WO2020026810A1

WO2020026810A1 - On-press development type lithographic printing plate precursor, method of producing lithographic printing plate, and lithographic printing method

Info

Publication number: WO2020026810A1
Application number: PCT/JP2019/028069
Authority: WO
Inventors: 啓介野越; 健次郎荒木
Original assignee: 富士フイルム株式会社
Priority date: 2018-07-30
Filing date: 2019-07-17
Publication date: 2020-02-06
Also published as: JPWO2020026810A1; JP2023016860A; JP7378566B2; CN112512824A; CN112512824B

Abstract

Provided are: an on-press development type lithographic printing plate precursor which has, in order, a support, an image recording layer, and an overcoat layer, wherein the image recording layer includes a binder polymer and an electron donor type polymerization initiator, the binder polymer has a constituent unit formed by an aromatic vinyl compound and a constituent unit formed by an acrylonitrile compound, and the overcoat layer has a thickness that is greater than the thickness of the image recording layer; a method of producing a lithographic printing plate using the on-press development type lithographic printing plate precursor; and a lithographic printing method using the on-press development type lithographic printing plate precursor.

Description

On-press development type planographic printing plate precursor, method of preparing planographic printing plate, and planographic printing method

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

In general, a lithographic printing plate is composed of an oleophilic image area that receives ink during a printing process and a hydrophilic non-image area that receives fountain solution. Lithographic printing utilizes the property that water and oil-based ink repel each other, so that the lipophilic image area of the lithographic printing plate is an ink receiving area and the hydrophilic non-image area is a dampening water receiving area (ink non-receiving area). In this method, a difference in ink adhesion is caused on the surface of a lithographic printing plate, the ink is deposited only on an image portion, and then the ink is transferred to a printing medium such as paper for printing.
Conventionally, in order to produce this lithographic printing plate, a lithographic printing plate precursor (PS plate) comprising a hydrophilic support and a lipophilic photosensitive resin layer (image recording layer) provided thereon is widely used. Normally, after the lithographic printing plate precursor is exposed through an original such as a lithographic film, the image portion of the image recording layer is left, and the other unnecessary image recording layer is washed with an alkaline developer or an organic solvent. Plate making is performed by a method of dissolving and removing with a solvent and exposing the surface of the hydrophilic support to form a non-image portion to obtain a lithographic printing plate.

Also, due to increasing interest in the global environment, environmental issues relating to waste liquids associated with wet processing such as development processing have been highlighted.
In response to the above-mentioned 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-press development” is performed. That is, after exposure of the lithographic printing plate precursor, conventional development is not carried out, and the lithographic printing plate precursor is directly mounted on a printing machine to remove unnecessary portions of the image recording layer at an initial stage of a normal printing process.
In the present disclosure, a lithographic printing plate precursor that can be used for such on-press development is referred to as an "on-press development type lithographic printing plate precursor".
Conventional lithographic printing plate precursors or printing methods using lithographic printing plate precursors include, for example, those described in Patent Documents 1 to 3.

Patent Document 1 describes a negative type lithographic printing plate precursor having an image recording layer containing a support, 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 hydroxyl group, an alkyl group or an aryl group. i represents an integer of 0 to 3. When i represents an integer of 2 or more, a plurality of R ¹ 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 binding to Ar. ** represents a site binding to Y. Y represents a (m + 1) -valent 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.

U.S. Pat. No. 5,086,067 includes a substrate having an imageable layer thereon, wherein the imageable layer initiates polymerization of the free radically polymerizable groups upon exposure to free radically polymerizable components, imaging radiation. An initiator composition comprising diaryl iodonium borate, an infrared absorbing cyanine dye having a methine chain linking a heterocyclic group, Wherein the methine chain has a chain length of at least 7 carbon atoms, and comprises a primary polymer binder, and the imageable element further comprises an overcoat disposed on the imageable layer; The overcoat describes an imageable element that is comprised primarily of poly (vinyl alcohol) having a degree of hydrolysis of 85% or less.

US Pat. No. 5,047,097 discloses a substrate and a negative-working imageable layer disposed on the substrate, comprising a free-radically polymerizable component and an initiator composition capable of generating free radicals when exposed to imaging radiation. A negative-type image-forming layer containing a substance, a radiation-absorbing agent, and a polymer binder, and an outermost water-soluble overcoat layer directly disposed on the negative-type image-forming layer; One or more film-forming water-soluble polymer binders, and (2) one or more of the above one or more in an amount of at least 1.3 wt% and up to 60 wt% based on the total outermost water-soluble overcoat layer weight. A negative-working lithographic printing plate precursor comprising: an outermost water-soluble overcoat layer containing organic wax particles dispersed in a film-forming water-soluble polymer binder; Is measured from a scanning electron micrograph of the overcoat layer, negative-working lithographic printing plate precursor having an average maximum dimension of 0.7μm at least 0.05μm and maximum are described.

Patent Document 1: JP-A-2017-132227 Patent Document 2: JP-T-2010-529490 JP Patent Document 3: JP-T-2015-519610

In printing using a lithographic printing plate, for example, the plate surface is washed using a plate cleaner or the like during printing. Therefore, an on-press development type lithographic printing plate precursor capable of obtaining a lithographic printing plate excellent in chemical resistance to chemicals such as a plate cleaner is required.
According to the on-press development type lithographic printing plate precursor according to the present disclosure (hereinafter, also simply referred to as “lithographic printing plate precursor”), the present inventors have compared with the lithographic printing plate precursors described in Patent Documents 1 to 3. It has been found that it is possible to further improve the chemical resistance of the resulting lithographic printing plate.

The problem to be solved by the embodiments of the present invention is that an on-press development type lithographic printing plate precursor capable of obtaining a lithographic printing plate excellent in chemical resistance, production of a lithographic printing plate using the on-press development type lithographic printing plate precursor. And a lithographic printing method using the on-press development type lithographic printing plate precursor.

