JP7321115B2 - On-machine development type lithographic printing plate precursor, method for preparing lithographic printing plate, and lithographic printing method - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to an on-press development type lithographic printing plate precursor, a method for preparing a lithographic printing plate, and a lithographic printing method.

In general, a lithographic printing plate consists of oleophilic image areas that accept ink during the printing process and hydrophilic non-image areas that accept dampening water. Lithographic printing utilizes the property that water and oily ink repel each other. The oleophilic image area of the lithographic printing plate is used as the ink receiving area, and the hydrophilic non-image area is used as the dampening water receiving area (non-ink receiving area). In this method, the surface of the lithographic printing plate is made to have different ink adherence properties, the ink is applied only to the image area, and then the ink is transferred to a printing medium such as paper for printing.
Conventionally, a lithographic printing plate precursor (PS plate) comprising a hydrophilic support and a lipophilic photosensitive resin layer (image recording layer) provided thereon has been widely used to prepare the lithographic printing plate. Usually, after the lithographic printing plate precursor is exposed through an original image such as a lith film, the portion of the image-recording layer that will become the image portion is left, and the other unnecessary image-recording layer is removed with an alkaline developer or an organic solvent. A lithographic printing plate is obtained by dissolving and removing with a solvent to expose the surface of the hydrophilic support to form a non-image area.

In addition, due to growing interest in the global environment, environmental issues related to waste liquid associated with wet processing such as development processing are being highlighted.
In order to deal with the environmental problems described above, there is a trend toward simplification of development or plate making and elimination of processing. As one of the simple production methods, a method called "on-machine development" is performed. That is, in this method, after the lithographic printing plate precursor is exposed, the conventional development is not performed, and the unnecessary portion of the image recording layer is removed at the initial stage of the normal printing process by mounting the plate as it is in the printing press.

As conventional lithographic printing plate precursors, for example, Patent Document 1 discloses that (A) a polymerization initiator, (B) a polymerizable compound, and (C) a polymerization reaction are inhibited by heating on a support. A lithographic printing plate precursor having an image-recording layer containing a chemical species generating compound is described.

Further, in Patent Document 2, an image recording layer containing (A) a radical polymerization initiator, (B) a radically polymerizable compound, and (C) a polyfunctional polymerization inhibitor is provided on a support. ) A lithographic printing plate precursor is described in which the polyfunctional polymerization inhibitor has two or more radical trapping sites that directly bind to radicals to form covalent bonds in the molecule.

Japanese Patent Application Laid-Open No. 2006-001182 WO2014/045783

An object to be solved by an embodiment of the present disclosure is to provide an on-press development type lithographic printing plate precursor that provides a lithographic printing plate that has excellent printing durability and suppresses streak-like unevenness.
A problem to be solved by another embodiment of the present disclosure is to provide a lithographic printing plate making method or a lithographic printing method using the above-described on-press development type lithographic printing plate precursor.

Means for solving the above problems include the following aspects.
<1> having a support and an image recording layer formed on the support;
An on-press development type lithographic printing plate precursor, wherein the image-recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and a radical-induced polymerization inhibitor precursor.

<2> The on-press development type lithographic printing plate precursor as described in <1>, wherein the radical-induced polymerization inhibitor precursor is a compound having a radical scavenging site and a polymerization-inhibiting precursor site.
<3> The on-press development type lithographic printing plate precursor as described in <2>, wherein the radical-scavenging site is a site containing an ethylenically unsaturated double bond.
<4> The on-press development type lithographic printing plate precursor as described in <3>, wherein the site containing an ethylenically unsaturated double bond is a (meth)acryloxy group.
<5> The on-press development type lithographic printing plate precursor as described in <4>, wherein the polymerization-inhibited precursor site is a site containing a hydroxyl group.
<6> The on-press development type lithographic printing plate according to any one of <1> to <5>, wherein the radical-induced polymerization inhibitor precursor is a compound containing a partial structure represented by the following formula (1): Original printing plate.

In formula (1), Ra each independently represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group; Rb represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; , represents a (meth)acryloxy group.

<7> The content ratio A/B between the content A of the infrared absorbent and the content B of the radical-induced polymerization inhibitor precursor is 0.1 to 2.5 on a mass basis, <1 > to the on-press development type lithographic printing plate precursor according to any one of <6>.

<8> The on-press development type lithographic printing plate precursor according to any one of <1> to <7>, wherein the polymerization initiator comprises an electron-donating polymerization initiator and an electron-accepting polymerization initiator.
<9> The on-press development type lithographic printing plate precursor according to <8>, wherein the HOMO value of the infrared absorber-the HOMO value of the electron-donating polymerization initiator is 0.70 eV or less.
<10> The on-press development type lithographic printing plate precursor according to <8> or <9>, wherein the LUMO value of the electron-accepting polymerization initiator-the LUMO value of the infrared absorber is 0.80 eV or less.
<11> The on-press development type lithographic printing plate precursor as described in any one of <1> to <10>, wherein the polymerizable compound is a polymerizable compound having a functionality of 7 or more.
<12> The on-press development type lithographic printing plate precursor as described in any one of <1> to <11>, wherein the polymerizable compound is a polymerizable compound having a functionality of 10 or more.

<13> imagewise exposing the on-press development type lithographic printing plate precursor according to any one of <1> to <12>;
supplying at least one selected from the group consisting of printing ink and dampening water on a printing press to remove the image-recording layer in the non-image areas.
<14> imagewise exposing the on-press development type lithographic printing plate precursor according to any one of <1> to <12>;
a step of supplying at least one selected from the group consisting of printing ink and dampening water to remove the image-recording layer in the non-image areas on a printing press to prepare a lithographic printing plate;
and printing with the obtained lithographic printing plate.

According to one embodiment of the present disclosure, it is possible to provide an on-press development type lithographic printing plate precursor that provides a lithographic printing plate that has excellent printing durability and suppresses streak-like unevenness.
Further, according to another embodiment of the present invention, it is possible to provide a method for preparing a lithographic printing plate or a lithographic printing method using the above-described on-press development type lithographic printing plate precursor.

1 is a schematic cross-sectional view of one embodiment of a support; FIG. FIG. 4 is a schematic cross-sectional view of another embodiment of a support; 4 is a graph showing an example of an alternating waveform current waveform diagram used for electrochemical graining treatment in the method of manufacturing a support. FIG. 2 is a side view showing an example of a radial type cell in electrochemical graining treatment using alternating current in the support manufacturing method.

The content of the present disclosure will be described in detail below. The description of the constituent elements described below may be made based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.
In this specification, the term "to" indicating a numerical range is used to include the numerical values before and after it as lower and upper limits.
In the numerical ranges described step by step in the present disclosure, the upper limit or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described step by step. . Moreover, in the numerical ranges described in the present disclosure, the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples.
In addition, in the description of groups (atomic groups) in the present specification, the descriptions that do not indicate substitution or unsubstituted include those having no substituents as well as those having substituents. For example, the term “alkyl group” includes not only alkyl groups having no substituents (unsubstituted alkyl groups) but also alkyl groups having substituents (substituted alkyl groups).
In the present specification, "(meth)acrylic" is a term used as a concept that includes both acrylic and methacrylic, and "(meth)acryloyl" is a term that is used as a concept that includes both acryloyl and methacryloyl. is.
In addition, the term "step" in this specification is not only an independent step, but even if it cannot be clearly distinguished from other steps, if the intended purpose of the step is achieved included. In addition, in the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.
Furthermore, in the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.
In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) in the present disclosure are TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) columns, unless otherwise specified. It is a molecular weight converted using polystyrene as a standard substance detected with a solvent THF (tetrahydrofuran) and a differential refractometer using a gel permeation chromatography (GPC) analyzer.
As used herein, the term "lithographic printing plate precursor" includes not only a lithographic printing plate precursor but also a waste plate precursor. The term "lithographic printing plate" includes not only a lithographic printing plate prepared by subjecting a lithographic printing plate precursor to exposure, development and the like, but also a waste plate. In the case of a waste plate precursor, the operations of exposure and development are not necessarily required. A discard plate is a lithographic printing plate precursor to be attached to an unused plate cylinder, for example, when printing a part of a page in color newspaper printing in a single color or two colors.
In the present disclosure, the term "excellent in printing durability" means that the lithographic printing plate can print a large number of sheets. It is also called "printing durability".

≪On-machine development type lithographic printing plate precursor≫
The on-press development type lithographic printing plate precursor according to the present disclosure has a support and an image-recording layer formed on the support, and the image-recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compounds, and radical-induced polymerization inhibitor precursors.
Hereinafter, the on-press development type lithographic printing plate precursor according to the present disclosure is also simply referred to as a lithographic printing plate precursor.
The lithographic printing plate precursor according to the present disclosure is a negative type lithographic printing plate precursor in which an exposed portion is polymerized by infrared exposure.

2. Description of the Related Art In recent years, in the exposure of a lithographic printing plate precursor, an exposure machine equipped with an exposure head employing GLV (Grating Light Value) technology is sometimes used.
When the exposure is performed with this exposure device, the halftone dot image thickens in the scanning direction, and is observed as streak-like unevenness. This streak-like unevenness is sometimes called swath unevenness.
As a result of intensive studies on this streak-like unevenness, the present inventors have found that a lithographic printing plate precursor having the above-described structure can provide a lithographic printing plate in which streak-like unevenness is suppressed.

Although the detailed mechanism by which the above effects are obtained is unknown, it is presumed as follows.
The streak-like unevenness is considered to be caused by locally integrating the exposure amount. The lithographic printing plate precursor according to the present disclosure contains a radical-induced polymerization inhibitor precursor in the image-recording layer. The radical-induced polymerization inhibitor precursor is, as described later, a compound that is induced by radicals to produce a polymerization inhibitor. Therefore, the polymerization inhibitor is generated only when radicals are generated in the image recording layer by exposure.
The function of stopping or suppressing the polymerization reaction when radicals are generated in the image recording layer and the polymerization inhibitor is generated from the radical-induced polymerization inhibitor precursor, even if the amount of exposure is locally accumulated. works, and the polymerization reaction is less likely to be promoted in the integration portion.
As a result, it is presumed that thickening of the halftone dot image can be suppressed, and a lithographic printing plate in which streak-like unevenness is suppressed can be obtained.
In addition, the polymerization inhibitor is generated from the radical-induced polymerization inhibitor precursor only when radicals are generated in the image-recording layer by exposure. Hateful.
As a result, it is presumed that a lithographic printing plate having excellent printing durability can be obtained.

Note that the lithographic printing plate precursors described in Patent Documents 1 and 2 do not mention streak-like unevenness at all.

<Image recording layer>
The image-recording layer in the present disclosure contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound, and a radical-induced polymerization inhibitor precursor.
The image-recording layer in the present disclosure is an on-machine development image-recording layer and a negative image-recording layer.

The details of each component contained in the image recording layer will be described below.

[Radical Induced Polymerization Inhibitor Precursor]
A “radical-induced polymerization inhibitor precursor” in the present disclosure refers to a compound that is induced by radicals to produce a polymerization inhibitor. The radical-induced polymerization inhibitor precursor is a compound that does not or hardly functions as a polymerization inhibitor in a state where it is not induced by radicals.
The radical-induced polymerization inhibitor precursor is preferably a compound having a radical scavenging site and a polymerization-inhibiting precursor site from the viewpoint of exhibiting the above functions.

The radical scavenging site in the radical-induced polymerization inhibitor precursor is not particularly limited, but from the viewpoint of radical scavenging ability, it is preferably a site containing an ethylenically unsaturated double bond (that is, C=C). .
The site containing an ethylenically unsaturated double bond includes a (meth)acryloxy group, a styryl group, an allyl group, a vinyl group, and the like. From the viewpoint of radical scavenging ability, a (meth)acryloxy group is preferable. .

The polymerization-inhibiting precursor site in the radical-induced polymerization inhibitor precursor refers to a site that functions as a polymerization inhibitor.
Here, the polymerization inhibitor is a compound that terminates or suppresses the polymerization reaction.
Suitable polymerization inhibitors include conventionally known polymerization inhibitors such as phenol and quinone polymerization inhibitors, amine polymerization inhibitors, nitroso polymerization inhibitors, and phenothiazine.

Examples of phenol and quinone polymerization inhibitors include phenol, p-methoxyphenol, 2,6-di-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4-cresol, hydroquinone, catechol, t-butylcatechol, pyrogallol, resorcinol, 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), phenylhydroquinone, hydroquinone, t-butylhydroquinone, 2,5-di-t-butylhydroquinone, benzoquinone and the like.

Amine polymerization inhibitors include aniline, methoxyaniline, aminophenol, 2,4,6-tri-t-butylaniline, diphenylamine, triphenylamine, 2,2,6,6-tetramethylpiperidine, and derivatives thereof. etc.
Nitroso-based polymerization inhibitors include, for example, N-nitrosophenylhydroxylamine and metal salts thereof.

The polymerization-inhibiting precursor site in the radical-induced polymerization inhibitor precursor is preferably a site having a hydroxyl group (that is, a hydroxyl group) from the viewpoint of the performance of terminating or suppressing the polymerization reaction.
The site containing a hydroxyl group is more preferably a site having a phenolic hydroxyl group.

A linking group may be provided between the radical scavenging site and the polymerization inhibiting precursor site in the radical-induced polymerization inhibitor precursor, if necessary.

The radical-induced polymerization inhibitor precursor is preferably a compound containing a partial structure represented by the following formula (1).

In formula (1), Ra each independently represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group; Rb represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; , represents a (meth)acryloxy group.

Each Ra in formula (1) is preferably an alkyl group having 1 to 15 carbon atoms.
The alkyl group represented by Ra may be linear, branched, or cyclic.
The alkyl group represented by Ra is more preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms.
More specifically, Ra in formula (1) is preferably a methyl group, a t-butyl group, or a dimethylpropyl group.
Moreover, it is preferable that two Ra's in the formula (1) are the same group.
When Ra in formula (1) is an aryl group, the aryl group is preferably an aryl group having 6 to 12 carbon atoms.

Rb in Formula (1) is preferably a hydrogen atom or a methyl group.

The radical-induced polymerization inhibitor precursor is preferably at least one selected from the group consisting of compounds represented by the following formula (2) and compounds represented by the following formula (3).

In formula (2), Ra, Rc ¹ and Rc ² each independently represent a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group, and Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. group, and X represents a (meth)acryloxy group.

Ra in formula (2) has the same meaning as Ra in formula (1), and preferred embodiments are also the same.
Rb in formula (2) has the same definition as Rb in formula (1), and preferred embodiments are also the same.

Rc ¹ and Rc ² in formula (2) are each independently preferably an alkyl group having 1 to 15 carbon atoms.
The alkyl groups represented by Rc ¹ and Rc ² may be linear, branched, or cyclic.
The alkyl group represented by Rc ¹ and Rc ² is more preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms.
More specifically, Rc ¹ and Rc ² in formula (2) are preferably a methyl group, a butyl group, a dimethylpropyl group, or a methylcyclohexyl group, and a methyl group, a t-butyl group, or a 1,1-dimethylpropyl group. , or a 1-methylcyclohexyl group is more preferred.
Moreover, Rc ¹ and Rc ² in formula (2) are preferably the same group.

When Rc ¹ is a hydrogen atom and Rc ² is a methyl group, the methyl group represented by Rc ² may be substituted with a group represented by the following formula (2-1).

In formula (2-1), Ra represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group; Rb represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; Each independently represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group, and X represents a (meth)acryloxy group. "*" indicates the bonding position with the methyl group represented by ^Rc2 .

Ra in formula (2-1) has the same meaning as Ra in formula (1), and preferred embodiments are also the same.
Rb in formula (2-1) has the same definition as Rb in formula (1), and preferred embodiments are also the same.
Rd in formula (2-1) is preferably a hydrogen atom.

In formula (3), each Ra independently represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group; Rb represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; , represents a (meth)acryloxy group. m and n represent an integer of 2 or more.

Ra in formula (3) has the same meaning as Ra in formula (1), and preferred embodiments are also the same.
Rb in formula (3) has the same definition as Rb in formula (1), and preferred embodiments are also the same.

The n repeating units and the m repeating units may be arranged randomly or in blocks.
The molecular weight of the compound represented by formula (3) (weight average molecular weight when it has a molecular weight distribution) is preferably 500 to 10,000.

According to the radical-induced polymerization inhibitor precursor, a polymerization initiator is produced, for example, as follows.
For example, in the case of compound G-1 below, when the radical "R." is generated in the image-recording layer, the .pi. A -R bond is formed, and along with this, the hydroxyl group becomes a radical "O."

Specific examples of radical-induced polymerization inhibitor precursors are shown below, but the present disclosure is not limited thereto.
Among them, the following G-1 to G-5 are preferable from the viewpoint of obtaining a lithographic printing plate in which streak-like unevenness is suppressed.

The radical-induced polymerization inhibitor precursor may be a compound synthesized by a known method or a commercially available product.
Examples of commercially available radical-induced polymerization inhibitor precursors include Sumilizer (registered trademark) GM and Sumilizer (registered trademark) GS manufactured by Sumitomo Chemical Co., Ltd. Antioxidant GS and Antioxidant GM manufactured by Qingdao Jade New Material Technology. is mentioned.

Only one radical-induced polymerization inhibitor precursor may be used, or two or more thereof may be used in combination.

The content of the radical-induced polymerization inhibitor precursor should be 0.1% by mass to 20% by mass with respect to the total mass of the image-recording layer from the viewpoint of obtaining a lithographic printing plate in which streak-like unevenness is suppressed. is preferred, 1% by mass to 12% by mass is more preferred, 3% by mass to 12% by mass is even more preferred, and 3% by mass to 8% by mass is particularly preferred.

In the image recording layer of the present disclosure, the content ratio A/B of the content A of the infrared absorbing agent and the content B of the radical-induced polymerization inhibitor precursor provides a lithographic printing plate in which streak-like unevenness is suppressed. From the point of view, it is preferably 0.1 to 2.5, more preferably 0.2 to 2.0, even more preferably 0.3 to 1.0, and 0.1 to 2.5 on a mass basis. 3 to 0.8 are particularly preferred.

[Infrared absorber]
The image-recording layer in the present disclosure contains an infrared absorber.
The infrared absorbing agent is not particularly limited, and examples thereof include pigments and dyes.
As the dye used as the infrared absorbing agent, commercially available dyes and known dyes described in literature such as "Dye Handbook" (edited by the Society of Organic Synthetic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex salt azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinone imine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complexes. is mentioned.

Particularly preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further examples include cyanine dyes and indolenine cyanine dyes. Among them, cyanine dyes are particularly preferred.

