (A) an infrared absorber and (B) a polymerization initiator having a structure represented by the general formula (1) (specific polymerization initiation) Agent) and (C) a polymerizable compound, and has an image recording layer that can be removed by printing ink and / or fountain solution.

  Further, the lithographic printing method of the present invention or the image recording layer of the lithographic printing plate precursor preferably contains microcapsules, and further preferably contains (D) a binder polymer.

Although the mechanism of action of the present invention is not clear, it is presumed as follows.
In general, in the case of an on-press development type lithographic printing plate precursor using an ionic polymerization initiator, an ionic compound that could not be decomposed by exposure remains in the image area, so There is a concern that the printing portion is liable to be damaged and the printing durability of the image portion is lowered. However, since the specific polymerization initiator (B), which is a characteristic component of the present invention, is nonionic, there is no undecomposed ionic compound remaining in the image area, so that it is damaged by the fountain solution or the like. It is considered that excellent printing durability is maintained without concern.
In addition, the specific polymerization initiator that is nonionic is caused by the strong interaction between ions and various polar groups present in other components even when left under conditions such as high temperatures. It is considered that there is no concern about the deterioration of the removability of the non-image area over time, and excellent on-press developability is maintained.
Since the lithographic printing plate precursor of the present invention using such a specific polymerization initiator has good printing durability and on-press developability over time (stability over time), it is preferably used in the lithographic printing method of the present invention. It is thought that

According to the lithographic printing method of the present invention, an image is recorded by infrared laser exposure directly from digital data of a computer or the like using a lithographic printing plate precursor capable of recording an image with a laser emitting infrared rays, and any development is performed. By performing the printing process without performing the processing process, it can be developed on the machine and a large number of good printed matter can be obtained with a practical amount of energy.
Further, the lithographic printing plate precursor according to the present invention is excellent in printing durability and on-press developability with time (stability over time), and has the effect of being suitably used in the lithographic printing method according to the present invention.

Hereinafter, the present invention will be described in detail.
The lithographic printing method of the present invention comprises (A) an infrared absorber, (B) a polymerization initiator (specific polymerization initiator) having a structure represented by the general formula (1), and (C) polymerization on a support. And a lithographic printing plate precursor having an image recording layer that can be recorded by irradiation with infrared rays. Hereinafter, the configuration of the lithographic printing plate precursor suitably used in the lithographic printing method of the present invention will be described.

[Lithographic printing plate precursor]
(Image recording layer)
The lithographic printing plate precursor according to the invention contains (A) an infrared absorber, (B) a specific polymerization initiator, and (C) a polymerizable compound on a support, and can be recorded by infrared irradiation. It has an image recording layer.
In this planographic printing plate precursor, the exposed portion of the image recording layer is cured by irradiation with infrared rays to form a hydrophobic (lipophilic) region. After exposure of this lithographic printing plate precursor, without performing any development processing, when dampening water and ink are supplied and printing is started, uncured unexposed areas are dampened in the initial stage. It is quickly removed from the support by an emulsion of ink or fountain solution and ink. That is, the image recording layer is an image recording layer that can be removed by printing ink and / or fountain solution. Hereinafter, each component of the image recording layer will be described.
First, (B) specific polymerization initiator, which is a characteristic component of the present invention, will be described.

<(B) Specific polymerization initiator>
The specific polymerization initiator used in the present invention is an oxime derivative represented by the following general formula (1).

In the general formula (1), X represents a divalent linking group, and Y, Q, and Z each independently represent a monovalent substituent composed of a hydrogen atom or a nonmetal atom.
X is not particularly limited as long as it is a divalent linking group, and any group can be used. Preferred examples of X include a carbonyl group, a sulfonyl group, a sulfinyl group, and a methylene group.
Y represents a monovalent substituent composed of a hydrogen atom or a nonmetallic atom, and the monovalent substituent composed of a nonmetallic atom is not particularly limited, but preferred examples of Y include an alkyl group, an alkenyl group, and an alkynyl group. Group, aryl group, benzoyl group, heterocyclic group, alkoxy group, aryloxy group, hydrogen atom and the like, more specifically, a cyclic or chain alkyl group having 1 to 12 carbon atoms, an alkenyl group, an alkynyl group. Preferable examples include aryl groups having 6 to 18 carbon atoms, heterocyclic groups, and benzoyl groups.
Q and Z each independently represent a monovalent substituent consisting of a hydrogen atom or a nonmetallic atom, and the monovalent substituent consisting of a nonmetallic atom is not particularly limited, and any of them can be introduced. However, examples of preferable Q and Z include those preferably mentioned above for Y, and further, a cyano group, an amino group, an alkylcarbonyl group, an arylcarbonyl group, a thioalkoxy group, a thioaryloxy group, and the like. In addition, the monovalent substituent composed of a nonmetallic atom used here has a substituent containing one or more atoms selected from the group consisting of a hydrogen atom, an oxygen atom, a halogen atom, a nitrogen atom, and a sulfur atom. You may do it.

As the aryl group when Y represents an aryl group, aromatic hydrocarbon compounds such as a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene group, a pyrene group, and a triphenylene group are preferable. In addition, examples of the heterocyclic group include aromatic compounds having at least one hetero atom selected from a nitrogen atom, a sulfur atom, and an oxygen atom in the ring structure, such as a pyrrole group, a furan group, a thiophene group, a selenophene group, Pyrazole group, imidazole group, triazole group, tetrazole group, oxazole group, thiazole group, indole group, benzofuran group, benzimidazole group, benzoxazole group, benzothiazole group, pyridine group, pyrimidine group, pyrazine group, triazine group, quinoline group , Carbazole group, acridine group, phenoxazine, phenothiazine and the like.
The substituent represented by Y may further have a substituent, such as a halogen atom, a hydroxyl group, a nitrile group, a nitro group, a carboxy group, an aldehyde group, an alkyl group, a thiol group, Aryl group, alkenyl group, alkynyl group, alkoxy group, alkoxycarbonyl group, amino group, thioalkoxy group, thioaryloxy group, sulfo group, aryloxy group, aryloxycarbonyl group, hydrazino group, imino group, phosphoroso group, phospho group And a carbonyl ether group. These may be introduced directly, but via one or more of divalent groups such as carbonyl group, amide group, urea group, urethane group, sulfonyl group, sulfinyl group, ether group, disulfide group, ester group and the like. May be introduced.

In the general formula (1), Q and Z each independently represent a monovalent substituent consisting of a hydrogen atom or a nonmetallic atom, preferably a nitrile group, a halogen atom, a hydrogen atom, an amino group, and the above The organic group mentioned by Y is mentioned.
The substituent represented by Z may further have a substituent. Examples of such a substituent include a halogen atom, a hydroxyl group, a nitrile group, a nitro group, a carboxy group, an aldehyde group, an alkyl group, a thiol group, Examples include aryl group, alkenyl group, alkynyl group, ether group, ester group, amino group, sulfide group, disulfide group, sulfo group, hydrazino group, imino group, phosphoroso group, carbonyl ether group and the like. These may be introduced directly, or may be introduced via one or more of divalent groups such as a carbonyl group, an amide group, a urea group, a urethane group, a sulfonyl group, a sulfinyl group, and an ether group. Good.

  As a more preferred embodiment of the polymerization initiator represented by the general formula (1), a compound represented by the following general formula (2) is exemplified.

In the general formula (2), X represents a divalent linking group, but is preferably a carbonyl group, a sulfonyl group, or a sulfinyl group. From the viewpoint of sensitivity and stability, the carbonyl group and the sulfonyl group are Most preferred.
Y has the same meaning as that represented by the general formula (1), but a cyclic or chain alkyl group having 1 to 12 carbon atoms, an alkenyl group, an alkynyl group, an aryl group having 6 to 18 carbon atoms, or a complex. A cyclic group is preferable, and from the viewpoint of sensitivity, an aryl group or a benzoyl group is more preferable, and a halogen atom, nitrile group, nitro group, aryl group, hydroxyl group, alkyl group, thiol group, carboxy group, ether is particularly preferable. And an aryl group or a benzoyl group which may be substituted with a substituent selected from the group.
Z has the same meaning as in the general formula (1), and preferably an alkyl group or an aryl group from the viewpoint of sensitivity, and particularly preferably a halogen atom, a nitrile group, a nitro group, an aryl group, Examples thereof include an alkyl group or an aryl group which may be substituted with a substituent selected from a hydroxyl group, an alkyl group, a thiol group, a carboxy group, and an ether group.
W is preferably a carbonyl group, a sulfonyl group, an ether group or an amino group, more preferably a carbonyl group. n represents an integer of 0 or 1.

V is preferably a cyclic or chain alkyl group having 1 to 12 carbon atoms, an alkenyl group, an alkynyl group, an aryl group having 6 to 18 carbon atoms, an alkoxy group, or an aryloxy group. Is an aromatic hydrocarbon compound such as benzene ring, naphthalene ring, anthracene ring, phenanthrene group, pyrene group, triphenylene group, pyrrole group, furan group, thiophene group, selenophene group, pyrazole group, imidazole group, triazole group, tetrazole group, Oxazole group, thiazole group, indole group, benzofuran group, benzimidazole group, benzoxazole group, benzothiazole group, pyridine group, pyrimidine group, pyrazine group, triazine group, quinoline group, carbazole group, acridine group, phenoxazine, phenothiazine, etc. Hetero field Containing aromatic compound is preferably mentioned, among others, and more preferably an aryl group.
The monovalent organic group represented by V may further have a substituent. Examples of such a substituent include a halogen atom, a hydroxyl group, a nitrile group, a nitro group, a carboxy group, an aldehyde group, an alkyl group, Thiol group, aryl group, alkenyl group, alkynyl group, alkoxy group, alkoxycarbonyl group, amino group, thioalkoxy group, thioaryloxy group, sulfo group, hydrazino group, imino group, phosphoroso group, phospho group, carbonyl ether group, etc. Is mentioned. These may be introduced directly, but via one or more of divalent groups such as carbonyl group, amide group, urea group, urethane group, sulfonyl group, sulfinyl group, ether group, disulfide group, ester group and the like. May be introduced.
V and Z may be bonded to each other to form a ring.

