WO2021241688A1

WO2021241688A1 - Original plate for on-machine development type lithographic printing plate, lithographic printing plate manufacturing method, and lithographic printing method

Info

Publication number: WO2021241688A1
Application number: PCT/JP2021/020203
Authority: WO
Inventors: 康平會津; 和朗榎本; 一郎小山; 彬阪口; 昌山本
Original assignee: 富士フイルム株式会社
Priority date: 2020-05-29
Filing date: 2021-05-27
Publication date: 2021-12-02
Also published as: EP4159441A4; EP4159441A1; CN115666958A

Abstract

Provided are an original plate for an on-machine development type lithographic printing plate, that comprises a support, an image recording layer, and an outermost layer in this order, the image recording layer including a polymerization initiator, a polymerizable compound, and an infrared absorber, and a decomposition rate of the infrared absorber after storing for 8 hours in an environment with an ozone concentration of 150 ppb being 50% or less, a lithographic printing plate manufacturing method using the original plate for a lithographic printing plate, and a lithographic printing method.

Description

Machine-developed lithographic printing plate original plate, lithographic printing plate manufacturing method, and lithographic printing method

This disclosure relates to an on-machine development type lithographic printing plate original plate, a method for producing a lithographic printing plate, and a lithographic printing method.

Generally, a lithographic printing plate comprises a lipophilic image portion that receives ink in the printing process and a hydrophilic non-image portion that receives dampening water. In flat plate printing, the property that water and oil-based ink repel each other is used to make the oil-based image part of the flat plate printing plate an ink receiving part and the hydrophilic non-image part a dampening water receiving part (that is, ink non-receptive part). As a part), it is a method of causing a difference in the adhesiveness of ink on the surface of a flat plate printing plate, inking the ink only on the image part, and then transferring the ink to an object to be printed such as paper for printing.
In order to produce this lithographic printing plate, conventionally, a lithographic printing plate original plate (also referred to as PS plate) in which a lipophilic photosensitive resin layer (also referred to as an image recording layer) is provided on a hydrophilic support has been widely used. ing. Normally, after the lithographic printing plate original plate is exposed through an original image such as a squirrel film, the portion that becomes the image portion of the image recording layer remains, and the other unnecessary image recording layer is an alkaline developer or organic. A lithographic printing plate is obtained by performing plate making by a method of dissolving and removing with a solvent to expose the surface of a hydrophilic support to form a non-image portion.

In addition, due to growing interest in the global environment, environmental issues related to waste liquids associated with wet treatments such as development treatments have been highlighted.
In response to the above environmental problems, simplification or non-processing of development or plate making is aimed at. One of the simple methods for producing a lithographic printing plate is a method called "on-machine development". That is, on-machine development is a method in which a lithographic printing plate original plate is exposed and then mounted on a printing machine as it is without conventional development, and unnecessary parts of the image recording layer are removed at the initial stage of a normal printing process. Is.
In the present disclosure, a lithographic printing plate original plate that can be used for such on-machine development is referred to as a "machine-developing lithographic printing plate original plate".

Examples of the conventional planographic printing plate original plate include those described in Japanese Patent Application Laid-Open No. 2012-06657577.
Japanese Patent Application Laid-Open No. 2012-066575 contains a support, an image recording layer containing a radical polymerization initiator, a radically polymerizable compound, and a binder polymer having an alkylene oxide group, and an overcoat layer containing celluloses. , The machine-developed flat plate printing plate original plate having in this order is described.

An object to be solved by one embodiment of the present disclosure is to provide an on-board development type lithographic printing plate original plate in which discoloration due to ozone exposure is suppressed.
An object to be solved by another embodiment of the present disclosure is to provide a method for producing a lithographic printing plate using the above-mentioned machine-developing lithographic printing plate original plate, or a method for lithographic printing.

The means for solving the above problems include the following aspects.
<1> The support, the image recording layer, and the outermost layer are provided in this order.
The image recording layer contains a polymerization initiator, a polymerizable compound, and an infrared absorber.
The decomposition rate of the infrared absorber after storage for 8 hours in an environment with an ozone concentration of 150 ppb is 50% or less.
On-machine development type lithographic printing plate original plate.
<2> The machine-developed lithographic printing plate original plate according to <1>, wherein the outermost layer has a film thickness of 0.005 μm to 2 μm.
<3> The machine-developed lithographic printing plate original plate according to <1> or <2>, wherein the outermost layer has oxygen permeability.
<4> The machine-developed lithographic printing plate original plate according to any one of <1> to <3>, wherein the outermost layer contains a polysaccharide.
<5> The machine-developed lithographic printing plate original plate according to any one of <1> to <4>, wherein the outermost layer contains a cellulose derivative having a degree of methoxy group substitution of 1 to 2.
<6> The machine-developed lithographic printing plate original plate according to any one of <1> to <5>, wherein the outermost layer further contains a hydrophobic polymer.
<7> The machine-developed lithographic printing plate original plate according to any one of <1> to <6>, wherein the outermost layer further contains polymer particles.
<8> On-machine development type lithographic printing plate original plate in any one of <1> to <7> in which the outermost layer contains a decomposition type infrared absorber.

<9> The machine-developed lithographic printing plate original plate according to any one of <1> to <8>, wherein the polymerization initiator contains an electron donating type polymerization initiator and an electron accepting type polymerization initiator.
<10> The machine-developed lithographic printing plate original plate according to <9>, wherein the value of HOMO of the infrared absorber-HOMO of the electron donating type polymerization initiator is 0.70 eV or less.
<11> The machine-developed lithographic printing plate original plate according to <9> or <10>, wherein the LUMO value of the electron-accepting polymerization initiator-LUMO of the infrared absorber is 0.80 eV or less.
<12> The machine-developed lithographic printing plate original plate according to any one of <1> to <11>, wherein the polymerizable compound contains a polymerizable compound having 7 or more functionalities.
<13> The machine-developed lithographic printing plate original plate according to any one of <1> to <12>, wherein the polymerizable compound contains a polymerizable compound having 10 or more functionalities.
<14> An on-machine development type lithographic printing plate original plate is added to any one of <1> to <13> in which the image recording layer further contains polymer particles.
<15> The polymer particles are addition polymerization type polymer particles having a hydrophilic group.
The machine-developed lithographic printing plate original plate according to <14>, wherein the hydrophilic group contains a group represented by the following formula Z.
Formula Z: * -Q-W-Y
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, and Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophilic structure. A monovalent group having a hydrophobic structure is represented, either W or Y has a hydrophilic structure, and * represents a binding site with another structure.

<16> The machine-developed lithographic printing plate original plate according to any one of <1> to <15>, wherein the image recording layer further contains a color former.
<17> The on-machine development according to any one of <1> to <16>, wherein the color former is a compound represented by any of the following formulas (Le-1) to (Le-3). Planographic printing plate original plate.

In the formulas (Le-1) to (Le-3), ERG independently represents an electron donating group, and X ₁ to X ₄ independently represent a hydrogen atom, a halogen atom, or a dialkylanilino. _{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 Y _{1 represents a group.} When N, X ₁ does not exist, when Y ₂ is N, X ₄ does not exist, Ra ₁ represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb ₁ to Rb ₄ Independently represent a hydrogen atom, an alkyl group, or an aryl group.

<18> The machine-developed lithographic printing plate original plate according to <16> or <17>, wherein the color former is a compound represented by the following formula (Le-8).

In formula (Le-8), X ₁ to X ₄ independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, and Y ₁ and Y ₂ independently represent C or N, respectively. If Y ₁ is N, then X ₁ is absent, if Y ₂ is N, then X ₄ is absent, and Rb ₁ and Rb ₂ are independently alkyl, aryl, or, respectively. Representing a heteroaryl group, Rc ₁ and Rc ₂ independently represent an aryl group or a heteroaryl group, respectively.

<19> The _{machine according to <18>, wherein Rc 1} and Rc ₂ are phenyl groups each independently having a substituent at at least one ortho position and an electron donating group at the para position. Top-developed lithographic printing plate original plate.

<20> The machine-developed lithographic printing plate original plate according to <16> or <17>, wherein the color former contains a compound represented by the following formula (Le-10).

In formula (Le-10), Ar ₁ independently represents an aryl group or a heteroaryl group, and Ar ₂ independently represents an aryl group having a substituent at at least one ortho position, or at least 1 Represents a heteroaryl group having a substituent at one ortho position.

<21> The above Ar ₁ is an aryl group having an electron donating group or a heteroaryl group having an electron donating group _{, respectively, and the above Ar 2} is independently at least one ortho position. The machine-developed flat plate printing plate original plate according to <20>, which is a phenyl group having a substituent and an electron donating group at the para position.

<22> The support has an aluminum plate and an aluminum anodized film arranged on the aluminum plate.
The anodic oxide film is located closer to the image recording layer than the aluminum plate.
The anodic oxide film has micropores extending in the depth direction from the surface on the image recording layer side.
The average diameter of the micropores on the surface of the anodic oxide film is more than 10 nm and 100 nm or less.
The description in any one of <1> to <21>, wherein the value ^{of L *} a ^* b ^* ^{brightness L *} in the surface color system of the surface of the anodized film on the image recording layer side is 70 to 100. On-machine development type lithographic printing plate original plate.
<23> The micropore communicates with the large-diameter hole extending from the surface of the anodic oxide film to a depth of 10 nm to 1,000 nm and the bottom of the large-diameter hole, and has a depth of 20 nm to 2 from the communication position. It consists of a small-diameter hole that extends to a position of 000 nm.
The average diameter of the large-diameter hole portion on the surface of the anodic oxide film is 15 nm to 100 nm.
The machine-developed lithographic printing plate original plate according to <22>, wherein the average diameter of the small-diameter hole portion at the communication position is 13 nm or less.

<24> The step of exposing the machine-developed lithographic printing plate original plate according to any one of <1> to <23> like an image, and
A method for producing a lithographic printing plate, comprising a step of supplying at least one selected from the group consisting of printing ink and dampening water on a printing machine to remove an image recording layer in a non-image area.
<25> The step of exposing the machine-developed lithographic printing plate original plate according to any one of <1> to <23> like an image, and
A process 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 a printing machine to produce a lithographic printing plate, and printing with the obtained lithographic printing plate. And lithographic printing methods, including.

According to one embodiment of the present disclosure, it is possible to provide an on-board development type lithographic printing plate original plate in which discoloration due to ozone exposure is suppressed.
Further, according to another embodiment of the present disclosure, it is possible to provide a method for producing a lithographic printing plate using the above-mentioned machine-developing lithographic printing plate original plate, or a lithographic printing method.

It is a schematic sectional view of one Embodiment of a support. FIG. 3 is a schematic cross-sectional view of another embodiment of the support.

The contents of the present disclosure will be described in detail below. The description of the constituents described below may be based on the representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.
In the present disclosure, "-" indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
Further, in the notation of a group (atomic group) in the present disclosure, the notation that does not describe substitution or non-substitution includes those having no substituent as well as those having a substituent. For example, the "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In the present disclosure, "(meth) acrylic" is a term used in 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 methacrylic. be.
In addition, the term "process" in the present disclosure is included in this term as long as the intended purpose of the process is achieved, not only in an independent process but also in the case where it cannot be clearly distinguished from other processes. Is done.
Further, in the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.
Further, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.
Further, for the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the present disclosure, unless otherwise specified, columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Toso Co., Ltd.) are used. The molecular weight is detected by the solvent THF (tetrahydrofuran) and the differential refractometer by the gel permeation chromatography (GPC) analyzer and converted using polystyrene as the standard substance.
In the present disclosure, the term "lithographic printing plate original plate" includes not only a lithographic printing plate original plate but also a discarded plate original plate. Further, the term "lithographic printing plate" includes not only a lithographic printing plate produced by subjecting a lithographic printing plate original plate through operations such as exposure and development, but also a discarded plate, if necessary. In the case of a discarded original plate, exposure and development operations are not always necessary. The discarded plate is a lithographic printing plate original plate for attaching to an unused plate cylinder, for example, when printing a part of the paper surface in a single color or two colors in color newspaper printing.
In the present disclosure, "excellent in printing resistance" means that the number of printable sheets of a lithographic printing plate is large, and the printing resistance when UV ink is used as the ink for printing is hereinafter referred to as "UV". Also called "print resistance".

≪In-machine development type lithographic printing plate original plate≫
The on-machine development type lithographic printing plate original plate (hereinafter, also simply referred to as “lithographic printing plate original plate”) according to the present disclosure has a support, an image recording layer, and an outermost layer in this order, and the image recording layer starts polymerization. The decomposition rate of the infrared absorber is 50% or less after storage for 8 hours in an environment with an ozone concentration of 150 ppb, which contains an agent, a polymerizable compound, and an infrared absorber.

In a lithographic printing plate original plate having an image recording layer containing a polymerization initiator, a polymerizable compound, and an infrared absorber as described in JP-A-2012-0665757, infrared rays in the image recording layer are generated by ozone in the atmosphere. There is a problem that the absorber is decomposed and the lithographic printing plate original plate is discolored.
On the other hand, in the lithographic printing plate original plate according to the present disclosure, the decomposition rate of the infrared absorber in the image recording layer after storage for 8 hours in an environment with an ozone concentration of 150 ppb is 50% or less. That is, even when stored for 8 hours in an environment with a high ozone concentration of 150 ppb in the atmosphere, in the lithographic printing plate original plate according to the present disclosure, 50% or more of the infrared absorber in the image recording layer is not decomposed. Means to remain in.
By having such characteristics, the lithographic printing plate original plate according to the present disclosure is suppressed from discoloration due to ozone exposure.
The smaller the decomposition rate of the infrared absorber, the more the discoloration due to ozone exposure is suppressed.

<Decomposition rate of infrared absorber in lithographic printing plate original plate by ozone exposure>
The lithographic printing plate original plate according to the present disclosure has a decomposition rate of the infrared absorber in the image recording layer of 50% or less after being stored for 8 hours in an environment with an ozone concentration of 150 ppb.
That is, in the lithographic printing plate original plate according to the present disclosure, the amount of the infrared absorber in the decomposed image recording layer after storage for 8 hours in an environment of ozone concentration of 150 ppb is larger than the amount of the infrared absorber before storage. It means that it is 50% or less.
In other words, in the lithographic printing plate original plate according to the present disclosure, the amount of the infrared absorber remaining in the image recording layer after storage in an environment of ozone concentration of 150 ppb for 8 hours is the amount of the infrared absorber in the image recording layer before storage. It means that it is 50% or more with respect to the amount of.
The amount of the infrared absorber is determined by analyzing the extract extracted from the platen original plate with a solvent by high performance liquid chromatography (HPLC) and quantifying the infrared absorber.

The smaller the decomposition rate of the infrared absorber, the smaller the lithographic printing plate original plate, the more the discoloration due to ozone exposure is suppressed.
The decomposition rate of the infrared absorber is preferably 45% or less, more preferably 40% or less, further preferably 35% or less, and particularly preferably 30% or less.
The lower limit of the decomposition rate of the infrared absorber may be 0%, but may be, for example, 1% or more, or 5% or more.

The decomposition rate of the infrared absorber is measured by the following method.
A lithographic printing plate original plate is cut out to a size of 3 cm square when viewed from the outermost layer side, and two samples having the same shape are obtained.
One of the two samples is extracted with 5 mL of acetonitrile in an ultrasonic bath for 30 minutes and the resulting extract is subjected to HPLC analysis through a 0.20 mm filter. The peak area of the infrared absorber is determined by HPLC analysis, and this is defined as the amount (X) of the infrared absorber before ozone exposure.

Place the remaining one of the two samples in a 100 mL vial bottle and place on a table.
Insert the foot tube of the Kiriyama Rohto bottle (manufactured by Kiriyama Glass Co., Ltd.) into the bayal bottle containing the sample and fix it. On the other hand, a stirring blade is placed as a spacer in the upper opening of the Kiriyama funnel bottle (manufactured by Kiriyama Glass Co., Ltd.). Then, an ozone generator (a refreshing ion plus CS-4 commercial ozone generator manufactured by Associa Ozone Co., Ltd.) is fixed above the stirring blade (here, the stirring blade and the ozone generator are separated by about 150 mm). ing). In this device, the ozone generated from the ozone generator becomes an air flow containing ozone by moving the stirring blade, and reaches the sample in the vial bottle through the Kiriyama funnel bottle.
Ozone exposure to the sample is performed using such a device. During ozone exposure to the sample, the ozone concentration in the vial bottle is measured and adjusted so that the ozone concentration is 150 ppm. Further, this ozone exposure is performed at 25 ° C. and 50% RH.
The above-mentioned ozone exposure to the sample was continued for 8 hours, and the sample after the ozone exposure was continued for 8 hours was subjected to HPLC analysis by the same method as above to determine the peak area of the infrared absorber, which was determined after ozone exposure. The amount of the infrared absorber (Y).

The amount (X) of the infrared absorber before ozone exposure and the amount (Y) of the infrared absorber after ozone exposure obtained as described above are substituted into the following formula 1 to decompose the infrared absorber. Find the rate (Z).
Equation 1: (Z) = 100-[(Y) / (X) × 100]

The conditions for performing HPLC analysis are as follows.
・ Equipment: Alliance 2695, Waters Corp. ・ Column: Mightysil RP-18GP 250 mm x φ4.6 mm (5 μm), Kanto Chemical Co., Inc.
-Column temperature: 40 ° C
-Eluent: <A> MeOH (containing 0.1% by mass acetic acid + 0.1% by mass triethylamine), <B> H ₂ O (containing 0.1% by mass acetic acid + 0.1% by mass triethylamine)
-Gragent: <A / B> = 30/70 (0 min) -100/0 (28 min) -100/0 (40 min) -30/70 (40.1 min) Equilibration-Flow velocity: 1.0 mL / min
・ Injection amount: 10 mL
-UV detector: PDA 2998, Waters

Next, the details of each constituent requirement in the lithographic printing plate original plate according to this disclosure will be described.

<Outermost layer>
The lithographic printing plate original plate according to the present disclosure has an outermost layer on the side opposite to the support side of the image recording layer.
The outermost layer in the present disclosure is preferably an ozone blocking layer from the viewpoint of achieving the decomposition rate of the infrared absorber due to ozone exposure described above.
The ozone blocking layer is not particularly limited as long as it has an ozone blocking ability that achieves the decomposition rate of the infrared absorber due to the ozone exposure described above.

[Water-soluble polymer]
The outermost layer in the present disclosure preferably contains a water-soluble polymer from the viewpoint of developability (more preferably, on-machine developability).
In the present disclosure, the water-soluble polymer is a solution in which 5 g of the polymer is dissolved in 125 ° C. and 100 g of pure water at 5 g or more, and 5 g of the polymer is dissolved in 125 ° C. and 100 g of pure water, and the solution is cooled to 25 ° C. A polymer that does not precipitate even if it does.

Examples of the water-soluble polymer used for the outermost layer include polyvinyl alcohol, modified polyvinyl alcohol, poly (meth) acrylamide, polyethylene glycol, poly (meth) acrylonitrile, polyvinylpyrrolidone, and a copolymer in which the raw material monomers of these polymers are combined. , Copolymers obtained by combining the raw material monomers of these polymers with other monomers and the like.
The other monomer is not particularly limited as long as it is a monomer copolymerizable with the above-mentioned raw material monomer, but for example, an alkyl (meth) acrylate such as vinyl acetate, methyl (meth) acrylate, and butyl (meth) acrylate. Examples thereof include ester, carboxy group, sulfo group, and addition-polymerized monomer having an acid group such as a salt thereof.
Further, as the modified polyvinyl alcohol, an acid-modified polyvinyl alcohol having a carboxy group or a sulfo group is preferably used. Specific examples of the modified polyvinyl alcohol include the modified polyvinyl alcohol described in JP-A-2005-250216 and JP-A-2006-259137.

Further, as the water-soluble polymer, polysaccharides can also be used.
That is, the outermost layer in the present disclosure preferably contains a polysaccharide.
The polysaccharide used for the outermost layer is not limited as long as it has the above-mentioned water solubility, and a cellulose derivative is preferable from the viewpoint of forming an outermost layer having high ozone blocking ability and oxygen permeability. Be done.
In addition, examples of the polysaccharide used in the outermost layer include soybean polysaccharide, modified starch, gum arabic, dextrin, pullulan and the like.

In the cellulose derivative, in at least a part of the hydroxy groups of cellulose, the hydrogen atom of the hydroxy group is substituted with at least one group selected from the group consisting of an alkyl group, a hydroxyalkyl group, and a carboxyalkyl group. Examples include compounds. Here, examples of the alkyl group, the alkyl group in the hydroxyalkyl group, and the alkyl group in the carboxyalkyl group include a methyl group, an ethyl group, a propyl group and the like.
Among the above, as the cellulose derivative, a compound in which the hydrogen atom of the hydroxy group is substituted with at least an alkyl group (preferably a methyl group) in at least a part of the hydroxy groups of cellulose is more preferable. That is, as the cellulose derivative, a compound in which at least a part of the hydroxy group of cellulose is replaced with an alkoxy group (preferably a methoxy group) is preferable.