Means for solving the above problems include the following aspects.
<1> having a support, an image recording layer, and an overcoat layer in this order;
The image recording layer contains a binder polymer, and an electron donating polymerization initiator,
The binder polymer has a structural unit formed by an aromatic vinyl compound, and a structural unit formed by an acrylonitrile compound,
An on-press development type lithographic printing plate precursor wherein the thickness of the overcoat layer is larger than the thickness of the image recording layer.
<2> 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 in the image recording layer is more than 0% by mass and 400% by mass or less. An on-press development type lithographic printing plate precursor as described in 1>.
<3> The on-press development type lithographic printing plate precursor according to <1> or <2>, wherein the overcoat layer contains a water-soluble polymer.
<4> The on-press development type lithographic printing plate precursor according to <3>, wherein the water-soluble polymer contains polyvinyl alcohol having a saponification degree of 50% or more.
<5> The on-press development type lithographic printing plate precursor as described in any one of <1> to <4> above, wherein the electron donating polymerization initiator is a borate compound.
<6> The on-press development type lithographic printing plate precursor as described in any one of <1> to <5> above, wherein the electron donating polymerization initiator is a tetraaryl borate compound.
<7> The on-press development type lithographic printing plate precursor as described in any one of <1> to <6> above, wherein the electron donating polymerization initiator is a tetraphenylborate compound.
<8> The on-press development type lithographic printing plate precursor as described in any one of the above items <1> to <7>, wherein the highest occupied orbit of the electron donating polymerization initiator is −6.0 eV or more.
<9> The on-press development type lithographic printing plate precursor as described in any one of <1> to <8> above, wherein the image recording layer further contains an electron-accepting polymerization initiator.
<10> The on-press development type lithographic printing plate precursor as described in <9> above, wherein the electron-accepting polymerization initiator is an onium compound.
<11> The on-press development type lithographic printing plate precursor as described in <9> or <10> above, wherein the electron-accepting polymerization initiator has a minimum free orbit of −3.0 eV or less.
<12> The on-press development type lithographic plate according to any one of <9> to <11>, wherein the electron-accepting polymerization initiator and the electron-donating polymerization initiator form a salt. Printing plate original.
<13> On-press development type lithographic printing as described in any one of the above items <9> to <12>, comprising an iodonium borate compound as the electron-accepting polymerization initiator and the electron-donating polymerization initiator. Original version.
<14> The on-press development type lithographic printing plate precursor according to any one of <1> to <13>, wherein the binder polymer further has a structural unit formed of N-vinylpyrrolidone.
<15> The on-press development type lithographic printing plate precursor according to any one of <1> to <14> above, wherein the image recording layer further contains an infrared absorbent.
<16> The on-press development type lithographic printing plate precursor as described in <15> above, wherein the infrared absorber is an infrared absorber that is decomposed by infrared exposure.
<17> The on-press development type lithographic printing plate precursor as described in <15> or <16> above, wherein the infrared absorber is an infrared absorber that is decomposed by heat, electron transfer, or both due to infrared exposure.
<18> The on-press development type lithographic printing plate precursor as described in any one of the above <15> to <17>, wherein the infrared absorbent is a cyanine dye.
<19> The on-press development type lithographic printing plate precursor according to any one of <15> to <18>, wherein the infrared absorbent is a compound represented by the following formula 1.

In Formula 1, R ¹ represents a group capable of cleaving the R ¹ -L bond by infrared exposure, and R ₁₁ to R ₁₈ each independently represent a hydrogen atom, a halogen atom, —Ra, —ORb, —SRc or —NRdRe. And Ra to Re each independently represent a hydrocarbon group, A ₁ and A ₂ and a plurality of R ₁₁ to R ₁₈ may be linked to form a monocyclic or polycyclic ring, and A ₁ and A ₂ Each independently represents an oxygen atom, a sulfur atom or a nitrogen atom; n ₁₁ and n ₁₂ each independently represent an integer of 0 to 5, provided that the sum of n ₁₁ and n ₁₂ is 2 or more; ₁₃ and n ₁₄ each 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 neutralizer. Represents a counter ion.

<20> R ¹ in the above formula 1, the on-press development type lithographic printing plate precursor as described in <19> is a group represented by the following formula 2.

In Formula 2, R ^Z represents an alkyl group, and a wavy line represents a bonding site with the group represented by L in Formula 1 above.

<21> a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of the above <1> to <20>,
Supplying at least one selected from the group consisting of a printing ink and a fountain solution on a printing press to remove the image recording layer in the non-image area.
<22> a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of the above <1> to <20>,
A step of providing a lithographic printing plate by supplying at least one selected from the group consisting of printing ink and fountain solution and removing the image recording layer of the non-image portion on a printing press,
Printing with the obtained lithographic printing plate.

According to the embodiment of the present invention, an on-press development type lithographic printing plate precursor capable of obtaining a lithographic printing plate excellent in chemical resistance, a method for producing a lithographic printing plate using the on-press development type lithographic printing plate precursor, and A planographic printing method using the on-press development type planographic printing plate precursor can be provided.

Hereinafter, the content of the present disclosure will be described in detail. The description of the components described below may be made based on typical embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.
In this specification, “to” indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit and the upper limit.
Further, in the notation of a group (atomic group) in this specification, the notation of not indicating substituted or unsubstituted includes not only a group having no substituent but also a group having a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In the present specification, “(meth) acryl” is a term used in a concept including both acryl and methacryl, and “(meth) acryloyl” is a term used as a concept including both acryloyl and methacryloyl. It is.
In addition, the term “step” in the present specification is not limited to an independent step, and even if it cannot be clearly distinguished from other steps, the term is used as long as the intended purpose of the step is achieved. included. In the present disclosure, “mass%” and “weight%” have the same meaning, and “mass part” and “part by weight” have the same meaning.
Unless particularly limited, each component in the composition or each constituent unit in the polymer in the present disclosure may be included alone or in combination of two or more. .
Further, in the present disclosure, the amount of each component in the composition, or each constituent unit in the polymer, each component in the composition, or a plurality of substances or constituent units corresponding to each constituent unit in the polymer are present In this case, unless otherwise specified, it refers to the total amount of the corresponding plural substances present in the composition or the corresponding plural structural units present in the polymer.
Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.
In addition, columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) are used for the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the present disclosure unless otherwise specified. It is a molecular weight detected by a gel permeation chromatography (GPC) analyzer using a solvent THF (tetrahydrofuran) and a differential refractometer and converted using polystyrene as a standard substance.
In the present disclosure, the term “lithographic printing plate precursor” includes not only the lithographic printing plate precursor but also a discarded plate precursor. Further, the term “lithographic printing plate” includes not only a lithographic printing plate precursor but also a lithographic printing plate produced through operations such as exposure and development, if necessary, as well as a discarded plate. In the case of a discarded plate master, the operations of exposure and development are not necessarily required. The discarded plate is a lithographic printing plate precursor to be attached to an unused plate cylinder, for example, when printing a part of the paper surface in monochrome or two colors in color newspaper printing.
In the present disclosure, “*” in a chemical structural formula represents a bonding position with another structure.
Hereinafter, the present disclosure will be described in detail.