The preferred specific polymerization initiator used in the present invention is a compound represented by the general formula (2) from the viewpoint of sensitivity, wherein X is a carbonyl group, Y is an aryl group or benzoyl group, and Z group is an alkyl group. Or, an aryl group, W is a carbonyl group, and V is an aryl group are preferred. More preferred is a compound in which V is an aryl group having a thioether substituent.
Note that the structure of the N—O bond in the general formula (1) or the general formula (2) may be E-form or Z-form.

  Other examples of oxime derivatives that can be suitably used as the specific polymerization initiator in the present invention include “Progress in Organic Coatings”, Vol. 13 (1985) p123-150; "JC S Perkin II", (1979), p1653-1660; "Journal of Photoscience Science and Technology" (1995) p205-232; "JC S Perkin II". (1979) p156-162; JP-A 2000-66385; JP-A 2000-80068.

  Specific examples of the specific polymerization initiator [Exemplary compounds (OS-1) to (OS-99)] preferably used in the present invention are listed below, but the present invention is not limited thereto.

The specific polymerization initiator is preferably contained in a proportion of 0.1 to 40% by mass with respect to the total solid content constituting the image recording layer, from the viewpoint of sensitivity and the difficulty of smearing the non-image area during printing. More preferably, it is contained in a proportion of 0.5 to 30% by mass, particularly preferably in a proportion of 1 to 20% by mass.
These specific polymerization initiators may be used alone or in combination of two or more. Moreover, these polymerization initiators may be added to the same layer as other components, or another layer may be provided and added thereto.

In the image recording layer according to the present invention, a general polymerization initiator other than the specific polymerization initiator may be used in combination as long as the effect is not impaired. The polymerization initiator that can be used in combination is not particularly limited as long as it is a compound that generates radicals by energy of light, heat, or both, and starts and accelerates polymerization of the polymerizable compound (C) described later. For example, a known thermal polymerization initiator, a compound having a bond with a small bond dissociation energy, a photopolymerization initiator, and the like can be mentioned. Particularly preferably, a radical is generated by thermal energy, and the polymerizable compound Examples thereof include a thermal polymerization initiator that initiates and accelerates polymerization.
In the present invention, such a polymerization initiator can be appropriately selected and used. Moreover, 1 type (s) or 2 or more types of such a polymerization initiator can be used together.

Suitable polymerization initiators for use in the present invention include, for example, organic halogenated compounds, carbonyl compounds, organic peroxide compounds, azo polymerization initiators, azide compounds, metallocene compounds, hexaarylbiimidazole compounds, organic boron compounds. And acid compounds and onium salt compounds.
The above general polymerization initiator can be added within a range that does not impair the performance of the specific polymerization initiator, but it is preferably not more than the added weight of the specific polymerization initiator. It is particularly preferably 50% by weight or less based on the amount added.

<(A) Infrared absorber>
The image recording layer of the lithographic printing plate precursor according to the invention preferably contains an infrared absorbent having an absorption maximum at 700 to 1200 nm from the viewpoint of improving sensitivity. By adding such a compound, the image recording layer of the lithographic printing plate precursor according to the invention has sensitivity in the infrared wavelength region, and recording by an infrared laser becomes possible.
The compound having an absorption maximum at 700 to 1200 nm is preferably an infrared-absorbing dye or pigment having an absorption maximum at a wavelength of 760 to 1200 nm from the viewpoint of compatibility with an easily available high-power laser.

  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, 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, oxonol dyes And dyes such as diimonium dyes, aminium dyes, and croconium dyes.

  Examples of preferable dyes include cyanine dyes described in, for example, JP-A-58-125246, JP-A-59-84356, JP-A-59-202829, JP-A-60-78787, and the like. Methine dyes described in JP-A-58-173696, JP-A-58-181690, JP-A-58-194595, JP-A-58-112793, JP-A-58- Naphthoquinone dyes described in JP-A-224793, JP-A-59-48187, JP-A-59-73996, JP-A-60-52940, JP-A-60-63744, etc. Examples include squarylium dyes described in JP-A-58-112792, and cyanine dyes described in British Patent 434,875.

  Further, near infrared absorption sensitizers described in US Pat. No. 5,156,938 are also preferably used, and substituted aryl benzoates described in US Pat. No. 3,881,924 are also preferably used. (Thio) pyrylium salt, trimethine thiapyrylium salt described in JP-A-57-142645 (US Pat. No. 4,327,169), JP-A-58-181051, JP-A-58-220143 No. 59-41363, No. 59-84248, No. 59-84249, No. 59-146063, No. 59-146061, JP-A 59-216146 No. 5,13514, a cyanine dye described in US Pat. No. 4,283,475, a pentamethine thiopyrylium salt described in US Pat. No. 4,283,475, and the like. Pyrylium compounds Nos disclosed in Japanese 5-19702 are also preferably used.

  Moreover, as another example preferable as an infrared absorption dye, the near-infrared absorption dye described as Formula (I) and (II) in US Patent 4,756,993 can be mentioned.

  Particularly preferred among these dyes are cyanine dyes, phthalocyanine dyes, oxonol dyes, squarylium dyes, pyrylium salts, thiopyrylium dyes, and nickel thiolate complexes. Furthermore, the dyes represented by the following general formulas (a) to (e) are preferable because they are excellent in photothermal conversion efficiency. Particularly, the cyanine dye represented by the following general formula (a) is used in the photosensitive composition of the present invention. In this case, it is most preferable because it gives a high interaction with the alkali-soluble resin and is excellent in stability and economy.

In formula (a), X ¹ represents a hydrogen atom, a halogen ^{atom, X 2 -L 1, -N (} L 2) (L 3), or a group shown below. Here, X ² represents an oxygen atom, a sulfur atom or a nitrogen atom, and L ¹ represents a hydrocarbon group having 1 to 12 carbon atoms, an aromatic ring having a hetero atom, or 1 to 12 carbon atoms including a hetero atom. Represents a hydrocarbon group. L ² and L ³ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an aryl group, or an aromatic ring containing a hetero atom. L ^{1 to} L ³ may further have a substituent, and examples of the substituent include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a halogen atom, a hydroxy group, an ether group, a thioether group, and a carbonyl group. Carboxy group, cyano group, ester group, amide group, urethane group, urea group, mercapto group, sulfonamide group, amino group, and substituents containing these groups are preferably mentioned. Represents N, S, O, a halogen atom, or Se. Xa ^- the 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 when the photosensitive composition of the present invention is used as a recording layer coating solution for a lithographic printing plate precursor, R ¹ and R ² may be a hydrocarbon group having 2 or more carbon atoms. Further, R ¹ and R ² are preferably bonded to each other 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 aromatic hydrocarbon group which may have a substituent. Preferred aromatic hydrocarbon 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 neutralization of charge is not necessary. Preferred Za ⁻ is a halogen ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a carboxylate ion, and a sulfonate ion because of the storage stability of the recording layer coating solution. From the viewpoint of solubility and solubility in a coating solution, halogen ions and organic acid ions such as carboxylate ions and sulfonate ions are preferable, sulfonate ions are more preferable, and aryl sulfonate ions are particularly preferable.

  Specific examples of the cyanine dye represented by the general formula (a) that can be suitably used in the present invention include those exemplified below, and paragraph numbers [0017] to [0019] of JP-A No. 2001-133969, Examples thereof include those described in paragraph numbers [0012] to [0038] of JP-A No. 2002-40638 and paragraph numbers [0012] to [0023] of JP-A No. 2002-23360.

In the general formula (b), L represents a methine chain having 7 or more conjugated carbon atoms, the methine chain may have a substituent, and the substituents are bonded to each other to form a ring structure. Also good. Zb ⁺ represents a counter cation. Preferred counter cations include ammonium, iodonium, sulfonium, phosphonium, pyridinium, alkali metal cations (Na ⁺ , K ⁺ , Li ⁺ ) and the like. R ^{9 to} R ¹⁴ and R ^{15 to} R ²⁰ are each independently a hydrogen atom or halogen atom, cyano group, alkyl group, aryl group, alkenyl group, alkynyl group, carbonyl group, thio group, sulfonyl group, sulfinyl group, oxy group Or a substituent selected from amino groups, or a combination of two or three of these, and may be bonded to each other to form a ring structure. Here, in the general formula (b), those in which L represents a methine chain having 7 conjugated carbon atoms and those in which R ^{9 to} R ¹⁴ and R ^{15 to} R ²⁰ all represent hydrogen atoms are easily available. From the viewpoint of the effect.

  Specific examples of the dye represented by formula (b) that can be suitably used in the present invention include those exemplified below.

In the general formula (c), Y ³ and Y ⁴ each represent an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom. M represents a methine chain having 5 or more conjugated carbon atoms. R ^{21 to} R ²⁴ and R ^{25 to} R ²⁸ may be the same or different, and are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, an aryl group, an alkenyl group, an alkynyl group, a carbonyl group, a thiol group, Represents a group, a sulfonyl group, a sulfinyl group, an oxy group, or an amino group. Further, wherein Za ^- include a counter anion, Za in the general formula (a) ^- it is synonymous.

  In the present invention, specific examples of the dye represented by formula (c) that can be suitably used include those exemplified below.

In the general formula (d), R ²⁹ to R ³² each independently represent a hydrogen atom, an alkyl group, or an aryl group. R ³³ and R ³⁴ each independently represents an alkyl group, a substituted oxy group, or a halogen atom. n and m each independently represents an integer of 0 to 4. R ²⁹ and R ³⁰ , or R ³¹ and R ³² may be bonded to each other to form a ring, and R ²⁹ and / or R ³⁰ is R ³³ and R ³¹ and / or R ³² is R ³⁴ A ring may be bonded to each other, and when a plurality of R ³³ or R ³⁴ are present, R ³³ or R ³⁴ may be bonded to each other to form a ring. X ¹ and X ² are each independently a hydrogen atom, an alkyl group, or an aryl group, and at least one of X ¹ and X ² represents a hydrogen atom or an alkyl group. Q is a trimethine group or a pentamethine group which may have a substituent, and may form a ring structure together with a divalent organic group. Zc ⁻ represents a counter anion and has the same meaning as Za ⁻ in the general formula (a).