The infrared absorber is preferably a cationic polymethine dye having an oxygen or nitrogen atom at the meso position. As cationic polymethine dyes, cyanine dyes, pyrylium dyes, thiopyrylium dyes, azulenium dyes, and the like are preferably exemplified, and cyanine dyes are preferable from the viewpoints of availability, solvent solubility during the introduction reaction, and the like.

Specific examples of cyanine dyes include compounds described in paragraphs 0017 to 0019 of JP-A-2001-133969, paragraphs 0016-0021 of JP-A-2002-023360, and paragraphs 0012-0037 of JP-A-2002-040638. Compounds described in, preferably paragraphs 0034 to 0041 of JP-A-2002-278057, compounds described in paragraphs 0080-0086 of JP-A-2008-195018, particularly preferably paragraph 0035 of JP-A-2007-90850 to 0043, and compounds described in paragraphs 0105 to 0113 of JP-A-2012-206495.
In addition, the compounds described in paragraphs 0008 to 0009 of JP-A-5-5005 and paragraphs 0022-0025 of JP-A-2001-222101 can also be preferably used.
As the pigment, compounds described in paragraphs 0072 to 0076 of JP-A-2008-195018 are preferable.

Only 1 type may be used for an infrared absorber and it may use 2 or more types together.
Also, a pigment and a dye may be used in combination as an infrared absorber.

The content of the infrared absorbing agent is preferably 0.1% by mass to 10.0% by mass, more preferably 0.5% by mass to 5.0% by mass, relative to the total mass of the image recording layer.

[Polymerization initiator]
The image-recording layer in the present disclosure contains a polymerization initiator.
The polymerization initiator preferably contains an electron-accepting polymerization initiator, and more preferably contains an electron-accepting polymerization initiator and an electron-donating polymerization initiator.

[Electron-accepting polymerization initiator]
The image-recording layer in the present disclosure preferably contains an electron-accepting polymerization initiator as a polymerization initiator.
The electron-accepting polymerization initiator is a compound that generates polymerization initiation species such as radicals by accepting one electron through intermolecular electron transfer when electrons of an infrared absorber are excited by infrared exposure.
The electron-accepting polymerization initiator is a compound that generates polymerization initiation species such as radicals and cations by the energy of light, heat, or both. A photopolymerization initiator or the like can be appropriately selected and used.
As the electron-accepting polymerization initiator, a radical polymerization initiator is preferable, and an onium salt compound is more preferable.
Further, the electron-accepting polymerization initiator is preferably an infrared-sensitive polymerization initiator.
Examples of electron-accepting radical polymerization initiators include (a) organic halides, (b) carbonyl compounds, (c) azo compounds, (d) organic peroxides, (e) metallocene compounds, and (f) azide compounds. , (g) hexaarylbiimidazole compounds, (i) disulfone compounds, (j) oxime ester compounds, and (k) onium salt compounds.

(a) As the organic halide, for example, compounds described in paragraphs 0022 to 0023 of JP-A-2008-195018 are preferable.
As the (b) carbonyl compound, for example, compounds described in paragraph 0024 of JP-A-2008-195018 are preferable.
(c) As the azo compound, for example, an azo compound described in JP-A-8-108621 can be used.
(d) As the organic peroxide, for example, compounds described in paragraph 0025 of JP-A-2008-195018 are preferable.
(e) As the metallocene compound, for example, compounds described in paragraph 0026 of JP-A-2008-195018 are preferable.
(f) Azide compounds include, for example, compounds such as 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone.
As the hexaarylbiimidazole compound (g), for example, compounds described in paragraph 0027 of JP-A-2008-195018 are preferable.
(i) Disulfone compounds include, for example, compounds described in JP-A-61-166544 and JP-A-2002-328465.
(j) As the oxime ester compound, for example, compounds described in paragraphs 0028 to 0030 of JP-A-2008-195018 are preferable.

Among the above electron-accepting polymerization initiators, oxime ester compounds and onium salt compounds are preferred from the viewpoint of curability. Among them, from the viewpoint of printing durability, an iodonium salt compound, a sulfonium salt compound or an azinium salt compound is preferable, an iodonium salt compound or a sulfonium salt compound is more preferable, and an iodonium salt compound is particularly preferable.
Specific examples of these compounds are shown below, but the present disclosure is not limited thereto.

Examples of iodonium salt compounds are preferably diaryliodonium salt compounds, more preferably diphenyliodonium salt compounds substituted with an electron-donating group such as an alkyl group or an alkoxyl group, and more preferably asymmetric diphenyliodonium salt compounds. . Specific examples include diphenyliodonium = hexafluorophosphate, 4-methoxyphenyl-4-(2-methylpropyl)phenyliodonium = hexafluorophosphate, 4-(2-methylpropyl)phenyl-p-tolyliodonium = hexafluorophosphate. Fluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium = tetrafluoroborate, 4-octyloxy Phenyl-2,4,6-trimethoxyphenyliodonium = 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, bis(4-t-butylphenyl ) iodonium hexafluorophosphate.

Examples of the sulfonium salt compounds are preferably triarylsulfonium salt compounds, particularly preferably triarylsulfonium salt compounds in which at least part of an electron-withdrawing group, such as a group on the aromatic ring, is substituted with a halogen atom. More preferred are triarylsulfonium salt compounds in which the total number of halogen atoms substituted on the ring is 4 or more. Specific examples include triphenylsulfonium hexafluorophosphate, triphenylsulfonium benzoylformate, bis(4-chlorophenyl)phenylsulfonium benzoylformate, bis(4-chlorophenyl)-4-methylphenylsulfonium tetrafluoro borate, tris(4-chlorophenyl)sulfonium 3,5-bis(methoxycarbonyl)benzenesulfonate, tris(4-chlorophenyl)sulfonium hexafluorophosphate, tris(2,4-dichlorophenyl)sulfonium hexafluorophosphate Fart is mentioned.

Examples of counter anions for iodonium salt compounds and sulfonium salt compounds include sulfonate anions, carboxylate anions, tetrafluoroborate anions, hexafluorophosphate anions, p-toluenesulfonate anions, tosylate anions, sulfonamide anions or sulfonimides. Anions are mentioned.
Among them, a sulfonamide anion or a sulfonimide anion is preferable, and a sulfonimide anion is more preferable.
As the sulfonamide anion, an arylsulfonamide anion is preferred.
Moreover, as the sulfonimide anion, a bisarylsulfonimide anion is preferable.
Specific examples of sulfonamide anions or sulfonimide anions are shown below, but the present disclosure is not limited thereto. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group, respectively.

The lowest unoccupied molecular orbital (LUMO) of the electron-accepting polymerization initiator is preferably −3.00 eV or less, more preferably −3.02 eV or less, from the viewpoint of improving sensitivity and preventing plate skipping. preferable.
The lower limit is preferably -3.80 eV or more, more preferably -3.60 eV or more.

The electron-accepting polymerization initiator may be used singly or in combination of two or more.

The content of the electron-accepting polymerization initiator is preferably 0.1% by mass to 50% by mass, more preferably 0.5% by mass to 30% by mass, relative to the total mass of the image-recording layer. , 0.8% by weight to 20% by weight.

[Electron donating polymerization initiator (polymerization aid)]
The image-recording layer in the present disclosure preferably contains an electron-donating polymerization initiator (also referred to as a "polymerization aid") as a polymerization initiator.
The electron-donating polymerization initiator provides radical It is a compound that generates polymerization initiation species such as
The electron-donating polymerization initiator is preferably an electron-donating radical polymerization initiator.

From the viewpoint of improving printing durability, the image-recording layer preferably contains the following electron-donating polymerization initiators.
(i) Alkyl or arylate complexes: It is believed that the carbon-hetero bond is oxidatively cleaved to generate active radicals. Specifically, borate compounds are preferred.
(ii) N-arylalkylamine compounds: It is believed that oxidation cleaves the C—X bond on the carbon adjacent to the nitrogen to generate an active radical. X is preferably a hydrogen atom, a carboxyl group, a trimethylsilyl group or a benzyl group. 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 used).
(iii) Sulfur-containing compound: The above-mentioned amines in which the nitrogen atom is replaced with a sulfur atom can generate active radicals by the same action. Examples thereof include phenylthioacetic acid (the phenyl group may or may not have a substituent).
(iv) Tin-containing compounds: The above-mentioned amines in which the nitrogen atom is replaced with a tin atom can generate active radicals by the same action.
(v) Sulfinates: can generate active radicals upon oxidation. Specifically, arylsulfin sodium and the like can be mentioned.

Among these, the image recording layer preferably contains a borate compound from the viewpoint of printing durability.
The borate compound is preferably a tetraarylborate compound or a monoalkyltriarylborate compound, more preferably a tetraarylborate compound, from the viewpoint of printing durability and color development.
The counter cation of the borate compound is not particularly limited, but is preferably an alkali metal ion or a tetraalkylammonium ion, more preferably a sodium ion, a potassium ion, or a tetrabutylammonium ion.

A preferred example of the borate compound is sodium tetraphenylborate.

B-1 to B-9 are shown below as preferred specific examples of the electron-donating polymerization initiator, but needless to say, the present invention is not limited to these. In the chemical formulas below, Ph represents a phenyl group and Bu represents an n-butyl group.

In addition, the highest occupied molecular orbital (HOMO) of the electron-donating polymerization initiator is preferably -6.00 eV or more, and -5.95 eV or more, from the viewpoint of improving sensitivity and preventing plate skipping. is more preferable, and −5.93 eV or more is even more preferable.
The upper limit is preferably -5.00 eV or less, more preferably -5.40 eV or less.

Only one type of electron-donating polymerization initiator may be used, or two or more types may be used in combination.

The content of the electron-donating polymerization initiator is preferably 0.01% by mass to 30% by mass, preferably 0.05% by mass, based on the total mass of the image-recording layer, from the viewpoint of sensitivity and printing durability. It is more preferably from 0.1 mass % to 20 mass %, more preferably from 0.1 mass % to 20 mass %.

In the present disclosure, the polymerization initiator may be a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form a counter salt.
For example, in the present disclosure, a compound in which an anion in an electron-donating polymerization initiator and a cation in an electron-accepting polymerization initiator form a countersalt is preferable, and an onium cation and a borate anion form a countersalt. more preferably a compound formed by forming a counter salt with an iodonium cation or a sulfonium cation and a borate anion, and a compound formed by forming a counter salt with a diaryliodonium cation or triarylsulfonium cation and a tetraarylborate anion is particularly preferred to be a compound formed by forming a counter salt.
As preferred embodiments of the anion in the electron-donating polymerization initiator and the cation in the electron-accepting polymerization initiator, the anion in the electron-donating polymerization initiator and the cation in the electron-accepting polymerization initiator are preferred. It is the same as the aspect.
When the image-recording layer contains an anion that is an electron-donating polymerization initiator and a cation that is an electron-accepting polymerization initiator (that is, when it contains the compound forming the counter salt), the image-recording layer shall include an electron-accepting polymerization initiator and the electron-donating polymerization initiator.
Further, a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form a counter salt may be used as an electron-donating polymerization initiator or as an electron-accepting polymerization initiator. good.
Further, the compound formed by forming a counter salt between an electron-donating polymerization initiator and an electron-accepting polymerization initiator may be used in combination with the above-described electron-donating polymerization initiator, or may be used in combination with the above-described electron-accepting polymerization initiator. It may be used in combination with a polymerization initiator.

[Preferred embodiment of infrared absorbing agent and electron-donating polymerization initiator]
In the image-recording layer of the present disclosure, the HOMO value of the infrared absorber-the HOMO value of the electron-donating polymerization initiator is preferably 0.70 eV or less, from the viewpoint of improving sensitivity and printing durability. It is more preferably ~-0.10 eV.
A negative value means that the HOMO of the electron-donating polymerization initiator is higher than the HOMO of the infrared absorber.

[Preferred Embodiments of Electron Accepting Polymerization Initiator and Infrared Absorber]
In the image recording layer of the present disclosure, the LUMO value of the electron-accepting polymerization initiator and the LUMO value of the infrared absorber is preferably 0.80 eV or less, from the viewpoint of improving sensitivity and printing durability. It is more preferably ~-0.10 eV.
A negative value means that the LUMO of the infrared absorber is higher than the LUMO of the electron-accepting polymerization initiator.

[Polymerizable compound]
The image-recording layer in the present disclosure contains a polymerizable compound.
In the present disclosure, a polymerizable compound refers to a compound having a polymerizable group.
The polymerizable group is not particularly limited as long as it is a known polymerizable group, but an ethylenically unsaturated group is preferred. The polymerizable group may be a radically polymerizable group or a cationic polymerizable group, but is preferably a radically polymerizable group.
The radically polymerizable group includes a (meth)acryloyl group, an allyl group, a vinylphenyl group, a vinyl group, and the like, and a (meth)acryloyl group is preferable from the viewpoint of reactivity.
The molecular weight of the polymerizable compound (the weight average molecular weight when it has a molecular weight distribution) is preferably 50 or more and less than 2,500.

The polymerizable compound used in the present disclosure may be, for example, a radical polymerizable compound or a cationically polymerizable compound, but an addition polymerizable compound having at least one ethylenically unsaturated bond (ethylenic unsaturated compounds).
The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, more preferably a compound having two or more terminal ethylenically unsaturated bonds. Polymerizable compounds have chemical forms such as, for example, monomers, prepolymers, ie dimers, trimers or oligomers, or mixtures thereof.
Among them, from the viewpoint of UV printing durability, the polymerizable compound preferably contains a trifunctional or higher polymerizable compound, more preferably contains a heptafunctional or higher polymerizable group, and a 10 or higher functional polymerizable compound. More preferably it contains a group. In addition, the polymerizable compound preferably contains a trifunctional or higher (preferably heptafunctional or higher, more preferably 10 or higher functional) ethylenically unsaturated compound from the viewpoint of the UV printing durability of the resulting lithographic printing plate. , tri- or higher (preferably hepta- or higher, more preferably 10- or higher) (meth)acrylate compound.

[Oligomer]
The polymerizable compound contained in the image-recording layer preferably contains a polymerizable compound that is an oligomer (hereinafter also simply referred to as "oligomer").
In the present disclosure, the term "oligomer" refers to a polymerizable compound having a molecular weight (weight average molecular weight when having a molecular weight distribution) of 600 or more and 10,000 or less and containing at least one polymerizable group.
From the viewpoint of excellent chemical resistance and UV printing durability, the molecular weight of the oligomer is preferably 1,000 or more and 5,000 or less.

From the viewpoint of improving UV printing durability, the number of polymerizable groups in one molecule of the oligomer is preferably 2 or more, more preferably 3 or more, still more preferably 6 or more, and 10 or more. is particularly preferred.
The upper limit of the polymerizable groups in the oligomer is not particularly limited, but the number of polymerizable groups is preferably 20 or less.

From the viewpoint of UV printing durability and on-press developability, the oligomer preferably has 7 or more polymerizable groups and a molecular weight of 1,000 or more and 10,000 or less. More preferably, the number of groups is 7 or more and 20 or less and the molecular weight is 1,000 or more and 5,000 or less.

From the viewpoint of UV printing durability, visibility, and on-press developability, the oligomer has at least one selected from the group consisting of a compound having a urethane bond, a compound having an ester bond, and a compound having an epoxy residue. is preferable, and it is preferable to have a compound having a urethane bond.
In the present disclosure, an epoxy residue refers to a structure formed by an epoxy group, and means a structure similar to a structure obtained by reacting an acid group (such as a carboxylic acid group) with an epoxy group, for example.

(Compound with urethane bond)
The compound having a urethane bond, which is an example of an oligomer, is preferably a compound having at least a group represented by the following formula (Ac-1) or formula (Ac-2), and the following formula (Ac-1 ) is more preferably a compound having at least a group represented by

In formulas (Ac-1) and (Ac-2), L ¹ to L ⁴ each independently represent a divalent hydrocarbon group having 2 to 20 carbon atoms, and the wavy line portion is a bonding position with another structure. represents
L ¹ to L ⁴ are each independently preferably an alkylene group having 2 to 20 carbon atoms, more preferably an alkylene group having 2 to 10 carbon atoms, and an alkylene group having 4 to 8 carbon atoms. It is even more preferable to have Further, the alkylene group may have a branched or ring structure, but is preferably a linear alkylene group.

Each wavy line portion in formula (Ac-1) or formula (Ac-2) is preferably directly bonded to the wavy line portion in the group represented by formula (Ae-1) or formula (Ae-2) below. .

In formula (Ae-1) and formula (Ae-2), R each independently represents an acryloyloxy group or a methacryloyloxy group, and the wavy line portion is the wavy line portion in formula (Ac-1) and formula (Ac-2) represents the binding position with

As the compound having a urethane bond, a compound obtained by introducing a polymerizable group through a polymer reaction into a polyurethane obtained by reacting a polyisocyanate compound and a polyol compound may be used.
For example, a compound having a urethane bond may be obtained by reacting a compound having an epoxy group and a polymerizable group with a polyurethane oligomer obtained by reacting a polyol compound having an acid group and a polyisocyanate compound.

(Compound with an ester bond)
The number of polymerizable groups in a compound having an ester bond, which is an example of an oligomer, is preferably 3 or more, more preferably 6 or more.

(Compound with epoxy residue)
As the compound having an epoxy residue, which is an example of an oligomer, a compound containing a hydroxy group in the compound is preferable.
The number of polymerizable groups in the compound having an epoxy residue is preferably 2-6, more preferably 2-3.
The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

Specific examples of oligomers are shown in the table below, but the oligomers used in the present disclosure are not limited thereto.
As the oligomer, commercially available products may be used, such as UA510H, UA-306H, UA-306I, UA-306T (all manufactured by Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, UV7620EA (all of Nippon Synthesis Kagaku Kogyo Co., Ltd.), U-15HA (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, EBECRYL860 (all manufactured by Daicel Allnex Co., Ltd.), etc. It is not limited to this.

The content of the oligomer is 30% by mass to 100% by mass with respect to the total mass of the polymerizable compounds in the image recording layer from the viewpoint of improving chemical resistance, UV printing durability, and suppression of on-press development scum. preferably 50% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[Low-molecular polymerizable compound]
The polymerizable compound may further contain a polymerizable compound other than the oligomer.
Polymerizable compounds other than oligomers are preferably low-molecular-weight polymerizable compounds from the viewpoint of chemical resistance. The low-molecular-weight polymerizable compounds may be in chemical forms such as monomers, dimers, trimers, or mixtures thereof.
Further, as the low-molecular-weight polymerizable compound, from the viewpoint of chemical resistance, at least one selected from the group consisting of a polymerizable compound having three or more ethylenically unsaturated groups and a polymerizable compound having an isocyanuric ring structure. It is preferably a chemical compound.

In the present disclosure, the low-molecular-weight polymerizable compound represents a polymerizable compound having a molecular weight (weight average molecular weight when having a molecular weight distribution) of 50 or more and less than 600.
The molecular weight of the low-molecular polymerizable compound is preferably 100 or more and less than 600, more preferably 300 or more and less than 600, from the viewpoint of excellent chemical resistance, UV printing durability, and suppression of on-press development scum. It is preferably 400 or more and less than 600, more preferably.