Specific examples of the cellulose derivative include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose and the like, and among them, methyl cellulose and hydroxypropyl methyl cellulose are preferable.

The degree of substitution (preferably the degree of methoxy substitution) of the hydroxy group with the above group in the cellulose derivative is preferably 0.1 to 6.0, more preferably 1 to 4, and 1 to 2. Is more preferable.
That is, it is particularly preferable that the outermost layer contains a cellulose derivative having a degree of methoxy substitution of 1 to 2.
Here, the degree of methoxy substitution means the average number of hydroxyl groups substituted with methoxy groups per glucose ring unit of cellulose. This degree of methoxy substitution is determined by J. G. Gobler, E.I. P. Samscl, and G. H. It can be measured by the method by Zeisel-GC described in Beaver, Talanta, 9,474 (1962).

The water-soluble polymer may be used alone or in combination of two or more.

The content of the water-soluble polymer contained in the outermost layer is preferably 20% by mass to 99% by mass, more preferably 30% by mass to 98% by mass, more preferably 40% by mass, based on the total mass of the outermost layer. It is more preferably mass% to 97% by mass.
The content of the polysaccharide (preferably a cellulose derivative) contained in the outermost layer is 30% by mass to 98% by mass with respect to the total mass of the outermost layer from the viewpoint of suppressing discoloration of the flat plate printing plate original plate due to ozone exposure. %, More preferably 35% by mass to 98% by mass, and even more preferably 40% by mass to 97% by mass.

[Hydrophobic polymer]
The outermost layer may contain a hydrophobic polymer.
The hydrophobic polymer means a polymer that dissolves or does not dissolve in less than 5 g in 100 g of pure water at 125 ° C.
Examples of the hydrophobic polymer include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, and poly (meth) acrylic acid alkyl esters (for example, poly (meth) methyl acrylate, poly (meth) ethyl acrylate, and poly (meth). ) Butylate acrylate, etc.), a copolymer in which the raw material monomers of these polymers are combined (for example, styrene acrylic resin, etc.) and the like.

The hydrophobic polymer may be used alone or in combination of two or more.

When the outermost layer contains a hydrophobic polymer, the content of the hydrophobic polymer is preferably 5% by mass to 70% by mass, preferably 7.5% by mass to 50% by mass, based on the total mass of the outermost layer. It is preferably present, and more preferably 10% by mass to 30% by mass.

[Polymer particles]
The outermost layer may contain polymer particles.
The polymer particles mean a polymer that exhibits a particle shape in the outermost layer.
Even if the polymer contained in the polymer particles corresponds to the above-mentioned water-soluble polymer or hydrophobic polymer, if the polymer remains in the particle shape in the outermost layer, it is included in the "polymer particles".
Above all, the outermost layer preferably contains hydrophobic polymer particles.
The presence or absence of polymer particles in the outermost layer can be confirmed by observing the outermost layer surface with a scanning electron microscope (SEM).

The polymer particles are preferably in the form of, for example, microcapsules, microgels (that is, crosslinked polymer particles), and more preferably in the form of microgels.
Further, the polymer particles preferably have at least a hydrophilic group on the surface.
That is, as the polymer particles contained in the outermost layer, microgels having a hydrophilic group on the surface are preferable. Examples of such microgels include microgels used for image recording layers, which will be described later.

The polymer particles may be used alone or in combination of two or more.

When the outermost layer contains polymer particles, the content of the polymer particles is preferably 10% by mass to 80% by mass, preferably 15% by mass to 60% by mass, based on the total mass of the outermost layer. , 20% by mass to 40% by mass, more preferably.

[Decomposable infrared absorber]
The outermost layer may contain a decomposable infrared absorber from the viewpoint of enhancing the visibility of the exposed portion.
The decomposable infrared absorber may be any as long as it absorbs and decomposes at least a part of the light in the infrared wavelength range (that is, the wavelength range of 750 nm to 1 mm, preferably the wavelength range of 750 nm to 1,400 nm). It is preferably a compound having maximum absorption in the wavelength range of 750 nm to 1,400 nm.
More specifically, the decomposition type infrared absorber is preferably a compound that decomposes due to infrared exposure to produce a compound having a maximum absorption wavelength in the wavelength range of 500 nm to 600 nm.

The decomposable infrared absorber is a cyanine dye having a ^{group (specifically, R 1} in the following formulas 1-1 to 1-7) that decomposes by infrared exposure from the viewpoint of enhancing the visibility of the exposed portion. Is preferable.
The decomposition type infrared absorber is more preferably a compound represented by the following formula 1-1 from the viewpoint of enhancing the visibility of the exposed portion.

In formula 1-1, R ¹ represents a group represented by any of the following formulas 2 to 4, and R ¹¹ to R ¹⁸ independently represent a hydrogen atom, a halogen atom, -R ^a , and -OR ^b. , -SR ^c , or -NR ^d R ^e , R ^a to R ^e each independently represent a hydrocarbon group, and A ₁ , A ₂ , and a plurality of R ¹¹ to R ¹⁸ are connected and simply. Rings or polycycles may be formed, where A ₁ and A ₂ independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, and n ₁₁ and n ₁₂ are independent integers of 0 to 5, respectively. However, _{the sum of n 11} and n ₁₂ is 2 or more, n ₁₃ and n ₁₄ independently represent 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR ^10- . ^{Representing R 10} , represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counterion that neutralizes the charge.

In formulas 2 to 4, R ²⁰ , R ³⁰ , R ⁴¹ , and R ⁴² independently represent an alkyl group or an aryl group, Zb represents a counterion that neutralizes the charge, and the wavy line represents the above formula. Represents a binding site with a group represented by L in 1-1.

Compounds of the formula 1-1, when exposed with ^{infrared, R} 1 -L bond is cleaved, L is, = O, = S, or = become ^{NR 10,} changes color.

In formula 1-1, R ¹ represents a group represented by any of the above formulas 2 to 4.
Hereinafter, the group represented by the formula 2, the group represented by the formula 3, and the group represented by the formula 4 will be described.

In formula 2, R ²⁰ represents an alkyl group or an aryl group, and the wavy line portion represents a binding site with a group represented by L in formula 1-1.
As the ^{alkyl group represented by R 20} , an alkyl group having 1 to 30 carbon atoms is preferable, an alkyl group having 1 to 15 carbon atoms is more preferable, and an alkyl group having 1 to 10 carbon atoms is further preferable.
The alkyl group may be linear, have a branch, or have a ring structure.
As the ^{aryl group represented by R 20} , an aryl group having 6 to 30 carbon atoms is preferable, an aryl group having 6 to 20 carbon atoms is more preferable, and an aryl group having 6 to 12 carbon atoms is further preferable.
The R ²⁰ is preferably an alkyl group from the viewpoint of enhancing the visibility of the exposed portion.

Further, in view of enhancing the visibility of the exposed portion, the alkyl group represented by R ^20, it is preferably a secondary alkyl group or a tertiary alkyl group, preferably a tertiary alkyl group ..
Furthermore, in view of enhancing the visibility of the exposed portion, the alkyl group represented by R ^20, it is preferably a branched alkyl group having 3 to 10 carbon atoms is an alkyl group having 1 to 8 carbon atoms More preferably, it is more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.
Here, the ^{alkyl group represented by R 20} may be a substituted alkyl group substituted with a halogen atom (for example, a chloro group) or the like.

Specific examples of the group represented by the above formula 2 are given below, but the present disclosure is not limited thereto. In the following structural formula, ● represents the binding site with the group represented by L in the formula 1-1.

In formula 3, R ³⁰ represents an alkyl group or an aryl group, and the wavy line portion represents a binding site with a group represented by L in formula 1-1.
The ^{alkyl group and aryl group represented by R 30} are the same as those of the alkyl group and aryl group ^{represented by R 20} in Formula 2, and the preferred embodiments are also the same.

From the viewpoint of enhancing the visibility of the exposed portion, the alkyl group represented by R ^30, preferably a is secondary alkyl group or a tertiary alkyl group is preferably a tertiary alkyl group.
Further, from the viewpoint of improving the visibility of the exposed portion, the ^{alkyl group represented by R 30} is preferably an alkyl group having 1 to 8 carbon atoms, and is a branched alkyl group having 3 to 10 carbon atoms. More preferably, it is more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.
Furthermore, in view of enhancing the visibility of the exposed portion is preferably an alkyl group represented by R ³⁰ is a substituted alkyl group is preferably a substituted alkyl group, more preferably a fluoro-substituted alkyl group, It is more preferably a perfluoroalkyl group, and particularly preferably a trifluoromethyl group.

From the viewpoint of improving the visibility of the exposed portion, the ^{aryl group represented by R 30} is preferably a substituted aryl group, and the substituent is an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms) or an alkoxy group. (Preferably an alkoxy group having 1 to 4 carbon atoms) and the like.

Specific examples of the group represented by the above formula 3 are given below, but the present disclosure is not limited thereto. In the following structural formula, ● represents the binding site with the group represented by L in the formula 1-1.

In Formula 4, R ⁴¹ and R ⁴² each independently represent an alkyl or aryl group, Zb represents a charge-neutralizing counterion, and the wavy portion is represented by L in Formula 1-1. Represents a binding site with a group.
The ^{alkyl group and aryl group represented by R 41} or R ⁴² are the same as those of the alkyl group and aryl group ^{represented by R 20} in the formula 2, and the preferred embodiments are also the same.
The R ⁴¹ is preferably an alkyl group from the viewpoint of enhancing the visibility of the exposed portion.
The R ⁴² is preferably an alkyl group from the viewpoint of enhancing the visibility of the exposed portion.

From the viewpoint of improving the visibility of the exposed portion, the ^{alkyl group represented by R 41} is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. Methyl groups are particularly preferred.
From the viewpoint of enhancing the visibility of the exposed portion, the ^{alkyl group represented by R 42} is preferably a secondary alkyl group or a tertiary alkyl group, and preferably a tertiary alkyl group.
Further, from the viewpoint of improving the visibility of the exposed portion, the ^{alkyl group represented by R 42} is preferably an alkyl group having 1 to 8 carbon atoms, and is a branched alkyl group having 3 to 10 carbon atoms. More preferably, it is more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

Zb in the formula 4 may be a counterion for neutralizing the charge, and the compound as a whole may be contained in Za in the formula 1-1.
Zb is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a tetrafluoroborate ion.

Specific examples of the group represented by the above formula 4 are given below, but the present disclosure is not limited thereto. In the following structural formula, ● represents the binding site with the group represented by L in the formula 1-1.

In the formula 1-1, L is ^{preferably an oxygen atom or −NR 10} −, and an oxygen atom is particularly preferable.
Further, R ¹⁰ ^{in −NR 10} − is preferably an alkyl group. As the ^{alkyl group represented by R 10} , an alkyl group having 1 to 10 carbon atoms is preferable. Further, the ^{alkyl group represented by R 10} may be linear, may have a branch, or may have a ring structure.
Among the alkyl groups represented by R ¹⁰ , a methyl group, a tert-butyl group, or a cyclohexyl group is preferable.
When R ¹⁰ ^{in −NR 10} − is an aryl group, an aryl group having 6 to 30 carbon atoms is preferable, an aryl group having 6 to 20 carbon atoms is more preferable, and an aryl group having 6 to 12 carbon atoms is further preferable. Moreover, these aryl groups may have a substituent.

In Formula ^1-1, ^R 11 ^~ R ¹⁸ are each independently a hydrogen ^atom, -R ^a, is preferably -OR b, -SR ^c, or ^-NR d ^{R e.}
Hydrocarbon groups represented by R a ^~ R ^e is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably a hydrocarbon group having 1 to 15 carbon atoms, further a hydrocarbon group having 1 to 10 carbon atoms preferable. Further, the ^{hydrocarbon group represented by Ra} to ^Re may be linear, have a branch, or have a ring structure.
Examples of the hydrocarbon group represented by R a ^~ R ^e, the alkyl group is particularly preferred.

As the alkyl group, an alkyl group having 1 to 30 carbon atoms is preferable, an alkyl group having 1 to 15 carbon atoms is more preferable, and an alkyl group having 1 to 10 carbon atoms is further preferable.
The alkyl group may be linear, have a branch, or have a ring structure.
Specifically, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, and an octadecyl group. Group, eicosyl group, isopropyl group, isobutyl group, s-butyl group, tert-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl Groups include groups and 2-norbornyl groups.
Among these alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is preferable.

The alkyl group may have a substituent.
Examples of substituents include an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and these. Examples include a group that combines the above.

^{Each of R 11} to R ¹⁴ in the formula 1-1 ^{is preferably a hydrogen atom or —R a} (that is, a hydrocarbon group) independently, and more preferably a hydrogen atom or an alkyl group, as follows. Except for cases, it is more preferably a hydrogen atom.
^{Among them, R 11} and R ¹³ bonded to the carbon atom to which L is bonded are preferably an alkyl group, and it is more preferable that both are linked to form a ring. The ring formed may be a monocyclic ring or a polycyclic ring. Specific examples of the ring formed include a monocycle such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring and a cyclohexadiene ring, and a polycycle such as an indene ring and an indole ring.
Further, ^{it is preferable that R 12} bonded to the carbon atom to which _{A 1} ⁺ is bonded is linked to R ¹⁵ or R ¹⁶ (preferably R ¹⁶ ) to form a ring, and R to be bonded to the carbon atom to which _{A 2 is bonded.} ¹⁴ is ^{preferably linked to R 17} or R ¹⁸ (preferably R ¹⁸ ) to form a ring.

In formula 1-1, n ₁₃ is preferably 1 and R ¹⁶ is ^{preferably —R a} (ie, a hydrocarbon group).
Further, ^{it is preferable that R 16} is ^{linked to R 12} bonded to the carbon atom to which _{A 1} ⁺ is bonded to form a ring. As the ring to be formed, an indolium ring, a pyrylium ring, a thiopyrylium ring, a benzoxazoline ring, or a benzoimidazoline ring is preferable, and an indolium ring is more preferable from the viewpoint of enhancing the visibility of the exposed portion. These rings may further have a substituent.
In formula 1-1, n ₁₄ is preferably 1 and R ¹⁸ is ^{preferably —R a} (ie, a hydrocarbon group).
Further, ^{it is preferable that R 18} is ^{linked to R 14} bonded to the carbon atom to which _{A 2} is bonded to form a ring. As the ring to be formed, an indole ring, a pyran ring, a thiopyran ring, a benzoxazole ring, or a benzimidazole ring is preferable, and an indole ring is more preferable from the viewpoint of enhancing the visibility of the exposed portion. These rings may further have a substituent.
^{It is preferable that R 16} and R ¹⁸ in the formula 1-1 have the same group, and when each forms a ring, it is preferable to form a ring having the same structure except for _{A 1} ⁺ and A _2.

^{It is preferable that R 15} and R ¹⁷ in the formula 1-1 are the same group. Further, R ¹⁵ and R ¹⁷ are preferably —R ^a (that is, a hydrocarbon group), more preferably an alkyl group, and even more preferably a substituted alkyl group.

In the compound represented by the formula 1-1, R ¹⁵ and R ¹⁷ are preferably substituent alkyl groups from the viewpoint of improving water solubility.
Examples of the substituted alkyl group represented by R ¹⁵ or R ¹⁷ include a group represented by any of the following formulas (a1) to (a4).

Wherein (a1) ~ formula ^{(a4), R W0} represents an alkylene group having 2 to 6 carbon atoms, W is a single bond or an oxygen _{atom, n W1} represents an integer of 1 ~ ^{45, R W1} carbon Alkyl groups of numbers 1 to 12 or -C (= O) ^-RW5 are represented, ^RW5 represents alkyl groups of carbon atoms 1 to 12, and ^RW2 to ^RW4 are independently single bonds or carbon atoms, respectively. It represents 1 to 12 alkylene groups, and M represents a hydrogen atom, a sodium atom, a potassium atom, or an onium group.

^{Specific examples of the alkylene group represented by RW0} in the formula (a1) include an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group and n-. Examples thereof include a hexyl group and an isohexyl group, and an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferable, and an n-propylene group is particularly preferable.
n _W1 is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3.
^{Specific examples of the alkyl group represented by RW1} include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group and neopentyl. Examples thereof include a group, an n-hexyl group, an n-octyl group, an n-dodecyl group, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, or an n-butyl group and a tert-butyl group are preferable. , Or an ethyl group is more preferable, and a methyl group is particularly preferable.
Alkyl group represented by R ^W5 is the same as defined for the alkyl group represented by R ^W1, preferred embodiments are also the same as the preferred embodiment of the alkyl group represented by R ^W1.

Specific examples of the group represented by the formula (a1) are shown below, but the present disclosure is not limited thereto. In the following structural formula, Me represents a methyl group, Et represents an ethyl group, and * represents a binding site.

^{Specific examples of the alkylene group represented by RW2} to ^RW4 in the formulas (a2) to (a4) include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group and an isobutylene group. , N-pentylene group, isopentylene group, n-hexyl group, isohexyl group, n-octylene group, n-dodecylene group and the like, preferably an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group. , Ethylene group, or n-propylene group is particularly preferable.
In the formula (a3), the two existing Ms may be the same or different.

In the formulas (a2) to (a4), examples of the onium group represented by M include an ammonium group, an iodonium group, a phosphonium group, a sulfonium group, and the like.
The CO ₂ M in the formula (a 2), the PO ₃ M ₂ _{in the formula (a 2), and the SO 3} M in the formula (a 4) may all have an anion structure in which M is dissociated. Counter cation of the anion structure may be a A ₁ ^+, may be a cation may be included in R ¹ -L in Formula 1-1.

Among the groups represented by the formulas (a1) to (a4), the group represented by the formula (a1), the formula (a2), or the formula (a4) is preferable.

_{It is preferable that n 11} and n ₁₂ in the formula 1-1 are the same, and an integer of 1 to 5 is preferable, an integer of 1 to 3 is more preferable, 1 or 2 is more preferable, and 2 is particularly preferable.

_{A 1} and A ₂ in the formula 1-1 independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, and a nitrogen atom is preferable.
_{It is preferable that A 1} and A ₂ in the formula 1-1 are the same atom.

Za in Equation 1-1 represents a counterion that neutralizes the charge.
If all of R ¹¹ to R ¹⁸ and R ^1- L are charge-neutral groups, Za is a monovalent counter anion. However, R ¹¹ to R ¹⁸ and R ^{1 to} L may have an anionic structure or a cationic structure. For example, when R ¹¹ to R ¹⁸ and R ^{1 to} L have two or more anionic structures, Za Can also be a counter cation.
If the cyanine dye represented by the formula 1-1 has a charge-neutral structure in the whole compound except Za, Za is not necessary.
When Za is a counter anion, sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, p-toluenesulfonate ion, perchlorate ion and the like can be mentioned, and tetrafluoroborate ion is preferable.
When Za is a counter cation, alkali metal ion, alkaline earth metal ion, ammonium ion, pyridinium ion, sulfonium ion and the like can be mentioned, and sodium ion, potassium ion, ammonium ion, pyridinium ion or sulfonium ion are preferable. Ions, potassium ions, or ammonium ions are more preferred.

The decomposition type infrared absorber is more preferably a compound represented by the following formula 1-2 (that is, a cyanine dye) from the viewpoint of enhancing the visibility of the exposed portion.

In formula 1-2, R ¹ represents a group represented by any of the above formulas 2 to 4, and R ¹⁹ to R ²² independently represent a hydrogen atom, a halogen atom, -R ^a , and -OR ^b. , -CN, represents -SR ^c, or ^{^{^{^{-NR d R e, R 23 ~}}}} R 24 each independently represent a hydrogen atom, or a -R ^{^a,} ^R ^a ~ R ^e are each independently carbon Representing a hydrogen group, R ¹⁹ and R ²⁰ , R ²¹ and R ²² , or R ²³ and R ²⁴ may be linked to form a monocyclic or polycyclic, where L is an oxygen atom, a sulfur atom, or -NR ^10- , R ¹⁰ represents a hydrogen atom, an alkyl group, or an aryl group, and R ^d1 to R ^d4 and W ¹ to W ² each independently may have a substituent. Represents, and Za represents a counter ion that neutralizes the charge.

^{R 1} in Formula 1-2 is synonymous with ^{R 1} in the formula 1-1, preferable embodiments thereof are also the same.