  In the present invention, specific examples of the dye represented by the general formula (d) that can be suitably used include those exemplified below.

In the general formula (e), R ^{35 to} R ⁵⁰ are each independently a hydrogen atom, a halogen atom, a cyano group, an alkyl group, an aryl group, an alkenyl group, an alkynyl group, a hydroxyl group, or a carbonyl group that may have a substituent. Group, thio group, sulfonyl group, sulfinyl group, oxy group, amino group, and onium salt structure. M represents two hydrogen atoms or metal atoms, a halometal group, and an oxymetal group, and the metal atoms contained therein include IA, IIA, IIIB, IVB group atoms of the periodic table, first, second, second Three-period transition metals and lanthanoid elements can be mentioned, among which copper, magnesium, iron, zinc, cobalt, aluminum, titanium, and vanadium are preferable.

  In the present invention, specific examples of the dye represented by formula (e) that can be suitably used include those exemplified below.

  In the present invention, as the pigment used as the component (C), commercially available pigments and color index (CI) manual, “Latest Pigment Handbook” (edited by Japan Pigment Technical Association, published in 1977), “Latest Pigment Application” Examples thereof include pigments described in “Technology” (CMC Publishing, 1986) and “Printing Ink Technology” CMC Publishing, 1984).

  Examples of the pigment include black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and other polymer-bonded dyes. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments In addition, quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like can be used. Among these pigments, carbon black is preferable.

  These pigments may be used without surface treatment, or may be used after surface treatment. The surface treatment method includes a method of surface coating with a resin or wax, a method of attaching a surfactant, a method of bonding a reactive substance (eg, silane coupling agent, epoxy compound, polyisocyanate, etc.) to the pigment surface, etc. Can be considered. The above-mentioned surface treatment methods are described in “Characteristics and Applications of Metal Soap” (Shobobo), “Printing Ink Technology” (CMC Publishing, 1984) and “Latest Pigment Application Technology” (CMC Publishing, 1986). Yes.

  The particle size of the pigment is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.05 to 1 μm, and particularly preferably in the range of 0.1 to 1 μm. When the particle diameter of the pigment is less than 0.01 μm, it is not preferable from the viewpoint of stability of the dispersion in the image recording layer coating solution, and when it exceeds 10 μm, it is not preferable from the viewpoint of uniformity of the image recording layer.

  As a method for dispersing the pigment, a known dispersion technique used in ink production, toner production, or the like can be used. Examples of the disperser include an ultrasonic disperser, a sand mill, an attritor, a pearl mill, a super mill, a ball mill, an impeller, a disperser, a KD mill, a colloid mill, a dynatron, a three-roll mill, and a pressure kneader. Details are described in "Latest Pigment Applied Technology" (CMC Publishing, 1986).

(A) Infrared absorber in this invention may use only 1 type, and can also use 2 or more types together.
As the (A) infrared absorber in the present invention, a cyanine dye is preferable.
From the viewpoint of sensitivity, the cyanine dye represented by the general formula (a) is more preferable. Among the cyanine dyes represented by the general formula (a), a cyanine dye in which X ¹ is a diarylamino group or X ² -L ¹ is used. Preferably, a cyanine dye having a diarylamino group is more preferable.
In addition, cyanine dyes having an electron-withdrawing group or a heavy atom-containing substituent at both indolenine sites are also preferable. For example, those described in Japanese Patent Application No. 2001-6323 are preferably used. Most preferably, X ¹ is a diarylamino group and is a cyanine dye having an electron-withdrawing group at both indolenine sites.

These infrared absorbers may be added to the same layer as other components, or may be added to another layer provided, but when a negative planographic printing plate precursor is prepared, image recording is performed. The layer is added so that the absorbance at the maximum absorption wavelength in the wavelength range of 760 nm to 1200 nm is in the range of 0.3 to 1.2 by the reflection measurement method. Preferably, it is the range of 0.4-1.1. Within this range, a uniform polymerization reaction in the depth direction of the image recording layer proceeds, and good film strength of the image area and adhesion to the support can be obtained.
The absorbance of the image recording layer can be adjusted by the amount of infrared absorber added to the image recording layer and the thickness of the image recording layer. Absorbance can be measured by a conventional method. As a measuring method, for example, on a reflective support such as aluminum, an image recording layer having a thickness appropriately determined in a range in which the coating amount after drying is necessary as a lithographic printing plate is formed, and the reflection density is set to the optical density. And a method of measuring with a spectrophotometer by a reflection method using an integrating sphere.
In terms of the content of the infrared absorber, from the viewpoint of sensitivity and film uniformity, 0.01 to 50% by mass is preferable in the total solid content constituting the image recording layer, and more preferably 0. The range is from 1 to 15% by mass. In particular, in the case of a dye, the range is 0.5 to 15% by mass, preferably 1 to 10% by mass, and in the case of a pigment, the range is 0.1 to 15% by mass, preferably 1 to 10% by mass.

<(C) Polymerizable compound>
The polymerizable compound that can be used in the present invention is an addition polymerizable compound having at least one ethylenically unsaturated double bond, and is a compound having at least one terminal ethylenically unsaturated bond, preferably two or more. To be elected. Such a compound group is widely known in the industrial field, and can be used without any particular limitation in the present invention. These have chemical forms such as monomers, prepolymers, i.e. dimers, trimers and oligomers, or mixtures thereof and copolymers thereof. Examples of monomers and copolymers thereof include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), and esters and amides thereof. In this case, an ester of an unsaturated carboxylic acid and an aliphatic polyhydric alcohol compound, or an amide of an unsaturated carboxylic acid and an aliphatic polyvalent amine compound is used. In addition, an addition reaction product of an unsaturated carboxylic acid ester or amide having a nucleophilic substituent such as a hydroxyl group, amino group or mercapto group with a monofunctional or polyfunctional isocyanate or epoxy, and monofunctional or polyfunctional 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.

  Specific examples of the monomer of an ester of an aliphatic polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as ethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate, and tetramethylene glycol. Diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1,4-cyclohexanediol diacrylate , Tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate , Pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligomer, isocyanuric acid There are EO-modified triacrylate, 2,2-bis [4- (acryloxydiethoxy) phenylpropane] and the like.

  Methacrylic acid esters include tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, Hexanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, bis [p- (3-methacryloxy- 2-hydroxypro ) Phenyl] dimethyl methane, bis - [p- (methacryloxyethoxy) phenyl] dimethyl methane.

  Itaconic acid esters include ethylene glycol diitaconate, propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanediol diitaconate, tetramethylene glycol diitaconate, pentaerythritol diitaconate And sorbitol tetritaconate. Examples of crotonic acid esters include ethylene glycol dicrotonate, tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, and sorbitol tetradicrotonate. Examples of isocrotonic acid esters include ethylene glycol diisocrotonate, pentaerythritol diisocrotonate, and sorbitol tetraisocrotonate. Examples of maleic acid esters include ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, and sorbitol tetramaleate.

  Examples of other esters include aliphatic alcohol esters described in JP-B-51-47334 and JP-A-57-196231, JP-A-59-5240, JP-A-59-5241, and JP-A-2-226149. Those having the aromatic skeleton described above and those having an amino group described in JP-A-1-165613 are also preferably used. Furthermore, the ester monomers described above can also be used as a mixture.

  Specific examples of amide monomers of aliphatic polyvalent amine compounds and unsaturated carboxylic acids include methylene bis-acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, 1,6-hexamethylene bis. -Methacrylamide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, xylylene bismethacrylamide and the like. Examples of other preferable amide monomers include those having a cyclohexylene structure described in JP-B-54-21726.

  In addition, urethane-based addition polymerizable compounds produced by using an addition reaction of isocyanate and hydroxyl group are also suitable, and specific examples thereof include, for example, one molecule described in JP-B-48-41708. A vinyl urethane containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxyl group represented by the following general formula (3) to a polyisocyanate compound having two or more isocyanate groups. Compounds and the like.

^{_{CH 2 = C (R 4)}} COOCH 2 CH (R 5) OH ··· formula (3)
(In the general formula (3), R ⁴ and R ⁵ represent H or CH _3. )

  Also, urethane acrylates such as those described in JP-A-51-37193, JP-B-2-32293, and JP-B-2-16765, JP-B-58-49860, JP-B-56-17654, Urethane compounds having an ethylene oxide skeleton described in JP-B-62-39417 and JP-B-62-39418 are also suitable. Further, by using addition polymerizable compounds having an amino structure or a sulfide structure in the molecule described in JP-A-63-277653, JP-A-63-260909, and JP-A-1-105238, It is possible to obtain a photopolymerizable composition excellent in the photosensitive speed.

  Other examples include polyester acrylates, epoxy resins and (meth) acrylic acid as described in JP-A-48-64183, JP-B-49-43191, JP-B-52-30490, and JP-A-52-30490. Mention may be made of polyfunctional acrylates and methacrylates such as reacted epoxy acrylates. Further, specific unsaturated compounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, vinylphosphonic acid compounds described in JP-A-2-25493, and the like can also be mentioned. . In some cases, a structure containing a perfluoroalkyl group described in JP-A-61-22048 is preferably used. Furthermore, Journal of Japan Adhesion Association vol. 20, no. 7, pages 300 to 308 (1984), which are introduced as photocurable monomers and oligomers, can also be used.

