JP4542932B2 - Planographic printing plate precursor and planographic printing method - Google Patents

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 by scanning with an infrared laser based on a digital signal from a computer or the like, and developing the lithographic printing plate precursor on a printing press, the so-called lithographic printing plate precursor. The present invention relates to a planographic printing method for printing.

In general, a lithographic printing plate comprises an oleophilic image area that receives ink during 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, 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 is left, 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 is to make the system unnecessary or simplified. In particular, in recent years, disposal of waste liquids discharged with wet processing has become a major concern for the entire industry due to consideration for the global environment, and therefore, the demand for solving the above-mentioned problems has become stronger.

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 of using a lithographic printing plate precursor having an image recording layer that can be dissolved or dispersed in an fountain solution, an ink solvent, or an emulsion of a fountain solution 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 force of the image recording layer by penetration of dampening water, ink solvent, etc., or between the image recording layer and the support. There is a method in which after the adhesive 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 unexposed portion of the image recording layer of the lithographic printing plate precursor and exposing the surface of the hydrophilic support, and “on-press development” refers to a liquid (usually printing ink) using a printing press. And / or a dampening solution) to remove the unexposed portion of the image recording layer of the lithographic printing plate precursor and expose the surface of the hydrophilic support.

On the other hand, in recent years, digitization techniques for electronically processing, storing, and outputting image information by a computer have become widespread, and various new image output methods corresponding to such digitization techniques are 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. Accordingly, obtaining a lithographic printing plate precursor adapted to such a technique is one of the important technical issues.

As described above, in recent years, 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.
However, when the conventional image recording method using light in the ultraviolet to visible region is used for simplification of plate making operations such as on-press development, the image recording layer is not fixed even after exposure, and thus has sensitivity to room light. After the lithographic printing plate precursor was taken out of the package, it was necessary to keep it completely shielded from light until the on-press development was completed.

Recently, high-power lasers such as semiconductor lasers and YAG lasers that emit infrared light with a wavelength of 760 to 1200 nm have become available at low cost. As a method for producing lithographic printing plates by scanning exposure that is easy to incorporate into digitization technology. Therefore, a method using these high-power lasers as an image recording light source has been considered promising.
In a conventional plate making method using light in the ultraviolet to visible region, a photosensitive lithographic printing plate precursor is subjected to imagewise exposure from low to medium illuminance, and image-like physical property changes due to photochemical reaction in the image recording layer. Record an image. 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 form or a structure is caused and the change is used for image recording. Therefore, 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 the plate making method using heat mode recording are that the image recording layer is not exposed to light at a normal illuminance level such as indoor lighting, and that fixing of an image recorded by high illumination exposure is not essential. is there. 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 performed by on-machine development, exposure is performed. Later, it is expected that a printing system in which an image is not affected even if exposed to ambient light in a room will be possible, and its realization is desired.

  As such a lithographic printing plate precursor, 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 is known ( For example, see Patent Document 1.) This lithographic printing plate precursor is exposed to an infrared laser, and the hydrophobic thermoplastic polymer particles are fused and coalesced by heat to form an image. Then, the lithographic printing plate precursor is attached onto a cylinder of a printing machine, dampening water and / or On-press development is possible by supplying ink.

  However, the method for forming an image by merging the polymer fine particles by simple thermal fusion as described above exhibits good on-press developability, but the image strength is extremely weak and the printing durability is insufficient.

  In order to improve the printing durability of such an on-press developable lithographic printing plate precursor, a thermosensitive layer comprising a microcapsule containing a compound having a functional group that reacts with heat on a hydrophilic support is provided. There is proposed a lithographic printing plate precursor comprising an infrared absorber contained in a heat-sensitive layer or an adjacent layer (see Patent Document 2 and Patent Document 3).

As another technique for improving printing durability, a lithographic printing plate precursor capable of on-press development, which is provided with a photosensitive layer containing an infrared absorber, a radical polymerization initiator, and a polymerizable compound on a support, is known. (See Patent Document 4).
The method using a reaction such as a polymerization reaction as described above can improve the image strength because the chemical bond density of the image portion is higher than that of the image portion formed by thermal fusion of polymer fine particles. However, it is still insufficient in terms of both on-press developability, fine line reproducibility and printing durability.

Japanese Patent No. 2938397 JP 2001-277740 A JP 2001-277742 A JP 2002-287334 A

  The present invention has been made in view of the above prior art, and provides a lithographic printing plate precursor excellent in on-press developability, fine line reproducibility, printing durability and printing stain performance, and a lithographic printing method using the same. The purpose is to do.

As a result of intensive studies to achieve the above object, the present inventor achieved the above object by including a copolymer containing a specific group in the image recording layer or other layer of the lithographic printing plate precursor. As a result, the present invention has been completed.
The present invention is as follows.

（一般式（Ａ２）中、Ｒ ₁ 〜Ｒ ₃ はそれぞれ独立に、水素原子、炭素数１〜６のアルキル基、またはハロゲン原子を表し、Ｌは−ＣＯ−、−Ｏ−、−ＮＨ−、二価の脂肪族基、二価の芳香族基およびそれらの組み合わせからなる群より選ばれる二価の連結基を表し、Ｑは下記各構造で表される基及びホスホン酸基から選ばれる少なくともいずれかを表す。）

（上記式中、Ｒ ₁₁ 〜Ｒ ₁₃ はそれぞれ独立に、水素原子、アルキル基、アリール基、アルキニル基、またはアルケニル基を表し、Ｍ ₁ およびＭ ₂ はそれぞれ独立に、水素原子、金属原子、またはアンモニウム基を表し、Ｘ ^- はカウンターアニオンを表す。）
繰り返し単位（ａ３）が、下記一般式（Ａ３）で表されるものであり、

（一般式（Ａ３）中、Ｒ ₁ 〜Ｒ ₃ はそれぞれ独立に、水素原子、炭素数１〜６のアルキル基、またはハロゲン原子を表し、Ｌは−ＣＯ−、−Ｏ−、−ＮＨ−、二価の脂肪族基、二価の芳香族基およびそれらの組み合わせからなる群より選ばれる二価の連結基を表し、Ｗは下記から選ばれる少なくともいずれかの基を表す。）

（上記式中、Ｍ ₁ は水素原子、金属原子、またはアンモニウム基を表し、Ｒ ₇ およびＲ ₈ はそれぞれ独立に、水素原子、あるいは炭素数１〜６の直鎖または分岐のアルキル基を表し、Ｒ ₉ は炭素数１〜６の直鎖または分岐のアルキレン基を表し、ｎは１〜１００の整数を表す。）
該共重合体（Ａ）と該共重合体（Ｂ）の混合割合は、該共重合体（Ａ）が５〜９５質量％であることを特徴とする平版印刷版原版。 (1) On a support, it contains (A) an infrared absorber, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer. By printing ink, fountain solution or both A repeating unit having a removable image recording layer, the undercoat layer provided between the support and the image recording layer containing at least (a1) at least one ethylenically unsaturated bond, and (a2 A copolymer (A) having a repeating unit containing at least one functional group that interacts with the support surface, and (a3) a repeating unit containing at least one hydrophilic functional group, and at least (a2) A copolymer (B) having a repeating unit containing at least one functional group that interacts with the support surface, and (a3) a repeating unit containing at least one hydrophilic functional group ,
The repeating unit (a2) is represented by the following general formula (A2),

(In General Formula (A2), R _{1 to} R ₃ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen atom, and L represents —CO—, —O—, —NH—, Represents a divalent linking group selected from the group consisting of a divalent aliphatic group, a divalent aromatic group, and combinations thereof, Q is at least any one selected from a group represented by the following structures and a phosphonic acid group Represents.)

