JP7064595B2 - Machine-developed lithographic printing plate original plate, lithographic printing plate manufacturing method, and lithographic printing method - Google Patents

Description

The present 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 (ink non-receptive part). This is a method in which a difference in the adhesiveness of ink is generated on the surface of a flat plate printing plate, the ink is inlaid only on the image portion, and then the ink is transferred to an object to be printed such as paper for printing.
In order to produce this lithographic printing plate, a lithographic printing plate original plate (PS plate) in which a lipophilic photosensitive resin layer (image recording layer) is provided on a hydrophilic support has been widely used. 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 the 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 issues, simplification and non-processing of development or plate making are aimed at. As one of the simple manufacturing methods, a method called "on-machine development" is performed. That is, after the lithographic printing plate original plate is exposed, the conventional development is not performed, but the printing machine is mounted as it is, and the unnecessary portion of the image recording layer is removed at the initial stage of the normal printing process.
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 printing method using the conventional lithographic printing plate original plate or the lithographic printing plate original plate include those described in Patent Documents 1 to 3.

Patent Document 1 describes a negative lithographic printing plate original plate having a support and an image recording layer containing a compound having a repeating unit represented by the following general formula (1) and a radical polymerization initiator.

In the general formula (1), A represents a single bond or a divalent linking group. Ar represents a benzene nucleus or a naphthalene nucleus. R ¹ represents a hydroxy group, an alkyl group or an aryl group. i represents an integer from 0 to 3. When i represents an integer of 2 or more, a plurality of R ^1s may be the same or different. R ² represents a hydrogen atom, an alkyl group or an aryl group. L represents * -O-**, * -OCO-** or * -OCONH-**. * Represents a site that binds to Ar. ** represents a site that binds to Y. Y represents a (m + 1) valence linking group. X represents a (meth) acryloyloxy group.
l represents an integer of 0 or 1. m represents an integer of 1 or 2. However, when l is 0, m is 1. n represents an integer of 1 or 2.

Patent Document 2 includes a substrate having an image-forming layer on top, and the image-forming layer initiates polymerization of a free radical polymerizable component by exposure to a free radical polymerizable component and an image forming radiation. An initiator composition capable of producing sufficient free radicals, the initiator composition containing diaryliodonium borate, an infrared absorbent cyanine dye having a methine chain to which a heterocyclic group is linked, and the like. Here, the methine chain has at least 7 carbon atom chain lengths and comprises a primary polymer binder, and the image-forming element further comprises an overcoat placed on the image-forming layer. The overcoat describes an image-forming element mainly composed of a poly (vinyl alcohol) having a degree of hydrolysis of 85% or less.

Patent Document 3 describes a substrate, a negative image-forming layer arranged on the substrate, a free radical polymerizable component, and an initiator composition capable of generating free radicals when exposed to imaging radiation. A negative image-forming layer containing a substance, a radiation absorber, and a polymer binder, and an outermost water-soluble overcoat layer directly arranged on the negative image-forming layer, (1) present. One or more film-forming water-soluble polymer binders, and (2) the above one or more in an amount of at least 1.3% by weight and up to 60% by weight based on the total outermost water-soluble overcoat layer weight. A negative type slab printing plate original plate containing an outermost water-soluble overcoat layer containing organic wax particles dispersed in the film-forming water-soluble polymer binder, wherein the organic wax particles are the dry outermost water-soluble overcoat layer. A negative slab printing plate precursor with an average maximum dimension of at least 0.05 μm and a maximum of 0.7 μm, as measured from the scanning electron micrographs of the above, is described.

Patent Document 1: Japanese Patent Application Laid-Open No. 2017-132227 Patent Document 2: Japanese Patent Application Laid-Open No. 2010-528490 Patent Document 3: Japanese Patent Application Laid-Open No. 2015-591610

During the above-mentioned on-machine development, development residue (on-machine development residue) may be generated.
When such on-board developing debris is generated, it may cause contamination of dampening water and printing stains due to contamination of non-image areas. Therefore, in the field of lithographic printing plate original plate, on-machine developing debris is generated. There is a demand for an suppressed on-board development type lithographic printing plate original plate.
Further, it is said that the short time from the start of printing on the lithographic printing plate to the adhesion of ink to the printing portion (image portion) is excellent in ink inking property (simply referred to as "inking property"). In the field of lithographic printing plate original plates, there is a demand for on-machine development type lithographic printing plate original plates having excellent ink inking properties for the reasons such as shortening the time to start printing and suppressing blurring in printed matter.
The present inventors have described 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 as a machine rather than the lithographic printing plate original plate described in Patent Documents 1 to 3. It has been found that the generation of development residue during top development is suppressed and the ink adhesion is excellent.

The problem to be solved by one embodiment of the present disclosure is the on-board development type lithographic printing plate original plate, which suppresses the generation of development residue during on-machine development and has excellent ink infiltration property, and the above-mentioned on-machine development type lithographic printing plate. It is an object of the present invention to provide a method for manufacturing a lithographic printing plate using a printing plate original plate and a lithographic printing method using the above-mentioned on-machine development type lithographic printing plate original plate.

The means for solving the above problems include the following aspects.
<1> A support, an image recording layer, and an overcoat layer are provided in this order.
The image recording layer contains a binder polymer and a development accelerator.
The binder polymer has a structural unit formed of an aromatic vinyl compound and a structural unit formed of an acrylonitrile compound.
The value of the polarity term of the SP value of the development accelerator is 6.0 to 26.0.
An on-machine development type lithographic printing plate original plate in which the film thickness of the overcoat layer is thicker than the film thickness of the image recording layer.
<2> The above-mentioned <1>, wherein the image recording layer further contains a polymerizable compound, and the content of the binder polymer with respect to the total mass of the polymerizable compound is more than 0% by mass and 400% by mass or less. On-machine development type lithographic printing plate original plate.
<3> The machine-developed lithographic printing plate original plate according to <1> or <2>, wherein the overcoat layer contains a water-soluble polymer.
<4> The machine-developed lithographic printing plate original plate according to <3>, wherein the water-soluble polymer contains polyvinyl alcohol having a saponification degree of 50% or more.
<5> The machine-developed lithographic printing plate original plate according to any one of <1> to <4>, wherein the development accelerator is a compound having a cyclic structure.
<6> The machine-developed lithographic printing plate original plate according to <5>, wherein the compound having a cyclic structure has a hydroxy group.
<7> The machine-developed lithographic printing plate original plate according to any one of <1> to <6>, wherein the development accelerator is an onium compound.
<8> The machine-developed lithographic printing plate original plate according to any one of <1> to <7>, which contains two or more compounds as the development accelerator.
<9> The machine-developed lithographic printing plate original plate according to any one of <1> to <8>, wherein the binder polymer further has a structural unit formed by N-vinylpyrrolidone.
<10> The machine-developed lithographic printing plate original plate according to any one of <1> to <9>, wherein the image recording layer further contains an infrared absorber.
<11> The machine-developed lithographic printing plate original plate according to <10>, wherein the infrared absorber is an infrared absorber that decomposes by infrared exposure.
<12> The machine-developed lithographic printing plate original plate according to <10> or <11>, wherein the infrared absorber is an infrared absorber that decomposes due to heat, electron transfer, or both caused by infrared exposure.
<13> The machine-developed lithographic printing plate original plate according to any one of <10> to <12>, wherein the infrared absorber is a cyanine pigment.
<14> The machine-developed lithographic printing plate original plate according to any one of <10> to <113>, wherein the infrared absorber is a compound represented by the following formula 1.

In Equation 1, R ¹ represents a group in which the R ¹ -L bond is cleaved by infrared exposure, and R ₁₁ to R ₁₈ independently contain a hydrogen atom, a halogen atom, -Ra, -ORb, -SRc or -NRdRe. Ra to Re each independently represent a hydrocarbon group, and A ₁ , A ₂ and a plurality of R ₁₁ to R ₁₈ may be linked to form a single ring or a poly ring, and A ₁ and A ₂ may be formed. Independently represent an oxygen atom, a sulfur atom or a nitrogen atom, and n ₁₁ and n ₁₂ each independently represent an integer of 0 to 5, where the sum of n ₁₁ and n ₁₂ is 2 or more and n. ₁₃ and n ₁₄ independently represent 0 or 1, L represents an oxygen atom, a sulfur atom or -NR ^10- , R ¹⁰ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a charge neutralizing. Represents a counter ion.

<15> The machine-developed lithographic printing plate original plate according to <14>, wherein R ¹ in the above formula 1 is a group represented by the following formula 2.

In the formula 2, R ^Z represents an alkyl group, and the wavy line portion represents a binding site with a group represented by L in the above formula 1.
<16> A step of exposing the machine-developed lithographic printing plate original plate according to any one of <1> to <15> 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 to remove an image recording layer of a non-image portion on a printing machine.
<17> The step of exposing the machine-developed lithographic printing plate original plate according to any one of <1> to <15> 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 of the non-image area on the printing machine to prepare a lithographic printing plate.
A lithographic printing method including a step of printing with the obtained lithographic printing plate.

According to one embodiment of the present disclosure, the on-machine development type lithographic printing plate original plate and the above-mentioned on-machine development type lithographic printing plate original plate, in which the generation of development residue during on-machine development is suppressed and the ink adhesion is excellent, are used. It is possible to provide a method for manufacturing a lithographic printing plate used and a lithographic printing method using the above-mentioned on-machine development type lithographic printing plate original plate.

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 addition, in this specification, "-" indicating a numerical range is used in the sense that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.
Further, in the notation of a group (atomic group) in the present specification, 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).
As used herein, "(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. Is.
In addition, the term "process" in the present specification is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term "process" will be used as long as the intended purpose of the process is achieved. included. Further, in the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.
Unless otherwise specified, in the present disclosure, each component in the composition or each structural unit in the polymer may be contained alone or in combination of two or more. ..
Further, in the present disclosure, the amount of each component in the composition or each structural unit in the polymer has a plurality of substances or structural units corresponding to each component or each structural unit in the polymer in the composition. In the case, unless otherwise specified, it means the total amount of each of the plurality of applicable substances present in the composition or the plurality of applicable constituent units present in the polymer.
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. It is a molecular weight converted by using a gel permeation chromatography (GPC) analyzer as a standard material, which is detected by a solvent THF (tetrahydrofuran) and a differential refraction meter.
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.
Further, in the present disclosure, "*" in the chemical structural formula represents a bonding position with another structure.
Hereinafter, the present disclosure will be described in detail.

(In-machine development type lithographic printing plate original plate)
The on-machine development type flat plate printing plate original plate according to the present disclosure has a support, an image recording layer, and an overcoat layer in this order, and the image recording layer contains a binder polymer and a development accelerator. The binder polymer has a structural unit formed of an aromatic vinyl compound and a structural unit formed of an acrylonitrile compound, and the value of the polar term of the SP value of the development accelerator is 6.0 to 1. It is 26.0, and the film thickness of the overcoat layer is thicker than the film thickness of the image recording layer.

As a result of diligent studies by the present inventors, by adopting the above configuration, it is possible to provide a lithographic printing plate original plate having excellent on-machine developability and suppressing the generation of development residue during on-machine development. I found.
The detailed mechanism by which the above effect is obtained is unknown, but it is presumed as follows.
In the field of on-machine development type lithographic printing plate original plate, it is known to use a development accelerator for an image recording layer in order to improve on-machine developability.
When the development accelerator is simply added to the image recording layer, the present inventors may dissolve the components of the image recording layer in water due to watering the printing plate original plate or the like, and development residue may be easily generated. I found that.
Therefore, as a result of diligent studies, the present inventors have found that the generation of the development residue is suppressed by providing the overcoat layer on the image recording layer.
Further, the present inventors have provided a development accelerator having an overcoat layer and having a polar term of SP value of 6.0 to 26.0 (hereinafter, also referred to as “specific development accelerator”). It has been found that the use may reduce the inking property of the ink at the time of printing.
Therefore, as a result of diligent studies, the present inventors have found a binder polymer having a structural unit formed of an aromatic vinyl compound and a structural unit formed of an acrylonitrile compound (hereinafter, also referred to as "specific binder polymer"). It has been found that the use thereof improves the inking property of the ink.
As described above, in the on-board development type lithographic printing plate original plate according to the present disclosure, by combining the specific development accelerator, the overcoat layer, and the specific binder polymer, development residue is suppressed and ink inking property is improved. It is based on the new finding that the excellent effect of compatibility is achieved.

The lithographic printing plate original plate described in Patent Document 1 or 2 does not contain the specific binder polymer, and there is room for further improvement in the ink inking property.
The lithographic printing plate original plate described in Patent Document 3 has neither description nor suggestion that it has an overcoat layer having a film thickness thicker than that of the image recording layer, and is inferior in suppressing development residue.

Further, according to the lithographic printing plate original plate according to the present disclosure, it is considered that a lithographic printing plate having excellent on-machine developability can be easily obtained. This is due to the effect of containing the specific development accelerator, the inclusion of the specific binder polymer makes it easy for the non-image area to stick to the ink roller during in-machine development, and it is easy to remove (ink tack development). It is presumed that this is due to the synergistic effect of having the specific binder polymer and the overcoat layer.
Further, according to the lithographic printing plate original plate according to the present disclosure, it is considered that a lithographic printing plate original plate having excellent scratch resistance can be easily obtained. It is presumed that this is an effect due to having the overcoat layer and the like.

<Support>
The lithographic printing plate original plate according to the present disclosure has a support.
As the support, a support having a hydrophilic surface (also referred to as “hydrophilic support”) is preferable. As the hydrophilic surface, a surface having a contact angle with water of less than 10 ° is preferable, and a surface having a contact angle of less than 5 ° is more preferable.
The water contact angle in the present disclosure is measured by DM-501 manufactured by Kyowa Surface Chemistry Co., Ltd. as the contact angle (after 0.2 seconds) of water droplets on the surface at 25 ° C.
The lithographic printing plate original support according to the present disclosure can be appropriately selected from known lithographic printing plate original supports and used. As the support, an aluminum plate that has been roughened and anodized by a known method is preferable.
Further, if necessary, the aluminum plate can be subjected to micropore enlargement treatment and pore sealing treatment of the anodic oxide film described in JP-A-2001-253181 and JP-A-2001-322365, and US Pat. No. 2,714,4. Surface hydrophilization treatment with alkali metal silicate as described in 066, 3,181,461, 3,280,734 and 3,902,734, USA. A surface hydrophilization treatment with polyvinylphosphonic acid or the like as described in each of Patent Nos. 3,276,868, 4,153,461 and 4,689,272 is appropriately selected. You may go there.
The support preferably has a centerline average roughness of 0.10 μm to 1.2 μm.

If necessary, the support may be an organic polymer compound described in JP-A-5-45885 or a silicon alkoxy compound described in JP-A-6-35174 on the surface opposite to the image recording layer. It may have a backcoat layer containing.