About these addition polymerizable compounds, the details of usage, such as the structure, single use or combination, addition amount, etc. can be arbitrarily set according to the performance design of the final lithographic printing plate precursor. For example, it is selected from the following viewpoints.
From the viewpoint of sensitivity, a structure having a large unsaturated group content per molecule is preferable, and in many cases, a bifunctional or higher functionality is preferable. Further, in order to increase the strength of the image portion, that is, the cured film, those having three or more functionalities are preferable, and further, different functional numbers and different polymerizable groups (for example, acrylic acid ester, methacrylic acid ester, styrene compound, vinyl ether type). A method of adjusting both sensitivity and strength by using a compound) is also effective.
Further, the selection and use method of the addition polymerization compound is also an important factor for the compatibility and dispersibility with other components (for example, binder polymer, initiator, colorant, etc.) in the image recording layer. In some cases, the compatibility can be improved by using a low-purity compound or by using two or more kinds in combination. In addition, a specific structure may be selected for the purpose of improving the adhesion of the substrate and an overcoat layer described later.
The addition polymerizable compound is preferably used in the range of 5 to 80% by mass, more preferably 25 to 75% by mass with respect to the nonvolatile component in the image recording layer. These may be used alone or in combination of two or more. In addition, the use method of the addition polymerizable compound can be arbitrarily selected from the viewpoint of polymerization inhibition with respect to oxygen, resolution, fogging property, refractive index change, surface adhesiveness, etc. Depending on the case, a layer configuration and coating method such as undercoating and overcoating can be performed.

<(D) Binder polymer>
The image recording layer according to the present invention preferably contains (D) a binder polymer. As the binder polymer that can be used in the present invention, conventionally known binder polymers can be used without limitation, and among them, it is preferable to use a linear organic polymer having a film property. Examples of such binder polymers include acrylic resins, polyvinyl acetal resins, polyurethane resins, polyurea resins, polyimide resins, polyamide resins, epoxy resins, methacrylic resins, polystyrene resins, novolac phenolic resins, polyester resins, and synthetic rubbers. And natural rubber.
The binder polymer preferably has crosslinkability in order to improve the film strength of the image area. In order to impart crosslinkability to the binder polymer, a crosslinkable functional group such as an ethylenically unsaturated bond may be introduced into the main chain or side chain of the polymer. The crosslinkable functional group may be introduced by copolymerization.
Examples of the polymer having an ethylenically unsaturated bond in the main chain of the molecule include poly-1,4-butadiene and poly-1,4-isoprene.
Examples of polymers having an ethylenically unsaturated bond in the side chain of the molecule are polymers of esters or amides of acrylic acid or methacrylic acid where the ester or amide residue (R of -COOR or -CONHR) is Mention may be made of polymers having an ethylenically unsaturated bond.

Examples of the residue (the R) having an ethylenically unsaturated _{bond, - (CH 2) n CR} 1 = CR 2 R 3, - (CH 2 O) n CH 2 CR 1 = CR 2 R 3, - _{(CH 2 CH 2 O) n} CH 2 CR 1 = CR 2 R 3, - (CH 2) n NH-CO-O-CH 2 CR 1 = CR 2 R 3, - (CH 2) n -O-CO —CR ¹ ═CR ² R ³ and — (CH ₂ CH ₂ O) ₂ —X (wherein R ^{1 to} R ³ are each a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, Represents an alkoxy group or an aryloxy group, and R ¹ and R ² or R ³ may combine with each other to form a ring, n represents an integer of 1 to 10. X represents dicyclopentadienyl. Represents a residue).
Specific examples of the ester _{residue, -CH 2 CH = CH 2,} ( described in JP Kokoku _{7-21633.) - CH 2 CH 2} O-CH 2 CH = CH 2, -CH 2 C _{(CH 3) = CH 2,} -CH 2 CH = CH-C 6 H 5, -CH 2 CH 2 OCOCH = CH-C 6 H 5, -CH 2 CH 2 -NHCOO-CH 2 CH = CH 2 and - CH ₂ CH ₂ O—X (wherein X represents a dicyclopentadienyl residue).
Specific examples of the amide residue include —CH ₂ CH═CH ₂ , —CH ₂ CH ₂ —Y (wherein Y represents a cyclohexene residue), —CH ₂ CH ₂ —OCO—CH═CH _2. Is mentioned.

  In the case of a binder polymer having crosslinkability, for example, free radicals (polymerization initiation radicals or growth radicals in the polymerization process of a polymerizable compound) are added to the crosslinkable functional group, and a polymerization chain of a polymerizable compound is formed directly between polymers. Through addition polymerization, a cross-link is formed between the polymer molecules and cured. Alternatively, atoms in the polymer (eg, hydrogen atoms on carbon atoms adjacent to the functional bridging group) are abstracted by free radicals to form polymer radicals that are bonded to each other so that crosslinking between the polymer molecules occurs. Forms and cures.

  The content of the crosslinkable group in the binder polymer (content of unsaturated double bond capable of radical polymerization by iodine titration) is preferably 0.1 to 10.0 mmol, more preferably 1.0, per 1 g of the binder polymer. -7.0 mmol, most preferably 2.0-5.5 mmol. Within this range, good sensitivity and good storage stability can be obtained.

Further, from the viewpoint of improving the on-press developability in the unexposed portion of the image recording layer, the binder polymer preferably has high solubility or dispersibility in ink and / or fountain solution.
In order to improve solubility or dispersibility in ink, the binder polymer is preferably oleophilic, and in order to improve solubility or dispersibility in dampening water, the binder polymer is hydrophilic. Is preferred. Therefore, in the present invention, it is also effective to use a lipophilic binder polymer and a hydrophilic binder polymer in combination.

  Examples of hydrophilic binder polymers include hydroxy groups, carboxy groups, carboxylate groups, hydroxyethyl groups, polyoxyethyl groups, hydroxypropyl groups, polyoxypropyl groups, amino groups, aminoethyl groups, aminopropyl groups, and ammonium. Preferred are those having a hydrophilic group such as a group, an amide group, a carboxymethyl group, a sulfonic acid group, and a phosphoric acid group.

  Specific examples include gum arabic, casein, gelatin, starch derivatives, carboxymethylcellulose and its sodium salt, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymers, styrene-maleic acid copolymers, polyacrylic acids and their salts, Polymethacrylic acids and their salts, homopolymers and copolymers of hydroxyethyl methacrylate, homopolymers and copolymers of hydroxyethyl acrylate, homopolymers and copolymers of hydroxypropyl methacrylate, homopolymers and copolymers of hydroxypropyl acrylate, homopolymers of hydroxybutyl methacrylate Polymers and copolymers, homopolymers and copolymers of hydroxybutyl acrylate Polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, hydrolyzed polyvinyl acetate, polyvinyl formal, polyvinyl butyral, polyvinyl pyrrolidone, acrylamide homopolymers and copolymers having a degree of hydrolysis of 60% by mass or more, preferably 80% by mass or more , Homopolymers and polymers of methacrylamide, homopolymers and copolymers of N-methylolacrylamide, polyvinylpyrrolidone, alcohol-soluble nylon, polyether of 2,2-bis- (4-hydroxyphenyl) -propane and epichlorohydrin, etc. Is mentioned.

The binder polymer preferably has a weight average molecular weight of 5000 or more, more preferably 10,000 to 300,000, and a number average molecular weight of 1,000 or more, preferably 2000 to 250,000. More preferred. The polydispersity (weight average molecular weight / number average molecular weight) is preferably 1.1 to 10.
The binder polymer may be any of a random polymer, a block polymer, a graft polymer, and the like, but is preferably a random polymer.

The binder polymer can be synthesized by a conventionally known method. Solvents used in the synthesis include, for example, tetrahydrofuran, ethylene dichloride, cyclohexanone, methyl ethyl ketone, acetone, methanol, ethanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, diethylene glycol dimethyl ether, 1-methoxy. Examples include 2-propanol, 1-methoxy-2-propyl acetate, N, N-dimethylformamide, N, N-dimethylacetamide, toluene, ethyl acetate, methyl lactate, ethyl lactate, dimethyl sulfoxide, and water. These may be used alone or in combination of two or more.
As the radical polymerization initiator used for synthesizing the binder polymer, known compounds such as an azo initiator and a peroxide initiator can be used.

A binder polymer may be used independently or may be used in mixture of 2 or more types.
The content of the binder polymer is 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass with respect to the total solid content of the image recording layer. Within this range, good image area strength and image formability can be obtained.
Moreover, it is preferable to use (C) polymeric compound and (D) binder polymer in the quantity used as 1 / 9-7 / 3 by mass ratio.

<Microcapsule>
The image recording layer according to the present invention preferably further contains microcapsules. Due to the presence of the microcapsules, the capsule wall material melts and adheres closely to the support in the exposed area, or the surface softens and adheres to or adheres to other adjacent microcapsules or to the support surface. Thus, it becomes easy to form a hydrophobic region. In the unexposed area, even if dispersed in a hydrophilic binder, it is easily removed together with the binder with a slight amount of water, so that the image formability is improved. Such a microcapsule may be added as a filler, but may include the above-mentioned image recording layer constituent components (A) to (D) and other constituent components described later.

In the present invention, several modes can be used as a method for incorporating the above-mentioned image recording layer constituent components (A) to (D) and other constituent components described later into the image recording layer. One is a molecular dispersion type image recording layer in which the constituent components are dissolved and applied in an appropriate solvent as described in JP-A-2002-287334, for example. In another embodiment, for example, as described in JP-A-2001-277740 and JP-A-2001-277742, all or part of the constituent components are encapsulated in microcapsules and contained in the image recording layer. It is a capsule type image recording layer. In the image recording layer in the lithographic printing plate precursor according to the invention, it is preferable that at least one of the components constituting the image recording layer is contained in microcapsules.
In the microcapsule type image recording layer, the constituent component may be contained outside the microcapsule. In such a microcapsule-type image recording layer, it is preferable from the viewpoint of obtaining good on-press developability that a hydrophobic constituent component is encapsulated in a microcapsule and a hydrophilic constituent component is contained outside the microcapsule. .