When the polymerizable compound contains a low-molecular-weight polymerizable compound as a polymerizable compound other than an oligomer (if two or more low-molecular-weight polymerizable compounds are included, the total amount thereof), chemical resistance, UV printing durability, and on-press From the viewpoint of suppressing development scum, the ratio of the oligomer to the low-molecular-weight polymerizable compound (oligomer/low-molecular-weight polymerizable compound) on a mass basis is preferably 10/1 to 1/10, and 10/ It is more preferably 1 to 3/7, and even more preferably 10/1 to 7/3.

Examples of low-molecular-weight polymerizable compounds include unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.) and their esters and amides, preferably , esters of unsaturated carboxylic acids and polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and polyvalent amine compounds are used. In addition, unsaturated carboxylic acid esters having a nucleophilic substituent such as a hydroxy group, an amino group, or a mercapto group, or addition reaction products of amides and monofunctional or polyfunctional isocyanates or epoxies, and monofunctional Alternatively, a dehydration condensation reaction product with a polyfunctional carboxylic acid is also preferably used. In addition, 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, and thiols, halogen atoms, Substitution reaction products of unsaturated carboxylic acid esters or amides having a leaving substituent such as a tosyloxy group with monofunctional or polyfunctional alcohols, amines and thiols are also suitable. As another example, it is also possible to use a group of compounds in which the above unsaturated carboxylic acid is replaced with unsaturated phosphonic acid, styrene, vinyl ether, or the like.
These are JP 2006-508380, JP 2002-287344, JP 2008-256850, JP 2001-342222, JP 9-179296, JP 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, Patent It is described in Japanese Laid-Open Patent Publication No. 10-333321.

Specific examples of ester monomers 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, Trimethylolpropane triacrylate, hexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate, ethylene oxide (EO) isocyanurate modified triacrylate, polyester acrylate oligomer and the like. Methacrylic acid esters such as 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.
Further, specific examples of amide monomers of polyvalent amine compounds and unsaturated carboxylic acids include methylenebisacrylamide, methylenebismethacrylamide, 1,6-hexamethylenebisacrylamide, 1,6-hexamethylenebismethacrylamide, Diethylene triamine trisacrylamide, xylylene bisacrylamide, xylylene bismethacrylamide and the like.

Urethane-based addition-polymerizable compounds produced using an addition reaction between an isocyanate and a hydroxy group are also suitable. 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 formula (M) to a polyisocyanate compound having one or more isocyanate groups. etc.
_CH2 =C( ^RM4 ) _COOCH2CH ( ^RM5 )OH (M)
In formula (M), R ^M4 and R ^M5 each independently represent a hydrogen atom or a methyl group.

In addition, the urethane acrylates described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-2003-344997, JP-A-2006-65210, JP-B-58-49860, JP-B-56-17654, JP-B-62-39417, JP-B-62-39418, JP-A-2000-250211, ethylene described in JP-A-2007-94138 Urethane compounds having an oxide skeleton, U.S. Pat. No. 7,153,632, Japanese Patent Publication No. 8-505958, JP-A-2007-293221, and urethane compounds having a hydrophilic group described in JP-A-2007-293223 are also suitable.

Details of the method of use, such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount to be added, can be set arbitrarily.
Above all, the image-recording layer preferably contains two or more polymerizable compounds from the viewpoint of UV printing durability.
The content of polymerizable compounds (the total content of polymerizable compounds when two or more polymerizable compounds are included) is preferably 5% by mass to 75% by mass with respect to the total mass of the image-recording layer. , more preferably 10% by mass to 70% by mass, and even more preferably 15% by mass to 60% by mass.

〔particle〕
The image recording layer in the present disclosure preferably contains particles from the viewpoint of developability and UV printing durability. The particles may be inorganic particles or organic particles.
Among them, the particles preferably contain organic particles, and more preferably contain resin particles.
As the inorganic particles, known inorganic particles can be used, and metal oxide particles such as silica particles and titania particles can be preferably used.

[Resin particles]
Examples of the resin particles include particles containing an addition polymerization resin (i.e., addition polymerization resin particles), particles containing a polyaddition resin (i.e., polyaddition resin particles), and particles containing a polycondensation resin (i.e., , polycondensation type resin particles), etc. Among them, addition polymerization type resin particles or polyaddition type resin particles are preferable.
Moreover, the resin particles may be particles containing a thermoplastic resin (that is, thermoplastic resin particles) from the viewpoint of enabling heat fusion.

Also, the resin particles may be in the form of microcapsules, microgels (that is, crosslinked resin particles) or the like.

The resin particles are selected from the group consisting of thermoplastic resin particles, thermoreactive resin particles, resin particles having a polymerizable group, microcapsules encapsulating a hydrophobic compound, and microgels (crosslinked resin particles). is preferred. Among them, resin particles having a polymerizable group are preferable.
In particularly preferred embodiments, the resin particles contain at least one ethylenically unsaturated group. The presence of such resin particles has the effect of improving the printing durability of the exposed areas and the on-press developability of the unexposed areas.

Thermoplastic resin particles are disclosed in Research Disclosure No. 1, 1992; 33303, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250 and European Patent No. 931647 are preferable.

Specific examples of resins constituting thermoplastic resin particles include ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, and polyalkylene structures. Homopolymers or copolymers of monomers such as acrylates or methacrylates or mixtures thereof may be mentioned.

From the viewpoint of ink receptivity and UV printing durability, the thermoplastic resin particles preferably contain a resin having structural units formed from an aromatic vinyl compound and structural units having a nitrile group.

The aromatic vinyl compound may be a compound having a structure in which a vinyl group is bonded to an aromatic ring, and examples include styrene compounds and vinylnaphthalene compounds, with styrene compounds being preferred, and styrene being more preferred.
Styrene compounds include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene. Styrene is preferred.
Examples of vinylnaphthalene compounds include 1-vinylnaphthalene, methyl-1-vinylnaphthalene, β-methyl-1-vinylnaphthalene, 4-methyl-1-vinylnaphthalene, 4-methoxy-1-vinylnaphthalene, and the like. - Vinylnaphthalene is preferred.

Moreover, as a structural unit formed from an aromatic vinyl compound, a structural unit represented by the following formula A1 is preferably exemplified.

In formula A1, R ^A1 and R ^A2 each independently represent a hydrogen atom or an alkyl group, Ar represents an aromatic ring group, R ^A3 represents a substituent, and n is an integer of 0 or more and the maximum number of substituents of Ar or less. represents
In formula A1, R ^A1 and R ^A2 are each independently preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, both of which are hydrogen atoms. is more preferred.
In Formula A1, Ar is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring.
In formula A1, R ^A3 is preferably an alkyl group or an alkoxy group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and a methyl group or a methoxy group. is more preferred.
In Formula A1, when there are multiple R ^{A3 s} , the multiple R ^A3s may be the same or different.
In formula A1, n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

From the viewpoint of ink receptivity, the content of structural units formed from the aromatic vinyl compound is preferably greater than the content of structural units having a nitrile group, which will be described later. It is more preferably 15% by mass to 85% by mass, and even more preferably 30% by mass to 70% by mass.

The structural unit having a nitrile group is preferably introduced using a monomer having a nitrile group.
Monomers having a nitrile group include acrylonitrile compounds, preferably (meth)acrylonitrile.
As the structural unit having a nitrile group, a structural unit formed from (meth)acrylonitrile is preferred.

Moreover, as a structural unit having a nitrile group, a structural unit represented by the following formula B1 is preferably exemplified.

In Formula B1, R ^B1 represents a hydrogen atom or an alkyl group.
In formula B1, R ^{1 B1} is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, even more preferably a hydrogen atom.

From the viewpoint of ink receptivity, the content of the structural unit having a nitrile group is preferably less than that formed by the aromatic vinyl compound, and is 55% by mass to 90% by mass with respect to the total mass of the resin. more preferably 60% by mass to 85% by mass.

Further, when the resin contained in the thermoplastic resin particles contains structural units formed from an aromatic vinyl compound and structural units having a nitrile group, The content ratio (structural unit formed from the aromatic vinyl compound: structural unit having a nitrile group) is preferably 5:5 to 9:1, more preferably 6:4 to 8 on a mass basis. :2.

From the viewpoint of UV printing durability and chemical resistance, the resin contained in the thermoplastic resin particles preferably further contains a structural unit formed of an N-vinyl heterocyclic compound.
Examples of N-vinyl heterocyclic compounds include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, and N- Vinylimidazoles may be mentioned, preferably N-vinylpyrrolidone.

Further, as the structural unit formed from the N-vinyl heterocyclic compound, a structural unit represented by the following formula C1 is preferably exemplified.

In Formula C1, Ar ^{2 N} represents a heterocyclic ring structure containing a nitrogen atom, and the nitrogen atom in Ar ^{2 N} is bonded to the carbon atom indicated by *.
In formula C1, the heterocyclic ring structure represented by Ar ^N is preferably a pyrrolidone ring, a carbazole ring, a pyrrole ring, a phenothiazine ring, a succinimide ring, a phthalimide ring, a caprolactam ring, and an imidazole ring, and is a pyrrolidone ring. is more preferred.
Also, the heterocyclic ring structure represented by Ar ^{2 N} may have a known substituent.

The content of the structural unit formed by the N-vinyl heterocyclic compound is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, relative to the total mass of the thermoplastic resin. more preferred.

The resin contained in the thermoplastic resin particles may contain a structural unit having an acidic group, but from the viewpoint of on-press developability and ink receptivity, it is preferable not to contain a structural unit having an acidic group. .
Specifically, the content of the structural unit having an acidic group in the thermoplastic resin is preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less. preferable. The lower limit of the content is not particularly limited, and may be 0% by mass.
The acid value of the thermoplastic resin is preferably 160 mgKOH/g or less, more preferably 80 mgKOH/g or less, and even more preferably 40 mgKOH/g or less. The lower limit of the acid value is not particularly limited, and may be 0 mgKOH/g.
In the present disclosure, the acid value is determined by a measurement method conforming to JIS K0070:1992.

From the viewpoint of ink receptivity, the resin contained in the thermoplastic resin particles may contain a structural unit containing a hydrophobic group.
Examples of the hydrophobic group include an alkyl group, an aryl group and an aralkyl group.
The structural unit containing a hydrophobic group is preferably a structural unit formed of an alkyl (meth)acrylate compound, an aryl (meth)acrylate compound, or an aralkyl (meth)acrylate compound, and a structural unit formed of an alkyl (meth)acrylate compound. is more preferred.
The number of carbon atoms in the alkyl group in the alkyl (meth)acrylate compound is preferably 1-10. The alkyl group may be linear or branched, and may have a cyclic structure. Alkyl (meth)acrylate compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and the like. is mentioned.
The aryl group in the aryl (meth)acrylate compound preferably has 6 to 20 carbon atoms, more preferably a phenyl group. Also, the aryl group may have a known substituent. Phenyl (meth)acrylate is preferably used as the aryl (meth)acrylate compound.
The number of carbon atoms in the alkyl group in the aralkyl (meth)acrylate compound is preferably 1-10. The alkyl group may be linear or branched, and may have a cyclic structure. The aryl group in the aralkyl (meth)acrylate compound preferably has 6 to 20 carbon atoms, more preferably a phenyl group. Benzyl (meth)acrylate is preferably mentioned as the aralkyl (meth)acrylate compound.

The content of the structural unit having a hydrophobic group in the resin contained in the thermoplastic resin particles is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 30% by mass, based on the total mass of the resin. It is more preferable to have

The thermoplastic resin contained in the thermoplastic resin particles preferably has a hydrophilic group from the viewpoint of UV printing durability and on-press developability.
The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxyl group, a hydroxy group, an amino group, a nitrile group, and a polyalkylene oxide structure.
From the viewpoint of UV printing durability and on-press developability, the hydrophilic group is preferably a group having a polyalkylene oxide structure, a group having a polyester structure, or a sulfonic acid group. or a sulfonic acid group, more preferably a group having a polyalkylene oxide structure.

From the viewpoint of on-press developability, the polyalkylene oxide structure is preferably a polyethylene oxide structure, a polypropylene oxide structure, or a poly(ethylene oxide/propylene oxide) structure.
From the viewpoint of on-machine developability, among the above hydrophilic groups, the polyalkylene oxide structure preferably has a polypropylene oxide structure, and more preferably has a polyethylene oxide structure and a polypropylene oxide structure.
From the viewpoint of on-machine developability, the number of alkylene oxide structures in the polyalkylene oxide structure is preferably 2 or more, more preferably 5 or more, even more preferably 5 to 200, and 8 to 150 is particularly preferred.

From the viewpoint of on-press developability, the hydrophilic group is preferably a group represented by formula Z above.
Among the hydrophilic groups possessed by thermoplastic resins, groups represented by the following formula PO are preferred.

In formula PO, each L ^P independently represents an alkylene group, R ^P represents a hydrogen atom or an alkyl group, and n represents an integer of 1-100.
In formula PO, each L ^P is independently preferably an ethylene group, a 1-methylethylene group or a 2-methylethylene group, more preferably an ethylene group.
In formula PO, R ^P is preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a hydrogen atom or 1 to 4 carbon atoms. is more preferred, and a hydrogen atom or a methyl group is particularly preferred.
In formula PO, n is preferably an integer of 1-10, more preferably an integer of 1-4.

The content of the structural unit having a hydrophilic group is preferably 5% by mass to 60% by mass, more preferably 10% by mass to 30% by mass, relative to the total mass of Resin A.

The resin contained in the thermoplastic resin particles may further contain other structural units. Other structural units may contain structural units other than the above structural units without particular limitation, and examples thereof include structural units formed from acrylamide compounds, vinyl ether compounds, and the like.
Examples of acrylamide compounds include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-butyl(meth)acrylamide, N,N'-dimethyl (Meth)acrylamide, N,N'-diethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-hydroxypropyl(meth)acrylamide, N-hydroxybutyl(meth)acrylamide and the like.
Examples of vinyl ether compounds include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, and 4-methylcyclohexyl. Methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofuran furyl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, and the like.

The content of other structural units in the thermoplastic resin is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 30% by mass, based on the total mass of the thermoplastic resin.

The glass transition temperature (Tg) of the thermoplastic resin is preferably 60° C. to 150° C., more preferably 80° C. to 140° C., and 90° C. from the viewpoint of UV printing durability and ink receptivity. More preferably ~130°C.
When the thermoplastic resin particles contain two or more thermoplastic resins, the value obtained by the FOX formula described below is called the glass transition temperature of the thermoplastic resin.

In the present disclosure, the glass transition temperature of a resin can be measured using Differential Scanning Calorimetry (DSC).
A specific measuring method is performed according to the method described in JIS K 7121 (1987) or JIS K 6240 (2011). As the glass transition temperature in this specification, an extrapolated glass transition start temperature (hereinafter sometimes referred to as Tig) is used.
A method for measuring the glass transition temperature will be described more specifically.
When determining the glass transition temperature, after holding the apparatus at a temperature about 50° C. below the expected Tg of the resin until it stabilizes, the heating rate: 20° C./min. Heat to elevated temperature and generate a differential thermal analysis (DTA) curve or DSC curve.
The extrapolated glass transition start temperature (Tig), that is, the glass transition temperature Tg in this specification, is a straight line obtained by extending the baseline on the low temperature side of the DTA curve or DSC curve to the high temperature side, and the stepwise change part of the glass transition. It is obtained as the temperature at the point of intersection with the tangent line drawn at the point where the slope of the curve is maximum.

When the thermoplastic resin particles contain two or more thermoplastic resins, the Tg of the thermoplastic resin contained in the thermoplastic resin particles is obtained as follows.
The Tg of the first thermoplastic resin is Tg1 (K), the mass fraction of the first thermoplastic resin with respect to the total mass of the thermoplastic resin components in the thermoplastic resin particles is W1, and the second Tg is Tg2. (K), and the mass fraction of the second resin with respect to the total mass of the thermoplastic resin components in the thermoplastic resin particles is W2, the Tg0 (K) of the thermoplastic resin particles is obtained by the following FOX formula: Therefore, it is possible to estimate
FOX formula: 1/Tg0 = (W1/Tg1) + (W2/Tg2)
Further, when the thermoplastic resin particles contain three kinds of resins, or three kinds of thermoplastic resin particles with different types of thermoplastic resins are contained in the pretreatment liquid, the Tg of the thermoplastic resin particles is n. When the Tg of the second resin is Tgn(K) and the mass fraction of the nth resin with respect to the total mass of the resin components in the thermoplastic resin particles is Wn, the estimation can be made according to the following formula in the same manner as above. is possible.
FOX formula: 1/Tg0 = (W1/Tg1) + (W2/Tg2) + (W3/Tg3) + (Wn/Tgn)

As used herein, Tg is a value measured by a differential scanning calorimetry (DSC). As a differential scanning calorimeter (DSC), for example, EXSTAR6220 manufactured by SII Nano Technology Co., Ltd. can be used.

The heat-reactive resin particles include resin particles having heat-reactive groups. The thermoreactive resin particles form a hydrophobized region by cross-linking due to thermal reaction and functional group change at that time.

The heat-reactive group in the resin particles having a heat-reactive group may be any functional group that performs any reaction as long as a chemical bond is formed, but is preferably a polymerizable group, examples of which include: Ethylenically unsaturated groups that undergo radical polymerization reactions (e.g., acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, etc.), cationically polymerizable groups (e.g., vinyl groups, vinyloxy groups, epoxy groups, oxetanyl groups, etc.), addition reactions An isocyanato group or a block thereof, an epoxy group, a vinyloxy group and a functional group having an active hydrogen atom that is a reaction partner of these (e.g., amino group, hydroxy group, carboxy group, etc.), a carboxy group that performs a condensation reaction, and a reaction A hydroxy group or amino group as a counterpart, an acid anhydride that undergoes a ring-opening addition reaction, and an amino group or hydroxy group as a reaction partner are preferred.
The resin having a thermoreactive group may be an addition polymerization type resin, a polyaddition type resin, a polycondensation type resin, or a thermoplastic resin.

As the microcapsule, for example, as described in JP-A-2001-277740 and JP-A-2001-277742, those encapsulating at least part of the constituent components of the image-recording layer (preferably a hydrophobic compound) are preferred. . The image-recording layer containing microcapsules as resin particles encloses hydrophobic components (i.e., hydrophobic compounds) among the components of the image-recording layer in microcapsules, and encapsulates hydrophilic components (i.e., hydrophilic compounds) in microcapsules. A configuration in which it is contained outside the capsule is a preferred embodiment.
The microgel (crosslinked resin particles) can contain part of the constituent components of the image recording layer on at least one of its surface and inside. In particular, a reactive microgel having a polymerizable group on its surface is preferable from the viewpoint of the sensitivity of the lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate.
A known synthesis method can be applied to obtain microcapsules containing the components of the image-recording layer.