(On-press development type lithographic printing plate precursor)
The on-press development type lithographic printing plate precursor according to the present disclosure has a support, an image recording layer, and an overcoat layer in this order, and the image recording layer comprises a binder polymer, and an electron donating polymer. Including an initiator, the binder polymer has a structural unit formed by an aromatic vinyl compound, and a structural unit formed by an acrylonitrile compound, and the film thickness of the overcoat layer is a film of the image recording layer. Thicker than thick.

As a result of intensive studies by the present inventors, it has been found that, by employing the above-described configuration, a lithographic printing plate precursor from which a lithographic printing plate having excellent chemical resistance can be obtained can be provided.
The detailed mechanism for obtaining the above effects is unknown, but is presumed as follows.
The lithographic printing plate precursor according to the present disclosure includes an overcoat layer having a thickness greater than that of an image recording layer, including an electron donating polymerization initiator. Thereby, the polymerization efficiency of the radically polymerizable compound in the exposed portion is improved, and the strength of the film in the image area obtained after development is improved, so that the chemical resistance is considered to be improved.
Further, the lithographic printing plate precursor according to the present disclosure includes 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”). Including. The chemical resistance is further improved by the synergistic effect of including all of the specific binder polymer, the overcoat layer, and the electron donating polymerization initiator, but the mechanism is not clear.

The lithographic printing plate precursor described in Patent Document 1 or 2 does not contain a specific binder polymer, and there is room for further improvement in chemical resistance.
The lithographic printing plate precursor described in Patent Document 3 has no description or suggestion that it has an overcoat layer having a thickness greater than that of the image recording layer, and is poor in chemical resistance.

According to the lithographic printing plate precursor according to the present disclosure, it is considered that a lithographic printing plate excellent in printing durability is easily obtained. This is presumed to be due to the above-mentioned improvement in polymerization efficiency, the above-mentioned synergistic effect, and the like.
In a lithographic printing plate, the fact that the number of printable plates is large is referred to as "excellent in printing durability". Furthermore, according to the lithographic printing plate precursor according to the present disclosure, it is considered that a lithographic printing plate excellent in ink deposition property (hereinafter, also simply referred to as “deposition property”) is easily obtained. This is presumably due to the inclusion of the specific binder polymer described above, the synergistic effect described above, and the like.
According to the lithographic printing plate precursor according to the present disclosure, it is considered that a lithographic printing plate precursor excellent in on-press developability is easily obtained. This is presumed to be due to the fact that the non-image portion sticks to the ink roller during the on-press development and is easily removed (ink tack development) by including the specific binder polymer, and the synergistic effect described above. .

The lithographic printing plate precursor according to the present disclosure includes a specific binder polymer, the overcoat layer, and the electron donating polymerization initiator, and includes all the requirements for printing durability, chemical resistance, and inking property. Further, it is considered that both the on-press developability and the on-press developability are excellent. If even one of the above requirements is missing, it is likely that at least one of these effects will be reduced.
In general, in an on-press development type lithographic printing plate, by improving the chemical resistance obtained by lowering the solubility of the image area by the agent such as the plate cleaner, or by improving the resistance to ink as an agent. It is necessary to achieve both the printing durability obtained and the ink inking property obtained by improving the affinity for the ink, or the on-press developability obtained by the unexposed part having an excellent affinity for the ink. It is considered difficult, and the lithographic printing plate precursor according to the present disclosure is considered to be very useful in that both of these can be achieved.
Hereinafter, the details of each component in the lithographic printing plate precursor according to the present disclosure will be described.

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

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

<Image recording layer>
The lithographic printing plate precursor 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 viewpoints of printing durability and photosensitivity.
The image recording layer used in the present disclosure preferably further contains an electron-accepting polymerization initiator from the viewpoints of printing durability 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 include an acid coloring agent in order to confirm the exposed portion before development.
In the lithographic printing plate precursor according to the present disclosure, 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 fountain solution and printing ink from the viewpoint of on-press developability. .
Hereinafter, details of each component contained in the image recording layer will be described.

(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 that is not in a particle shape, and polymer particles described below are not included in the specific binder polymer in the present disclosure.
The specific binder polymer has a structural unit formed by an aromatic vinyl compound and a structural unit formed by an acrylonitrile compound.

-Structural unit formed by aromatic vinyl compound-
The specific binder polymer has a structural unit formed by 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 a styrene compound and a vinyl naphthalene compound. A styrene compound is preferable, and styrene is more preferable.
Examples of the styrene compound include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene. Styrene is preferred.
Examples of the vinyl naphthalene compound include 1-vinyl naphthalene, methyl-1-vinyl naphthalene, β-methyl-1-vinyl naphthalene, 4-methyl-1-vinyl naphthalene, and 4-methoxy-1-vinyl naphthalene. -Vinyl naphthalene is preferred.

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

In Formula A1, R ^A1 and R ^A2 each independently represent a hydrogen atom or an alkyl group, Ar represents an aromatic ring group, R ^A3 represents a substituent, and n represents an integer equal to or less than the maximum number of substituents of Ar. .
In formula A1, R ^A1 and R ^A2 are each independently preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and both are hydrogen atoms. Is more preferred.
In Formula A1, Ar is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring.
In the formula A1, R ^A3 is preferably an alkyl group or an alkoxy group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and a methyl group or a methoxy group. Is more preferred.
In the formula A1, when the R ^A3 there are a plurality, plural of R ^A3 may be the same or may be different.
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 from 15% by mass to 85% by mass, and more preferably from 30% by mass to 70% by mass based on the total mass of the specific binder polymer. More preferably, there is.

-Structural unit formed by acrylonitrile compound-
The specific binder polymer has a structural unit formed by an acrylonitrile compound.
Examples of the acrylonitrile compound include (meth) acrylonitrile and the like, with acrylonitrile being preferred.