  As a method for microencapsulating at least one of the image recording layer constituent components (A) to (D), a known method can be applied. For example, as a method for producing microcapsules, a method using coacervation found in U.S. Pat. Nos. 2,800,547 and 2,800,498, U.S. Pat. No. 3,287,154, JP-B-38-19574, 42-446 by the interfacial polymerization method, US Pat. No. 3,418,250, US Pat. No. 3,660,304 by precipitation of polymer, US Pat. No. 3,796,669, isocyanate polyol A method using a wall material, a method using an isocyanate wall material found in US Pat. No. 3,914,511, and a urea-formaldehyde system found in US Pat. Nos. 4,001,140, 4,087,376 and 4,089,802. Or urea formaldehyde-resorcinol A method using a wall forming material, a method using a wall material such as melamine-formaldehyde resin, hydroxycellulose, etc. found in US Pat. No. 4,025,445, and Japanese Patent Publication Nos. 36-9163 and 51-9079. In situ method by monomer polymerization, spray drying method found in British Patent No. 930422, US Pat. No. 3,111,407, electrolytic dispersion cooling method seen in British Patent Nos. 952807, 967074, etc. However, it is not limited to these.

  A preferable microcapsule wall used in the present invention has a three-dimensional cross-linking and has a property of swelling with a solvent. From such a viewpoint, the wall material of the microcapsule is preferably polyurea, polyurethane, polyester, polycarbonate, polyamide, and a mixture thereof, and particularly preferably polyurea and polyurethane. Moreover, you may introduce | transduce into a microcapsule wall the compound which has crosslinkable functional groups, such as the ethylenically unsaturated bond which can be introduce | transduced into the said (D) binder polymer.

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

In the image recording layer according to the present invention, in addition to the above essential components, various compounds can be used in combination according to the purpose as long as the effects of the present invention are not impaired. Hereinafter, arbitrary components contained in the image recording layer will be described.
<Surfactant>
In the present invention, it is preferable to add a surfactant to the image recording layer in order to promote on-press developability at the start of printing and to improve the coated surface state. As the surfactant, any of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant may be used, and a fluorosurfactant is also preferred.
Surfactant may be used independently and may be used in combination of 2 or more type.

  The nonionic surfactant used for this invention is not specifically limited, A conventionally well-known thing can be used. For example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, pentaerythritol Fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, Polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N N- bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid ester, trialkylamine oxide, polyethylene glycol, copolymers of polyethylene glycol and polypropylene glycol.

  The anionic surfactant used in the present invention is not particularly limited, and conventionally known anionic surfactants can be used. For example, fatty acid salts, abietic acid salts, hydroxyalkane sulfonates, alkane sulfonates, dialkyl sulfosuccinate esters, linear alkyl benzene sulfonates, branched alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl phenoxy poly Oxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salt, N-alkyl sulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef oil, fatty acid alkyl esters Sulfates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alcohol Ruphenyl ether sulfates, polyoxyethylene styryl phenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, styrene / maleic anhydride Examples thereof include partial saponification products of polymers, partial saponification products of olefin / maleic anhydride copolymers, and naphthalene sulfonate formalin condensates.

The cationic surfactant used in the present invention is not particularly limited, and conventionally known cationic surfactants can be used. Examples thereof include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.
The amphoteric surfactant used in the present invention is not particularly limited, and conventionally known amphoteric surfactants can be used. Examples thereof include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric esters, and imidazolines.

  Of the above surfactants, the term “polyoxyethylene” can be read as “polyoxyalkylene” such as polyoxymethylene, polyoxypropylene, polyoxybutylene, etc. Those surfactants can also be used.

  More preferable surfactants include fluorine-based surfactants containing a perfluoroalkyl group in the molecule. Examples of such fluorosurfactants include anionic types such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates; amphoteric types such as perfluoroalkyl betaines; Cation type such as trimethylammonium salt; perfluoroalkylamine oxide, perfluoroalkylethylene oxide adduct, oligomer containing perfluoroalkyl group and hydrophilic group, oligomer containing perfluoroalkyl group and lipophilic group, perfluoroalkyl Nonionic surfactants such as an oligomer containing a group, a hydrophilic group and a lipophilic group, and a urethane containing a perfluoroalkyl group and a lipophilic group. Moreover, the fluorine-type surfactant described in each gazette of Unexamined-Japanese-Patent No. 62-170950, 62-226143, and 60-168144 is also mentioned suitably.

Surfactant can be used individually or in combination of 2 or more types.
The content of the surfactant is preferably 0.001 to 10% by mass and more preferably 0.01 to 5% by mass with respect to the total solid content of the image recording layer.

<Colorant>
In the present invention, various compounds other than these may be added as necessary. For example, a dye having a large absorption in the visible light region can be used as an image colorant. Specifically, Oil Yellow # 101, Oil Yellow # 103, Oil Pink # 312, Oil Green BG, Oil Blue BOS, Oil Blue # 603, Oil Black BY, Oil Black BS, Oil Black T-505 (orientated chemistry) Manufactured by Kogyo Co., Ltd.), Victoria Pure Blue, Crystal Violet (CI42555), Methyl Violet (CI42535), Ethyl Violet, Rhodamine B (CI145170B), Malachite Green (CI42000), Methylene Blue (CI522015), etc. And dyes described in No. 293247. In addition, pigments such as phthalocyanine pigments, azo pigments, carbon black, and titanium oxide can also be suitably used.
These colorants are preferably added since it is easy to distinguish an image area from a non-image area after image formation. The addition amount is 0.01 to 10% by mass with respect to the total solid content of the image recording material.

<Bakeout agent>
In the image recording layer of the present invention, a compound that changes color by an acid or a radical can be added in order to produce a printout image. As such a compound, for example, various dyes such as diphenylmethane, triphenylmethane, thiazine, oxazine, xanthene, anthraquinone, iminoquinone, azo, and azomethine are effectively used.

  Specific examples include brilliant green, ethyl violet, methyl green, crystal violet, basic fuchsin, methyl violet 2B, quinaldine red, rose bengal, methanyl yellow, thymol sulfophthalein, xylenol blue, methyl orange, paramethyl red, Congo Fred, Benzopurpurin 4B, α-Naphthyl Red, Nile Blue 2B, Nile Blue A, Methyl Violet, Malachide Green, Parafuchsin, Victoria Pure Blue BOH [manufactured by Hodogaya Chemical Co., Ltd.], Oil Blue # 603 [Orient Chemical Kogyo Co., Ltd.], Oil Pink # 312 [Orient Chemical Co., Ltd.], Oil Red 5B [Orient Chemical Co., Ltd.], Oil Scarlet # 308 [Orient Gaku Kogyo Co., Ltd.], Oil Red OG [Orient Chemical Co., Ltd.], Oil Red RR [Orient Chemical Co., Ltd.], Oil Green # 502 [Orient Chemical Co., Ltd.], Spiron Red BEH Special [made by Hodogaya Chemical Co., Ltd.], m-cresol purple, cresol red, rhodamine B, rhodamine 6G, sulforhodamine B, auramine, 4-p-diethylaminophenyliminonaphthoquinone, 2-carboxyanilino-4-p- Diethylaminophenyliminonaphthoquinone, 2-carboxystearylamino-4-pN, N-bis (hydroxyethyl) amino-phenyliminonaphthoquinone, 1-phenyl-3-methyl-4-p-diethylaminophenylimino-5-pyrazolone, 1-β-naphthyl-4- - dyes and p of diethylamino phenyl imino-5-pyrazolone, p ', p "- hexamethyl triamnotriphenylmethane (leuco crystal violet), and a leuco dye such as Pergascript Blue SRB (manufactured by Ciba-Geigy).

  In addition to the above, a leuco dye known as a material for thermal paper or pressure-sensitive paper is also suitable. Specific examples include crystal violet lactone, malachite green lactone, benzoylleucomethylene blue, 2- (N-phenyl-N-methylamino) -6- (Np-tolyl-N-ethyl) amino-fluorane, 2-anilino. -3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3,6-dimethoxyfluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) ) -Fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -6-methyl-7-anilinofluorane, 3 -(N, N-diethylamino) -6-methyl-7-xylidinofluorane, 3- (N, N-diethylamino) -6-methyl-7-chloro Fluorane, 3- (N, N-diethylamino) -6-methoxy-7-aminofluorane, 3- (N, N-diethylamino) -7- (4-chloroanilino) fluorane, 3- (N, N-diethylamino) -7-chlorofluorane, 3- (N, N-diethylamino) -7-benzylaminofluorane, 3- (N, N-diethylamino) -7,8-benzofluorane, 3- (N, N-dibutyl) Amino) -6-methyl-7-anilinofluorane, 3- (N, N-dibutylamino) -6-methyl-7-xylidinofluorane, 3-piperidino-6-methyl-7-anilinofluorane 3-pyrrolidino-6-methyl-7-anilinofluorane, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-n-butyl- -Methylindol-3-yl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl- 2-methylindol-3-yl) -4-zaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, and the like.

  A suitable addition amount of the dye that changes color by an acid or a radical is 0.01 to 10% by mass with respect to the solid content of the image recording layer.

<Polymerization inhibitor>
In order to prevent unnecessary thermal polymerization of the polymerizable compound (C) during the production or storage of the image recording layer, a small amount of a thermal polymerization inhibitor is preferably added to the image recording layer of the present invention.
Examples of the thermal polymerization inhibitor include hydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,4'-thiobis (3-methyl-6-t- (Butylphenol), 2,2-methylenebis (4-methyl-6-tert-butylphenol), and N-nitroso-N-phenylhydroxylamine aluminum salt are preferable.
The addition amount of the thermal polymerization inhibitor is preferably about 0.01 to about 5% by mass with respect to the total solid content of the image recording layer.

<Higher fatty acid derivatives, etc.>
In order to prevent polymerization inhibition by oxygen, a higher fatty acid derivative such as behenic acid or behenic acid amide is added to the image recording layer of the present invention, and the surface of the image recording layer is dried during the coating process. It may be unevenly distributed. The amount of the higher fatty acid derivative added is preferably about 0.1 to about 10% by mass with respect to the total solid content of the image recording layer.