<Image recording layer>
The lithographic printing plate original plate according to the present disclosure has an image recording layer formed on a support.
The image recording layer used in the present disclosure preferably further contains a polymerizable compound from the viewpoint of printing resistance and photosensitivity.
The image recording layer used in the present disclosure preferably further contains an electron-accepting polymerization initiator from the viewpoint of printing resistance and photosensitivity.
The image recording layer used in the present disclosure preferably further contains an electron donating type polymerization initiator from the viewpoint of printing resistance and photosensitivity.
The image recording layer used in the present disclosure preferably further contains an infrared absorber from the viewpoint of exposure sensitivity.
The image recording layer used in the present disclosure may further contain an acid color former in order to confirm the exposed portion before development.
From the viewpoint of on-machine developability, it is preferable that the unexposed portion of the image recording layer can be removed by at least one selected from the group consisting of dampening water and printing ink in the planographic printing plate original plate according to the present disclosure. ..
Hereinafter, the details of each component contained in the image recording layer will be described.

[Specific development accelerator]
The image recording layer used in the present disclosure contains a specific development accelerator.
In the present disclosure, the specific development accelerator has a polar term of SP value of 6.0 to 26.0. The value of the polarity term of the SP value is preferably 6.2 to 24.0, more preferably 6.3 to 23.5, and further preferably 6.4 to 22.0. ..

As the value of the polarity term of the SP value (solubility parameter, unit: (cal / cm ³ ) ^1/2 ) in the present disclosure, the value of the polarity term δp in the Hansen solubility parameter shall be used. The Hansen solubility parameter is a three-dimensional space in which the solubility parameter introduced by Hildebrand is divided into three components, the dispersion term δd, the polarity term δp, and the hydrogen bond term δh. , The above polar term δp is used in the present disclosure.
δp [cal / cm ³ ] is the Hansen solubility parameter-dipole interpolar force term, V [cm ³ / mol] is the molar volume, and μ [D] is the dipole moment. For δp, the following formula simplified by Hansen and Beerbower is generally used.

The specific development accelerator is not particularly limited as long as the value of the polar term of the SP value is within the above range, and is preferably a hydrophilic polymer compound or a hydrophilic low molecule compound.
In the present disclosure, hydrophilicity means that the value of the polar term of the SP value is 6.0 to 26.0, and the hydrophilic polymer compound has a molecular weight (weight average molecular weight if it has a molecular weight distribution). A compound having a molecular weight of 3,000 or more, and a hydrophilic low molecular weight compound means a compound having a molecular weight (weight average molecular weight when having a molecular weight distribution) of less than 3,000.

-Hydrophilic polymer compound-
Examples of the hydrophilic polymer compound include cellulose compounds, and cellulose compounds are preferable.
Examples of the cellulose compound include cellulose or a compound in which at least a part of cellulose is modified (modified cellulose compound), and a modified cellulose compound is preferable.
Preferred examples of the modified cellulose compound include compounds in which at least a part of the hydroxy group of cellulose is substituted with at least one group selected from the group consisting of an alkyl group and a hydroxyalkyl group.
The degree of substitution of the compound in which at least a part of the hydroxy groups of the cellulose is substituted with at least one group selected from the group consisting of an alkyl group and a hydroxyalkyl group is preferably 0.1 to 6.0. It is more preferably 1 to 4.
As the modified cellulose compound, an alkyl cellulose compound or a hydroxyalkyl cellulose compound is preferable, and a hydroxyalkyl cellulose compound is more preferable.
As the alkyl cellulose compound, methyl cellulose is preferably mentioned.
Hydroxypropyl cellulose is preferably mentioned as the hydroxyalkyl cellulose compound.

The molecular weight of the hydrophilic polymer compound (weight average molecular weight if it has a molecular weight distribution) is preferably 3,000 to 5,000,000, more preferably 5,000 to 200,000.

-Hydrophilic small molecule compound-
Examples of the hydrophilic low molecular weight compound include glycol compounds, polyol compounds, organic amine compounds, organic sulfonic acid compounds, organic sulfamine compounds, organic sulfuric acid compounds, organic phosphonic acid compounds, organic carboxylic acid compounds, betaine compounds and the like, and polyol compounds. , Organic sulfonic acid compound or betaine compound is preferable.

Examples of the glycol compound include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol, and ether or ester derivatives of these compounds.
Examples of the polyol compound include glycerin, pentaerythritol, tris (2-hydroxyethyl) isocyanurate and the like.
Examples of the organic amine compound include triethanolamine, diethanolamine, monoethanolamine and the like, and salts thereof.
Examples of the organic sulfonic acid compound include alkyl sulfonic acid, toluene sulfonic acid, benzene sulfonic acid and the like and salts thereof, and alkyl sulfonic acid having an alkyl group having 1 to 10 carbon atoms is preferable.
Examples of the organic sulfamine compound include alkylsulfamic acid and the like and salts thereof.
Examples of the organic sulfuric acid compound include alkyl sulfuric acid, alkyl ether sulfuric acid and the like and salts thereof.
Examples of the organic phosphonic acid compound include phenylphosphonic acid and the like and salts thereof.
Examples of the organic carboxylic acid compound include tartrate acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid and the like and salts thereof.
Examples of the betaine compound include a phosphobetaine compound, a sulfobetaine compound, a carboxybetaine compound and the like, and trimethylglycine is preferable.

The molecular weight of the hydrophilic low molecular weight compound (weight average molecular weight when having a molecular weight distribution) is preferably 100 or more and less than 3,000, and more preferably 300 to 2,500.

-Circular structure-
The specific development accelerator is preferably a compound having a cyclic structure.
The cyclic structure is not particularly limited, but may have a glucose ring in which at least a part of the hydroxy group may be substituted, an isocyanul ring, an aromatic ring in which a hetero atom may be present, or a hetero atom. An aliphatic ring and the like can be mentioned, and a glucose ring or an isocyanul ring is preferably mentioned.
Examples of the compound having a glucose ring include the above-mentioned cellulose compounds.
Examples of the compound having an isocyanul ring include the above-mentioned tris (2-hydroxyethyl) isocyanurate and the like.
Examples of the compound having an aromatic ring include the above-mentioned toluene sulfonic acid and benzene sulfonic acid.
Examples of the compound having an aliphatic ring include the above-mentioned alkyl sulfuric acid, such as a compound having a ring structure in an alkyl group.

Further, the compound having a cyclic structure preferably has a hydroxy group.
Preferred examples of the compound having a hydroxy group and having a cyclic structure include the above-mentioned cellulose compound and the above-mentioned tris (2-hydroxyethyl) isocyanate.

-Onium compound-
Further, the specific development accelerator is preferably an onium compound.
Examples of the onium compound include an ammonium compound and a sulfonium compound, and an ammonium compound is preferable.
Examples of the specific development accelerator which is an onium compound include trimethylglycine and the like.
Further, the onium compound in the electron-accepting polymerization initiator described later is a compound in which the value of the polar term of the SP value is not 6.0 to 26.0, and is not included in the specific development accelerator.

-Combination-
The image recording layer may contain one type of specific development accelerator alone, or two or more types may be used in combination.
One of the preferred embodiments of the image recording layer used in the present disclosure is an embodiment containing two or more compounds as a specific development accelerator.
Specifically, the image recording layer used in the present disclosure is a above-mentioned polyol compound, the above-mentioned betaine compound, the above-mentioned betaine compound, and the above-mentioned organic sulfonic acid compound as a specific development accelerator from the viewpoint of on-machine developability and carving property. Or, it is preferable to contain the above-mentioned polyol compound and the above-mentioned organic sulfonic acid compound.

-Content-
The content of the specific development accelerator with respect to the total mass of the image recording layer is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and 1% by mass or more. More preferably, it is 10% by mass or less.

[Specific binder polymer]
The image recording layer used in the present disclosure contains a specific binder polymer.
In the present disclosure, the specific binder polymer is a binder resin having no particle shape, and the polymer particles described later are not included in the specific binder polymer in the present disclosure.
The specific binder polymer has a structural unit formed of an aromatic vinyl compound and a structural unit formed of an acrylonitrile compound.

-Constituent units formed by aromatic vinyl compounds-
The specific binder polymer has a structural unit formed of an aromatic vinyl compound.
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. Styrene is preferred.
Examples of the vinylnaphthalene compound include 1-vinylnaphthalene, methyl-1-vinylnaphthalene, β-methyl-1-vinylnaphthalene, 4-methyl-1-vinylnaphthalene, 4-methoxy-1-vinylnaphthalene and the like. -Vinyl naphthalene is preferred.

Further, as the structural unit formed of the aromatic vinyl compound, the structural unit represented by the following formula A1 is preferably mentioned.

In the formula ^A1 , ^{RA1, RA2 and RA2'independently represent} a hydrogen atom or an alkyl group, Ar represents an aromatic ring group, ^RA3 represents a substituent, and n is equal to or less than the maximum number of substituents of Ar. Represents an integer of.
In the formula ^A1 , RA1, ^{RA2 and RA2'are each} independently preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and all of them are hydrogen. It is more preferably an atom.
In the formula A1, Ar is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring.
In the formula ^A1 , RA3 is preferably an alkyl group or an alkoxy group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and it is a methyl group or a methoxy group. Is more preferable.
When a plurality of ^RA3s are present in the formula A1, the plurality of ^RA3s may be the same or different from each other.
In the formula A1, n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

The content of the structural unit formed by the aromatic vinyl compound in the specific binder polymer is preferably 1% by mass to 80% by mass, preferably 5% by mass to 60% by mass, based on the total mass of the specific binder polymer. It is more preferable to have.

-Constituent units formed by acrylonitrile compounds-
The specific binder polymer has a structural unit formed of an acrylonitrile compound.
Examples of the acrylonitrile compound include (meth) acrylonitrile, and acrylonitrile is preferable.

Further, as the structural unit formed by the acrylonitrile compound, the structural unit represented by the following formula B1 is preferably mentioned.

In formula ^B1 , RB1 represents a hydrogen atom or an alkyl group.
In the formula ^B1 , RB1 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

The content of the structural unit formed by the acrylonitrile compound in the specific binder polymer is preferably 1% by mass to 80% by mass, preferably 5% by mass to 60% by mass, based on the total mass of the specific binder polymer. Is more preferable.

-Constituent unit formed by N-vinyl heterocyclic compound-
From the viewpoint of printing resistance and chemical resistance, the specific binder polymer 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.

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

In the formula C1, Ar ^N represents a heterocyclic structure containing a nitrogen atom, and the nitrogen atom in Ar ^N is bonded to the carbon atom indicated by *.
In the formula C1, the heterocyclic structure represented by Ar ^N is preferably a pyrrolidone ring, a carbazole ring, a pyrrole ring, a phenothiazine ring, a succinimide ring, a phthalimide ring, a caprolactam ring, and an imidazolid ring, and is preferably a pyrrolidone ring. Is more preferable.
Further, the heterocyclic structure represented by Ar ^N may have a known substituent.

The content of the structural unit formed by the N-vinyl heterocyclic compound in the specific binder polymer is preferably 1% by mass to 80% by mass, and 5% by mass to 60% by mass, based on the total mass of the specific binder polymer. % Is more preferable.

-Constituent unit having an ethylenically unsaturated group-
The specific binder polymer may further have a structural unit having an ethylenically unsaturated group.
The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth) acrylamide group, a (meth) acryloyloxy group, and the like, and from the viewpoint of reactivity, (meth). ) It is preferably an acrylamide group.
The structural unit having an ethylenically unsaturated group can be introduced into a specific binder polymer by a polymer reaction or copolymerization. Specifically, for example, a method of reacting a polymer having a structural unit having a carboxy group such as methacrylic acid with a compound having an epoxy group and an ethylenically unsaturated group (for example, glycidyl methacrylate), a hydroxy group. It can be introduced by a method of reacting a polymer having a structural unit having a group having an active hydrogen such as, etc. with a compound having an isocyanate group and an ethylenically unsaturated group (2-isocyanatoethyl methacrylate, etc.). ..
Further, the structural unit having an ethylenically unsaturated group is such that a polymer having an epoxy group such as glycidyl (meth) acrylate is reacted with a compound having a carboxy group and an ethylenically unsaturated group. It may be introduced into a specific binder polymer by a method.
Further, the structural unit having an ethylenically unsaturated group may be introduced into the specific binder polymer by using a monomer containing a partial structure represented by the following formula d1 or the following formula d2, for example. Specifically, for example, after polymerization using at least the above-mentioned monomer, an ethylenically unsaturated group is formed by a desorption reaction using a basic compound with respect to the partial structure represented by the following formula d1 or the following formula d2. By doing so, a structural unit having an ethylenically unsaturated group is introduced into the specific binder polymer.

In formulas d1 and d2, ^{R d} represents a hydrogen atom or an alkyl group, ^{Ad represents a halogen atom, X d represents} -O- or -NR ^N- , and RN represents a hydrogen atom or an alkyl group. , * Represent the binding site with other structures.
In formulas d1 and d2, R ^d is preferably a hydrogen atom or a methyl group.
In the formulas d1 and ^d2 , Ad is preferably a chlorine atom, a bromine atom, or an iodine atom.
In the formulas d1 and d2, X ^d is preferably —O—. When X ^d represents −NR ^N− , ^RN is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and more preferably a hydrogen atom.

Examples of the structural unit having an ethylenically unsaturated group include a structural unit represented by the following formula D1.

In formula D1, L ^D1 represents a single-bonded or divalent linking group, L ^D2 represents an m + 1 valent linking group, and X ^D1 and X ^D2 independently represent -O- or -NR ^N- , respectively. ^RN represents a hydrogen atom or an alkyl group, ^RD1 and ^RD2 independently represent a hydrogen atom or a methyl group, and m represents an integer of 1 or more.

In the formula ^D1 , LD1 is preferably a single bond. When ^LD1 represents a divalent linking group, an alkylene group, an arylene group or a divalent group to which two or more of these are bonded is preferable, and an alkylene group or a phenylene group having 2 to 10 carbon atoms is more preferable.
In the formula D1, L ^D2 is preferably a group represented by any of the following formulas D2 to the following formula D6.
In the formula D1, it is preferable that both X ^D1 and X ^D2 are —O—. Further, when at least one of X ^D1 and X ^{D 2} represents −NR ^N −, the ^RN is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and a hydrogen atom is more preferable.
In the formula ^D1 , RD1 is preferably a methyl group.
In the formula D1, it is preferable that at least one of the m ^RD2s is a methyl group.
In the formula D1, m is preferably an integer of 1 to 4, more preferably 1 or 2, and even more preferably 1.

In the formulas D2 to D6, L ^D3 to L ^D7 represent a divalent linking group, L ^D5 and L ^D6 may be different, and * represents a binding site with X ^D1 in the formula D1 and has a wavy line portion. Represents the binding site with X ^D2 in the formula D1.