構成 Moreover, as a structural unit formed of an acrylonitrile compound, a structural unit represented by the following formula B1 is preferably exemplified.

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

The content of the structural unit formed by the acrylonitrile compound in the specific binder polymer is preferably from 15% by mass to 85% by mass, and more preferably from 30% by mass to 70% by mass, based on the total mass of the specific binder polymer. Is more preferred.

-Structural unit formed by N-vinyl heterocyclic compound-
The specific binder polymer preferably further has a structural unit formed of an N-vinyl heterocyclic compound from the viewpoint of printing durability and chemical resistance.
Examples of the N-vinyl heterocyclic compound include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylcaprolactam. Vinyl imidazole is preferred, with N-vinylpyrrolidone being preferred.

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

In the formula C1, Ar ^N represents a heterocyclic structure containing a nitrogen atom, a nitrogen atom in Ar ^N is bonded to the carbon atoms indicated by *.
In 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, or an imidazole ring, and more preferably a pyrrolidone ring. Is more preferred.
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 from 5% by mass to 50% by mass, and more preferably from 10% by mass to 40% by mass, based on the total mass of the specific binder polymer. % Is more preferable.

-Structural unit having an ethylenically unsaturated group-
The specific binder polymer may further have a structural unit having an ethylenically unsaturated group.
Examples of the ethylenically unsaturated group include, but are not particularly limited to, a vinyl group, an allyl group, a vinylphenyl group, a (meth) acrylamide group, and a (meth) acryloyloxy group. ) An acryloyloxy group is preferred.
The constituent 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 in which a compound having an epoxy group and an ethylenically unsaturated group (eg, glycidyl methacrylate) is reacted with a polymer into which a structural unit having a carboxy group such as methacrylic acid is introduced, Such as a method in which a compound having an isocyanate group and an ethylenically unsaturated group (such as 2-isocyanatoethyl methacrylate) is reacted with a polymer into which a structural unit having a group having an active hydrogen such as has been introduced. .
Further, the structural unit having an ethylenically unsaturated group may be obtained by reacting a polymer having a structural unit having an epoxy group such as glycidyl (meth) acrylate 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 constituent unit having an ethylenically unsaturated group may be introduced into the specific binder polymer by using, for example, a monomer having a partial structure represented by the following formula d1 or d2. Specifically, for example, after polymerization using at least the above monomer, an ethylenically unsaturated group is formed by a elimination reaction using a base compound on a partial structure represented by the following formula d1 or the following formula d2. By doing so, the structural unit having an ethylenically unsaturated group is introduced into the specific binder polymer.

In the formula d1 and wherein d2, ^{R d} represents a hydrogen atom or an alkyl group, ^{A d} represents a halogen atom, ^{X d} is -O- or -NR ^N - represents, ^{R N} represents a hydrogen atom or an alkyl group , * Represents a binding site to another structure.
In the formulas d1 and d2, R ^d is preferably a hydrogen atom or a methyl group.
In the formula d1 and wherein d2, A ^d is a chlorine atom, a bromine atom, or preferably a iodine atom.
In the formulas d1 and d2, X ^d is preferably -O-. When X ^d represents —NR ^N —, R ^N 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 bond or a divalent linking group, L ^D2 represents an m + 1-valent linking group, X ^D1 and X ^D2 each independently represent -O- or -NR ^N- , R ^N represents a hydrogen atom or an alkyl group, R ^D1 and R ^D2 each independently represent a hydrogen atom or a methyl group, and m represents an integer of 1 or more.

In the formula D1, L ^D1 is preferably a single bond. When ^LD1 represents a divalent linking group, an alkylene group, an arylene group or a divalent group in which two or more of these groups are bonded is preferable, and an alkylene group having 2 to 10 carbon atoms or a phenylene group is more preferable.
In Formula D1, L ^D2 is preferably a group represented by any of Formulas D2 to D6.
In Formula D1, X ^D1 and X ^D2 are preferably both —O—. When at least one of X ^D1 and X ^D2 represents —NR ^N —, R ^N is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and more preferably a hydrogen atom.
In the formula D1, R ^D1 is preferably a methyl group.
In the formula D1, at least one of m R ^D2 is preferably a methyl group.
In the formula D1, m is preferably an integer of 1 to 4, more preferably 1 or 2, and still more preferably 1.

In 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 to X ^{D1 in} Formula D1; Represents a binding site to ^{XD2 in} Formula D1.

In Formula D3, ^LD3 is preferably an alkylene group, an arylene group, or a group having two or more of these bonded, and is preferably an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group having two or more of these bonded. More preferred.
In formula D4, ^LD4 is preferably an alkylene group, an arylene group, or a group having two or more of these bonded, and preferably an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group having two or more of these bonded. More preferred.
In Formula D5, ^LD5 is preferably an alkylene group, an arylene group, or a group having two or more of these bonded, and is preferably an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group having two or more of these bonded. More preferred.
In Formula D6, ^LD6 is preferably an alkylene group, an arylene group, or a group having two or more of these bonded, and is preferably an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group having two or more of these bonded. More preferred.
In Formula D7, ^LD7 is preferably an alkylene group, an arylene group, or a group in which two or more thereof are bonded, and is preferably an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a group in which two or more thereof are bonded. More preferred.

具体 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, each 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 from 5% by mass to 60% by mass, and more preferably from 10% by mass to 30% by mass, based on the total mass of the specific binder polymer. Is more preferable.

-Structural unit having acidic group-
Although the specific binder polymer may contain a constituent unit having an acidic group, it is preferable that the specific binder polymer does not contain a constituent unit having an acidic group from the viewpoints of on-press developability and ink adhesion.
Specifically, the content of the structural unit having an acidic group in the specific binder polymer is preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less. preferable. The lower limit of the content is not particularly limited, and may be 0% by mass.
Further, the acid value of the specific binder polymer is preferably 160 mgKOH / g or less, more preferably 80 mgKOH / g or less, and further preferably 40 mgKOH / g or less. The lower limit of the acid value is not particularly limited, and may be 0 mgKOH / g.
In the present disclosure, the acid value is determined by a measuring method based on JIS K0070: 1992.