<Plasticizer>
The image recording layer of the present invention may contain a plasticizer in order to improve the on-press developability.
Examples of the plasticizer include phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, dioctyl phthalate, octyl capryl phthalate, dicyclohexyl phthalate, ditridecyl phthalate, butyl benzyl phthalate, diisodecyl phthalate, diallyl phthalate; Glycol esters such as glycol phthalate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, triethylene glycol dicaprylate; Phosphate esters such as tricresyl phosphate and triphenyl phosphate Diisobutyl adipate, dioctyl adipate, dimethyl sebacate, dibutyl sebacate, dioct Ruazereto, aliphatic dibasic acid esters such as dibutyl maleate; polyglycidyl methacrylate, triethyl citrate, glycerin triacetyl ester, butyl laurate in.
The plasticizer content is preferably about 30% by mass or less based on the total solid content of the image recording layer.

<Inorganic fine particles>
The image recording layer according to the present invention may contain inorganic fine particles for the purpose of improving the strength of the cured film in the image area and improving the on-press developability of the non-image area.
As the inorganic fine particles, for example, silica, alumina, magnesium oxide, titanium oxide, magnesium carbonate, calcium alginate or a mixture thereof can be preferably mentioned. Even if they are not photothermally convertible, they can be used for strengthening the film, enhancing interfacial adhesion by surface roughening, and the like.
The inorganic fine particles preferably have an average particle size of 5 nm to 10 μm, and more preferably 0.5 μm to 3 μm. Within the above range, it is possible to form a non-image portion having excellent hydrophilicity that is stably dispersed in the image recording layer, sufficiently retains the film strength of the image recording layer, and hardly causes stains during printing.
The inorganic fine particles as described above can be easily obtained as a commercial product such as a colloidal silica dispersion.
The content of the inorganic fine particles is preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total solid content of the image recording layer.

<Low molecular hydrophilic compound>
The image recording layer according to the present invention may contain a hydrophilic low molecular weight compound for improving on-press developability. Examples of the hydrophilic low-molecular compound include water-soluble organic compounds such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and the like, and ether or ester derivatives thereof, glycerin, Polyhydroxys such as pentaerythritol, organic amines such as triethanolamine and diethanolamine monoethanolamine and salts thereof, organic sulfonic acids such as toluenesulfonic acid and benzenesulfonic acid and salts thereof, organic phosphonic acids such as phenylphosphonic acid and the like Examples thereof include organic carboxylic acids such as salts thereof, tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, and amino acids, and salts thereof.

<Other additives>
The image recording layer according to the present invention may contain a compound having at least one carboxylic acid (hereinafter, appropriately referred to as “carboxylic acid compound”) for the purpose of achieving or improving both sensitivity and on-press developability. it can. As such a carboxylic acid compound, a compound represented by the following general formula (4) can be suitably used.

In the general formula (4), X represents —O—, —S—, —SO ₂ —, —NH—, —N (R ³ ) —, —CH ₂ —, —CH (R ⁴ ) —, — C (R ⁴ ) (R ⁵ ) — is represented, and —O—, —S—, —NH—, and —N (R ³ ) — are particularly preferable from the viewpoint of sensitivity.
Here, R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group.

R ¹ and R ² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group. Examples of the monovalent nonmetallic atomic group include a hydroxyl group, a cyano group, a halogen atom, a nitro group, an amino group, an alkylamide group, an arylamide group, a thiol group, or a monovalent organic group. As an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 12 carbon atoms, an alkynyl group having 1 to 12 carbon atoms, an aromatic group, a heterocyclic group, an alkoxy group, an acyloxy group, an alkylcarbonyl group, an arylcarbonyl group. Group, alkoxycarbonyl group, and thioalkoxy group. These are alkyl group, alkenyl group, alkynyl group, aryl group, aromatic group, heterocyclic group, hydroxyl group, halogen atom, cyano group, alkoxy group, acyloxy group, alkylcarbonyl group, arylcarbonyl group, alkoxycarbonyl group, nitro It may have a substituent such as a group, amino group, alkylamide group, arylamide group, thiol group, thioalkoxy group, carboxy group, ester group or sulfo group.

R ¹ and R ² are preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 12 carbon atoms, an alkynyl group having 1 to 12 carbon atoms, an aromatic group, a heterocyclic group, a hydroxyl group, Examples include a cyano group, a halogen atom, an alkoxy group, an acyloxy group, a carbonyl group, an alkoxycarbonyl group, a nitro group, an amino group, an alkylamide group, an arylamide group, a thiol group, and a thioalkoxy group. Most preferred are alkyl groups of 1-6. R ¹ and R ² may be bonded to each other via a methylene group or a hetero atom to form a ring.

Preferred R ³ includes a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 1 to 12 carbon atoms, an alkynyl group having 1 to 12 carbon atoms, an aromatic group, and a heterocyclic group. Most preferred is an alkyl group having a substituent selected from an amide group, an alkoxy group, an alkoxycarbonyl group, and a carboxy group.
Preferable R ⁴ and R ⁵ are each independently the same as those mentioned in the description of R ¹ or R ² .

  A represents an aromatic group or a heterocyclic group, and an alkyl group, an alkenyl group, an alkynyl group, an aromatic group, a heterocyclic group, a hydroxyl group, a cyano group, a halogen atom, an alkoxy group, an acyloxy group, an alkylcarbonyl group, an arylcarbonyl group , An alkoxycarbonyl group, a nitro group, an amino group, an alkylamide group, an arylamide group, a thiol group, a thioalkoxy group, and the like.

By adding such a carboxylic acid compound, radical polymerization reaction by exposure is promoted, and printing durability is improved. Although its mechanism of action is not clear, decomposition of the infrared absorber or the polymerization initiator is promoted by such a carboxylic acid compound causing electron transfer with the infrared absorber or the polymerization initiator. This is probably because the polymerization is promoted. Moreover, it is thought that superposition | polymerization is accelerated | stimulated by acting also as a chain transfer agent in a polymerization reaction.
The content of the carboxylic acid compound is preferably 0.05 to 30% by mass and more preferably 0.1 to 10% by mass with respect to the total solid content of the image recording layer.

(Formation of image recording layer)
The image recording layer in the lithographic printing plate precursor according to the invention is coated by preparing a coating solution by dispersing or dissolving the necessary components in a solvent. Solvents used here include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxy Examples include ethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene, water and the like. However, the present invention is not limited to this. These solvents are used alone or in combination. The solid content concentration of the coating solution is preferably 1 to 50% by mass.
The image recording layer according to the present invention can be formed by preparing a plurality of coating solutions in which the same or different components are dispersed or dissolved in the same or different solvents, and repeating a plurality of coatings and dryings.

Further, the coating amount (solid content) of the image recording layer on the support obtained after coating and drying varies depending on the use, but generally 0.3 to 3.0 g / m ² is preferable. Within this range, good sensitivity and good film characteristics of the image recording layer can be obtained.
Various methods can be used as a coating method. Examples thereof include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.

(Support)
The support used for the lithographic printing plate precursor according to the invention is not particularly limited as long as it is a dimensionally stable plate. For example, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, cellulose propionate) Cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), and paper or plastic films on which the above-mentioned metals are laminated or deposited. Preferable supports include a polyester film and an aluminum plate. Among them, an aluminum plate that has good dimensional stability and is relatively inexpensive is preferable.

  The aluminum plate is a pure aluminum plate, an alloy plate containing aluminum as a main component and containing a trace amount of different elements, or a plastic laminated on a thin film of aluminum or an aluminum alloy. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is preferably 10% by mass or less. In the present invention, a pure aluminum plate is preferable, but completely pure aluminum is difficult to manufacture in terms of refining technology, and therefore may contain a slightly different element. The composition of the aluminum plate is not specified, and a publicly known material can be used as appropriate.

  The thickness of the support is preferably from 0.1 to 0.6 mm, more preferably from 0.15 to 0.4 mm, and even more preferably from 0.2 to 0.3 mm.

  Prior to using the aluminum plate, it is preferable to perform a surface treatment such as roughening treatment or anodizing treatment. By the surface treatment, it is easy to improve hydrophilicity and secure adhesion between the image recording layer and the support. Prior to roughening the aluminum plate, a degreasing treatment with a surfactant, an organic solvent, an alkaline aqueous solution or the like for removing rolling oil on the surface is performed as desired.

The surface roughening treatment of the aluminum plate is performed by various methods. For example, mechanical surface roughening treatment, electrochemical surface roughening treatment (electrochemical surface roughening treatment that dissolves the surface), chemical treatment, etc. Surface roughening treatment (roughening treatment that chemically selectively dissolves the surface).
As a method for the mechanical surface roughening treatment, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, or a buff polishing method can be used.
Examples of the electrochemical surface roughening treatment include a method in which an alternating current or a direct current is used in an electrolytic solution containing an acid such as hydrochloric acid or nitric acid. Another example is a method using a mixed acid as described in JP-A-54-63902.

  The surface-roughened aluminum plate is subjected to an alkali etching treatment using an aqueous solution of potassium hydroxide, sodium hydroxide or the like, if necessary, further neutralized, and if desired, wear resistant. In order to increase the anodic oxidation treatment.

As the electrolyte used for the anodizing treatment of the aluminum plate, various electrolytes that form a porous oxide film can be used. In general, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte.
The conditions for anodizing treatment vary depending on the electrolyte used and cannot be specified in general. In general, however, the electrolyte concentration is 1 to 80% by mass solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 to 60 A / dm ² , voltage 1 to 100 V, and electrolysis time 10 seconds to 5 minutes are preferable. The amount of the anodized film formed is preferably from 1.0 to 5.0 g / m ^2, and more preferably 1.5 to 4.0 g / m ^2. Within this range, good printing durability and good scratch resistance of the non-image area of the lithographic printing plate can be obtained.