(In the above formula, R _{11 to} R ₁₃ each independently represents a hydrogen atom, an alkyl group, an aryl group, an alkynyl group, or an alkenyl group, and M ₁ and M ₂ each independently represent a hydrogen atom, a metal atom, or Represents an ammonium group, and X ⁻ represents a counter anion.)
The repeating unit (a3) is represented by the following general formula (A3),

(In General Formula (A3), R _{1 to} R ₃ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen atom, and L represents —CO—, —O—, —NH—, And represents a divalent linking group selected from the group consisting of a divalent aliphatic group, a divalent aromatic group, and combinations thereof, and W represents at least one group selected from the following.

(Wherein, M ₁ is a hydrogen atom, a metal atom or an ammonium group, and R ₇ and R ₈ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, R ₉ represents a linear or branched alkylene group having 1 to 6 carbon atoms, and n represents an integer of 1 to 100.)
A lithographic printing plate precursor , wherein the copolymer (A) and the copolymer (B) are mixed at a ratio of 5 to 95% by mass of the copolymer (A) .

(2) The undercoat layer is provided by applying a coating solution prepared by mixing the copolymer (A) and the copolymer (B ). The lithographic printing plate precursor described in 1.

(3) After the lithographic printing plate precursor as described in (1) or (2) above is mounted on a printing machine and imagewise exposed with an infrared laser, or after imagewise exposure with an infrared laser, a printing machine A lithographic printing method comprising: printing on the lithographic printing plate precursor by supplying printing ink and fountain solution to remove the infrared unexposed portion of the image recording layer.

  According to the present invention, it is possible to provide a lithographic printing plate precursor having excellent on-press developability, fine line reproducibility, printing durability and printing stain performance, and a lithographic printing method using the same.

Hereinafter, the present invention will be described in detail.
The present invention relates to the lithographic printing plate precursor and the lithographic printing method described in (1) to (3) described in the section [Means for Solving the Problems]. Therefore, other matters were also described.
The lithographic printing plate precursor of the present invention comprises (A) an infrared absorber, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer on a support, and includes printing ink, dampening. An image-recording layer removable by water or both, and the image-recording layer or other layer includes at least (a1) a repeating unit containing at least one ethylenically unsaturated bond; and (a2) a support. A copolymer (A) having a repeating unit containing at least one functional group that interacts with the surface, (a3) a repeating unit containing at least one hydrophilic functional group, and at least (a2) a support surface And (a3) a copolymer (B) having a repeating unit containing at least one hydrophilic functional group. To.

(A1) Repeating unit containing at least one ethylenically unsaturated bond In the copolymer (A), the repeating unit containing at least one ethylenically unsaturated bond (hereinafter referred to as “repeat unit (a1)”) Is preferably a repeating unit represented by the following general formula (A1).

In the formula, R _{1 to} R ₃ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen atom. R _{4 to} R ₆ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, an acyl group, or an acyloxy group. Further, R ₄ and R ₅ , or R ₅ and R ₆ may form a ring. L represents a divalent linking group selected from the group consisting of -CO-, -O-, -NH-, a divalent aliphatic group, a divalent aromatic group, and combinations thereof.

Specific examples of L composed of combinations are given below. In the following examples, the left side is bonded to the main chain, and the right side is bonded to the ethylenically unsaturated bond.
L1: -CO-NH-divalent aliphatic group -O-CO-
L2: —CO—divalent aliphatic group —O—CO—
L3: -CO-O-divalent aliphatic group -O-CO-
L4: -Divalent aliphatic group -O-CO-
L5: -CO-NH-divalent aromatic group -O-CO-
L6: -CO-divalent aromatic group -O-CO-
L7: -Divalent aromatic group -O-CO-
L8: -CO-divalent aliphatic group-CO-O-divalent aliphatic group-O-CO-
L9: -CO-divalent aliphatic group-O-CO-divalent aliphatic group-O-CO-
L10: -CO-Divalent aromatic group -CO-O-Divalent aliphatic group -O-CO-
L11: -CO-Divalent aromatic group -O-CO-Divalent aliphatic group -O-CO-
L12: -CO-divalent aliphatic group-CO-O-divalent aromatic group-O-CO-
L13: -CO-Divalent aliphatic group -O-CO-Divalent aromatic group -O-CO-
L14: -CO-divalent aromatic group-CO-O-divalent aromatic group-O-CO-
L15: -CO-Divalent aromatic group -O-CO-Divalent aromatic group -O-CO-

The divalent aliphatic group means an alkylene group, a substituted alkylene group, an alkenylene group, a substituted alkenylene group, an alkynylene group, a substituted alkynylene group or a polyalkyleneoxy group. Of these, an alkylene group, a substituted alkylene group, an alkenylene group, and a substituted alkenylene group are preferable, and an alkylene group and a substituted alkylene group are more preferable.
The divalent aliphatic group is preferably a chain structure rather than a cyclic structure, and more preferably a linear structure than a branched chain structure.
The number of carbon atoms in the divalent aliphatic group is preferably 1 to 20, more preferably 1 to 15, further preferably 1 to 12, and further preferably 1 to 10. It is preferably 1 to 8, and most preferably.
Examples of the substituent of the divalent aliphatic group include a halogen atom (F, Cl, Br, I), a hydroxyl group, a carboxyl group, an amino group, a cyano group, an aryl group, an alkoxy group, an aryloxy group, and an acyl group. , Alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, monoalkylamino group, dialkylamino group, arylamino group and diarylamino group.

The divalent aromatic group means an aryl group or a substituted aryl group. Preferable are phenylene, substituted phenylene group, naphthylene and substituted naphthylene group.
Examples of the substituent for the divalent aromatic group include an alkyl group in addition to the examples of the substituent for the divalent aliphatic group.

(A2) Repeating unit containing at least one functional group that interacts with the support surface In the copolymers (A) and (B), a repeating unit containing at least one functional group that interacts with the support surface The unit (hereinafter also referred to as “repeating unit (a2)”) is preferably a repeating unit represented by the following general formula (A2).

In formula, R < ₁ > -R < ₃ > and L are synonymous with what is represented by said Formula (A1). Q represents a functional group that interacts with the support surface (hereinafter sometimes abbreviated as “specific functional group”).
Specific functional groups include, specifically, Si—OH, Si—O ⁻ , Al ³⁺ , aluminum oxide, zirconium oxide, etc. on the support surface, covalent bond, ionic bond, hydrogen bond, polar interaction, van der Waals Examples include groups capable of interaction such as interaction. Specific examples of the specific functional group are listed below.