In formula 1-2, R ¹⁹ to R ²² are preferably hydrogen atoms, halogen atoms, -R ^a , -OR ^b , or -CN, respectively.
More ^{specifically, R 19} and ^{R 21} are preferably hydrogen atom, or a -R ^a.
Further, R ²⁰ and R ²² are preferably hydrogen atoms, -R ^a , -OR ^b , or -CN.
As ^{—R a} represented by ^{R 19} to R ²² , an alkyl group or an alkenyl group is preferable.
When all of ^{R 19} to R ²² ^{are −R a,} it is preferable that R ¹⁹ and R ²⁰ and R ²¹ and R ²² are connected to form a monocyclic or polycyclic ring.
Examples of the ring formed by connecting R ¹⁹ and R ²⁰ or R ²¹ and R ²² include a benzene ring, a cyclohexane ring, a cyclopentane ring and the like.

In formula 1-2, ^{it is preferable that R 23} and R ²⁴ are connected to form a monocyclic or polycyclic ring.
The ^{ring formed by connecting R 23} and R ²⁴ may be a monocyclic ring or a polycyclic ring. Specific examples of the ring formed include a monocycle such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring and a cyclohexadiene ring, and a polycycle such as an indene ring and an indole ring.

In formula 1-2, R ^d1 to R ^d4 are preferably unsubstituted alkyl groups. Further, ^{it is preferable that R d1} to R ^d4 are all the same group.
Examples of the unsubstituted alkyl group include a methyl group and an ethyl group, and among them, a methyl group is preferable.

In formula 1-2, W ¹ to W ² are preferably substituted alkyl groups from the viewpoint of increasing water solubility in the compound represented by formula 1-2.
Examples of the ^{substituted alkyl group represented by W 1} to W ² include groups represented by any of the formulas (a1) to (a4) in the formula 1-1, and the preferred embodiment is also the same.

Za represents a counterion that neutralizes the charge in the molecule.
If all of R ¹⁹ to R ²² , R ²³ to R ²⁴ , R ^d1 to R ^d4 , W ¹ to W ² , and R ^{1 to} L are charge-neutral groups, then Za is a monovalent counter anion. Will be. However, R ¹⁹ to R ²² , R ²³ to R ²⁴ , R ^d1 to R ^d4 , W ¹ to W ² , and R ^{1 to} L may have an anionic structure or a cationic structure, for example, R ^19. If ~ R ²² , R ²³ to R ²⁴ , R ^d1 to R ^d4 , W ¹ to W ² , and R ^{1 to} L have two or more anionic structures, Za can also be a counter cation.
If the compound represented by the formula 1-2 has a charge-neutral structure as a whole except for Za, Za is not necessary.
The example when Za is a counter anion is the same as Za in Formula 1-1, and the preferred embodiment is also the same. Further, the example in which Za is a counter cation is the same as Za in Formula 1-1, and the preferred embodiment is also the same.

The cyanine dye as the decomposable infrared absorber is more preferably a compound represented by any of the following formulas 1-3 to 1-7 from the viewpoint of enhancing the visibility of the exposed portion.
In particular, from the viewpoint of enhancing the visibility of the exposed portion, the compound represented by any of the formulas 1-3, 1-5, and 1-6 is preferable.

In formulas 1-3 to 1-7, R ¹ represents a group represented by any of the above formulas 2 to 4, and R ¹⁹ to R ²² are independently hydrogen atom, halogen atom, and −R, respectively. ^a , -OR ^b , -CN, -SR ^c , or -NR ^d R ^e , and R ²⁵ to R ²⁶ ^{independently represent a} hydrogen atom, a halogen atom, or -R a, and R ^a to R. ^e independently represents a hydrocarbon group, and R ¹⁹ and R ²⁰ , R ²¹ and R ²² , or R ²⁵ and R ²⁶ may be linked to form a monocyclic or polycyclic, where L is. , Oxygen atom, sulfur atom, or -NR ^10- , R ¹⁰ represents a hydrogen atom, an alkyl group, or an aryl group, and R ^d1 to R ^d4 and W ¹ to W ² are independent substituents. Represents an alkyl group which may have, and Za represents a counterion that neutralizes the charge.

^{^R} ^1, ^R ¹⁹ ~ ^R 22 in Formula 1-3 to Formula ^{^{1-7, R d1 ~ R d4,}} W 1 ~ W 2, and L ^{^{^{is, R 1, R 19 ~ R}}} 22 in Formula 1-2, R ^{^{^{d1 ~ R d4, W 1 ~}}} W 2, and has the same meaning as L, and also the same preferred embodiment.
^{It is preferable that R 25} to R ²⁶ in the formula 1-7 are independently hydrogen atoms or methyl groups, respectively.

The following are specific examples of the cyanine dye of the decomposition type infrared absorber, but the present disclosure is not limited to these.

Further, as the cyanine dye which is a decomposition type infrared absorber, the infrared absorbent compound described in International Publication No. 2019/219560 can be preferably used.

The decomposition type infrared absorber may be used alone or in combination of two or more.

When the outermost layer contains a decomposition type infrared absorber, the content of the decomposition type infrared absorber is preferably 1% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, based on the total mass of the outermost layer. It is more preferably 10% by mass to 30% by mass.

[Other ingredients]
In addition to the above-mentioned components, the outermost layer in the present disclosure may contain known additives such as an inorganic layered compound and a surfactant.

[Method of forming the outermost layer]
The method for forming the outermost layer is not particularly limited, but it is preferable to use the following method from the viewpoint of enhancing the ozone blocking property.
That is, a coating liquid having a solid content concentration of 5% by mass to 30% by mass is applied onto the image recording layer formed on the support, and the obtained coating film is applied at 70 ° C. to 200 ° C. for 5 seconds to 30 seconds. It is a method of forming the outermost layer by drying under the drying conditions of.
By using this method, it becomes easy to form an outermost layer in which the decomposition rate of the infrared absorber by ozone exposure is 50% or less.

In the formation of the outermost layer, the solid content concentration of the coating liquid is preferably 7.5% by mass to 25% by mass, more preferably 10% by mass to 20% by mass.

Further, in forming the outermost layer, the drying condition of the coating film is preferably 7.5 seconds to 25 seconds at 80 ° C to 170 ° C, and 10 seconds to 20 seconds at 90 ° C to 150 ° C. preferable.

Outermost coating amount (solid content) is preferably from ^{^{0.01g / m 2 ~ 10g / m}} 2, more preferably ^{^{0.02g / m 2 ~ 3g / m}} 2, 0.1g / m 2 ~ 2g / m ² is particularly preferable.
The film thickness of the outermost layer is preferably 0.005 μm to 2 μm, preferably 0.05 μm to 5 μm, and more preferably 0.1 μm to 3 μm.
In the present disclosure, the film thickness of each layer in the lithographic printing plate original plate is determined by preparing a section cut in a direction perpendicular to the surface of the lithographic printing plate original plate, and the cross section of the section is scanned by a scanning electron microscope (SEM). The average film thickness when observed in a range of 50 μm in width in the horizontal direction with respect to the surface of the printing plate.

[Oxygen permeability]
The outermost layer may have oxygen permeability.
Here, "the outermost layer has oxygen permeability" means that the halftone dot area ratio ratio obtained by the method described later is more than 0.9.
When the outermost layer has oxygen permeability, that is, when the halftone dot area ratio is more than 0.9, the halftone dot image is thickened in the scanning direction of the exposure in the printed matter, and the streak-like unevenness (so-called) is observed. It is possible to suppress the occurrence of (also called swath unevenness). This streak-like unevenness is easily affected by the type of plate setter. Therefore, since the outermost layer has oxygen permeability, it can be applied to a plate setter in which streak-like unevenness is likely to occur, so that the selection range of the plate setter can be expanded.

From the viewpoint of suppressing streak-like unevenness, the halftone dot area ratio is preferably 0.92 or more, more preferably 0.94 or more, further preferably 0.96 or more, and particularly preferably 0.98 or more.
The upper limit of the halftone dot area ratio is, for example, 1.00.

Hereinafter, how to obtain the halftone dot area ratio and the halftone dot area ratio ratio will be described.
First, two lithographic printing plate original plates differing only in the presence or absence of the outermost layer (that is, a lithographic printing plate original plate with an outermost layer and a lithographic printing plate original plate without an outermost layer) are prepared.
Using two lithographic printing plate original plates, the halftone dot area ratio is obtained by the following method, and the halftone dot area ratio, which is an index of oxygen permeability, is calculated from the obtained halftone dot area ratio.
The two prepared lithographic printing plates were used on the Luxel PLATESTTER T-9800II manufactured by FUJIFILM Corporation equipped with an infrared semiconductor laser, respectively, with an outer drum rotation speed of 220 rpm (revolutions per minute) and laser outputs of 99.7 and 99. Exposure is performed under the conditions of 6.6, 99.5%, resolution 2,400 dpi (dot per inch, 1 inch = 2.54 cm), and extinction ratios of 1:14, 1:17, 1:19. At this time, the exposed image includes a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The obtained exposed lithographic printing original plate is attached to the plate cylinder of the printing machine LITHRONE26 manufactured by Komori Corporation without developing. After decelerating the water supply roller by 5% with respect to the plate cylinder, Efficiency-2 (manufactured by Fuji Film Co., Ltd.) / tap water = 2/98 (capacity ratio) dampening water and space color fusion G ink ink ( Using the standard automatic printing start method of LITHRONE26 using DIC Graphics Co., Ltd., after supplying dampening water and ink and developing on the machine, Tokubishi Art at a printing speed of 10,000 sheets per hour. (Made by Mitsubishi Paper Mills Limited, ream weight: 76.5 kg) Print 1,000 sheets on paper.
In the 1,000th printed matter, the density of the solid image portion (that is, the solid density) is DS, the density of the halftone dot portion is DT, and the halftone dot area ratio is derived by the following formula M: Murray-Davis. do. Subsequently, the obtained halftone dot area ratio value is substituted into the formula of the following formula OT to calculate the halftone dot area ratio.
Equation M: Halftone dot area ratio = (1-10- ^DT ) / (1-10- ^DS ) x 100
Formula OT: Halftone dot area ratio = (halftone dot area ratio of lithographic printing plate without outermost layer) / (halftone dot area ratio of lithographic printing plate with outermost layer)
The larger the value of the halftone dot area ratio, the better the oxygen permeability.

<Image recording layer>
The lithographic printing plate original plate according to the present disclosure has an image recording layer between the outermost layer and the support as described above.
The image recording layer in the present disclosure contains a polymerization initiator, a polymerizable compound, and an infrared absorber.
The image recording layer in the present disclosure is a negative image recording layer, and is preferably a water-soluble or water-dispersible negative image recording layer.
From the viewpoint of on-machine developability, the unexposed portion of the image recording layer in the present disclosure is preferably removable with at least one of dampening water and printing ink.

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

[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 preferably contains an electron-accepting polymerization initiator as the polymerization initiator.
The electron-accepting polymerization initiator is a compound that generates a polymerization initiator such as a radical by accepting one electron by electron transfer between molecules when the electron of the infrared absorber is excited by infrared exposure.
The electron-accepting polymerization initiator is a compound that generates a polymerization initiator such as a radical or a cation by energy of light, heat, or both, and is a known thermal polymerization initiator, a compound having a small bond of bond dissociation energy, and the like. 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.
The electron-accepting polymerization initiator is preferably an infrared photosensitive polymerization initiator.

Among the electron-accepting polymerization initiators, oxime ester compounds and onium salt compounds are preferable from the viewpoint of curability of the image recording layer. Among them, from the viewpoint of printing resistance, 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.

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

Examples of the counter anion of the iodonium salt compound and the sulfonium salt compound include a sulfonate anion, a carboxylate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, a p-toluene sulfonate anion, a tosylate anion, a sulfonamide anion or a sulfonimide. Anions are mentioned. Of these, sulfonamide anions or sulfonimide anions are preferable, and sulfonamide anions are more preferable.
As the sulfonamide anion, an aryl sulfonamide anion is preferable.
Further, as the sulfoneimide anion, a bisaryl sulfoneimide anion is preferable.
Specific examples of the sulfonamide anion or the sulfonamide anion include the compounds described in paragraph 0034 of WO 2019/013268.

Further, the electron-accepting polymerization initiator is preferably a compound represented by any of the following formulas (II) and (III) from the viewpoint of developability and UV printing resistance in the obtained lithographic printing plate. , Particularly the compound represented by the formula (II) is preferable.

In formulas (II) and (III), X represents a halogen atom, and R ³ , R ⁴ and R ⁵ each independently represent a monovalent hydrocarbon group having 1 to 20 carbon atoms.
In formula (II), it is preferable that X represents a halogen atom and R ^{3 represents an aryl group.}

Specific examples of the X in the formulas (II) and (III) include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Of these, a chlorine atom or a bromine atom is preferable because it has excellent sensitivity, and a bromine atom is particularly preferable.
Further, in the formulas (II) and (III), R ³ , R ⁴ and R ⁵ are preferably aryl groups independently of each other, and above all, from the viewpoint of excellent balance between sensitivity and storage stability, amides are used. Aryl groups substituted with groups are preferred.

Among the above electron-accepting polymerization initiators, the compound represented by the formula (IV) is particularly preferable.

In formula (IV), R ⁴ and R ⁵ each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. p and q each independently represent an integer from 1 to 5. However, p + q = 2 to 6.

Specific examples of the electron-accepting polymerization initiator represented by any of the above formulas (II) to (IV) include compounds represented by the following formulas, but the present disclosure is not limited thereto. No.

The minimum empty orbital (LUMO) of the electron-accepting polymerization initiator is preferably −3.00 eV or less, and more preferably −3.02 eV or less, from the viewpoint of improving sensitivity and making plate skipping less likely to occur. preferable.
The lower limit of the minimum empty orbital (LUMO) of the electron-accepting polymerization initiator is preferably -3.80 eV or more, and more preferably -3.50 eV or more.
In the present disclosure, the minimum empty orbital (LUMO) and the maximum occupied orbital (HOMO) described later are calculated by the following method.
First, when the compound to be calculated has a counterion that is not the main structure forming HOMO or LUMO, the counterion may be ignored.
Using the quantum chemistry calculation software Gaussian09, the structure optimization is DFT (B3L).
YP / 6-31G (d)).
The MO (molecular orbital) energy calculation is performed by DFT (B3LYP / 6-31 + G (d, p) / CPCM (solvent = methanol)) with the structure obtained by the above structural optimization.
The MO energy Ebare (unit: hartree) obtained by the above MO energy calculation is converted into Escaled (unit: eV) used as the values of HOMO and LUMO in the present disclosure by the following formula.
Escaled = 0.823168 x 27.2114 x Ebare-1.07634
Note that 27.2114 is simply a coefficient for converting hartree to eV, 0.823168 and -1.07634 are adjustment coefficients, and the calculated values of HOMO and LUMO of the compound to be calculated are actually measured. Determine to suit.

The electron-accepting polymerization initiator may be used alone 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, based on the total mass of the image recording layer. , 0.8% by mass to 20% by mass is particularly preferable.

[Electron-donated polymerization initiator (polymerization aid)]
The image recording layer in the present disclosure preferably contains an electron donating type polymerization initiator (also referred to as a polymerization aid) as a polymerization initiator.
The electron donating type polymerization initiator is a radical by donating one electron by intermolecular electron transfer to the orbital where one electron of the infrared absorber is missing when the electron of the infrared absorber is excited or moved intramolecularly by infrared exposure. It is a compound that generates a polymerization-initiated species such as.
The electron donating type polymerization initiator is preferably an electron donating type radical polymerization initiator.

From the viewpoint of printing resistance, the image recording layer preferably contains a borate compound as an electron donating type polymerization initiator.
The borate compound is preferably a tetraarylborate compound or a monoalkyltriarylborate compound, and more preferably a tetraarylborate compound, from the viewpoint of print resistance.
The counter cation contained in the borate compound is not particularly limited, but is preferably an alkali metal ion or a tetraalkylammonium ion, and more preferably a sodium ion, a potassium ion, or a tetrabutylammonium ion.
Further, the counter cation of the borate compound may be a cationic polymethine dye described as an infrared absorber in the present disclosure. For example, the above borate compound may be used as a counter cation of a cyanine dye.

Specific examples of the borate compound include sodium tetraphenylborate.

B-1 to B-9 are shown below as preferable specific examples of the electron donating type polymerization initiator, but it goes without saying that the present invention is not limited to these. Further, in the following chemical formula, Ph represents a phenyl group and Bu represents an n-butyl group.

Further, the maximum occupied orbital (HOMO) of the electron donating type polymerization initiator is preferably −6.00 eV or more, preferably −5.95 eV or more, from the viewpoint of improving sensitivity and making it difficult for plate skipping to occur. It is more preferable, and it is further preferable that it is −5.93 eV or more.
Further, the upper limit of the maximum occupied orbital (HOMO) of the electron donating type polymerization initiator is preferably −5.00 eV or less, and more preferably −5.40 eV or less.

As the electron donating type polymerization initiator, only one kind may be used, or two or more kinds may be used in combination.

The content of the electron donating type 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 resistance. It is more preferably to 25% by mass, and even more preferably 0.1% by mass to 20% by mass.

The polymerization initiator may be a compound in which the electron donating type polymerization initiator and the electron accepting type polymerization initiator form an anti-salt.
For example, it is preferable that the anion in the electron-donating polymerization initiator and the cation in the electron-accepting polymerization initiator form a counter-salt, and the electron-accepting polymerization initiator and the electron-donating polymerization initiator are preferable. More preferably, it is a compound in which a cation having an electron-accepting polymerization initiator structure and an anion having an electron-donating polymerization initiator structure form a salt. Specifically, it is preferably a compound in which an onium cation and a borate anion form an anti-salt, and more preferably a compound in which an iodonium cation or a sulfonium cation and a borate anion form an anti-salt. , A compound formed by forming a salt with a diaryliodonium cation or a triarylsulfonium cation and a tetraarylborate anion is particularly preferable.
Preferred embodiments of the anion in the electron-donating polymerization initiator and the cation in the electron-accepting polymerization initiator include the anion in the electron-donating polymerization initiator described above and the cation in the electron-accepting polymerization initiator described above. It is the same as the embodiment.
When the image recording layer contains an anion which is an electron donating type polymerization initiator and a cation which is an electron accepting type polymerization initiator (that is, when it contains the compound forming the above salt), the image recording layer. Shall include an electron-accepting polymerization initiator and the electron-donating polymerization initiator.
Further, the compound in which the electron donating type polymerization initiator and the electron accepting type polymerization initiator form an anti-salt may be used as an electron donating type polymerization initiator or as an electron accepting type polymerization initiator. good.
Further, the compound in which the electron donating type polymerization initiator and the electron accepting type polymerization initiator form a salt with respect to each other may be used in combination with the above-mentioned electron donating type polymerization initiator or the above-mentioned electron accepting type polymerization initiator. It may be used in combination with a polymerization initiator.

[Preferable Embodiment of Infrared Absorbent and Electron Donating Polymerization Initiator]
The image recording layer in the present disclosure is electron-donated polymerization from the HOMO value of the infrared absorber HOMO-electron-donating polymerization initiator (that is, the HOMO value of the infrared absorber) from the viewpoint of improving sensitivity and printing resistance. The value obtained by subtracting the HOMO value of the initiator) is preferably 0.70 eV or less, and more preferably 0.70 eV to −0.10 eV.
A negative value means that the HOMO of the electron donating polymerization initiator is higher than that of the infrared absorber.

[Preferable aspects of electron-accepting polymerization initiator and infrared absorber]
The image recording layer in the present disclosure is an infrared ray from the LUMO value of the electron-accepting polymerization initiator LUMO-infrared absorber (that is, the LUMO value of the electron-accepting polymerization initiator) from the viewpoint of improving sensitivity and printing resistance. The value obtained by subtracting the LUMO value of the absorber) is preferably 1.00 eV or less, more preferably 0.80 eV or less, and further preferably 0.70 eV or less. The LUMO value of the electron-accepting polymerization initiator LUMO-infrared absorber is preferably 1.00 eV to −0.10 eV, and more preferably 0.80 eV to 0.30 eV.
A negative value means that the LUMO of the infrared absorber is higher than that of the electron-accepting polymerization initiator.

[Polymerizable compound]
The image recording layer in the present disclosure contains a polymerizable compound.
In the present disclosure, the polymerizable compound means a compound having a polymerizable group.
The polymerizable group is not particularly limited and may be a known polymerizable group, but an ethylenically unsaturated group is preferable. The polymerizable group may be a radically polymerizable group or a cationically polymerizable group, but is preferably a radically polymerizable group.
Examples of the radically polymerizable group include 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 (weight average molecular weight when having a molecular weight distribution) is preferably 50 or more and less than 40,000.

The polymerizable compound used in the present disclosure may be, for example, a radically polymerizable compound or a cationically polymerizable compound, but is an addition polymerizable compound having at least one ethylenically unsaturated bond (ethylenic). It is preferably an unsaturated compound).
The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, and more preferably a compound having two or more terminal ethylenically unsaturated bonds. The polymerizable compound has a chemical form such as, for example, a monomer, a prepolymer, that is, a dimer, a trimer or an oligomer, or a mixture thereof.
Among them, the polymerizable compound preferably contains a trifunctional or higher-functional polymerizable compound, more preferably a 7-functional or higher-functional polymerizable compound, and 10-functional or higher-functional polymerizable compound from the viewpoint of UV printing resistance. It is more preferable to contain a compound. Further, the polymerizable compound preferably contains a trifunctional or higher (preferably 7 or higher, more preferably 10 or higher) ethylenically unsaturated compound from the viewpoint of UV printing resistance in the obtained flat plate printing plate. It is more preferable to contain a trifunctional or higher (preferably 7 or higher, more preferably 10 or higher) (meth) acrylate compound.

