WO2016047336A1 - Lithographic printing plate precursor and process for producing same - Google Patents

Abstract

Provided is a lithographic printing plate precursor which comprises a hydrophilic support and, formed thereon, an image recording layer comprising (A) a radical-polymerizable compound, (B) an infrared-absorbing dye, (C) a free-radical polymerization initiator, and (D) a microgel, wherein the microgel (D) is a product of the reaction of (1) a compound having at least two active-hydrogen-containing groups and at least one C_2-12 alkyleneoxy group with (2) a polyfunctional isocyanate compound. The lithographic printing plate precursor retains satisfactory on-press developability and printing durability and has excellent tone reproducibility. Also provided is a process for producing the lithographic printing plate precursor.

Description

Planographic printing plate precursor and plate making method

The present invention is a lithographic printing plate precursor capable of direct plate making using various lasers from a digital signal such as a computer, and a so-called lithographic printing plate precursor and its plate making method, in particular, while maintaining good on-press developability and printing durability, The present invention relates to a lithographic printing plate precursor excellent in tone reproducibility and a plate making method thereof.

Currently, lithographic printing plates are made using CTP (computer-to-plate) technology. That is, a lithographic printing plate can be obtained by scanning and exposing a lithographic printing plate precursor directly using a laser or a laser diode without using a lith film and developing it. Accordingly, one problem related to the lithographic printing plate precursor is improvement of image forming characteristics, printing characteristics, physical characteristics and the like corresponding to the CTP technology.

On the other hand, due to growing interest in the global environment, environmental issues related to waste liquids associated with wet processing such as development processing have been highlighted as another issue related to lithographic printing plate precursors.

In response to the environmental issues described above, development or plate making is simplified or eliminated. As one simple plate-making method, a method called “on-press development” is performed. That is, a method of removing an unnecessary portion (non-image portion) of an image recording layer in an initial stage of a normal printing process without exposing to a conventional development process after exposing a lithographic printing plate precursor and mounting it in a printing machine as it is. It is.

On-press development has very low development ability compared to conventional development processing, and it is difficult to satisfy both on-press developability and other characteristics, particularly printing durability. Various proposals have been made to solve this problem.

For example, Patent Document 1 discloses that (1) at least one group having an active hydrogen atom, and further an ionic hydrophilic group in order to improve developability after aging while maintaining high printing durability. Obtained by reaction with a compound having one or two, (2) a compound having at least one group having an active hydrogen atom and not having an ionic hydrophilic group, and (3) a polyfunctional isocyanate compound A lithographic printing plate precursor containing a microgel in an image recording layer is described.

Japanese Unexamined Patent Publication No. 2013-52515

However, in the technique described in Patent Document 1, there is a case where there is a problem that the tone reproducibility of the halftone image is lowered when the sensitivity of the polymerization initiation system is increased in order to obtain high printing durability. I understand. This is because, as the sensitivity is increased, polymerization of the non-image area (very low exposure area) close to the image area proceeds and cannot be sufficiently removed by on-machine development, resulting in a halftone dot thicker than the desired halftone image. It is thought that it is because it is formed. Thus, it has been difficult for the conventional technology to achieve both high printing durability and good tone reproducibility.

An object of the present invention is to provide a lithographic printing plate precursor excellent in tone reproducibility and a plate making method thereof while maintaining good on-press developability and printing durability.

1. A lithographic printing plate precursor having an image recording layer containing (A) a radical polymerizable compound, (B) an infrared absorbing dye, (C) a radical polymerization initiator, and (D) a microgel on a hydrophilic support. (D) a compound in which the microgel has (1) at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms, and (2) a polyfunctional isocyanate compound A lithographic printing plate precursor which is a reaction product of
2. (D) the microgel (1) a compound having at least two groups having an active hydrogen atom and at least one alkyleneoxy group having 2 to 12 carbon atoms, (2) a polyfunctional isocyanate compound, and (3) A reaction product of a compound other than the above (1) having at least one active hydrogen atom. The lithographic printing plate precursor described in 1.
3. (1) The compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms is a polyfunctional amine, polyfunctional alcohol, polyfunctional phenol and polyfunctional 1. at least one compound selected from thiols; Or 2. The lithographic printing plate precursor described in 1.
4). (3) The compound other than the above (1) having at least one active hydrogen atom is at least one compound selected from water, polyfunctional amines, polyfunctional alcohols, polyfunctional phenols and polyfunctional thiols. Or 3. The lithographic printing plate precursor described in 1.
5. (1) The compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms has at least two groups having active hydrogen atoms, and 1. A compound having at least two alkyleneoxy groups having 2 to 12 carbon atoms. ~ 4. The lithographic printing plate precursor as described in any one of the above.
6). 1. The image recording layer contains (E) a compound having an electron donating ability. ~ 5. The lithographic printing plate precursor as described in any one of the above.
7). 5. The compound (E) having an electron donating ability is an alkyl or aryl art complex compound or an N-arylalkylamine compound. The lithographic printing plate precursor described in 1.
8). 1. A protective layer is provided on the image recording layer. ~ 7. The lithographic printing plate precursor as described in any one of the above.
9. 1. The unexposed portion of the image recording layer can be removed with at least one of dampening water and printing ink. ~ 8. The lithographic printing plate precursor as described in any one of the above.
10.9. The lithographic printing plate precursor described in 1) is subjected to image exposure with an infrared laser, and the unexposed portion of the image recording layer is removed on the printing machine with at least one of dampening water and printing ink.

According to the present invention, it is possible to provide a planographic printing plate precursor excellent in tone reproducibility and a plate making method thereof while maintaining good on-press developability and printing durability.

Hereinafter, the present invention will be described in detail.

[Lithographic printing plate precursor]
The lithographic printing plate precursor according to the present invention comprises an image recording containing (A) a radical polymerizable compound, (B) an infrared absorbing dye, (C) a radical polymerization initiator, and (D) a microgel on a hydrophilic support. And (D) the microgel has (1) a compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms, and (2) It is a reaction product of a polyfunctional isocyanate compound. In the lithographic printing plate precursor according to the invention, an undercoat layer can be provided between the support and the image recording layer, and a protective layer can be provided on the image recording layer, if necessary.

The lithographic printing plate precursor according to the invention comprises (1) a compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms in the image recording layer, and (2) By containing a microgel which is a reaction product of a polyfunctional isocyanate compound, excellent tone reproducibility can be expressed while maintaining good on-press developability and printing durability.
The mechanism of action that provides such excellent characteristics is not necessarily clear, but is considered as follows. That is, the microgel according to the present invention has an alkyleneoxy group in the wall structure of the microgel, whereby the particle strength is reduced due to the decrease in the glass transition temperature of the microgel itself, and at the same time, the affinity for the ink is improved. As a result, the on-press developability is improved, and the on-press development progresses well even in the extremely low exposure region of the non-image area, thereby suppressing dot thickening. On the other hand, in the image portion, due to the decrease in the glass transition temperature, the polymerization efficiency of the radical polymerizable compound is improved, whereby the image strength is improved and high printing durability is achieved.

Hereinafter, components of the planographic printing plate precursor according to the present invention will be described in detail.

(Image recording layer)
The image recording layer of the lithographic printing plate precursor according to the invention contains (A) a radical polymerizable compound, (B) an infrared absorbing dye, (C) a radical polymerization initiator, and (D) a microgel.

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

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

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

Also suitable are urethane-based addition-polymerizable compounds produced using an addition reaction of isocyanate and hydroxyl group. Specific examples include, for example, two or more per molecule described in JP-B-48-41708. And a vinyl urethane 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 the polyisocyanate compound having the above isocyanate group. It is done.
^{_{CH 2 = C (R 4)}} COOCH 2 CH (R 5) OH formula (A)
(However, R ⁴ and R ⁵ represent H or CH _3. )

Also, urethanes as described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-2003-344997, JP-A-2006-65210 are disclosed. Acrylates, JP-B 58-49860, JP-B 56-17654, JP-B 62-39417, JP-B 62-39418, JP-A 2000-250211, JP-A 2007-94138 Urethane compounds having an ethylene oxide-based skeleton described in Japanese Patent Publication No. 7153632, hydrophilic groups described in US Pat. No. 7,153,632, JP-T 8-505958, JP-A 2007-293221, and JP-A 2007-293223. Also suitable are urethane compounds having.

Among the above compounds, tris (acryloyloxyethyl) isocyanurate, bis (acryloyloxyethyl) hydroxyethyl isocyanurate, etc. from the point of excellent balance between the hydrophilicity involved in on-press developability and the polymerization ability involved in printing durability The isocyanuric acid ethylene oxide modified acrylates are particularly preferred.