-Structural unit having a hydrophobic group-
The specific binder polymer may contain a structural unit containing a hydrophobic group from the viewpoint of ink adhesion.
Examples of the hydrophobic group include an alkyl group, an aryl group, and an aralkyl group.
As the structural unit containing a 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 a structural unit formed of an alkyl (meth) acrylate compound is preferred. Is more preferable.
The alkyl (meth) acrylate compound preferably has 1 to 10 carbon atoms in the alkyl group. 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. Is 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. Preferred examples of the aryl (meth) acrylate compound include phenyl (meth) acrylate.
The aralkyl (meth) acrylate compound preferably has 1 to 10 carbon atoms in the alkyl group. 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, and more preferably a phenyl group. As an aralkyl (meth) acrylate compound, benzyl (meth) acrylate is preferably exemplified.

The content of the structural unit having a hydrophobic group in the specific binder polymer is preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 30% by mass, based on the total mass of the specific binder polymer. More preferred.

-Structural unit having a hydrophilic group-
The specific binder polymer may include a structural unit having a hydrophilic group from the viewpoint of improving printing durability, chemical resistance, and on-press developability.
Examples of the hydrophilic group include —OH, —CN, —CONR ¹ R ² , and —NR ² COR ¹ (R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group. R ¹ and R ² may combine to form a ring.) —NR ³ R ⁴ , —N ⁺ R ³ R ⁴ R ⁵ X ⁻ (R ³ to R ⁵ each independently have a carbon number. represents an alkyl group of 1 ~ 8, X ^- represents a counter anion), include groups represented by the following formula PO.
Among these hydrophilic groups, a group represented by —CONR ¹ R ² or the formula PO is preferable, and a group represented by the formula PO is more preferable.

In the formula PO, L ^P each independently represents an alkylene group, R ^P represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 100.
Wherein PO, L ^P is each independently represents preferably an ethylene group, a 1-methylethylene or 2-methylethylene group, more preferably an ethylene group.
Wherein PO, R ^P is preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, a hydrogen atom or a C 1-4 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, 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 5% by mass to 60% by mass, and more preferably 10% by mass to 30% by mass based on the total mass of the specific binder polymer. More preferred.

-Other structural units-
The specific binder polymer may further contain other constituent units. As other structural units, structural units other than the above-described structural units can be contained without any particular limitation, and examples thereof include structural units formed of an acrylamide compound, a vinyl ether compound, and 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, N, N′-dimethyl (Meth) acrylamide, N, N'-diethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxypropyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide and the like can be mentioned.
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, cyclohexylmethyl vinyl ether, and 4-methylcyclohexyl. Methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl Ether, tetrahydrofurfuryl 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, chloro Examples include ethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, and the like.

含有 The content of the other constituent units in the specific binder polymer is preferably from 5% by mass to 50% by mass, more preferably from 10% by mass to 30% by mass, based on the total mass of the specific binder polymer.

-Method for producing specific binder polymer-
The method for producing the specific binder polymer is not particularly limited, and can be produced by a known method.
For example, a styrene compound, an acrylonitrile compound, and if necessary, the N-vinyl heterocyclic compound, the compound used to form the structural unit having an ethylenically unsaturated group, and the compound used to form the structural unit having an acidic group And at least one compound selected from the group consisting of a compound used for forming the structural unit having the hydrophobic group, and a compound used for forming the other structural unit, using a known method. Obtained by polymerization with

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

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

In the above specific examples, the content ratio of each structural unit can be appropriately changed according to the preferable range of the content of each structural unit described above.
In addition, the weight average molecular weight of each compound shown in the above specific examples can be appropriately changed according to the preferable range of the weight average molecular weight of the specific binder polymer.

-Content-
The image recording layer may contain one specific binder polymer alone, or two or more specific binder polymers 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 from 5% by mass to 95% by mass, more preferably from 7% by mass to 80% by mass, and preferably from 10% by mass to 60% by mass. More preferred.

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

Among these electron donating polymerization initiators, the image recording layer preferably contains a borate compound. As the borate compound, a tetraaryl borate compound or a monoalkyltriaryl borate compound is preferable, and from the viewpoint of the stability of the compound, a tetraaryl borate compound is more preferable, and a tetraphenyl borate compound is particularly preferable.
The counter cation of 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 tetraphenyl borate.

Further, the highest occupied orbital (HOMO) of the electron donating polymerization initiator used in the present disclosure is preferably −6.00 eV or more, and −5.95 eV or more from the viewpoint of chemical resistance and printing durability. Is more preferable, and more preferably −5.93 eV or more.
Further, the upper limit is preferably -5.00 eV or less, more preferably -5.40 eV or less.

In the present disclosure, the calculation of the highest occupied orbit (HOMO) and the lowest unoccupied orbit (LUMO) is performed by the following method.
First, the counter anion in the compound to be calculated is ignored.
Structure optimization was performed using DFT (B3L) using quantum chemical calculation software Gaussian09.
YP / 6-31G (d)).
The MO (molecular orbital) energy calculation is performed by DFT (B3LYP / 6-31 + G (d, p) / CPCM (solvent = methanol)) using the structure obtained by the above structure optimization.
The MO energy Ebare (unit: hearttree) obtained by the MO energy calculation is converted into Escaled (unit: eV) used as a value of HOMO and LUMO in the present disclosure by the following formula.
Escaled = 0.823168 × 27.2114 × Ebare-1.07634
Note that 27.2114 is simply a coefficient for converting hearttree to eV, 0.823168 and -1.07634 are adjustment coefficients, and the HOMO and LUMO of the compound to be calculated are actually measured values. Set to fit.

Preferred specific examples of the electron donating polymerization initiator include B-1 to B-8 and other compounds, but needless to say, the invention is not limited thereto. 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 ⁺ , and N ⁺ (Bu) ₄ . Bu represents an n-butyl group.
Further, as a counter cation represented by Z, an onium ion in an electron-accepting polymerization initiator described below is also preferably exemplified.

The electron donating polymerization initiator may be used alone or in combination of two or more.
The content of the electron donating polymerization initiator is preferably 0.01% by mass to 30% by mass, more preferably 0.05% by mass to 25% by mass, and more preferably 0.1% by mass, based on the total mass of the image recording layer. -20% by mass is more preferred.