  After the anodizing treatment, the surface of the aluminum plate is subjected to a hydrophilic treatment as necessary. The hydrophilization treatment is described in US Pat. Nos. 2,714,066, 3,181,461, 3,280,734, and 3,902,734. There are such alkali metal silicate methods. In this method, the support is immersed in an aqueous solution such as sodium silicate or electrolytically treated. In addition, the treatment with potassium zirconate fluoride described in JP-B 36-22063, U.S. Pat. Nos. 3,276,868, 4,153,461 and 4,689, And a method of treating with polyvinylphosphonic acid as described in each specification of No.272.

The support preferably has a center line average roughness of 0.10 to 1.2 μm. Within this range, good adhesion to the image recording layer, good printing durability and good stain resistance can be obtained.
The color density of the support is preferably 0.15 to 0.65 as the reflection density value. Within this range, good image formability by preventing halation during image exposure and good plate inspection after development can be obtained.

(Back coat layer)
After the surface treatment is performed on the support or after the undercoat layer is formed, a back coat can be provided on the back surface of the support, if necessary.
Examples of the back coat include hydrolysis and polycondensation of organic polymer compounds described in JP-A-5-45885, organometallic compounds or inorganic metal compounds described in JP-A-6-35174. A coating layer made of a metal oxide obtained in this manner is preferred. Among them, it is inexpensive to use a silicon alkoxy compound such as Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Si (OC ₃ H ₇ ) ₄ , Si (OC ₄ H ₉ ) _4. It is preferable in terms of easy availability.

(Undercoat layer)
In the lithographic printing plate precursor according to the invention, an undercoat layer can be provided between the image recording layer and the support, if necessary. Since the undercoat layer functions as a heat insulating layer, heat generated by exposure with an infrared laser does not diffuse to the support and can be used efficiently, so that there is an advantage that high sensitivity can be achieved. In addition, in the unexposed area, the image recording layer is easily peeled off from the support, so that the on-press developability is improved.
As the undercoat layer, specifically, a silane coupling agent having an ethylenic double bond reactive group capable of addition polymerization described in JP-A-10-282679, an ethylenic double bond reaction Preferable examples include a phosphorus compound having a group.
The coating amount (solid content) of the undercoat layer is preferably from 0.1-100 mg / m ^2, and more preferably 3 to 30 mg / m ^2.

(Protective layer)
In the lithographic printing plate precursor according to the present invention, a protective layer is provided on the image recording layer as necessary in order to prevent the occurrence of scratches in the image recording layer, to block oxygen, and to prevent ablation during high-illuminance laser exposure. Can do.
In the lithographic printing method of the present invention, exposure is usually carried out in the atmosphere, but the protective layer is a low-molecular substance such as oxygen or a basic substance present in the atmosphere that inhibits the image forming reaction caused by exposure in the image recording layer. It prevents the compound from being mixed into the image recording layer and prevents the inhibition of the image forming reaction due to exposure in the air. Therefore, the properties desired for the protective layer are low permeability of low-molecular compounds such as oxygen, furthermore, good transparency of light used for exposure, excellent adhesion to the image recording layer, and It is preferable that it can be easily removed in an on-press development process after exposure. Various studies have been made on protective layers having such characteristics, and are described in detail, for example, in US Pat. No. 3,458,311 and JP-A-55-49729.

Examples of the material used for the protective layer include water-soluble polymer compounds that are relatively excellent in crystallinity. Specific examples include water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, acidic celluloses, gelatin, gum arabic, and polyacrylic acid. Among these, when polyvinyl alcohol (PVA) is used as a main component, the best results are obtained for basic characteristics such as oxygen barrier properties and development removability. The polyvinyl alcohol may be partially substituted with an ester, ether or acetal as long as it contains an unsubstituted vinyl alcohol unit for providing the oxygen barrier property and water solubility necessary for the protective layer, and a part of the other You may have a copolymerization component. In particular, a mixture obtained by replacing polyvinyl pyrrolidone in the range of 1 to 50% by mass with respect to polyvinyl alcohol is preferable from the viewpoint of storage stability.
Specific examples of the polyvinyl alcohol include those having a hydrolysis degree of 71 to 100% and a degree of polymerization of 300 to 2400. Specifically, for example, Kuraray Co., Ltd. PVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST, PVA- HC, PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220, PVA-224, PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-405, PVA-420, PVA-613, and L-8 are mentioned.

The components of the protective layer (selection of PVA, use of additives, etc.), coating amount, etc. are appropriately selected in consideration of fogging properties, adhesion, scratch resistance, etc. in addition to oxygen barrier properties and development removability. In general, the higher the hydrolysis rate of PVA (that is, the higher the content of unsubstituted vinyl alcohol units in the protective layer), the higher the film thickness, the higher the oxygen barrier property, which is preferable in terms of sensitivity. . In order to prevent unnecessary polymerization reaction during production and storage, or unnecessary fogging during image exposure, image line weighting, and the like, it is preferable that the oxygen permeability is not excessively high. Accordingly, the oxygen permeability A at 25 ° C. and 1 atm is preferably 0.2 ≦ A ≦ 20 (ml / m ² · day).

As another composition of the protective layer, glycerin, dipropylene glycol and the like can be added in an amount corresponding to several mass% with respect to the (co) polymer to provide flexibility. Anionic surfactants such as sodium acid salts; amphoteric surfactants such as alkylaminocarboxylates and alkylaminodicarboxylates; nonionic surfactants such as polyoxyethylene alkylphenyl ethers to the (co) polymer Mass% can be added.
The thickness of the protective layer is suitably from 0.1 to 5 μm, particularly preferably from 0.2 to 2 μm.

  In addition, adhesion to the image area, scratch resistance, and the like are extremely important in handling the lithographic printing plate precursor. That is, when a protective layer that is hydrophilic because it contains a water-soluble polymer compound is laminated on an image recording layer that is oleophilic, the protective layer is easily peeled off due to insufficient adhesion, and polymerization is inhibited by oxygen at the peeled portion. It may cause defects such as poor film hardening due to.

On the other hand, various proposals have been made to improve the adhesion between the image recording layer and the protective layer. For example, JP-A-49-70702 and British Patent Application No. 1303578 disclose an acrylic emulsion, a water-insoluble vinylpyrrolidone-vinyl acetate copolymer, etc. in a hydrophilic polymer mainly composed of polyvinyl alcohol. It is described that sufficient adhesiveness can be obtained by mixing 20 to 60% by mass and laminating on an image recording layer. Any of these known techniques can be used in the present invention. The method for applying the protective layer is described in detail, for example, in US Pat. No. 3,458,311 and JP-A-55-49729.
Furthermore, other functions can be imparted to the protective layer. For example, by adding a colorant (for example, a water-soluble dye) that is excellent in the transparency of infrared rays used for exposure and that can efficiently absorb light of other wavelengths, it is safe light without causing a decrease in sensitivity. Suitability can be improved.

[Lithographic printing method]
Next, a planographic printing method using the planographic printing plate precursor of the present invention will be described. The lithographic printing method of the present invention comprises a step of exposing a lithographic printing plate precursor having an image recording layer as described above onto a support imagewise with an infrared laser, and any development on the lithographic printing plate precursor after exposure. A printing process for printing by supplying oil-based ink and an aqueous component without performing the treatment, and the infrared laser unexposed portion of the lithographic printing plate precursor is removed during the printing process. To do.
Hereinafter, this will be described in the order of steps.

(exposure)
In the planographic printing method of the present invention, the above-described planographic printing plate precursor of the present invention is first imagewise exposed with an infrared laser.
Although the infrared laser used for this invention is not specifically limited, The solid laser and semiconductor laser which radiate | emit infrared rays with a wavelength of 760-1200 nm are mentioned suitably. The output of the infrared laser is preferably 100 mW or more. In order to shorten the exposure time, it is preferable to use a multi-beam laser device.
The exposure time per pixel is preferably within 20 μsec. Moreover, it is preferable that irradiation energy amount is 10-300 mJ / cm < ² >.

(printing)
In the lithographic printing method of the present invention, as described above, after exposing the lithographic printing plate precursor of the present invention imagewise with an infrared laser, an oil-based ink and an aqueous component are supplied without any development processing steps. Print.
Specifically, after exposing the lithographic printing plate precursor with an infrared laser, mounting it on a printing machine without passing through the development process, printing the lithographic printing plate precursor on the printing machine, Examples include a method of printing with an infrared laser and printing without going through a development process.

After exposing the lithographic printing plate precursor imagewise with an infrared laser and supplying it with an aqueous component and oil-based ink without passing through a development process such as a wet development process, in the exposed part of the image recording layer, The image recording layer cured by exposure forms an oil-based ink receiving portion having an oleophilic surface. On the other hand, in the unexposed area, the uncured image recording layer is dissolved or dispersed and removed by the supplied aqueous component and / or oil-based ink, and the hydrophilic support surface is exposed in the area.
As a result, the aqueous component adheres to the exposed hydrophilic surface, and the oil-based ink is deposited on the image recording layer in the exposed area, and printing is started. Here, the water-based component or the oil-based ink may be supplied to the printing plate first, but the oil-based ink is first used to prevent the water-based component from being contaminated by the image recording layer in the unexposed area. It is preferable to supply. As the aqueous component and oil-based ink, a dampening water and printing ink for ordinary lithographic printing are used.
In this way, the lithographic printing plate precursor is subjected to on-press development on an offset printing machine and used as it is for printing a large number of sheets.