Details of the usage method such as the structure of the radical polymerizable compound, whether it is used alone or in combination, and the amount added can be arbitrarily set according to the performance design of the final lithographic printing plate precursor. The content of the radical polymerizable compound is preferably 0.5 to 75% by mass, more preferably 1 to 70% by mass, based on the total solid content of the image recording layer.

(B) Infrared absorbing dye The infrared absorbing dye used in the image recording layer has a function of converting absorbed infrared light into heat and a function of being excited by infrared light to transfer electrons or energy to a radical polymerization initiator. As a result, radicals are generated, and a cured image is formed by initiating and promoting the polymerization reaction of the radical polymerizable compound. The infrared absorbing dye preferably has an absorption maximum in a wavelength region of 760 to 1200 nm.

As the infrared absorbing dye, commercially available dyes and known dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes Is mentioned.

Preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further, cyanine dyes and indolenine cyanine dyes are preferred, and particularly preferred examples include cyanine dyes represented by the following general formula (II).

In the general formula (II), R ¹⁷ represents a hydrogen atom, a halogen atom, —OR ²⁶ , —N (R ²⁷ ) (R ²⁸ ) or —SR ²⁹ . R ²⁶ and R ²⁹ each independently represent a hydrocarbon group, an aryl group, a heteroaryl group, or a hydrocarbon group having 1 to 12 carbon atoms including a hetero atom. R ²⁷ and R ²⁸ each independently represent a hydrogen atom, an alkyl group or an aryl group, or R ²⁷ and R ²⁸ may be linked to each other to form a ring. R ¹⁸ and R ¹⁹ each independently represent a hydrogen atom or an alkyl group, or R ¹⁸ and R ¹⁹ may be linked to each other to form a ring. Ar ¹ and Ar ² each independently represents an atomic group necessary for forming an aromatic ring or a heterocyclic ring. Y ¹ and Y ² each independently represents —NR ³⁰ —, —S—, —O—, —C═C— or a dialkylmethylene group. R ²⁰ and R ²¹ each independently represent a hydrocarbon group. R ²² , R ²³ , R ²⁴ , R ²⁵ , and R ³⁰ each independently represent a hydrogen atom or a hydrocarbon group. Za represents a counter ion that neutralizes the charge.

The cyanine dye represented by formula (II) will be described in more detail. R ¹⁷ is preferably a hydrogen atom, a halogen atom or —N (R ²⁷ ) (R ²⁸ ), particularly preferably a halogen atom.

R ²⁷ and R ²⁸ may be the same or different, preferably an aryl group having 6 to 10 carbon atoms which may have a substituent, or 1 to carbon atoms which may have a substituent. 8 represents an alkyl group or a hydrogen atom, and R ²⁷ and R ²⁸ may be linked to each other to form a ring. Of these, a phenyl group is preferred (—NPh ₂ ). R ²⁶ and R ²⁹ are preferably a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent, an aryl group which may have a substituent, and a substituent. A heteroaryl group, a hydrocarbon group having 1 to 12 carbon atoms containing a hetero atom; Here, a hetero atom shows a nitrogen atom, a sulfur atom, an oxygen atom, a halogen atom, and a selenium atom. Of these, an aryl group (for example, phenyl group) which may have a substituent and a heteroaryl group (for example, tetrazolyl group) which may have a substituent are preferable.

R ¹⁸ and R ¹⁹ each independently preferably represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms. From the viewpoint of storage stability of the coating solution for the image recording layer, R ¹⁸ and R ¹⁹ are preferably hydrocarbon groups having 2 or more carbon atoms. R ¹⁸ and R ¹⁹ may be connected to each other to form a ring, and in the case of forming a ring, it is particularly preferable to form a 5-membered ring or a 6-membered ring.

Ar ¹ and Ar ² may be the same or different and each represents an atomic group necessary for forming an aromatic ring or a heterocyclic ring which may have a substituent. A preferable aromatic ring or heterocyclic ring includes a benzene ring or a naphthalene ring. Preferred examples of the substituent include a hydrocarbon group having 12 or less carbon atoms, a halogen atom, and an alkoxy group having 12 or less carbon atoms. Y ¹ and Y ² may be the same as or different from each other, and preferably represent —NR ³⁰ —, —S—, —O—, —C═C— or a dialkylmethylene group having 12 or less carbon atoms, R ³⁰ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms. R ²⁰ and R ²¹ may be the same or different, and each preferably represents a hydrocarbon group having 20 or less carbon atoms, which may have a substituent. Preferred substituents include an alkoxy group having 12 or less carbon atoms, an acyl group, a carboxy group, and a sulfo group.

R ²² , R ²³ , R ²⁴ and R ²⁵ may be the same or different, and preferably represent a hydrogen atom or a hydrocarbon group having 12 or less carbon atoms. In view of easy availability of the raw material, a hydrogen atom is preferred. Za ⁻ represents a counter anion that neutralizes the charge. When the cyanine dye represented by the general formula (II) has an anionic substituent in the structure thereof, and charge neutralization is not necessary. Za ^- is not necessary. Za ⁻ is preferably a halide ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, or a sulfonate ion from the viewpoint of the storage stability of the coating solution for the image recording layer. A phosphate ion and an aryl sulfonate ion are more preferable.

Specific examples of the cyanine dye represented by the general formula (II) include compounds described in paragraph numbers [0017] to [0019] of JP-A No. 2001-133969, and paragraph numbers of JP-A No. 2002-023360. 0016] to [0021], compounds described in paragraphs [0012] to [0037] of JP-A No. 2002-040638, preferably paragraphs [0034] to [0041] of JP-A No. 2002-278057, The compounds described in paragraph Nos. [0080] to [0086] of Kaikai 2008-195018, particularly preferably the compounds described in paragraph Nos. [0035] to [0043] of JP-A-2007-90850 are exemplified.

Specific examples of the infrared absorbing dye used in the present invention are shown below, but the present invention is not limited thereto.

Infrared absorbing dyes may be used alone or in combination of two or more. Moreover, you may use together with infrared absorbers other than infrared absorbing dyes, such as a pigment. As the pigment, compounds described in paragraph numbers [0072] to [0076] of JP-A-2008-195018 are preferable.

The content of the infrared absorbing dye is preferably 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, and particularly preferably 0.15 to 10% by mass with respect to the total solid content of the image recording layer. It is.

(C) Radical polymerization initiator The radical polymerization initiator used in the image recording layer is a compound which generates radicals by energy of light, heat or both, and initiates and accelerates polymerization of the radical polymerizable compound. Examples of the radical polymerization initiator include (a) an organic halide, (b) a carbonyl compound, (c) an azo compound, (d) an organic peroxide, (e) a metallocene compound, (f) an azide compound, (g ) Hexaarylbiimidazole compounds, (h) disulfone compounds, (i) oxime ester compounds, and (j) onium salt compounds. As the radical polymerization initiator, (j) onium salt compounds are preferably used.

(J) Examples of the onium salt compound include European Patent Nos. 104 and 143, US Patent Application Publication Nos. 2008/0311520, JP-A-2-150848, JP-A-2008-195018, and J . V. Ivonium salts described in Crivello et al, Macromolecules, 10 (6), 1307 (1977), European Patent Nos. 370,693, 233,567, 297,443, 297,442, US Patent No. 4,933,377, 4,760,013, 4,734,444, 2,833,827, German Patents 2,904,626, 3,604,580, Examples thereof include onium salts such as sulfonium salts described in each specification of No. 3,604,581.

As the onium salt, an onium salt having a cyanine structure as shown below is also preferably used.

Of the onium salts, iodonium salts are preferred. As the iodonium salt, a diphenyl iodonium salt is preferable, a diphenyl iodonium salt substituted with an electron donating group such as an alkyl group or an alkoxyl group is more preferable, and an asymmetric diphenyl iodonium salt is further preferable. Specific examples of iodonium salts include diphenyliodonium = hexafluorophosphate, 4-methoxyphenyl-4- (2-methylpropyl) phenyliodonium = hexafluorophosphate, 4- (2-methylpropyl) phenyl-p-tolyl. Iodonium = hexafluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium = tetrafluoroborate, 4 -Octyloxyphenyl-2,4,6-trimethoxyphenyliodonium = 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophos Ato, bis (4-t- butylphenyl) iodonium but tetraphenylborate and the like, and the present invention is not limited thereto.

The content of the radical polymerization initiator is preferably 7 to 75% by mass, more preferably 10 to 70% by mass, and particularly preferably 15 to 60% by mass with respect to the total solid content of the image recording layer.

(D) Microgel The microgel used for the image recording layer (hereinafter also referred to as microgel (D)) is (1) an alkyleneoxy group having at least two groups having active hydrogen atoms and having 2 to 12 carbon atoms. And (2) a reaction product obtained by reaction of a polyfunctional isocyanate compound.