The microgel (crosslinked resin particles) can contain part of the constituent components of the image recording layer on at least one of its surface and inside. In particular, a reactive microgel having a polymerizable group on its surface is preferable from the viewpoint of the sensitivity of the lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate.
A known synthesis method can be applied to obtain a microgel containing the components of the image recording layer.
or microgel

From the viewpoint of the printing durability, stain resistance and storage stability of the resulting lithographic printing plate, the resin particles are adducts of a polyhydric phenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate. Polyaddition-type resin particles obtained by reacting a polyvalent isocyanate compound and a compound having active hydrogen are preferred.
As the polyhydric phenol compound, a compound having a plurality of benzene rings with phenolic hydroxy groups is preferable.
The compound having active hydrogen is preferably a polyol compound or a polyamine compound, more preferably a polyol compound, and more preferably at least one compound selected from the group consisting of propylene glycol, glycerin and trimethylolpropane.
A polyvalent isocyanate compound which is an adduct of a polyvalent phenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate, and a resin particle obtained by the reaction of a compound having an active hydrogen are disclosed in JP-A-2012. The resin particles described in paragraphs 0032 to 0095 of JP-A-206495 are preferred.

Furthermore, from the viewpoint of printing durability and solvent resistance of the lithographic printing plate to be obtained, the resin particles have a hydrophobic main chain and i) have a nitrile group directly bonded to the hydrophobic main chain. Addition polymerizable resin particles containing both structural units and ii) structural units having pendant groups containing hydrophilic polyalkylene oxide segments are preferred.
As the hydrophobic main chain, an acrylic resin chain is preferably mentioned.
Examples of the structural unit i) above preferably include -[CH ₂ CH(C≡N)]- or -[CH ₂ C(CH ₃ )(C≡N)]-.
Also, the constituent units of i) are readily obtainable, for example, from acrylonitrile or methacrylonitrile, or from combinations thereof.

The alkylene oxide in the hydrophilic polyalkylene oxide segment of the structural unit ii) above is preferably ethylene oxide or propylene oxide, more preferably ethylene oxide.
The number of repetitions of the alkylene oxide structure is preferably 10-100, more preferably 25-75, even more preferably 40-50.

A building block having a hydrophobic backbone, both i) having a pendant cyano group directly attached to said hydrophobic backbone and ii) a building block having a pendant group comprising a hydrophilic polyalkylene oxide segment. As the addition polymerization type resin particles containing, preferred are those described in paragraphs 0039 to 0068 of JP-T-2008-503365.

Moreover, the resin particles preferably have a hydrophilic group from the viewpoint of UV printing durability and on-press developability.
The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxyl group, a hydroxy group, an amino group, a nitrile group, and a group containing a polyalkylene oxide structure.
Among them, a group containing a polyalkylene oxide structure is preferable, and a group containing a polyethylene oxide structure, a polypropylene oxide structure, or a polyethylene/propylene oxide structure is more preferable from the viewpoint of on-press developability and UV printing durability.

Further, from the viewpoint of on-press developability and suppression of development scum during on-press development, the polyalkylene oxide structure preferably has a polypropylene oxide structure, and preferably has a polyethylene oxide structure and a polypropylene oxide structure. more preferred.

Further, the hydrophilic group preferably contains a structural unit having a nitrile group or a group represented by the following formula Z, from the viewpoint of printing durability, ink receptivity, and on-press developability. It more preferably contains a structural unit represented by the following formula (AN) or a group represented by the following formula Z, and particularly preferably contains a group represented by the following formula Z.

(Structural Unit Represented by Formula (AN))
The resin particles in the present disclosure preferably have a structural unit represented by the following formula (AN) having a nitrile group as a hydrophilic group.

In formula (AN), R ^AN represents a hydrogen atom or a methyl group.

In order to introduce the structural unit represented by the formula (AN) into the resin particles, a monomer having a nitrile group may be used to synthesize a resin having a structural unit containing a cyano group (addition polymerization type resin).
(Meth)acrylonitrile is suitable as a monomer having a nitrile group.
From the viewpoint of UV printing durability, the content of the structural unit represented by the formula (AN) is preferably 5% to 90% by mass, more preferably 20% to 80% by mass, based on the total mass of the resin. %, and particularly preferably 30% by mass to 60% by mass.

(Group represented by formula Z)
The resin particles in the present disclosure preferably have a group represented by formula Z below as a hydrophilic group.
*-Q-W-Y Formula Z
In formula Z, Q represents a divalent linking group, W represents a divalent group having a hydrophilic structure or a divalent group having a hydrophobic structure, Y represents a monovalent group having a hydrophilic structure or It represents a monovalent group having a hydrophobic structure, either W or Y has a hydrophilic structure, and * represents a binding site with another structure.
Also, any one of the hydrophilic structures contained in Formula Z preferably contains a polyalkylene oxide structure.

Q in the above formula Z is preferably a divalent linking group having 1 to 20 carbon atoms, more preferably a divalent linking group having 1 to 10 carbon atoms.
In addition, Q in the above formula Z is preferably an alkylene group, an arylene group, an ester bond, an amide bond, or a group in which two or more of these are combined, and may be a phenylene group, an ester bond, or an amide bond. more preferred.

The divalent group having a hydrophilic structure in W of the above formula Z is preferably a group containing a polyalkylene oxide structure, a polyalkyleneoxy group, or _-CH CH at one end of the polyalkyleneoxy group. A group to which ₂ NR ^W — is bonded is preferred. ^RW represents a hydrogen atom or an alkyl group.
The divalent groups having a hydrophobic structure in W of the above formula Z are -R ^WA -, -OR ^WA -O-, -R ^W NR ^WA -NR ^W -, -OC(=O)- R ^WA -O- or -OC(=O)-R ^WA -O- is preferred. Each R ^WA is independently a linear, branched or cyclic alkylene group having 6 to 120 carbon atoms, a haloalkylene group having 6 to 120 carbon atoms, an arylene group having 6 to 120 carbon atoms, and an alkarylene group having 6 to 120 carbon atoms. group (a divalent group obtained by removing one hydrogen atom from an alkylaryl group) or an aralkylene group having 6 to 120 carbon atoms.

A monovalent group having a hydrophilic structure in Y of the above formula Z is —OH, —C(═O)OH, a polyalkyleneoxy group having a terminal hydrogen atom or an alkyl group, or a terminal hydrogen atom or an alkyl group It is preferably a group in which —CH ₂ CH ₂ N(R ^W )— is bonded to the other terminal of the polyalkyleneoxy group. Among them, the monovalent group having a hydrophilic structure is preferably a group containing a polyalkylene oxide structure, a polyalkyleneoxy group having a terminal hydrogen atom or an alkyl group, or a terminal hydrogen atom or an alkyl group A group in which —CH ₂ CH ₂ N(R ^W )— is bonded to the other terminal of the polyalkyleneoxy group is preferred.
The monovalent group having a hydrophobic structure in Y of the above formula Z includes a linear, branched or cyclic alkyl group having 6 to 120 carbon atoms, a haloalkyl group having 6 to 120 carbon atoms, an aryl group having 6 to 120 carbon atoms, an alkaryl group having 6 to 120 carbon atoms (alkylaryl group), an aralkyl group having 6 to 120 carbon atoms, -OR ^WB , -C(=O)OR ^WB , or -OC(=O)R ^WB preferable. R ^WB represents an alkyl group having 6 to 20 carbon atoms.

In the resin particles having a group represented by the above formula Z, W is more preferably a divalent group having a hydrophilic structure, from the viewpoint of printing durability, inking property, and on-press developability. More preferably, Q is a phenylene group, an ester bond, or an amide bond, W is a polyalkyleneoxy group, and Y is a polyalkyleneoxy group terminated with a hydrogen atom or an alkyl group.
The group represented by formula Z may function as a dispersing group that enhances the dispersibility of the resin particles.

The resin particles in the present disclosure preferably have a polymerizable group (preferably an ethylenically unsaturated group) from the viewpoint of printing durability and on-press developability, and in particular resin particles having a polymerizable group on the surface. more preferably. By using resin particles having a polymerizable group, plate skipping (preferably UV plate skipping) can be easily suppressed, and printing durability (preferably UV printing durability) can be improved.

From the viewpoint of printing durability, the resin particles in the present disclosure are preferably resin particles having a hydrophilic group and a polymerizable group.
The polymerizable group may be a cationically polymerizable group or a radically polymerizable group, but is preferably a radically polymerizable group from the viewpoint of reactivity.
The polymerizable group is not particularly limited as long as it is a polymerizable group, but from the viewpoint of reactivity, an ethylenically unsaturated group is preferable, a vinylphenyl group (styryl group), a (meth)acryloxy group, or A (meth)acrylamide group is more preferred, and a (meth)acryloxy group is particularly preferred.
Moreover, it is preferable that the resin constituting the resin particles having a polymerizable group has a constitutional unit having a polymerizable group.
A polymerizable group may be introduced onto the surface of the resin particles by a polymer reaction.

Further, the resin particles preferably contain a polyaddition type resin having a urea bond from the viewpoint of printing durability, ink receptivity, on-press developability, and suppression of development scum during on-press development. More preferably, it contains a polyaddition resin having a structure obtained by reacting at least an isocyanate compound represented by (Iso) with water, and at least reacting an isocyanate compound represented by the following formula (Iso) with water. It is particularly preferable to include a polyaddition type resin having a structure obtained by a polyoxyalkylene structure and having a polyethylene oxide structure and a polypropylene oxide structure as the polyoxyalkylene structure. Moreover, the particles containing the polyaddition type resin having a urea bond are preferably microgels.

In formula (Iso), n represents an integer of 0-10.

An example of the reaction between the isocyanate compound represented by the above formula (Iso) and water includes the reaction shown below. The following examples are examples using the n=0,4,4-isomer.
As shown below, when the isocyanate compound represented by the above formula (Iso) is reacted with water, part of the isocyanate group is hydrolyzed by the water to generate an amino group, and the generated amino group and the isocyanate group reacts to form a urea bond and form a dimer. Also, the following reaction is repeated to form a polyaddition resin having a urea bond.

In the following reaction, by adding a compound having reactivity with an isocyanate group (a compound having an active hydrogen) such as an alcohol compound or an amine compound, the structure of the alcohol compound, amine compound, etc. can be converted into polyaddition having a urea bond. It can also be introduced into the mold resin.
As the compound having active hydrogen, the compounds having active hydrogen described above are preferably used.

Moreover, the polyaddition type resin having the urea bond preferably has an ethylenically unsaturated group, and more preferably has a group represented by the following formula (PETA).

In the formula (PETA), the wavy line represents the bonding position with other structures.

(Synthesis of resin particles)
The method for synthesizing the resin particles is not particularly limited as long as it is a method capable of synthesizing particles with the various resins described above. Examples of methods for synthesizing resin particles include known methods for synthesizing resin particles, such as emulsion polymerization, suspension polymerization, dispersion polymerization, soap-free polymerization, and microemulsion polymerization.
In addition, for synthesizing the resin particles, a known method for synthesizing microcapsules, a method for synthesizing microgels (crosslinked resin particles), or the like may be used.

(Average particle size of particles)
The average particle diameter of the particles is preferably 0.01 μm to 3.0 μm, more preferably 0.03 μm to 2.0 μm, and still more preferably 0.10 μm to 1.0 μm. Good resolution and stability over time can be obtained in this range.
The average particle diameter of the particles is measured by a light scattering method, or an electron microscope photograph of the particles is taken, the particle diameters of 5,000 particles in total are measured on the photograph, and the average value is calculated. do. For non-spherical particles, the circle-equivalent diameter of the particles on the photograph is used.
Note that the average particle size of particles in the present disclosure is the volume average particle size unless otherwise specified.

Only one type of particles (preferably resin particles) may be used, or two or more types may be used in combination.

The content of the particles (preferably resin particles) is preferably 5% to 90% by mass, preferably 10% to 90% by mass, based on the total mass of the image recording layer, from the viewpoint of developability and printing durability. is more preferably 20% by mass to 90% by mass, and particularly preferably 50% by mass to 90% by mass.

[Other ingredients]
The image-recording layer in the present disclosure may contain other components than those mentioned above.
Other components include binder polymers, color formers, chain transfer agents, low-molecular-weight hydrophilic compounds, sensitizers, and other additives.

[Binder polymer]
The image-recording layer may optionally contain a binder polymer.
Here, the binder polymer refers to a polymer other than resin particles, that is, a non-particulate polymer.
Binder polymers exclude ammonium salt-containing polymers in sensitizers and polymers used as surfactants.

As the binder polymer, a known binder polymer (for example, (meth)acrylic resin, polyvinyl acetal resin, polyurethane resin, etc.) used in the image recording layer of the planographic printing plate precursor can be suitably used.
As an example, the binder polymer used for the on-press development type lithographic printing plate precursor (hereinafter also referred to as the on-press development binder polymer) will be described in detail.
As the binder polymer for on-press development, a binder polymer having an alkylene oxide chain is preferred. A binder polymer having an alkylene oxide chain may have a poly(alkylene oxide) moiety in the main chain or in a side chain. It may also be a graft polymer having poly(alkylene oxide) in a side chain, or a block copolymer of a block composed of poly(alkylene oxide)-containing repeating units and a block composed of (alkylene oxide)-free repeating units.
Polyurethane resins are preferred when having a poly(alkylene oxide) moiety in the main chain.
Examples of the polymer of the main chain when having a poly(alkylene oxide) moiety in the side chain include (meth) acrylic resins, polyvinyl acetal resins, polyurethane resins, polyurea resins, polyimide resins, polyamide resins, epoxy resins, polystyrene resins, novolak type Phenolic resins, polyester resins, synthetic rubbers and natural rubbers can be mentioned, and (meth)acrylic resins are particularly preferred.

Further, as another preferred example of the binder polymer, a polyfunctional thiol having a functionality of 6 or more and 10 or less is used as a nucleus, and it has a polymer chain bonded to this nucleus by a sulfide bond, and the polymer chain has a polymerizable group. Molecular compounds (hereinafter also referred to as star-shaped polymer compounds) can be mentioned.
As the star-shaped polymer compound, for example, compounds described in JP-A-2012-148555 can be preferably used.

The star-shaped polymer compound has a polymerizable group such as an ethylenically unsaturated bond for improving the film strength of the image area as described in JP-A-2008-195018 on the main chain or side chain, preferably on the side. Those that have chains are included. The polymerizable groups possessed by the star-shaped polymer compound form crosslinks between the molecules of the star-shaped polymer compound, promoting curing.
The polymerizable group is preferably an ethylenically unsaturated group such as a (meth)acrylic group, a vinyl group, an allyl group, a vinylphenyl group (styryl group), an epoxy group, or the like. A group (styryl group) is more preferable from the viewpoint of polymerization reactivity, and a (meth)acryl group is particularly preferable. These groups can be introduced into the polymer by polymer reaction or copolymerization. Specifically, for example, a reaction between a polymer having a carboxy group in its side chain and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be used.

The molecular weight of the binder polymer is preferably 2,000 or more, more preferably 5,000 or more, and a weight average molecular weight (Mw) of 10,000 to 300,000 in terms of polystyrene by GPC method. It is even more preferable to have

As the binder polymer, hydrophilic polymers such as polyacrylic acid and polyvinyl alcohol described in JP-A-2008-195018 can be used in combination, if necessary. Also, a lipophilic polymer and a hydrophilic polymer can be used in combination.

A binder polymer may be used individually by 1 type, and may use 2 or more types together.

The binder polymer can be contained in any amount in the image-recording layer, but the content of the binder polymer is preferably 1% by mass to 90% by mass with respect to the total mass of the image-recording layer. It is more preferably 5% by mass to 80% by mass.

[Color former]
The image-recording layer in the present disclosure preferably contains a color former, more preferably an acid color former. Moreover, it is preferable that the coloring agent contains a leuco compound.
The "color former" used in the present disclosure means a compound having a property of developing or decoloring by stimulation with light, acid, etc. to change the color of the image recording layer. It means a compound having a property of changing the color of the image-recording layer by coloring or decoloring by heating while receiving an electron-accepting compound (for example, protons of an acid, etc.). As the acid coloring agent, in particular, colorless coloring agents having partial skeletons such as lactones, lactams, sultones, spiropyrans, esters, amides, etc., and in which these partial skeletons are rapidly ring-opened or cleaved upon contact with an electron-accepting compound. Compounds are preferred.

