JP2012176606A - Lithographic printing original plate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithographic printing original plate which gives a lithographic printing plate having a favorable ink sticking property and high printing durability, and is excellent in on-machine developing property.SOLUTION: The lithographic printing original includes: an image recording layer containing a binder polymer having (A) an infrared absorbing dye, (B) a polymerization initiator, (C) a polymerizable compound and (D) an alkylene oxide group on a support which can form an image by removing an unexposed part by at least any of printing ink and dampening water on a printing machine after exposure; and a protection layer containing a hydrophilic polymer having (E) a repeating unit of two specific structures on the image recoding layer.

Description

  The present invention relates to a lithographic printing plate precursor and a plate making method thereof. More specifically, the present invention relates to a lithographic printing plate precursor that can be directly made by laser image exposure and can be developed on-press, and a plate-making method including on-press development.

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

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

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

For the above environmental problems, simplification and no processing of development or plate making are directed. As one simple plate making method, a method called “on-press development” is performed. That is, after the exposure of the lithographic printing plate precursor, conventional development is not performed, but it is mounted on a printing machine as it is, and unnecessary portions of the image recording layer are removed at the initial stage of a normal printing process.
In addition, as a simple development method, a method called “gum development” in which unnecessary portions of the image recording layer are removed with a finisher or gum solution having a pH close to neutral instead of a conventional highly alkaline developer is also performed. ing.

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

  As a lithographic printing plate precursor capable of on-machine development, for example, in Patent Documents 1 and 2, a lithographic printing plate having an image recording layer (thermosensitive layer) containing a microcapsule containing a polymerizable compound on a hydrophilic support. The original edition is listed. Patent Document 3 describes a lithographic printing plate precursor in which an image recording layer (photosensitive layer) containing an infrared absorber, a radical polymerization initiator, and a polymerizable compound is provided on a support.

Patent Documents 4 and 5 propose that the protective layer contains celluloses for imparting inking properties. However, the balance between the inking property / printing durability and the on-press development property was insufficient.
Furthermore, Patent Document 6 has an image recording layer containing an actinic ray absorber, a polymerization initiator, and a polymerizable compound on a support and removable by printing ink, fountain solution or both. Furthermore, a lithographic printing plate precursor having a protective layer (overcoat layer) containing an inorganic stratiform compound in this order is described.
However, since the polyvinyl alcohol resin and the inorganic layered compound having a hydrophilic surface are immersed in the image recording layer in the coating / drying stage, it is cured by exposure to form an image portion. There was a problem that the ink inking property was lowered.

JP 2001-277740 A JP 2001-277742 A JP 2002-287334 A Japanese Patent No. 4162365 JP 2008-162056 A JP 2005-119273 A

  Accordingly, an object of the present invention is to provide a lithographic printing plate precursor that overcomes the drawbacks of the prior art as described above. That is, it is to provide a lithographic printing plate precursor having good inking properties and high printing durability and having excellent on-press developability.

The present invention is as follows.
1. The support contains (A) an infrared-absorbing dye, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer having an alkylene oxide group. An image recording layer capable of forming an image by removing an unexposed portion with at least one of water, and a first (E) represented by the following general formula (1) or (2) on the image recording layer A lithographic printing plate precursor comprising a protective layer containing a repeating unit and a polymer having a second repeating unit represented by formula (3) or (6).

In the above formula, R ₁ and R ₄ each independently represents a hydrogen atom or a methyl group. R ₂ represents a hydrogen atom, and R ₃ represents an alkyl group. R ₅ and R ₆ each independently represents a hydrogen atom or an alkyl group, and Z represents a linear alkylene group. R ₇ and R ₉ each independently represents a hydrogen atom or a methyl group. Y is a carboxylic acid group, a carboxylic acid group, a sulfonic acid group, a sulfonic acid group, a phosphoric acid group, a phosphoric acid group, a phosphonic acid group, a phosphonic acid group, a hydroxyl group, a carboxybetaine group, a sulfobetaine group, an ammonium group, or The polyether group represented by the general formula (5) is represented. X represents a single bond, a divalent linking chain in the structure of the structure group (4), or a divalent linking chain obtained by combining a plurality of structures in the structure group (4). R ₁₀ and R ₁₁ both represent a hydrogen atom or both an alkyl group.
In General Formula (5), R ₈ represents a hydrogen atom or an alkyl group, L represents an alkylene group having 2 to 6 carbon atoms, and m is an integer of 2 to 120.