(1) A compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms, having at least two groups having active hydrogen atoms, and having the number of carbon atoms The group having an active hydrogen atom in a compound having at least one alkyleneoxy group of 2 to 12 (hereinafter also referred to as compound (1)) means a group having a hydrogen atom on an oxygen atom, a nitrogen atom or a sulfur atom. .
Specific examples include a hydroxy group having a hydrogen atom on an oxygen atom, an amino group having a hydrogen atom on a nitrogen atom, and a mercapto group having a hydrogen atom on a sulfur atom. Among these, a hydroxy group and an amino group are preferable, and a hydroxy group is particularly preferable.

The compound (1) is characterized by having at least two groups having active hydrogen atoms in the molecule. By reacting compound (1) having at least two groups having active hydrogen atoms with (2) polyfunctional isocyanate compound, the alkyleneoxy group contained in compound (1) is a reaction product in the wall structure of the microgel. Incorporated into. Accordingly, it is considered that the microgel (D) according to the present invention greatly contributes to the expression of the excellent effect of the present invention. On the other hand, in the microgel similarly produced using the compound having one active hydrogen atom group instead of the compound (1), the alkyleneoxy group is suspended from the surface of the microgel particle wall. The excellent effect of the present invention is not exhibited because of the presence of
The number of groups having an active hydrogen atom in the compound (1) is preferably 2 to 6, more preferably 3 to 5.

The alkyleneoxy group having 2 to 12 carbon atoms in the compound (1) is a group in which an alkylene group having 2 to 12 carbon atoms and an oxygen atom are bonded.
The alkyleneoxy group having 2 to 12 carbon atoms includes, for example, structures represented by the following general formulas (1-1) to (1-3).

In general formulas (1-1) to (1-3), R ¹ represents a hydrogen atom or an alkyl group, respectively. A plurality of R ¹ may be the same or different. n, m and l each represents an integer of 1 or more.

In the general formulas (1-1) to (1-3), the alkyl group represented by R ¹ is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, and a carbon number of 1 More preferred are alkyl groups of ˜5.
Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.
Of the alkyl groups, a methyl group, an ethyl group, and a propyl group are particularly preferable.

In the general formulas (1-1) to (1-3), n, m and l are each preferably 1 to 25, more preferably 1 to 20, and still more preferably 1 to 15.

The alkyleneoxy group having 2 to 12 carbon atoms is preferably an alkyleneoxy group represented by the general formula (1-1), (1-2) or (1-3). The alkyleneoxy group represented is more preferable. In particular, an ethyleneoxy group and a propyleneoxy group are preferable.

The compound (1) is also characterized by having at least one alkyleneoxy group having 2 to 12 carbon atoms in the molecule. By including an alkyleneoxy group having 2 to 12 carbon atoms, excellent tone reproducibility can be obtained while maintaining printing durability.
The number of alkyleneoxy groups having 2 to 12 carbon atoms in the compound (1) is preferably 2 or more. The upper limit of the number of alkyleneoxy groups having 2 to 12 carbon atoms is suitably about 40.

Specifically, the compound (1) includes a polyol compound having a plurality of hydroxy groups (polyfunctional alcohol, polyfunctional phenol, etc.), a polyamine compound having a plurality of amino groups (polyfunctional amine), and a plurality of mercapto groups. It is preferably at least one compound selected from polythiol compounds (polyfunctional thiol) having a structure containing at least one alkyleneoxy group having 2 to 12 carbon atoms. Compound (1) may further have a substituent.
As for compound (1), only 1 type may be used and 2 or more types may be used together.

Specific examples of the compound (1) are shown below, but the present invention is not limited thereto. In Table 2 below, “2.5” of “n number” in compound “AO-32” means that compound “AO-32” is an equimolar mixture of n number 2 and 3.

Compound (1) can be synthesized using a known method. Commercial products can also be used. For example, TMP-30, TMP-60, TMP-90, PNT-60U manufactured by Nippon Emulsifier Co., Ltd. are preferably used.

(2) Polyfunctional isocyanate compound The polyfunctional isocyanate compound is a compound having at least two isocyanate groups in the molecule. Specific examples include a bifunctional isocyanate compound having two isocyanate groups in the molecule and a trifunctional or more isocyanate compound having three or more isocyanate groups in the molecule. The number of isocyanate groups in the polyfunctional isocyanate compound is preferably 2 to 6, more preferably 2 to 5, and particularly preferably 2 to 4.

Examples of bifunctional isocyanate compounds include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4′- Diisocyanate, 3,3'-dimethoxy-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, 4-chloroxylylene-1 , 3-diisocyanate, 2-methylxylylene-1,3-diisocyanate, 4,4'-diphenylpropane diisocyanate, 4,4'-diphenylhexafluoropropane diisocyanate, trimethylene diisocyanate Cyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, dicyclohexyl Examples include methane-4,4′-diisocyanate, 1,4-bis (isocyanatemethyl) cyclohexane, 1,3-bis (isocyanatemethyl) cyclohexane, isophorone diisocyanate, and lysine diisocyanate.

Examples of the trifunctional or higher functional isocyanate compounds include those trimers (burette or isocyanurate) mainly composed of the above bifunctional isocyanate compounds, adducts of polyols such as trimethylolpropane and bifunctional isocyanate compounds. Examples include functionalized compounds, formalin condensates of benzene isocyanate, polymers of isocyanate compounds having a polymerizable group such as methacryloyloxyethyl isocyanate, and lysine triisocyanate. In particular, xylene diisocyanate and hydrogenated product thereof, hexamethylene diisocyanate, tolylene diisocyanate and hydrogenated product thereof, these trimers (burette or isosinurate), and polyfunctional as adducts with trimethylolpropane. Is preferred. These compounds are described in “Polyurethane Resin Handbook” (edited by Keiji Iwata, published by Nikkan Kogyo Shimbun (1987)).

Among the polyfunctional isocyanate compounds, diphenylmethane-4,4′-diisocyanate, xylylene-1,3-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, hexamethylene diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene 1,4-diisocyanate, 1,4-bis (isocyanatemethyl) cyclohexane, 1,3-bis (isocyanatemethyl) cyclohexane, isophorone diisocyanate, lysine diisocyanate are preferred, cyclohexylene-1,4-diisocyanate, 1,4- Bis (isocyanatemethyl) cyclohexane, 1,3-bis (isocyanatemethyl) cyclohexane, isophorone diisocyanate, and lysine diisocyanate are more preferable. 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate is particularly preferred.
Only one type of polyfunctional isocyanate compound may be used, or two or more types may be used in combination.

The polyfunctional isocyanate compound can be synthesized using a known method. For example, trimethylolethane and 4-fold moles of isophorone diisocyanate are heated in an organic solvent with stirring (50 to 100 ° C.) or at a relatively low temperature (40 ° C. while adding a catalyst such as stannous octylate). To 70 ° C.).
Examples of the organic solvent used include ethyl acetate, chloroform, tetrahydrofuran, methyl ethyl ketone, acetone, acetonitrile, toluene and the like.

The polyfunctional isocyanate compound is dibutylureated with dibutylamine according to a conventional method, and the molecular weight (polystyrene conversion value by gel permeation chromatography (GPC) method) is measured. The weight average molecular weight (Mw) of the polyfunctional isocyanate compound is preferably 1000 to 40000, particularly preferably 2000 to 30000.

There are many commercially available polyfunctional isocyanate compounds, and these can also be used.

The (D) microgel (microgel (D)) used for the image recording layer has (1) at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms. In addition to the compound and (2) the polyfunctional isocyanate compound, (3) a reaction product obtained by reaction of a compound other than the above (1) having at least one active hydrogen atom may be used.

The compound other than the above (1) having at least one active hydrogen atom (hereinafter also referred to as the compound (3)) may be a compound that forms a microgel by reacting with the (2) polyfunctional isocyanate compound together with the compound (1). That's fine. Specifically, water, a compound having two or more hydroxy groups, a compound having two or more amino groups, a compound having two or more mercapto groups, and the like are used. In general, water is preferably used as the compound (3). Polyols (such as polyfunctional alcohols and polyfunctional phenols), polyamines (polyfunctional amines), and polythiols (polyfunctional thiols) are preferably used. Specific examples include propylene glycol, glycerin, trimethylolpropane, bis (hexamethylene) triamine, ethylenediamine, diethylenetriamine, pentaerythritol tetra (3-mercaptopropionate) and the like. Only 1 type may be used for a compound (3) and it may use 2 or more types together.

The microgel (D) is manufactured by preparing an oil phase component and an aqueous phase component and mixing them to produce an emulsified dispersion and performing a known operation applied to a general method for producing fine polymer particles. Can do. The production method is described in detail in, for example, “Microcapsule” (Kondo Asahi, Nikkan Kogyo Shimbun (1970)) and “Microcapsule” (Kondo Yasu et al., Sankyo Publishing (1977)).