(In the above formula, R _{11 to} R ₁₃ each independently represents a hydrogen atom, an alkyl group, an aryl group, an alkynyl group, or an alkenyl group, and M ₁ and M ₂ each independently represent a hydrogen atom, a metal atom, or Represents an ammonium group, and X ⁻ represents a counter anion.)
Among these, the specific functional group is preferably an onium base such as an ammonium group or a pyridinium group, or a β-diketone group such as a phosphate group, a phosphonic acid group, a boric acid group, or an acetylacetone group.

In the general formula (A2), L represents a divalent linking group selected from the group consisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalent aromatic group, and combinations thereof. To express.
Specific examples of L composed of a combination include the following in addition to the specific examples of L in the above (A1). In the following examples, the left side is bonded to the main chain, and the right side is bonded to a specific functional group.
L16: —CO—NH—
L17: -CO-O-
L18: -Divalent aromatic group-

(A3) Repeating unit containing at least one hydrophilic functional group In the copolymers (A) and (B), a repeating unit containing at least one hydrophilic functional group (hereinafter referred to as “repeating unit (a3)”) In the case where the hydrophilic functional group is —COOM ₁ , —SO ₃ M ₁ , —OH, —OSO ₂ M ₁ , —CONR ₇ R ₈ , —P (═O) (OM ₁ ) ₂ or — (R ₉ O) _n —R ₇ (wherein M ₁ represents hydrogen, a metal ion or an ammonium ion, R ₇ and R ₈ each independently represents a hydrogen atom or an alkyl group, and R ₉ represents It represents a divalent hydrocarbon group, and n is preferably an integer of 1 to 100).

  The repeating unit having at least one hydrophilic functional group is preferably represented by the following general formula (A3).

In formula, R < ₁ > -R < ₃ > and L are synonymous with what is represented by said Formula (A1). W represents the following group.

However, M ₁ is the same meanings as those represented in the description of the formula (A2).
R ₇ and R ₈ each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.
R ₉ represents a linear or branched alkylene group having 1 to 6 carbon atoms.
n represents an integer of 1 to 100.

  As a molecular weight of a copolymer (A), the range of 500-100,000 is preferable at a mass mean molecular weight, and the range of 700-50,000 is more preferable. Further, the repeating unit (a1) is preferably 5 to 80 mol%, more preferably 10 to 50 mol%, based on all copolymerized monomers. The repeating unit (a2) is preferably from 5 to 80 mol%, more preferably from 10 to 50 mol%, based on all copolymerized monomers. Furthermore, the repeating unit (a3) is preferably from 5 to 80 mol%, more preferably from 10 to 50 mol%, based on all copolymerized monomers.

  As a molecular weight of a copolymer (B), the range of 500-100,000 is preferable at a mass mean molecular weight, and the range of 700-50,000 is more preferable. Further, the repeating unit (a2) is preferably 5 to 80 mol%, more preferably 10 to 50 mol%, based on all copolymerized monomers. Further, the repeating unit (a3) is preferably from 20 to 95 mol%, more preferably from 50 to 90 mol%, based on all copolymerized monomers.

  Specific examples of the copolymer (A) used in the present invention are shown below, but are not limited thereto.

  Specific examples of the copolymer (B) used in the present invention are shown below, but are not limited thereto.

In the present invention, the copolymers (A) and (B) can be used in an image recording layer, or an undercoat layer (intermediate layer) provided between the support and the image recording layer. Although it can be contained in a layer adjacent to the image recording layer, it is particularly preferred to use it in the undercoat layer because the effects of the present invention are sufficiently exhibited. 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. Further, in the unexposed area, the on-press developability is improved because the image recording layer is easily peeled off from the support.
In the present invention, when the copolymers (A) and (B) are used for the undercoat layer, the copolymer is usually diluted with a solvent. Examples of the solvent include water and organic solvents such as methanol, ethanol, propanol, isopropanol, ethylene glycol, hexylene glycol, THF, DMF, 1-methoxy-2-propanol, dimethylacetamide, dimethyl sulfoxide, and particularly alcohols. Is preferred. These organic solvents can also be mixed and used.

As a density | concentration of undercoat layer coating liquid, 0.001-10 mass% is preferable, More preferably, it is 0.01-5 mass%, More preferably, it is 0.05-1 mass%. A surfactant described later may be added to the undercoat layer as necessary.
The mixing ratio of the copolymer (A) and the copolymer (B) can be used at any mixing ratio as long as the effect of the present invention is expressed. 5 to 95 mass% is preferable, and 10 to 90 mass% is more preferable. In this range, the printing durability and stain resistance of the printing plate are improved.

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.

Next, the image recording layer in the planographic printing plate precursor according to the invention will be described in detail.
The lithographic printing plate precursor of the present invention comprises (A) an infrared absorber, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer on a support, and includes printing ink, dampening. It has an image recording layer that can be removed by water or both.
Hereinafter, each component constituting the image recording layer will be described in detail.

[(A) Infrared absorber]
The image recording layer in the present invention contains an infrared absorbing agent in order to enable efficient image formation using a laser emitting infrared light of 760 to 1200 nm as a light source. The infrared absorber has a function of converting absorbed infrared rays into heat. With the heat generated at this time, a polymerization initiator (radical generator) described later is thermally decomposed to generate radicals. Such an infrared absorber used in the present invention is a dye or pigment having an absorption maximum at a wavelength of 760 to 1200 nm.

Examples of the dye include commercially available dyes and, for example, “Dye Handbook” (edited by the Society of Synthetic Organic Chemistry, Showa 45).
The publicly known thing described in literature, such as an annual publication, can be utilized. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Is mentioned.
Preferred dyes include, for example, cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-60-78787, JP-A-58-173696, The methine dyes described in JP-A-58-181690 and JP-A-58-194595, JP-A-58-112793, JP-A-58-224793, JP-A-59-48187, Naphthoquinone dyes described in JP-A-59-73996, JP-A-60-52940, JP-A-60-63744, and the like, squarylium dyes described in JP-A-58-112792, and the like; And cyanine dyes described in British Patent No. 434,875.

  Further, a near infrared absorption sensitizer described in US Pat. No. 5,156,938 is also preferably used, and a substituted arylbenzo (thio) described in US Pat. No. 3,881,924 is also preferred. ) Pyrylium salt, trimethine thiapyrylium salt described in JP-A-57-142645 (US Pat. No. 4,327,169), JP-A-58-181051, 58-220143, 59- No. 41363, No. 59-84248, No. 59-84249, No. 59-146063, No. 59-146061, and Pyrlium compounds described in JP-A-59-216146. In US Pat. No. 4,283,475, the pentamethine thiopyrylium salt, etc., and Japanese Patent Publication Nos. 5-13514 and 5-19702 are disclosed. Pyrylium compounds are also preferably used. Another example of a preferable dye is a near-infrared absorbing dye described in US Pat. No. 4,756,993 as formulas (I) and (II).

  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 preferable, and one particularly preferable example is a cyanine dye represented by the following general formula (i).

During formula (i), X ¹ represents a hydrogen atom, a halogen atom, -NPh _2, X ² -L ¹ or a group shown below.

X ² in the general formula (i) represents an oxygen atom, a nitrogen atom, or a sulfur atom, and L ¹ is a hydrocarbon group having 1 to 12 carbon atoms, an aromatic ring having a hetero atom, or carbon containing a hetero atom. A hydrocarbon group having 1 to 12 atoms is shown. In addition, a hetero atom here shows N, S, O, a halogen atom, and 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. Ph represents a phenyl group.