In the formula ^D3 , LD3 is preferably an alkylene group, an arylene group, or a group in which two or more of these are bonded, and an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group in which two or more of these are bonded. More preferred.
In the formula ^D4 , LD4 is preferably an alkylene group, an arylene group, or a group in which two or more of these are bonded, and an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group in which two or more of these are bonded. More preferred.
In the formula ^D5 , LD5 is preferably an alkylene group, an arylene group, or a group in which two or more of these are bonded, and an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group in which two or more of these are bonded. More preferred.
In the formula D5, ^LD6 is preferably an alkylene group, an arylene group, or a group in which two or more of them are bonded, and an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group in which two or more of these are bonded. More preferred.
In the formula ^D6 , LD7 is preferably an alkylene group, an arylene group, or a group in which two or more of these are bonded, and an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group in which two or more of these are bonded. More preferred.

Specific examples of the structural unit having an ethylenically unsaturated group are shown below, but the structural unit having an ethylenically unsaturated group contained in the binder polymer according to the present disclosure is not limited thereto. In the following specific examples, R independently represents a hydrogen atom or a methyl group.

The content of the structural unit having an ethylenically unsaturated group in the specific binder polymer is preferably 1% by mass to 80% by mass, and 5% by mass to 60% by mass, based on the total mass of the specific binder polymer. Is more preferable.

-Constituent unit having an acidic group-
The specific binder polymer may contain a structural unit having an acidic group, but from the viewpoint of on-machine developability and ink inking property, it is preferable not to contain a structural unit having an acidic group.
Specifically, the content of the structural unit having an acidic group in the specific binder polymer is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% 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 specific binder polymer is preferably 20 mgKOH / g or less, more preferably 50 mgKOH / g or less, and even more preferably 100 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 K0070: 1992.

-Constituent unit with hydrophobic group-
The specific binder polymer 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 alkyl group in the alkyl (meth) acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched, and may have a cyclic structure. Examples of the alkyl (meth) acrylate compound include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. Can be mentioned.
The aryl group in the aryl (meth) acrylate compound preferably has 6 to 20 carbon atoms, and more preferably a phenyl group. Further, the aryl group may have a known substituent. As the aryl (meth) acrylate compound, phenyl (meth) acrylate is preferably mentioned.
The alkyl group in the aralkyl (meth) acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched, and may have a cyclic structure. The aryl group in the aralkyl (meth) acrylate compound preferably has 6 to 20 carbon atoms, more preferably a phenyl group. Benzyl (meth) acrylate is preferably mentioned as the aralkyl (meth) acrylate compound.

The content of the structural unit having a hydrophobic group in the specific binder polymer is preferably 1% by mass to 80% by mass, and preferably 5% by mass to 60% by mass, based on the total mass of the specific binder polymer. More preferred.

-Constituent unit having a hydrophilic group-
The specific binder polymer may contain a structural unit having a hydrophilic group from the viewpoint of improving printing resistance, chemical resistance and on-machine developability.
As the hydrophilic group, -OH, -CN, -CONR ¹ R ² , -NR ² COR ¹ (R ¹ , R ² independently represent a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, respectively. R ¹ and R ² may be combined to form a ring.)-NR ³ R ⁴ , -N ⁺ R ³ R ⁴ R ⁵ X- ⁽ R ³ to R ⁵ each have an independent number of carbon atoms. (Representing an alkyl group of 1 to 8 and X ^- representing a counter anion), a group represented by the following formula PO, and the like can be mentioned.
Among these hydrophilic groups, the group represented by -CONR ¹ R ² or the formula PO is preferable, and the group represented by the formula PO is more preferable.

In the formula PO, ^LP independently represents an alkylene group, ^RP represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 100.
In the formula PO, LP is preferably an ethylene group, a 1-methylethylene group or a 2 ^- methylethylene group independently, and more preferably an ethylene group.
In the formula PO, ^RP is preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 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 in the specific binder polymer is preferably 1% by mass to 80% by mass, and preferably 5% by mass to 60% by mass, based on the total mass of the specific binder polymer. More preferred.

-Other building blocks-
The specific binder polymer 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.
Examples of the acrylamide compound include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-butyl (meth) acrylamide, and N, N'-dimethyl. Examples thereof include (meth) acrylamide, N, N'-diethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxypropyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide and the like.
Examples of the vinyl ether compound include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether and 4-methylcyclohexyl. Methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydroflu Frill vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, Examples thereof include phenylethyl vinyl ether and phenoxypolyethylene glycol vinyl ether.

The content of the other structural units in the specific binder polymer is preferably 0.5% by mass to 50% by mass, more preferably 1% by mass to 30% by mass, based on the total mass of the specific binder polymer. preferable.

-Manufacturing method of specific binder polymer-
The method for producing the specific binder polymer is not particularly limited, and the specific binder polymer can be produced by a known method.
For example, an aromatic vinyl compound, an acrylonitrile compound, an N-vinyl heterocyclic compound as required, a compound used for forming a structural unit having an ethylenically unsaturated group, and a structural unit having an acidic group. At least one compound selected from the group consisting of the compound used in the above, the compound used for forming the structural unit having the hydrophobic group, and the compound used for forming the other structural unit. It is obtained by polymerizing by the method of.

-Molecular weight-
The weight average molecular weight of the specific binder polymer is preferably 3,000 to 300,000, more preferably 5,000 to 100,000.

-Concrete example-
Specific examples of the specific binder polymer are shown in the table below, but the specific binder polymer used in the present disclosure is not limited thereto.

In the above specific example, for example, the description of "40/30/10/20" in P1-4 is the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit from the left. Represents the content ratio (mass ratio) of each.
Further, in the above specific example, the content ratio of each structural unit can be appropriately changed according to the preferable range of the content of each of the above-mentioned structural units.
Further, the weight average molecular weight of each compound shown in the above specific example can be appropriately changed according to a preferable range of the weight average molecular weight of the above-mentioned specific binder polymer.

-Content-
The image recording layer may contain one type of specific binder polymer alone, or two or more types may be used in combination.
The content of the specific binder polymer with respect to the total mass of the image recording layer is preferably 5% by mass or more and 95% by mass or less, more preferably 7% by mass or more and 80% by mass or less, and 10% by mass or more and 60% by mass or less. More preferred.

[Electron-donated polymerization initiator]
The image recording layer used in the present disclosure preferably contains an electron donating type polymerization initiator. The electron donating type polymerization initiator is considered to contribute to the improvement of chemical resistance and printing resistance in the lithographic printing plate. Examples of the electron donating type polymerization initiator include the following five types.
(I) Alkyl or arylate complex: It is considered that the carbon-heterobond is oxidatively cleaved to generate an active radical. Specific examples thereof include borate compounds.
(Ii) Aminoacetic acid compound: It is considered that the CX bond on the carbon adjacent to nitrogen is broken by oxidation to generate an active radical. As X, a hydrogen atom, a carboxy group, a trimethylsilyl group or a benzyl group is preferable. Specific examples thereof include N-phenylglycines (may have a substituent on the phenyl group), N-phenyliminodiacetic acid (may have a substituent on the phenyl group) and the like. Be done.
(Iii) Sulfur-containing compound: The above-mentioned aminoacetic acid compound in which the nitrogen atom is replaced with a sulfur atom can generate an active radical by the same action. Specific examples thereof include phenylthioacetic acid (which may have a substituent on the phenyl group) and the like.
(Iv) Tin-containing compound: The above-mentioned aminoacetic acid compound in which the nitrogen atom is replaced with a tin atom can generate an active radical by the same action.
(V) Sulfinates: Oxidation can generate active radicals. Specific examples thereof include sodium arylsulfinate and the like.

Among these electron donating type polymerization initiators, the image recording layer preferably contains a borate compound. As the borate compound, a tetraarylborate compound or a monoalkyltriarylborate compound is preferable, a tetraarylborate compound is more preferable, and a tetraphenylborate compound is particularly preferable from the viewpoint of compound stability.
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.

Specific examples of the borate compound include sodium tetraphenylborate.

B-1 to B-8 are shown below as preferred 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, Bu represents an n-butyl group and Z represents a counter cation.
Examples of the counter cation represented by Z include Na ⁺ , K ⁺ , N ⁺ (Bu) ₄ , and the like. The above Bu represents an n-butyl group.
Further, as the counter cation represented by Z, onium ion in the electron-accepting polymerization initiator described later is also preferably mentioned.

As the electron donating type polymerization initiator, only one kind may be added, 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, more preferably 0.05% by mass to 25% by mass, and 0.1% by mass with respect to the total mass of the image recording layer. It is more preferably to 20% by mass.

[Polymerizable compound]
The image recording layer in the present disclosure preferably contains a polymerizable compound.
In the present disclosure, even if the compound has polymerizable property, the compound corresponding to the above-mentioned specific binder polymer, the polymer particles described later, and the binder polymer other than the specific binder polymer described later does not correspond to the polymerizable compound. And.
The molecular weight (weight average molecular weight when having a molecular weight distribution) of the polymerizable compound is preferably 50 or more and less than 2,500, and more preferably 50 or more and 2,000 or less.
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.

Examples of the monomer include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), esters thereof, and amides thereof, and unsaturated carboxylic acids are preferable. Esters of acid and polyhydric alcohol compound, and amides of unsaturated carboxylic acid and polyhydric amine compound are used. Further, an addition reaction product of an unsaturated carboxylic acid ester or amide having a nucleophilic substituent such as a hydroxy group, an amino group or a mercapto group with a monofunctional or polyfunctional isocyanate or an epoxy, and a monofunctional or polyfunctional group. A dehydration condensation reaction product with a functional carboxylic acid is also preferably used. Further, an addition reaction product of unsaturated carboxylic acid esters or amides having a polyelectron substituent such as an isocyanate group or an epoxy group with monofunctional or polyfunctional alcohols, amines and thiols, and a halogen atom. Substitutable compounds of unsaturated carboxylic acid esters or amides having a desorbing substituent such as a tosyloxy group with monofunctional or polyfunctional alcohols, amines and thiols are also suitable. Further, as another example, it is also possible to use a compound group in which the above unsaturated carboxylic acid is replaced with unsaturated phosphonic acid, styrene, vinyl ether or the like. These are JP-A-2006-508380, JP-A-2002-287344, JP-A-2008-256850, JP-A-2001-342222, JP-A-9-179296, JP-A-9-179297. , JP-A-9-179298, JP-A-2004-294935, JP-A-2006-243493, JP-A-2002-275129, JP-A-2003-64130, JP-A-2003-280187, Special Publication. It is described in Kaihei 10-333321A.

Specific examples of the monomer of the ester of the polyhydric alcohol compound and the unsaturated carboxylic acid include ethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethylene glycol diacrylate, and propylene glycol diacrylate, as acrylic acid esters. Examples thereof include trimethylolpropane triacrylate, hexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate, isocyanuric acid ethylene oxide (EO) modified triacrylate, and polyester acrylate oligomer. As methacrylic acid ester, tetramethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropanetrimethacrylate, ethylene glycol dimethacrylate, pentaerythritol trimethacrylate, bis [p- (3-methacryloxy-2-hydroxypropoxy) phenyl]. Examples thereof include dimethylmethane and bis [p- (methacrylicoxyethoxy) phenyl] dimethylmethane. Specific examples of the amide monomer of the polyvalent amine compound and the unsaturated carboxylic acid include methylenebisacrylamide, methylenebismethacrylamide, 1,6-hexamethylenebisacrylamide, and 1,6-hexamethylenebismethacrylate. Examples thereof include diethylenetriaminetrisacrylamide, xylylenebisacrylamide, and xylylenebismethacrylamide.

Further, a urethane-based addition-polymerizable compound produced by using an addition reaction of isocyanate and a hydroxy group is also suitable, and specific examples thereof are, for example, 2 in 1 molecule described in Japanese Patent Publication No. 48-41708. A vinyl urethane compound containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxy group represented by the following formula (M) to a polyisocyanate compound having two or more isocyanate groups. And so on.
CH ₂ = C (RM4) COOCH ₂ CH ( ^RM5 ) OH ( ^M )
In formula ( ^M ), RM4 and ^RM5 each independently represent a hydrogen atom or a methyl group.

Further, urethane acrylates described in JP-A-51-37193, JP-A-2-32293, JP-A-2-16765, JP-A-2003-344997, JP-A-2006-65210, and Japanese Patent Publication No. The ethylene described in Japanese Patent Application Laid-Open No. 58-49860, Japanese Patent Publication No. 56-17654, Japanese Patent Publication No. 62-39417, Japanese Patent Application Laid-Open No. 62-39418, Japanese Patent Application Laid-Open No. 2000-250211, and Japanese Patent Application Laid-Open No. 2007-94138. Urethane compounds having an oxide-based skeleton, urethane compounds having a hydrophilic group described in US Pat. No. 7,153,632, JP-A-8-505598, JP-A-2007-293221, JP-A-2007-293223. Kind is also suitable.

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.
The content of the polymerizable compound is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 70% by mass, and 15% by mass to 60% by mass with respect to the total mass of the image recording layer. It is more preferably by mass%.
Further, the content of the specific binder polymer in the image recording layer with respect to the total mass of the polymerizable compound is preferably more than 0% by mass and 400% by mass or less, and preferably 25% by mass to 300% by mass. More preferably, it is more preferably 50% by mass to 200% by mass.
In the image recording layer, it is preferable that the specific binder polymer and the above-mentioned polymerizable compound have a sea-island structure. For example, a structure in which the polymerizable compound is dispersed in an island shape (discontinuous layer) in the sea (continuous phase) of the specific binder polymer can be adopted. It is considered that the sea-island structure is easily formed by setting the content of the specific binder polymer with respect to the total mass of the polymerizable compound to a value within the above range.

[Electron-accepting polymerization initiator]
The image recording layer preferably contains an electron-accepting polymerization initiator.
The electron-accepting polymerization initiator used in the present disclosure is a compound that generates a polymerization initiator such as a radical or a cation by the energy of light, heat, or both, and is a known thermal polymerization initiator and has a small bond dissociation energy. A compound having a bond, a photopolymerization initiator and the like can be appropriately selected and used.
As the electron-accepting polymerization initiator, a radical polymerization initiator is preferable, and an onium compound is more preferable.
Further, the electron-accepting polymerization initiator is preferably an infrared photosensitive polymerization initiator.
The electron-accepting polymerization initiator may be used alone or in combination of two or more.
Examples of the radical polymerization initiator include (a) an organic halide, (b) a carbonyl compound, (c) an azo compound, (d) an organic peroxide, (e) a metallocene compound, and (f) an azide compound. ) Hexaaryl biimidazole compound, (i) disulfone compound, (j) oxime ester compound, (k) onium compound.