Specifically, compounds (1) and (2) a polyfunctional isocyanate compound, or an adduct of compound (1) and (2) polyfunctional isocyanate compound, and an oil phase component containing at least an organic solvent, and at least water An aqueous dispersion of microgel (D) can be obtained by mixing the aqueous phase components to be contained, emulsifying and dispersing using an emulsifying device such as a homogenizer, and removing the organic solvent from the oil droplets of the emulsified dispersion by heating or the like. . In the case of using the compound (3), an aqueous dispersion of the microgel (D) can be obtained by adding the compound (3) to the aqueous phase component and performing the same operation. The adduct of compound (1) and (2) polyfunctional isocyanate compound can be easily produced by reacting compound (1) and (2) polyfunctional isocyanate compound by a conventional method. The method using an adduct is preferable from the viewpoint of reproducibility and production stability because the control of the microgel wall structure is easy.

The organic solvent used for the oil phase component is an organic solvent that dissolves the compound (1), (2) polyfunctional isocyanate compound and other components used as necessary, and is not miscible with water. Any organic solvent that can be removed from the oil droplets by any means can be used without particular limitation. Specifically, hydrocarbon solvents, aromatic solvents, ketone solvents, ester solvents, ether solvents and the like are preferably used. For example, ethyl acetate, butyl acetate, methyl ethyl ketone, diethyl ether, diisopropyl ether, methyl tertiary butyl ether and the like are preferable, and ethyl acetate and methyl ethyl ketone are more preferable.

In the preparation of the emulsified dispersion, the mixture of the oil phase component and the aqueous phase component is vigorously stirred, for example, at 12,000 rpm for 10 to 15 minutes using an emulsifying dispersion device such as a homogenizer. An emulsified dispersion in which oil droplets are emulsified and dispersed is obtained. Subsequently, the obtained emulsified dispersion is heated and stirred to evaporate the organic solvent, thereby obtaining the desired aqueous dispersion of the microgel (D).

The ratio of (2) polyfunctional isocyanate compound and compound (1) (the total amount of compound (1) and compound (3) when compound (3) is also used) at the time of producing the microgel (D) is the mass ratio. It is preferably 59: 1 to 5: 1.

The amount of the compound (1) added is preferably 0.01 to 30% by mass, more preferably 0.1 to 20% by mass, and particularly preferably 0.1% by mass, based on the total solid content at the time of producing the microgel. 1 to 10% by mass.

(2) The content of the polyfunctional isocyanate compound is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and particularly preferably 20 to 50% by mass with respect to the total solid content at the time of microgel production. .

The amount of compound (3) added is preferably 0.01 to 30% by mass, more preferably 0.1 to 20% by mass, and particularly preferably 0.1% by mass, based on the total solid content at the time of microgel production. 1 to 10% by mass.

In the production of the microgel (D), in addition to the above components, a dispersant, a polymerizable compound, a surfactant and the like may be used. A dispersant, a polymerizable compound, and a surfactant are appropriately added to the oil phase component and / or the water phase component depending on the solubility thereof.

(Dispersant)
A hydrophilic polymer is preferably used as the dispersant. Examples of the hydrophilic polymer include a compound having a polyoxyalkylene chain, polyvinyl alcohol and a modified product thereof, polyacrylic acid amide and a derivative thereof, ethylene / vinyl acetate copolymer, styrene / maleic anhydride copolymer, ethylene / Maleic anhydride copolymer, isobutylene / maleic anhydride copolymer, polyvinylpyrrolidone, ethylene / acrylic acid copolymer, vinyl acetate / acrylic acid copolymer, carboxymethylcellulose, methylcellulose, casein, gelatin, starch derivative, gum arabic And sodium alginate. The hydrophilic polymer is preferably a compound which does not react with (2) a compound having a polyfunctional isocyanate group or is extremely difficult to react. For example, those having a reactive amino group in the molecular chain, such as gelatin, need to have no reactivity in advance. Among the hydrophilic polymers, compounds having a polyoxyalkylene chain are preferred.

Since the hydrophilic polymer functions as a protective colloid for the microgel (D), the use of the hydrophilic polymer is preferable from the viewpoint of improving the dispersion stability of the microgel (D) and improving the developability of the lithographic printing plate precursor.

The amount of the dispersant added is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, and particularly preferably 1 to 30% by mass with respect to the total solid content of the oil phase component.

(Polymerizable compound)
Examples of the polymerizable compound include a compound having an ethylenically unsaturated group and a compound having an epoxy group. A compound having an ethylenically unsaturated group having a relatively high photopolymerization rate is preferred. The polymerizable compound contributes to further improving the printing durability of the lithographic printing plate. For example, when a polymerizable compound having a hydroxy group is used, the polymerizable group is introduced into the wall structure of the microgel, and as a result of radical polymerization reaction induced by image exposure, the strength between the microgel and the image recording layer matrix is increased. This is thought to be due to the improvement. A polymeric compound may be used independently or may use 2 or more types together. When a polymerizable compound is used, the addition amount thereof is preferably 1 to 80% by mass, more preferably 5 to 70% by mass, and particularly preferably 10 to 60% by mass with respect to the total solid content of the oil phase component.

Specific examples of the polymerizable compound are shown below, but the present invention is not limited thereto.

(Surfactant)
In order to improve the stability of the emulsified dispersion, it is preferable to use a surfactant. The surfactant may be added to either the oil phase component or the water phase component, but is usually easier to add to the water phase component because of its low solubility in organic solvents. The amount added is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, based on the total solid content of the oil phase component. In general, surfactants used for emulsification and dispersion are considered to be excellent surfactants having a relatively long-chain hydrophobic group. For example, “Surfactant Handbook” (Nishiichiro et al., Published in industrial books (1980)). ), Specifically, alkali metal salts such as alkylsulfonic acid and alkylbenzenesulfonic acid can be used.

Also, as the surfactant (emulsification aid), a formalin condensate of aromatic sulfonate or a formalin condensate of aromatic carboxylate can be used. Specific examples include compounds represented by the following general formula (W-1) described in JP-A-06-297856.

In the general formula (W-1), R represents an alkyl group having a carbon number of 1 ~ 4, X is SO ₃ ^- or COO ^- represents, M represents Na ⁺ or ^{K +,} q is 1 to 20 Represents an integer.

Furthermore, alkyl glucoside compounds can also be used. Specifically, a compound represented by the following general formula (W-2) can be given.

In general formula (W-2), R represents an alkyl group having 4 to 18 carbon atoms, and q represents an integer of 0 to 2.

Surfactants may be used alone or in combination of two or more. The addition amount of the surfactant is preferably 0.01 to 5.0% by mass, more preferably 0.01 to 4.0% by mass, based on the total solid content of the oil phase component, and 0.05 to 3.0%. Mass% is particularly preferred.

The microgel (D) used in the present invention is a reaction product of the compounds (1) and (2) polyfunctional isocyanate compounds and is a fine particle composed of a urethane bond or a polymer having a urethane bond and a urea bond. The microgel (D) may have a capsule structure having a urethane bond or a polymer having a urethane bond and a urea bond as a wall. For example, the form of the microcapsule which includes the component of an image recording layer, for example, a radically polymerizable compound, is mentioned.

The average particle size of the microgel (D) is preferably from 0.01 to 3.0 μm, more preferably from 0.05 to 2.0 μm, from the viewpoints of the effects of the present invention and good resolution and stability over time. 10 to 1.0 μm is particularly preferable. The average particle diameter of the microgel (D) can be measured by a light scattering method.

Specific examples of the microgel (D) used in the present invention are shown below by the compound (1), (2) polyfunctional isocyanate compound, and compound (3) used in the production, but the present invention is limited to this. It is not something.

(2) The structures of polyfunctional isocyanate compounds NCO-1 to NCO-4 are shown below.

(E) Compound having electron donating ability The image recording layer of the lithographic printing plate precursor according to the invention preferably further contains (E) a compound having electron donating ability. The compound having an electron donating ability is a compound that can donate electrons to the (B) infrared absorbing dye excited by exposure, and decomposes to generate radicals after electron donation. Therefore, radical reactivity is improved and the strength of the image area is increased, which contributes to improvement in printing durability.

The compound having an electron donating ability is preferably a compound that can decompose itself and generate a radical after electron donation, and examples thereof include the following (i) to (v).

(I) Alkyl or aryl art complex: It is considered that an active radical is generated by oxidative cleavage of a carbon-hetero bond. Specifically, a borate compound is preferably used.

(Ii) N-arylalkylamine compound: It is considered that the C—X bond on carbon adjacent to nitrogen is cleaved by oxidation to generate an active radical. X is preferably a hydrogen atom, a carboxyl group, a trimethylsilyl group, a benzyl group or the like. Specifically, for example, N-phenylglycines (which may or may not have a substituent on the phenyl group), N-phenyliminodiacetic acid (which may or may not have a substituent on the phenyl group) May be included).