2. 2. The lithographic printing plate precursor as described in 1 above, wherein Y is a sulfonic acid group, a sulfonic acid group, a carboxybetaine group, a sulfobetaine group, or an ammonium group.
3. 3. The lithographic printing plate precursor as described in 1 or 2 above, wherein R ₁ and R ₄ are hydrogen atoms.
4). The lithographic printing plate precursor as described in any one of 1 to 3 above, wherein R ₇ and R ₉ are hydrogen atoms.
5. The lithographic printing plate precursor as described in any one of 1 to 4 above, wherein the image recording layer further comprises (F) a hydrophobized precursor.
6). The lithographic printing plate precursor as described in any one of 1 to 5 above, wherein the protective layer further contains an inorganic stratiform compound.
7). After the lithographic printing plate precursor according to any one of 1 to 6 is imagewise exposed, at least one of printing ink and fountain solution is supplied on a printing machine to remove a non-image portion of the image recording layer. A plate making method comprising removing the plate.

In the present invention, (D) a binder polymer having an alkylene oxide group is contained in the image recording layer, and (E) a hydrophilic polymer having a repeating unit having a specific structure is contained in the protective layer, so that on-press developability and The object of providing a lithographic printing plate precursor having good inking properties and high press life and capable of on-press development was achieved.
The working mechanism of the invention is not necessarily clear, but is estimated as follows.
Conventionally, when (D) a binder polymer having an alkylene oxide group is included in the image recording layer in order to impart on-press developability, when the protective layer is dried, the hydrophilic polymer and / or (F) inorganic layered layer of the protective layer is used. The compound was mixed with the image recording layer components and remained in the image area after development, resulting in a drawback that the inking property was lowered.
In the conventional hydrophilic binder polymer that ensures water solubility by including an acid group or a salt thereof in the molecule, the hydrophilicity of the image recording layer and the protective layer is increased. there were. In particular, in an on-press development type lithographic printing plate precursor containing an inorganic layered compound in a protective layer, it is more difficult to improve the inking property.
However, when the hydrophilic polymer (E) of the present invention obtained by copolymerizing the first repeating unit and the repeating unit having the second hydrophilic component in the structure is used for the protective layer, (D) is used for the image recording layer. Even if a binder polymer having an alkylene oxide group was present, the inking property was good.
This is because the (E) hydrophilic polymer of the present invention suppresses the mixing of the protective layer component and the image recording layer component even when there is an inorganic stratiform compound, so that the protective layer component is quickly removed during on-press development. It is estimated that this is the result.
Further, according to the present invention, an unexpected result was obtained that no deterioration of the inking property occurred at all when the special color ink which was likely to occur in the aged lithographic printing plate precursor was used.
As described above, the present invention is a novel polymer technology for a protective layer of an on-press development type lithographic printing plate precursor that cannot be imagined from an extension of the prior art, and enables a significant improvement in practical performance.

  According to the present invention, it is possible to provide a lithographic printing plate having good inking properties and high printing durability and having excellent on-press developability.

The present invention will be described in detail below.
[Lithographic printing plate precursor]
The lithographic printing plate precursor of the present invention comprises an image recording layer on which a non-exposed portion is removed on a support by at least one of printing ink and fountain solution on a printing machine, and a protective layer. They are provided in this order. Further, the lithographic printing plate precursor according to the invention may have an undercoat layer between the support and the image recording layer.
The components and components of the lithographic printing plate precursor according to the invention will be described below.

(Protective layer)
The protective layer of the present invention comprises (E) a first repeating unit represented by the following general formula (1) or (2), and a second repeating unit represented by the general formula (3) or (6). A polymer (hereinafter abbreviated as (E) a hydrophilic polymer).

In the above formula, R ₁ and R ₄ each independently represents a hydrogen atom or a methyl group. From the viewpoint of on-press development property, a hydrogen atom is preferable. R ₂ represents a hydrogen atom, and R ₃ represents an alkyl group. As the alkyl group, an alkyl group having 4 or less carbon atoms is preferable, and a branched alkyl group having 4 or less carbon atoms is more preferable from the viewpoint of achieving both on-press developability and inking property. The alkyl group may have a substituent, and specific examples of the substituent include an amino group, a hydroxyl group, a carboxylic acid group, and an alkoxy group.
R ₅ and R ₆ each independently represents a hydrogen atom or an alkyl group. An alkyl group having 4 or less carbon atoms is preferable from the viewpoint of achieving both on-press developability and inking property. Z represents a linear alkylene group. The alkylene group is more preferably a linear alkylene having 2 to 4 carbon atoms.

R ₇ and R ₉ each independently represents a hydrogen atom or a methyl group. From the viewpoint of on-press developability, R ₇ and R ₉ are preferably hydrogen atoms. Y is a carboxylic acid group, a carboxylic acid group, a sulfonic acid group, a sulfonic acid group, a phosphoric acid group, a phosphoric acid group, a phosphonic acid group, a phosphonic acid group, a hydroxyl group, a carboxybetaine group, a sulfobetaine group, an ammonium group, or The polyether group represented by the general formula (5) is represented. From the viewpoint of on-press developability, Y is preferably a sulfonic acid group, a sulfonic acid group, a carboxybetaine group, a sulfobetaine group, or an ammonium group, and more preferably a sulfonic acid group, a sulfonic acid group, or a sulfobetaine group. The carboxybetaine group is a group having both a quaternary ammonium group and a carboxyl group, and the sulfobetaine group is a group having both a quaternary ammonium group and a sulfonic acid group. Preferable salts include inorganic salts such as potassium salt and sodium salt, and ammonium salts such as pyridinium and tetrabutylammonium.
X represents a single bond, a divalent linking chain in the structure of the structure group (4), or a divalent linking chain obtained by combining a plurality of structures in the structure group (4). Preferably, X represents a single bond or a divalent linking chain obtained by combining a plurality of structures of the following structural group (7).