(A) As the organic halide, for example, the compounds described in paragraphs 0022 to 0023 of JP-A-2008-195018 are preferable.
(B) As the carbonyl compound, for example, the compound described in paragraph 0024 of JP-A-2008-195018 is preferable.
(C) As the azo compound, for example, the azo compound described in JP-A-8-108621 can be used.
(D) As the organic peroxide, for example, the compound described in paragraph 0025 of JP-A-2008-195018 is preferable.
(E) As the metallocene compound, for example, the compound described in paragraph 0026 of JP-A-2008-195018 is preferable.
Examples of the (f) azide compound include compounds such as 2,6-bis (4-azidobenzylidene) -4-methylcyclohexanone.
(G) As the hexaarylbiimidazole compound, for example, the compound described in paragraph 0027 of JP-A-2008-195018 is preferable.
(I) Examples of the disulfone compound include the compounds described in JP-A-61-166544 and JP-A-2002-328465.
(J) As the oxime ester compound, for example, the compounds described in paragraphs 0028 to 0030 of JP-A-2008-195018 are preferable.

Among the electron-accepting polymerization initiators, oxime ester compounds and onium compounds are preferable from the viewpoint of curability. 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 further 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.

As an example of the sulfonium salt compound, a triarylsulfonium salt compound is preferable, and an electron-attracting group, for example, a triarylsulfonium salt compound in which at least a part of a group on an aromatic ring is substituted with a halogen atom is preferable, and an aromatic is preferable. A triarylsulfonium salt compound having a total number of substitutions of 4 or more halogen atoms on the ring is more preferable. Specific examples include triphenylsulfonium = hexafluorophosphate, triphenylsulfonium = benzoylformate, bis (4-chlorophenyl) phenylsulfonium = benzoylformate, and bis (4-chlorophenyl) -4-methylphenylsulfonium = tetrafluoro. Borat, Tris (4-chlorophenyl) Sulfonium = 3,5-bis (methoxycarbonyl) Benzene Sulfonium, Tris (4-chlorophenyl) Sulfonium = Hexafluorophosphate, Tris (2,4-dichlorophenyl) Sulfonium = Hexafluorophos Fert is mentioned.

Further, as the counter anion of the iodonium salt compound and the sulfonium salt compound, a sulfonamide anion or a sulfonimide anion is preferable, and a sulfonamide anion is 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 are shown below, but the present disclosure is not limited thereto. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group.

Further, one of the preferred embodiments in the present disclosure is an embodiment in which the electron-accepting polymerization initiator and the electron-donating polymerization initiator form a salt.
Specifically, for example, an embodiment in which the onium compound is a salt of an onium ion and an anion (for example, a tetraphenylborate anion) in the electron donating type polymerization initiator can be mentioned. Further, more preferably, an iodonium borate compound in which an iodonium cation (for example, dip-tolyl iodonium cation) in the iodonium salt compound described later and a borate anion in the above-mentioned electron donating polymerization initiator form a salt is mentioned. Be done.
In the present disclosure, when the image recording layer contains onium ions and anions in the above-mentioned electron donating type polymerization initiator, the image recording layer shall contain an electron accepting type polymerization initiator and an electron donating type polymerization initiator.

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. It is preferably 0.8% by mass to 20% by mass, and particularly preferably 0.8% by mass.

[Infrared absorber]
The image recording layer preferably contains an infrared absorber. Examples of the infrared absorber 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 "Handbook of Dyes" (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, particularly preferable ones include cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indorenin cyanine dyes. Further, cyanine pigments and indorenin cyanine pigments can be mentioned. Of these, the cyanine pigment is particularly preferable.

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 the compounds described in 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, it is preferable that the infrared absorber is an infrared absorber that decomposes by infrared exposure (hereinafter, also referred to as "degradable infrared absorber").
By using an infrared absorber that decomposes by infrared exposure as the infrared absorber, the infrared absorber or its decomposition product promotes polymerization, and by using a specific binder polymer, a highly polar film can be obtained. Further, the decomposition product of the infrared absorber and the binder polymer interact with each other to have excellent printing resistance and printing resistance (UV printing resistance) even when UV ink is used. It is estimated that.
The degradable infrared absorber is preferably an infrared absorber having a function of absorbing, decomposing, and developing a color of infrared rays by infrared exposure. Here, "color development" means that there is almost no absorption in the visible light region (wavelength region of 400 nm or more and less than 750 nm) before infrared exposure, but absorption occurs in the visible light region by infrared exposure, and the visible light region. It also includes the fact that absorption in the lower wavelength region has a longer wavelength in the visible light region.
Hereinafter, the color-developed compound formed by the decomposable infrared absorber absorbing infrared rays by infrared exposure and decomposing the compound is also referred to as a "color former of the decomposable infrared absorber".
Further, it is preferable that the decomposable infrared absorber has a function of absorbing infrared rays by infrared exposure and converting the absorbed infrared rays into heat.
The degradable infrared absorber may be any as long as it absorbs and decomposes at least one part of light in the infrared wavelength range (wavelength 750 nm to 1 mm), but infrared rays having maximum absorption in the wavelength range of 750 nm to 1,400 nm. It is preferably an absorbent.

The degradable infrared absorber is preferably an infrared absorber that decomposes due to heat, electron transfer, or both caused by infrared exposure, and more preferably an infrared absorber that decomposes due to electron transfer caused by infrared exposure. preferable. Here, "decomposed by electron transfer" means that the electrons excited from the HOMO (highest occupied orbital) of the degradable infrared absorber to the LUMO (lowest empty orbital) by infrared exposure are the electron accepting groups (LUMO) in the molecule. It means that the electron transfers in the molecule to a group whose potential is close to that of the group, and the decomposition occurs accordingly.

As the degradable infrared absorber, a cyanine dye that decomposes by infrared exposure is preferable from the viewpoint of color development and UV printing resistance of the obtained lithographic printing plate.
The infrared absorber is more preferably a compound represented by the following formula 1 from the viewpoint of color development and UV printing resistance of the obtained lithographic printing plate.

In Equation 1, R ¹ represents a group in which the R ¹ -L bond is cleaved by infrared exposure, and R ₁₁ to R ₁₈ independently contain a hydrogen atom, a halogen atom, -Ra, -ORb, -SRc or -NRdRe. Ra to Re each independently represent a hydrocarbon group, and A ₁ , A ₂ and a plurality of R ₁₁ to R ₁₈ may be linked to form a single ring or a poly ring, and A ₁ and A ₂ may be formed. Independently represent an oxygen atom, a sulfur atom or a nitrogen atom, and n ₁₁ and n ₁₂ each independently represent an integer of 0 to 5, where the sum of n ₁₁ and n ₁₂ is 2 or more and n. ₁₃ and n ₁₄ independently represent 0 or 1, L represents an oxygen atom, a sulfur atom or -NR ^10- , R ¹⁰ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a charge neutralizing. Represents a counter ion.

When the cyanine dye represented by the formula 1 is exposed to infrared rays, the R1 ^- L bond is cleaved, L becomes = O, = S or = NR ¹⁰ , and the color former of the degradable infrared absorber is developed. Is formed. R ¹ is detached to form a radical or ionic body. These contribute to the polymerization of the polymerizable compound contained in the image recording layer.

In formula 1, R ₁₁ to R ₁₈ are preferably hydrogen atoms, -Ra, -ORb, -SRc or -NRdRe, respectively.
The hydrocarbon group in Ra to Re is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably a hydrocarbon group having 1 to 15 carbon atoms, and further preferably a hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group may be linear, may have a branch, or may have a ring structure.

Independently, R ₁₁ to R ₁₄ in the formula 1 are preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group, and even more preferably a hydrogen atom.
Further, 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 formed ring is preferably a 5-membered ring or a 6-membered ring, and more preferably a 5-membered ring.
It is preferable that R ₁₂ bonded to the carbon atom to which A ₁ ⁺ is bonded and R ₁₄ bonded to the carbon atom to which A ₂ is bonded are linked to R ₁₅ and R ₁₇ , respectively, to form a ring.

R15 in Formula ₁ is preferably a hydrocarbon group. Further, it is preferable that R ₁₅ and R ₁₂ bonded to the carbon atom to which A ₁ ⁺ is bonded are linked 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 color development.
R ₁₇ in Formula 1 is preferably a hydrocarbon group. Further, it is preferable that R ₁₇ and R ₁₄ bonded to the carbon atom to which A ₂ is bonded are linked 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 color development.
It is preferable that R ₁₅ and R ₁₇ in the formula 1 have the same group, and when each forms a ring, it is preferable to form the same ring.

It is preferable that R ₁₆ and R ₁₈ in the formula 1 are the same group.
Further, from the viewpoint of improving the water solubility of the compound represented by the formula 1, R ₁₆ and R ₁₈ are preferably an alkyl group having a (poly) oxyalkylene group or an alkyl group having an anionic structure, respectively, preferably alkoxyalkyl. An alkyl group having a group, a carboxylate group or a sulfonate group is more preferable, and an alkyl group having a sulfonate group at the terminal is further preferable. As the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkyl group having 1 to 4 carbon atoms is more preferable.
The counter cation of the anion structure may be a cation that can be contained in ^R1 −L in the formula ^{1 or A 1+} _, or may be an alkali metal cation or an alkaline earth metal cation.
The counter cation of the sulfonate group may be a cation that can be contained in ^R1 −L in the formula ^{1 or A 1+} _, or may be an alkali metal cation or an alkaline earth metal cation.
Further, the maximum absorption wavelength of the compound represented by the formula 1 is lengthened, and from the viewpoint of color development and printing resistance in the lithographic printing plate, R ₁₆ and R ₁₈ independently have an alkyl group or an aromatic ring, respectively. Alkyl groups having are preferable. As the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable, an alkyl group having 1 to 4 carbon atoms is more preferable, and a methyl group or an ethyl group is further preferable. As the alkyl group having an aromatic ring, an alkyl group having an aromatic ring at the terminal is preferable, and a 2-phenylethyl group, a 2-naphthalenylethyl group or a 2- (9-anthrasenyl) ethyl group is more preferable.

For n ₁₁ and n ₁₂ in the formula 1, the same integers of 0 to 5 are preferable, integers of 1 to 3 are more preferable, 1 or 2 is more preferable, and 2 is particularly preferable.

A ₁ and A ₂ in the formula 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 are the same atom.

Za in Equation 1 represents a counterion that neutralizes the charge. Examples of the anion species include sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroantimonate ion, p-toluenesulfonate ion, perchlorate ion and the like, and hexafluoroantimonic acid. Ions or hexafluorophosphate ions are preferred. Examples of the cation species include alkali metal ions, alkaline earth metal ions, ammonium ions, pyridinium ions, sulfonium ions and the like, and sodium ions, potassium ions, ammonium ions, pyridinium ions or sulfonium ions are preferable. More preferably, potassium ion or ammonium ion.
R ₁₁ to R ₁₈ and R ¹ to L may have an anionic structure or a cationic structure, and if all of R ₁₁ to R ₁₈ and R ¹ to L are charge-neutral groups, Za Is a monovalent counter anion, but Za can also be a counter cation, for example, if R ₁₁ to R ₁₈ and R ^1-1 have two or more anion structures.
Further, if the cyanine dye represented by the formula 1 has a charge-neutral structure in the whole compound, Za does not exist.

In formula 1, the group in which the ^R1 -L bond is cleaved by infrared exposure represented by ^R1 will be described in detail later.

As the degradable infrared absorber, a cyanine dye represented by the following formula 1-A is more preferable from the viewpoint of color development and UV printing resistance of the obtained lithographic printing plate.

In formula 1-A, R ¹ represents a group whose ^R1 -L bond is cleaved by infrared exposure, R ² and R ³ each independently represent a hydrogen atom or an alkyl group, and R ² and R ³ are linked to each other. Ar ¹ and Ar ² each independently represent a group forming a benzene ring or a naphthalene ring, and Y ¹ and Y ² independently represent an oxygen atom, a sulfur atom, and -NR. ⁰ -or a dialkylmethylene group, R ⁰ represents a hydrogen atom, an alkyl group or an aryl group, and R ⁴ and R ⁵ independently represent an alkyl group, -CO ₂ M group or -PO ₃ M ₂ group, respectively. , M represent a hydrogen atom, a Na atom, a K atom or an onium group, R ⁶ to R ⁹ independently represent a hydrogen atom or an alkyl group, and L represents an oxygen atom, a sulfur atom or -NR ^10- . R ¹⁰ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counterion that neutralizes the charge.

^In formula 1-A, the alkyl group in ^R2 to R9 and ^R0 is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and an alkyl group having 1 to 10 carbon atoms. Is more 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 Examples include a group and a 2-norbornyl group.
Among the 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 Examples thereof include a group combining these.

The aryl group at ^R0 is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms.
The aryl group may have a substituent. Examples of substituents are an alkyl group, 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 and an aryloxycarbonyl group. , And a group combining these.
Specifically, for example, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, p-fluorophenyl group, p-methoxyphenyl group, p-dimethylaminophenyl group, p-methylthiophenyl group, p- Phenylthiophenyl group and the like can be mentioned.
Among the aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group or a naphthyl group is preferable.

It is preferable that R ² and R ³ are connected to form a ring.
When R ² and R ³ are connected to form a ring, a 5-membered ring or a 6-membered ring is preferable, and a 5-membered ring is particularly preferable.

Y ¹ and Y ² independently represent an oxygen atom, a sulfur atom, an −NR ⁰ − or a dialkyl methylene group, preferably an −NR ⁰ − or a dialkyl methylene group, and more preferably a dialkyl methylene group.
^R0 represents a hydrogen atom, an alkyl group or an aryl group, and an alkyl group is preferable.

The alkyl group represented by R ⁴ or R ⁵ may be a substituted alkyl. ^Examples of the substituted alkyl group represented by ^R4 or R5 include a group represented by any of the following formulas (a1) to (a4).

In formulas (a1) to (a4), RW0 represents an alkylene group having 2 to 6 carbon atoms, ^W represents a single bond or an oxygen atom, n _W1 represents an integer of 1 to 45, and ^RW1 represents carbon. Represents an alkyl group of number 1 to 12 or -C (= O) ^-RW5 , ^RW5 represents an alkyl group of 1 to 12 carbon atoms, and ^{RW2 to RW4 independently} represent a single bond or 1 carbon number. Represents an alkylene group of ~ 12, where M represents a hydrogen atom, a Na atom, a K 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 and an n-butylene group are 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, an n-butyl group, a tert-butyl group, and the like, preferably a methyl group and a tert-butyl group. An ethyl group is more preferable, and a methyl group is particularly preferable.
The alkyl group represented by ^RW5 is the same as the alkyl group represented by ^RW1 , and the preferred embodiment is also the same as the preferred embodiment of the alkyl group represented by ^RW1 .

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 groups 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, and ethylene group, n-propylene group, isopropylene group and n-butylene group are preferable. Ethylene groups and n-propylene groups are 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.

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

In formula 1-A, R ⁴ and R ⁵ are preferably unsubstituted alkyl groups, respectively. R ⁴ and R ⁵ are preferably the same group.