R ¹ and R ² in the general formula (i) each independently represent a hydrocarbon group having 1 to 12 carbon atoms. From the storage stability of the 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 are bonded to each other to form a 5-membered ring or It is particularly preferable that a 6-membered ring is formed.

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, carboxyl 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 (i) 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, and a sulfonate ion, particularly preferably a perchlorate ion, a hexagonal salt, in view of the storage stability of the recording layer coating solution. Fluorophosphate ion and aryl sulfonate ion.

Specific examples of cyanine dyes represented by formula (i) that can be suitably used in the present invention include those described in paragraph numbers [0017] to [0019] of JP-A No. 2001-133969. Can do.
Other particularly preferable examples include specific indolenine cyanine dyes described in JP-A-2002-278057.
Furthermore, the infrared absorber is preferably water-soluble, but when it is water-insoluble, it can be added by a method such as dispersion or dissolution in a mixed solvent.

Examples of the pigment used in the present invention include commercially available pigments and color indexes (C.I.
. ) Handbook, “Latest Pigment Handbook” (edited by the Japan Pigment Technology Association, published in 1977), “Latest Pigment Applied Technology” (published by CMC, 1986), “Printing Ink Technology”, published by CMC, published in 1984) Is available.

  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” (Yokoshobo), “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 μm to 10 μm, more preferably in the range of 0.05 μm to 1 μm, and particularly preferably in the range of 0.1 μm to 1 μm. Within this range, good stability of the pigment dispersion in the image recording layer coating solution and good uniformity of the image recording layer can be obtained.

  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).

  The addition of these infrared absorbers to the image recording layer is preferably made the minimum necessary amount in order to suppress side effects that inhibit the polymerization reaction.

  These infrared absorbers are added in a proportion of 0.001 to 50% by mass, preferably 0.005 to 30% by mass, particularly preferably 0.01 to 10% by mass, based on the total solid content of the image recording layer. Can do. Within this range, high sensitivity can be obtained without adversely affecting the uniformity and film strength of the image recording layer.

  Among these infrared absorbers described above, a preferable dye is a cyanine dye represented by the general formula (i).

[(B) polymerization initiator]
The polymerization initiator that can be used in the present invention generates radicals by heat, light, or both energies, and initiates and advances the curing reaction of the polymerizable compound described later. As a polymerization initiator for this purpose, a thermal decomposition type radical generator that decomposes by heat to generate radicals is useful. Such a radical generator is used in combination with the above-described infrared absorber, so that when the infrared laser is irradiated, the infrared absorber generates heat, and the heat generates radicals. Is possible.
Examples of radical generators include onium salts, triazine compounds having a trihalomethyl group,
A peroxide, an azo polymerization initiator, an azide compound, a quinonediazide and the like can be mentioned, and an onium salt is preferable because of its high sensitivity. Below, the onium salt which can be used suitably as a radical polymerization initiator in this invention is demonstrated. Preferred onium salts include iodonium salts, diazonium salts, and sulfonium salts. In the present invention, these onium salts function not as acid generators but as radical polymerization initiators. The onium salts particularly preferably used in the present invention are onium salts represented by the following general formulas (ii) to (iv).

In formula (ii), Ar ¹¹ and Ar ¹² each independently represent an aryl group having 20 or less carbon atoms, which may have a substituent. Preferred substituents when this aryl group has a substituent include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, or a carbon atom having 12 or less carbon atoms. An aryloxy group is mentioned. Z ¹¹⁻ represents a counter ion selected from the group consisting of a halogen ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a carboxylate ion, and a sulfonate ion, preferably a perchlorate ion, Hexafluorophosphate ions, carboxylate ions, and aryl sulfonate ions.

In the formula (iii), Ar ²¹ represents an aryl group having 20 or less carbon atoms which may have a substituent. Preferred examples of the substituent include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, an aryloxy group having 12 or less carbon atoms, and 12 or less carbon atoms. Examples thereof include an alkylamino group, a dialkylamino group having 12 or less carbon atoms, an arylamino group having 12 or less carbon atoms, or a diarylamino group having 12 or less carbon atoms. Z ^21- represents a counter ion having the same ^meaning as Z ^11- .

In formula (iv), R ³¹ , R ³² and R ³³ may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferable substituents include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, or an aryloxy group having 12 or less carbon atoms. Z ^31- represents a counter ion having the same ^meaning as Z ^11- .

Specific examples of onium salts that can be suitably used as a radical generator in the present invention include those described in JP-A Nos. 2001-133969, 2001-343742, and 2002-148790. Can be mentioned. In the present invention, onium salts represented by general formula (ii) ([OI-1] to [OI-10]) and onium salts represented by general formula (iii) ([ON -1] to [ON-5]), and specific examples of onium salts ([OS-1] to [OS-10]) represented by the general formula (iv), but are not limited thereto. .

  The radical generator used in the present invention preferably has a maximum absorption wavelength of 400 nm or less. More preferably, the maximum absorption wavelength is 360 nm or less, and most preferably 300 nm or less. By making the absorption wavelength in the ultraviolet region in this way, the lithographic printing plate precursor can be handled under white light.

  These polymerization initiators are added in a proportion of 0.1 to 50% by mass, preferably 0.5 to 30% by mass, particularly preferably 1 to 20% by mass, based on the total solid content constituting the image recording layer. Can do. Within this range, good sensitivity and good stain resistance of the non-image area during printing can be obtained. These 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.

[(C) Polymerizable compound]
The polymerizable compound used in the image recording layer in the present invention is an addition polymerizable compound having at least one ethylenically unsaturated double bond, and a compound having at least one terminal ethylenically unsaturated bond, preferably two or more. Chosen from. 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, isocyanuric acid ethylene oxide (EO) Examples include modified triacrylates and polyester acrylate oligomers.

  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- Those having an aromatic skeleton described in JP-A No. 5241 and JP-A-2-226149 and those containing 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 No. 54-21726.

  Further, urethane-based addition polymerizable compounds produced by using an addition reaction of isocyanate and hydroxyl group are also suitable. Specific examples thereof include, for example, one molecule described in JP-B-48-41708. A vinylurethane compound 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 Etc.

_{CH 2 = C (R 4)} COOCH 2 CH (R 5) OH (A)
(However, 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, JP-B-2-16765, JP-B-58-49860, JP-B-56- Urethane compounds having an ethylene oxide skeleton described in Japanese Patent No. 17654, Japanese Patent Publication No. 62-39417, and Japanese Patent Publication No. 62-39418 are also suitable. Furthermore, 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 are used. Depending on the case, 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. In addition, specific unsaturated compounds described in JP-B-46-43946, JP-B-1-40337, JP-B-1-40336, and vinylphosphonic acid-based compounds described in JP-A-2-25493 are also included. Can 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 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 area, that is, the cured film, those having three or more functionalities are preferable. A method of adjusting both sensitivity and strength by using a compound) is also effective.
In addition, the compatibility and dispersibility with other components in the image recording layer (for example, binder polymer, polymerization initiator, colorant, etc.), the selection and use method of the polymerizable compound is an important factor, For example, the compatibility may be improved by using a low-purity compound or using two or more kinds in combination. In addition, a specific structure may be selected for the purpose of improving adhesion to a support or an overcoat layer described later.