R ₁₀ and R ₁₁ both represent a hydrogen atom or both an alkyl group. R ₁₀ and R ₁₁ are preferably an alkyl group having 4 or less carbon atoms from the viewpoint of achieving both on-press developability and inking property.
R ₈ represents a hydrogen atom or an alkyl group, L represents an alkylene group having 2 to 6 carbon atoms, and m is an integer of 2 to 120. R ₈ is preferably a hydrogen atom or an alkyl group having 4 or less carbon atoms, L is preferably an alkylene group having 2 to 4 carbon atoms, m is preferably an integer of 2 to 90, and more preferably an integer of 2 to 25.

  The hydrophilic polymer (E) of the present invention contains at least one kind of the first repeating unit and the second repeating unit. Moreover, the preferable combination of a 1st repeating unit and a 2nd repeating unit is a combination of said preferable 1st repeating unit and a preferable 2nd repeating unit.

The hydrophilic polymer (E) of the present invention preferably contains 70 to 95 mol% of the first repeating unit and 5 to 30 mol% of the second repeating unit, 70 to 80 mol% of the first repeating unit, and second More preferred are those containing 20 to 30 mol% of the repeating unit, and most preferred are those containing 75 to 80 mol% of the first repeating unit and 20 to 25 mol% of the second repeating unit.
Moreover, the (E) hydrophilic polymer of this invention may have a repeating unit derived from the monomer which has an ethylenically unsaturated bond other than the above as a 3rd repeating unit.

  The hydrophilic polymer (E) of the present invention is obtained by copolymerizing a monomer serving as a first repeating unit, a monomer serving as a second repeating unit, and, if necessary, a monomer serving as a third repeating unit by a known method. It is obtained by doing.

  The (E) hydrophilic polymer of the present invention has a mass average molar mass (Mw) of preferably 10,000 to 200,000, more preferably 10,000 to 100,000, and most preferably 10,000 to 30,000. .

  Tables 1 to 4 below show specific examples of the (E) hydrophilic polymer. The number in a table | surface represents the compound number of a hydrophilic polymer, and respond | corresponds with the compound number in an Example.

  (E) The content of the hydrophilic polymer in the protective layer is preferably 40% by mass or more of the solid content of the protective layer. More preferably, it is 60 mass% or more, Most preferably, it is 80 mass% or more. Within this range, a lithographic printing plate having good inking properties and high printing durability can be obtained, and a lithographic printing plate precursor having excellent on-press developability can be obtained.

The protective layer of the present invention preferably contains an inorganic stratiform compound in order to obtain a good oxygen barrier property with a thin layer.
The inorganic layered compound is a particle having a thin flat plate shape. For example, the following general formula A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O) ₂ [where A is Li, Any of K, Na, Ca, Mg, an organic cation, B and C are any of Fe (II), Fe (III), Mn, Al, Mg, V, and D is Si or Al. And mica groups such as natural mica and synthetic mica, talc, teniolite, montmorillonite, saponite, hectorite, zirconium phosphate and the like represented by the formula 3MgO.4SiO.H ₂ O.

Examples of the natural mica include muscovite, soda mica, phlogopite, biotite and sericite. Further, as the synthetic mica, non-swelling mica such as fluorine phlogopite mica ₃ (AlSi ₃ O ₁₀ ) F ₂ , potassium tetrasilicon mica KMg _2.5 Si ₄ O ₁₀ ) F ₂ , and Na tetrasilicic mica NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ , Na or Li Tenniolite (Na, Li) Mg ₂ Li (Si ₄ O ₁₀ ) F ₂ , Montmorillonite Na or Li Hectorite (Na, Li) _1/8 Mg Swellable mica such as _2/5 Li _1/8 (Si ₄ O ₁₀ ) F ₂ can be used. Synthetic smectite is also useful.

Among the above layered compounds, mica is preferable, and fluorine-based swellable mica that is a synthetic inorganic layered compound is particularly useful. That is, this swellable synthetic mica and swellable clay minerals such as montmorillonite, saponite, hectorite, bentonite and the like have a laminated structure composed of unit crystal lattice layers with a thickness of about 10 to 15 mm, Atomic substitution is significantly greater than other clay minerals. As a result, the lattice layer is deficient in positive charge, and in order to compensate for this, cations such as Li ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ and organic cations are adsorbed between the layers. These inorganic layered compounds swell with water. If shear is applied in this state, it will easily cleave and form a stable sol in water. Bentonite and swelling synthetic mica have this tendency.