R ⁶ to R ⁹ independently represent a hydrogen atom or an alkyl group, and a hydrogen atom is preferable.
Ar ¹ and Ar ² each independently represent a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent. As the substituent, an alkyl group, 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 an acyloxy group. Examples thereof include a group, a phosphonic acid group, and a group combining these groups. As the substituent, an alkyl group is preferable.
Further, from the viewpoint of lengthening the maximum absorption wavelength of the compound represented by the formula 1-A and improving the color development property and the printing durability of the flat plate printing plate, Ar ¹ and Ar ² are independently naphthalene rings. , Or a group forming a benzene ring having an alkyl group or an alkoxy group as a substituent is preferable, and a naphthalene ring or a group forming a benzene ring having an alkoxy group as a substituent is more preferable, a naphthalene ring or a methoxy. A group forming a benzene ring having a group as a substituent is particularly preferable.

In formula 1-A, it is preferable that Ar ¹ or Ar ² is a group forming a group represented by the following formula (b1).

In formula (b1), R ¹⁹ represents an alkyl group having 1 to 12 carbon atoms. n3 represents an integer of 1 to 4. * Represents the binding site.

Za represents a counterion for neutralizing the charge. However, if the compound represented by the formula 1-A has a corresponding ionic substituent in its structure and charge neutralization is not required, Za is not required. When Za indicates an anionic species, sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, p-toluenesulfonate ion, perchlorate ion, hexafluoroantimonate ion and the like can be mentioned, and hexafluoro Phosphate ion or hexafluoroantimonate ion is preferable. When Za represents a cation species, examples thereof include alkali metal ion, alkaline earth metal ion, ammonium ion, pyridinium ion or sulfonium ion, and sodium ion, potassium ion, ammonium ion, pyridinium ion or sulfonium ion are preferable. Ions, potassium ions or ammonium ions are more preferred.
R ¹ to R ⁹ , R ⁰ , Ar ¹ , Ar ² , Y ¹ and Y ² may have an anionic structure or a cationic structure, and R ¹ to R ⁹ , R ⁰ , Ar ¹ , Ar ² , etc. If all of Y ¹ and Y ² are charge-neutral groups, Za is a monovalent counter anion, for example R ¹ to R ⁹ , R ⁰ , Ar ¹ , Ar ² , Y ¹ and. If Y ² has more than one anion structure, Za can also be a counter cation.

In the above formulas 1 and 1-A, the group in which the ^R1 -L bond is cleaved by infrared exposure represented by ^R1 will be described below.
When L is an oxygen atom in Formula 1 or Formula 1-A, R ¹ is preferably a group represented by any of the following formulas (1-1) to (1-7) from the viewpoint of color development. , The group represented by any of the following formulas (1-1) to (1-3) is more preferable.

In formulas (1-1) to (1-7), ● represents a bonding site with an oxygen atom represented by L in formula 1 or formula 1-A, and ^R20 is an independent hydrogen atom. Alkyl group, alkoxy group, aryl group, -OR ²⁴ , -NR ²⁵ R ²⁶ or -SR ²⁷ , R ²¹ independently represents a hydrogen atom, alkyl group or aryl group, R ²² represents an aryl group,- OR ²⁴ , -NR ²⁵ R ²⁶ , -SR ²⁷ , -C (= O) R ²⁸ , -OC (= O) R ²⁸ or a halogen atom, where R ²³ is an aryl group, an alkenyl group, an alkoxy group or an onium group. , R ²⁴ to R ²⁷ independently represent a hydrogen atom, an alkyl group or an aryl group, and R ²⁸ represents an alkyl group, an aryl group, -OR ²⁴ , -NR ²⁵ R ²⁶ or -SR ²⁷ , and Z. ¹ represents a counter ion for neutralizing the charge.

The preferred embodiment when R ²⁰ , R ²¹ and R ²⁴ to R ²⁸ are alkyl groups is the same as the preferred embodiment of the alkyl groups in R ² to R ⁹ and R ⁰ .
The carbon number of the alkenyl group in R ²⁰ and R ²³ is preferably 1 to 30, more preferably 1 to 15, and even more preferably 1 to 10.
The preferred embodiment when R ²⁰ to R ²⁸ are aryl groups is the same as the preferred embodiment of the aryl group in R ⁰ .

From the viewpoint of color development, the R ²⁰ in the formula (1-1) is preferably an alkyl group, an alkenyl group, an aryl group, -OR ²⁴ , -NR ²⁵ R ²⁶ or -SR ²⁷ , and an alkyl group, -OR ²⁴ ,-. NR ²⁵ R ²⁶ or -SR ²⁷ is more preferred, alkyl groups or -OR ²⁴ are even more preferred, and -OR ²⁴ is particularly preferred.
When R ²⁰ in the formula (1-1) is an alkyl group, the alkyl group may be an alkyl group having an arylthio group, an alkyloxycarbonyl group, or an arylsulfonyl group at the α-position, and may be an α-position. An alkyl group having an arylthio group or an alkyloxycarbonyl group is preferable.
When R ²⁰ in the formula (1-1) is −OR ²⁴ , the R ²⁴ is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, further preferably an isopropyl group or a tert-butyl group, and t. -Butyl groups are particularly preferred.
When R20 in the formula ⁽ 1-1) is an alkenyl group, the alkenyl group may be an aryl group or an alkenyl group having a hydroxyaryl group.

From the viewpoint of color development, hydrogen atom is preferable for R ²¹ in the formula (1-2).
Further, from the viewpoint of color development, R ²² in the formula (1-2) is preferably -C (= O) OR ²⁴ , -OC (= O) OR ²⁴ or a halogen atom, and is preferably -C (= O) OR ²⁴ . Alternatively, -OC (= O) OR ²⁴ is more preferable. When R ²² in the formula (1-2) is −C (= O) OR ²⁴ or —OC (= O) OR ²⁴ , R ²⁴ is preferably an alkyl group.

From the viewpoint of color development, R ²¹ in the formula (1-3) is preferably a hydrogen atom or an alkyl group independently, and at least one R ²¹ in the formula (1-3) is more preferably an alkyl group.
The alkyl group in R ²¹ is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 3 to 10 carbon atoms.
Further, the alkyl group in R ²¹ is preferably an alkyl group having a branched or ring structure, and more preferably an isopropyl group, a cyclopentyl group, a cyclohexyl group, or a tert-butyl group. Further, the alkyl group in R ²¹ is preferably a secondary or tertiary alkyl group.
Further, from the viewpoint of color development, R ²³ in the formula (1-3) is preferably an aryl group, an alkoxy group or an onium group, more preferably a p-dimethylaminophenyl group or a pyridinium group, and even more preferably a pyridinium group.
Examples of the onium group in R ²³ include a pyridinium group, an ammonium group, a sulfonium group and the like. The onium group may have a substituent. As the substituent, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a sulfo group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a combination thereof are used. Examples thereof include an alkyl group, an aryl group and a group in which these are combined.
Of these, a pyridinium group is preferable, and an N-alkyl-3-pyridinium group, an N-benzyl-3-pyridinium group, an N- (alkoxypolyalkyleneoxyalkyl) -3-pyridinium group, and an N-alkoxycarbonylmethyl-3-pyridinium group are preferable. , N-alkyl-4-pyridinium group, N-benzyl-4-pyridinium group, N- (alkoxypolyalkyleneoxyalkyl) -4-pyridinium group, N-alkoxycarbonylmethyl-4-pyridinium group, or N-alkyl -3,5-dimethyl-4-pyridinium group is more preferable, N-alkyl-3-pyridinium group or N-alkyl-4-pyridinium group is more preferable, N-methyl-3-pyridinium group, N-octyl. A -3-pyridinium group, an N-methyl-4-pyridinium group, or an N-octyl-4-pyridinium group is particularly preferable, and an N-octyl-3-pyridinium group or an N-octyl-4-pyridinium group is the most preferable. preferable.
When R ²³ is a pyridinium group, the counter anions include sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, p-toluene sulfonate ion, perchlorate ion, and hexafluoroantimonate ion. And the like, p-toluenesulfonate ion, hexafluoroantimonate ion or hexafluorophosphate ion is preferable.

From the viewpoint of color development, the R ²⁰ in the formula (1-4) is preferably an alkyl group or an aryl group, and of the two R ²⁰ , one is more preferably an alkyl group and the other is more preferably an aryl group. The above two R ^20s may be connected to form a ring.
From the viewpoint of color development, the R ²⁰ in the formula (1-5) is preferably an alkyl group or an aryl group, more preferably an aryl group, and even more preferably a p-methylphenyl group.
From the viewpoint of color development, R ²⁰ in the formula (1-6) is preferably an alkyl group or an aryl group, and more preferably a methyl group or a phenyl group, respectively.
From the viewpoint of color development, Z ¹ in the formula (1-7) may be any counterion for neutralizing the charge, and the compound as a whole may be contained in Za.
Z ¹ is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroantimonate ion, a p-toluenesulfonate ion, or a perchlorate ion, preferably a p-toluenesulfonate ion or a hexa. Fluoroantimonate ion or hexafluorophosphate ion is more preferable.

When L is an oxygen atom in Formula 1 or Formula 1-A, R ¹ is more preferably a group represented by the following formula (5) from the viewpoint of color development.

In formula (5), R ¹⁵ and R ¹⁶ independently represent a hydrogen atom, an alkyl group or an aryl group, E represents an onium group, and * is represented by formula 1 or L in formula 1-A. Represents a bond site with an oxygen atom.

The alkyl group represented by R ¹⁵ or R ¹⁶ is the same as the alkyl group in R ² to R ⁹ and R ⁰ , and the preferred embodiment is also the same as the preferred embodiment of the alkyl group in R ² to R ⁹ and R ⁰ . ..
The aryl group represented by R ¹⁵ or R ¹⁶ is the same as the aryl group in R ⁰ , and the preferred embodiment is also the same as the preferred embodiment of the aryl group in R ⁰ .
The onium group represented by E is the same as the onium group in R ²³ , and the preferred embodiment is also the same as the preferred embodiment of the onium group in R ²³ .

In the formula (5), the onium group represented by E is preferably the pyridinium group represented by the following formula (6).

In formula (6), R ¹⁷ represents a halogen atom, an alkyl group, an aryl group, a hydroxy group or an alkoxy group, and when a plurality of R ^17s are present, the plurality of R ^17s may be the same or different, or a plurality of Rs may be different. ¹⁷ may be connected to form a ring. n2 represents an integer from 0 to 4. R ¹⁸ represents an alkyl group or an aryl group. Z _b represents a counterion for neutralizing the charge.

The alkyl group or aryl group represented by R ¹⁷ or R ¹⁸ is the same as the alkyl group in R ² to R ⁹ and R ⁰ or the aryl group in R ⁰ , and the preferred embodiment is also in R ² to R ⁹ and R ⁰ . Similar to the preferred embodiment of the alkyl group or the aryl group at ^R0 .
The alkoxy group represented by R ¹⁷ is preferably an alkoxy group having 1 to 10 carbon atoms, and a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a tert-butoxy group and the like. Can be mentioned.
n2 is preferably 0.
The counterion for neutralizing the charge represented by Z _b is the same as Z ¹ in the formula (1-7), and the preferred embodiment is also the same as the preferred embodiment of Z ¹ in the formula (1-7). ..

Hereinafter, when L is an oxygen atom in Formula 1 or Formula 1-A, specific examples of the group represented by R ¹ are given, but the present disclosure is not limited thereto. In the following structural formula, TsO ⁻ represents a tosylate anion, and ● represents a binding site with an oxygen atom represented by L in Formula 1 or Formula 1-A.

When L is an oxygen atom and R ¹ is an aryl group or a linear alkyl group, cleavage of the R1 ^- O bond by infrared exposure does not occur.

When L is a sulfur atom in Formula 1 or Formula 1-A, R ¹ is preferably a group represented by the following formula (2-1).

In formula (2-1), ● represents a bonding site with a sulfur atom represented by L in formula 1 or formula 1-A, and R ²¹ independently has a hydrogen atom, an alkyl group or an aryl group, respectively. Representing, R ²² represents an aryl group, an alkenyl group, an alkoxy group or an onium group.

When L is −NR ¹⁰ − in formula 1 or formula 1-A, R ¹ bonded to N is preferably a group represented by the following formula (3-1).

In formula (3-1), ● represents a binding site with a nitrogen atom contained in L in formula 1 or formula 1-A, and X ¹ and X ² independently represent an oxygen atom or a sulfur atom, respectively. , Y represent a group represented by the above formula (2-1).

In the above formula (2-1), the alkyl group, aryl group, alkenyl group, alkoxy group and onium group represented by R ²¹ and R ²² are described in the above formulas (1-1) to (1-7). The description regarding the alkyl group, aryl group, alkenyl group, alkoxy group and onium group described can be incorporated.

In Formula 1 or Formula 1-A, it is preferable that L represents a sulfur atom or −NR ¹⁰ − and R ¹⁰ represents a hydrogen atom, an alkyl group or an aryl group from the viewpoint of improving printing durability.

R ₁ in the above formula 1 and the formula 1-A is preferably a group represented by the following formula 2.
Further, the group represented by the above formula 2 is preferably a group in which the ^RZO bond in the formula 2 is cleaved by infrared exposure.

In formula 2, R ^Z represents an alkyl group, and the wavy line portion represents a binding site with a group represented by L in formula 1 or formula 1-A.
The alkyl group represented by R ^Z is the same as the preferred embodiment of the alkyl group in ^R2 to ^R9 and ^R0 described above.
From the viewpoint of color development and UV printing resistance of the obtained lithographic printing plate, the alkyl group is preferably a secondary alkyl group or a tertiary alkyl group, and is a tertiary alkyl group. Is preferable.
Further, from the viewpoint of color development and UV printing resistance of the obtained flat plate printing plate, the alkyl group is preferably an alkyl group having 1 to 8 carbon atoms, and is branched with 3 to 10 carbon atoms. It is more preferably an alkyl group, further 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 t-butyl group.

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

Specific examples of infrared absorbers that decompose by infrared exposure are given below, but the present disclosure is not limited thereto.

Further, as the infrared absorber that decomposes by infrared exposure, those described in Japanese Patent Publication No. 2008-544322 or International Publication No. 2016/0278886 can be preferably used.

Only one type of infrared absorber may be used, or two or more types 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 in the image recording layer is preferably 0.1% by mass to 10.0% by mass, more preferably 0.5% by mass to 5.0% by mass, based on the total mass of the image recording layer. preferable.

[Polymer particles]
The image recording layer preferably contains polymer particles.
The polymer particles may be 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). preferable. Of these, polymer particles or microgels having a polymerizable group are preferable. In a particularly preferred embodiment, the polymer particles contain at least one ethylenically unsaturated polymerizable 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.
Further, the polymer particles are preferably thermoplastic polymer particles.