(Iii) Sulfur-containing compound: A compound in which the nitrogen atom of the amine compound is replaced with a sulfur atom can generate an active radical by the same action. For example, phenylthioacetic acid (the phenyl group may or may not have a substituent).
(Iv) Tin-containing compound: A compound in which the nitrogen atom of the amine is replaced with a tin atom can generate an active radical by the same action.
(V) Sulfinic acid salts: An active radical can be generated by oxidation. Specific examples include arylsulfin sodium.

Of these, (i) alkyl or aryl art complexes and (ii) N-arylalkylamine compounds are preferred, and (i) alkyl or aryl art complexes are particularly preferred. (I) Of the alkyl or aryl art complexes, borate compounds are preferred.

As the borate compound, for example, compounds described in paragraph No. [0028] of JP-A-2008-195018 are preferably used.

Specific examples of the borate compound include tetraphenylborate salt, tetratolylborate salt, tetrakis (4-methoxyphenyl) borate salt, tetrakis (pentafluorophenyl) borate salt, tetrakis (3,5-bis (trifluoromethyl) phenyl ) Borate salt, tetrakis (4-chlorophenyl) borate salt, tetrakis (4-fluorophenyl) borate salt, tetrakis (2-thienyl) borate salt, tetrakis (4-phenylphenyl) borate salt, tetrakis (4-t-butylphenyl) ) Borate salt, ethyl triphenyl borate salt, butyl triphenyl borate salt and the like. Examples of the counter cation of the borate compound include known cations such as alkali metal cations, alkaline earth metal cations, ammonium cations, phosphonium cations, sulfonium cations, iodonium cations, diazonium cations, and azinium cations. From the viewpoint of printing durability, tone reproducibility, and stability over time, a tetraphenylborate salt is particularly preferable.

(Binder polymer)
The image recording layer preferably contains a binder polymer in order to impart film properties. A conventionally well-known thing can be used for a binder polymer as long as it can provide film property. The binder polymer may be a linear binder polymer or a star structure polymer as described in JP-A-2007-249036.
In the image recording layer, it is preferable to use a binder polymer corresponding to the developing method.

As the binder polymer used in the image recording layer of the on-press development type lithographic printing plate precursor, a binder polymer having an alkylene oxide group is preferable.

The binder polymer having an alkylene oxide group used in the image recording layer may have a poly (alkylene oxide) moiety in the main chain or a side chain, and may have a poly (alkylene oxide) moiety. The graft polymer in the side chain may be a block copolymer composed of a block composed of a poly (alkylene oxide) -containing repeating unit and a block composed of a (alkylene oxide) -free repeating unit.

When a poly (alkylene oxide) moiety is present in the main chain, a polyurethane resin is preferred. When having a poly (alkylene oxide) moiety in the side chain, the main chain polymer is acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, methacrylic resin, polystyrene resin, novolac type A phenol resin, a polyester resin, a synthetic rubber, and a natural rubber are exemplified, and an acrylic resin is particularly preferable.

The alkylene oxide at the poly (alkylene oxide) moiety is preferably an alkylene oxide having 2 to 6 carbon atoms, and particularly preferably ethylene oxide or propylene oxide.
The number of repeating alkylene oxides at the poly (alkylene oxide) site is suitably 2 to 120, preferably 2 to 70, more preferably 2 to 50.
If the number of alkylene oxide repeats is 120 or less, it is preferable that both the printing durability due to abrasion and the printing durability due to ink acceptance do not deteriorate.

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

In general formula (a), y represents 2 to 120, R ₁ represents a hydrogen atom or an alkyl group, and R ₂ represents a hydrogen atom or an organic group.

In the general formula (a), y is preferably 2 to 70, more preferably 2 to 50. As the organic machine represented by R ₂ , an alkyl group having 1 to 6 carbon atoms is preferable, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, Examples thereof include t-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, isohexyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, cyclopentyl group, and cyclohexyl group.
R ₁ is preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom. R ₂ is particularly preferably a hydrogen atom or a methyl group.

The binder polymer may have crosslinkability in order to improve the film strength of the image area. In order to impart crosslinkability to the polymer, a crosslinkable functional group such as an ethylenically unsaturated bond may be introduced into the main chain or side chain of the polymer. The crosslinkable functional group may be introduced by copolymerization.
Examples of the polymer having an ethylenically unsaturated bond in the main chain of the molecule include poly-1,4-butadiene and poly-1,4-isoprene.

Examples of polymers having an ethylenically unsaturated bond in the side chain of the molecule are polymers of esters or amides of acrylic acid or methacrylic acid, where the ester or amide residue (-COOR or CONHR R) is ethylene. Examples thereof include polymers having a polymerizable unsaturated bond.

Examples of the residue having the ethylenically unsaturated bond (the above R) include-(CH ₂ ) _n CR ¹ = CR ² R ³ ,-(CH ₂ O) _n CH ₂ CR ¹ = CR ² R ³ ,- (CH ₂ CH ₂ O) _n CH ₂ CR ¹ ═CR ² R ³ , — (CH ₂ ) _n NH—CO—O—CH ₂ CR ¹ ═CR ² R ³ , — (CH ₂ ) _n —O—CO —CR ¹ ═CR ² R ³ and (CH ₂ CH ₂ O) ₂ —X (wherein R ¹ to R ³ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 20 carbon atoms, aryl 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, and X represents dicyclopentadi. An enyl residue).

Specific examples of the ester residue include —CH ₂ CH═CH ₂ (described in JP-B-7-21633), —CH ₂ CH ₂ O—CH ₂ CH═CH ₂ , —CH ₂ C _{(CH 3) = CH 2,} -CH 2 CH = CH-C 6 H 5, -CH 2 CH 2 OCOCH = CH-C 6 H 5, -CH 2 CH 2 -NHCOO-CH 2 CH = CH 2 and CH ₂ CH ₂ O—X (wherein X represents a dicyclopentadienyl residue).

Specific examples of the amide residue include —CH ₂ CH═CH ₂ , —CH ₂ CH ₂ —Y (wherein Y represents a cyclohexene residue), —CH ₂ CH ₂ —OCO—CH═CH _2. Is mentioned.

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

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

Specific examples (1) to (13) of the binder polymer used in the image recording layer of the on-press development type lithographic printing plate precursor are shown below, but the present invention is not limited thereto.

In addition, in the following exemplary compounds, a numerical value written together with each repeating unit (a numerical value written together with the main chain repeating unit) represents a mole percentage of the repeating unit. The numerical value written together with the repeating unit of the side chain indicates the number of repetitions of the repeating site.

The mass average molar mass (Mw) of the binder polymer is preferably 2000 or more, more preferably 5000 or more, and further preferably 10,000 to 300,000 as a polystyrene conversion value by the GPC method.

In the image recording layer, hydrophilic polymer compounds such as polyacrylic acid and polyvinyl alcohol described in JP-A-2008-195018 can be used in combination as required. Further, a lipophilic polymer compound and a hydrophilic polymer compound can be used in combination.

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

The content of the binder polymer is preferably 3 to 90% by mass and more preferably 6 to 80% by mass with respect to the total solid content of the image recording layer.

The image recording layer may further contain a low molecular weight hydrophilic compound, a sensitizer, and other components as necessary.

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

In the present invention, it is preferable to contain at least one selected from polyols, organic sulfates, organic sulfonates and betaines.

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

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

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

Since low molecular weight hydrophilic compounds have a small hydrophobic part structure and almost no surface-active action, dampening water penetrates into the exposed part of the image recording layer (image part) and decreases the hydrophobicity and film strength of the image part. The ink receptivity and printing durability of the image recording layer can be maintained satisfactorily.

The low molecular weight hydrophilic compound may be used alone or in combination of two or more. The content of the low molecular weight hydrophilic compound is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, based on the total solids of the image recording layer, from the viewpoint of good on-press developability and printing durability. 2 to 10% by mass is more preferable.

(2) Grease Sensitizer A grease sensitizer such as a phosphonium compound, a nitrogen-containing low molecular weight compound, or an ammonium group-containing polymer can be used in the image recording layer in order to improve the inking property. In particular, when an inorganic layered compound is contained in the protective layer, the sensitizer functions as a surface coating agent for the inorganic layered compound, and has the effect of preventing a decrease in the inking property during printing by the inorganic layered compound. .

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

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

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

The ammonium salt-containing polymer preferably has a reduced specific viscosity (unit: ml / g) obtained by the measuring method described in JP-A-2009-208458, preferably in the range of 5 to 120, and in the range of 10 to 110. Are more preferable, and those in the range of 15 to 100 are particularly preferable. When the reduced specific viscosity is converted into mass average molar mass (Mw), it is preferably 10,000 to 150,000, more preferably 17,000 to 140000, and particularly preferably 20,000 to 130,000.