  The polymerizable compound is used in the image recording layer in an amount of preferably 5 to 80% by mass, more preferably 25 to 75% by mass. These may be used alone or in combination of two or more. In addition, the usage of the polymerizable compound can be arbitrarily selected from the viewpoint of polymerization inhibition with respect to oxygen, resolution, fogging, refractive index change, surface adhesiveness, etc. The layer construction and coating method such as undercoating and overcoating can also be carried out.

[(D) Binder polymer]

<Binder polymer>
In the present invention, a binder polymer is used as an essential component for improving the film characteristics and on-press developability of the image recording layer. A conventionally well-known thing can be used as a binder polymer without a restriction | limiting, The linear organic polymer which has film property is preferable. 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 or may be introduced by a polymer reaction.

  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 ethylenically unsaturated bonds in the side chain of the molecule are polymers of esters or amides of acrylic acid or methacrylic acid, at least of the residue of the ester or amide (-COOR or CONHR R) Mention may be made of polymers having some ethylenically unsaturated bonds.

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) in ₂ -X (wherein, R ¹ each to R ³ is a hydrogen atom, a halogen atom or an alkyl group having 1 to 20 carbon atoms, an aryl group, an alkoxy R ¹ and R ² or R ³ may be bonded to each other to form a ring, n represents an integer of 1 to 10. X represents a dicyclopentadienyl residue. Represents a group).

Specific examples of the ester residue include —CH ₂ CH═CH ₂ , —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 OCOC (CH 3) = CH 2, -CH 2 CH 2 OCOCH = CH 2, -CH 2 CH 2 -NHCOO -CH ₂ CH = CH ₂ and CH ₂ CH (wherein, X represents a dicyclopentadienyl residue.) ₂ O-X and the like.
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 crosslink 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 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 of the image recording layer unexposed portion, 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. For this reason, 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, carboxyl 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 glycol , Hydroxypropylene polymers, polyvinyl alcohol, hydrolyzed polyvinyl acetate, polyvinyl formal, polyvinyl butyral, polyvinyl pyrrolidone, acrylamide homopolymers and copolymers having a hydrolysis degree of 60% by mass or more, preferably 80% by mass or more Methacrylamide homopolymers and polymers, N-methylolacrylamide homopolymers and copolymers, polyvinylpyrrolidone, alcohol-soluble nylon, polyether of 2,2-bis- (4-hydroxyphenyl) -propane and epichlorohydrin, etc. Is mentioned.

  The binder polymer preferably has a mass average molecular weight of 5,000 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 (mass average molecular weight / number average molecular weight) is preferably 1.1 to 10.

The binder polymer may be a random polymer, a block polymer, a graft polymer, or the like, but is preferably a random polymer.
Such a binder polymer can be synthesized by a conventionally known method. The binder polymer having a crosslinkable group in the side chain can be easily synthesized by radical polymerization or polymer reaction.

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 preferably 10 to 90% by mass and more preferably 20 to 80% 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 a polymeric compound and a binder polymer in the quantity used as 1 / 9-7 / 3 by mass ratio.

[Other components of image recording layer]
In the image recording layer in the present invention, components other than the above (A) to (D), for example, surfactant, colorant, print-out agent, polymerization inhibitor (thermal polymerization inhibitor), higher fatty acid derivative, plasticizer Inorganic fine particles, low molecular weight hydrophilic compounds and the like can be contained.

<Surfactant>
In the present invention, it is preferable to use a surfactant in the image recording layer in order to promote on-press developability at the start of printing and to improve the coated surface state. Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and fluorosurfactants. 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 acid esters, and imidazolines.

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

  Further preferred surfactants include fluorine-based surfactants containing a perfluoroalkyl group in the molecule in addition to the component (D) in the present invention. 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 types 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 surfactant is preferably contained in the image recording layer in an amount of 0.001 to 10% by mass, and more preferably 0.01 to 5% by mass.

<Colorant>
In the image recording layer of the present invention, 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) 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 JP-A-62-2 And dyes described in Japanese Patent No. 293247. Also, pigments such as phthalocyanine pigments, azo pigments, carbon black, titanium oxide, etc. can be suitably used.

<Bakeout agent>
In the image recording layer of the present invention, a compound that is discolored by an acid or a radical can be added 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.

  It is preferable to add the dye which changes color by an acid or a radical to the image recording layer at a ratio of 0.01 to 10% by mass.

<Thermal polymerization inhibitor>
In order to prevent unnecessary thermal polymerization of the polymerizable compound (C) during production or storage of the image recording layer, a small amount of a thermal polymerization inhibitor is preferably added to the image recording layer in 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), N-nitroso-N-phenylhydroxylamine aluminum salt are preferred.
The thermal polymerization inhibitor is preferably contained in the image recording layer in an amount of about 0.01 to about 5% by mass.

<Higher fatty acid derivatives, etc.>
In the image recording layer of the present invention, a higher fatty acid derivative such as behenic acid or behenic acid amide or the like is added to prevent polymerization inhibition due to oxygen, and the surface of the image recording layer is dried during coating. 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 in the 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 is preferably contained in the image recording layer at a ratio of about 30% by mass or less.

<Inorganic fine particles>
The image recording layer in the present invention may contain inorganic fine particles in order to enhance the interfacial adhesiveness by surface roughening, improve the cured film strength of the image area, and improve 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 is preferably exemplified.
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, which 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 in the invention may contain a hydrophilic low molecular weight compound for improving on-press developability. Examples of hydrophilic low-molecular compounds 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.

(Formation of image recording layer)
In the present invention, several modes can be used as a method for incorporating the above-mentioned image recording layer constituents 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, for example, JP-A-2002-287334. In another embodiment, for example, as described in JP-A-2001-277740 and JP-A-2001-277742, all or part of the components (A) to (D) are encapsulated in a microcapsule. It is a microcapsule type image recording layer to be contained in the recording layer. further. In the microcapsule type image recording layer, the constituent component may be contained outside the microcapsule. Here, it is preferable that the microcapsule-type image recording layer includes a hydrophobic constituent component in the microcapsule and a hydrophilic constituent component outside the microcapsule. In order to obtain better on-press developability, it is advantageous that the image recording layer is a microcapsule type image recording layer.

  As a method of microencapsulating the above-mentioned image recording layer constituent components, known methods 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 polymer precipitation method, 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 the microcapsule wall the compound which has crosslinkable functional groups, such as the said ethylenically unsaturated bond which can introduce | transduce the binder polymer.

Such microcapsules may or may not be combined with each other by heat. In short, among the microcapsule inclusions, the one that oozes out from the surface of the microcapsule or the microcapsule at the time of application, or the one that enters the microcapsule wall may cause a chemical reaction by heat. Moreover, you may react with the added hydrophilic resin or the added low molecular weight compound. Furthermore, two or more types of microcapsules may be reacted with each other by providing functional groups that react with each other with different functional groups. Therefore, it is preferable for image formation that the microcapsules are fused and united with heat, but it is not essential.
The addition amount of the microcapsules to the image recording layer (image forming layer) is preferably 50% by mass or more, and more preferably 60 to 95% by mass in terms of solid content. Within this range, good sensitivity and good printing durability can be obtained simultaneously with good developability.