  The image forming layer of the lithographic printing plate precursor according to the present invention is excellent in curability of the exposed portion, and can be quickly cured by exposure with an infrared laser to form a strong ink receiving region. The lithographic printing of the present invention does not require special development processing because it is easily removed in a short time by contact with dampening water and / or ink inherently possessed by the image recording layer due to its high solubility and dispersibility. When applied to the method, it can be said that the effect is remarkable.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
1. Production of lithographic printing plate precursor (1) Production of support <aluminum plate>
Al: 99.5% by mass or more, Fe: 0.30% by mass, Si: 0.10% by mass, Ti: 0.02% by mass, Cu: 0.013% by mass, the balance being inevitable impurities JIS The molten A1050 aluminum alloy was cleaned and cast. As the cleaning treatment, degassing treatment was performed to remove unnecessary gas such as hydrogen in the molten metal, and ceramic tube filter treatment was further performed. The casting method was a DC casting method. The surface of the solidified ingot with a thickness of 500 mm was chamfered by 10 mm, and homogenized at 550 ° C. for 10 hours so that the intermetallic compound was not coarsened. Subsequently, it was hot-rolled at 400 ° C., subjected to intermediate annealing at 500 ° C. for 60 seconds in a continuous annealing furnace, and then cold-rolled to obtain an aluminum rolled plate having a thickness of 0.30 mm. By controlling the roughness of the rolling roll, to control the center line average roughness R _a after cold rolling to 0.2 [mu] m. Then, it applied to the tension leveler in order to improve planarity. The obtained aluminum plate was subjected to the following surface treatment.

First, in order to remove the rolling oil on the surface of the aluminum plate, a degreasing treatment is performed at 50 ° C. for 30 seconds using a 10 mass% sodium aluminate aqueous solution, and then, at 30 ° C. for 30 seconds using a 30 mass% nitric acid aqueous solution. Then, neutralization and smut removal treatment were performed.
Subsequently, a surface roughening treatment was performed in order to improve the adhesion between the image recording layer and the support and to provide water retention to the non-image area. Specifically, a current density of 20 A is passed through an aluminum plate web through an aqueous solution (liquid temperature 45 ° C.) containing 1% by mass of nitric acid and 0.5% by mass of aluminum nitrate supplied to the indirect power supply cell. Electrolytic surface roughening treatment was carried out by electrolyzing the aluminum plate with an alternating waveform of / dm ² and a duty ratio of 1: 1 so that the amount of electricity at the time of anode was 240 C / dm ² .
Further, an etching treatment was performed at 35 ° C. for 30 seconds using a 10 mass% sodium hydroxide aqueous solution, and then neutralization and smut removal treatment were performed at 50 ° C. for 30 seconds using a 30 mass% sulfuric acid aqueous solution.

Thereafter, an anodizing treatment was performed to improve wear resistance, chemical resistance and water retention. Specifically, electrolysis is performed by direct current having a current density of 14 A / dm ² while passing through a web of an aluminum plate through a 20% by mass sulfuric acid aqueous solution (liquid temperature: 35 ° C.) supplied to the indirect power feeding cell. An anodized film of 0.5 g / m ² was prepared.
Then, in order to ensure the hydrophilic property of a non-image part, the silicate process was performed for 15 second at 70 degreeC using the 1.5 mass% No. 3 sodium silicate aqueous solution. The adhesion amount of Si was 10 mg / m ² . Then, it washed with water and the support body was obtained. Center line average roughness R _a of the support obtained was 0.25 [mu] m.

(2) Formation of image recording layer (Examples 1 and 2 and Comparative Example 1)
An image recording layer coating solution 1 having the following composition is bar-coated on the above support, followed by oven drying at 70 ° C. for 60 seconds to form an image recording layer having a dry coating amount of 0.8 g / m ² and lithographic printing. I got the original version.

<Image recording layer coating solution 1>
・ Water 100g
・ The following microcapsule (1) 5 g (in terms of solid content)
-Polymerization initiator (compound described in Table 1) 0.5 g
-Fluorosurfactant (1) with the following structure 0.2g

(Synthesis of microcapsule (1))
As oil phase components, trimethylolpropane and xylene diisocyanate adduct (Mitsui Takeda Chemical Co., Ltd., Takenate D-110N) 10 g, pentaerythritol triacrylate (Nippon Kayaku Co., Ltd., SR444) 3.15 g, Infrared absorber (IR-1) 0.35 g having the following structure, 3- (N, N-diethylamino) -6-methyl-7-anilinofluorane (ODB manufactured by Yamamoto Kasei), and pionine A-41C (Takemoto) 0.1 g of Oils and Fats Co., Ltd. was dissolved in 17 g of ethyl acetate. As an aqueous phase component, 40 g of a 4% by mass aqueous solution of PVA-205 was prepared. The oil phase component and the aqueous phase component were mixed and emulsified for 10 minutes at 12000 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 40 ° C. for 3 hours. The microcapsule solution thus obtained was diluted with distilled water so that the solid content concentration became 20% by mass. The average particle diameter of the obtained microcapsules (1) was 0.3 μm.

(Examples 3 to 7, Comparative Example 2)
An image recording layer coating solution 2 having the following composition is bar-coated on the support and then oven-dried at 100 ° C. for 60 seconds to form an image recording layer having a dry coating amount of 1.0 g / m ^2. An original plate was obtained.

<Image recording layer coating solution 2>
Infrared absorber (compound described in Table 2 below) 0.05 g
-Polymerization initiator (compound described in Table 2 below) 0.2 g
・ Binder polymer (compound described in Table 2 below) 0.5 g
-Polymerizable compound (compound described in Table 2 below) 1.0 g
・ Victoria Pure Blue Naphthalenesulfonate 0.02g
・ 0.1 g of fluorosurfactant having the above structure (1)
・ Methyl ethyl ketone 18.0g

2. Exposure and Printing The obtained lithographic printing plate precursor was exposed with a Trend setter 3244VX manufactured by Creo equipped with a water-cooled 40 W infrared semiconductor laser under the conditions of an output of 9 W, an outer drum rotating speed of 210 rpm, and a resolution of 2400 dpi. The exposure image includes a thin line chart. The exposed exposed original plate was attached to a cylinder of a printing machine SOR-M manufactured by Heidelberg without developing. Dampening water (EU-3 (etch solution manufactured by Fuji Photo Film Co., Ltd.) / Water / isopropyl alcohol = 1/89/10 (volume ratio)) and TRANS-G (N) black ink (Dainippon Ink & Chemicals, Inc.) After supplying dampening water and ink, 100 sheets were printed at a printing speed of 6000 sheets per hour.
When the printing of the 100 sheets was completed, the number of printing sheets required until the ink was not transferred to the non-image area of the printing sheet was measured as on-machine developability. On-press development on the printing press was completed within 100 sheets, and a printed matter free from smudges in the non-image area was obtained.

3. Evaluation (1) Printing durability In the measurement of on-press developability, printing was continued after 100 sheets were printed. As the number of printed sheets was increased, the image recording layer was gradually worn out and the ink acceptability was lowered, so that the ink density in the printing paper was lowered. The number of printed sheets when the ink density (reflection density) was reduced by 0.1 from the start of printing was determined. The results are shown in Tables 1 and 2 below. The numerical values shown in Table 1 below are the same as those in Examples 1 and 2 when the number of printed sheets was set to 100 in Comparative Example 1 when the ink density (reflection density) was reduced by 0.1 from the start of printing. Similarly, the numerical values described in Table 2 below are relative values in Examples 3 to 7 when the number of printed sheets in Comparative Example 2 is 100.

(2) Stability over time After the obtained lithographic printing plate precursor is allowed to stand at 45 ° C. and 45% humidity for 40 hours, it is exposed and printed in the same manner as described above to develop on-press (printing paper on which on-press development has been completed). Number of sheets). When this result was compared with the on-press developability of the lithographic printing plate precursor before forced aging, the on-press developability of all the lithographic printing plate precursors after forced aging was observed. Tables 1 and 2 below show the difference in the number of printing papers that have undergone on-press development in each lithographic printing plate precursor. The smaller the number, the better, especially within 10 sheets.

  The polymerization initiators used in Examples 1 to 7 described in Tables 1 and 2 above are the specific polymerization initiators described in the main text, and the polymerization initiators used in Comparative Examples 1 and 2 (H -1) is the structure shown below.

  In addition, the structure of the infrared absorbers (IR-2) and (IR-3) described in Table 2 above, the structures of the binder polymers (BP-1) and (BP-2), and the polymerizable compound (M-1) ) And (M-2) are shown below.

<Polymerizable compound>
M-1: EO-modified triacrylate of isocyanuric acid (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester M-315)
M-2: Pentaerythritol tetraacrylate (SR-295 manufactured by Nippon Kayaku Co., Ltd.)

  As apparent from Table 1 and Table 2, according to the planographic printing method of the present invention using the planographic printing plate precursor containing (B) the specific polymerization initiator, the printing durability and the on-press developability with time. It was confirmed that an excellent lithographic printing plate was obtained. On the other hand, when a lithographic printing plate precursor of a comparative example that does not use a specific polymerization initiator (B) was made in the same process, the printing durability and on-press developability over time were inferior to those of the examples. I understood it.

Claims (6)

The support contains (A) an infrared absorber, (B) a polymerization initiator having a structure represented by the following general formula (1), and (C) a polymerizable compound, and is recorded by irradiation with infrared rays. An oil-based ink and an aqueous component are supplied to the lithographic printing plate precursor having an image recording layer, imagewise exposure with an infrared laser, and without any development treatment on the exposed lithographic printing plate precursor. And a printing process for printing, wherein an infrared laser unexposed portion of the planographic printing plate precursor is removed in the course of the printing process.

(In general formula (1), X represents a divalent linking group, and Y, Q, and Z each independently represent a monovalent substituent consisting of a hydrogen atom or a nonmetallic atom.) 2. The lithographic printing method according to claim 1, wherein the image recording layer contains microcapsules. The lithographic printing method according to claim 1, wherein the image recording layer contains (D) a binder polymer. On the support, it contains (A) an infrared absorber, (B) a polymerization initiator having a structure represented by the following general formula (1), and (C) a polymerizable compound, and a printing ink and / or A lithographic printing plate precursor having an image recording layer removable with a dampening solution.

(In General Formula (1), X represents a divalent linking group, and Y, Q, and Z each independently represent a monovalent substituent composed of a hydrogen atom or a nonmetallic atom. Represents a group.) The lithographic printing plate precursor as claimed in claim 4, wherein the image recording layer contains microcapsules. The lithographic printing plate precursor as claimed in claim 4 or 5, wherein the image recording layer contains (D) a binder polymer.