[Oligomer]
As the polymerizable compound contained in the image recording layer, it is preferable to contain a polymerizable compound which is an oligomer (hereinafter, also simply referred to as “oligomer”).
In the present disclosure, the oligomer represents a polymerizable compound having a molecular weight (weight average molecular weight in the case of having a molecular weight distribution) of 600 or more and 30,000 or less and containing at least one polymerizable group.
Preferred examples of the molecular weight of the oligomer include 1,000 or more and 25,000 or less.
Further, from the viewpoint of excellent chemical resistance and UV printing resistance, the molecular weight of the oligomer is preferably 1,000 or more and 5,000 or less.

Further, from the viewpoint of improving UV printing resistance, the number of polymerizable groups in one molecule of the oligomer is preferably 2 or more, more preferably 3 or more, further preferably 6 or more, and 10 or more. Is particularly preferable.
The upper limit of the polymerizable group in the oligomer is not particularly limited, but the number of polymerizable groups is preferably 20 or less.

From the viewpoint of UV printing resistance and on-machine developability, the oligomer preferably has 7 or more polymerizable groups and a molecular weight of 1,000 or more and 10,000 or less, and is polymerizable. It is more preferable that 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.
When the oligomer is contained as the polymerizable compound, a polymer component that may occur in the process of producing the oligomer may also be contained.

From the viewpoint of UV printing resistance and on-machine developability, the oligomer may have 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. It is preferable to have a compound having a urethane bond.
In the present disclosure, the epoxy residue refers to a structure formed by an epoxy group, and means, for example, a structure similar to the structure obtained by the reaction of an acid group (carboxylic acid group or the like) with an epoxy group.

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

Wherein (Ac-1) and formula ^{(Ac-2), L 1} ~ L 4 each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, the wavy line portion coupled to other structures Represents a position.
Each of L ¹ to L ⁴ is 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 more preferable to have. The alkylene group may have a branched or ring structure, but is preferably a linear alkylene group.

The wavy line portion in the formula (Ac-1) or the formula (Ac-2) can be independently bonded directly to the wavy line portion in the group represented by the following formula (Ae-1) or the formula (Ae-2). preferable.

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

Further, as the compound having a urethane bond, a compound in which a polymerizable group is introduced into a polyurethane obtained by a reaction between a polyisocyanate compound and a polyol compound by a polymer reaction may be used.
For example, a compound having a urethane bond may be obtained by reacting a polyurethane oligomer obtained by reacting a polyol compound having an acid group with a polyisocyanate compound with a compound having an epoxy group and a polymerizable group.

(Compound with ester bond)
The number of polymerizable groups in the compound having an ester bond, which is an example of the oligomer, is preferably 3 or more, and 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.
Further, the number of polymerizable groups in the compound having an epoxy residue is preferably 2 to 6, and more preferably 2 to 3.
The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

Commercially available products are shown below as specific examples of oligomers, but the oligomers used in the present disclosure are not limited thereto.
Commercially available oligomers include UA510H, UA-306H, UA-306I, and UA-306T (all from Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, and UV7620EA (all from Nippon Synthetic Chemical Industry Co., Ltd.). , U-15HA (Shin Nakamura Chemical Industry Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, EBECRYL860 (all of which are Daisel Ornex Co., Ltd.) and the like.

The content of the oligomer is 30% by mass to 100% by mass with respect to the total mass of the polymerizable compound in the image recording layer from the viewpoint of improving chemical resistance, UV printing resistance, and suppression of on-machine developing residue. It is preferably 50% by mass to 100% by mass, more preferably 80% by mass to 100% by mass.

[Small molecule polymerizable compound]
The polymerizable compound may further contain a polymerizable compound other than the above oligomer.
The polymerizable compound other than the oligomer is preferably a small molecule polymerizable compound from the viewpoint of chemical resistance. The low molecular weight polymerizable compound may be in a chemical form such as a monomer, a dimer, a trimer, or a mixture thereof.
Further, as the low molecular weight polymerizable compound, at least one polymerization selected from the group consisting of a polymerizable compound having three or more ethylenically unsaturated groups and a polymerizable compound having an isocyanulous ring structure from the viewpoint of chemical resistance. It is preferably a sex compound.

In the present disclosure, the low molecular weight polymerizable compound means a polymerizable compound having a molecular weight (in the case of having a molecular weight distribution, a weight average molecular weight) of 50 or more and less than 600.
The molecular weight of the low molecular weight polymerizable compound is preferably 100 or more and less than 600, and more preferably 300 or more and less than 600, from the viewpoint of excellent chemical resistance, UV printing resistance and resistance to on-machine development residue. 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 the oligomer (when two or more kinds of low molecular weight polymerizable compounds are contained, the total amount thereof), chemical resistance, UV printing resistance and on-machine resistance. From the viewpoint of suppressing the development residue, the ratio of the oligomer to the low molecular weight polymerizable compound (oligomer / low molecular weight polymerizable compound) is preferably 10/1 to 1/10 on a mass basis. It is more preferably 1 to 3/7, and even more preferably 10/1 to 7/3.

Specific examples of the small molecule polymerizable compound include the compounds described in paragraphs 882 to 0086 of International Publication No. 2019/013268.

The details of the structure of the polymerizable compound, whether it is used alone or in combination, and the amount of addition can be arbitrarily set.
Above all, the image recording layer preferably contains two or more kinds of polymerizable compounds from the viewpoint of UV printing resistance.
The content of the polymerizable compound (when two or more kinds of the polymerizable compound are contained, the total content of the polymerizable compound) is preferably 5% by mass to 75% by mass with respect to the total mass of the image recording layer. It is more preferably 10% by mass to 70% by mass, and further preferably 15% by mass to 60% by mass.

[Infrared absorber]
The image recording layer in the present disclosure contains an infrared absorber.
The infrared absorber is not particularly limited, and examples thereof include pigments and dyes.
As the dye used as the infrared absorber, a commercially available dye and, for example, a known dye described in a document such as "Dye Handbook" (edited by the Society of Synthetic Organic 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, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complexes. Can be mentioned.

Among these dyes, preferred ones include cyanine dye, squarylium dye, pyrylium salt, nickel thiolate complex, and indorenin cyanine dye. More preferably, cyanine pigments and indorenin cyanine pigments are mentioned. Of these, the cyanine pigment is particularly preferable.

The infrared absorber is preferably a cationic polymethine dye having an oxygen atom, a nitrogen atom, or a halogen atom at the meso position. Preferred examples of the cationic polymethine dye include cyanine dye, pyrylium dye, thiopyrylium dye, and azulenium dye, and cyanine dye is preferable from the viewpoint of easy availability and solvent solubility during the introduction reaction.

Specific examples of the cyanine dye include the compounds described in paragraphs 0017 to 0019 of JP-A-2001-133769, paragraphs 0016 to 0021 of JP-A-2002-0233360, and paragraphs 0012 to 0037 of JP-A-2002-040638. , Preferably paragraphs 0034 to 0041 of JP-A-2002-278057, paragraphs 0080-0086 of JP-A-2008-195018, and particularly preferably paragraphs 0035 of JP-A-2007-90850. Examples thereof include the compounds described in 0043 and the compounds described in paragraphs 0105 to 0113 of JP2012-206495A.
Further, the compounds described in paragraphs 0008 to 0009 of JP-A-5-5005 and paragraphs 0022 to 0025 of JP-A-2001-222101 can also be preferably used.
As the pigment, the compounds described in paragraphs 0072 to 0076 of JP-A-2008-195018 are preferable.

Further, as the infrared absorber, an infrared absorber that decomposes by infrared exposure can also be preferably used.
As the infrared absorber that decomposes by infrared exposure, those described in JP-A-2008-544322, International Publication No. 2016/027886, International Publication No. 2017/141882, or International Publication No. 2018/0432559 are preferably used. Can be used.
Further, as the infrared absorber that decomposes by infrared exposure, the above-mentioned decomposition type infrared absorber used for the outermost layer may be used.

Only one kind of infrared absorber may be used, or two or more kinds may be used in combination.
Further, a pigment and a dye may be used in combination as an infrared absorber.

The content of the infrared absorber is 0.1% by mass to 10.0% by mass with respect to the total mass of the image recording layer.
Is preferable, and 0.5% by mass to 5.0% by mass is more preferable.

〔particle〕
The image recording layer in the present disclosure preferably contains particles from the viewpoint of developability and UV printing resistance. The particles may be inorganic particles or organic particles.
Among them, the particles preferably contain organic particles, and more preferably polymer particles.
That is, the image recording layer in the present disclosure preferably contains polymer 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.

[Polymer particles]
Examples of the polymer particles include particles containing an addition polymerization type resin (that is, addition polymerization type polymer particles), particles containing a polyaddition type resin (that is, polyaddition type polymer particles), and particles containing a polycondensation type resin (that is, that is). , Polycondensation type polymer particles), etc., among which addition polymerization type polymer particles or polyaddition type polymer particles are preferable.
Further, the polymer particles may be particles containing a thermoplastic resin (that is, thermoplastic polymer particles) from the viewpoint of enabling heat fusion.

Further, the polymer particles may be in the form of microcapsules, microgels (that is, crosslinked polymer particles) and the like.

The polymer particles are selected from the group consisting of thermoplastic polymer particles, heat-reactive polymer particles, polymer particles having a polymerizable group, microcapsules containing a hydrophobic compound, and microgels (crosslinked polymer particles). Is preferable. Of these, polymer particles having a polymerizable group are preferable.
In a particularly preferred embodiment, the polymer particles contain at least one ethylenically unsaturated group. The presence of such polymer particles has the effect of enhancing the printing durability of the exposed portion and the on-machine developability of the unexposed portion.

As the thermoplastic polymer particles, Research Disclosure No. 1 of January 1992. The thermoplastic polymer particles described in 33303, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250, European Patent No. 913647, and the like are preferable.

Specific examples of the thermoplastic resin constituting the thermoplastic polymer particles include ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, and a polyalkylene structure. Examples thereof include homopolymers or copolymers of monomers such as acrylates or methacrylates having the above, or mixtures thereof.

The thermoplastic polymer particles preferably contain a structural unit formed of an aromatic vinyl compound and a thermoplastic resin having a structural unit having a nitrile group, from the viewpoint of ink inking property and UV printing resistance.

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

The content of the structural unit formed by the aromatic vinyl compound is preferably higher than the content of the structural unit having a nitrile group, which will be described later, from the viewpoint of ink inking property, with respect to the total mass of the thermoplastic resin. 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.
Examples of the monomer having a nitrile group include acrylonitrile compounds, and (meth) acrylonitrile is preferable.
As the structural unit having a nitrile group, a structural unit formed of (meth) acrylonitrile is preferable.

The content of the structural unit having a nitrile group is preferably smaller than the content of the structural unit formed by the above aromatic vinyl compound from the viewpoint of ink inking property, and is 55% by mass with respect to the total mass of the resin. It is more preferably to 90% by mass, more preferably 60% by mass to 85% by mass.

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

From the viewpoint of UV printing resistance and chemical resistance, the resin contained in the thermoplastic polymer particles preferably further has a structural unit formed of the N-vinyl heterocyclic compound.
Examples of the N-vinyl heterocyclic compound include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinic acidimide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylpyrrolidone. Vinyl imidazole is mentioned, and N-vinylpyrrolidone is preferable.

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

The resin contained in the thermoplastic polymer particles may contain a structural unit having an acidic group, but it is preferable not to contain a structural unit having an acidic group from the viewpoint of on-machine developability and ink inking property. ..
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 measuring method based on JIS K 0070-1992.

The thermoplastic resin contained in the thermoplastic polymer particles may contain a structural unit containing a hydrophobic group from the viewpoint of ink inking property.
Examples of the hydrophobic group include an alkyl group, an aryl group, an aralkyl group and the like.
As the structural unit containing the hydrophobic group, a structural unit formed of an alkyl (meth) acrylate compound, an aryl (meth) acrylate compound, or an aralkyl (meth) acrylate compound is preferable, and the structural unit is formed of an alkyl (meth) acrylate compound. The structural unit is more preferable.

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

The thermoplastic resin contained in the thermoplastic polymer particles preferably has a hydrophilic group from the viewpoint of UV printing resistance and on-machine 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 carboxy group, a hydroxy group, an amino group, a nitrile group, and a polyalkylene oxide structure.
The hydrophilic group is preferably a group having a polyalkylene oxide structure, a group having a polyester structure, or a sulfonic acid group from the viewpoint of UV printing resistance and on-machine developability, and the polyalkylene oxide structure is preferably used. It is more preferably a group having or a sulfonic acid group, and further preferably a group having a polyalkylene oxide structure.

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.
Further, from the viewpoint of on-machine developability, it is preferable to have a polypropylene oxide structure as the polyalkylene oxide structure among the above hydrophilic groups, and it is more preferable to have 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, further preferably 5 to 200, and 8 to 8. It is particularly preferably 150.

Further, from the viewpoint of on-machine developability, the group represented by the formula Z described later is preferable as the hydrophilic group.

Further, among the hydrophilic groups of the thermoplastic resin, the group represented by the following formula PO is preferable.

Wherein PO, ^{L P} each independently represent an alkylene group, ^{R P} represents a hydrogen atom or an alkyl group, n represents an integer of 1 to 100.
Wherein PO, L ^P are each independently an ethylene group, preferably a 1-methylethylene group, or a 2-methylethylene group, more preferably an ethylene group.
Wherein 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, a hydrogen atom or a C 1-4 It is more preferably an alkyl group, and particularly preferably a hydrogen atom or a methyl group.
In the formula PO, n is preferably an integer of 1 to 10, and more preferably an integer of 1 to 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, based on the total mass of the resin.

The resin contained in the thermoplastic polymer particles may further contain other structural units.
The other structural units may contain a structural unit other than the above-mentioned structural units without particular limitation, and examples thereof include structural units formed of an acrylamide compound, a vinyl ether compound, or the like.

The content of the 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.

Examples of the heat-reactive polymer particles include polymer particles having a heat-reactive group.
The heat-reactive resin particles form a hydrophobic region by cross-linking due to a heat reaction and the change of functional groups at that time.

The heat-reactive group in the polymer particles having a heat-reactive group may be a functional group that undergoes any reaction as long as a chemical bond is formed, but a polymerizable group is preferable, and as an example, it is preferable. Eethylene unsaturated groups (eg, acryloyl group, methacryloyl group, vinyl group, allyl group, etc.), cationically polymerizable groups (eg, vinyl group, vinyloxy group, epoxy group, oxetanyl group, etc.), addition reaction Isocyanato group or a block thereof, an epoxy group, a vinyloxy group and a functional group having an active hydrogen atom which is a reaction partner thereof (for example, an amino group, a hydroxy group, a carboxy group, etc.), a carboxy group for performing a condensation reaction and a reaction. Preferred examples thereof include a hydroxy group or an amino group as a partner, an acid anhydride for carrying out a ring-opening addition reaction, and an amino group or a hydroxy group as a reaction partner.
The resin having the heat-reactive group may be an addition polymerization type resin, a polyaddition type resin, a polycondensation type resin, or a thermoplastic resin.

As the microcapsules, for example, as described in JP-A-2001-277740 and JP-A-2001-277742, those containing at least a part (preferably a hydrophobic compound) of the constituents of the image recording layer are preferable. .. In the image recording layer containing microcapsules as polymer particles, a hydrophobic component (that is, a hydrophobic compound) among the constituent components of the image recording layer is encapsulated in the microcapsules, and the hydrophilic component (that is, a hydrophilic compound) is microscopically contained. A configuration contained outside the capsule is a preferred embodiment.
Known synthetic methods can be applied to obtain microcapsules containing the components of the image recording layer.

The microgel (crosslinked polymer particles) can contain a part of the constituents of the image recording layer on at least one of the surface or the inside thereof. 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 original plate and the printing durability of the obtained lithographic printing plate.
A known synthetic method can be applied to obtain a microgel containing the constituents of the image recording layer.

The polymer particles are an adduct of a polyhydric phenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate from the viewpoint of printing resistance, stain resistance and storage stability of the obtained flat plate printing plate. The polyadductate polymer particles obtained by the reaction of the polyhydric isocyanate compound and the compound having active hydrogen are preferable.
As the polyvalent phenol compound, a compound having a plurality of benzene rings having a phenolic hydroxy group is preferable.
As the compound having active hydrogen, a polyol compound or a polyamine compound is preferable, a polyol compound is more preferable, and at least one compound selected from the group consisting of propylene glycol, glycerin and trimethylolpropane is further preferable.
Further, water may be used as the compound having active hydrogen. When water is used, the amine generated by the reaction between the isocyanate group of the polyhydric isocyanate compound and water can form a urea bond to form particles.
As the particles of the resin obtained by the reaction of the polyhydric phenol compound having two or more hydroxy groups in the molecule, the polyhydric isocyanate compound which is an adduct of isophorone diisocyanate, and the compound having active hydrogen, the first international release. Preferred examples thereof include microgels obtained by the preparation method described in paragraphs 0230 to 0234 of No. 2018/043259.

Further, the polymer particles have a hydrophobic main chain from the viewpoint of printing resistance and solvent resistance of the obtained flat plate printing plate, and i) have a nitrile group directly bonded to the hydrophobic main chain. Additionally polymerized polymer particles containing both a constituent unit and ii) a constituent unit having a pendant group containing a hydrophilic polyalkylene oxide segment are preferred.
Specifically, the particles described in paragraph 0156 of JP-A-2019-64269 are preferable as such addition polymerization type polymer particles.

(Group represented by formula Z)
The polymer particles in the present disclosure preferably have a group represented by the following formula Z as a hydrophilic group.
In particular, the polymer particles in the present disclosure are preferably addition polymerization type polymer particles having a hydrophilic group including a group represented by the following formula Z.
Formula Z: * -Q-W-Y
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, and Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophilic structure. A monovalent group having a hydrophobic structure is represented, either W or Y has a hydrophilic structure, and * represents a binding site with another structure.
Further, it is preferable that any of the hydrophilic structures contained in the formula Z contains a polyalkylene oxide structure.

Q in the above formula Z is preferably a divalent linking group having 1 to 20 carbon atoms, and more preferably a divalent linking group having 1 to 10 carbon atoms.
Further, 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 more preferably a phenylene group, an ester bond, or an amide bond. ..

The divalent group having a hydrophilic structure in W of the above formula Z is preferably a group containing a polyalkylene oxide structure, and is a polyalkylene oxy group or -CH ₂ CH at one end of the polyalkylene oxy group. It is preferably a group to which ₂ NR ^{W − is bound.} Incidentally, R ^W represents a hydrogen atom or an alkyl group, subsequent R ^W also the same.
^The divalent group having a hydrophobic structure in the W of formula ^{^{Z, -R WA -, - O}} -R WA -O -, - R W N-R WA -NR W -, - OC (= O) - R ^WA -O-, or, -OC (= ^O) is preferably ^-R WA -O-. The ^RWAs are independently linear, branched or cyclic alkylene groups having 6 to 120 carbon atoms, haloalkylene groups having 6 to 120 carbon atoms, arylene groups having 6 to 120 carbon atoms, and 7 to 120 carbon atoms. It represents an alkanerylene group (a divalent group obtained by removing one hydrogen atom from an alkylaryl group) or an aralkylene group having 7 to 120 carbon atoms.

The monovalent group having a hydrophilic structure in Y of the above formula Z is -OH, -C (= O) OH, a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the end, or a hydrogen atom or an alkyl at the end. it is preferably bound group - at the other end of the polyalkyleneoxy group is a group _{_{^{-CH 2 CH 2 N (R W}}} ). Among them, the monovalent group having a hydrophilic structure is preferably a group containing a polyalkylene oxide structure, a polyalkylene oxy group having a hydrogen atom or an alkyl group at the end, or a hydrogen atom or an alkyl group at the end. in polyalkyleneoxy groups other end to the _{_{^{-CH 2 CH 2 N (R W}}} ) is - is bonded group.
The monovalent group having a hydrophobic structure in Y of the above formula Z is 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, and the like. It may be an alcoholyl group (alkylaryl group) having 7 to 120 carbon atoms, an aralkyl group having 7 to 120 carbon atoms, -OR ^WB , -C (= O) OR ^WB , or -OC (= O) R ^WB. preferable. ^RWB represents an alkyl group having 6 to 20 carbon atoms.