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 polymer 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 or mixtures thereof. Preferably, a copolymer containing polystyrene, styrene and acrylonitrile, or polymethyl methacrylate can be mentioned. The average particle size of the thermoplastic polymer particles is preferably 0.01 μm to 3.0 μm.

Examples of the heat-reactive polymer particles include polymer particles having a heat-reactive group. The heat-reactive polymer 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 Preferred examples thereof include a hydroxy group or an amino group as a reaction partner, an acid anhydride for carrying out a ring-opening addition reaction, and an amino group or a hydroxy group as a reaction partner.

As the microcapsules, for example, as described in JP-A-2001-277740 and JP-A-2001-277742, at least a part of the constituent components of the image recording layer is encapsulated in the microcapsules. The components of the image recording layer can also be contained outside the microcapsules. The image recording layer containing the microcapsules is preferably configured such that the hydrophobic constituents are encapsulated in the microcapsules and the hydrophilic constituents are contained outside the microcapsules.

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 radically polymerizable group on its surface is preferable from the viewpoint of image formation sensitivity and printing resistance.

Known methods can be applied to microencapsulate or microgelify the constituents of the image recording layer.

Further, as the polymer particles, from the viewpoint of printing resistance, stain resistance and storage stability, a polyvalent isocyanate compound which is an adduct of a polyvalent phenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate. , And those obtained by the reaction of a 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.
Examples of the resin particles 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 are Japanese Patent Application Laid-Open No. 2012. The polymer particles described in paragraphs 0032 to 0095 of the publication No. 206495 are preferably mentioned.

Further, the polymer particles have a hydrophobic main chain from the viewpoint of printing resistance and solvent resistance, and i) a constituent unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) It is preferable to include both constituent units having a pendant group containing a hydrophilic polyalkylene oxide segment.
Acrylic resin chains are preferably mentioned as the hydrophobic main chain.
As an example of the pendant cyano group,-[CH ₂ CH (C≡N)-] or-[CH ₂ C (CH ₃ ) (C≡N)-] is preferably mentioned.
Further, the constituent unit having the pendant cyano group can be easily derived from an ethylene-based unsaturated monomer, for example, acrylonitrile or methacrylonitrile, or a combination thereof.
Further, as the alkylene oxide in the hydrophilic polyalkylene oxide segment, ethylene oxide or propylene oxide is preferable, and ethylene oxide is more preferable.
The number of repetitions of the alkylene oxide structure in the hydrophilic polyalkylene oxide segment is preferably 10 to 100, more preferably 25 to 75, and even more preferably 40 to 50.
Both a constituent unit having a hydrophobic backbone and i) having a pendant cyano group directly attached to the hydrophobic backbone and ii) a constituent unit having a pendant group containing a hydrophilic polyalkylene oxide segment. As the resin particles containing the above, those described in paragraphs 0039 to 0068 of JP-A-2008-503365 are preferably mentioned.

The average particle size of the polymer 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 primary particle size of each of the above particles in the present disclosure is measured by a light scattering method, or an electron micrograph of the particle is taken, and a total of 5,000 particle size particles are measured on the photograph and averaged. The value shall be calculated. For non-spherical particles, the particle size of spherical particles having the same particle area as the particle area on the photograph is used as the particle size.
Further, the average particle size in the present disclosure shall be the volume average particle size unless otherwise specified.
The content of the polymer particles is preferably 5% by mass to 90% by mass with respect to the total mass of the image recording layer.

[Acid color former]
The image recording layer used in the present disclosure preferably contains an acid color former.
As used in the present disclosure, the "acid color former" means a compound having a property of developing a color 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, spiropyran, ester, and amide, and is colorless and the partial skeleton rapidly opens or cleaves when it comes into contact with an electron-accepting compound. Compounds are preferred.

Examples of such acid color formers are 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide (referred to as "crystal violet lactone") and 3,3-bis (4-). Dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1) , 2-Dimethylindole-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2-methylindole-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-3) -Il) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3-yl) ) -6-Dimethylaminophthalide, 3,3-bis (2-phenylindole-3-yl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1-methylpyrrole-) 3-Indole) -6-dimethylaminophthalide,

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

4,4-bis-dimethylaminobenzhydrinbenzyl ether, N-halophenyl-leucooramine, N-2,4,5-trichlorophenylleucooramine, rhodamine-B-anilinolactam, rhodamine- (4-nitroanilino) ) Lactam, Rhodamine-B- (4-chloroanilino) lactam, 3,7-bis (diethylamino) -10-benzoylphenoxazine, benzoyl leucomethylene blue, 4-nitrobenzoyl methylene blue,

3,6-Dimethoxyfluolane, 3-dimethylamino-7-methoxyfluolane, 3-diethylamino-6-methoxyfluolane, 3-diethylamino-7-methoxyfluolane, 3-diethylamino-7-chlorofluorine, 3 -Diethylamino-6-methyl-7-chlorofluorine, 3-diethylamino-6,7-dimethylfluorane, 3-N-cyclohexyl-Nn-butylamino-7-methylfluorine, 3-diethylamino-7- Dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-di-n-hexylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7- ( 2'-fluorophenylamino) fluorane, 3-diethylamino-7- (2'-chlorophenylamino) fluorane, 3-diethylamino-7- (3'-chlorophenylamino) fluorane, 3-diethylamino-7- (2', 3) '-Dichlorophenylamino) fluorane, 3-diethylamino-7- (3'-trifluoromethylphenylamino) fluorane, 3-di-n-butylamino-7- (2'-fluorophenylamino) fluorane, 3-di- n-butylamino-7- (2'-chlorophenylamino) fluorane, 3-N-isopentyl-N-ethylamino-7- (2'-chlorophenylamino) fluorane,

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

3-N- (2'-Methylethyl) -N-Methylamino-6-Methyl-7-anilinofluorane, 3-N- (2'-Methylethyl) -N-ethylamino-6-methyl-7 -Anilinofluorane, 3-N- (2'-methoxyethyl) -N-isobutylamino-6-methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-methylamino -6-Methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) ) -N-Methylamino-6-Methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3'-ethoxypropyl) -N-methylamino-6-methyl-7-anilinofluolane, 3-N- (3'-ethoxypropyl) -N-ethylamino-6-methyl-7-anilinofuru Olan, 3-N- (2'-tetrahydrofurfuryl) -N-ethylamino-6-methyl-7-anilinofluoran, 3-N- (4'-methylphenyl) -N-ethylamino-6- Methyl-7-anilinofluorane, 3-diethylamino-6-ethyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (3'-methylphenylamino) fluorane, 3-diethylamino-6- Methyl-7- (2', 6'-dimethylphenylamino) fluorane, 3-di-n-butylamino-6-methyl-7- (2', 6'-dimethylphenylamino) fluorane, 3-di-n -Butylamino-7- (2', 6'-dimethylphenylamino) fluorane, 2,2-bis [4'-(3-N-cyclohexyl-N-methylamino-6-methylfluorane) -7-yl Aminophenyl] Propane, 3- [4'-(4-phenylaminophenyl) Aminophenyl] Amino-6-methyl-7-chlorofluorane, 3- [4'-(dimethylaminophenyl)] Amino-5,7 -Fluolans such as dimethylfluorane,

3- (2-Methyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-n-propoxycarbonylamino-4-di-n) -Propylaminophenyl) -3- (1-ethyl-2-methylindole-3-yl) -4-azaphthalide, 3- (2-methylamino-4-di-n-propylaminophenyl) -3- (1) -Ethyl-2-methylindole-3-yl) -4-azaphthalide, 3- (2-methyl-4-din-hexylaminophenyl) -3- (1-n-octyl-2-methylindole-3-) Il) -4,7-diazaphthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3,3-bis (1-n-octyl-2-methylindole-3-yl) -4-Azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindole-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) ) -3- (1-octyl-2-methylindole-3-yl) -4 or 7-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-) 3-yl) -4 or 7-azaphthalide, 3- (2-hexyloxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindole-3-yl) -4 or 7-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide, 3- (2-butoxy-4-diethylaminophenyl) -3-( 1-Ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide 3-methyl-spiro-dinaftopyrane, 3-ethyl-spiro-dinaftopyrane, 3-phenyl-spiro-dinaftopylan, 3-benzyl-spiro-zinaftpyran , 3-Methyl-naphtho- (3-methoxybenzo) spiropirane, 3-propyl-spiro-dibenzopyran-3,6-bis (dimethylamino) fluorene-9-spiri-3'-(6'-dimethylamino) phthalide , 3,6-Bis (diethylamino) fluorene-9-spiro-3'-(6'-dimethylamino) phthalides and other phthalides,

In addition, 2'-anilino-6'-(N-ethyl-N-isopentyl) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthen-3-one, 2'-anilino -6'-(N-ethyl-N- (4-methylphenyl)) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one, 3'-N , N-Dibenzylamino-6'-N, N-diethylaminospiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one, 2'-(N-methyl-N-phenyl) Amino-6'-(N-ethyl-N- (4-methylphenyl)) aminospiro [isobenzofuran-1 (3H), 9'-(9H) xanthene] -3-one and the like can be mentioned.

Among them, the acid color former used in the present disclosure is 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. preferable.
The hue of the dye after color development is preferably green, blue or black from the viewpoint of visibility.

As the acid color former, it is also possible to use products on the market, such as ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H. -3035, BLUE203, ATP, H-1046, H-2114 (all manufactured by Fukui Yamada Chemical Industry Co., Ltd.), ORANGE-DCF, Vermilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF , TH-107 (all manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green -118, Red-40, Red-8 (all manufactured by Yamamoto Kasei Co., Ltd.), crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.) and the like can be mentioned. 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 to be formed has a good visible light absorption rate.

These acid color formers may be used alone or in combination of two or more kinds of components.
The content of the acid 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.

[Binder polymers other than specific binder polymers]
The image recording layer may contain a binder polymer other than the specific binder polymer (hereinafter, also referred to as “another binder polymer”).
The specific binder polymer and the polymer corresponding to the polymer particles do not correspond to the other binder polymers. That is, the other binder polymer is a non-particle-shaped polymer having at least one selected from the group consisting of a structural unit formed of an aromatic vinyl compound and a structural unit formed of an acrylonitrile compound. ..
As the other binder polymer, a (meth) acrylic resin, a polyvinyl acetal resin, or a polyurethane resin is preferable.

Among them, as the other binder polymer, a known binder polymer used for the image recording layer of the lithographic 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 a machine-developed lithographic printing plate precursor 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 other binder polymers, a polyfunctional thiol having 6 or more functionalities and 10 or less functionals as a nucleus has a polymer chain bonded to the nucleus by a sulfide bond, and the polymer chain has a polymerizable group. Examples thereof include polymer compounds having (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 forms crosslinks between the polymer molecules and promotes curing.
As the polymerizable group, an ethylenically unsaturated group such as a (meth) acrylic group, a vinyl group, an allyl group or a vinylphenyl group (styryl group) or an epoxy group is preferable, and a (meth) acrylic group, a vinyl group or a vinylphenyl is 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. 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. These groups may be used together.

As for the molecular weight of the other binder polymer, the weight average molecular weight (Mw) is preferably 2,000 or more, more preferably 5,000 or more, and 10,000 to 300, as a polystyrene-equivalent value by the GPC method. It is more preferably 000.

If necessary, hydrophilic polymers such as polyacrylic acid and polyvinyl alcohol described in JP-A-2008-195018 can be used in combination. In addition, a lipophilic polymer and a hydrophilic polymer can be used in combination.

In the image recording layer used in the present disclosure, one type of other binder polymer may be used alone, or two or more types may be used in combination.
Other binder polymers can be contained in the image recording layer in an arbitrary amount, but the content of the binder polymer may be 1% by mass to 90% by mass with respect to the total mass of the image recording layer. It is preferably 5% by mass to 80% by mass, more preferably 5% by mass.
Further, when the image recording layer in the present disclosure contains another binder polymer, the content of the other binder polymer with respect to the total mass of the above-mentioned specific binder polymer and the other binder polymer is more than 0% by mass and 99% by mass or less. It is preferably 20% by mass to 95% by mass, more preferably 40% by mass to 90% by mass.

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

Specific examples of the chain transfer agent include the following compounds.

As the chain transfer agent, only one kind may be added, or two or more kinds may be used in combination.
The content of the chain transfer agent is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 40% by mass, and 0.1% by mass to 30% by mass with respect to the total mass of the image recording layer. % Is more preferable.

[Fat sensitive agent]
The image recording layer may contain a fat-sensing agent such as a phosphonium compound, a nitrogen-containing small molecule compound, and an ammonium group-containing polymer in order to improve the inking property. In particular, when the overcoat layer contains the inorganic layered compound, these compounds function as a surface coating agent for the inorganic layered compound, and the deterioration of the inking property during printing due to the inorganic layered compound can be suppressed.
As the fat-sensing agent, it is preferable to use a phosphonium compound, a nitrogen-containing low molecular weight compound, and an ammonium group-containing polymer in combination, and the phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer are used in combination. Is more preferable.

-Phosphonium compound-
Examples of the phosphonium compound include the phosphonium compounds described in JP-A-2006-297907 and JP-A-2007-50660. Specific examples include tetrabutylphosphonium iodide, butyltriphenylphosphonium bromide, tetraphenylphosphonium bromide, 1,4-bis (triphenylphosphonio) butane-di (hexafluorophosphate), and 1,7-bis (tri). Phenylphosphonio) heptane-sulfate, 1,9-bis (triphenylphosphonio) nonan-naphthalen-2,7-disulfonate and the like can be mentioned.

-Nitrogen-containing small molecule compound-
Examples of the nitrogen-containing small molecule compound include amine salts and quaternary ammonium salts. Further, imidazolinium salts, benzoimidazolinium salts, pyridinium salts, quinolinium salts and the like can also be mentioned. Of these, quaternary ammonium salts and pyridinium salts are preferable. Specific examples include tetramethylammonium = hexafluorophosphate, tetrabutylammonium = hexafluorophosphate, dodecyltrimethylammonium = p-toluenesulfonate, benzyltriethylammonium = hexafluorophosphate, and benzyldimethyloctylammonium = hexafluorophos. Examples thereof include fert, benzyldimethyldodecylammonium = hexafluorophosphate, the compounds described in paragraphs 0021 to 0037 of JP-A-2008-284858, and the compounds described in paragraphs 0030 to 0057 of JP-A-2009-90645.

-Ammonium group-containing polymer-
The ammonium group-containing polymer may have an ammonium group in its structure, and a polymer containing 5 mol% to 80 mol% of a (meth) acrylate having an ammonium group in the side chain as a copolymerization component is preferable. Specific examples include the polymers described in paragraphs 809-0105 of JP2009-208458A.