(Polymerizable compound)
The image recording layer in the present disclosure preferably contains a polymerizable compound.
In the present disclosure, even if it is a compound having polymerizability, the above-mentioned specific binder polymer, polymer particles described below, and a compound corresponding to a binder polymer other than the specific binder described below are not applicable to the polymerizable compound. I do.
The molecular weight of the polymerizable compound (in the case of having a molecular weight distribution, the weight average molecular weight) 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 radical polymerizable compound or a cationic polymerizable compound, but may be an addition polymerizable compound having at least one ethylenically unsaturated bond (ethylenic compound). Unsaturated compounds). 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, ie, a dimer, trimer or oligomer, or a mixture thereof.

Examples of the monomer include unsaturated carboxylic acids (eg, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.) and esters and amides thereof. Esters of an acid and a polyhydric alcohol compound and amides of an unsaturated carboxylic acid and a polyamine 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, A dehydration-condensation reaction product with a functional carboxylic acid is also preferably used. Further, an isocyanate group, an unsaturated carboxylic acid ester or amide having an electrophilic substituent such as an epoxy group and an amide and a monofunctional or polyfunctional alcohol, an amine, an addition reaction product with a thiol, further a halogen atom, Substitution products of unsaturated carboxylic esters or amides having a leaving 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 described in JP-T-2006-508380, JP-A-2002-287344, JP-A-2008-256850, JP-A-2001-342222, JP-A-9-179296, and JP-A-9-179297. JP-A-9-179298, JP-A-2004-294935, JP-A-2006-243493, JP-A-2002-275129, JP-A-2003-64130, JP-A-2003-280187, It is described in Japanese Unexamined Patent Publication No. Hei 10-333321.

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

Urethane-based addition-polymerizable compounds produced by an addition reaction between an isocyanate and a hydroxy group are also suitable. Specific examples thereof include, for example, two molecules per molecule described in JP-B-48-41708. A vinyl urethane compound containing two or more polymerizable vinyl groups in one molecule obtained by adding a hydroxyl group-containing vinyl monomer represented by the following formula (M) to a polyisocyanate compound having two or more isocyanate groups: And the like.
CH ₂ ＣC (R ^M4 ) COOCH ₂ CH (R ^M5 ) OH (M)
In the formula (M), R ^M4 and R ^M5 each independently represent a hydrogen atom or a methyl group.

Also, urethane acrylates described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-2003-344997, and JP-A-2006-65210 are disclosed. Ethylene described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417, JP-B-62-39418, JP-A-2000-250211, and JP-A-2007-94138. Urethane compounds having an oxide skeleton, and urethane compounds having a hydrophilic group described in US Pat. No. 7,153,632, JP-T 8-505958, JP-A 2007-293221, and JP-A 2007-293223. Classes are also suitable.

Details of the method of use, such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount added, can be arbitrarily set.
The content of the polymerizable compound is preferably from 5% by mass to 75% by mass, more preferably from 10% by mass to 70% by mass, and more preferably from 15% by mass to 60% by mass, based on the total mass of the image recording layer. More preferably, it is mass%.
Further, the content of the specific binder polymer with respect to the total mass of the polymerizable compound in the image recording layer is preferably more than 0% by mass and 400% by mass or less, and more preferably 25% by mass to 300% by mass. More preferably, it is more preferably from 50% by mass to 200% by mass.
In the image recording layer, the specific binder polymer and the polymerizable compound preferably 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 to the total mass of the polymerizable compound 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 initiating species such as a radical or a cation by the energy of light, heat or both, and is a known thermal polymerization initiator, having 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.
In addition, the electron-accepting polymerization initiator is preferably an infrared-sensitive 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, (f) an azide compound, (g) ) Hexaarylbiimidazole compounds, (i) disulfone compounds, (j) oxime ester compounds, and (k) onium compounds.

As the organic halide (a), for example, compounds described in paragraphs 0022 to 0023 of JP-A-2008-195018 are preferable.
As the carbonyl compound (b), for example, compounds described in paragraph 0024 of JP-A-2008-195018 are preferable.
As the azo compound (c), for example, azo compounds described in JP-A-8-108621 can be used.
As the organic peroxide (d), for example, compounds described in paragraph 0025 of JP-A-2008-195018 are preferable.
As the metallocene compound (e), for example, compounds described in paragraph 0026 of JP-A-2008-195018 are preferable.
Examples of the (f) azide compound include compounds such as 2,6-bis (4-azidobenzylidene) -4-methylcyclohexanone.
As the (g) hexaarylbiimidazole compound, for example, compounds described in paragraph 0027 of JP-A-2008-195018 are preferable.
Examples of the (i) disulfone compound include compounds described in JP-A-61-166544 and JP-A-2002-328465.
As the oxime ester compound (j), for example, 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 durability, iodonium salt compounds, sulfonium salt compounds or azinium salt compounds are preferable, iodonium salt compounds or sulfonium salt compounds are more preferable, and iodonium salt compounds are 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, particularly an electron donating group, for example, a diphenyliodonium salt compound substituted with an alkyl group or an alkoxyl group is more preferable, and an asymmetric diphenyliodonium salt compound is preferable. . As specific examples, 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 = hexafluorophosphate, bis ( -t- butylphenyl) iodonium hexafluorophosphate and the like.

As an example of the sulfonium salt compound, a triarylsulfonium salt compound is preferable, and in particular, 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. Triarylsulfonium salt compounds in which the total number of substitution of halogen atoms on the ring is 4 or more are more preferred. As specific examples, triphenylsulfonium = hexafluorophosphate, triphenylsulfonium = benzoylformate, bis (4-chlorophenyl) phenylsulfonium = benzoylformate, bis (4-chlorophenyl) -4-methylphenylsulfonium = tetrafluoro Borate, tris (4-chlorophenyl) sulfonium = 3,5-bis (methoxycarbonyl) benzenesulfonate, tris (4-chlorophenyl) sulfonium = hexafluorophosphate, tris (2,4-dichlorophenyl) sulfonium = hexafluorophos Fart.

The counter anion of the iodonium salt compound and the sulfonium salt compound is preferably a sulfonamide anion or a sulfonimide anion, and more preferably a sulfonimide anion.
As the sulfonamide anion, an arylsulfonamide anion is preferable.
As the sulfonimide anion, a bisarylsulfonimide anion is preferable.
Specific examples of the sulfonamide anion or the sulfonimide 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.