The polymer particles having a group represented by the above formula Z are more preferably divalent groups in which W has a hydrophilic structure from the viewpoints of print resistance, fillability and on-machine developability. It is more preferable that Q is a phenylene group, an ester bond or an amide bond, W is a polyalkyleneoxy group, and Y is a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the end.
The group represented by the formula Z may function as a dispersible group for enhancing the dispersibility of the polymer particles.

The polymer particles in the present disclosure preferably have a polymerizable group (preferably an ethylenically unsaturated group) from the viewpoint of print resistance and on-machine developability, and in particular, may have a polymerizable group on the surface. More preferred. By using the polymer particles having a polymerizable group, it becomes easy to suppress plate skipping (preferably UV plate skipping), and printing resistance (preferably UV printing resistance) is also enhanced.

The polymer particles in the present disclosure are preferably resin particles having a hydrophilic group and a polymerizable group from the viewpoint of printing resistance.
The polymerizable group may be a cationically polymerizable group or a radically polymerizable group, but from the viewpoint of reactivity, it is preferably a radically polymerizable group.
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, and a vinylphenyl group (styryl group), a (meth) acryloxy group, or a (meth) acryloxy group is preferable. A (meth) acrylamide group is more preferred, and a (meth) acryloxy group is particularly preferred.
Further, the resin constituting the polymer particles having a polymerizable group preferably has a structural unit having a polymerizable group.
In addition, a polymerizable group may be introduced on the surface of the polymer particles by a polymer reaction.

Further, the polymer particles preferably contain a heavy addition type resin having a urea bond from the viewpoints of printing resistance, inking property, on-machine developability, and ability to suppress development residue during on-machine development, and the following formula is preferable. It is more preferable to contain a heavy addition type resin having a structure obtained by at least reacting the isocyanate compound represented by (Iso) with water, and at least reacting the isocyanate compound represented by the following formula (Iso) with water. It is particularly preferable that the polyoxyalkylene structure contains a polyadditive resin having a polyethylene oxide structure and a polypropylene oxide structure. Further, the particles containing the heavy addition type resin having a urea bond are preferably microgels.

In the formula (Iso), n represents an integer from 0 to 10.

As an example of the reaction between the isocyanate compound represented by the above formula (Iso) and water, the reaction shown below can be mentioned. The following example is an example using n = 0, 4,4-isomer.
As shown below, when the isocyanate compound represented by the above formula (Iso) is reacted with water, a part of the isocyanate group is hydrolyzed by water to generate an amino group, and the generated amino group and isocyanate group are used. React to form a urea bond and form a dimer. Further, the following reaction is repeated to form a heavy addition type resin having a urea bond.

Further, in the following reaction, by adding a compound having reactivity with an isocyanate group such as an alcohol compound or an amine compound (a compound having active hydrogen), the structure of the alcohol compound, the amine compound or the like is added with a urea bond. It can also be introduced into the mold resin.
As the compound having active hydrogen, the above-mentioned compound having active hydrogen is preferably mentioned.

Further, the heavy addition type resin having a 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 part represents the connection position with other structures.

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

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

As the particles (preferably polymer particles), only one kind may be used, or two or more kinds may be used in combination.

The content of the particles (preferably polymer particles) is preferably 5% by mass to 90% by mass, preferably 10% by mass to 90% by mass, based on the total mass of the image recording layer from the viewpoint of developability and print resistance. It 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 other than the above-mentioned components.
Examples of other components include binder polymers, color formers, chain transfer agents, small molecule hydrophilic compounds, fat sensitizers, and other additives.

[Binder polymer]
The image recording layer may contain a binder polymer, if desired.
Here, the binder polymer refers to a polymer other than polymer particles, that is, a polymer that is not in the form of particles.
Further, the binder polymer excludes the ammonium salt-containing polymer in the oil-sensitive agent and the polymer used as a surfactant.

As the binder polymer, a known binder polymer (for example, (meth) acrylic resin, polyvinyl acetal resin, polyurethane resin, etc.) used for the image recording layer of the platen printing plate original plate can be preferably used.
As an example, a binder polymer (hereinafter, also referred to as a binder polymer for on-machine development) used in the machine-developed lithographic printing plate original plate will be described in detail.
As the binder polymer for on-machine development, a binder polymer having an alkylene oxide chain is preferable. The binder polymer having an alkylene oxide chain may have a poly (alkylene oxide) moiety in the main chain or the side chain. Further, it may be a graft polymer having poly (alkylene oxide) in the 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.
When the main chain has a poly (alkylene oxide) moiety, a polyurethane resin is preferable.
When the polymer of the main chain has a poly (alkylene oxide) moiety in the side chain, the polymer of the main chain is (meth) acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, polystyrene resin, novolak type. Examples thereof include phenol resin, polyester resin, synthetic rubber and natural rubber, and (meth) acrylic resin is particularly preferable.

Further, as another preferable example of the binder polymer, a high molecular weight polymer chain having a polyfunctional thiol having 6 or more functionalities or 10 functionalities as a nucleus and being bonded to the nucleus by a sulfide bond, and the polymer chain having a polymerizable group. Examples thereof include molecular compounds (hereinafter, also referred to as star-shaped polymer compounds).
As the star-shaped polymer compound, for example, the compound described in JP-A-2012-148555 can be preferably used.

The star-shaped polymer compound contains a polymerizable group such as an ethylenically unsaturated bond for improving the film strength of the image portion as described in JP-A-2008-195018, with a main chain or a side chain, preferably a side chain. Examples include those held in the chain. The polymerizable group of the star-shaped polymer compound forms crosslinks between the molecules of the star-shaped polymer compound, and curing is promoted.
As the polymerizable group, an ethylenically unsaturated group such as a (meth) acrylic group, a vinyl group, an allyl group, a vinylphenyl group (styryl group), an epoxy group and the like are preferable, and a (meth) acrylic group, a vinyl group and a vinylphenyl are preferable. A group (styryl group) is more preferable from the viewpoint of polymerization reactivity, and a (meth) acrylic 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 the 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 40,000 or more, and more preferably 40,000 to 300,000 in terms of polystyrene by the GPC method.
If the binder polymer does not have a polymerizable group, the weight average molecular weight (Mw) is preferably 10,000 to 300,000.

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

The binder polymer may be used alone or in combination of two or more.

The binder polymer can be contained in the image recording layer in an arbitrary amount, 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 may contain a color former.
The color-developing agent is preferably an acid color-developing agent. Further, the color former preferably contains a leuco compound.
The "color former" used in the present disclosure means a compound having a property of developing or decoloring a color or decoloring by a stimulus such as light or acid and changing the color of the image recording layer, and the "acid color former" is used. It means a compound having a property of developing or decoloring and changing the color of an image recording layer by heating in a state of receiving an electron-accepting compound (for example, a proton such as an acid).
The acid color former has a partial skeleton such as lactone, lactam, salton, spiropyrane, ester, and amide, and is colorless and the partial skeleton is rapidly ring-opened or cleaved when it comes into contact with an electron-accepting compound. Compounds are preferred.

Examples of the acid color former include the compounds described in paragraphs 0184 to 0191 of JP-A-2019-18412.

Among them, the color former is preferably at least one compound selected from the group consisting of a spiropyran compound, a spiroxazine compound, a spirolactone compound, and a spirolactam compound from the viewpoint of color development.
As the hue of the color former after color development, it is preferable to have maximum absorption in the range of 450 nm to 650 nm from the viewpoint of visibility. The color of the color-developing agent after color development is preferably red, purple, blue, or black-green.

Further, as the coloring agent (preferably an acid coloring agent), it is preferable to use a leuco dye from the viewpoint of enhancing the visibility of the exposed portion.
Here, the leuco dye is not particularly limited as long as it is a dye having a leuco structure, but it is preferably having a spiro structure, and more preferably a spirolactone ring structure.
Further, the leuco dye is preferably a leuco dye having a phthalide structure or a fluorane structure from the viewpoint of enhancing the visibility of the exposed portion.

Further, the color-developing agent (preferably an acid color-developing agent) is a leuco dye having the above-mentioned phthalide structure or fluorane structure from the viewpoint of enhancing the visibility of the exposed portion, and is the following formulas (Le-1) to (Le-3). ) Is preferable, and a compound represented by the following formula (Le-2) is more preferable.

In the formulas (Le-1) to (Le-3), ERG independently represents an electron donating group, and X ₁ to X ₄ independently represent a hydrogen atom, a halogen atom, or a dialkylanilino. _{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 Y _{1 represents a group.} When N, X ₁ does not exist, when Y ₂ is N, X ₄ does not exist, Ra ₁ represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb ₁ to Rb ₄ Independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

The electron donating groups in the ERGs of the formulas (Le-1) to (Le-3) include amino groups, alkylamino groups, arylamino groups, and heteroaryls from the viewpoint of color development and visibility of the exposed portion. Amino group, dialkylamino group, monoalkyl monoarylamino group, monoalkyl monoheteroarylamino group, diarylamino group, diheteroarylamino group, monoarylmonoheteroarylamino group, alkoxy group, allyloxy group, heteroallyloxy group , Or an alkyl group, preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, It is more preferably a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, or an allyloxy group, and a monoalkyl monoarylamino group, a diarylamino group, a diheteroarylamino group, or a monoarylmono. It is more preferably a heteroarylamino group, and particularly preferably a monoalkyl monoarylamino group.
The electron donating group in the ERG is an aryl group having a substituent at at least one ortho position or a hetero having a substituent at at least one ortho position from the viewpoint of color development and visibility of the exposed portion. It is preferably a disubstituted amino group having an aryl group, more preferably a disubstituted amino group having a substituent at at least one ortho position and a phenyl group having an electron donating group at the para position. preferable. Further, for the same reason, the electron-donating group in the ERG includes a phenyl group having a substituent at at least one ortho-position and an electron-donating group at the para-position, and an aryl group or a heteroaryl group. It is more preferably an amino group having an electron donating group, a phenyl group having a substituent at at least one ortho position and an electron donating group at the para position, and an aryl group or an electron donating group having an electron donating group. It is particularly preferable that it is an amino group having a heteroaryl group having.
Here, in the present disclosure, the ortho position in an aryl group or a heteroaryl group other than the phenyl group is next to the above-mentioned 1-position when the bonding position with the other structure of the aryl group or the heteroaryl group is the 1-position. It refers to the bonding position (for example, the second position, etc.).
The electron-donating group of the aryl group or the heteroaryl group includes an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, and a dialkylamino group from the viewpoint of color development and visibility of the exposed portion. A monoalkyl monoarylamino group, a monoalkyl monoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoaryl monoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroarryloxy group, or an alkyl group. It is preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, and particularly preferably an alkoxy group.

_X 1 ~ _{X 4} in the formula (Le-1) ~ formula (Le-3) are each independently, from the viewpoint of enhancing the visibility of the exposure unit, a hydrogen atom, or, preferably a chlorine atom, a hydrogen atom Is more preferable.
_{X 5} to X ₁₀ in the formula (Le-2) or the formula (Le-3) are independently hydrogen atom, halogen atom, alkyl group, aryl group, amino group, from the viewpoint of enhancing the visibility of the exposed part. Alkylamino group, arylamino group, heteroarylamino group, dialkylamino group, monoalkyl monoarylamino group, monoalkyl monoheteroarylamino group, diarylamino group, diheteroarylamino group, monoaryl monoheteroarylamino group, A hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, or a cyano group is preferable, and a hydrogen atom, a halogen atom, an alkyl group, etc. It is more preferably an aryl group, an alkoxy group, or an aryloxy group, further preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and particularly preferably a hydrogen atom.
_{It is preferable that at least one of Y 1} and Y ₂ in the formulas (Le-1) to (Le-3) is C from the viewpoint of enhancing the visibility of the exposed portion, _{and both Y 1} and Y ₂ are used. It is more preferably C.
_{Ra 1} in the formula (Le-3) is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group, from the viewpoint of enhancing the visibility of the exposed portion.
_{Each of Rb 1} to Rb ₄ in the formula (Le-1) is preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, and a methyl group, independently from the viewpoint of enhancing the visibility of the exposed portion. Is particularly preferable.

Further, the leuco dye having the phthalide structure or the fluorane structure may be a compound represented by any of the following formulas (Le-4) to (Le-6) from the viewpoint of enhancing the visibility of the exposed portion. More preferably, it is a compound represented by the following formula (Le-5).

Wherein (Le-4) ~ formula (Le-6), ERG each independently represents an electron donating _group, X 1 ~ _{X 4} are each independently a hydrogen atom, a halogen atom, or a dialkyl anilino Represents a group, Y ₁ and Y ₂ independently represent C or N, where X ₁ does not exist _{when Y 1} is N and X ₄ exists _{when Y 2 is N.} Instead, Ra ₁ represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb ₁ to Rb ₄ independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

_{ERG, X 1} to X ₄ , Y ₁ , Y ₂ , Ra ₁ and Rb ₁ to Rb ₄ in the formulas (Le-4) to (Le-6) are the formulas (Le-1) to the formulas (Le-1) to the formulas (Le-1) to Rb 4, respectively. le-3) _ERG _{_{in, X 1 ~ X 4, Y}} 1, Y 2, Ra 1 and have _the same meanings as Rb 1 ~ Rb _4, preferable embodiments thereof are also the same.

Further, the leuco dye having a phthalide structure or a fluorine structure may be a compound represented by any of the following formulas (Le-7) to (Le-9) from the viewpoint of enhancing the visibility of the exposed portion. Further, it is particularly preferable that the compound is represented by the following formula (Le-8).

Wherein (Le-7) ~ formula _{(Le-9), X 1} ~ X 4 are each independently a hydrogen atom, a halogen atom or a dialkyl anilino group, _{Y 1} and _{Y 2} are each independently Represents C or N, where X ₁ is absent _{when Y 1} _{is N, X 4} is absent _{when Y 2} is N, _{and Ra 1} to Ra ₄ are independent hydrogens, respectively. Representing an atom, an alkyl group, or an alkoxy group, Rb ₁ to Rb ₄ independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, and Rc ₁ and Rc ₂ each independently represent an aryl. Represents a group or a heteroaryl group.

_X 1 _- X 4 in formula (Le-7) to Formula (Le-9), _{Y 1} and _{Y 2} has the formula _{_{(Le-1) X 1 ~}} X 4 in ~ formula (Le-3), _{Y 1} and It has the same meaning as Y ₂ , and the preferred embodiment is also the same.
_{Ra 1} to Ra ₄ in the formula (Le-7) or the formula (Le-9) are each independently preferably an alkyl group or an alkoxy group from the viewpoint of enhancing the visibility of the exposed portion, and are alkoxy groups. It is more preferable, and it is particularly preferable that it is a methoxy group.
_{Rb 1} to Rb ₄ in the formulas (Le-7) to (Le-9) are independently substituted with a hydrogen atom, an alkyl group, or an alkyl group or an alkoxy group from the viewpoint of enhancing the visibility of the exposed portion. It is preferably an aryl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom or a methyl group.
_{Rc 1} and Rc ₂ in the formula (Le-8) are preferably phenyl groups or alkylphenyl groups, and more preferably phenyl groups, independently from the viewpoint of enhancing the visibility of the exposed portion. ..
Further, in the formula (Le-8), from the viewpoint of enhancing the visibility of the exposed portion, it is preferable that _{X 1} to X ₄ are hydrogen atoms and Y ₁ and Y _{2 are C.}
Further, in the formula (Le-8), from the viewpoint of enhancing the visibility of the exposed portion, Rb ₁ and Rb ₂ are independently substituted with a hydrogen atom, an alkyl group, or an alkyl group or an alkoxy group. It is preferably present, and more preferably a hydrogen atom or an alkyl group.

_{Further, the Rb 1} , Rb ₂ , Rc ₁ , and Rc ₂ in the formula (Le-8) preferably have the following aspects.
_{From the viewpoint of color development and visibility of the exposed portion, Rb 1} and Rb ₂ in the formula (Le-8) are preferably aryl groups or heteroaryl groups, respectively, and are preferably aryl groups. It is more preferably an aryl group having an electron donating group, and particularly preferably a phenyl group having an electron donating group at the para position.
_{Rc 1} and Rc ₂ in the formula (Le-8) are an aryl group having a substituent at at least one ortho position, or at least one, independently from the viewpoint of color development and visibility of the exposed portion. It is preferably a heteroaryl group having a substituent at the ortho position, more preferably an aryl group having a substituent at at least one ortho position, and a phenyl group having a substituent at at least one ortho position. Is more preferable, and it is particularly preferable that the phenyl group has a substituent at at least one ortho position and an electron donating group at the para position. Examples _{of the substituents in Rc 1} and Rc ₂ include substituents described later.
_{In addition, Rc 1} and Rb ₁ and Rc ₂ and Rb ₁ in the formula (Le-8) may be independently bonded at the ortho position to form a ring (for example, a carbazole ring).
The electron-donating groups in Rb ₁ , Rb ₂ , Rc ₁ , and Rc ₂ include amino groups, alkylamino groups, arylamino groups, and heteroaryls from the viewpoint of color development and visibility of exposed parts. Amino group, dialkylamino group, monoalkyl monoarylamino group, monoalkyl monoheteroarylamino group, diarylamino group, diheteroarylamino group, monoarylmonoheteroarylamino group, alkoxy group, allyloxy group, heteroallyloxy group , Or an alkyl group, more preferably an alkoxy group, an allyloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

The color-developing agent (preferably an acid-color-developing agent) is a leuco dye having the above-mentioned phthalide structure or fluorane structure from the viewpoint of color-developing property and visibility of the exposed portion, and is represented by the following formula (Le-10). It is preferably a compound to be used.

_{Ar 1} in the formula (Le-10) is similar to the preferred embodiment _{of Rb 1} and Rb ₂ in the formula (Le-8).
_{Ar 2} in the formula (Le-10) is similar to the preferred embodiment _{of Rc 1} and Rc ₂ in the formula (Le-8).

The alkyl group in the formulas (Le-1) to (Le-9) may be linear, may have a branch, or may have a ring structure.
Further, the number of carbon atoms of the alkyl group in the formulas (Le-1) to (Le-9) is preferably 1 to 20, more preferably 1 to 8, and further preferably 1 to 4. It is preferably 1 or 2, and particularly preferably 1.
The number of carbon atoms of the aryl group in the formulas (Le-1) to (Le-10) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8.
Specific examples of the aryl group in the formulas (Le-1) to (Le-10) include a phenyl group, a naphthyl group, an anthrasenyl group, a phenanthrenyl group and the like which may have a substituent.
Specifically, the heteroaryl group in the formulas (Le-1) to (Le-10) may have a substituent, such as a frill group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group. Can be mentioned.
Further, each group such as a monovalent organic group, an alkyl group, an aryl group, a heteroaryl group, a dialkylanilino group, an alkylamino group and an alkoxy group in the formulas (Le-1) to (Le-9) is substituted. It may have a group.

The substituents in the formulas (Le-1) to (Le-10) include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group and a dialkyl group. Amino group, monoalkyl monoarylamino group, monoalkyl monoheteroarylamino group, diarylamino group, diheteroarylamino group, monoaryl monoheteroarylamino group, hydroxy group, alkoxy group, allyloxy group, heteroallyloxy group, Examples thereof include an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group and a cyano group. Further, these substituents may be further substituted with these substituents.

Specific examples of the leuco dye having a phthalide structure or a fluorine structure that are preferably used include the following compounds (S-1 to S-21).

It is also possible to use a commercially available product as the acid color former. Commercially available acid color formers include, for example, ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H-3035, BLUE203, ATP, H. -1046, H-2114 (above, manufactured by Fukui Yamada Chemical Industry Co., Ltd.), ORANGE-DCF, Vermilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF, TH-107 (above, 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 (above, manufactured by Yamamoto Kasei Co., Ltd.), crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.) and the like.
Among these commercially available 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 preferable because the film (that is, the image recording layer) on which the crystal violet lactone is formed has a good visible light absorption rate.

As the leuco dye, the following compounds are also preferably used from the viewpoint of enhancing the visibility of the exposed portion.

The color former may be used alone or in combination of two or more.

The content of the color former is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 5% by mass, based on the total mass of the image recording layer.

The image recording layer may contain components other than those described above.
Ingredients other than those described above include colorants, baking agents, polymerization inhibitors, higher fatty acid derivatives, plasticizers, inorganic fine particles, and low molecular weight hydrophilicity described in paragraphs 0181 to 0190 of JP-A-2009-255434. Examples include compounds.
In addition, as components other than those described above, the hydrophobizing precursor (fine particles capable of converting the image recording layer into hydrophobicity when heat is applied) described in paragraphs 0191 to 0217 of JP2012-187907A. Examples thereof include low molecular weight hydrophilic compounds, fat sensitizers (for example, phosphonium compounds, nitrogen-containing low molecular weight compounds, ammonium group-containing polymers), chain transfer agents and the like.

[Formation of image recording layer]
In the image recording layer in the lithographic printing plate original plate 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. It can be formed by preparing a coating liquid, applying the coating liquid on a support by a known method such as bar coater coating, and drying the coating liquid.