The ammonium salt-containing polymer preferably has a reduction specific viscosity (unit: ml / g) in the range of 5 to 120, which is obtained according to the measurement method described in JP-A-2009-208458, and is in the range of 10 to 110. Those in the range of 15 to 100 are particularly preferable. When the reduced specific viscosity is converted into a weight average molecular weight (Mw), it is preferably 10,000 to 150,000, more preferably 17,000 to 140,000, and particularly preferably 20,000 to 130,000.

Specific examples of the ammonium group-containing polymer are shown below.
(1) 2- (trimethylammonio) ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90, Mw 45,000)
(2) 2- (trimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(3) 2- (Ethyldimethylammonio) Ethylmethacrylate = p-toluenesulfonate / hexylmethacrylate copolymer (molar ratio 30/70, Mw45,000)
(4) 2- (trimethylammonio) ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(5) 2- (trimethylammonio) ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (molar ratio 40/60, Mw 7,000,000)
(6) 2- (Butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 25/75, Mw 65,000)
(7) 2- (Butyldimethylammonio) ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 65,000)
(8) 2- (Butyldimethylammonio) ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80) , Mw 75,000)

The content of the oil-sensitive agent is preferably 1% by mass to 40.0% by mass, more preferably 2% by mass to 25.0% by mass, and 3% by mass to 20% by mass with respect to the total mass of the image recording layer. % Is more preferable.

[Other ingredients]
The image recording layer may contain a surfactant, a polymerization inhibitor, a higher fatty acid derivative, a plasticizer, inorganic particles, an inorganic layered compound and the like as other components. Specifically, the description in paragraphs 0114 to 0159 of JP-A-2008-284817 can be referred to.

[Formation of image recording layer]
As described in paragraphs 0142 to 0143 of JP-A-2008-195018, for example, the image recording layer in the lithographic printing plate original plate according to the present disclosure is coated by dispersing or dissolving each of the above-mentioned necessary components in a known solvent. It can be formed by preparing a liquid, applying the coating liquid on the support by a known method such as coating with a bar coater, and drying the liquid. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but is preferably 0.3 g / m ² to 3.0 g / m ² . In this range, good sensitivity and good film characteristics of the image recording layer can be obtained.
As the solvent, 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, Propropylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3- Methoxy-1-propanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N, N-dimethyl 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 5.0 μm, and more preferably 0.3 μm to 2.0 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 observing the cross section of the section with a scanning electron microscope (SEM). Confirmed by.

<Overcoat layer>
The lithographic printing plate original plate according to the present disclosure has an overcoat layer (sometimes referred to as a "protective layer") on the surface of the image recording layer on the side opposite to the support side.
The film thickness of the overcoat layer is thicker than the film thickness of the image recording layer.
The overcoat layer has a function of suppressing an image formation inhibitory reaction by blocking oxygen, a function of preventing scratches in the image recording layer, and a function of preventing ablation during high-illuminance laser exposure.

An overcoat layer having such characteristics is described in, for example, US Pat. No. 3,458,311 and Japanese Patent Application Laid-Open No. 55-49729. As the oxygen low-permeability polymer used for the overcoat layer, either a water-soluble polymer or a water-insoluble polymer can be appropriately selected and used, and if necessary, two or more kinds may be mixed and used. However, from the viewpoint of on-machine developability, it is preferable to contain a water-soluble polymer.
In the present disclosure, the water-soluble polymer is a solution in which 1 g or more is dissolved in 100 g of pure water at 70 ° C. and 1 g of the polymer is dissolved in 100 g of pure water at 70 ° C., and the solution is cooled to 25 ° C. A polymer that does not precipitate.
Examples of the water-soluble polymer used in the overcoat layer include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, water-soluble cellulose derivative, polyethylene glycol, poly (meth) acrylonitrile and the like.
As the modified polyvinyl alcohol, an acid-modified polyvinyl alcohol having a carboxy group or a sulfo group is preferably used. Specific examples thereof include the modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137.

Among the water-soluble polymers, polyvinyl alcohol is preferably contained, and polyvinyl alcohol having a saponification degree of 50% or more is more preferably contained.
The saponification degree is preferably 60% or more, more preferably 70% or more, still more preferably 85% or more. The upper limit of the saponification degree is not particularly limited and may be 100% or less.
The saponification degree is measured according to the method described in JIS K 6726: 1994.
Further, as one aspect of the overcoat layer, an aspect containing polyvinyl alcohol and polyethylene glycol is also preferably mentioned.

When the overcoat layer in the present disclosure contains a water-soluble polymer, the content of the water-soluble polymer with respect to the total mass of the overcoat layer is preferably 10% by mass to 99% by mass, preferably 30% by mass to 95% by mass. It is more preferably 50% by mass to 90% by mass.

The overcoat layer may contain an inorganic layered compound in order to enhance oxygen barrier properties. The inorganic layered compound is a particle having a thin flat plate shape, for example, a group of mica such as natural mica and synthetic mica, formula: talc, teniolite, montmorillonite, saponite, hectorite represented by 3MgO · 4SiO · _H2O . Examples include light, zirconium phosphate and the like.
The inorganic layered compound preferably used is a mica compound. Examples of the mica compound include formula: A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O) ₂ [However, A is any of K, Na, Ca, and B and C are It is any of Fe (II), Fe (III), Mn, Al, Mg, and V, and D is Si or Al. ] Can be mentioned as a group of mica such as natural mica and synthetic mica.

In the mica group, natural mica includes muscovite, paragonite, phlogopite, biotite and lepidolite. As synthetic mica, non-swelling mica such as fluorine gold mica KMg ₃ (AlSi ₃ O ₁₀ ) F ₂ , potash tetrasilicon mica KM g _2.5 Si ₄ O ₁₀ ) F ₂ , and Na tetrasilic mica NaMg _{2. 5} (Si ₄ O ₁₀ ) F ₂ , Na or Li teniolite (Na, Li) Mg ₂ Li (Si ₄ O ₁₀ ) F ₂ , montmorillonite-based Na or Li hectrite (Na, Li) _1/8 Mg _{2 /} Examples thereof include swelling mica such as ₅ Li _1/8 (Si ₄ O ₁₀ ) F ₂ . In addition, synthetic smectites are also useful.

Among the above mica compounds, fluorine-based swelling mica is particularly useful. That is, the swellable synthetic mica has a laminated structure composed of a unit crystal lattice layer having a thickness of about 10 Å to 15 Å (1 Å = 0.1 nm), and the metal atom substitution in the lattice is significantly larger than that of other clay minerals. As a result, the lattice layer causes a positive charge shortage, and in order to compensate for it, cations such as Li ⁺ , Na ⁺ , Ca ²⁺ , and Mg ²⁺ are adsorbed between the layers. The cations intervening between these layers are called commutative cations and can be exchanged with various cations. In particular, when the cations between layers are Li ⁺ and Na ⁺ , the bond between the layered crystal lattices is weak because the ionic radius is small, and the cations are greatly swollen by water. When share is applied in that state, it easily cleaves and forms a stable sol in water. Swellable synthetic mica has a strong tendency to this and is particularly preferably used.

As for the shape of the mica compound, from the viewpoint of diffusion control, the thinner the thickness, the better, and the plane size is better as long as it does not impair the smoothness of the coated surface and the permeability of the active light beam. Therefore, the aspect ratio is preferably 20 or more, more preferably 100 or more, and particularly preferably 200 or more. The aspect ratio is the ratio of the major axis to the thickness of the particle, which can be measured, for example, from a micrograph projection of the particle. The larger the aspect ratio, the greater the effect obtained.

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

The content of the inorganic layered compound is preferably 1% by mass to 60% by mass, more preferably 3% by mass to 50% by mass, based on the total solid content of the overcoat layer. Even when a plurality of types of inorganic layered compounds are used in combination, it is preferable that the total amount of the inorganic layered compounds is the above-mentioned content. Oxygen blocking property is improved in the above range, and good sensitivity can be obtained. In addition, it is possible to prevent a decrease in meat-forming property.

The overcoat layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coatability, and inorganic particles for controlling the slipperiness of the surface. Further, the oil-sensitive agent described in the image recording layer may be contained in the overcoat layer.

The overcoat layer is applied by a known method. The coating amount (solid content) of the overcoat layer is preferably 0.01 g / m ² to 10 g / m ² , more preferably 0.02 g / m ² to 3 g / m ² , and more preferably 0.02 g / m ² to 1 g / m. m ² is particularly preferred.
The film thickness of the overcoat layer in the lithographic printing plate precursor according to the present disclosure is preferably 0.01 μm to 5.0 μm, and more preferably 0.1 μm to 1.0 μm.
The film thickness of the overcoat layer in the lithographic printing plate original plate according to the present disclosure is preferably 0.01 to 5 times, preferably 0.1 to 1 times, the film thickness of the image recording layer. Is more preferable.

<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 heat generated by the exposure from diffusing to the support and reducing the sensitivity.

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 methacrylic group, an acrylamide group, a methacrylicamide 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.

In addition to the above-mentioned compound for the undercoat layer, the undercoat layer includes a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, an amino group or a functional group having a polymerization prohibitive ability and a support surface in order to prevent stains over time. Compounds with groups that interact with (eg, 1,4-diazabicyclo [2.2.2] octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranyl, sulfophthalic acid, hydroxy). Ethylenediaminediacetic acid, dihydroxyethylethylenediaminediacic acid, hydroxyethyliminodiacetic acid, etc.) may be contained.

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

(Planographic printing plate manufacturing method 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 machine-developed lithographic printing plate original plate according to the present disclosure to an image (hereinafter, also referred to as an “exposure step”), printing ink and a wet plate. 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 on the printing machine (hereinafter, also referred to as “on-machine development step”).
The flat plate printing method according to the present disclosure includes a step of exposing the on-machine development type flat plate printing plate original plate according to the present disclosure to an image (exposure step) and at least one selected from the group consisting of printing ink and dampening water. It includes a step of producing a flat plate printing plate by supplying and removing an image recording layer of a non-image portion on a printing machine (on-machine development step), and a step of printing with the obtained flat plate printing plate (printing step). Is preferable.
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 and the on-machine development step in the lithographic printing method according to the present disclosure are the same steps.

<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 flat plate 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 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 includes an on-machine development step of supplying at least one selected from the group consisting of printing ink and dampening water to remove the image recording layer of the non-image portion on the printing machine. 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.

As the laser for image-exposing the lithographic printing plate original plate according to the present disclosure, the wavelength of the light source is preferably 300 nm to 450 nm or 750 nm to 1,400 nm. 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, 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.

(Examples 1 to 30 and Comparative Examples 1 to 7)
<Making a support>
In order to remove the rolling oil on the surface of an aluminum plate (material JIS A 1050) having 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 surface of the aluminum plate was sanded using three 3 mm bundled nylon brushes and a Pamis-aqueous suspension (specific gravity 1.1 g / cm ³ ) having a median diameter of 25 μm, and washed thoroughly with water. The aluminum 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. 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 was a 1% by mass aqueous solution of nitric acid (containing 0.5% by mass of aluminum ions), and the liquid temperature was 50 ° C. The AC power supply waveform is electrochemically roughened using a carbon electrode as the counter electrode using a trapezoidal square wave AC with a TP of 0.8 ms from zero to the peak of the current value and a duty ratio of 1: 1. 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, a 0.5% by mass hydrochloric acid aqueous solution (containing 0.5% by mass of aluminum ions) and an electrolytic solution having a liquid temperature of 50 ° C. were used to electrolyze nitrate under the condition that the aluminum plate had an electric value 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 of 2.5 g / m ² was formed on an aluminum plate using a 15 mass% sulfuric acid aqueous solution (containing 0.5 mass% of aluminum ions) as an electrolytic solution at a current density of 15 A / dm ² , and then washed with water. , Dryed to make a support. The average pore diameter (surface average pore diameter) on the surface layer of the anodic oxide film was 10 nm.
An ultra-high resolution SEM (scanning electron microscope, S-900 manufactured by Hitachi, Ltd.) is used to measure the pore diameter on the surface layer of the anodic oxide film, and conductivity is imparted at a relatively low acceleration voltage of 12 V. The surface was observed at a magnification of 150,000 times, and 50 pores were randomly selected to obtain an average value without performing a vapor deposition treatment or the like. The standard deviation was less than ± 10% of the mean.

<Formation of lithographic printing plate original plate>
The undercoat liquid (1) having the following composition was applied onto the support so that the dry coating amount was 20 mg / m ² , and dried in an oven at 100 ° C. for 30 seconds to prepare a support having an undercoat layer.
The following image recording layer coating liquid (1) is bar-coated on the undercoat layer, dried in an oven at 100 ° C. for 60 seconds, and dried. The image recording layer has a coating amount of 0.60 g / m ² (thickness = about 0.60 μm). Was formed, and a lithographic printing plate original plate was obtained.
After that, the overcoat layer coating liquid (1) having the following composition is applied onto the image recording layer, dried in an oven at 100 ° C. for 60 seconds, and dried in an amount of 1.0 g / m ² (film thickness = about 1.0 μm). ) Was formed, and a lithographic printing plate original plate was obtained.
Further, in Examples 7, 21, 24 and 27, the dry coating amount was changed so that the content of each component in the overcoat layer had the value shown in the content shown in Table 1.

[Undercoat liquid (1)]
・ The following undercoat compound 1: 0.18 parts ・ Methanol: 55.24 parts ・ Distilled water: 6.15 parts

-Synthesis of undercoat compound 1-
<< Purification of Monomer M-1 >>
Add 420 parts of light ester P-1M (2-methacryloyloxyethyl acid phosphate, manufactured by Kyoeisha Chemical Co., Ltd.), 1,050 parts of diethylene glycol dibutyl ether and 1,050 parts of distilled water to the separating funnel, stir vigorously and then statically. Placed. After discarding the upper layer, 1,050 parts of diethylene glycol dibutyl ether was added, and the mixture was vigorously stirred and then allowed to stand. The upper layer was discarded to obtain 1,300 parts of an aqueous solution of monomer M-1 (10.5% by mass in terms of solid content).

<< Synthesis of Undercoat Compound 1 >>
53.73 parts of distilled water and 3.66 parts of the monomer M-2 shown below were added to the three-necked flask, and the temperature was raised to 55 ° C. under a nitrogen atmosphere. Next, the dropping liquid 1 shown below was added dropwise over 2 hours, and after stirring for 30 minutes, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate ( VA-046B and 0.386 parts of Fujifilm Wako Pure Chemical Industries, Ltd. were added, the temperature was raised to 80 ° C., and the mixture was stirred for 1.5 hours. After returning the reaction solution to room temperature (25 ° C.), add a 30 mass% sodium hydroxide aqueous solution to adjust the pH to 8.0, and then 4-hydroxy-2,2,6,6-tetramethylpiperidine-1. -Oxyl (4-OH-TEMPO, manufactured by Aldrich) was added in an amount of 0.005 parts. By the above operation, 180 parts of an aqueous solution of the undercoat compound 1 was obtained. The weight average molecular weight (Mw) in terms of polyethylene glycol by gel permeation chromatography (GPC) was 170,000.