  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.

  When the microcapsules are contained in the image recording layer of the present invention, a solvent capable of dissolving the inclusion and swelling the wall material can be added to the microcapsule dispersion medium. By such a solvent, diffusion of the encapsulated compound having a heat-reactive functional group to the outside of the microcapsule is promoted. Such a solvent depends on the microcapsule dispersion medium, the material of the microcapsule wall, the wall thickness, the inclusion, and the like, but can be easily selected from many commercially available solvents. For example, in the case of a water-dispersible microcapsule comprising a crosslinked polyurea or polyurethane wall, alcohols, ethers, acetals, esters, ketones, polyhydric alcohols, amides, amines, fatty acids and the like are preferable.

  Specific examples of the solvent include methanol, ethanol, tertiary butanol, n-propanol, tetrahydrofuran, methyl lactate, ethyl lactate, methyl ethyl ketone, propylene glycol monomethyl ether, ethylene glycol diethyl ether, ethylene glycol monomethyl ether, γ-butyrolactone, N , N-dimethylformamide, N, N-dimethylacetamide, and the like. Two or more of these solvents may be used. A solvent that does not dissolve in the microcapsule dispersion but dissolves when the solvent is mixed can also be used.

  The amount of the solvent added is determined by the combination of materials, but usually 5 to 95% by mass of the coating solution is effective, and a preferable range is 10 to 90% by mass, and a more preferable range is 15 to 85% by mass. %.

The image recording layer in the present invention is formed by preparing and applying a coating solution by dispersing or dissolving necessary constituents in a solvent using any of the above-described embodiments. 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 of 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.

Image recording layer coating weight (solids) is preferably from ^{0.3~1.5g / m 2, 0.5~1.5g / m} 2 is more preferable.
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.

[Overcoat layer]
The planographic printing plate precursor of the present invention can be removed with printing ink, fountain solution or both for purposes such as preventing scratches in the image recording layer, blocking oxygen, and preventing ablation during high-intensity laser exposure. An overcoat layer (protective layer) can be provided on the image recording layer.
In the present invention, the exposure is usually carried out in the atmosphere, but the overcoat layer is made up of low molecular compounds such as oxygen and basic substances present in the atmosphere that inhibit the image forming reaction caused by exposure in the image recording layer. It prevents mixing into the image recording layer and prevents an image formation reaction from being hindered by exposure in the atmosphere. Therefore, the properties desired for the overcoat layer are low permeability of low-molecular compounds such as oxygen, furthermore, good transparency of light used for exposure, and excellent adhesion to the image recording layer, And it is preferable that it can be easily removed in the on-press development process after exposure. Various studies have been made on overcoat 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 overcoat 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 overcoat layer, and part of the polyvinyl alcohol The copolymer component may be included.
Specific examples of polyvinyl alcohol include those having a molecular weight of 300 to 2400 hydrolyzed by 71 to 100%. 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 overcoat layer (selection of PVA, use of additives, etc.), coating amount, and the like are appropriately selected in consideration of fogging, 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 overcoat layer), and the thicker the film thickness, the higher the oxygen barrier property. preferable. Further, in order to prevent unnecessary polymerization reaction during production and storage, unnecessary fogging during image exposure, image line thickening, 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 (cc / m ² · day).
The molecular weight of the (co) polymer such as polyvinyl alcohol (PVA) is 2000 to 100.
Those in the range of 100,000 can be used, and those in the range of 20,000 to 3,000,000 are suitable.

  As another composition of the overcoat layer, glycerin, dipropylene glycol and the like can be added in an amount corresponding to several mass% with respect to the (co) polymer to give flexibility. Anionic surfactants such as sodium sulfonate; amphoteric surfactants such as alkylaminocarboxylates and alkylaminodicarboxylates; nonionic surfactants such as polyoxyethylene alkylphenyl ethers to (co) polymers Several mass% can be added.

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

On the other hand, various proposals have been made to improve the adhesion between the image recording layer and the overcoat layer. For example, in JP-A-49-70702 and British Patent Application No. 1303578, a hydrophilic polymer mainly composed of polyvinyl alcohol, an acrylic emulsion, a water-insoluble vinylpyrrolidone-vinyl acetate copolymer, etc. 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 overcoat 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 overcoat 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, safe light is not caused. Suitability can be improved.

  The thickness of the overcoat layer is suitably from 0.1 to 5 μm, particularly preferably from 0.2 to 2 μm.

[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 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 the roughening treatment of 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 of anodizing treatment vary depending on the electrolyte used, and thus cannot be specified in general. In general, however, an electrolyte concentration of 1 to 80% by mass solution, a liquid temperature of 5 to 70 ° C., a current density of 5 to 60 A / d m 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 with 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]
A back coat can be provided on the back surface of the support, if necessary, after surface treatment or after forming an undercoat layer on the support.
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.

[Plate making, printing]
In the planographic printing method of the present invention, the above-described planographic printing plate precursor of the present invention is 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. Further, the amount of irradiation energy is preferably 10 to 300 mJ / cm ^2.

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, the oil-based ink and the 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 an oil-based ink without passing through a development processing step such as a wet development processing step, in the exposed portion 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 portion, the uncured image recording layer is dissolved or dispersed and removed by the supplied aqueous component and / or oil-based ink, and a hydrophilic surface is exposed in the portion.
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 oil-based ink may be first supplied to the plate surface, but the oil-based ink is first used in order 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 the oil-based ink, a dampening water for normal lithographic printing and a printing ink 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.

Hereinafter, although an example and a comparative example explain the present invention in detail, the present invention is not limited to these. In addition, Example 3, 7, 11, and 14 shall be read as the reference example 3, 7, 11, and 14, respectively.

Example 1
(A) Production of Support Using an aluminum plate according to JIS-A-1050 having a thickness of 0.3 mm, the following steps (a) to (k) were carried out in this order and processed.

(A) Mechanical surface roughening treatment While supplying a suspension of abrasive (silica sand) having a specific gravity of 1.12. Roughening was performed. The average particle size of the abrasive was 8 μm, and the maximum particle size was 50 μm. The material of the nylon brush was 6 · 10 nylon, the hair length was 50 mm, and the hair diameter was 0.3 mm. The nylon brush was planted so as to be dense by making a hole in a stainless steel tube having a diameter of 300 mm. Three rotating brushes were used. The distance between the two support rollers (Φ200 mm) at the bottom of the brush was 300 mm. The brush roller was pressed until the load of the drive motor for rotating the brush became 7 kW plus with respect to the load before the brush roller was pressed against the aluminum plate. The rotating direction of the brush was the same as the moving direction of the aluminum plate. The rotation speed of the brush was 200 rpm.

(B) Alkali etching treatment The obtained aluminum plate was sprayed with an aqueous NaOH solution (concentration: 26 mass%, aluminum ion concentration: 6.5 mass%) at a temperature of 70 ° C. to dissolve the aluminum plate by 6 g / m ^2. did. Thereafter, washing with water was performed using well water.