Specific examples of the ammonium group-containing polymer are shown below, but the present invention is not limited thereto. (1) 2- (trimethylammonio) ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90, Mw 45,000) (2) 2- (trimethylammonio) ) Ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 60,000) (3) 2- (ethyldimethylammonio) ethyl methacrylate = p-toluenesulfonate / Hexyl methacrylate copolymer (molar ratio 30/70 Mw 45,000) (4) 2- (trimethylammonio) ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20/80 Mw 6. (0000) (5) 2- (Trimethylammonio) Ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (molar ratio 40/60, Mw 7 million) (6) 2- (butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate Copolymer (molar ratio 25/75, Mw 65,000) (7) 2- (butyldimethylammonio) ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80 Mw 65,000) (8) 2- (Butyldimethylammonio) ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate / 3,6-dioxaheptyl methacrylate copolymer ( Molar ratio 20/80 Mw 75,000) (9) 2- ( Chill dimethyl ammonio) ethyl methacrylate hexafluorophosphate / 3,6-dioxaheptyl methacrylate / 2-hydroxy-3-methacryloyl oxy propyl methacrylate copolymer (molar ratio 15/80/5 Mw6.5 50,000)

The sensitizer may be used alone or in combination of two or more. The content of the sensitizer is preferably 0.01 to 30.0% by mass, more preferably 0.1 to 15.0% by mass, and more preferably 1 to 10% by mass with respect to the total solid content of the image recording layer. Further preferred.

(3) Others In the image recording layer, as other components, surfactants, colorants, print-out agents, polymerization inhibitors, higher fatty acid derivatives, plasticizers, inorganic fine particles, inorganic layered compounds, co-sensitizers or chains. A transfer agent or the like can be added as necessary. Specifically, paragraph numbers [0114] to [0159] of Japanese Patent Application Laid-Open No. 2008-284817, paragraph numbers [0023] to [0027] of Japanese Patent Application Laid-Open No. 2006-091479, and US Patent Publication No. 2008/0311520. The compound and the addition amount described in paragraph [0060] are preferably used.

In the lithographic printing plate precursor according to the invention, it is a preferable aspect that the unexposed portion of the image recording layer can be removed by at least one of dampening water and printing ink.

(Formation of image recording layer)
In the image recording layer of the lithographic printing plate precursor according to the present invention, for example, as described in paragraph numbers [0142] to [0143] of JP-A-2008-195018, the necessary components described above are dispersed in a known solvent. Alternatively, it can be formed by preparing a coating solution by dissolving, applying the coating solution on a support by a known method such as bar coater coating, and drying. The coating amount (solid content) of the image recording layer on the support after coating and drying varies depending on the application, but is generally 0.3 to from the viewpoint of good sensitivity and good film properties of the image recording layer. 3.0 g / m ² is preferred.

[Support]
As the support for the planographic printing plate precursor according to the invention, a known support for a planographic printing plate precursor is used. As the support, an aluminum plate which has been roughened and anodized by a known method is preferable.
For the aluminum plate, if necessary, the micropore enlargement treatment and sealing treatment of the anodized film described in JP-A-2001-253181 and JP-A-2001-322365 are further disclosed. Surface hydrophilization treatment with alkali metal silicate as described in the specifications of Nos. 714, 066, 3,181,461, 3,280,734 and 3,902,734 Surface hydrophilization treatment with polyvinylphosphonic acid as described in US Pat. Nos. 3,276,868, 4,153,461 and 4,689,272, as appropriate. You can choose to do it.
The support preferably has a center line average roughness of 0.10 to 1.2 μm.

A back coat layer containing an organic polymer compound described in JP-A No. 5-45885 or a silicon alkoxy compound described in JP-A No. 6-35174 on the back surface as necessary. Can be provided.

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

Examples of the compound used for the undercoat layer include compounds having an adsorptive group and a hydrophilic group that can be adsorbed on the surface of the support. In order to improve the adhesion to the image recording layer, a compound having an adsorptive group and a hydrophilic group and further having a crosslinkable group is preferred. The compound used for the undercoat layer may be a low molecular compound or a high molecular compound. The compounds used for the undercoat layer may be used as a mixture of two or more if necessary.

When the compound used for the undercoat layer is a polymer compound, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferable.
Examples of the adsorptive groups that can be adsorbed on the support surface include phenolic hydroxy groups, carboxyl groups, —PO ₃ H ₂ , —OPO ₃ H ₂ , —CONHSO ₂ —, —SO ₂ NHSO ₂ —, and —COCH ₂ COCH _3. preferable. The hydrophilic group is preferably a sulfo group or a salt thereof, or a salt of a carboxyl group. The crosslinkable group is preferably a methacryl group or an allyl group.
The polymer compound may have a crosslinkable group introduced by salt formation between the polar substituent of the polymer compound, a substituent having a counter charge with the polar substituent, and a compound having an ethylenically unsaturated bond. Alternatively, monomers other than those described above, preferably hydrophilic monomers may be further copolymerized.

Specifically, a silane coupling agent having an ethylenic double bond reactive group capable of addition polymerization described in JP-A No. 10-282679 and an ethylenic compound described in JP-A No. 2-304441. The phosphorus compound which has a heavy bond reactive group is mentioned suitably. Crosslinkable groups (preferably ethylenically unsaturated bond groups) described in JP-A-2005-238816, JP-A-2005-12549, JP-A-2006-239867, and JP-A-2006-215263, a support A low molecular or high molecular compound having a functional group interacting with the surface and a hydrophilic group is also preferably used.
More preferable are polymer compounds having an adsorptive group, a hydrophilic group and a crosslinkable group which can be adsorbed on the surface of the support described in JP-A Nos. 2005-125749 and 2006-188038.

The content of unsaturated double bonds in the polymer compound for the undercoat layer is preferably 0.1 to 10.0 mmol, more preferably 0.2 to 5.5 mmol per 1 g of the polymer compound.
The mass average molar mass (Mw) of the polymer compound for the undercoat layer is preferably 5000 or more, more preferably 10,000 to 300,000 as a polystyrene conversion value by GPC method.

In addition to the undercoat layer compound, the undercoat layer is a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, an amino group, or a functional group having a polymerization inhibiting ability and an aluminum support surface to prevent contamination over time. Having a group that interacts with (eg, 1,4-diazabicyclo [2,2,2] octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, hydroxy Ethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, and the like).

The undercoat layer can be applied by a known method. The coating amount (solid content) of the undercoat layer is preferably 0.1 ~ 100mg / ^{m 2,} and more preferably 1 ~ 30mg / ^{m 2.}

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

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

The protective layer preferably contains an inorganic layered compound in order to enhance oxygen barrier properties. The inorganic layered compound is a particle having a thin plate-like shape, for example, mica group such as natural mica and synthetic mica, talc, teniolite, montmorillonite, saponite, hectorite represented by the formula 3MgO · 4SiO · H ₂ O And zirconium phosphate.
The inorganic layered compound preferably used is a mica compound. As the mica compound, for example, the general formula: A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O) ₂ [where A is any of K, Na, Ca, and B and C are , Fe (II), Fe (III), Mn, Al, Mg, or V, and D is Si or Al. ] Mica groups such as natural mica and synthetic mica represented by

In the mica group, natural mica includes muscovite, soda mica, phlogopite, biotite, and sericite. As the synthetic mica, non-swelling mica such as fluorine phlogopite mica ₃ (AlSi ₃ O ₁₀ ) F ₂ , potassium tetrasilicon mica KMg _2.5 Si ₄ O ₁₀ ) F ₂ , and Na tetrasilicic mica NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ , Na or Li teniolite (Na, Li) Mg ₂ Li (Si ₄ O ₁₀ ) F ₂ , montmorillonite-based Na or Li hectorite (Na, Li) _1/8 Mg _2/5 Examples thereof include swelling mica such as Li _1/8 (Si ₄ O ₁₀ ) F ₂ . Synthetic smectite is also useful.

Of the mica compounds, fluorine-based swellable mica is particularly useful. That is, the swellable synthetic mica has a laminated structure composed of unit crystal lattice layers with a thickness of about 10 to 15 mm, and the substitution of metal atoms in the lattice is significantly larger than other clay minerals. As a result, the lattice layer is deficient in positive charge, and in order to compensate for this, cations such as Li ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ are adsorbed between the layers. The cations present between these layers are called exchangeable cations and exchange with various cations. In particular, when the cation between layers is Li ⁺ or Na ⁺ , the bond between the layered crystal lattices is weak because the ionic radius is small, and the layer swells greatly with water. If shear is applied in this state, it will easily cleave and form a stable sol in water. Swelling synthetic mica has a strong tendency and is particularly preferably used.