One preferred embodiment of 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 above-described electron donating polymerization initiator. More preferably, an iodonium borate compound in which an iodonium cation (for example, di-p-tolyliodonium cation) in an iodonium salt compound described below and a borate anion in the above-described electron donating polymerization initiator form a salt, is mentioned. Can be
In the present disclosure, when the image recording layer contains onium ions and the above-mentioned anion in the electron donating polymerization initiator, the image recording layer contains an electron accepting polymerization initiator and an electron donating polymerization initiator.

The lowest unoccupied orbit (LUMO) of the electron-accepting polymerization initiator is preferably −3.00 eV or less, more preferably −3.02 eV or less, from the viewpoint of chemical resistance and printing durability.
Further, the lower limit is preferably -3.80 eV or more, more preferably -3.60 eV or more.

The content of the electron-accepting polymerization initiator is preferably from 0.1% by mass to 50% by mass, more preferably from 0.5% by mass to 30% by mass, based on the total mass of the image recording layer. It is particularly preferable that the content be 0.8% by mass to 20% by mass.

(Infrared absorber)
The image recording layer preferably contains an infrared absorbing agent.
Infrared absorbents include pigments and dyes.
As the dye used as the infrared absorber, commercially available dyes and known dyes described in literatures such as "Dye Handbook" (edited by The Society of Synthetic Organic Chemistry, Japan, 1970) can be used. Specifically, azo dyes, metal complex salt azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinone imine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, dyes such as metal thiolate complexes Is mentioned.
Particularly preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further, cyanine dyes and indolenine cyanine dyes are exemplified. Among them, cyanine dyes are particularly preferred.

Specific examples of the cyanine dye include the compounds described in paragraphs 0017 to 0019 of JP-A-2001-133969, paragraphs 0016 to 0021 of JP-A-2002-023360, and paragraphs 0012 to 0037 of JP-A-2002-040638. The compounds described in paragraphs 0034 to 0041 of JP-A-2002-278057, and the compounds described in paragraphs 0080 to 008 of JP-A-2008-195018, particularly preferably paragraph 0035 of JP-A-2007-90850 are preferred. And the compounds described in paragraphs 0105 to 0113 of JP-A-2012-206495.
Further, 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, compounds described in paragraphs 0072 to 0076 of JP-A-2008-195018 are preferable.

Further, it is preferable that the infrared absorbing agent is an infrared absorbing agent that decomposes upon exposure to infrared light (hereinafter also referred to as “degradable infrared absorbing agent”).
As the infrared absorbing agent, by using an infrared absorbing agent dye that decomposes by infrared exposure, the infrared absorbing agent or a decomposition product thereof promotes polymerization, and a highly polar film is obtained by using a specific binder polymer. Further, it is presumed that the decomposed product of the infrared absorber and the binder polymer interact with each other, so that the printing durability (UV printing durability) is excellent even when a UV ink is used. .
The decomposable infrared absorbent is preferably an infrared absorbent that has a function of absorbing infrared light, decomposing it, and developing color by infrared exposure. Here, the term "coloring" means that the visible light region (wavelength region of 400 nm or more and less than 750 nm) has almost no absorption before infrared exposure, but the visible light region absorbs by infrared exposure. It also includes the case where the absorption in the lower wavelength region becomes longer in the visible light region.
Hereinafter, a colored compound formed by the decomposable infrared absorber absorbing infrared rays upon exposure to infrared light and decomposing the same is also referred to as a “color former of the decomposable infrared absorber”.
Further, it is preferable that the decomposable infrared absorbent has a function of absorbing infrared light by infrared exposure and converting the absorbed infrared light into heat.
The decomposable infrared absorbent may be any as long as it absorbs and decomposes at least a part of light in an infrared wavelength range (wavelength 750 nm to 1 mm), and an infrared ray having a maximum absorption in a wavelength range of 750 nm to 1,400 nm. Preferably it is an absorbent.

The decomposable infrared absorbent is preferably an infrared absorbent that decomposes due to heat due to infrared exposure, electron transfer or both, more preferably an infrared absorbent that decomposes due to electron transfer due to infrared exposure. preferable. Here, “decomposed by electron transfer” means that the electrons excited from the HOMO (highest occupied orbit) of the decomposable infrared absorbent to the LUMO (lowest unoccupied orbit) of the decomposable infrared absorbent by infrared exposure are converted into an electron accepting group (LUMO) in the molecule. Electron transfer to a group having a potential close to that of the molecule), and decomposition occurs accordingly.

As the decomposable infrared absorbing agent, a cyanine dye that decomposes by infrared exposure is preferable from the viewpoints of color developability and UV printing durability of the resulting lithographic printing plate.
The above-mentioned infrared absorber is more preferably a compound represented by the following formula 1 from the viewpoints of color developability and UV printing durability of the resulting lithographic printing plate.

When the cyanine dye represented by Formula 1 is exposed to infrared light, the R ¹ -L bond is cleaved, and L becomes ＯO, ＳS, or ＮＲNR ^10, and the color forming body of a decomposable infrared absorbent Is formed. R ¹ is separated to form a radical form or an ionic form. These contribute to the polymerization of the polymerizable compound contained in the image recording layer.

In Formula 1, R ₁₁ to R ₁₈ are each independently preferably a hydrogen atom, —Ra, —ORb, —SRc, or —NRdRe.
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, branched, or have a ring structure.

R ₁₁ to R ₁₄ in Formula 1 are each independently preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group, and further preferably a hydrogen atom.
Further, R ₁₁ and R ₁₃ bonded to the carbon atom bonded to the carbon atom bonded to L are preferably an alkyl group, and more preferably the two are linked to form a ring. The formed ring is preferably a 5-membered ring or a 6-membered ring, more preferably a 5-membered ring.
It is preferable that R ₁₂ bonded to the carbon atom bonded to A ₁ ⁺ and R ₁₄ bonded to the carbon atom bonded to A ₂ be bonded to R ₁₅ and R ₁₇ to form a ring, respectively.

R ₁₅ in Formula 1 is preferably a hydrocarbon group. Further, it is preferable that R ₁₅ and R ₁₂ bonded to the carbon atom bonded to A ₁ ⁺ are connected to form a ring. The ring formed is preferably an indolium ring, a pyrylium ring, a thiopyrylium ring, a benzoxazoline ring or a benzimidazoline ring, and more preferably an indolium ring 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 connected to form a ring. The ring formed is preferably an indole ring, a pyran ring, a thiopyran ring, a benzoxazole ring, or a benzimidazole ring, and more preferably an indole ring from the viewpoint of color development.
R ₁₅ and R ₁₇ in Formula 1 are preferably the same group, and when each forms a ring, it is preferable to form the same ring.