(C) Desmutting treatment The desmutting treatment was performed by spraying with a 1% by mass aqueous solution of nitric acid at a temperature of 30 ° C. (containing 0.5% by mass of aluminum ions), and then washed with water by spraying. The nitric acid aqueous solution used for the desmut was the waste liquid from the step of electrochemical surface roughening using alternating current in nitric acid aqueous solution.

(D) Electrochemical roughening treatment An electrochemical roughening treatment was carried out continuously using an alternating voltage of 60 Hz. The electrolytic solution at this time was a nitric acid 10.5 g / liter aqueous solution (aluminum ion 5 g / liter) at a temperature of 50 ° C. The AC power supply waveform has an electrochemical surface roughening treatment using a carbon electrode as a counter electrode using a trapezoidal rectangular wave alternating current with a time TP of 0.8 ms until the current value reaches a peak from zero, a DUTY ratio of 1: 1. went. Ferrite was used for the auxiliary anode. The electrolytic cell used was a radial cell type. The current density was 30 A / dm ² at the peak current value, and the amount of electricity was 220 C / dm ² in terms of the total amount of electricity when the aluminum plate was the anode. 5% of the current flowing from the power source was shunted to the auxiliary anode. Thereafter, washing with water was performed using well water.

(E) Alkali etching treatment The aluminum plate was sprayed at a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass at 32 ° C. to dissolve the aluminum plate by 0.20 g / m ² , The smut component mainly composed of aluminum hydroxide generated when electrochemical surface roughening was used was removed, and the edge portion of the generated pit was melted to smooth the edge portion. Thereafter, washing with water was performed using well water. The etching amount was 3.5 g / m ² .

(F) Desmut treatment Desmut treatment by spraying was performed with a 15% by weight aqueous solution of nitric acid at a temperature of 30 ° C. (including 4.5% by weight of aluminum ions), and then washed with water using well water. The nitric acid aqueous solution used for the desmut was the waste liquid from the step of electrochemical surface roughening using alternating current in nitric acid aqueous solution.

(G) Electrochemical roughening treatment An electrochemical roughening treatment was carried out continuously using an alternating voltage of 60 Hz. The electrolytic solution at this time was a hydrochloric acid 7.5 g / liter aqueous solution (containing 5 g / liter of aluminum ions) at a temperature of 35 ° C. The AC power supply waveform was a rectangular wave, and an electrochemical surface roughening treatment was performed using a carbon electrode as a counter electrode. Ferrite was used for the auxiliary anode. The electrolytic cell used was a radial cell type. The current density was 25 A / dm ² at the peak current value, and the amount of electricity was 50 C / dm ² in terms of the total amount of electricity when the aluminum plate was the anode. Thereafter, washing with water was performed using well water.

(H) Alkali etching treatment The aluminum plate was sodium hydroxide concentration of 26 wt%, performed an aluminum ion concentration of 6.5 wt% to etching treatment by spraying at 32 ° C., the aluminum plate 0.10 g / m ² was dissolved, the alternating current in the previous stage The smut component mainly composed of aluminum hydroxide generated during the electrochemical surface roughening treatment was removed, and the edge portion of the generated pit was melted to smooth the edge portion. Thereafter, washing with water was performed using well water.

(I) Desmut treatment A desmut treatment by spraying was performed with a 25% by mass aqueous solution of sulfuric acid at a temperature of 60 ° C. (containing 0.5% by mass of aluminum ions), and then water washing by spraying was performed using well water.

(J) Anodizing treatment As the electrolytic solution, sulfuric acid was used. All electrolytes had a sulfuric acid concentration of 170 g / liter (containing 0.5 mass% of aluminum ions), and the temperature was 43 ° C. Thereafter, washing with water was performed using well water. Both current densities were about 30 A / dm ² . The final oxide film amount was 2.7 g / m ² .

(K) Alkali metal silicate treatment An alkali metal silicate treatment (silicate treatment) was performed by immersing the obtained aluminum plate in a treatment layer of a 1 mass% aqueous solution of sodium silicate No. 3 at a temperature of 30 ° C. for 10 seconds. ) Then, the aluminum support body was produced by performing the water washing by the spray using well water. The amount of silicate adhering at that time was 3.6 mg / m ² .

(B) Formation of undercoat layer and image recording layer On the support prepared above, copolymer (A) represented by specific example (A16) (x / y / z = 20/20/60, mass average) 5% by weight methanol solution (copolymer (A) / copolymer) containing copolymer (B) (a / b = 20/80, weight average molecular weight 180,000) represented by specific example (B16) and molecular weight 25000) After combining (B) = 50/50 mass ratio), it was oven-dried at 70 ° C. for 30 seconds to form an undercoat layer having a dry coating amount of 10 mg / m ² .
Subsequently, an image recording layer coating solution (1) having the following composition was bar coated, 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. I got the original version.

Image recording layer coating solution (1)
・ Water 100g
・ The following microcapsule (1) (in terms of solid content) 5 g
-0.5 g of the following polymerization initiator (1)
・ 0.2 g of the following fluorosurfactant (1)

(Synthesis of microcapsule (1))
As an oil phase component, trimethylolpropane and xylene diisocyanate adduct (manufactured by Mitsui Takeda Chemical Co., Ltd., Takenate D-110N) 10 g, pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., SR444) 3.15 g, The following infrared absorber (1) 0.35 g and Pionein A-41C (manufactured by Takemoto Yushi Co., Ltd.) 0.1 g were 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. All of the average particle diameters were 0.3 μm.

(C) Exposure and printing The resulting lithographic printing plate precursor was exposed with a Trendsetter 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 obtained 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 on-press development of the unexposed part of the image recording layer was completed on the printing press and the number of printing papers required until the ink was not transferred to the printing paper was measured as on-press developability, Even when the planographic printing plate precursor was used, a printed matter having no non-image area stain was obtained within 50 sheets.

(D) Evaluation In general, in the case of a negative lithographic printing plate precursor, when the exposure amount is small, the degree of cure of the image recording layer (photosensitive layer) decreases, and when the amount of exposure is large, the degree of cure increases. If the image recording layer has a too low degree of curing, the printing durability of the lithographic printing plate will be low, and the reproducibility of small dots and fine lines will be poor. On the other hand, when the degree of cure of the image recording layer is high, the printing durability is high, and the reproducibility of small dots and fine lines is good.
In this example, as shown below, the negative lithographic printing plate precursor obtained as described above was evaluated for printing durability and fine line reproducibility under the same exposure amount conditions described above. It was used as an index of sensitivity. That is, it can be said that the sensitivity of the lithographic printing plate precursor is higher as the number of printed sheets in printing durability is higher and the fine line width in fine line reproducibility is narrower.

(1) Fine line reproducibility As described above, after 100 sheets were printed and it was confirmed that a printed matter having no ink stains in the non-image area was obtained, 500 sheets were continuously printed. A thin line chart of the 600th printed material (charts with 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 60, 80, 100 and 200 μm fine lines exposed) with a 25X magnifier The fine line reproducibility was evaluated by observing and the fine line width reproduced with ink without interruption.