  As the shape of the layered compound, from the viewpoint of diffusion control, the thinner the better, the better the planar size as long as the smoothness of the coated surface and the transmittance of actinic rays are not impaired. Accordingly, the aspect ratio is preferably 20 or more, more preferably 100 or more, and particularly preferably 200 or more. The aspect ratio is the ratio of the thickness to the major axis of the particle, and can be measured, for example, from a projected view of the particle by a micrograph. The larger the aspect ratio, the greater the effect that can be obtained.

  The average particle diameter of the layered compound is preferably 1 to 20 μm, more preferably 1 to 10 μm, and particularly preferably 2 to 5 μm. If the particle diameter is 1 μm or more, the permeation of oxygen and moisture is sufficiently suppressed, and the effect can be sufficiently exhibited, which is preferable. Moreover, if it is 20 micrometers or less, the dispersion stability in a coating liquid is enough, and stable application | coating can be performed and it is preferable. The average thickness of the particles is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.01 μm or less. For example, among the inorganic layered compounds, the size of the swellable synthetic mica that is a representative compound is preferably 1 to 50 nm in thickness and about 1 to 20 μm in surface size.

  When the inorganic layered compound particles having such a large aspect ratio are contained in the protective layer, the coating film strength is improved, and the permeation of oxygen and moisture can be effectively prevented. Deterioration is prevented, and even when stored for a long time under high-humidity conditions, an effect of excellent storage stability can be obtained without deterioration of image-forming properties in a lithographic printing plate precursor due to changes in humidity.

  Further, a fluorine compound, a silicone compound, and a wax emulsion can be added to these protective layers in order to prevent stickiness. When these are added, the stickiness caused by the hydrophilic resin is eliminated by floating on the surface of the protective layer. The amount of these compounds added is preferably from 0.1% by mass to 5% by mass of the protective layer, more preferably from 0.5 to 2.0% by mass.

  Protective layer coating solutions include known anionic surfactants, nonionic surfactants, cationic surfactants, fluorosurfactants for improving coatability, and water-soluble plasticizers for improving physical properties of coatings. Additives can be added. Examples of the water-soluble plasticizer include propionamide, cyclohexanediol, glycerin, sorbitol and the like. Furthermore, a known additive for improving the adhesion to the image recording layer, the temporal stability of the coating solution, and the inking property may be added to the coating solution.

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

(Image recording layer)
The image recording layer of the present invention contains (A) an infrared absorbing dye, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer having an alkylene oxide group, and is printed on a printing machine after exposure. It is an image recording layer capable of forming an image by removing an unexposed portion with at least one of ink and fountain solution. The on-press developable image recording layer of the present invention preferably further contains (G) a hydrophobized precursor.
Below, each component which can be contained in an image recording layer is demonstrated one by one.

(D) Binder polymer having alkylene oxide group The binder polymer having an alkylene oxide group used in the lithographic printing plate precursor according to the invention has a poly (alkylene oxide) moiety in the main chain, but has a side chain. Even in a graft polymer having poly (alkylene oxide) in the side chain, a block composed of a poly (alkylene oxide) -containing repeating unit and a block composed of a (alkylene oxide) -free repeating unit Copolymers may be used.
When it has in a principal chain, a polyurethane resin is preferable. The main chain polymer in the case of the side chain includes acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, methacrylic resin, polystyrene resin, novolac type phenol resin, polyester resin Synthetic rubber and natural rubber can be mentioned, and acrylic resin is particularly preferable.

As said alkylene oxide, a C2-C6 alkylene oxide is preferable and especially an ethylene oxide or a propylene oxide is preferable.
The number of repeating alkylene oxides at the poly (alkylene oxide) site is preferably 2 to 120, more preferably 2 to 70, and still more preferably 2 to 50.
If the number of alkylene oxide repeats is 120 or less, both the printing durability due to wear and the printing durability due to ink acceptance are further improved, which is preferable.

  The poly (alkylene oxide) moiety is preferably contained as a side chain of the binder polymer in a structure represented by the following general formula (8). More preferably, it is contained as a side chain of the acrylic resin in a structure represented by the following general formula (8).

In general formula (8), y represents 2-120, the range of 2-70 is preferable and the range of 2-50 is more preferable. R ₁ represents a hydrogen atom or an alkyl group, and R ₂ represents a hydrogen atom or an organic group. As the organic machine, an alkyl group having 1 to 6 carbon atoms is preferable, and a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, isobutyl group, t-butyl group, n -Pentyl group, isopentyl group, neopentyl group, n-hexyl group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, cyclopentyl group, and cyclohexyl group.
Among the above, R ₁ is preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom. R ₂ is most preferably a hydrogen atom or a methyl group.