As the shape of the mica compound, from the viewpoint of diffusion control, the thinner the better, the better the plane size as long as it does not hinder the smoothness of the coated surface or the transmittance of actinic rays. Accordingly, the aspect ratio is 20 or more, preferably 100 or more, particularly preferably 200 or more. The aspect ratio is the ratio of the major axis to the thickness of the particle, and can be measured from, for example, a projection drawing of a micrograph of the particle. The larger the aspect ratio, the greater the effect that can be obtained.

The average major axis of the mica compound is 0.3 to 20 μm, preferably 0.5 to 10 μm, particularly preferably 1 to 5 μm. The average thickness of the particles is 0.1 μm or less, preferably 0.05 μm or less, particularly preferably 0.01 μm or less. Specifically, for example, in the case of swellable synthetic mica which is a representative compound, the thickness is 1 to 50 nm and the surface size (major axis) is about 1 to 20 μm.

The content of the inorganic stratiform compound is preferably 0 to 60% by mass and more preferably 3 to 50% by mass with respect to the total solid content of the protective layer. Even when a plurality of types of inorganic layered compounds are used in combination, the total amount of the inorganic layered compounds is preferably the above-described mass. Within the above range, the oxygen barrier property is improved and good sensitivity is obtained. Further, it is possible to prevent a decrease in inking property.

The protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coating properties, and inorganic fine particles for controlling surface slipperiness. Further, the protective layer can contain the sensitizer described in the image recording layer.

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

[Plate making method]
The plate-making method according to the present invention includes a step of image-exposing the lithographic printing plate precursor and an on-press development step of developing using an oil-based ink and an aqueous component on a printing press.

<Exposure process>
The planographic printing plate precursor according to the present invention can be image-exposed by a method of scanning and exposing digital data with an infrared laser or the like.
The wavelength of the light source is preferably 750 to 1400 nm. As the light source having a wavelength of 750 to 1400 nm, a solid laser or semiconductor laser that emits infrared light is suitable. The exposure mechanism may be any of an internal drum system, an external drum system, a flat bed system, and the like.
The exposure step can be performed by a known method using a plate setter or the like. Alternatively, the exposure may be performed on the printing machine after the planographic printing plate precursor is mounted on the printing machine using a printing machine equipped with an exposure device.

<On-machine development process>
In the on-press development process, if the lithographic printing plate precursor after image exposure is not subjected to any development processing, printing is started as it is by supplying oil-based ink and aqueous component, and lithographic printing is performed at an early stage of printing. The unexposed portion of the plate precursor is removed, and accordingly, the hydrophilic support surface is exposed to form a non-image portion. As the oil-based ink and the aqueous component, ordinary lithographic printing ink and fountain solution are used. Here, printing ink or fountain solution may be supplied to the printing plate first, but the printing ink is first applied in order to prevent the fountain solution from being contaminated by the removed image recording layer components. It is preferable to supply.
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, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. In the polymer compound, except for those specifically defined, the molecular weight is a mass average molar mass (Mw) in terms of polystyrene converted by the GPC method, and the ratio of repeating units is a mole percentage.

Synthesis examples of microgel (D) are shown below.

<Synthesis of Microgel MG-2>
13 g of methyl ethyl ketone solution (35% by mass) of the following adduct of AO-4 and NCO-1; adduct of trimethylolpropane, xylene diisocyanate and polyethylene glycol monomethyl ether (manufactured by Mitsui Chemicals, Takenate D-116N) 3.5 g, 6.5 g of pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., SR444) and 0.5 g of alkylbenzene sulfonate (manufactured by Takemoto Yushi Co., Ltd., Pionein A-41C) are dissolved in 17 g of ethyl acetate. Thus, an oil phase component was prepared. Distilled water (50 g) was added to the oil phase component as an aqueous phase component, mixed, and emulsified at 12,000 rpm for 10 minutes using a homogenizer. The obtained emulsion was added to 25 g of distilled water, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours. Diluted with distilled water so that the solid content concentration of the obtained microgel solution was 15% by mass to obtain microgel MG-2. The average particle size of the microgel measured by the light scattering method was 0.25 μm.

(Preparation of methyl ethyl ketone solution (35% by mass) of adduct of AO-4 and NCO-1)
To a solution containing AO-4 (20 g), NCO-1 (35.4 g) and methyl ethyl ketone (102 g), 0.16 g of bismuth 2-ethylhexanoate (Nitto Kasei Co., Ltd., Neostan U-600) was added. The mixture was stirred under heating at 50 ° C. for 1 hour and then at 70 ° C. for 2 hours, and then cooled to room temperature to prepare a methyl ethyl ketone solution (35% by mass) of an adduct of AO-2 and NCO-1.

<Synthesis of Microgel MG-3>
13 g of methyl ethyl ketone solution (35% by mass) of the above adduct of AO-2 and NCO-1, adduct of trimethylolpropane, xylene diisocyanate and polyethylene glycol monomethyl ether (manufactured by Mitsui Chemicals, Takenate D-116N) 3.5 g, 6.5 g of pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., SR444) and 0.5 g of alkylbenzene sulfonate (manufactured by Takemoto Yushi Co., Ltd., Pionein A-41C) are dissolved in 17 g of ethyl acetate. Thus, an oil phase component was prepared. To the oil phase component, 49 g of distilled water and 1 g of trimethylolpropane were added and mixed as an aqueous phase component, and the mixture was emulsified at 12,000 rpm for 10 minutes using a homogenizer. The obtained emulsion was added to 25 g of distilled water, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours. Distilled water was used to dilute the solid content concentration of the obtained microgel solution to 15% by mass to obtain microgel MG-3. The average particle size of the microgel measured by the light scattering method was 0.25 μm.

<Synthesis of Microgel MG-4 to 7, 14, 19, 22>
Based on the same method as in the above <Synthesis of Microgel MG-2> except that each of the components (1) to (3) described in Table 3 above was used, respectively, Microgel MG-4 to 7, 14, 19, 22 was synthesized.

<Synthesis of Comparative Microgel MG-A>
13 g of methyl ethyl ketone solution (35% by mass) of the following adduct of trimethylolpropane and NCO-1; adduct of trimethylolpropane, xylene diisocyanate and polyethylene glycol monomethyl ether (manufactured by Mitsui Chemicals, Takenate D-116N) 3.5 g, 6.5 g of pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., SR444) and 0.5 g of alkylbenzene sulfonate (manufactured by Takemoto Yushi Co., Ltd., Pionein A-41C) are dissolved in 17 g of ethyl acetate. Thus, an oil phase component was prepared. Distilled water (50 g) was added to the oil phase component as an aqueous phase component, mixed, and emulsified at 12,000 rpm for 10 minutes using a homogenizer. The obtained emulsion was added to 25 g of distilled water, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours. Distilled water was used to dilute the solid content concentration of the obtained microgel solution to 15% by mass to obtain microgel MG-A. The average particle size of the microgel measured by the light scattering method was 0.25 μm.

(Preparation of methyl ethyl ketone solution (35% by mass) of adduct of trimethylolpropane and NCO-1)
Addition of trimethylolpropane and NCO-1 in the same manner except that trimethylolpropane was used instead of AO-2 in the preparation of the methyl ethyl ketone solution (35% by mass) of the adduct of AO-2 and NCO-1. Body methyl ethyl ketone solution (35% by mass) was prepared.

<Synthesis of Comparative Microgel MG-B>
11 g of a methyl ethyl ketone solution (35% by mass) of the above-mentioned adduct of trimethylolpropane and NCO-1, adduct of trimethylolpropane, xylene diisocyanate and polyethylene glycol monomethyl ether (manufactured by Mitsui Chemicals, Takenate D-116N) 3.5 g, 1.0 g of triethylene glycol monomethyl ether, 6.5 g of pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., SR444), and alkylbenzene sulfonate (manufactured by Takemoto Yushi Co., Ltd., Pionine A-41C) An oil phase component was prepared by dissolving 0.5 g in 18 g of ethyl acetate. Distilled water (50 g) was added to the oil phase component as an aqueous phase component, mixed, and emulsified at 12,000 rpm for 10 minutes using a homogenizer. The obtained emulsion was added to 25 g of distilled water, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours. Diluted with distilled water so that the solid content concentration of the obtained microgel solution was 15% by mass to obtain microgel MG-B. The average particle size of the microgel measured by the light scattering method was 0.25 μm.

[Examples 1 to 18 and Comparative Examples 1 to 3]

1. Production of lithographic printing plate precursor <Production of support>
In order to remove rolling oil on the surface of a 0.3 mm thick aluminum plate (material JIS A 1050), after degreasing at 50 ° C. for 30 seconds using a 10 mass% sodium aluminate aqueous solution, the hair diameter is 0.3 mm. The aluminum surface was grained with three bundle-planted nylon brushes and a pumice-water suspension (specific gravity 1.1 g / cm ³ ) having a median diameter of 25 μm and washed thoroughly with water. Etching was performed by immersing the aluminum plate in a 25 mass% sodium hydroxide aqueous solution at 45 ° C for 9 seconds, washing with water, and further immersed in a 20 mass% nitric acid aqueous solution at 60 ° C for 20 seconds, followed by washing with water. At this time, the etching amount of the grained surface was about 3 g / m ² .