Examples of such acid color couplers include 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (referred to as "crystal violet lactone"), 3,3-bis(4 -dimethylaminophenyl)phthalide, 3-(4-dimethylaminophenyl)-3-(4-diethylamino-2-methylphenyl)-6-dimethylaminophthalide, 3-(4-dimethylaminophenyl)-3-( 1,2-dimethylindol-3-yl)phthalide, 3-(4-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindole- 3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazole-3- yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-(4-dimethylaminophenyl)-3-(1-methylpyrrole -3-yl)-6-dimethylaminophthalide,

3,3-bis[1,1-bis(4-dimethylaminophenyl)ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1,1-bis( 4-pyrrolidinophenyl)ethylene-2-yl]-4,5,6,7-tetrabromophthalide, 3,3-bis[1-(4-dimethylaminophenyl)-1-(4-methoxyphenyl) Ethylene-2-yl]-4,5,6,7-tetrachlorophthalide, 3,3-bis[1-(4-pyrrolidinophenyl)-1-(4-methoxyphenyl)ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-diethylaminophenyl ) phthalide, 3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-N-ethyl-N-phenylaminophenyl)phthalide, 3 -(2-ethoxy-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-phthalide, 3,3-bis(1-n-octyl-2-methylindole- 3-yl)-phthalide, 3-(2-methyl-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)-phthalide and other phthalides,

4,4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, rhodamine-B-anilinolactam, rhodamine-(4-nitroanilino ) lactam, rhodamine-B-(4-chloroanilino)lactam, 3,7-bis(diethylamino)-10-benzoylphenoxazine, benzoyl leucomethylene blue, 4-nitrobenzoylmethylene blue,

3,6-dimethoxyfluorane, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3 -diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-N-cyclohexyl-Nn-butylamino-7-methylfluorane, 3-diethylamino-7- dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-di-n-hexylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-( 2′-fluorophenylamino)fluorane, 3-diethylamino-7-(2′-chlorophenylamino)fluorane, 3-diethylamino-7-(3′-chlorophenylamino)fluorane, 3-diethylamino-7-(2′,3 '-dichlorophenylamino)fluorane, 3-diethylamino-7-(3'-trifluoromethylphenylamino)fluorane, 3-di-n-butylamino-7-(2'-fluorophenylamino)fluorane, 3-di- n-butylamino-7-(2′-chlorophenylamino)fluorane, 3-N-isopentyl-N-ethylamino-7-(2′-chlorophenylamino)fluorane,

3-Nn-hexyl-N-ethylamino-7-(2'-chlorophenylamino)fluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-di-n-butylamino-6- Chloro-7-anilinofluorane, 3-diethylamino-6-methoxy-7-anilinofluorane, 3-di-n-butylamino-6-ethoxy-7-anilinofluorane, 3-pyrrolidino-6- Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-morpholino-6-methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7- Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n-pentylamino-6 -methyl-7-anilinofluorane, 3-N-ethyl-N-methylamino-6-methyl-7-anilinofluorane, 3-Nn-propyl-N-methylamino-6-methyl-7 -anilinofluorane, 3-Nn-propyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-Nn-butyl-N-methylamino-6-methyl-7-ani linofluorane, 3-Nn-butyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isobutyl-N-methylamino-6-methyl-7-anilinofluorane, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-Nn- Hexyl-N-methylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn- Propylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-butylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-hexylamino -6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-octylamino-6-methyl-7-anilinofluorane,

3-N-(2′-methoxyethyl)-N-methylamino-6-methyl-7-anilinofluorane, 3-N-(2′-methoxyethyl)-N-ethylamino-6-methyl-7 -anilinofluorane, 3-N-(2'-methoxyethyl)-N-isobutylamino-6-methyl-7-anilinofluorane, 3-N-(2'-ethoxyethyl)-N-methylamino -6-methyl-7-anilinofluorane, 3-N-(2'-ethoxyethyl)-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-(3'-methoxypropyl )-N-methylamino-6-methyl-7-anilinofluorane, 3-N-(3′-methoxypropyl)-N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3′-ethoxypropyl)-N-methylamino-6-methyl-7-anilinofluorane, 3-N-(3′-ethoxypropyl)-N-ethylamino-6-methyl-7-anilinofluor Olan, 3-N-(2′-tetrahydrofurfuryl)-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-(4′-methylphenyl)-N-ethylamino-6- Methyl-7-anilinofluorane, 3-diethylamino-6-ethyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(3′-methylphenylamino)fluorane, 3-diethylamino-6- methyl-7-(2',6'-dimethylphenylamino)fluorane, 3-di-n-butylamino-6-methyl-7-(2',6'-dimethylphenylamino)fluorane, 3-di-n -butylamino-7-(2′,6′-dimethylphenylamino)fluorane, 2,2-bis[4′-(3-N-cyclohexyl-N-methylamino-6-methylfluoran)-7-yl aminophenyl]propane, 3-[4′-(4-phenylaminophenyl)aminophenyl]amino-6-methyl-7-chlorofluorane, 3-[4′-(dimethylaminophenyl)]amino-5,7 - fluorans such as dimethylfluorane,

3-(2-methyl-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-n-propoxycarbonylamino-4-di-n -propylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-methylamino-4-di-n-propylaminophenyl)-3-(1 -ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-methyl-4-di-n-hexylaminophenyl)-3-(1-n-octyl-2-methylindole-3- yl)-4,7-diazaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl) -4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl )-3-(1-octyl-2-methylindol-3-yl)-4 or 7-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindole- 3-yl)-4 or 7-azaphthalide, 3-(2-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4 or 7-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-phenylindol-3-yl)-4 or 7-azaphthalide, 3-(2-butoxy-4-diethylaminophenyl)-3-( 1-ethyl-2-phenylindol-3-yl)-4 or 7-azaphthalide, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro- Dinaphthopyran, 3-methyl-naphtho-(3-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran-3,6-bis(dimethylamino)fluorene-9-spiro-3′-(6′-dimethylamino) phthalides such as phthalide, 3,6-bis(diethylamino)fluorene-9-spiro-3′-(6′-dimethylamino)phthalide,

Other, 2'-anilino-6'-(N-ethyl-N-isopentyl) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthen-3-one, 2'-anilino -6′-(N-ethyl-N-(4-methylphenyl))amino-3′-methylspiro[isobenzofuran-1(3H),9′-(9H)xanthene]-3-one, 3′-N ,N-dibenzylamino-6′-N,N-diethylaminospiro[isobenzofuran-1(3H),9′-(9H)xanthene]-3-one, 2′-(N-methyl-N-phenyl) amino-6′-(N-ethyl-N-(4-methylphenyl))aminospiro[isobenzofuran-1(3H),9′-(9H)xanthen]-3-one and the like.

Among them, the color former used in the present disclosure is preferably at least one compound selected from the group consisting of spiropyran compounds, spirooxazine compounds, spirolactone compounds, and spirolactam compounds from the viewpoint of color development. .
From the viewpoint of visibility, the hue of the dye after color development is preferably green, blue or black.

Moreover, the acid color former is preferably a leuco dye from the viewpoint of color development and visibility of the exposed area.
The leuco dye is not particularly limited as long as it has a leuco structure, but it preferably has a spiro structure, and more preferably has a spirolactone ring structure.
Further, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure from the viewpoint of color development and visibility of the exposed area.
Furthermore, the leuco dye having the phthalide structure or fluoran structure is a compound represented by any one of the following formulas (Le-1) to (Le-3) from the viewpoint of color development and visibility of an exposed area. and more preferably a compound represented by the following formula (Le-2).

In formulas (Le-1) to (Le-3), ERG each independently represents an electron-donating group, and X ₁ to X ₄ each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group. , X ₅ to X ₁₀ each independently represent a hydrogen atom, a halogen atom or a monovalent organic group, Y ₁ and Y ₂ each independently represent C or N, and when Y ₁ is N, When X ₁ does not exist and Y ₂ is N, X ₄ does not exist, Ra ₁ represents a hydrogen atom, an alkyl group or an alkoxy group, Rb ₁ to Rb ₄ each independently represents a hydrogen atom , represents an alkyl group or an aryl group.

The electron-donating group in ERG of formulas (Le-1) to (Le-3) includes amino group, alkylamino group, arylamino group and dialkylamino from the viewpoint of color development and visibility of exposed areas. group, monoalkylmonoarylamino group, diarylamino group, alkoxy group, aryloxy group, or alkyl group, amino group, alkylamino group, arylamino group, dialkylamino group, monoalkylmonoarylamino group , a diarylamino group, an alkoxy group, or an aryloxy group, more preferably an arylamino group, a monoalkylmonoarylamino group, or a diarylamino group, an arylamino group, or a monoalkyl A monoarylamino group is particularly preferred.
X ₁ to X ₄ in formulas (Le-1) to (Le-3) are each independently preferably a hydrogen atom or a chlorine atom from the viewpoint of color development and visibility of exposed areas. , is more preferably a hydrogen atom.
X ₅ to X ₁₀ in formula (Le-2) or formula (Le-3) are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, or a cyano group; is preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group, and more preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group. , is particularly preferably a hydrogen atom.
At least one of Y ₁ and Y ₂ in formulas (Le-1) to (Le-3) is preferably C from the viewpoint of color development and visibility of the exposed area, and Y ₁ and Y ₂ are both C more preferably.
Ra ₁ in formula (Le-3) is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and a methoxy group, from the viewpoints of color development and visibility of exposed areas. is particularly preferred.
Rb ₁ to Rb ₄ in formula (Le-1) are each independently preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, from the viewpoints of color development and visibility of exposed areas. , methyl groups are particularly preferred.

In addition, the leuco dye having the phthalide structure or the fluoran structure has the following formulas (Le-4) to (Le-4) to ( A compound represented by any one of Le-6) is more preferable, and a compound represented by the following formula (Le-5) is even more preferable.

In formulas (Le-4) to (Le-6), ERG each independently represents an electron-donating group, and X ₁ to X ₄ each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group. , Y ₁ and Y ₂ each independently represent C or N; when Y ₁ is N, X ₁ is absent; when Y ₂ is N, X ₄ is absent; ₁ represents a hydrogen atom, an alkyl group or an alkoxy group, and Rb ₁ to Rb ₄ each independently represents a hydrogen atom, an alkyl group or an aryl group.

ERG, X ₁ to X ₄ , Y ₁ , Y ₂ , Ra ₁ , and Rb ₁ to Rb ₄ in formulas (Le-4) to (Le-6) respectively correspond to formulas (Le-1) to (Le-1) to ( ERG, X ₁ to X ₄ , Y ₁ , Y ₂ , Ra ₁ and Rb ₁ to Rb ₄ in Le-3), and preferred embodiments are also the same.

Furthermore, the leuco dye having the phthalide structure or the fluoran structure has the following formula (Le-7) to the formula (Le-7) to ( A compound represented by any one of Le-9) is more preferable, and a compound represented by the following formula (Le-8) is particularly preferable.

In formulas (Le-7) to (Le-9), X ₁ to X ₄ each independently represent a hydrogen atom, a halogen atom or a dialkylanilino group, Y ₁ and Y ₂ each independently represent C or represents N, when Y ₁ is N, X ₁ does not exist, when Y ₂ is N, X ₄ does not exist, and Ra ₁ to Ra ₄ each independently represent a hydrogen atom, an alkyl or an alkoxy group, Rb ₁ to Rb ₄ each independently represent a hydrogen atom, an alkyl group or an aryl group, and Rc ₁ and Rc ₂ each independently represent an aryl group.

X ₁ to X ₄ , Y ₁ and Y ₂ in formulas (Le-7) to (Le-9) are X ₁ to X 4 , Y 1 and Y ₁ in formulas (Le-1) to (Le- ₃ ) It has the same meaning as Y ₂ , and preferred embodiments are also the same.
Ra ₁ to Ra ₄ in formula (Le-7) are each independently preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, from the viewpoints of color development and visibility of exposed areas. , methoxy groups are particularly preferred.
Rb ₁ to Rb ₄ in formulas (Le-7) to (Le-9) are each independently a hydrogen atom, an alkyl group, an alkyl group, or an alkoxy group from the viewpoint of color development and visibility of exposed areas. The group is preferably a substituted aryl group, more preferably a hydrogen atom or an alkyl group, particularly preferably a hydrogen atom or a methyl group.
Rc ₁ and Rc ₂ in formula (Le-8) are each independently preferably a phenyl group or an alkylphenyl group from the viewpoint of color development and visibility of an exposed area, and are preferably a phenyl group. is more preferred.
In formula (Le-8), X ₁ to X ₄ are preferably hydrogen atoms, and Y ₁ and Y ₂ are preferably C from the viewpoint of color development and visibility of exposed areas.
Furthermore, in formula (Le-8), from the viewpoint of color development and visibility of exposed areas, each of Rb ₁ and Rb ₂ is independently substituted with a hydrogen atom, an alkyl group, or an alkyl group or an alkoxy group. An aryl group is preferable, and a hydrogen atom or an alkyl group is more preferable.

The alkyl groups in formulas (Le-1) to (Le-9) may be linear, branched, or have a cyclic structure.
Further, the number of carbon atoms in the alkyl group in formulas (Le-1) to (Le-9) is preferably 1 to 20, more preferably 1 to 8, and further preferably 1 to 4. 1 or 2 is particularly preferred.
The number of carbon atoms in the aryl group in formulas (Le-1) to (Le-9) is preferably 6-20, more preferably 6-10, and particularly preferably 6-8.

Further, each group such as a monovalent organic group, an alkyl group, an aryl group, a dialkylanilino group, an alkylamino group, and an alkoxy group in formulas (Le-1) to (Le-9) has a substituent. may be Examples of substituents include alkyl groups, aryl groups, halogen atoms, amino groups, alkylamino groups, arylamino groups, dialkylamino groups, monoalkylmonoarylamino groups, diarylamino groups, hydroxy groups, alkoxy groups, aryloxy groups, and acyl groups. groups, alkoxycarbonyl groups, aryloxycarbonyl groups, cyano groups, and the like. Moreover, these substituents may be further substituted by these substituents.

As the leuco dye having a phthalide structure or a fluoran structure, which is preferably used, the following compounds can be mentioned.

It is also possible to use commercially available products as acid color formers, such as ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H -3035, BLUE203, ATP, H-1046, H-2114 (manufactured by Fukui Yamada Chemical Industry Co., Ltd.), ORANGE-DCF, Vermilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF , TH-107 (manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green -118, Red-40, Red-8 (manufactured by Yamamoto Kasei Co., Ltd.), and Crystal Violet Lactone (manufactured by Tokyo Chemical Industry Co., Ltd.). Among these commercial products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63 , GN-169, and crystal violet lactone are preferred because the films formed have good visible light absorption.

Preferred leuco dyes include the following compounds from the viewpoint of color development and visibility of exposed areas.

These color formers may be used singly or in combination of two or more.
The content of the coloring agent is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 5% by mass, relative to the total mass of the image recording layer.

[Chain transfer agent]
The image-recording layer used in the present disclosure may contain a chain transfer agent. A chain transfer agent contributes to improving the printing durability of a lithographic printing plate.
As the chain transfer agent, a thiol compound is preferable, a thiol having 7 or more carbon atoms is more preferable from the viewpoint of boiling point (hardness to volatilize), and a compound having a mercapto group on an aromatic ring (aromatic thiol compound) is more preferable. The thiol compound is preferably a monofunctional thiol compound.

Specific examples of chain transfer agents include the following compounds.

Chain transfer agents may be added alone or in combination of two or more.
The content of the chain transfer agent is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 40% by mass, and 0.1% by mass to 30% by mass, relative to the total mass of the image recording layer. % is more preferred.

[Low molecular weight hydrophilic compound]
The image-recording layer may contain a low-molecular-weight hydrophilic compound in order to improve developability while suppressing deterioration in printing durability. The low-molecular-weight hydrophilic compound is preferably a compound with a molecular weight of less than 1,000, more preferably a compound with a molecular weight of less than 800, and even more preferably a compound with a molecular weight of less than 500.
Low-molecular-weight hydrophilic compounds include, for example, water-soluble organic compounds such as glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol, 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 alkyl sulfuric acid and alkyl ether sulfuric acid and salts thereof, organic phosphonic acids such as phenylphosphonic acid and salts thereof, tartaric acid, oxalic acid, citric acid Acids, malic acid, lactic acid, gluconic acid, organic carboxylic acids such as amino acids and salts thereof, and betaines.

At least one selected from the group consisting of polyols, organic sulfates, organic sulfonates and betaines is preferably contained as the low-molecular-weight hydrophilic compound.

Specific examples of organic sulfonates include alkylsulfonates such as sodium n-butylsulfonate, sodium n-hexylsulfonate, sodium 2-ethylhexylsulfonate, sodium cyclohexylsulfonate and sodium n-octylsulfonate; , Sodium 8,11-trioxapentadecane-1-sulfonate, Sodium 5,8,11-trioxaheptadecane-1-sulfonate, 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 sodium, sodium p-styrenesulfonate, dimethyl isophthalate-5-sodium sulfonate, sodium 1-naphthylsulfonate, sodium 4-hydroxynaphthylsulfonate, disodium 1,5-naphthalenedisulfonate, 1,3,6- Examples thereof include arylsulfonates such as trisodium naphthalenetrisulfonate, and compounds described in paragraphs 0026 to 0031 of JP-A-2007-276454 and paragraphs 0020-0047 of JP-A-2009-154525. The salt may be potassium salt, lithium salt.

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

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

Since the hydrophobic portion of the low-molecular-weight hydrophilic compound has a small structure and little surface activity, dampening water permeates into the exposed portion (image portion) of the image recording layer, reducing the hydrophobicity and film strength of the image portion. The ink receptivity and printing durability of the image recording layer can be maintained satisfactorily.

The content of the low-molecular-weight hydrophilic compound is preferably 0.5% to 20% by mass, more preferably 1% to 15% by mass, and 2% to 10% by mass, relative to the total mass of the image-recording layer. is more preferred. Within this range, good developability and printing durability can be obtained.
The low-molecular-weight hydrophilic compounds may be used singly or in combination of two or more.

[Oleosensitizer]
The image-recording layer may contain an oil-sensitizing agent such as a phosphonium compound, a nitrogen-containing low-molecular-weight compound, an ammonium group-containing polymer, etc., in order to improve ink receptivity. In particular, when the inorganic layered compound is contained in the protective layer, these compounds function as a surface coating agent for the inorganic layered compound, and can suppress the deterioration of the ink receptivity during printing due to the inorganic layered compound.
As the oil-sensitizing agent, it is preferable to use a phosphonium compound, a nitrogen-containing low-molecular-weight compound, and an ammonium group-containing polymer in combination. is more preferred.

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

Nitrogen-containing low-molecular-weight compounds include amine salts and quaternary ammonium salts. Also included are imidazolinium salts, benzimidazolinium salts, pyridinium salts, and quinolinium salts. Among them, quaternary ammonium salts and pyridinium salts are preferred. Specific examples include tetramethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, dodecyltrimethylammonium p-toluenesulfonate, benzyltriethylammonium hexafluorophosphate, benzyldimethyloctylammonium hexafluorophosphate. Phate, benzyldimethyldodecyl ammonium hexafluorophosphate, and compounds described in paragraphs 0021 to 0037 of JP-A-2008-284858 and paragraphs 0030-0057 of JP-A-2009-90645.

The ammonium group-containing polymer may have an ammonium group in its structure, and is preferably a polymer containing 5 mol % to 80 mol % of a (meth)acrylate having an ammonium group in its side chain as a copolymerization component. Specific examples include polymers described in paragraphs 0089 to 0105 of JP-A-2009-208458.

The ammonium salt-containing polymer preferably has a reduced specific viscosity (unit: ml/g) value in the range of 5 to 120, more preferably in the range of 10 to 110. is more preferred, and those in the range of 15 to 100 are particularly preferred. When the reduced specific viscosity is converted to a weight average molecular weight (Mw), it is preferably 10,000 to 150,0000, more preferably 17,000 to 140,000, and particularly preferably 20,000 to 130,000.

Specific examples of the ammonium group-containing polymer are shown below.
(1) 2-(trimethylammonio)ethyl methacrylate = p-toluenesulfonate/3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90, Mw 45,000)
(2) 2-(trimethylammonio)ethyl methacrylate = hexafluorophosphate/3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(3) 2-(ethyldimethylammonio)ethyl methacrylate = p-toluenesulfonate/hexyl methacrylate copolymer (molar ratio 30/70, Mw 45,000)
(4) 2-(trimethylammonio)ethyl methacrylate = hexafluorophosphate/2-ethylhexyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(5) 2-(trimethylammonio)ethyl methacrylate = methyl sulfate/hexyl methacrylate copolymer (molar ratio 40/60, Mw 70,000)
(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-(Butyldimethylammonio)ethyl methacrylate = hexafluorophosphate/3,6-dioxaheptyl methacrylate/2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer (molar ratio 15/80/5, Mw 65,000)

The content of the oil sensitizing agent is preferably 0.01% by mass to 30.0% by mass, more preferably 0.1% by mass to 15.0% by mass, and 1% by mass with respect to the total mass of the image recording layer. % to 10% by mass is more preferred.