As the solvent used for the coating liquid, a known solvent can be used. 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 monomateyl 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 Examples thereof include formamide, dimethylsulfoxide, γ-butyrolactone, methyl lactate, ethyl lactate and the like.
The solvent may be used alone or in combination of two or more.
The solid content concentration in the coating liquid is preferably 1% by mass 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 characteristics of the image recording layer, 0.3 g / m ² to 3.0 g /. m ² is preferable.
Further, the film thickness of the image recording layer in the lithographic printing plate original plate according to the present disclosure is preferably 0.1 μm to 3.0 μm, and more preferably 0.3 μm to 2.0 μm.

<Support>
The lithographic printing plate original plate according to the present disclosure has a support.
As the support, a known lithographic printing plate precursor support can be appropriately selected and used.
As the support, a support having a hydrophilic surface (hereinafter, also referred to as “hydrophilic support”) is preferable.

As the support in the present disclosure, an aluminum plate that has been roughened and anodized by a known method is preferable. That is, the support in the present disclosure preferably has an aluminum plate and an aluminum anodized film arranged on the aluminum plate.

[Preferable embodiment of support]
An example of a preferred embodiment of the support used in the present disclosure (the aluminum support according to this example is also referred to as “support (1)”) is shown below.
That is, the support (1) has an aluminum plate and an anodized film of aluminum arranged on the aluminum plate, and the anodized film is located 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.
The value of the brightness L ^* ^{in the L *} a ^* b ^* color system of the surface of the anodic oxide film on the image recording layer side is preferably 70 to 100.

FIG. 1 is a schematic cross-sectional view of an embodiment of the aluminum support 12a.
The aluminum support 12a has a laminated structure in which an aluminum plate 18 and an anodized aluminum film 20a (hereinafter, also simply referred to as “anodized film 20a”) are laminated in this order. The anodic oxide film 20a in the aluminum support 12a is located closer to the image recording layer than the aluminum plate 18. That is, it is preferable that the lithographic printing plate original plate according to the present disclosure has at least an anodic oxide film, an image recording layer, and an outermost layer on an aluminum plate in this order.

-Anodic oxide film-
Hereinafter, preferred embodiments of the anodic oxide film 20a will be described.
The anodic oxide film 20a is a film formed on the surface of the aluminum plate 18 by anodization treatment, and this film is substantially perpendicular to the surface of the film and has ultrafine micropores 22a in which each is uniformly distributed. Has. The micropore 22a extends from the surface of the anodic oxide film 20a on the image recording layer side (the surface of the anodic oxide film 20a on the side opposite to the aluminum plate 18 side) along the thickness direction (aluminum plate 18 side).

The average diameter (average opening diameter) of the micropores 22a in the anodic oxide film 20a on the surface of the anodic oxide film is preferably more than 10 nm and 100 nm or less. Among them, from the viewpoint of the balance between printing resistance, stain resistance, and image visibility, 15 nm to 60 nm is more preferable, 20 nm to 50 nm is further preferable, and 25 to 40 nm is particularly preferable. The diameter inside the pores may be wider or narrower than the surface layer.
When the average diameter exceeds 10 nm, the printing durability and the image visibility are further excellent. Further, when the average diameter is 100 nm or less, the printing durability is further excellent.
The average diameter of the micropores 22a is 400 nm × 600 nm in the obtained 4 images obtained by observing 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 the micropores existing in the range of is measured at 50 points and calculated as an arithmetic average value.
If the shape of the micropore 22a is not circular, the diameter equivalent to the circle is used. The "circle equivalent 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 micropore 22a is not particularly limited, but is preferably 10 nm to 3,000 nm, more preferably 50 nm to 2,000 nm, and even more preferably 300 nm to 1,600 nm.
The depth is an average value obtained by taking a photograph (150,000 times) of a cross section of the anodic oxide film 20a and measuring the depths of 25 or more micropores 22a.

The shape of the micropore 22a is not particularly limited, and in FIG. 2, it is a substantially straight tubular (substantially cylindrical) shape, but it may be a conical shape whose diameter decreases in the depth direction (thickness direction). Further, the shape of the bottom portion of the micropore 22a is not particularly limited, and may be curved (convex) or planar.

^{The value of L *} a ^* b ^* ^{lightness L *} in the color system of the surface of the aluminum support 12a on the image recording layer side (the surface of the anodic oxide 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 that the balance between printing durability and image visibility is more excellent.
The brightness L ^* is measured using a color difference meter SpecroEye manufactured by X-Rite Co., Ltd.

In the support (1), the micropore communicates with the large-diameter hole extending from the surface of the anodic oxide film to a depth of 10 nm to 1,000 nm and the bottom of the large-diameter hole, and is deep from the communication position. It is composed of a small-diameter hole extending from 20 nm to 2,000 nm, and the average diameter of the large-diameter hole on the surface of the anodic oxide film is 15 nm to 100 nm, and the average diameter of the small-diameter hole at the communication position. A mode in which the diameter is 13 nm or less (hereinafter, the support according to this mode is also referred to as “support (2)”) is also preferably mentioned.
FIG. 2 is a schematic cross-sectional view of the aluminum support 12a according to an embodiment different from that shown in FIG.
In FIG. 2, the aluminum support 12b includes an aluminum plate 18 and an anodic oxide film 20b having a micropore 22b composed of a large-diameter hole portion 24 and a small-diameter hole portion 26.
The micropores 22b in the anodic oxide film 20b have a large-diameter hole portion 24 extending from the surface of the anodic oxide film to a depth of 10 nm to 1,000 nm (depth D: see FIG. 2) and a bottom portion of the large-diameter hole portion 24. It is composed of a small-diameter hole portion 26 extending from the communication position to a depth of 20 nm to 2,000 nm.
The details of the large-diameter hole portion 24 and the small-diameter hole portion 26 are as described in paragraphs 0107 to 0114 of Japanese Patent Application Laid-Open No. 2019-162855, and this aspect is also applied in the present disclosure.

[Manufacturing method of aluminum support]
As the method for manufacturing the aluminum support in the present disclosure, for example, a manufacturing method in which the following steps are sequentially performed is preferable.
・ Roughening treatment step: Roughening treatment of aluminum plate ・ Anodizing treatment step: Anodizing the roughened aluminum plate ・ Pore wide treatment step: Anodizing obtained in the anodic oxidation treatment step Step of bringing an aluminum plate having an oxide film into contact with an acid aqueous solution or an alkaline aqueous solution to increase the diameter of micropores in the anodized film The procedure of each step will be described in detail below.

(Roughening process)
The roughening treatment step is a step of applying a roughening treatment including an electrochemical roughening treatment to the surface of the aluminum plate. This step is preferably carried out before the anodizing treatment step described later, but it may not be carried out in particular as long as the surface of the aluminum plate already has a preferable surface shape.
The roughening treatment for the aluminum plate can be performed by the method described in paragraphs 0086 to 0101 of JP-A-2019-162855.

(Anodizing process)
The procedure of the anodic oxidation treatment step is not particularly limited as long as the above-mentioned micropores can be obtained, and a known method can be mentioned.
In the anodizing treatment step, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid or the like can be used as the electrolytic bath. For example, the concentration of sulfuric acid may be 100 g / L to 300 g / L.
The conditions for the anodizing treatment are appropriately set depending on the electrolytic solution used, and for example, the liquid temperature is 5 ° C to 70 ° C (preferably 10 ° C to 60 ° C), and the current density is 0.5 A / dm ² to 60 A / dm ^2. (Preferably 5A / dm ² to 60A / dm ² ), voltage 1V to 100V (preferably 5V to 50V), electrolysis time 1 to 100 seconds (preferably 5 to 60 seconds), and film amount 0.1 g. / M ² to 5 g / m ² (preferably 0.2 g / m ² to 3 g / m ² ).

(Pore wide processing)
The pore wide treatment is a treatment (pore diameter expansion treatment) for enlarging the diameter (pore diameter) of the micropores existing in the anodic oxide film formed by the above-mentioned anodizing treatment step.
The pore-wide treatment can be performed by contacting the aluminum plate obtained by the above-mentioned anodizing treatment step with an acid aqueous solution or an alkaline aqueous solution. The contact method is not particularly limited, and examples thereof include a dipping method and a spraying method.

<Undercoat layer>
The lithographic printing plate original plate according to the present disclosure preferably has an undercoat layer (sometimes referred to as 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 area, and makes it easy for the image recording layer to peel off from the support in the unexposed area, so that the deterioration of printing durability is suppressed. Contributes to improving developability. Further, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, which also has an effect of preventing the heat generated by the exposure from diffusing to the support and reducing the sensitivity.

〔polymer〕
Examples of the compound used for the undercoat layer include polymers having an adsorptive group and a hydrophilic group that can be adsorbed on the surface of the support. In order to improve the adhesion to the image recording layer, a polymer having an adsorptive group and a hydrophilic group and further having a crosslinkable group is preferable. The compound used for the undercoat layer may be a small molecule compound or a polymer. As the compound used for the undercoat layer, two or more kinds may be mixed and used as needed.

When the compound used for the undercoat layer is a polymer, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group and a monomer having a crosslinkable group is preferable.
Adsorbable groups that can be adsorbed on the surface of the support include phenolic hydroxy group, carboxy group, -PO ₃ H ₂ , -OPO ₃ H ₂ , -CONHSO _2- , -SO ₂ NHSO _2- , _{-COCH 2} COCH ₃ Is preferable. As the hydrophilic group, a sulfo group or a salt thereof, or a salt of a carboxy group is preferable. As the crosslinkable group, an acrylic 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 substituent having a countercharge with the polar substituent and a compound having an ethylenically unsaturated bond. A monomer other than the above, preferably a hydrophilic monomer may be further copolymerized.

Specifically, a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A No. 10-282679, and an ethylenic substance described in JP-A-2-304441. A phosphorus compound having a double bond reactive group is preferably mentioned. Crosslinkable groups (preferably ethylenically unsaturated bonding groups) and supports described in JP-A-2005-238816, JP-A-2005-125479, JP-A-2006-239867, and JP-A-2006-215263. Low molecular weight or high molecular weight compounds having functional and hydrophilic groups that interact with the surface are also preferably used.
More preferable examples thereof include polymer polymers having an adsorptive group, a hydrophilic group and a crosslinkable group that can be adsorbed on the surface of the support described in JP-A-2005-125479 and JP-A-2006-188038.

The content of the ethylenically unsaturated bond group 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 the 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]
The undercoat layer preferably contains a hydrophilic compound from the viewpoint of developability.
The hydrophilic compound is not particularly limited, and a known hydrophilic compound used for the undercoat layer can be used.
Preferred examples of the hydrophilic compound include phosphonic acids having an amino group such as carboxymethyl cellulose and dextrin, organic phosphonic acids, organic phosphoric acids, organic phosphinic acids, amino acids, and hydrochlorides of amines having a hydroxy group.
Further, as the hydrophilic compound, a compound having an amino group or a functional group having a polymerization prohibition ability and a group interacting with the surface of the support (for example, 1,4-diazabicyclo [2.2.2] octane (DABCO)). , 2,3,5,6-tetrahydroxy-p-quinone, chloranyl, sulfophthalic acid, ethylenediaminetetraacetic acid (EDTA) or its salt, hydroxyethylethylenediaminetriacetic acid or its salt, dihydroxyethylethylenediaminediacetic acid or its salt, hydroxy Ethylenediaminediacetic acid or a salt thereof, etc.) are preferably mentioned.

The hydrophilic compound preferably contains a hydroxycarboxylic acid or a salt thereof from the viewpoint of suppressing scratches and stains.
Further, the hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, is preferably contained in the layer on the aluminum support from the viewpoint of suppressing scratches and stains. Further, 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, an undercoat layer or an image recording layer is preferably mentioned as a layer in contact with the aluminum support. Further, a layer other than the layer in contact with the aluminum support, for example, the outermost layer or the image recording layer may contain a hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof.
In the lithographic printing plate original plate according to the present disclosure, it is preferable that the image recording layer contains a hydroxycarboxylic acid or a salt thereof from the viewpoint of suppressing scratches and stains.
Further, in the lithographic printing plate original plate 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 containing at least hydroxycarboxylic acid or a salt thereof (for example, an aqueous solution) is also preferably mentioned. Be done. In the above embodiment, the treated hydroxycarboxylic acid or a salt thereof is detected at least in a state of being contained in a layer on the image recording layer side (for example, an image recording layer or an undercoat layer) in contact with an aluminum support. be able to.
By containing hydroxycarboxylic acid or a salt thereof in the layer on the image recording layer side in contact with the aluminum support such as the undercoat layer, the surface of the aluminum support on the image recording layer side can be made hydrophilic, and the aluminum support can also be made hydrophilic. The contact angle with water on the surface of the image recording layer side by the aerial water droplet method can be easily set to 110 ° or less, and the scratch and stain suppression property is excellent.

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, or alcoholic acid (). Iwanami Physics and Chemistry Dictionary 5th Edition, published by Iwanami Shoten Co., Ltd. (1998)).
The hydroxycarboxylic acid or a salt thereof is preferably represented by the following formula (HC).
Formula (HC): R ^HC (OH) _mhc ( _COM ^HC ) nhc
In formula (HC), R ^HC represents a mhc + nhc valent organic group, M ^HC independently represents a hydrogen atom, an alkali metal, or onium, and mhc and nhc each independently represent an integer of 1 or more. Represented, when n is 2 or more, M may be the same or different.

In the formula ^(HC), as the organic group for mhc + NHC value represented by ^{R HC,} it includes mhc + NHC valent hydrocarbon group. The hydrocarbon group may have a substituent and / or a linking group.
Examples of the hydrocarbon group include a group having a mhc + nhc valence derived from an aliphatic hydrocarbon, for example, an alkylene group, an alkanthryl group, an alkanetetrayl group, an alcantyl group, an alkenylene group, an alkanthryl group and an alkentetrayl group. Groups of mhc + nhc valence derived from aromatic hydrocarbons such as groups, alkenylpentyl groups, alkynylene groups, alkyntriyl groups, alkynetetrayl groups, alkynpentyl groups, etc., such as allylene groups, allenetriyl groups, allenes. Examples thereof include a tetrayl group and an arenepentile group. Examples of the substituent include an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an aryl group and the like. Specific examples of the substituent include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group and a 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, trill 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. 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 thereof include an alkylene group, a substituted alkylene group, an arylene group, a substituted arylene group and the like, and a plurality of these divalent groups are linked by any of an amide bond, an ether bond, a urethane bond, a urea bond and an ester bond. It may have a structure that has been modified.

^Examples of the alkali metal represented by MHC include lithium, sodium, potassium and the like, and sodium is particularly preferable. Examples of onium include ammonium, phosphonium, sulfonium and the like, and ammonium is particularly preferable.
Further, M ^HC, from the viewpoint of scratch stain inhibitory, preferably an alkali metal or an onium, and more preferably an alkali metal.
The total number of mhc and nhc is preferably 3 or more, more preferably 3 to 8, and even more preferably 4 to 6.

The hydroxycarboxylic acid or a salt thereof preferably has a molecular weight of 600 or less, more preferably 500 or less, and particularly preferably 300 or less. The molecular weight is preferably 76 or more.
Specifically, the hydroxycarboxylic acid constituting the hydroxycarboxylic acid or the salt of the hydroxycarboxylic acid is gluconic acid, glycolic acid, lactic acid, tartron acid, hydroxybutyric acid (2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-Hydroxybutyric acid, etc.), malic acid, tartaric acid, citramalic acid, citric acid, isocitrate, leucic acid, mevalonic acid, pantoic acid, lysynolic acid, lysine lysic acid, cerebronic acid, quinic acid, chymic acid, monohydroxybenzoic acid derivative (Salicylic acid, cleosortic acid (homosalicylic acid, hydroxy (methyl) benzoic acid), vanillic acid, syring acid, etc.), dihydroxybenzoic acid derivatives (pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentidic acid, orceric acid, etc.), trihydroxy Benzoic acid derivatives (such as galvanic acid), phenylacetic acid derivatives (mandelic acid, benzylic acid, atrolactinic acid, etc.), hydrosilicic acid derivatives (merilotoic acid, floret acid, bear acid, umbel acid, coffee acid, ferulic acid, cinnapic acid, etc.) Celebronic acid, carmic acid, etc.) and the like.

Among these, as the hydroxycarboxylic acid or the hydroxycarboxylic acid constituting the salt of the hydroxycarboxylic acid, a compound having two or more hydroxy groups is preferable from the viewpoint of suppressing scratches and stains, and the hydroxy group is preferable. A compound having 3 or more hydroxy groups is more preferable, a compound having 5 or more hydroxy groups is further preferable, and a compound having 5 to 8 hydroxy groups is particularly preferable.
Further, as a substance having one carboxy group and two or more hydroxy groups, gluconic acid or shikimic acid is preferable.
Citric acid or malic acid is preferable as having two or more carboxy groups and one hydroxy group.
Tartaric acid is preferable as having two or more carboxy groups and hydroxy groups, respectively.
Among them, gluconic acid is particularly preferable as the hydroxycarboxylic acid.

The hydrophilic compound may be used alone or in combination of two or more.

When the undercoat layer contains a hydrophilic compound (preferably hydroxycarboxylic acid or a salt thereof), the content of the hydrophilic compound (preferably hydroxycarboxylic acid and a salt thereof) is 0.01 mass by mass with respect to the total mass of the undercoat layer. It is preferably% to 50% by mass, more preferably 0.1% by mass to 40% by mass, and particularly preferably 1.0% by mass to 30% by mass.

In addition to the above-mentioned compound for the undercoat layer, the undercoat layer is a chelating agent to prevent stains over time.
It may contain a secondary or tertiary amine, a polymerization inhibitor and the like.

The undercoat layer can be formed by dissolving each of the above-mentioned necessary components in a known solvent to prepare a coating liquid, applying the coating liquid on the support by a known method, and drying.
The coating amount (solid content) of the undercoat layer ^{is preferably 0.1 mg / m 2} to 300 mg / m ^2, more preferably 5 mg / m ² to 200 mg / m ² .

The lithographic printing plate original plate according to the present disclosure may have other layers other than those described above.
The other layer is not particularly limited and may have a known layer. For example, a back coat layer may be provided on the side of the support opposite to the image recording layer side, if necessary.

≪Manufacturing method of lithographic printing plate original plate≫
The lithographic printing plate original plate according to the present disclosure is a manufacturing method including a step of forming an image recording layer on a support by the method described above and forming an outermost layer on the formed image recording layer by the following method. Is preferably manufactured.
The step of forming the outermost layer is the above-mentioned method of forming the outermost layer, that is, a coating liquid having a solid content concentration of 5% by mass to 30% by mass is applied onto the image recording layer formed on the support. This is a step of drying the obtained coating film at 70 ° C. to 200 ° C. under drying conditions of 5 seconds to 30 seconds to form the outermost layer.
Since the details of the step of forming the outermost layer are described in the column of the method of forming the outermost layer, they will be omitted here.
According to this method for manufacturing a lithographic printing plate original plate, it becomes easy to obtain a lithographic printing plate original plate in which the decomposition rate of the infrared absorber due to ozone exposure is 50% or less.

≪Manufacturing method of lithographic printing plate and lithographic printing method≫
A lithographic printing plate can be produced by exposing the original plate of the lithographic printing plate according to the present disclosure to an image and performing a developing process.
The method for producing a lithographic printing plate according to the present disclosure includes a step of exposing the lithographic printing plate original plate according to the present disclosure to an image (hereinafter, also referred to as an “exposure step”), and printing ink and wetting on a printing machine. It is preferable to include a step of supplying at least one selected from the group consisting of water to remove the image recording layer of the non-image portion (hereinafter, also referred to as “on-machine development step”).
The lithographic printing method according to the present disclosure is a step of exposing a lithographic printing plate original plate according to the present disclosure to an image (exposure step) and printing by supplying at least one selected from the group consisting of printing ink and dampening water. A process of producing a lithographic printing plate by removing the image recording layer of the non-image portion on the machine (machine development process), and a process of printing with the obtained lithographic printing plate (hereinafter, also referred to as "printing process"). It is preferable to include.

Hereinafter, preferred embodiments of each step will be sequentially described with respect to the method for producing a lithographic printing plate according to the present disclosure and the lithographic printing method according to the present disclosure. The lithographic printing plate original plate according to the present disclosure can also be developed with a developing solution.
Hereinafter, the exposure step and the on-machine development step in the lithographic printing plate manufacturing method will be described, but the exposure step in the lithographic printing plate manufacturing method according to the present disclosure and the exposure step in the lithographic printing method according to the present disclosure are the same. It is a step, and the on-machine development step in the method for producing a lithographic printing plate according to the present disclosure is the same as the on-machine development step in the lithographic printing method according to the present disclosure.