The binder polymer may have crosslinkability in order to improve the film strength of the image area. In order to impart crosslinkability to the 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, wherein 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, or 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.

  The binder polymer having crosslinkability, for example, has a free radical (polymerization initiation radical or a growth radical in the polymerization process of the polymerizable compound) added to the crosslinkable functional group, and the polymerization chain of the polymerizable compound is formed directly between the 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 together, thereby causing cross-linking between polymer molecules. Forms and cures.

  The content of the crosslinkable group in the binder polymer (content of unsaturated double bond capable of radical polymerization by iodometric titration) is preferably 0.1 to 10.0 mmol, more preferably 1. 0 to 7.0 mmol, most preferably 2.0 to 5.5 mmol. Within this range, good sensitivity and good storage stability can be obtained.

  Specific examples (1) to (11) of the binder polymer used in the present invention are shown below, but the present invention is not limited thereto.

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

  In the present invention, if necessary, hydrophilic polymer compounds such as polyacrylic acid and polyvinyl alcohol described in JP-A-2008-195018 can be used in combination. Further, a lipophilic polymer compound and a hydrophilic polymer compound can be used in combination.

  The form of the binder polymer of the present invention may be present in the image recording layer as a binder that serves as a linking function for each material, or may be present in the form of fine particles. When present in the form of fine particles, the average particle size is in the range of 10 to 1000 nm, preferably in the range of 20 to 300 nm, and particularly preferably in the range of 30 to 120 nm.

  The content of the binder polymer of the present invention is preferably 5 to 90% by mass, more preferably 5 to 80% by mass, and still more preferably 10 to 70% by mass with respect to the total solid content of the image recording layer.

(A) Infrared-absorbing dye The infrared-absorbing dye has a function of converting absorbed infrared light into heat and a function of being excited by infrared light to transfer electrons and / or energy to a polymerization initiator described later. The infrared absorbing dye used in the present invention is a dye having an absorption maximum at a wavelength of 760 to 1200 nm.

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

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

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

Ar ¹ and Ar ² may be the same or different and each represents an aryl group which may have a substituent. Preferred aryl groups include a benzene ring and a naphthalene ring. Moreover, as a preferable substituent, a C12 or less hydrocarbon group, a halogen atom, and a C12 or less alkoxy group are mentioned. Y ¹ and Y ² may be the same or different and each represents a sulfur atom or a dialkylmethylene group having 12 or less carbon atoms. R ³ and R ⁴ may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferred substituents include alkoxy groups having 12 or less carbon atoms, carboxylic acid groups, and sulfonic acid 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 halide ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ion, particularly preferably a perchlorate ion, in view of the storage stability of the image recording layer coating solution. , Hexafluorophosphate ions, and aryl sulfonate ions.

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

  Moreover, only 1 type may be used for these (A) infrared absorption dyes, and 2 or more types may be used together, and infrared absorbers other than infrared absorption dyes, such as a pigment, may be used together. As the pigment, compounds described in JP 2008-195018 A [0072] to [0076] are preferable.

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

(B) Polymerization initiator As (B) polymerization initiator used for this invention, the compound which starts and accelerates | stimulates the polymerization of (C) polymeric compound is shown. As the polymerization initiator that can be used in the present invention, a radical polymerization initiator is preferable, and a known thermal polymerization initiator, a compound having a bond with a small bond dissociation energy, a photopolymerization initiator, and the like can be used.
Examples of the polymerization initiator in the present invention include (a) an organic halide, (b) a carbonyl compound, (c) an azo compound, (d) an organic peroxide, (e) a metallocene compound, (f) an azide compound, (G) hexaarylbiimidazole compound, (h) organic borate compound, (i) disulfone compound, (j) oxime ester compound, (k) onium salt compound.

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

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

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

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

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

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

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

(I) Examples of the disulfone compound include compounds described in JP-A Nos. 61-166544 and 2002-328465.

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

(K) Examples of the onium salt compounds include S.I. I. Schlesinger, Photogr. Sci. Eng. 18, 387 (1974), T .; S. Bal et al, Polymer, 21, 423 (1980), diazonium salts described in JP-A-5-158230, ammonium described in US Pat. No. 4,069,055, JP-A-4-365049, and the like. Salt, phosphonium salts described in U.S. Pat. Nos. 4,069,055 and 4,069,056, EP 104,143, U.S. Patent Application Publication No. 2008/0311520 JP-A-2-150848, JP-A-2008-195018, or J.P. V. Crivello et al, Macromolecules, 10 (6), 1307 (1977), iodonium salts, European Patent Nos. 370,693, 233,567, 297,443, 297,442, US Patent 4,933,377, 4,760,013, 4,734,444, 2,833,827, German Patents 2,904,626, 3,604,580, Sulfonium salts described in each specification of JP-A-3,604,581; V. Crivello et al, J.A. Polymer Sci. , Polymer Chem. Ed. , 17, 1047 (1979), a selenonium salt described in C.I. S. Wen et al, Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988), and onium salts such as azinium salts described in JP-A-2008-195018.