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

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

<Formation of undercoat layer>
On the support 2, an undercoat layer coating solution having the following composition was applied to a dry coating amount of 20 mg / m ² to form an undercoat layer.

(Coating solution for undercoat layer)
・ Undercoat layer compound [below] 0.18 g
・ Hydroxyethyliminodiacetic acid 0.10g
・ Methanol 55.24g
・ Water 6.15g

<Formation of image recording layer>
An image recording layer coating solution having the following composition was bar coated on the undercoat layer 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 .
The image recording layer coating solution was prepared by mixing and stirring the following photosensitive solution and microgel solution immediately before coating.

(Photosensitive solution)
・ Binder polymer [below] 0.240 g
・ Infrared absorbing dye [below] 0.020 g
・ Radical polymerization initiator [below] 0.2g
-Compound having electron donating ability (TPB) [below] Amount shown in Table 4-Radical polymerizable compound 0.192 g
Tris (acryloyloxyethyl) isocyanurate (NK ester A-9300, manufactured by Shin-Nakamura Chemical Co., Ltd.)
・ Low molecular weight hydrophilic compound 0.062g
Tris (2-hydroxyethyl) isocyanurate / low molecular weight hydrophilic compound [below] 0.050 g
・ Fat Sensitizer 0.055g
Phosphonium compounds (below)
・ Fat Sensitizer 0.018g
Benzyl-dimethyl-octylammonium ・ PF ₆ salt ・ Sensitizer 0.035 g
Ammonium group-containing polymer [below] [reduced specific viscosity 44 ml / g]
・ Fluorosurfactant [below] 0.008g
・ 2-butanone 1.091g
・ 1-methoxy-2-propanol 8.609g

(Microgel solution)
Microgel (15% by mass) [described in Table 4] 2.640 g
・ Distilled water 2.425g

Binder polymer, infrared absorbing dye, radical polymerization initiator, compound having electron donating ability (TPB), fluorine-based surfactant, low molecular weight hydrophilic compound, phosphonium compound, and ammonium group used in the image recording layer coating solution The structure of the contained polymer is as shown below.

<Formation of protective layer>
A protective layer coating solution having the following composition was bar coated on the image recording layer, followed by oven drying at 120 ° C. for 60 seconds to form a protective layer having a dry coating amount of 0.15 g / m ² . In this way, lithographic printing plate precursors A-1 to A-18 and comparative lithographic printing plate precursors A′-1 to A′-3 according to the present invention were prepared, respectively.

(Protective layer coating solution)
・ Inorganic layered compound dispersion (1) 1.5 g
-Polyvinyl alcohol (Nippon Synthetic Chemical Industry Co., Ltd. CKS50, sulfonic acid modification,
Saponification degree 99 mol% or more, polymerization degree 300) 6% by mass aqueous solution 0.55 g
・ Polyvinyl alcohol (PVA-405 manufactured by Kuraray Co., Ltd.)
Degree of saponification 81.5 mol%, degree of polymerization 500) 6% by weight aqueous solution 0.03 g
・ Polyoxyethylene lauryl ether (Emulex 710 manufactured by Japan Emulsion Co., Ltd.) 1% by weight aqueous solution 0.86g
・ Ion-exchanged water 6.0g

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

2. Evaluation of lithographic printing plate precursor The obtained lithographic printing plate precursor was evaluated for on-press developability, printing durability, and tone reproducibility as follows.

(1) On-machine developability The lithographic printing plate precursor was exposed with a Luxel PLANETSETTER T-6000III equipped with an infrared semiconductor laser under conditions of an outer drum rotation speed of 1000 rpm, a laser output of 70%, and a resolution of 2400 dpi. The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The exposed lithographic printing plate precursor was mounted on the plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Equality-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) dampening water and Values-G (N) black ink (manufactured by Dainippon Ink & Chemicals, Inc.) Dampening water and ink were supplied using the standard automatic printing start method of LITHRONE 26, and 100 sheets were printed on Tokishi Art (76.5 kg) paper (Mitsubishi Paper Co., Ltd.) at a printing speed of 10,000 sheets per hour. .
On-press development was evaluated as the on-press developability of the number of print sheets required until the on-press development of the unexposed portion of the image recording layer was completed on the printing press and the ink was not transferred to the non-image portion. The results are shown in Table 4.

(2) Printing durability After the on-press developability was evaluated, printing was further continued. As the number of printed sheets was increased, the image recording layer was gradually worn out, so that the ink density on the printed material decreased. The number of copies when the halftone dot area ratio of 50% halftone dot FM screen in the printed matter is 5% lower than the measured value of the 100th printed matter when the value measured with a reflection densitometer RD-918 manufactured by Gretag-Macbeth is used. The printing durability was evaluated. The results are shown in Table 4.

(3) Tone reproducibility The lithographic printing plate precursor was exposed with a Luxel PLANETSETTER T-6000III manufactured by FUJIFILM Corporation under the conditions of an outer drum rotation speed of 400 rpm, a laser output of 85%, and a resolution of 2400 dpi. The exposure image includes a 50% halftone dot chart of AM200 line. On-press development is performed in the same manner as the on-press developability evaluation, and on the 100th printed matter, the halftone dot area ratio of the exposed portion is measured with a halftone dot measuring device iCplate2 (manufactured by x-rite). The reproducibility was evaluated. The results are shown in Table 4. The closer the numerical value (%) is to 50, the better the tone reproducibility. A halftone dot measurement value of 50 to 53 is preferable for tone reproducibility, and 60 or more is outside the allowable range for practical use.

From the results shown in Table 4, it can be seen that when the microgel according to the present invention is used, excellent tone reproducibility can be obtained while maintaining good on-press developability and printing durability. This is considered due to the fact that alkyleneoxy groups are incorporated into the wall structure of the microgel. In addition, when a compound having an electron donating ability is used (Examples 10 to 18), tone reproducibility is maintained well even if printing durability is improved, and the balance between printing durability and tone reproducibility is extremely high. It turns out that it is excellent in. On the other hand, in Comparative Examples 2 and 3, the tone reproducibility is remarkably deteriorated as the printing durability is improved, and the balance between the two cannot be maintained.

According to the present invention, it is possible to provide a planographic printing plate precursor excellent in tone reproducibility and a plate making method thereof while maintaining good on-press developability and printing durability.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on September 24, 2014 (Japanese Patent Application No. 2014-193661), the contents of which are incorporated herein by reference.

Claims (10)

1. A lithographic printing plate precursor having an image recording layer containing (A) a radical polymerizable compound, (B) an infrared absorbing dye, (C) a radical polymerization initiator, and (D) a microgel on a hydrophilic support. The (D) microgel has (1) a compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms, and (2) a polyfunctional isocyanate compound. A lithographic printing plate precursor which is a reaction product of
2. (D) the microgel has (1) a compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms, (2) a polyfunctional isocyanate compound, and (3) The lithographic printing plate precursor as claimed in claim 1, which is a reaction product of a compound other than (1) having at least one active hydrogen atom.
3. (1) The compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms is a polyfunctional amine, polyfunctional alcohol, polyfunctional phenol and polyfunctional The lithographic printing plate precursor as claimed in claim 1 or 2, which is at least one compound selected from thiols.
4. (3) The compound other than (1) having at least one active hydrogen atom is at least one compound selected from water, a polyfunctional amine, a polyfunctional alcohol, a polyfunctional phenol, and a polyfunctional thiol. 2. The lithographic printing plate precursor as described in 2 or 3.
5. (1) the compound having at least two groups having active hydrogen atoms and at least one alkyleneoxy group having 2 to 12 carbon atoms has at least two groups having active hydrogen atoms, and The lithographic printing plate precursor as claimed in any one of Claims 1 to 4, which is a compound having at least two alkyleneoxy groups having 2 to 12 carbon atoms.
6. The lithographic printing plate precursor as claimed in any one of claims 1 to 5, wherein the image recording layer comprises (E) a compound having an electron donating ability.
7. The lithographic printing plate precursor as claimed in claim 6, wherein the compound (E) having an electron donating ability is an alkyl or aryl art complex compound or an N-arylalkylamine compound.
8. The lithographic printing plate precursor as claimed in any one of claims 1 to 7, further comprising a protective layer on the image recording layer.
9. The lithographic printing plate precursor as claimed in any one of claims 1 to 8, wherein an unexposed portion of the image recording layer can be removed with at least one of dampening water and printing ink.
10. 10. A plate making method wherein the lithographic printing plate precursor according to claim 9 is image-exposed with an infrared laser, and an unexposed portion of the image recording layer is removed on a printing machine with at least one of dampening water and printing ink.