<Exposure process>
The method for producing a lithographic printing plate according to the present disclosure preferably includes an exposure step of exposing the lithographic printing plate original plate according to the present disclosure to an image to form an exposed portion and an unexposed portion. It is preferable that the lithographic printing plate original plate according to the present disclosure is exposed to an image by laser exposure through a transparent original image having a line image, a halftone dot image, or the like, or by laser light scanning with digital data.
The wavelength of the light source is preferably 750 nm to 1,400 nm. As a light source having a wavelength of 750 nm to 1,400 nm, a solid-state laser or a semiconductor laser that emits infrared rays is suitable. Regarding the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably 20 microseconds or less, and the irradiation energy amount is 10 mJ / cm ² to 300 mJ / cm ^2. preferable. Further, it is preferable to use a multi-beam laser device in order to shorten the exposure time. The exposure mechanism may be any of an inner drum method, an outer drum method, a flatbed method and the like.
Image exposure can be performed by a conventional method using a platesetter or the like. In the case of on-machine development, the lithographic printing plate original plate may be mounted on the printing machine and then the image may be exposed on the printing machine.

<In-machine development process>
The method for producing a lithographic printing plate according to the present disclosure is an on-machine development step of supplying at least one selected from the group consisting of printing ink and dampening water on a printing machine to remove an image recording layer in a non-image area. It is preferable to include it.
The on-machine development method will be described below.

[In-machine development method]
In the on-machine development method, the image-exposed lithographic printing plate original plate supplies oil-based ink and water-based components on the printing machine, and the image recording layer in the non-image area is removed to produce a lithographic printing plate. Is preferable.
That is, either the flat plate printing plate original plate is mounted on the printing machine as it is without any development processing after the image exposure, or the flat plate printing plate original plate is mounted on the printing machine and then the image is exposed on the printing machine, and then When printing is performed by supplying an oil-based ink and a water-based component, in the non-image area, an uncured image recording layer is formed by one or both of the supplied oil-based ink and the water-based component in the initial stage of printing. It dissolves or disperses and is removed, exposing a hydrophilic surface to that portion. On the other hand, in the exposed portion, the image recording layer cured by exposure forms an oil-based ink receiving portion having a lipophilic surface. The first supply to the plate surface may be an oil-based ink or a water-based component, but the oil-based ink is first supplied in terms of preventing contamination by the components of the image recording layer from which the water-based components have been removed. Is preferable. In this way, the lithographic printing plate original plate is developed on the printing machine and used as it is for printing a large number of sheets. As the oil-based ink and the water-based component, ordinary printing ink for lithographic printing and dampening water are preferably used.

The wavelength of the light source is preferably 300 nm to 450 nm or 750 nm to 1,400 nm as the laser for image-exposing the lithographic printing plate original plate according to the present disclosure. In the case of a light source of 300 nm to 450 nm, a lithographic printing plate original plate containing a sensitizing dye having an absorption maximum in this wavelength region in the image recording layer is preferably used, and a light source of 750 nm to 1,400 nm is preferably used as described above. Be done. As a light source of 300 nm to 450 nm, a semiconductor laser is suitable.

<Printing process>
The 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 a printing ink, an oil-based ink or an ultraviolet curable ink (UV ink) is preferably mentioned.
Further, in the printing process, dampening water may be supplied as needed.
Further, the printing process may be continuously performed in the on-machine development process without stopping the printing machine.
The recording medium is not particularly limited, and a known recording medium can be used if desired.

In the method for producing a lithographic printing plate from the lithographic printing plate original plate according to the present disclosure and the lithographic printing method according to the present disclosure, lithographic printing is performed before, during, and between exposure and development as necessary. The entire surface of the plate may be heated. By such heating, the image formation reaction in the image recording layer is promoted, and advantages such as improvement of sensitivity and printing durability and stabilization of sensitivity may occur. The heating before development is preferably performed under mild conditions of 150 ° C. or lower. With the above aspect, it is possible to prevent problems such as hardening of the non-image portion. It is preferable to use very strong conditions for heating after development, and it is preferably in the range of 100 ° C to 500 ° C. Within the above range, a sufficient image enhancement effect can be obtained, and problems such as deterioration of the support and thermal decomposition of the image portion can be suppressed.

Hereinafter, the present disclosure will be described in detail by way of examples, but the present disclosure is not limited thereto. In this embodiment, "%" and "part" mean "% by mass" and "part by mass", respectively, unless otherwise specified. In the polymer compound, the molecular weight is the weight average molecular weight (Mw), and the ratio of the constituent repeating units is the molar percentage, except for those specified specifically. The weight average molecular weight (Mw) is a value measured as a polystyrene-equivalent value by a gel permeation chromatography (GPC) method.

<Preparation of support>
(Preparation of support (1))
The aluminum alloy plate of material 1S having a thickness of 0.3 mm is described in paragraph 0134 from (A) mechanical roughening treatment (brush grain method) described in paragraph 0126 of JP2012-158022A. (AI) Desmat treatment in an acidic aqueous solution was carried out.
Next, each treatment condition from the (Aj) first stage anodizing treatment described in paragraph 0135 of JP2012-158022A to the (Am) third stage anodizing treatment described in paragraph 0138. Was appropriately adjusted to form an anodized film, which was used as the support (1).
A water washing treatment was performed during all the treatment steps, and after the water washing treatment, liquid was drained with a nip roller.

The details of the obtained support (1) are summarized.
^{Support (1): L *} a ^* b ^* lightness L ^* value on the surface of the anodized film of the micropores: 83, average diameter on the surface of the oxide film of the large diameter pores in the micropores: 35 nm (depth) 100 nm), average diameter at the communication position of the small diameter hole in the micropore: 10 nm (depth 1,000 nm), ratio of the depth of the large diameter hole to the average diameter of the large diameter hole: 2.9

(Preparation of support (2))
(A) Alkaline etching treatment An aqueous caustic soda solution having a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass was sprayed onto an aluminum plate at a temperature of 70 ° C. to perform an etching treatment. Then, it was washed with water by spraying. The amount of aluminum dissolved on the surface to be subjected to the electrochemical roughening treatment later was 5 g / m ² .

(B) Desmat treatment using an acidic aqueous solution (first desmat treatment)
Next, a desmat treatment was performed using an acidic aqueous solution. As the acidic aqueous solution used for the desmat treatment, an aqueous solution of sulfuric acid 150 g / L was used. The liquid temperature was 30 ° C. An acidic aqueous solution was sprayed onto an aluminum plate to perform desmat treatment for 3 seconds. Then, it was washed with water.

(C) Electrochemical roughening treatment Next, an electrolytic solution having a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L is used, and electrochemical roughening is performed using an AC current. Processing was performed. The liquid temperature of the electrolytic solution was 30 ° C. The aluminum ion concentration was adjusted by adding aluminum chloride.
The AC current waveform is a sinusoidal wave with symmetrical positive and negative waveforms, the frequency is 50 Hz, the anode reaction time and cathode reaction time in one AC current cycle are 1: 1, and the current density is the peak current value of the AC current waveform. It was 75 A / dm ^2. The electric amount was 450C / dm ² in terms of the total electric quantity aluminum plate participating in the anode reaction, electrolytic treatment was carried out four times to open the energization interval 112.5C / dm ² by 4 seconds. A carbon electrode was used as the counter electrode of the aluminum plate. Then, it was washed with water.

(D) Desmat treatment using an acidic aqueous solution
Next, a desmat treatment was performed using an acidic aqueous solution. Specifically, an acidic aqueous solution was sprayed onto an aluminum plate to perform desmat treatment for 3 seconds. As the acidic aqueous solution used for the desmat treatment, an aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L was used. The liquid temperature was 30 ° C.

(E) Anodizing treatment Anodizing treatment was performed in a sulfuric acid solution using an anodizing apparatus by direct current electrolysis so as to have ^{an oxide film amount of 3.6 g / m 2.}
As described above, the support (2) was manufactured.

(Preparation of support (3))
A 0.28 mm thick Hydro 1052 aluminum alloy strip or web (available from Norsk Hydro ASA, Norway) was used as the aluminum-containing support.
Both pre-etch and post-etch steps were performed in alkaline solution under known conditions. Roughening (or sanding) is performed by electrochemical means in a hydrochloric acid solution at about 23 ° C. on the plane of the aluminum-containing support to obtain a calculated average roughness (Ra) of 0.5 μm. bottom. These processing steps were performed in a continuous process on a typical production line used for the production of lithographic printing plates and original plates.
The resulting sanding and etched aluminum-containing supports were then washed with water, dried and cut into individual sanding and etched aluminum-containing sheets.
Next, each individual sheet was anodized twice, and each anodizing bath contained about 100 liters of anodizing solution. The first anodic oxidation condition is an electrolyte concentration of 175 g / liter, a temperature of 60 ° C., and a current density of 5.8 A / dm ² for 21.3 seconds. The second anodic oxidation condition is an electrolyte concentration of 280 g / liter, a temperature of 23 ° C. The treatment was performed at a current density of 10 A / dm ^{2 for 18 seconds.} The first anodizing process for forming the outer aluminum oxide layer is carried out using phosphoric acid as the electrolyte and the second anodizing process for forming the inner aluminum oxide layer is sulfuric acid as the electrolyte. Used and run.
As described above, the support (3) was manufactured.

(Preparation of support (4))
In order to remove the rolling oil on the surface of an aluminum plate (material: JIS A 1050) with a thickness of 0.3 mm, it was degreased at 50 ° C. for 30 seconds using a 10 mass% sodium aluminate aqueous solution, and then the hair diameter was 0. The aluminum surface was ground with three 3 mm bundled nylon brushes and a Pamis-aqueous suspension (specific gravity 1.1 g / cm ³ ) with a median diameter of 25 μm, and washed thoroughly with water. This plate was immersed in a 25 mass% sodium hydroxide aqueous solution at 45 ° C. for 9 seconds for etching, washed with water, and then further immersed in a 20 mass% nitric acid aqueous solution at 60 ° C. for 20 seconds and washed with water. At this time, the etching amount on the sand trimming surface was about 3 g / m ² .
Next, an electrochemical roughening treatment was continuously performed using an AC voltage of 60 Hz. The electrolytic solution at this time was a 1% by mass aqueous solution of nitric acid (containing 0.5% by mass of aluminum ions) and a liquid temperature of 50 ° C. The AC power supply waveform is electrochemically roughened using a carbon electrode as a counter electrode using a trapezoidal square wave AC with a TP of 0.8 msec, a duty ratio of 1: 1 and a trapezoidal square wave AC for the time from zero to the peak of the current value. Was done. Ferrite was used as the auxiliary anode. The current density was 30 A / dm ² at the peak value of the current, and 5% of the current flowing from the power source was diverted to the auxiliary anode. The amount of electricity in nitric acid electrolysis was ^{175 C / dm 2 when the aluminum plate was an anode.} Then, it was washed with water by spraying.
Subsequently, it is electrolyzed with nitrate in a 0.5% by mass aqueous solution of hydrochloric acid (containing 0.5% by mass of aluminum ions) and an electrolytic solution having a liquid temperature of 50 ° C. under ^{the condition that the aluminum plate has an electric amount of 50 C / dm 2 at the anode.} The surface was subjected to an electrochemical roughening treatment in the same manner as in the above method, and then washed with water by spraying.
Next, a DC anodic oxide film having a ^{current density of 15 A / dm 2} and a DC anodic oxide film of 2.5 g / m ² was provided on this plate using 15 mass% sulfuric acid (containing 0.5 mass% of aluminum ions) as an electrolytic solution, and then washed with water. It was dried to obtain a support A.
Then, in order to ensure the hydrophilicity of the non-imaged portion, the support A was silicate-treated at 60 ° C. for 10 seconds using a 2.5 mass% No. 3 sodium silicate aqueous solution, and then washed with water to support the support ( 4) was obtained. The amount of Si adhered was 10 mg / m ² . The center line average roughness (Ra) of the support (4) was measured using a needle having a diameter of 2 μm and found to be 0.51 μm.

<Preparation of undercoat layer coating liquid>
(Preparation of undercoat layer coating liquid (1))
An undercoat layer coating liquid (1) having the following composition was prepared.
-Compound for undercoat layer (hereinafter (P-1), 11% aqueous solution): 0.10502 parts-Sodium gluconate: 0.07000 parts-Surfactant (Emarex (registered trademark) 710, Nippon Emulsion Co., Ltd.) : 0.00159 parts ・ Preservative (Biohope L, Keiai Kasei Co., Ltd.): 0.00149 parts ・ Water: 2.87190 parts

(Preparation of undercoat layer coating liquid (2))
An undercoat layer coating liquid (2) having the following composition was prepared.
-Compound for undercoat layer ((P-1) above, 11% aqueous solution): 0.10502 parts-Hydroxyethyldiiminodiacetic acid: 0.01470 parts-Sodium ethylenediaminetetraacetate: 0.06575 parts-Surfactant (Emma) Rex (registered trademark) 710, Nippon Emulsion Co., Ltd.): 0.00159 parts, preservative (Biohope L, Keiai Kasei Co., Ltd.): 0.00149 parts, water: 2.86144 parts

(Preparation of undercoat layer coating liquid (3))
An undercoat layer coating liquid (3) having the following composition was prepared.
-Compound for undercoat layer (hereinafter (P-2)): 0.18 parts-Hydroxyethyliminodiacetic acid: 0.10 parts-Methanol: 55.24 parts-Water: 6.15 parts

<Preparation of image recording layer coating liquid>
(Preparation of image recording layer coating liquid (1-1))
An image recording layer coating liquid (1-1) was prepared by mixing a mixed liquid containing components other than the following microgel liquid 1 and the following microgel liquid 1 immediately before coating and stirring the mixture.
-Infrared absorber IR-1 (following structure, HOMO: -5.35eV, LUMO: -3.75eV): 0.02000 parts-Color former S-1 (following structure): 0.02500 parts-Electronic accepting polymerization Initiator Int-1 (following structure, HOMO: -6.70 eV, LUMO: -3.08 eV): 0.11000 parts-electron donating type polymerization initiator TPB (following structure, HOMO: -5.90 eV): 0. 02,500 parts ・ Polymerizable compound M-1 (obtained by the following synthesis method): 0.27500 parts ・ Anionic surfactant A-1 (following structure): 0.00600 parts ・ Fluorine-based surfactant W- 1 (structure below): 0.00416 parts, 2-butanone: 4.3602 parts, 1-methoxy-2-propanol: 4.4852 parts, methanol: 2.2838 parts, microgel solution 1 (obtained by the following preparation method) What was done): 2.3256 copies

(Preparation of image recording layer coating liquid (1-2))
The image recording layer coating liquid (1-2) was prepared in the same manner as in the preparation of the image recording layer coating liquid (1-1), except that the color developing agent S-3 (the following structure) was used instead of the color developing agent S-1. Was prepared.

(Preparation of image recording layer coating liquid (1-3))
The image recording layer coating liquid (1-3) was prepared in the same manner as in the preparation of the image recording layer coating liquid (1-1) except that the color developing agent S-4 (the structure described below) was used instead of the color developing agent S-1. Was prepared.

(Preparation of image recording layer coating liquid (2-1))
An image recording layer coating liquid (2-1) was prepared by mixing a mixed liquid containing components other than the following microgel liquid 2 and the following microgel liquid 2 immediately before coating and stirring the mixture.
-Infrared absorber IR-1 (the following structure, HOMO: -5.31 eV, LUMO: -3.75 eV): 0.00600 parts-Infrared absorber IR-2 (the following structure, HOMO: -5.31 eV, LUMO: -3.78eV): 0.0200 parts, color former S-1 (following structure): 0.02500 parts, electron-accepting polymerization initiator Int-1 (following structure, HOMO: -6.70eV, LUMO: -3 .08 eV): 0.11000 parts ・ Electron donation type polymerization initiator TPB (structure below, HOMO: -5.90 eV): 0.02500 parts ・ Polymerizable compound M-1 (obtained by the following synthesis method) : 0.27500 parts ・ Anionic surfactant A-1 (following structure): 0.09000 parts ・ Fluorine surfactant W-1 (following structure): 0.00416 parts ・ 2-Butanone: 4.9200 parts ・1-methoxy-2-propanol: 3.1000 parts, methanol: 2.7900 parts, microgel solution 2 (obtained by the following preparation method): 2.90700 parts

(Preparation of image recording layer coating liquid (2-2))
The image recording layer coating liquid (2-2) was prepared in the same manner as in the preparation of the image recording layer coating liquid (2-1) except that the color developing agent S-3 (the structure described below) was used instead of the color developing agent S-1. Was prepared.

(Preparation of image recording layer coating liquid (2-3))
The image recording layer coating liquid (2-3) was prepared in the same manner as in the preparation of the image recording layer coating liquid (2-1) except that the color developing agent S-4 (the structure described below) was used instead of the color developing agent S-1. Was prepared.

(Preparation of image recording layer coating liquid (3))
The image recording layer coating liquid (3) was prepared by mixing the following components.
-Electronic accepting polymerization initiator Int-2 (following structure, HOMO: -6.96eV, LUMO: -3.18eV): 0.060 parts-Infrared absorber IR-3 (following structure, HOMO: -5.43eV) , LUMO: -3.95 eV): 0.026 parts-Electronic donation type polymerization initiator TPB (following structure, HOMO: -5.90 eV): 0.050 parts-Polymerable compound M-2 (following structure): 0 .250 parts ・ Polymerizable compound M-3 (following structure): 0.250 parts ・ Binder polymer BP-1 (following structure, Eslek BX-5 (Z), Sekisui Chemical Industry Co., Ltd .: 0.150 parts ・ 1 -Polymer-2-propanol: 4.988 parts, 2-butanone: 9.262 parts

(Preparation of image recording layer coating liquid (4))
The image recording layer coating liquid (4) was prepared by mixing the following components.
-Electronic accepting polymerization initiator Int-3 (following structure, HOMO: -7.34eV, LUMO: -3.26eV): 0.041 parts-Infrared absorber IR-4 (following structure, HOMO: -5.42eV) , LUMO: -3.82eV): 0.027 parts-Infrared absorber IR-5 (structure below, HOMO: -5.43 eV, LUMO: -3.84 eV): 0.015 parts-Polymer compound M-4 (Structure below): 0.100 parts-Polymer compound M-5 (Structure below): 0.096 parts Polymerizable compound M-6 (Structure below): 0.096 parts Polymer particles PP-1 (Structure below) Particles containing the polymer of, average particle size 100 μm): 0.300 parts ・ Color former S-2 (following structure): 0.041 parts ・ Hydroxypropyl cellulose: 0.030 parts ・ n-propanol: 5.168 parts ・2-butanone: 6.460 parts, 1-methoxy-2-propanol: 1.615 parts, methanol: 2.907 parts

The details of each component used in each of the above-mentioned and later-described image recording layer coating liquids are as follows.
In BP-1, l is 72 mol%, m is 1 mol%, n is 27 mol%, and the weight average molecular weight is 130,000.
In PP-1, n is 40 and the weight average molecular weight is 90,000.
Int-3 is a mixture of compounds formed by each of the following two iodonium cation structures and the following counter anion (ie, tetraphenylborate ion).

[Synthesis of polymerizable compound M-1]
Takenate D-160N (polyisocyanate trimethylolpropane adduct, manufactured by Mitsui Chemicals, Inc.) 4.7 parts by mass, Aronix M-403 (manufactured by Toagosei Co., Ltd.) NCO value and Aronix M-403 of Takenate D-160N A mixed solution of 0.02 part by mass of t-butylbenzoquinone and 11.5 parts by mass of methylethylketone was heated to 65 ° C. in an amount such that the hydroxyl value of T-butylbenzoquinone was 1: 1. To the reaction solution, 0.11 part by mass of Neostan U-600 (bismuth-based polycondensation catalyst, manufactured by Nitto Kasei Co., Ltd.) was added, and the mixture was heated at the same temperature for 4 hours. The reaction solution was cooled to room temperature (25 ° C.), and methyl ethyl ketone was added to synthesize a urethane acrylate solution having a solid content of 50% by mass.
Subsequently, a recycled GPC (equipment: LC908-C60, column: JAIGEL-1H-40 and 2H-40 (manufactured by Nippon Analytical Industry Co., Ltd.)) was used in a tetrahydrofuran (THF) eluent, and the molecular weight of the urethane acrylate solution was increased. Fractionation was carried out. The weight average molecular weight of the obtained polymerizable compound M-1 was 20,000.

[Preparation of Microgel Liquid 1]
-Preparation of multivalent isocyanate compound-
Bismastris (2-ethyl) in a suspension solution of ethyl acetate (25.31 parts) containing 17.78 parts (80 mol equivalents) of isophorone diisocyanate and 7.35 parts (20 mol equivalents) of the following polyvalent phenol compound (1). Hexanoate) (Neostan U-600, manufactured by Nitto Kasei Co., Ltd.) 0.043 part was added and stirred. When the exotherm 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 the polyhydric isocyanate compound (1).