<< Drop liquid 1 >>
・ Monomer M-1 aqueous solution: 87.59 parts ・ Monomer M-2: 14.63 parts ・ VA-046B (2,2'-azobis [2- (2-imidazolin-2-yl) propane] distillate] Fate the hydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.): 0.386 parts, distilled water: 20.95 parts

<Image recording layer coating liquid (1)>
-Infrared absorber 1 (compound with the following structure): 0.030 parts-Di-p-tolyliodonium PF ₆ ^- salt (manufactured by Aldrich): 0.032 parts-NK ester A-9300 (Shin Nakamura Chemical Industry Co., Ltd.) ): 0.100 parts ・ A-DPH (manufactured by Shin Nakamura Chemical Industry Co., Ltd.): 0.100 parts ・ BYK306 (Byk Chemie): 0.008 parts ・ 1-methoxy-2-propanol: 8. 609 parts ・ Methyl ethyl ketone: 1.091 parts ・ Specific binder polymer shown in Table 1 or Table 2: Amount shown in Table 1 or Table 2 ・ Specific development accelerator shown in Table 1 or Table 2: Table 1 or Table 2 Amount listed in

<Overcoat layer coating liquid>
-Water-soluble polymer shown in Table 1 or Table 2: Amount shown in Table 1 or Table 2-Surfactant (Rapisol® (registered trademark) (A-80, manufactured by NOF CORPORATION): 0.01 parts by mass)・ Water: Amount that makes up 10 parts by mass

(Example 31 and Example 32)
In Example 1, a lithographic printing plate original plate was obtained in the same manner as in Example 1 except that the infrared absorber 1 was changed to the infrared absorber shown in Table 1.

In Table 1, the numerical values described in the columns of "P-1" to "P-3" in the column of the specific binder polymer indicate the content (parts by mass) of the following P-1 to P-3. The description of "-" indicates that the compound is not contained.
In Table 1, the numerical values described in the columns of "A-1" to "A-4" of the specific development accelerator indicate the content (parts by mass) of the following A-1 to A-4. The description of "-" indicates that the compound is not contained.
In Table 1, the description in the "type" and "content" columns of the water-soluble polymer column indicates the type and content (parts by mass) of the water-soluble polymer used, respectively.
In Table 2, the description in the "type" and "content" columns in the specific binder polymer column is the type of the specific binder polymer used, respectively. In the table 2, the "type" and "content" in the specific development accelerator column. The description in the column of "" indicates the type and content (parts by mass) of the specific binder polymer used respectively.
In Table 2, the description in the "type" and "content" columns of the water-soluble polymer column indicates the type and content (parts by mass) of the water-soluble polymer used, respectively.
Details of the compounds listed in Table 1 or Table 2 are as follows.

<Specific binder polymer>
[Synthesis of binder polymer P-1]
300 g of methyl ethyl ketone was placed in a three-necked flask and heated to 80 ° C. under a nitrogen stream. A mixed solution consisting of 50.0 g of the following compound (1), 50.0 g of the following compound (2), 0.7 g of AIBN (azobisisobutyronitrile), and 100 g of methyl ethyl ketone was added dropwise to this reaction vessel over 30 minutes. After the completion of the dropping, the reaction was continued for another 7.5 hours. Then, 0.3 g of AIBN was added, and the reaction was continued for another 12 hours. After completion of the reaction, the reaction solution was cooled to room temperature to obtain P-1. The weight average molecular weight of the obtained P-1 was 75,000.

[Synthesis of binder polymer P-2]
300 g of methyl ethyl ketone was placed in a three-necked flask and heated to 80 ° C. under a nitrogen stream. A mixed solution consisting of 70.0 g of compound (1), 20.0 g of compound (2), 10.0 g of compound (3), 0.7 g of AIBN, and 100 g of methyl ethyl ketone was added dropwise to this reaction vessel over 30 minutes. After the completion of the dropping, the reaction was continued for another 7.5 hours. Then, 0.3 g of AIBN was added, and the reaction was continued for another 12 hours. After completion of the reaction, the reaction solution was cooled to room temperature to obtain P-2. The weight average molecular weight of the obtained P-2 was 50,000.

[Synthesis of binder polymer P-3]
300 g of methyl ethyl ketone was placed in a three-necked flask and heated to 80 ° C. under a nitrogen stream. A mixed solution consisting of 90.0 g of the above compound (1), 40.0 g of the above compound (2), 10.0 g of the above compound (3), 0.7 g of AIBN, and 100 g of methyl ethyl ketone was placed in this reaction vessel over 30 minutes. Dropped. After the completion of the dropping, the reaction was continued for another 7.5 hours. Then, 0.3 g of AIBN was added, and the reaction was continued for another 12 hours. After completion of the reaction, the reaction solution was cooled to room temperature to obtain P-3. The weight average molecular weight of the obtained P-3 was 60,000.

[Specific binder polymer for comparison]
Klucel 99M: Hydroxypropyl Cellulose, manufactured by Hurcles

<Specific development accelerator>
A-1: Tris (2-hydroxyethyl) isocyanurate, SP value polar term value = 6.4
A-2: Trimethylglycine, SP value polarity term value = 6.5
A-3: Compound A-3 having the following structure, SP value polar term value = 8.1
A-4: Hydroxypropylmethylcellulose, SP value polar term value = 11.0 (60SH, Shin-Etsu Chemical Co., Ltd.)

[Specific development accelerator for comparison]
NK Ester A-9300: Ethoxylated isocyanuric acid triacrylate, SP value polar term value = 1.8
Compound A: PF ₆ ^- salt of the compound having the following structure, SP value polar term value = 26.8

<Water-soluble polymer>
PVA105: Polyvinyl alcohol (degree of saponification = 98% to 99%), manufactured by Kuraray Co., Ltd. PVA205: Polyvinyl alcohol (degree of saponification = 86.5% to 89.0%), manufactured by Kuraray Co., Ltd. PVA405: Polyvinyl alcohol (saponification) Degree = 80.0% -83.0%), LM-10HD manufactured by Kuraray Co., Ltd .: Polyvinyl alcohol (conservation degree = 38% to 42%), LM-20 manufactured by Kuraray Co., Ltd .: Polyvinyl alcohol (concentration degree =) 38% -42%), LM-25 manufactured by Kuraray Co., Ltd .: Polyvinyl alcohol (concentration = 33% -38%), PEG4000 manufactured by Kuraray Co., Ltd .: polyethylene glycol, manufactured by Tokyo Kasei Kogyo Co., Ltd.

[Infrared absorber]
The details of the infrared absorber in Table 1 are as follows.
Infrared absorber 2: Compound with the following structure Infrared absorber 3: Compound with the following structure

<Evaluation>
[Scratch resistance of outer layer]
Using the lithographic printing plate originals obtained in each example or comparative example, a scratch test: A 0.1 mm diameter sapphire needle was weighted from 5 g to 100 g at 5 g intervals, and the sample surface of each lithographic plate original was scanned. Used for scratch test (measured with a scratch strength tester manufactured by Shinto Kagaku Co., Ltd.).
The lithographic printing plate precursor after the scratch test was placed on a Kodak® Trendsetter 800II Q uantum platesetter (830 nm), and the scratched part was a solid image and an exposed image including a 50% halftone dot chart of a 20 μm dot FM screen and a non-image. Exposure was performed using an infrared (IR) laser of 830 nm so as to straddle the portions. The obtained exposed original plate was attached to a plate cylinder of a printing machine LITHRONE26 manufactured by Komori Corporation without developing. Efficiency-2 (manufactured by Fujifilm Co., Ltd.) / Tap water = 2/98 (capacity ratio) of dampening water and Space Color Fusion G ink ink (manufactured by DIC Graphics Co., Ltd.), standard automatic of LITHRONE26 After supplying dampening water and ink by the printing start method and developing on the machine, 500 sheets were printed on Tokubishi Art (ream weight: 76.5 kg) paper at a printing speed of 10,000 sheets per hour.
On the obtained 500th printed matter, the maximum load in which the image part was not damaged due to scratches or the development failure / ink stain of the non-image part did not occur was evaluated as the outer layer scratch resistance (g), and Table 3 shows. Described. It can be said that the larger the maximum load is, the better the lithographic printing plate is in scratch resistance.

[Ink inking property (ink inking property)]
Using the planographic printing plate original plate obtained in each Example or Comparative Example, development was carried out by the same method as the development method for scratch resistance of the outer layer, except that the scratch test was not performed. The lithographic printing plate after the development treatment was attached to the plate cylinder of the printing machine LITHRONE26 manufactured by Komori Corporation. Using Efficiency-2 (manufactured by Fujifilm Co., Ltd.) / tap water = 2/98 (capacity ratio) dampening water and Values-G (N) ink ink (manufactured by Dainippon Ink Chemical Industry Co., Ltd.). Printing is started by supplying dampening water and ink using the standard automatic printing start method of LITHRONE26, and printing is performed on 100 sheets of Tokubishi Art (ream amount: 76.5 kg) paper at a printing speed of 10,000 sheets per hour. gone.
The number of sheets of printing paper required for the ink density on the printing paper in the exposed area of the image recording layer to reach the specified standard density was measured as the initial ink fillability for printing, and is shown in Table 3.

[In-machine developability]
The flat plate printing plate original plate in each example or comparative example is mounted on a Fujifilm Luxel PLATESETTER T-6000III equipped with an infrared semiconductor laser, and the outer surface drum rotation speed is 1000 rpm (revolutions per minute), the laser output is 70%, and the resolution is 2400 dpi (. The exposure was performed under the condition of dot per inch, 1 inch = 2.54 cm). The exposed image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The obtained exposed original plate was attached to a plate cylinder of a printing machine LITHRONE26 manufactured by Komori Corporation without developing. Efficiency-2 (manufactured by Fujifilm Co., Ltd.) / Tap water = 2/98 (capacity ratio) of dampening water and Space Color Fusion G ink ink (manufactured by DIC Graphics Co., Ltd.), standard automatic of LITHRONE26 After supplying dampening water and ink by the printing start method and developing on the machine, 500 sheets were printed on Tokubishi Art (ream weight: 76.5 kg) paper at a printing speed of 10,000 sheets per hour.
The number of printing papers required to complete the on-machine development of the unexposed part of the image recording layer on the printing machine and to prevent the ink from being transferred to the non-image part was measured as the on-machine developability, and Table 3 Described in.

[In-machine development residue]
During the evaluation of the on-machine developability, the presence or absence of debris adhering to the watering roller was sensory-evaluated. Those that did not have were designated as A and are listed in Table 3.

From the results shown in Table 3, according to the lithographic printing plate original plate according to the examples, the generation of on-machine developing residue is suppressed, and a lithographic printing plate having excellent on-machine developability, inking property and scratch resistance can be obtained. You can see that.

The disclosures of Japanese Patent Application No. 2018-142864 filed on July 30, 2018 and Japanese Patent Application No. 2018-205747 filed on October 31, 2018 are by reference in their entirety. Incorporated herein.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Is incorporated herein by reference.

Claims (17)

It has a support, an image recording layer, and an overcoat layer in this order.
The image recording layer contains a binder polymer and a development accelerator.
The binder polymer has a structural unit formed of an aromatic vinyl compound and a structural unit formed of an acrylonitrile compound.
The value of the polarity term of the SP value of the development accelerator is 6.0 to 26.0.
An on-machine development type lithographic printing plate original plate in which the film thickness of the overcoat layer is thicker than the film thickness of the image recording layer. The on-machine development type according to claim 1, wherein the image recording layer further contains a polymerizable compound, and the content of the binder polymer with respect to the total mass of the polymerizable compound is more than 0% by mass and 400% by mass or less. Planographic printing plate original plate. The machine-developed lithographic printing plate original plate according to claim 1 or 2, wherein the overcoat layer contains a water-soluble polymer. The machine-developed lithographic printing plate original plate according to claim 3, wherein the water-soluble polymer contains polyvinyl alcohol having a saponification degree of 50% or more. The on-machine development type lithographic printing plate original plate according to any one of claims 1 to 4, wherein the development accelerator is a compound having a cyclic structure. The machine-developed lithographic printing plate original plate according to claim 5, wherein the compound having a cyclic structure has a hydroxy group. The machine-developed lithographic printing plate original plate according to any one of claims 1 to 6, wherein the development accelerator is an onium compound. The machine-developed lithographic printing plate original plate according to any one of claims 1 to 7, which contains two or more compounds as the development accelerator. The machine-developed lithographic printing plate original plate according to any one of claims 1 to 8, wherein the binder polymer further has a structural unit formed of N-vinylpyrrolidone. The machine-developed lithographic printing plate original plate according to any one of claims 1 to 9, wherein the image recording layer further contains an infrared absorber. The machine-developed lithographic printing plate original plate according to claim 10, wherein the infrared absorber is an infrared absorber that decomposes by infrared exposure. The machine-developed lithographic printing plate original plate according to claim 10, wherein the infrared absorber is an infrared absorber that decomposes due to heat, electron transfer, or both caused by infrared exposure. The machine-developed lithographic printing plate original plate according to any one of claims 10 to 12, wherein the infrared absorber is a cyanine dye. The machine-developed lithographic printing plate original plate according to any one of claims 10 to 13, wherein the infrared absorber is a compound represented by the following formula 1.

In Equation 1, R ¹ represents a group in which the R ¹ -L bond is cleaved by infrared exposure, and R ₁₁ to R ₁₈ independently contain a hydrogen atom, a halogen atom, -Ra, -ORb, -SRc or -NRdRe. Ra to Re each independently represent a hydrocarbon group, and A ₁ , A ₂ and a plurality of R ₁₁ to R ₁₈ may be linked to form a single ring or a poly ring, and A ₁ and A ₂ may be formed. Independently represent an oxygen atom, a sulfur atom or a nitrogen atom, and n ₁₁ and n ₁₂ each independently represent an integer of 0 to 5, where the sum of n ₁₁ and n ₁₂ is 2 or more and n. ₁₃ and n ₁₄ independently represent 0 or 1, L represents an oxygen atom, a sulfur atom or -NR ^10- , R ¹⁰ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a charge neutralizing. Represents a counter ion. The machine-developed lithographic printing plate original plate according to claim 14, wherein R ¹ in the above formula 1 is a group represented by the following formula 2.

In the formula 2, R ^Z represents an alkyl group, and the wavy line portion represents a binding site with a group represented by L in the formula 1. A step of exposing the machine-developed lithographic printing plate original plate according to any one of claims 1 to 15 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 to remove an image recording layer of a non-image portion on a printing machine. A step of exposing the machine-developed lithographic printing plate original plate according to any one of claims 1 to 15 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 of the non-image portion on the printing machine to prepare a lithographic printing plate.
A lithographic printing method including a step of printing with the obtained lithographic printing plate.