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

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

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

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

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

(C) Polymerizable compound The radical polymerizable compound used in the image recording layer in the invention is an addition polymerizable compound having at least one ethylenically unsaturated double bond, and has at least one terminal ethylenically unsaturated bond, Preferably, it is selected from compounds having two or more. These have chemical forms such as monomers, prepolymers, ie dimers, trimers and oligomers, or mixtures thereof.

  Examples of monomers include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), esters and amides thereof, preferably unsaturated carboxylic acids. An ester of an acid and a polyhydric alcohol compound and an amide of an unsaturated carboxylic acid and a polyvalent amine compound are used. In addition, an addition reaction product of an unsaturated carboxylic acid ester or amide having a nucleophilic substituent such as a hydroxyl group, amino group or mercapto group with a monofunctional or polyfunctional isocyanate or epoxy, and a monofunctional or polyfunctional compound. A dehydration condensation reaction product with a functional carboxylic acid is also preferably used. Further, an addition reaction product of an unsaturated carboxylic acid ester or amide having an electrophilic substituent such as an epoxy group or an epoxy group with a monofunctional or polyfunctional alcohol, amine or thiol, a halogen group or In addition, a substitution reaction product of an unsaturated carboxylic acid ester or amide having a leaving substituent such as a tosyloxy group and a monofunctional or polyfunctional alcohol, amine or thiol is also suitable. As another example, it is also possible to use a group of compounds substituted with unsaturated phosphonic acid, styrene, vinyl ether or the like instead of the unsaturated carboxylic acid. These are disclosed in JP-T-2006-508380, JP-A-2002-287344, JP-A-2008-256850, JP-A-2001-342222, JP-A-9-179296, JP-A-9-179297. JP-A-9-179298, JP-A-2004-294935, JP-A-2006-243493, JP-A-2002-275129, JP-A-2003-64130, JP-A-2003-280187, It is described in references including Kaihei 10-333321.

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

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

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

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

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

(F) Hydrophobized precursor In the present invention, a hydrophobized precursor can be used to improve on-press developability. The hydrophobized precursor in the present invention means fine particles capable of converting the image recording layer to hydrophobic when heat is applied. The fine particles are at least one selected from hydrophobic thermoplastic polymer fine particles, thermally reactive polymer fine particles, polymer fine particles having a polymerizable group, microcapsules enclosing a hydrophobic compound, and microgel (crosslinked polymer fine particles). It is preferable. Among these, polymer fine particles and microgels having a polymerizable group are preferable.

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

  The average particle diameter of the hydrophobic thermoplastic polymer fine particles used in the present invention is preferably 0.01 to 2.0 μm.

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

  The thermoreactive group in the polymer fine particles having a thermoreactive group used in the present invention may be any functional group that performs any reaction as long as a chemical bond is formed, but is preferably a polymerizable group, Examples include ethylenically unsaturated groups that undergo radical polymerization reactions (eg, acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, etc.), cationic polymerizable groups (eg, vinyl groups, vinyloxy groups, epoxy groups, oxetanyl groups, etc.) ), Isocyanato groups that perform addition reactions, or their block bodies, epoxy groups, vinyloxy groups, and functional groups having active hydrogen atoms that are reaction partners (for example, amino groups, hydroxyl groups, carboxylic acid groups, etc.), condensation reactions Carboxylic acid group to be performed and hydroxyl or amino group as reaction partner, acid anhydride and reaction to perform ring-opening addition reaction An amino group or a hydroxyl group with whom may be mentioned as suitable.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Specific examples of the ammonium group-containing polymer are shown below.
(1) 2- (Trimethylammonio) ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90 Mw 45,000)
(2) 2- (Trimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 Mw 60,000)
(3) 2- (Ethyldimethylammonio) ethyl methacrylate = p-toluenesulfonate / hexyl methacrylate copolymer (molar ratio 30/70 Mw 45,000)
(4) 2- (Trimethylammonio) ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20/80 Mw 60,000)
(5) 2- (Trimethylammonio) ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (molar ratio 40/60 Mw 7 million)
(6) 2- (Butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 25/75 Mw 650,000)
(7) 2- (Butyldimethylammonio) ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 Mw 65,000)
(8) 2- (butyldimethylammonio) ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 Mw 75,000)
(9) 2- (butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate / 2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer (molar ratio 15/80/5 (Mw 650,000)

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

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

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

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

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

In the case of a high molecular polymer, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferable. The adsorbable adsorptive group to the support surface, a phenolic hydroxyl group, a carboxylic acid _{group, -PO 3 H 2, -OPO 3} H 2, -CONHSO 2 -, - SO 2 NHSO 2 -, - COCH 2 COCH ₃ is preferred. As the hydrophilic group, a sulfonic acid group is preferable. The crosslinkable group is preferably a methacryl group or an allyl group.
This polymer may have a crosslinkable group introduced by salt formation between the polar substituent of the polymer, a substituent having a counter charge and a compound having an ethylenically unsaturated bond, Other monomers, preferably hydrophilic monomers, may be further copolymerized.