-Preparation of microgel-
The following oil phase components and aqueous phase components were mixed and emulsified at 12,000 rpm for 10 minutes using a homogenizer. After stirring the obtained emulsion at 45 ° C. for 4 hours, 10 mass of 1,8-diazabicyclo [5.4.0] undec-7-en-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) 5.20 g of a% aqueous solution was added, the mixture was stirred at room temperature for 30 minutes, and allowed to stand at 45 ° C. for 24 hours. The solid content concentration was adjusted to 20% by mass with distilled water to obtain an aqueous dispersion of Microgel 1 (that is, Microgel Solution 1). When the average particle size of Microgel 1 was measured by the light scattering method, it was 0.28 μm.

~ Oil phase component ~
(Component 1) Ethyl acetate: 12.0 parts (Component 2) Trimethylolpropane (6 molar equivalents) and xylenedi isocyanate (18 molar equivalents) are added to this, and one-terminal methylated polyoxyethylene (1 molar equivalent, oxy) is added. Additive (50 mass% ethyl acetate solution, manufactured by Mitsui Kagaku Co., Ltd.) to which an ethylene unit repetition number: 90) was added: 3.76 parts (component 3) Polyvalent isocyanate compound (1) (50 mass% acetate) As an ethyl solution): 15.0 parts (component 4) 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartmer) 11.54 parts (component 5) sulfonate type surfactant (Pionin A-41-C, manufactured by Takemoto Oil & Fat Co., Ltd.) 10% ethyl acetate solution: 4.42 parts ~ aqueous phase component ~
Distilled water: 46.87 parts

[Preparation of microgel solution 2]
-Preparation of oil phase components-
Polyfunctional isocyanate compound (PM-200: manufactured by Manka Kagaku): 6.66 g and "Takenate (registered trademark) D-116N (trimethylolpropane (TMP) and m-xylylene diisocyanate" manufactured by Mitsui Kagaku Co., Ltd. Addition of XDI) and polyethylene glycol monomethyl ether (EO90) (structure below) ”50 mass% ethyl acetate solution: 5.46 g and dipentaerythritol pentaacrylate (SR-399, manufactured by Sartmer) 65 mass% acetate Ethyl solution: 11.24 g, ethyl acetate: 14.47 g, and Pionin (registered trademark) A-41-C: 0.45 g manufactured by Takemoto Oil & Fat are mixed and stirred at room temperature (25 ° C.) for 15 minutes to obtain oil. Phase components were obtained.

-Preparation of aqueous phase components-
As an aqueous phase component, 47.2 g of distilled water was prepared.

-Microcapsule forming process-
The aqueous phase component was added to the oil phase component and mixed, and the obtained mixture was emulsified at 12,000 rpm for 16 minutes using a homogenizer to obtain an emulsion.
16.8 g of distilled water was added to the obtained emulsion, and the obtained liquid was stirred at room temperature for 10 minutes.
Next, the stirred liquid was heated to 45 ° C., and the mixture was stirred for 4 hours while maintaining the liquid temperature at 45 ° C. to distill off ethyl acetate from the above liquid. Next, 5.12 g of a 10% by mass aqueous solution of 1,8-diazabicyclo [5.4.0] undec-7-en-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) was added, and the mixture was added at room temperature for 30 minutes. The mixture was stirred and allowed to stand at 45 ° C. for 24 hours. The solid content concentration was adjusted to 20% by mass with distilled water, and an aqueous dispersion of Microgel 2 was obtained. The volume average particle size of the microgel 2 was 165 nm as measured by a laser diffraction / scattering type particle size distribution measuring device LA-920 (manufactured by HORIBA, Ltd.).
The obtained aqueous dispersion of the polymer particles 2 was designated as a microgel solution 2.

(Preparation of image recording layer coating liquid (5))
An image recording layer coating liquid (5) was prepared by mixing a mixed liquid containing components other than the following microgel liquid 3 and the following microgel liquid 3 immediately before coating and stirring the mixture.
-Binder polymer BP-2 (following structure): 0.240 parts-Infrared absorber IR-6 (following structure, HOMO: -5.38eV, LUMO: -3.70eV): 0.030 parts-Polymerization initiator Int -4 (structure below, HOMO: -6.70 eV, LUMO: -3.08 eV): 0.162 parts-Polymerizable compound: 0.192 parts (Tris (acryloyloxyethyl) isocyanurate, NK ester A-9300, Shin-Nakamura Chemical Co., Ltd.
-Low molecular weight hydrophilic compound (Tris (2-hydroxyethyl) isocyanurate): 0.062 parts-Low molecular weight hydrophilic compound A-1 (the above structure): 0.050 parts-Fat sensitive agent C-1 (below) Structure): 0.055 parts-Fat sensitive agent (benzyl-dimethyl-octylammonium / PF ₆ salt): 0.018 parts-Fat sensitive agent C-2 (following structure, reduction specific viscosity 44 ml / g): 0 .035 parts ・ Fluorosurfactant W-1 (the above structure): 0.008 parts ・ 2-Butanone: 1.091 parts ・ 1-methoxy-2-propanol: 8.609 parts ・ Microgel solution 3 (below Obtained by the preparation method): 5.065 parts

The details of each component used in the image recording layer coating liquid (5) are as follows.

[Preparation of microgel solution 3]
As oil phase components, trimethylolpropane and xylene diisocyanate adduct (Mitsui Chemicals Polyurethane Co., Ltd., Takenate D-110N) 10 g, pentaerythritol triacrylate (Nippon Kayaku Co., Ltd., SR444) 3.15 g, And 0.1 g of Pionin A-41C (manufactured by Takemoto Oil & Fat Co., Ltd.) was dissolved in 17 g of ethyl acetate. As an aqueous phase component, 40 g of a 4% by mass aqueous solution of polyvinyl alcohol (PVA-205 manufactured by Kuraray Co., Ltd.) was prepared.
The oil phase component and the aqueous phase component were mixed and emulsified at 12,000 rpm for 10 minutes using a homogenizer. The obtained emulsion was added to 25 g of distilled water, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours. The solid content concentration of the microgel solution thus obtained was diluted with distilled water so as to be 15% by mass.
When the average particle size of the microgel was measured by the light scattering method, the average particle size was 0.2 μm.
2.640 parts of the microgel liquid obtained as described above and 2.425 parts of distilled water were mixed to obtain a microgel liquid 3.

<Preparation of outermost layer coating liquid>
Each component shown in Table 1 below was mixed to obtain outermost layer coating liquids (1) to (27).

Details of the various components used in Table 1 are shown below.
-Water-soluble polymer-
-Gosenex L-3266: Sulfonic acid-modified polyvinyl alcohol having the following structure, Gosenex (registered trademark) L-3266 manufactured by Mitsubishi Chemical Corporation.

-Gosenex CKS-50: Sulfonic acid-modified polyvinyl alcohol with the following structure, Gosenex (registered trademark) CKS-50 manufactured by Mitsubishi Chemical Corporation

-Water-soluble polymer 1: Polymer having the following structure

-Mowiol 4-88: Polyvinyl alcohol particles having a saponification degree of 88 mol%, Mowiol (registered trademark) 4-88 manufactured by Sigma-Aldrich.
-Metro's SM04: Methyl cellulose (Methoxy substitution degree 1.8), Metrose (registered trademark) SM04 manufactured by Shin-Etsu Chemical Co., Ltd.
-Metro's SM15: Methyl cellulose (Methoxy substitution degree 1.8, high viscosity), Metrose (registered trademark) SM15 manufactured by Shin-Etsu Chemical Co., Ltd.
-Metro's 60SH 50: Hyroxypropylmethylcellulose (methoxy-substitution degree 1.9), Metrose (registered trademark) 60SH 50 manufactured by Shin-Etsu Chemical Co., Ltd.
・ Cellogen F 5A: Sodium Carboxymethyl Cellulose, Cellogen (registered trademark) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.
・ Penon JE-66: Modified starch, manufactured by Nissho Kagaku Co., Ltd.

-Hydrophobic polymer-
-Finesphere FS-102: Water dispersion of styrene acrylic resin particles having the following structure, glass transition temperature Tg 103 ° C, softening point 225 ° C, Finesphere (registered trademark) FS-102 manufactured by Nippon Paint Industrial Coatings Co., Ltd.

-Polymaron 385: Styrene acrylic resin dispersion, Polymaron 385 manufactured by Arakawa Chemical Industry Co., Ltd.
AQUAMAT 263: Oxidized High Density Polyethylene Wax Dispersion, BYK AQUAMAT® 263
-Takeseal PCeco Primer: Emulsion of styrene acrylic resin, manufactured by Takebayashi Chemical Industry-Diofan A50: Polyvinylidene chloride aqueous dispersion, Diofan (registered trademark) A50 manufactured by Solvin
-Diofan A602: Polyvinylidene chloride dispersion, Diofan (registered trademark) A602 manufactured by Solvin.

-Other ingredients-
-Microgel liquid 2: The above-mentioned microgel liquid 2
・ Decomposition type infrared absorber 1: Compound with the following structure

[Examples 1 to 29 and Comparative Examples 1 to 2]
The lithographic printing plate original plates of Examples 1 to 29 and Comparative Examples 1 and 2 were prepared by the following methods, respectively.
The undercoat layer coating liquid shown in Table 2 was applied onto the support shown in Table 2 so that the dry coating amount was 20 mg / m ² to form an undercoat layer.
Next, the image recording layer coating liquid shown in Table 2 was bar-coated on the undercoat layer so as to have a dry coating amount of 1.0 g / m ^2, and dried in an oven at 120 ° C. for 40 seconds to form an image recording layer. bottom.
For the lithographic printing plate original plate having no undercoat layer, the image recording layer coating liquid shown in Table 2 is applied on the support shown in Table 2 under the same conditions as above, and the dry coating amount is 1. A bar was applied so as to be 0 g / m ^{2 to form an image recording layer.}
Then, the outermost layer coating liquid shown in Table 2 is bar-coated on the obtained image recording layer so as to have a dry coating amount of 0.2 g / m ² , and dried in an oven under the drying conditions shown in Table 2. Then, the outermost layer was formed.
As described above, an on-machine development type lithographic printing plate original plate was obtained.
In the obtained on-machine development type lithographic printing plate original plate, the film thickness of the outermost layer was in the range of 0.005 μm to 2 μm.

<Evaluation of lithographic printing plate original plate>
[Decomposition rate of infrared absorber]
For the obtained lithographic printing plate original plate, the decomposition rate of the infrared absorber in the image recording layer was determined by the method described above.
The results are shown in Table 2.

[Evaluation of discoloration due to ozone exposure]
When obtaining the decomposition of the infrared absorbing agent as described above, measuring ^L * of sample before ozone ^exposure, a *, and ^{b *,} ^L * of the sample after ozone ^exposure, a *, and ^{b *,} respectively ^{The color difference ΔE was calculated from the obtained values of L *} , a ^* and b ^* by measuring with a color meter (X-Rite eXact) using the CIE 1976 color difference calculation formula. Based on the difference in the obtained color difference ΔE values before and after ozone exposure, the discoloration of the lithographic printing plate original plate due to ozone exposure was evaluated according to the following criteria. The results are shown in Table 2.
-Evaluation criteria-
10: The difference in color difference ΔE before and after ozone exposure is less than 0.5 9: The difference in color difference ΔE before and after ozone exposure is 0.5 or more and less than 1.0 8: The difference in color difference ΔE before and after ozone exposure is 1. 0 or more and less than 1.5 7: Difference of color difference ΔE before and after ozone exposure is 1.5 or more and less than 2.0 6: Difference of color difference ΔE before and after ozone exposure is 2.0 or more and less than 2.5 5: Color difference ΔE Difference between before and after ozone exposure is 2.5 or more and less than 3.0 4: Difference between before and after ozone exposure of color difference ΔE is 3.0 or more and less than 3.5 3: Difference between color difference ΔE before and after ozone exposure is 3. 5 or more and less than 4.0 2: Difference in color difference ΔE before and after ozone exposure 4.0 or more and less than 4.5 1: Difference in color difference ΔE before and after ozone exposure is 4.5 or more

[Oxygen permeability]
For the obtained lithographic printing plate original plate, the halftone dot area ratio was calculated by the method described above, and the presence or absence of oxygen permeability was confirmed.
The results are shown in Table 2.

[Evaluation of streak-like unevenness (swath unevenness)]
When confirming the oxygen permeability, the streak-like unevenness (swath unevenness) was evaluated using the 1000th printed matter produced by the lithographic printing plate obtained from the lithographic printing plate original plate having the outermost layer.
More specifically, the 50% halftone dot chart portion of the FM screen of the 1000th printed matter was observed, and the streak-like unevenness (swallow unevenness) was evaluated according to the following criteria. The results are shown in Table 2.
-standard-
5: Swathmura cannot be visually confirmed using a 6x loupe 4: Swathmura can be slightly visually confirmed using a 6x loupe 3: Swathmura can be clearly visually confirmed using a 6x loupe 2: Swathmura can be slightly visually confirmed Can be confirmed 1: Swath unevenness can be clearly visually confirmed

[In-machine developability]
The prepared planographic printing plate original plate was exposed to Kodak's Magnus 800 Quantum equipped with an infrared semiconductor laser under the conditions of an output of 27 W, an outer surface drum rotation speed of 450 rpm, and a resolution of 2,400 dpi (corresponding to an ^{irradiation energy of 110 mJ / cm 2).} The exposed image includes a solid image and a chart of 10% halftone dots on the AM screen (Amplitude Modulation Screen).
The exposed original plate was attached to the cylinder of a Heidelberg printing machine SX-74 of a chrysanthemum size (636 mm × 939 mm) without being developed. A non-woven fabric filter and a dampening water circulation tank having a capacity of 100 L having a built-in temperature control device were connected to the printing machine. Damping water S-Z1 (manufactured by Fujifilm Co., Ltd.) 2.0% by mass of dampening water 80L is charged in a circulation device, and T & K UV OFS K-HS ink GE-M, which is an ultraviolet curable ink, is used as a printing ink. After supplying dampening water and ink using the standard automatic printing start method using (manufactured by T & K TOKA Co., Ltd.), Tokubishi Art (ream amount: 76.5 kg, Mitsubishi Paper Mills Limited) at a printing speed of 10,000 sheets per hour. Co., Ltd. Printing was performed on 500 sheets of paper.
During printing, the number of sheets of printing paper required until the ink was not transferred to the non-image area was measured as the on-machine developability. It can be said that the smaller the number of sheets, the better the on-machine developability. The results are shown in Table 2.

As is clear from Table 2, it can be seen that the lithographic printing plate original plate according to the example has suppressed discoloration due to ozone exposure as compared with the lithographic printing plate original plate according to the comparative example.
Further, the lithographic printing plate original plate according to the embodiment has an outermost layer having oxygen permeability. Therefore, it seems that streak-like unevenness (swallow unevenness) is suppressed.

[Explanation of code]
18: Aluminum plate, 12a, 12b: Aluminum support, 20a, 20b: Anodized film, 22a, 22b: Micropore, 24: Large diameter hole, 26: Small diameter hole

The disclosures of Japanese Patent Application No. 2020-095073 filed on May 29, 2020 and Japanese Patent Application No. 2021-002219 filed on January 8, 2021 are herein by reference in their entirety. Incorporated into the book. All documents, patent applications, and technical standards described herein are to the same extent as specifically and individually stated that the individual documents, patent applications, and technical standards are incorporated by reference. Incorporated herein by reference.

Claims

It has a support, an image recording layer, and an outermost layer in this order.
The image recording layer contains a polymerization initiator, a polymerizable compound, and an infrared absorber.
The decomposition rate of the infrared absorber after storage for 8 hours in an environment with an ozone concentration of 150 ppb is 50% or less.
On-machine development type lithographic printing plate original plate.
The machine-developed lithographic printing plate original plate according to claim 1, wherein the outermost layer has a film thickness of 0.005 μm to 2 μm.
The machine-developed lithographic printing plate original plate according to claim 1 or 2, wherein the outermost layer has oxygen permeability.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 3, wherein the outermost layer contains a polysaccharide.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 4, wherein the outermost layer contains a cellulose derivative having a degree of methoxy group substitution of 1 to 2.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 5, wherein the outermost layer further contains a hydrophobic polymer.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 6, wherein the outermost layer further contains polymer particles.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 7, wherein the outermost layer contains a decomposable infrared absorber.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 8, wherein the polymerization initiator contains an electron donating type polymerization initiator and an electron accepting type polymerization initiator.
The machine-developed lithographic printing plate original plate according to claim 9, wherein the value of HOMO of the infrared absorber-HOMO of the electron donating type polymerization initiator is 0.70 eV or less.
The machine-developed lithographic printing plate original plate according to claim 9 or 10, wherein the value of LUMO of the electron-accepting polymerization initiator-LUMO of the infrared absorber is 0.80 eV or less.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 11, wherein the polymerizable compound contains a polymerizable compound having 7 or more functionalities.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 12, wherein the polymerizable compound contains a polymerizable compound having 10 or more functionalities.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 13, wherein the image recording layer further contains polymer particles.
The polymer particles are addition polymerization type polymer particles having a hydrophilic group, and the polymer particles are
The machine-developed lithographic printing plate original plate according to claim 14, wherein the hydrophilic group contains a group represented by the following formula Z.
Formula Z: * -Q-W-Y
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, and Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophilic structure. A monovalent group having a hydrophobic structure is represented, either W or Y has a hydrophilic structure, and * represents a binding site with another structure.
The machine-developed lithographic printing plate original plate according to any one of claims 1 to 15, wherein the image recording layer further contains a color former.
The machine-developed lithographic printing plate original plate according to claim 16, wherein the color former is a compound represented by any of the following formulas (Le-1) to (Le-3).

In the formulas (Le-1) to (Le-3), ERG independently represents an electron donating group, and X 1 to X 4 independently represent a hydrogen atom, a halogen atom, or a dialkylanilino. 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 Y 1 represents a group. When N, X 1 does not exist, when Y 2 is N, X 4 does not exist, Ra 1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb 1 to Rb 4 Independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.
The machine-developed lithographic printing plate original plate according to claim 16 or 17, wherein the color former is a compound represented by the following formula (Le-8).

In formula (Le-8), X 1 to X 4 independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, and Y 1 and Y 2 independently represent C or N, respectively. If Y 1 is N, then X 1 is absent, if Y 2 is N, then X 4 is absent, and Rb 1 and Rb 2 are independently alkyl, aryl, or, respectively. Representing a heteroaryl group, Rc 1 and Rc 2 independently represent an aryl group or a heteroaryl group, respectively.
The on-machine development type according to claim 18, wherein Rc 1 and Rc 2 are phenyl groups each independently having a substituent at at least one ortho position and an electron donating group at the para position. Planographic printing plate original plate.
The machine-developed lithographic printing plate original plate according to claim 16 or 17, wherein the color former contains a compound represented by the following formula (Le-10).

In formula (Le-10), Ar 1 independently represents an aryl group or a heteroaryl group, and Ar 2 independently represents an aryl group having a substituent at at least one ortho position, or at least 1 Represents a heteroaryl group having a substituent at one ortho position.
The Ar 1 is an aryl group having an electron-donating group or a heteroaryl group having an electron-donating group, and Ar 2 is each independently having a substituent at at least one ortho-position. The machine-developed flat plate printing plate original plate according to claim 20, which is a phenyl group having and having an electron donating group at the para position.
The support has an aluminum plate and an aluminum anodic oxide film arranged on the aluminum plate.
The anodic oxide film is located closer to the image recording layer than the aluminum plate.
The anodic oxide film has micropores extending in the depth direction from the surface on the image recording layer side.
The average diameter of the micropores on the surface of the anodic oxide film is more than 10 nm and 100 nm or less.
The aspect according to any one of claims 1 to 21, wherein the value of L * a * b * brightness L * in the surface of the anodized film on the image recording layer side is 70 to 100. On-machine development type lithographic printing plate original plate.
The micropore communicates with the large-diameter hole extending from the surface of the anodic oxide film to a depth of 10 nm to 1,000 nm and the bottom of the large-diameter hole, and has a depth of 20 nm to 2,000 nm from the communication position. It consists of a small-diameter hole that extends to the position.
The average diameter of the large-diameter hole portion on the surface of the anodic oxide film is 15 nm to 100 nm.
The machine-developed lithographic printing plate original plate according to claim 22, wherein the small diameter hole portion has an average diameter of 13 nm or less at the communication position.
The step of exposing the machine-developed lithographic printing plate original plate according to any one of claims 1 to 23 to an image.
A method for producing a lithographic printing plate, comprising a step of supplying at least one selected from the group consisting of printing ink and dampening water on a printing machine to remove an image recording layer in a non-image area.
The step of exposing the machine-developed lithographic printing plate original plate according to any one of claims 1 to 23 to an image.
A process 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 a printing machine to produce a lithographic printing plate, and printing with the obtained lithographic printing plate. And lithographic printing methods, including.