(2) Printing durability As described above, after printing was performed in the evaluation of fine line reproducibility, printing was further continued. 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. Printing durability was evaluated by the number of printed sheets when the ink density (reflection density) was reduced by 0.1 from the start of printing.

(3) Dirtiness An exposed original plate similar to that described above was attached to a cylinder of a printing machine SOR-M manufactured by Heidelberg without developing. Dampening water (IF102 (Effect manufactured by Fuji Photo Film Co., Ltd.) / Water / = 4/96 (volume ratio)) and TRANS-G (N) Beni Ink (Dainippon Ink Chemical Co., Ltd.) / Varnish = 90/10 (mass ratio), and after supplying dampening water and ink, 500 sheets were printed at a printing speed of 6000 sheets per hour. After on-press development is completed, the fountain solution is squeezed, the plate surface is completely soiled with ink, and the fountain solution is supplied again until the ink is completely removed from the non-image area and a good print is obtained. The number of sheets was measured. The small number of sheets indicates that the printing plate has excellent hydrophilicity and water retention in the non-image area.
The evaluation results are shown in Table 3 below.

Examples 2-8
Lithographic printing in the same manner as in Example 1, except that the copolymer (A) and the copolymer (B) were changed to the copolymer (A) and the copolymer (B) shown in Table 1 below, respectively. An original plate was prepared. The obtained lithographic printing plate precursor was exposed, printed, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 below.

Comparative Example 1
A methanol solution (5) containing the copolymer (A) represented by the specific example (A16) (x / y / z = 20/20/60, mass average molecular weight 25000) on the support prepared in Example 1 (Mass% concentration) was applied and then oven-dried at 70 ° C. for 30 seconds to form an undercoat layer having a dry coating amount of 10 mg / m ² .
Subsequently, the above image recording layer coating solution (1) was bar-coated and then oven-dried at 70 ° C. for 60 seconds to form an image recording layer having a dry coating amount of 0.8 g / m ² to form a planographic printing plate precursor. Got. The obtained lithographic printing plate precursor was exposed, printed, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 below.

Comparative Example 2
A methanol solution (5) containing the copolymer (A) represented by the specific example (A13) (x / y / z = 20/10/70, mass average molecular weight 18000) on the support prepared in Example 1 (Mass% concentration) was applied and then oven-dried at 70 ° C. for 30 seconds to form an undercoat layer having a dry coating amount of 10 mg / m ² .
Subsequently, the above image recording layer coating solution (1) was bar-coated and then oven-dried at 70 ° C. for 60 seconds to form an image recording layer having a dry coating amount of 0.8 g / m ² to form a planographic printing plate precursor. Got. The obtained lithographic printing plate precursor was exposed, printed, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 below.

Example 9
On the support prepared in Example 1, the copolymer (A) represented by the specific example (A16) (x / y / z = 20/30/50, mass average molecular weight 25000) and the specific example (B12) 5% by mass methanol solution (copolymer (A) / copolymer (B) = 70/30 mass) containing a copolymer (B) (a / b = 20/80, mass average molecular weight 200,000) represented by Ratio) was oven-dried at 70 ° C. for 30 seconds to form an undercoat layer having a dry coating amount of 10 mg / m ² .
Subsequently, an image recording layer coating solution (2) having the following composition was applied to the bar 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. I got the original plate. The obtained lithographic printing plate precursor was exposed, printed, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 below.

Image recording layer coating solution (2)
・ The following infrared absorber (2) 0.05 g
・ 0.2 g of the above polymerization initiator (1)
・ The following binder polymer (1) 0.5 g
(Average molecular weight 80,000)
・ Polymerizable compound 1.0g
Isocyanuric acid EO-modified triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester M-315)
・ 0.1 g of the above-mentioned fluorosurfactant (1)
・ Methyl ethyl ketone 18.0g

Examples 10-15
Lithographic printing was carried out in the same manner as in Example 9 except that the copolymer (A) and the copolymer (B) were changed to the copolymer (A) and the copolymer (B) shown in Table 2 below, respectively. An original version for the plate was obtained. The obtained lithographic printing plate precursor was exposed, printed, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 below.

Comparative Example 3
A methanol solution (5) containing the copolymer (A) represented by the specific example (A16) (x / y / z = 20/30/50, mass average molecular weight 25000) on the support prepared in Example 1 (Mass% concentration) was applied and then oven-dried at 70 ° C. for 30 seconds to form an undercoat layer having a dry coating amount of 10 mg / m ² .
Subsequently, the above image recording layer coating solution (2) is bar-coated 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 to form a planographic printing plate precursor. Got. The obtained lithographic printing plate precursor was exposed, printed, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 below.

  From Table 3, it can be seen that the lithographic printing plate precursor of the present invention is excellent in on-press developability, fine line reproducibility, printing durability and stain resistance.

Claims (3)

It contains (A) an infrared absorber, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer on the support, and can be removed by printing ink, fountain solution or both. An undercoat layer provided between the support and the image recording layer, wherein the undercoat layer comprises at least (a1) a repeating unit containing at least one ethylenically unsaturated bond; and (a2) the support. A copolymer (A) having a repeating unit containing at least one functional group that interacts with the surface, (a3) a repeating unit containing at least one hydrophilic functional group, and at least (a2) a support surface A copolymer (B) having a repeating unit containing at least one functional group that interacts with (a3) a repeating unit containing at least one hydrophilic functional group ,
The repeating unit (a2) is represented by the following general formula (A2),

(In General Formula (A2), R _{1 to} R ₃ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen atom, and L represents —CO—, —O—, —NH—, Represents a divalent linking group selected from the group consisting of a divalent aliphatic group, a divalent aromatic group, and combinations thereof, Q is at least any one selected from a group represented by the following structures and a phosphonic acid group Represents.)

(In the above formula, R _{11 to} R ₁₃ each independently represents a hydrogen atom, an alkyl group, an aryl group, an alkynyl group, or an alkenyl group, and M ₁ and M ₂ each independently represent a hydrogen atom, a metal atom, or Represents an ammonium group, and X ⁻ represents a counter anion.)
The repeating unit (a3) is represented by the following general formula (A3),

(In General Formula (A3), R _{1 to} R ₃ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogen atom, and L represents —CO—, —O—, —NH—, And represents a divalent linking group selected from the group consisting of a divalent aliphatic group, a divalent aromatic group, and combinations thereof, and W represents at least one group selected from the following.

(Wherein, M ₁ is a hydrogen atom, a metal atom or an ammonium group, and R ₇ and R ₈ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, R ₉ represents a linear or branched alkylene group having 1 to 6 carbon atoms, and n represents an integer of 1 to 100.)
A lithographic printing plate precursor , wherein the copolymer (A) and the copolymer (B) are mixed at a ratio of 5 to 95% by mass of the copolymer (A) .   The lithographic plate according to claim 1, wherein the undercoat layer is provided by applying a coating solution prepared by mixing the copolymer (A) and the copolymer (B). A printing plate master. The lithographic printing plate precursor according to claim 1 or 2 is mounted on a printing press and imagewise exposed with an infrared laser, or imagewise exposed with an infrared laser and then mounted on a printing press. A lithographic printing method, wherein printing ink and fountain solution are supplied to a printing plate precursor to remove an infrared unexposed portion of the image recording layer and printing is performed .