[Other additives]
The image-recording layer may contain surfactants, higher fatty acid derivatives, plasticizers, inorganic stratiform compounds, and the like as other components. Specifically, the description in paragraphs 0114 to 0159 of JP-A-2008-284817 can be referred to.
A polymerization inhibitor may be used in the image recording layer of the present disclosure as long as the above effects are not impaired.

[Formation of image recording layer]
The image recording layer in the lithographic printing plate precursor according to the present disclosure, for example, as described in paragraphs 0142 to 0143 of JP-A-2008-195018, the necessary components are dispersed or dissolved in a known solvent and coated. It can be formed by preparing a liquid, coating the coating liquid on the support by a known method such as bar coating, and drying.
A known solvent can be used as the solvent. Specifically, for example, water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3- Methoxy-1-propanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N,N-dimethyl formamide, dimethylsulfoxide, γ-butyrolactone, methyl lactate, ethyl lactate and the like. A solvent may be used individually by 1 type, and may use 2 or more types together. The solid content concentration in the coating liquid is preferably about 1 to 50% by mass.
The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer, it is 0.3 g/m ² to 3.0 g/m 2 . ^m2 is preferred.

<Support>
A lithographic printing plate precursor according to the present disclosure has a support.
The support can be appropriately selected from known lithographic printing plate precursor supports and used.
As the support, a support having a hydrophilic surface (hereinafter also referred to as "hydrophilic support") is preferable.
The support in the lithographic printing plate precursor according to the present disclosure preferably has a contact angle with water of 110° or less by the water droplet method on the surface of the support on the image-recording layer side, from the viewpoint of suppressing damage and staining. , more preferably 90° or less, more preferably 80° or less, even more preferably 50° or less, particularly preferably 30° or less, more preferably 20° or less. It is particularly preferred, and 10 or less is most preferred.

In the present disclosure, the contact angle with water on the surface of the support on the image recording layer side by the water drop method in air is measured by the following method.
The lithographic printing plate precursor is immersed in a solvent capable of removing the image-recording layer (for example, the solvent used in the coating solution for the image-recording layer), and the image-recording layer is scraped off with at least a sponge or cotton to remove the image-recording layer. Dissolving in a solvent exposes the surface of the aluminum support.
The contact angle with water on the exposed surface of the image recording layer of the aluminum support was measured at 25° C. using a fully automatic contact angle meter (eg, DM-501 manufactured by Kyowa Interface Science Co., Ltd.). is measured as the contact angle of a water drop (after 0.2 seconds).

As the support in the present disclosure, an aluminum plate roughened by a known method and anodized is preferred. That is, the support in the present disclosure preferably has an aluminum plate and an aluminum anodized coating disposed on the aluminum plate.

An example of a preferred embodiment of the support used in the present disclosure (also referred to as "support (1)") is shown below.
That is, the support (1) has an aluminum plate and an aluminum anodized film disposed on the aluminum plate, and the anodized film is positioned closer to the image recording layer than the aluminum plate. The anodized film has micropores extending in the depth direction from the surface on the image recording layer side, and the average diameter of the micropores on the surface of the anodized film is more than 10 nm and 100 nm or less, and the anodized film The value of lightness L ^* in the L ^* a ^* b ^* color system of the surface of the film on the image recording layer side is 70-100.

FIG. 1 is a schematic cross-sectional view of one embodiment of an aluminum support 12a.
The aluminum support 12a has a laminated structure in which an aluminum plate 18 and an aluminum anodized film 20a (hereinafter also simply referred to as "anodized film 20a") are laminated in this order. The anodized film 20a in the aluminum support 12a is located closer to the image recording layer than the aluminum plate 18 is. That is, the lithographic printing plate precursor according to the present disclosure preferably has at least an anodized film, an image recording layer, and a water-soluble resin layer in this order on an aluminum plate.

-Anodized film-
Preferred aspects of the anodized film 20a are described below.
The anodized film 20a is a film formed on the surface of the aluminum plate 18 by anodizing treatment, and this film is substantially perpendicular to the film surface and has extremely fine micropores 22a that are uniformly distributed. have The micropores 22a extend along the thickness direction (aluminum plate 18 side) from the surface of the anodized film 20a on the image recording layer side (the surface of the anodized film 20a opposite to the aluminum plate 18 side).

The average diameter (average opening diameter) of the micropores 22a in the anodized film 20a on the surface of the anodized film is preferably more than 10 nm and not more than 100 nm. Among them, from the viewpoint of the balance between printing durability, stain resistance, and image visibility, 15 nm to 60 nm is more preferable, 20 nm to 50 nm is still more preferable, and 25 nm to 40 nm is particularly preferable. The diameter inside the pore may be wider or narrower than the surface layer.
When the average diameter exceeds 10 nm, printing durability and image visibility are further improved. Moreover, when the average diameter is 100 nm or less, the printing durability is further improved.
The average diameter of the micropores 22a was 400 nm×600 nm in the four images obtained by observing N=4 sheets of the surface of the anodized film 20a with a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times. The diameter (diameter) of micropores present in the range of is measured at 50 points and calculated as an arithmetic mean value.
If the shape of the micropores 22a is not circular, the circle equivalent diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle having the same projected area as the projected area of the opening.

The depth of the micropores 22a is not particularly limited, but is preferably 10 nm to 3,000 nm, more preferably 50 nm to 2,000 nm, even more preferably 300 nm to 1,600 nm.
The above depth is a value obtained by taking a photograph of the cross section of the anodized film 20a (magnification of 150,000), measuring the depths of 25 or more micropores 22a, and averaging them.

The shape of the micropores 22a is not particularly limited, and in FIG. 1, it is substantially straight tubular (substantially cylindrical), but it may be conical in which the diameter decreases in the depth direction (thickness direction). The shape of the bottom of the micropore 22a is not particularly limited, and may be curved (convex) or flat.

The value of lightness L ^* in the L ^* a ^* b ^* color system of the surface of the aluminum support 12a on the image recording layer side (the surface of the anodized film 20a on the image recording layer side) is preferably 70 to 100. . Among them, 75 to 100 is preferable, and 75 to 90 is more preferable, in terms of better balance between printing durability and image visibility.
The lightness L ^* is measured using a color difference meter, Spectro Eye, manufactured by X-Rite Co., Ltd.

In the support (1), the micropores communicate with the large-diameter portion extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm and the bottom portion of the large-diameter portion. and a small-diameter pore extending to a position of 20 nm to 2,000 nm, the average diameter of the large-diameter pore on the surface of the anodized film being 15 nm to 150 nm, and the average diameter of the small-diameter pore at the communicating position. is 13 nm or less (also referred to as "support (2)").
FIG. 2 is a schematic cross-sectional view of an alternative embodiment of the aluminum support 12a to that shown in FIG.
In FIG. 2, the aluminum support 12b includes an aluminum plate 18 and an anodized film 20b having micropores 22b composed of large-diameter pore portions 24 and small-diameter pore portions .
The micropores 22b in the anodized film 20b communicate with the large-diameter hole portion 24 extending from the surface of the anodized film to a depth of 10 nm to 1000 nm (depth D: see FIG. 2) and the bottom portion of the large-diameter hole portion 24. and a small-diameter hole 26 extending from the communication position to a depth of 20 nm to 2,000 nm.
The large-diameter hole portion 24 and the small-diameter hole portion 26 will be described in detail below.

The average diameter of the large-diameter hole portion 24 on the surface of the anodized film 20b is the same as the average diameter of the micropores 22a in the anodized film 20a on the surface of the anodized film 20a described above, and is more than 10 nm and not more than 100 nm, and the preferred range is also the same. is.
The method for measuring the average diameter on the surface of the anodized film 20b of the large-diameter hole portion 24 is the same as the method for measuring the average diameter on the surface of the anodized film of the micropores 22a in the anodized film 20a.

The bottom of the large-diameter hole 24 is located at a depth of 10 nm to 1,000 nm (hereinafter also referred to as depth D) from the surface of the anodized film. That is, the large-diameter hole portion 24 is a hole portion extending from the surface of the anodized film to a position of 10 nm to 1,000 nm in the depth direction (thickness direction). The depth is preferably 10 nm to 200 nm.
The above depth is a value obtained by taking a photograph of the cross section of the anodized film 20b (magnified by 150,000), measuring the depths of 25 or more large-diameter holes 24, and averaging them.

The shape of the large-diameter hole portion 24 is not particularly limited. preferable.

As shown in FIG. 2, the small-diameter hole portion 26 is a hole portion that communicates with the bottom portion of the large-diameter hole portion 24 and extends further in the depth direction (thickness direction) from the communicating position.
The average diameter at the communicating position of the small-diameter hole portion 26 is preferably 13 nm or less. Among them, 11 nm or less is preferable, and 10 nm or less is more preferable. Although the lower limit is not particularly limited, it is often 5 nm or more.

The average diameter of the small-diameter pore portions 26 is obtained by observing N=4 sheets of the surface of the anodized film 20a with an FE-SEM at a magnification of 150,000 times, and micropores existing in the range of 400 nm × 600 nm in the obtained 4 images. The diameter (diameter) of the (small-diameter pore) is measured and obtained as an arithmetic mean value. If the large-diameter hole is deep, the upper portion of the anodized film 20b (the area where the large-diameter hole is located) is cut (for example, by argon gas), and then the anodized film 20b is cut. The surface may be observed with the above FE-SEM to determine the average diameter of the small-diameter pores.
In addition, when the shape of the small-diameter hole portion 26 is not circular, the circle equivalent diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle having the same projected area as the projected area of the opening.

The bottom portion of the small-diameter hole portion 26 is located at a location extending 20 nm to 2,000 nm further in the depth direction from the communicating position with the large-diameter hole portion 24 . In other words, the small-diameter hole portion 26 is a hole portion extending in the depth direction (thickness direction) from the position communicating with the large-diameter hole portion 24, and the depth of the small-diameter hole portion 26 is 20 nm to 2,000 nm. . The depth is preferably 500 nm to 2,000 nm.
The above depth is a value obtained by taking a photograph of the cross section of the anodized film 20b (magnification of 50,000), measuring the depths of 25 or more small-diameter holes, and averaging them.

The shape of the small-diameter hole portion 26 is not particularly limited, and includes, for example, a substantially straight tubular shape (substantially columnar shape) and a conical shape in which the diameter decreases in the depth direction, and a substantially straight tubular shape is preferred.

-Method for producing support-
As a method for manufacturing the support used in the present disclosure, for example, a manufacturing method in which the following steps are performed in order is preferable.
・Roughening treatment step: a step of roughening an aluminum plate ・Anodizing treatment step: a step of anodizing a roughened aluminum plate ・Pore widening treatment step: the anode obtained in the anodizing treatment step Step of contacting an aluminum plate having an oxide film with an aqueous acid solution or an aqueous alkali solution to expand the diameter of micropores in the anodized film. The procedures of each step are described in detail below.

[Roughening treatment step]
The graining treatment step is a step of subjecting the surface of the aluminum plate to graining treatment including electrochemical graining treatment. This step is preferably performed before the anodizing treatment step, which will be described later.

Graining treatment may be performed only by electrochemical graining treatment, but may be performed in combination with electrochemical graining treatment and mechanical graining treatment and/or chemical graining treatment. You may
When the mechanical graining treatment and the electrochemical graining treatment are combined, it is preferable to perform the electrochemical graining treatment after the mechanical graining treatment.
The electrochemical graining treatment is preferably carried out in an aqueous solution mainly containing nitric acid or hydrochloric acid using direct current or alternating current.
The method of mechanical graining treatment is not particularly limited, but includes, for example, the method described in Japanese Patent Publication No. 50-40047.
The chemical graining treatment is also not particularly limited, and includes known methods.

After the mechanical graining treatment, the following chemical etching treatment is preferably carried out.
The chemical etching treatment applied after the mechanical roughening treatment smoothes the uneven edges of the surface of the aluminum plate, prevents ink from being caught during printing, and improves the stain resistance of the printing plate. , to remove debris such as abrasive particles remaining on the surface.
The chemical etching treatment includes etching with an acid and etching with an alkali, and a chemical etching treatment using an alkaline aqueous solution (hereinafter also referred to as "alkaline etching treatment") is mentioned as a method that is particularly excellent in terms of etching efficiency. be done.

The alkaline agent used in the alkaline aqueous solution is not particularly limited, and examples thereof include caustic soda, caustic potash, sodium metasilicate, sodium carbonate, sodium aluminate, and sodium gluconate.
The alkaline aqueous solution may contain aluminum ions.
The concentration of the alkaline agent in the alkaline aqueous solution is preferably 0.01% by mass or more, more preferably 3% by mass or more, and preferably 30% by mass or less.

When alkali etching treatment is performed, it is preferable to perform chemical etching treatment (hereinafter also referred to as "desmutting treatment") using a low-temperature acidic aqueous solution in order to remove products generated by the alkali etching treatment.
Acids used in the acidic aqueous solution are not particularly limited, and examples thereof include sulfuric acid, nitric acid, and hydrochloric acid. Further, the temperature of the acidic aqueous solution is preferably 20°C to 80°C.

As the surface roughening treatment step, a method of carrying out the treatments shown in A mode or B mode in the following order is preferable.

~ A mode ~
(2) Chemical etching treatment using an alkaline aqueous solution (first alkaline etching treatment)
(3) Chemical etching treatment using an acidic aqueous solution (first desmutting treatment)
(4) Electrochemical graining treatment using an aqueous solution mainly containing nitric acid (first electrochemical graining treatment)
(5) Chemical etching treatment using alkaline aqueous solution (second alkaline etching treatment)
(6) Chemical etching treatment using an acidic aqueous solution (second desmutting treatment)
(7) Electrochemical graining treatment in aqueous solution mainly composed of hydrochloric acid (second electrochemical graining treatment)
(8) Chemical etching treatment using alkaline aqueous solution (third alkali etching treatment)
(9) Chemical etching treatment using an acidic aqueous solution (third desmutting treatment)

~ B mode ~
(10) Chemical etching treatment using alkaline aqueous solution (fourth alkali etching treatment)
(11) Chemical etching treatment using an acidic aqueous solution (fourth desmutting treatment)
(12) Electrochemical Graining Treatment Using an Aqueous Solution Mainly Containing Hydrochloric Acid (Third Electrochemical Graining Treatment)
(13) Chemical etching treatment using alkaline aqueous solution (fifth alkaline etching treatment)
(14) Chemical etching treatment using an acidic aqueous solution (fifth desmutting treatment)

(1) Mechanical surface roughening treatment may be performed before the treatment of (2) of Aspect A or before the treatment of (10) of Aspect B, if necessary.

The amount of aluminum plate dissolved in the first alkali etching treatment and the fourth alkali etching treatment is preferably 0.5 g/m ² to 30 g/m ² , more preferably 1.0 g/m ² to 20 g/m ² .

Examples of the aqueous solution containing nitric acid as a main component used in the first electrochemical graining treatment in A mode include aqueous solutions used in electrochemical graining treatment using direct current or alternating current. For example, an aqueous solution obtained by adding aluminum nitrate, sodium nitrate, or ammonium nitrate to an aqueous nitric acid solution of 1 to 100 g/L can be mentioned.
As the aqueous solution mainly containing hydrochloric acid used in the second electrochemical graining treatment in A mode and the third electrochemical graining treatment in B mode, a normal electrochemical roughening treatment using direct current or alternating current Aqueous solutions used for chemical treatment are mentioned. For example, an aqueous solution obtained by adding 0 g/L to 30 g/L of sulfuric acid to a hydrochloric acid aqueous solution of 1 g/L to 100 g/L can be mentioned. Nitrate ions such as aluminum nitrate, sodium nitrate and ammonium nitrate; and hydrochloride ions such as aluminum chloride, sodium chloride and ammonium chloride may be further added to this solution.

A sinusoidal wave, a rectangular wave, a trapezoidal wave, a triangular wave, or the like can be used as the AC power waveform for the electrochemical graining treatment. The frequency is preferably 0.1 Hz to 250 Hz.
FIG. 3 is a graph showing an example of an alternating waveform current waveform diagram used for electrochemical graining treatment.
In FIG. 3, ta is the anode reaction time, tc is the cathode reaction time, tp is the time from 0 to the peak of the current, Ia is the peak current on the anode cycle side, and Ic is the peak current on the cathode cycle side. , AA is the current of the anodic reaction of the aluminum plate, and CA is the current of the cathodic reaction of the aluminum plate. In the trapezoidal wave, the time tp from 0 to the peak of the current is preferably 1 ms to 10 ms. The conditions for one cycle of alternating current used for electrochemical roughening are that the ratio tc/ta of the anode reaction time ta to the cathode reaction time tc of the aluminum plate is 1 to 20, the amount of electricity Qc when the aluminum plate is the anode, and the anode It is preferable that the ratio Qc/Qa of the quantity of electricity Qa at the time is in the range of 0.3 to 20, and the anode reaction time ta is in the range of 5 ms to 1,000 ms. The current density is preferably 10 A/dm ² to 200 A/dm ² at the peak value of the trapezoidal wave on both the anode cycle side Ia and the cathode cycle side Ic. Ic/Ia is preferably 0.3-20. The total amount of electricity that participates in the anode reaction of the aluminum plate at the time when the electrochemical graining is completed is preferably 25 C/dm ² to 1,000 C/dm ² .

The apparatus shown in FIG. 4 can be used for electrochemical graining using alternating current.
FIG. 4 is a side view showing an example of a radial type cell in electrochemical graining treatment using alternating current.
4, 50 is a main electrolytic cell, 51 is an AC power supply, 52 is a radial drum roller, 53a and 53b are main electrodes, 54 is an electrolyte supply port, 55 is an electrolyte, 56 is a slit, 57 is an electrolyte passage, 58 is an auxiliary anode, 60 is an auxiliary anode tank, and W is an aluminum plate. In FIG. 4, arrow A1 indicates the direction of supply of the electrolytic solution, and arrow A2 indicates the direction of discharge of the electrolytic solution. is. When two or more electrolytic cells are used, the electrolysis conditions may be the same or different.
An aluminum plate W is wound around a radial drum roller 52 immersed in a main electrolytic bath 50 and electrolyzed by main electrodes 53a and 53b connected to an AC power supply 51 during transportation. The electrolyte 55 is supplied from the electrolyte supply port 54 through the slit 56 to the electrolyte passage 57 between the radial drum roller 52 and the main electrodes 53a and 53b. The aluminum plate W treated in the main electrolytic bath 50 is then electrolytically treated in the auxiliary anode bath 60 . An auxiliary anode 58 is disposed facing the aluminum plate W in the auxiliary anode bath 60, and an electrolytic solution 55 is supplied so as to flow through the space between the auxiliary anode 58 and the aluminum plate W. As shown in FIG.