Specifically, a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679 and an ethylenic compound described in JP-A-2-304441. The phosphorus compound which has a heavy bond reactive group is mentioned suitably. Crosslinkable group (preferably ethylenically unsaturated bond group) described in JP-A-2005-238816, JP-A-2005-12549, JP-A-2006-239867, JP-A-2006-215263, surface of support Those containing a low-molecular or high-molecular compound having a functional group that interacts with each other and a hydrophilic group are also preferably used.
More preferable are polymer polymers having an adsorbable group, a hydrophilic group, and a crosslinkable group that can be adsorbed on the support surface described in JP-A Nos. 2005-125749 and 2006-188038.

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

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

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

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

  If necessary, the support of the present invention includes an organic polymer compound described in JP-A-5-45885 and a silicon alkoxy compound described in JP-A-6-35174 on the back surface. A backcoat layer can be provided.

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

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

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

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

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

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these. In the polymer compound, the molecular weight is a mass average molar mass (Mw), and the ratio of repeating units is a mole percentage, except for those specifically defined.

[Examples 1-226 and Comparative Examples 1-3]

[I] Preparation of planographic printing plate precursor

(1) Preparation of support In order to remove rolling oil on the surface of an aluminum plate (material JIS A 1050) having a thickness of 0.3 mm, degreasing treatment was performed at 50 ° C. for 30 seconds using a 10 mass% sodium aluminate aqueous solution. After that, the aluminum surface was grained using ^three bundle-planted nylon brushes having a bristle diameter of 0.3 mm and a pumice-water suspension (specific gravity 1.1 g / cm ³ ) having a median diameter of 25 μm and washed thoroughly with water. . This plate was etched by being immersed in a 25 mass% aqueous sodium hydroxide solution at 45 ° C for 9 seconds, washed with water, further immersed in a 20 mass% nitric acid aqueous solution at 60 ° C for 20 seconds, and washed with water. The etching amount of the grained surface at this time was about 3 g / m ² .

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

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

(2) Formation of undercoat layer Next, the following undercoat layer coating solution (1) is applied onto the support (2) so that the dry coating amount is 20 mg / m ² , and a support having an undercoat layer. Was made.

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

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

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

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

  The binder polymer (2), infrared absorbing dye (1), polymerization initiator (1), phosphonium compound (1), low molecular weight hydrophilic compound (1), ammonium group-containing polymer, and fluorine-based surfactant ( The structure of 1) is as shown below.

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

(4) Formation of Protective Layer After the bar coating of the protective layer coating liquid (1) having the following composition was applied on the image recording layer, it was oven-dried at 120 ° C. for 60 seconds, and the dry coating amount was 0.15 g / m. ² protective layers were formed to obtain lithographic printing plate precursors for Examples 1-210 and 212-226, and Comparative Examples 1-3.
Further, an inorganic layered compound was used in the protective layer in the same manner as in the lithographic printing plate precursor for Example 49 except that the protective layer coating liquid (2) having the following composition was used instead of the protective layer coating liquid (1). Thus, a lithographic printing plate precursor for Example 211 containing no was obtained.

<Coating liquid for protective layer (1)>
・ Inorganic layered compound dispersion (1) 1.5 g
-(E) hydrophilic polymer (described in Tables 5 to 10) 0.035 g as a solid content
・ Nippon Emulsion Co., Ltd. surfactant polyoxyethylene lauryl ether (Emalex 710) 1% by weight aqueous solution 0.86 g
・ Ion-exchanged water 6.54g

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

<Coating liquid for protective layer (2)>
-Hydrophilic polymer (Compound No. 49) 0.035 g as solid content
・ Nippon Emulsion Co., Ltd. surfactant polyoxyethylene lauryl ether (Emalex 710) 1% by weight aqueous solution 0.86 g
・ Ion exchange water 8.00 g

[II] Evaluation of lithographic printing plate precursors Using the obtained lithographic printing plate precursors, on-machine developability, inking properties (initial inking properties, inking properties with special inks) and printing durability are as follows. It was evaluated with. About the charring property with the special color ink, the case where the lithographic printing plate precursor was aged was also evaluated.

(1) On-machine developability The obtained lithographic printing plate precursor was subjected to the conditions of an external drum rotation speed of 1000 rpm, a laser output of 70%, and a resolution of 2400 dpi on a Fujifilm Corp. Luxel PLANETTER T-6000III equipped with an infrared semiconductor laser. Exposed. The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The obtained exposed original plate was attached to a plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Equality-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) dampening water and Values-G (N) black ink (manufactured by Dainippon Ink & Chemicals, Inc.) After dampening water and ink were supplied by the standard automatic printing start method of LITHRONE 26 and developed on the machine, 100 sheets were printed on Tokuhishi Art (76.5 kg) paper at a printing speed of 10,000 sheets per hour.
The number of print sheets required until the on-press development on the printing press of the unexposed portion of the image recording layer was completed and the ink was not transferred to the non-image portion was measured as on-press developability. The results are shown in Tables 5-10.

(2) Inking property i) Initial inking property In the above printing start, the initial inking property is the number of printing papers required until the ink density on the printing paper in the exposed area of the image recording layer reaches the standard density. Measured. The results are shown in Tables 5-10.

ii) Spot color ink fillability (immediately after application, after time)
The obtained exposed original plate was attached to a plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Wet with the standard automatic printing start method of LITHRONE26 using dampening water of Ecology-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (capacity ratio) and Apple Pantone Blau 072C (ink made by Apple). After supplying water and ink and developing on the machine, printing was performed on Tokishi Art (76.5 kg) paper at a printing speed of 10,000 sheets per hour. The 10,000th printing paper was sampled, and the ink density at the 20% FM halftone dot portion was examined with a Gretag densitometer. Based on the measured value, evaluation of ink inking property is shown in Tables 5 to 10 with the following indices.

A. Ink density 1.8 to 1.9: No ink density decrease, and good ink setting.
B. Ink density 1.5 to 1.7: Slightly lower ink density but acceptable level.
C. Ink density 1.0 to 1.4: The ink density is clearly lowered and NG level.
D. Ink density of 0.9 or less: The ink density is significantly lowered.

  The inking property after the lapse of time is a result of performing the above evaluation after storing the prepared lithographic printing plate precursor at 60 ° C. for 4 days.

(3) Printing durability After the above-described evaluation of on-press developability immediately after coating, printing was further continued. As the number of printed sheets was increased, the image recording layer was gradually worn out, so that the ink density on the printed material decreased. Printing durability was evaluated using the number of printed copies when the value measured by the Gretag densitometer for the 50% halftone dot area ratio of the FM screen in the printed material was 5% lower than the measured value for the 100th printed sheet. . The results are shown in Tables 5-10.

  The structures of the hydrophilic polymers R-1 to R-3 used in the comparative examples are as follows. Both Mw were 20,000.

Claims (7)

The support contains (A) an infrared-absorbing dye, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer having an alkylene oxide group. An image recording layer capable of forming an image by removing an unexposed portion with at least one of water, and a first (E) represented by the following general formula (1) or (2) on the image recording layer A lithographic printing plate precursor comprising a protective layer containing a repeating unit and a polymer having a second repeating unit represented by formula (3) or (6).

In the above formula, R ₁ and R ₄ each independently represents a hydrogen atom or a methyl group. R ₂ represents a hydrogen atom, and R ₃ represents an alkyl group. R ₅ and R ₆ each independently represents a hydrogen atom or an alkyl group, and Z represents a linear alkylene group. R ₇ and R ₉ each independently represents a hydrogen atom or a methyl group. Y is a carboxylic acid group, a carboxylic acid group, a sulfonic acid group, a sulfonic acid group, a phosphoric acid group, a phosphoric acid group, a phosphonic acid group, a phosphonic acid group, a hydroxyl group, a carboxybetaine group, a sulfobetaine group, an ammonium group, or The polyether group represented by the general formula (5) is represented. X represents a single bond, a divalent linking chain in the structure of the structure group (4), or a divalent linking chain obtained by combining a plurality of structures in the structure group (4). R ₁₀ and R ₁₁ both represent a hydrogen atom or both an alkyl group.
In General Formula (5), R ₈ represents a hydrogen atom or an alkyl group, L represents an alkylene group having 2 to 6 carbon atoms, and m is an integer of 2 to 120.   The lithographic printing plate precursor as claimed in claim 1, wherein Y is a sulfonic acid group, a sulfonic acid group, a carboxybetaine group, a sulfobetaine group, or an ammonium group. The lithographic printing plate precursor as claimed in claim 1 or 2, wherein R ₁ and R ₄ are hydrogen atoms. The lithographic printing plate precursor as claimed in any one of claims 1 to 3, wherein R ₇ and R ₉ are hydrogen atoms.   The lithographic printing plate precursor as claimed in any one of claims 1 to 4, wherein the image recording layer further comprises (F) a hydrophobized precursor.   The lithographic printing plate precursor as claimed in any one of claims 1 to 5, wherein the protective layer further contains an inorganic stratiform compound.   The lithographic printing plate precursor according to any one of claims 1 to 6 is imagewise exposed, and then supplied with at least one of printing ink and fountain solution on a printing machine to form a non-image portion of the image recording layer. A method for making a plate, which comprises removing