The amount of dissolution of the aluminum plate in the second alkali etching treatment is preferably 1.0 g/m ² or more, more preferably 2.0 g/m ² to 10 g/m ² , from the viewpoint of easy production of a predetermined printing plate precursor.

The amount of dissolution of the aluminum plate in the third alkali etching treatment and the fourth alkali etching treatment is preferably 0.01 g/m ² to 0.8 g/m ² , and 0.05 g, in terms of facilitating the production of a predetermined printing plate precursor. /m ² to 0.3 g/m ² is more preferable.

In the chemical etching treatment using an acidic aqueous solution (first to fifth desmutting treatments), an acidic aqueous solution containing phosphoric acid, nitric acid, sulfuric acid, chromic acid, hydrochloric acid, or a mixed acid containing two or more of these acids is preferably used.
The acid concentration of the acidic aqueous solution is preferably 0.5% by mass to 60% by mass.

[Anodizing process]
The procedure of the anodizing treatment step is not particularly limited as long as the micropores described above can be obtained, and known methods can be used.
In the anodizing process, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, or the like can be used as an electrolytic bath. For example, the concentration of sulfuric acid can be 100 g/L to 300 g/L.
The conditions for ^the anodizing treatment are appropriately set depending on the electrolytic solution used ^. (preferably 1 A/dm ² to 60 A/dm ² ), voltage 1 V to 100 V (preferably 5 V to 50 V), electrolysis time 1 second to 100 seconds (preferably 5 seconds to 60 seconds), and coating amount 0.1 g /m ² to 5 g/m ² (preferably 0.2 g/m ² to 3 g/m ² ).

[Pore widening treatment]
The pore widening treatment is a treatment (pore diameter enlarging treatment) for enlarging the diameters of micropores (pore diameters) present in the anodized film formed by the anodizing treatment process described above.
The pore widening treatment can be performed by bringing the aluminum plate obtained by the above-described anodizing treatment process into contact with an acid aqueous solution or an alkaline aqueous solution. The contacting method is not particularly limited, and examples thereof include dipping and spraying.

<Undercoat layer>
The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (sometimes called an intermediate layer) between the image-recording layer and the support. The undercoat layer strengthens the adhesion between the support and the image-recording layer in the exposed areas, and facilitates the separation of the image-recording layer from the support in the unexposed areas. contribute to improving Moreover, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, and thus has the effect of preventing the heat generated by exposure from diffusing into the support and lowering the sensitivity.

Compounds used in the undercoat layer include polymers having an adsorptive group capable of being adsorbed to the support surface and a hydrophilic group. A polymer having an adsorptive group, a hydrophilic group, and a crosslinkable group is preferred in order to improve adhesion to the image-recording layer. The compound used in the undercoat layer may be a low-molecular-weight compound or a polymer. The compounds used for the undercoat layer may be used in combination of two or more, if necessary.

When the compound used for the undercoat layer is a polymer, it is preferably a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group.
Adsorptive groups capable of being adsorbed on the support surface include phenolic hydroxy group, carboxy group, -PO ₃ H ₂ , -OPO ₃ H ₂ , -CONHSO ₂ -, -SO ₂ NHSO ₂ -, and -COCH ₂ COCH _{3 .} is preferred. The hydrophilic group is preferably a sulfo group or a salt thereof, or a salt of a carboxy group. As the crosslinkable group, an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, and the like are preferable.
The polymer may have a polar substituent of the polymer and a crosslinkable group introduced by salt formation with a compound having a polar substituent, a countercharged substituent, and an ethylenically unsaturated bond. Other monomers, preferably hydrophilic monomers, may be further copolymerized.

Specifically, a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679, and an ethylenic divalent compound described in JP-A-2-304441. Phosphorus compounds having a heavy bond reactive group are preferred. JP-A-2005-238816, JP-A-2005-125749, JP-A-2006-239867, and JP-A-2006-215263, a crosslinkable group (preferably an ethylenically unsaturated bond group) described in each publication, a support Low-molecular-weight or high-molecular-weight compounds having surface-interacting functional groups and hydrophilic groups are also preferably used.
More preferred are polymers having an adsorptive group, a hydrophilic group and a crosslinkable group capable of being adsorbed to the surface of a support, as described in JP-A-2005-125749 and JP-A-2006-188038.

The content of ethylenically unsaturated bond groups in the polymer used for the undercoat layer is preferably 0.1 mmol to 10.0 mmol, more preferably 0.2 mmol to 5.5 mmol, per 1 g of polymer.
The weight average molecular weight (Mw) of the polymer used for the undercoat layer is preferably 5,000 or more, more preferably 10,000 to 300,000.

[Hydrophilic compound]
From the viewpoint of developability, the undercoat layer preferably contains a hydrophilic compound.
The hydrophilic compound is not particularly limited, and known hydrophilic compounds used for the undercoat layer can be used.
Preferred examples of the hydrophilic compound include carboxymethylcellulose, phosphonic acids having an amino group such as dextrin, organic phosphonic acids, organic phosphoric acids, organic phosphinic acids, amino acids, and hydrochlorides of amines having a hydroxyl group.
Further, as the hydrophilic compound, a compound having an amino group or a functional group capable of inhibiting polymerization and a group interacting with the support surface (for example, 1,4-diazabicyclo[2.2.2]octane (DABCO) , 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, ethylenediaminetetraacetic acid (EDTA) or its salts, hydroxyethylethylenediaminetriacetic acid or its salts, dihydroxyethylethylenediaminediacetic acid or its salts, hydroxy ethyliminodiacetic acid or a salt thereof, etc.).

The hydrophilic compound preferably contains a hydroxycarboxylic acid or a salt thereof from the viewpoint of preventing stains.
In addition, a hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, is preferably contained in the layer on the aluminum support from the viewpoint of anti-scratching property. The layer on the aluminum support is preferably a layer on the side where the image recording layer is formed, and is preferably a layer in contact with the aluminum support.
As the layer on the aluminum support, the layer in contact with the aluminum support is preferably an undercoat layer or an image-recording layer. A layer other than the layer in contact with the aluminum support, such as a protective layer or an image-recording layer, may contain a hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof.
In the lithographic printing plate precursor according to the present disclosure, the image-recording layer preferably contains a hydroxycarboxylic acid or a salt thereof from the viewpoint of preventing stains.
In addition, in the lithographic printing plate precursor according to the present disclosure, an embodiment in which the surface of the aluminum support on the image-recording layer side is surface-treated with a composition (e.g., an aqueous solution, etc.) containing at least a hydroxycarboxylic acid or a salt thereof is also preferred. be done. In the above embodiment, at least a portion of the treated hydroxycarboxylic acid or its salt is detected in a state of being contained in a layer (e.g., image recording layer or undercoat layer) on the image recording layer side in contact with the aluminum support. be able to.
By including hydroxycarboxylic acid or a salt thereof in a layer such as an undercoat layer on the side of the image recording layer in contact with the aluminum support, the surface of the aluminum support on the side of the image recording layer can be made hydrophilic. The contact angle with water on the surface of the image-recording layer can be easily made 110° or less by the water droplet method in air, and it is excellent in scratch/fouling suppressing properties.

Hydroxycarboxylic acid is a general term for organic compounds having one or more carboxy groups and one or more hydroxy groups in one molecule, and is also called hydroxy acid, oxy acid, oxycarboxylic acid, and alcoholic acid ( Iwanami Rikagaku Jiten 5th Edition, published by Iwanami Shoten Co., Ltd. (1998)).
The above hydroxycarboxylic acid or salt thereof is preferably represented by the following formula (HC).
R ^HC (OH) _mhc (COOM ^HC ) _nhc formula (HC)
In formula (HC), ^RHC represents an mhc+nhc valent organic group, ^MHC each independently represents a hydrogen atom, an alkali metal or onium, mhc and nhc each independently represents an integer of 1 or more, n is 2 or more, M may be the same or different.

In the formula (HC), the mhc+nhc valent organic group represented by R includes an mhc+nhc valent hydrocarbon group and the like. The hydrocarbon group may have substituents and/or linking groups.
Hydrocarbon groups include mhc+nhc valent groups derived from aliphatic hydrocarbons, such as alkylene groups, alkanetriyl groups, alkanetetrayl groups, alkanepentyl groups, alkenylene groups, alkenetriyl groups, and alkenetetrayl groups. groups, alkenepentyl groups, alkynylene groups, alkynetriyl groups, alkynetetrayl groups, alkynepentyl groups, and other mhc+nhc valent groups derived from aromatic hydrocarbons, e.g., arylene groups, arenetriyl groups, arenes Examples include a tetrayl group and an arenepentyl group. Examples of substituents other than hydroxyl groups and carboxyl groups include alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, and aryl groups. Specific examples of substituents include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, hexadecyl group, octadecyl group, eicosyl group, isopropyl group, isobutyl group, s-butyl group, t-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl group, 2-norbornyl group, methoxymethyl group, methoxyethoxyethyl group, allyloxymethyl group, phenoxymethyl group, acetyloxymethyl group, benzoyloxymethyl group, benzyl group, phenethyl group, α-methylbenzyl group, 1- methyl-1-phenylethyl group, p-methylbenzyl group, cinnamyl group, allyl group, 1-propenylmethyl group, 2-butenyl group, 2-methylallyl group, 2-methylpropenylmethyl group, 2-propynyl group, 2- butynyl group, 3-butynyl group, phenyl group, biphenyl group, naphthyl group, tolyl group, xylyl group, mesityl group, cumenyl group, methoxyphenyl group, ethoxyphenyl group, phenoxyphenyl group, acetoxyphenyl group, benzoyloxyphenyl group , methoxycarbonylphenyl group, ethoxycarbonylphenyl group, phenoxycarbonylphenyl group and the like. Further, the linking group is composed of at least one atom selected from the group consisting of a hydrogen atom, a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom and a halogen atom, and the number of atoms thereof is preferably 1 to 50. is. Specific examples include an alkylene group, a substituted alkylene group, an arylene group, a substituted arylene group, etc., and these divalent groups are linked by any of an amide bond, an ether bond, a urethane bond, a urea bond and an ester bond. You may have a structure that is

Alkali metals represented by ^MHC include lithium, sodium, potassium and the like, with sodium being particularly preferred. Onium includes ammonium, phosphonium, sulfonium and the like, with ammonium being particularly preferred.
In addition, from the viewpoint of antifouling property, ^MHC is preferably an alkali metal or an onium, more preferably an alkali metal.
The total number of mhc and nhc is preferably 3 or more, more preferably 3-8, even more preferably 4-6.

The hydroxycarboxylic acid or its salt preferably has a molecular weight of 600 or less, more preferably 500 or less, and particularly preferably 300 or less. Moreover, the molecular weight is preferably 76 or more.
The hydroxycarboxylic acid or the hydroxycarboxylic acid constituting the hydroxycarboxylic acid salt is specifically gluconic acid, glycolic acid, lactic acid, tartronic acid, hydroxybutyric acid (2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, etc.), malic acid, tartaric acid, citramaric acid, citric acid, isocitric acid, leucic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineraidic acid, cerebronic acid, quinic acid, shikimic acid, monohydroxybenzoic acid derivatives (salicylic acid, creosote acid (homosalicylic acid, hydroxy(methyl)benzoic acid), vanillic acid, syringic acid, etc.), dihydroxybenzoic acid derivatives (pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, orceric acid, etc.), trihydroxy Benzoic acid derivatives (gallic acid, etc.), phenylacetic acid derivatives (mandelic acid, benzilic acid, atrolactinic acid, etc.), hydrocinnamic acid derivatives (melilotic acid, phloretic acid, coumaric acid, umberic acid, caffeic acid, ferulic acid, sinapic acid, cerebronic acid, carminic acid, etc.).

Among these, the hydroxycarboxylic acid or the hydroxycarboxylic acid constituting the salt of the hydroxycarboxylic acid is preferably a compound having two or more hydroxy groups from the viewpoint of suppressing stains and stains. are more preferred, compounds having 5 or more hydroxy groups are more preferred, and compounds having 5 to 8 hydroxy groups are particularly preferred.
As those having one carboxyl group and two or more hydroxy groups, gluconic acid or shikimic acid is preferable.
Citric acid or malic acid is preferable as one having two or more carboxy groups and one hydroxy group.
Tartaric acid is preferable as one having two or more carboxyl groups and two or more hydroxy groups.
Among them, gluconic acid is particularly preferable as the hydroxycarboxylic acid.

A hydrophilic compound may be used individually by 1 type, or may use 2 or more types together.
When the undercoat layer contains a hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, the content of the hydrophilic compound, preferably a hydroxycarboxylic acid and a salt thereof, is 0.01 wt% to the total weight of the undercoat layer. It is preferably 50 mass %, more preferably 0.1 mass % to 40 mass %, and particularly preferably 1.0 mass % to 30 mass %.

The undercoat layer may contain a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, etc., in addition to the above-mentioned undercoat layer compounds, to prevent stains over time.

The subbing layer is applied by known methods. The coating amount (solid content) of the undercoat layer is preferably 0.1 mg/m ² to 100 mg/m ² , more preferably 1 mg/m ² to 30 mg/m ² .

<Protective layer>
The lithographic printing plate precursor according to the present disclosure may have a protective layer (sometimes called an overcoat layer) between the image-recording layer and the outermost layer. The protective layer has the function of inhibiting the image formation inhibiting reaction by blocking oxygen, and also has the function of preventing scratches on the image recording layer and preventing abrasion during high-intensity laser exposure.

Protective layers having such properties are described, for example, in US Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. As the low-oxygen-permeable polymer used in 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. can. Specific examples include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, water-soluble cellulose derivatives, poly(meth)acrylonitrile, and the like.
Acid-modified polyvinyl alcohol having a carboxy group or a sulfo group is preferably used as the modified polyvinyl alcohol. Specific examples include modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137.

The protective layer preferably contains an inorganic stratiform compound in order to improve oxygen barrier properties. The inorganic stratiform compound is a particle having a thin _tabular shape. light, zirconium phosphate and the like.
A preferred inorganic stratiform compound is a mica compound. Examples of mica compounds include compounds of the formula: A(B,C) _2-5 D ₄ O ₁₀ (OH,F,O) ₂ [wherein A is any one of K, Na and Ca, and B and C are Fe(II), Fe(III), Mn, Al, Mg, or V, and D is Si or Al. ] and a group of mica such as natural mica and synthetic mica.

In the mica group, natural micas include muscovite, soda mica, phlogopite, biotite and lepidite. Synthetic mica includes _non -swelling mica such as fluorine phlogopite _KMg3 ( _AlSi3O10 ) _F2 , potash tetrasilicon mica _{KMg2.5Si4O10 ) F2} , _and Na tetrasilic mica NaMg2 _{. 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 /} Swellable mica such as ₅ Li _1/8 (Si ₄ O ₁₀ )F ₂ and the like are included. Also useful are synthetic smectites.

Among the above mica compounds, fluorine-based swelling mica is particularly useful. That is, the swelling synthetic mica has a layered structure consisting of unit crystal lattice layers with a thickness of about 10 Å to 15 Å (1 Å=0.1 nm), and the metal atom substitution in the lattice is significantly larger than that of other clay minerals. As a result, the lattice layer has a shortage of positive charges, and to compensate for this, cations such as Li ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ are adsorbed between the layers. The cations interposed between these layers are called exchangeable cations and can be exchanged with various cations. In particular, when the cations between the layers are Li ⁺ or Na ⁺ , the bond between the layered crystal lattices is weak due to their small ionic radii, resulting in large swelling with water. When shear is applied in this state, it is easily cleaved to form a stable sol in water. Swellable synthetic mica has a strong tendency toward this and is particularly preferably used.

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

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

The content of the inorganic layered compound is preferably 1% by mass to 60% by mass, more preferably 3% by mass to 50% by mass, based on the total solid content of the protective layer. Even when multiple types of inorganic layered compounds are used in combination, the total amount of the inorganic layered compounds is preferably the above content. Within the above range, the oxygen blocking property is improved and good sensitivity is obtained. In addition, it is possible to prevent a decrease in ink receptivity.

The protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coatability, and inorganic particles for controlling surface slipperiness. In addition, the protective layer may contain the oil sensitizing agent described for the image recording layer.

The protective layer is applied by known methods. The coating amount (solid content) of the protective layer is preferably 0.01 g/m ² to 10 g/m ² , more preferably 0.02 g/m ² to 3 g/m ² , and 0.02 g/m ² to 1 g/m 2 . ² is particularly preferred.

<<Method for preparing lithographic printing plate and method for lithographic printing>>
A lithographic printing plate can be prepared by imagewise exposing and developing the lithographic printing plate precursor according to the present disclosure.
The method for preparing a lithographic printing plate according to the present disclosure includes a step of imagewise exposing the lithographic printing plate precursor according to the present disclosure (hereinafter also referred to as an “exposure step”), and a printing ink and dampening solution. and a step of removing the image recording layer in the non-image portion on the printing press (hereinafter also referred to as "on-press development step").
The lithographic printing method according to the present disclosure includes a step of imagewise exposing the lithographic printing plate precursor according to the present disclosure (exposure step), and printing by supplying at least one selected from the group consisting of printing ink and dampening water. a step of removing the image recording layer in the non-image areas on-press to prepare a lithographic printing plate (on-press development step); a step of printing with the obtained lithographic printing plate (hereinafter also referred to as a "printing step"); is preferably included.
Preferred aspects of each step of the method for preparing a lithographic printing plate according to the present disclosure and the lithographic printing method according to the present disclosure will be described below in order. The lithographic printing plate precursor according to the present disclosure can also be developed with a developer.
The exposure step and the on-press development step in the method for preparing a lithographic printing plate will be described below. The on-press development step in the method for preparing a lithographic printing plate according to the present disclosure is the same step as the on-press development step in the lithographic printing method according to the present disclosure.
In addition, it is presumed that the outermost layer is partly removed during on-press development and partly remains on the surface of the image area or penetrates into the interior of the image area due to the printing ink.

<Exposure process>
The method of preparing a lithographic printing plate according to the present disclosure preferably includes an exposure step of imagewise exposing the lithographic printing plate precursor according to the present disclosure to form an exposed portion and an unexposed portion. The lithographic printing plate precursor according to the present disclosure is preferably subjected to laser exposure through a transparent original image having a line image, halftone image, or the like, or imagewise exposure by laser beam scanning or the like using digital data.
The wavelength of the light source is preferably 750 nm to 1,400 nm. As the light source with a wavelength of 750 nm to 1,400 nm, solid-state lasers and semiconductor lasers that emit infrared rays are suitable. As for the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably within 20 microseconds, and the irradiation energy amount is preferably 10 mJ/cm ² to 300 mJ/cm ² . preferable. Also, it is preferable to use a multi-beam laser device to shorten the exposure time. The exposure mechanism may be an internal drum system, an external drum system, a flat bed system, or the like.
Imagewise exposure can be carried out by a conventional method using a plate setter or the like. In the case of on-press development, imagewise exposure may be performed on the printing press after the lithographic printing plate precursor is mounted on the printing press.

<On-machine development process>
The method of preparing a lithographic printing plate according to the present disclosure includes an on-press development step of supplying at least one selected from the group consisting of printing ink and dampening water to remove the image recording layer in the non-image area on the printing press. preferably included.
The on-machine development method will be described below.

[On-machine development method]
In the on-press development method, an image-exposed lithographic printing plate precursor is supplied with an oil-based ink and an aqueous component on a printing press, and the image-recording layer in the non-image areas is removed to prepare a lithographic printing plate. is preferred.
That is, after the lithographic printing plate precursor is exposed imagewise, it is mounted on the printing press as it is without undergoing any development treatment, or after the lithographic printing plate precursor is mounted on the printing press, it is imagewise exposed on the printing press and then When the oil ink and the aqueous component are supplied for printing, in the initial stage of printing, in the non-image area, the uncured image recording layer is formed by either or both of the supplied oil ink and the aqueous component. It dissolves or disperses and is removed, exposing the hydrophilic surface at that portion. On the other hand, in the exposed area, the image-recording layer cured by exposure forms an oil-based ink receiving area having a lipophilic surface. Either the oil-based ink or the water-based component may be supplied to the printing plate first. is preferred. In this manner, the lithographic printing plate precursor is developed on-press on the printing press and used as it is for printing a large number of sheets. As the oil-based ink and the water-based component, printing ink and dampening water for ordinary lithographic printing are preferably used.

As a laser for image exposure of the lithographic printing plate precursor according to the present disclosure, a light source with a wavelength of 750 nm to 1,400 nm is preferably used. The light source with a wavelength of 750 nm to 1,400 nm is preferably used as described above.

<Developing solution development process>
The method of preparing a lithographic printing plate according to the present disclosure includes the steps of imagewise exposing the lithographic printing plate precursor of the present disclosure, and the steps of removing the image recording layer in the non-image area with a developer to prepare the lithographic printing plate ( (also referred to as a "developing solution development step").
Further, the lithographic printing method according to the present disclosure comprises a step of imagewise exposing the lithographic printing plate precursor according to the present disclosure, a step of removing the image recording layer in the non-image area with a developer to prepare a lithographic printing plate, and a step of printing with the obtained lithographic printing plate.
A known developer can be used as the developer.
The pH of the developer is not particularly limited, and may be a strong alkaline developer, but a developer having a pH of 2 to 11 is preferred. As a developer having a pH of 2 to 11, for example, a developer containing at least one of a surfactant and a water-soluble polymer compound is preferably used.
In the development processing using a strong alkaline developer, the protective layer is removed in the pre-washing step, then alkali development is performed, the alkali is removed by washing in the post-washing step, gum solution treatment is performed, and drying is performed in the drying step. is mentioned.
Further, when the developer containing a surfactant or a water-soluble polymer compound is used, development and gum solution treatment can be carried out simultaneously. Therefore, the post-washing step is not particularly required, and the drying step can be performed after the development and the gum solution treatment are performed with one solution. Furthermore, since the removal of the protective layer can be carried out at the same time as the development and the treatment with the gum solution, a pre-washing step is not particularly required. After the development treatment, it is preferable to dry after removing excess developer using a squeeze roller or the like.

<Printing process>
A lithographic printing method according to the present disclosure includes a printing step of supplying printing ink to a lithographic printing plate to print a recording medium.
The printing ink is not particularly limited, and various known inks can be used as desired. Moreover, as printing ink, an oil-based ink or an ultraviolet curing ink (UV ink) is preferably mentioned.
In the printing process, dampening water may be supplied as necessary.
Further, the printing process may be performed continuously with the on-press development process or the developer development process without stopping the printing press.
The recording medium is not particularly limited, and any known recording medium can be used as desired.

In the method for preparing a lithographic printing plate from the lithographic printing plate precursor according to the present disclosure and the lithographic printing method according to the present disclosure, if necessary, before exposure, during exposure, and between exposure and development, lithographic printing The entire surface of the plate precursor may be heated. Such heating promotes the image forming reaction in the image recording layer, and can bring about advantages such as improvement in sensitivity and printing durability, stabilization of sensitivity, and the like. Heating before development is preferably carried out under mild conditions of 150° C. or less. With the above aspect, problems such as hardening of the non-image portion can be prevented. It is preferred to use very strong conditions for post-development heating, preferably in the range of 100°C to 500°C. Within the above range, a sufficient image strengthening action can be obtained, and problems such as deterioration of the support and thermal decomposition of the image area can be suppressed.

EXAMPLES The present disclosure will be described in detail below with reference to Examples, but the present disclosure is not limited to these. In the present examples, "%" and "parts" mean "% by mass" and "parts by mass", respectively, unless otherwise specified.
In the structures shown below, "OMe" represents a methoxy group.

[Examples 1 to 14, Comparative Examples 1 to 3]
<Preparation of support>
For an aluminum alloy plate of material 1S with a thickness of 0.3 mm, (Aa) mechanical roughening treatment (brush grain method) described in paragraph 0126 of JP-A-2012-158022 to paragraph 0134. (Ai) A desmutting treatment was performed in an acidic aqueous solution.
Next, each treatment condition from (Aj) first stage anodizing treatment described in paragraph 0135 of JP-A-2012-158022 to (Am) third stage anodizing treatment described in paragraph 0138 is adjusted appropriately to have a large-diameter pore with an average system of 35 nm and a depth of 100 nm and a small-diameter pore with an average diameter of 10 nm and a depth of 1,000 nm, and the large-diameter pore with respect to the average diameter of the large-diameter pore An anodized film having a depth ratio of 2.9 was formed, and an aluminum support A was obtained.
In addition, water washing treatment was performed between all the treatment steps, and after the water washing treatment, liquid was drained off with nip rollers.

<Formation of lithographic printing plate precursor>
An undercoat layer coating solution having the following composition was coated on the aluminum support A (printed surface side) so that the dry coating amount was 87 mg/m ² to form an undercoat layer.
Subsequently, an image-recording layer coating solution having the following composition was bar-coated on the undercoat layer and oven-dried at 120° C. for 40 seconds to form an image-recording layer having a dry coating amount of 0.971 g/m ² . got the original.
The image-recording layer coating solution containing resin particles (microgel) was prepared by mixing and stirring a photosensitive solution containing components other than the following microgel solution and the following microgel solution immediately before coating.

<Coating solution for undercoat layer>
・The following undercoat layer compound (P-1): 0.1370 parts ・Sodium gluconate: 0.0700 parts ・Surfactant (Emarex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts ・Preservative (Biohope L, manufactured by K.I Kasei Co., Ltd.): 0.00149 parts Water: 3.29000 parts

<Image recording layer coating solution>
・Infrared absorber (compound listed in Table 1): amount (parts) listed in Table 1
・Radical-induced polymerization inhibitor precursor (compound listed in Table 1): amount (parts) listed in Table 1
- Electron-donating polymerization initiator (B-1, the following compound, HOMO: -5.92 eV): 0.025 parts - Electron-accepting polymerization initiator (I-1, the following compound, LUMO: -3.02 eV): 0.110 parts Polymerizable compound (Shin-Nakamura Chemical Co., Ltd., U-15HA): 0.245 parts Color former (R-1, the following compound, leuco dye): 0.02 parts Anionic surfactant (A -1, the following compound): 0.006 parts Fluorinated surfactant (W-1, the following compound): 0.004 parts 1-methoxy-2-propanol (MFG): 4.50 parts Methyl ethyl ketone (MEK ): 4.35 parts Methanol: 2.30 parts Microgel liquid (prepared by the following method): 0.400 parts in solid form

<Preparation of microgel solution>
• Microgel (crosslinked resin particles): 2.640 parts • Distilled water: 2.425 parts A method for preparing the microgel used in the above microgel liquid is shown below.

-Preparation of polyvalent isocyanate compound-
Bismatris (2-ethyl hexanoate) (Neostan U-600, Nitto Kasei Co., Ltd.) 0.043 part was added and stirred. When the heat generation subsided, the reaction temperature was set to 50° C. and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50% by mass) of polyvalent isocyanate compound (1).

- Preparation of microgel -
The following oil phase component and water phase component were mixed and emulsified using a homogenizer at 12,000 rpm for 10 minutes. After stirring the obtained emulsion at 45° C. for 4 hours, 10 masses of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) % aqueous solution was added, stirred at room temperature for 30 minutes, and allowed to stand at 45° C. for 24 hours. Distilled water was added to adjust the solid content concentration to 20% by mass to obtain an aqueous microgel dispersion. The average particle size of the microgel measured by a light scattering method was 0.28 µm.

~Oil phase component~
(Component 1) Ethyl acetate: 12.0 parts (Component 2) Trimethylolpropane (6 molar equivalents) and xylene diisocyanate (18 molar equivalents) are added, and to this, one-end methylated polyoxyethylene (1 molar equivalent, oxy Repetition number of ethylene units: 90) (50% by mass ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.): 3.76 parts (Component 3) Polyvalent isocyanate compound (1) (50% by mass of acetic acid As an ethyl solution): 15.0 parts (Component 4) 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer): 11.54 parts (Component 5) Sulfonate surfactant (Pionin A-41-C, manufactured by Takemoto Oil & Fat Co., Ltd.) in 10% ethyl acetate solution: 4.42 parts

~ Aqueous Phase Component ~
Distilled water: 46.87 parts

<Evaluation>
(1) UV printing durability. Exposure was performed under the condition of 400 dpi (dots per inch, 1 inch is 2.54 cm) (equivalent to irradiation energy of 110 mJ/cm ² ). The exposure image includes a solid image and a 10% halftone dot chart of AM screen (Amplitude Modulation Screen).
The obtained exposed original plate was mounted on a chrysanthemum-size cylinder of Heidelberg SX-74 printing machine without being subjected to development processing. A 100-liter dampening solution circulation tank containing a non-woven fabric filter and a temperature control device was connected to this printing machine. 80 L of dampening water S-Z1 (manufactured by Fuji Film Co., Ltd.) containing 2.0% dampening water was charged into the circulation device, and T&K UV OFS K-HS Black GE-M (manufactured by T&K TOKA Co., Ltd.) was used as the printing ink. ), and after supplying dampening water and ink by the standard automatic printing start method, Tokubishi art paper (ream weight: 76.5 kg, manufactured by Mitsubishi Paper Mills Co., Ltd.) at a printing speed of 10,000 sheets per hour. 500 sheets were printed.
Further printing was carried out. As the number of printed sheets increased, the ink density on the printed matter decreased due to the gradual wear of the image area. The number of printed copies when the halftone dot area ratio of the 10% halftone dots of the AM screen in the printed matter measured by a Gretag densitometer (manufactured by GretagMacbeth) is 3% lower than the measured value of the 500th printed sheet is defined as the number of printed sheets. The printing durability was evaluated.
The relative printing durability was evaluated according to the following criteria, with 100 representing the number of printed sheets of 50,000. The higher the numerical value, the better the printing durability. The evaluation results are shown in Table 2.
Relative printing durability = (number of prints of target lithographic printing plate precursor)/50,000 x 100
-Evaluation criteria-
A: The value of relative printing durability exceeds 90 B: The value of relative printing durability exceeds 75 and is 90 or less C: The value of relative printing durability is 75 or less

(2) On-machine developability The lithographic printing plate precursor prepared as described above is exposed using a Kodak Magnus 800 Quantum equipped with an infrared semiconductor laser under the conditions of an output of 27 W, an outer drum rotation speed of 450 rpm, and a resolution of 2,400 dpi. (equivalent to irradiation energy of 110 mJ/cm ² ). The exposure image includes a solid image and AM screen (Amplitude Modulation Screen) 50% halftone dot chart.
The obtained exposed original plate was mounted on a chrysanthemum-size cylinder of Heidelberg SX-74 printing machine without being subjected to development processing. A 100-liter dampening solution circulation tank containing a non-woven fabric filter and a temperature control device was connected to this printing machine. 80 L of dampening water S-Z1 (manufactured by Fuji Film Co., Ltd.) containing 2.0% dampening water was charged into the circulation device, and T&K UV OFS K-HS Black GE-M (manufactured by T&K TOKA Co., Ltd.) was used as the printing ink. ), and after supplying dampening water and ink by the standard automatic printing start method, Tokubishi art paper (ream weight: 76.5 kg, manufactured by Mitsubishi Paper Mills Co., Ltd.) at a printing speed of 10,000 sheets per hour. 200 sheets were printed.
In the on-press development, the number of sheets of printing paper required until ink was not transferred to the non-image area was measured as the on-press developability. It can be said that the smaller the number of sheets, the better the on-machine developability.
-Evaluation criteria-
A: The number of sheets of printing paper required until ink was not transferred to the non-image area was 20 or less.
B: The number of sheets of printing paper required until ink was not transferred to the non-image area was 20 or more and less than 50 sheets.
C: The number of sheets of printing paper required until ink was not transferred to the non-image area was 50 or more.

(3) streak-like unevenness, the lithographic printing plate precursor prepared as described above,
Using an exposure machine (PlateRite HD 8900N series, manufactured by SCREEN Graphic Solution Co., Ltd.) equipped with an exposure head employing GLV (Grating Light Value) technology, exposure was performed at an exposure energy of 110 mJ/cm ² . The exposure image included a 200-line AM screen and a 20 μm FM screen (Frequency Modulation Screen) chart.
The exposed original plate thus obtained was mounted on a SOR-M monochrome printing machine (manufactured by Heidelberg) without being subjected to development processing. 2% dilution (manufactured by Fuji Film Co., Ltd.), blanket: DAY Blanket D 3000 (manufactured by T&K TOKA Co., Ltd.), paper: Tokubishi Art 127.9 gsm (manufactured by Mitsubishi Paper Mills Co., Ltd.), 1,000 I printed a copy. Then, sensory evaluation was performed on the degree of occurrence of streak-like unevenness by visual observation from the surface of the 1,000th printed sheet. It is also said that the more streak-like unevenness is seen, the better the suitability for GLV.
-Evaluation criteria-
A: No streak-like unevenness is observed on both the FM screen and the AM screen.
B: Slight streak-like unevenness is observed only on the FM screen.
C: Slight streak-like unevenness is observed on both the FM screen and the AM screen.
D: Striped unevenness is observed on both the FM screen and the AM screen.

Details of each component used in the image recording layer are shown below.

[Infrared absorber]
IR-1: compound with the following structure (HOMO = -5.35 eV, LUMO = -3.75 eV)
IR-2: compound with the following structure (HOMO = -5.27 eV, LUMO = -3.66 eV)
IR-3: compound with the following structure (HOMO = -5.38 eV, LUMO = -3.80 eV)
IR-4: compound with the following structure (HOMO = -5.38 eV, LUMO = -3.77 eV)

[Radical Induced Polymerization Inhibitor Precursor and Polymerization Inhibitor]
・G-1 to G-8: compounds having the following structures, provided that n and m in G-7 below indicate the molar ratio of repeating units to which n and m are attached, and n is 1 mol% to 50 mol % and m is 50 mol % to 99 mol %.
・MEHQ: p-methoxyphenol

From the results shown in Table 1, according to the lithographic printing plate precursors of Examples 1 to 14, which are the lithographic printing plate precursors according to the present disclosure, lithographic printing plates in which streak-like unevenness is suppressed can be obtained. Even when ink is used, a lithographic printing plate having excellent printing durability can be obtained.
Further, from the results shown in Table 1, the lithographic printing plate precursors of Examples 1 to 14, which are the lithographic printing plate precursors according to the present disclosure, are also excellent in on-press developability.

18: aluminum plate, ta: anode reaction time, tc: cathode reaction time, tp: time from 0 to peak current, Ia: current at peak on anode cycle side, Ic: peak time on cathode cycle side Current, AA: current of anodic reaction of aluminum plate, CA: current of cathodic reaction of aluminum plate, 12a, 12b: aluminum support, 22a, 22b: micropores, 24: large-diameter pore, 26: small-diameter pore, D: depth of large-diameter hole, 50: main electrolytic bath, 51: AC power supply, 52: radial drum roller, 53a, 53b: main pole, 54: electrolyte supply port, 55: electrolyte, 56: slit, 57: Electrolyte passage, 58: Auxiliary anode, 60: Auxiliary anode tank, W: Aluminum plate, A1: Liquid supply direction, A2: Electrolyte discharge direction

Claims (13)

having a support and an image-recording layer formed on the support;
The image recording layer contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound, and a radical-induced polymerization inhibitor precursor,
The on-press development type lithographic plate, wherein the content ratio A/B of the content A of the infrared absorbing agent and the content B of the radical-induced polymerization inhibitor precursor is 0.1 to 2.5 on a mass basis. Original printing plate. The on-press development type lithographic printing plate precursor as claimed in Claim 1, wherein the radical-induced polymerization inhibitor precursor is a compound having a radical scavenging site and a polymerization-inhibiting precursor site. The on-press development type lithographic printing plate precursor as claimed in claim 2, wherein the radical scavenging site is a site containing an ethylenically unsaturated double bond. The on-press development type lithographic printing plate precursor as claimed in Claim 3, wherein the site containing an ethylenically unsaturated double bond is a (meth)acryloxy group. The on-press development type lithographic printing plate precursor according to claim 4, wherein the polymerization-inhibited precursor site is a site containing a hydroxyl group. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 5, wherein the radical-induced polymerization inhibitor precursor is a compound containing a partial structure represented by the following formula (1). .

In formula (1), Ra each independently represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aryl group; Rb represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; , represents a (meth)acryloxy group. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 6, wherein the polymerization initiator comprises an electron-donating polymerization initiator and an electron-accepting polymerization initiator. 8. The on-press development type lithographic printing plate precursor as claimed in claim 7 , wherein the HOMO of the infrared absorber-the HOMO of the electron-donating polymerization initiator is 0.70 eV or less. The on-press development type lithographic printing plate precursor according to claim 7 or 8 , wherein a value of LUMO of the electron-accepting polymerization initiator - LUMO of the infrared absorber is 0.80 eV or less. The on-press development type lithographic printing plate precursor according to any one of Claims 1 to 9 , wherein the polymerizable compound is a polymerizable compound having a functionality of 7 or more. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 10, wherein the polymerizable compound is a polymerizable compound having a functionality of 10 or more. a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 11 ;
supplying at least one selected from the group consisting of printing ink and dampening water on a printing press to remove the image-recording layer in the non-image areas. a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 11 ;
a step of supplying at least one selected from the group consisting of printing ink and dampening water to remove the image-recording layer in the non-image areas on a printing press to prepare a lithographic printing plate;
and printing with the obtained lithographic printing plate.