R ₁₆ and R ₁₈ in Formula 1 are preferably the same group.
Further, from the viewpoint of improving the water solubility of the compound represented by Formula 1, R ₁₆ and R ₁₈ are each independently preferably an alkyl group having a (poly) oxyalkylene group or an alkyl group having an anionic structure, and an alkoxyalkyl An alkyl group having a group, a carboxylate group or a sulfonate group is more preferable, and an alkyl group having a terminal sulfonate group is more preferable. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms.
The counter cation having the anion structure may be a cation or A ₁ ⁺ that can be contained in R ¹ -L in Formula 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 or A ₁ ⁺ that can be contained in R ¹ -L in Formula 1, or may be an alkali metal cation or an alkaline earth metal cation.
Further, from the viewpoint of increasing the maximum absorption wavelength of the compound represented by the formula 1 and increasing the color development and printing durability of a lithographic printing plate, R ₁₆ and R ₁₈ each independently represent an alkyl group or an aromatic ring. Preferred is an alkyl group. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and still more preferably a methyl group or an ethyl group. 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, 2-naphthalenylethyl group or 2- (9-anthracenyl) ethyl group is more preferable.

In Formula 1, n ₁₁ and n ₁₂ are preferably the same integer of 0 to 5, more preferably 1 to 3, still more preferably 1 or 2, and particularly preferably 2.

A ₁ and A ₂ in Formula 1 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, and a nitrogen atom is preferable.
A ₁ and A ₂ in Formula 1 are preferably the same atom.

Za in Formula 1 represents a counter ion that neutralizes the charge. In the case of representing an anionic species, sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroantimonate ion, p-toluenesulfonate ion, perchlorate ion and the like can be mentioned, and hexafluorophosphate ion Or a hexafluoroantimonate ion is preferable. When representing a cationic species, an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, a sulfonium ion, and the like are mentioned, and a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion or a sulfonium ion is preferable, and a sodium ion, Potassium ions or ammonium ions are more preferred.
R ₁₁ to R ₁₈ and R ¹ -L may have an anion structure or a cation structure. If all of R ₁₁ to R ₁₈ and R ¹ -L are charge-neutral groups, Za Is a monovalent counter anion. For example, when R ₁₁ to R ₁₈ and R ¹ -L have two or more anion structures, Za can also be a counter cation.
If the cyanine dye represented by Formula 1 has a charge neutral structure in the entire compound, Za does not exist.

In Equation 1, for the radicals R ¹ -L bond by infrared exposure represented by R ¹ is cleaved, as described in detail later.

シア As the decomposable infrared absorbing agent, a cyanine dye represented by the following formula 1-A is more preferable from the viewpoints of color developing properties and UV printing durability of the resulting lithographic printing plate.

In Formula 1-A, R ¹ represents a group capable of cleaving an R ¹ -L bond upon exposure to infrared light, 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 And Ar ¹ and Ar ² each independently represent a group forming a benzene ring or a naphthalene ring, and Y ¹ and Y ² each independently represent an oxygen atom, a sulfur atom, —NR Represents a ^0- or dialkylmethylene group, R ⁰ represents a hydrogen atom, an alkyl group or an aryl group, and R ⁴ and R ⁵ each independently represent an alkyl group, a —CO ₂ M group or a —PO ₃ M ₂ group , M represents a hydrogen atom, a Na atom, a K atom or an onium group, R ⁶ to R ⁹ each independently represent a hydrogen atom or an alkyl group, L represents an oxygen atom, a sulfur atom or -NR ^10- , R ¹⁰ is a hydrogen atom, Represents a alkyl group or an aryl group, Za represents a counter ion for neutralizing the electric charge.

In the formula 1-A, the alkyl group for R ² to R ⁹ and R ⁰ 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 preferred. The alkyl group may be linear, branched, or have a ring structure.
Specifically, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, hexadecyl group, octadecyl Group, eicosyl group, isopropyl group, isobutyl group, s-butyl group, tert-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl And 2-norbornyl groups.
Among the alkyl groups, a methyl group, an ethyl group, a propyl group or a butyl group is preferred.

The alkyl group may have a substituent. Examples of the substituent 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 groups obtained by combining these.

The aryl group for R ⁰ is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and still more preferably an aryl group having 6 to 12 carbon atoms.
The aryl group may have a substituent. Examples of the substituent include 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 obtained by 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-methylthiophenyl group And a phenylthiophenyl group.
Among the aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group or a naphthyl group is preferred.

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

Y ¹ and Y ² each independently represent an oxygen atom, a sulfur atom, —NR ⁰ — or a dialkylmethylene group, preferably —NR ⁰ — or a dialkylmethylene group, and more preferably a dialkylmethylene group.
R ⁰ represents a hydrogen atom, an alkyl group or an aryl group, and is preferably an alkyl group.

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

In the formulas (a1) to (a4), R ^W0 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 R ^W1 represents a carbon atom. ^Represents an alkyl group of the formulas 1 to 12 or —C (＝ O) —R ^W5 , R ^W5 represents an alkyl group of 1 to 12 carbon atoms, and R ^W2 to R ^W4 each independently represent a single bond or 1 carbon atom. Represents up to 12 alkylene groups, and M represents a hydrogen atom, Na atom, K atom or onium group.

In the formula (a1), specific examples of the alkylene group represented by R ^WO include ethylene, n-propylene, isopropylene, n-butylene, isobutylene, n-pentylene, isopentylene, n- Examples include a hexyl group and an isohexyl group, preferably an ethylene group, an n-propylene group, an isopropylene group, and an n-butylene group, and particularly preferably an n-propylene group.
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 a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Group, n-hexyl group, n-octyl group, n-dodecyl group and the like, and methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group and tert-butyl group are preferable, and methyl group, Ethyl groups are more preferred, and methyl groups are particularly preferred.
Alkyl group represented by R ^W5 is the same as defined for the alkyl group represented by R ^W1, preferred embodiments are also the same as the preferred embodiment of the alkyl group represented by R ^W1.

具体 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 formulas, Me represents a methyl group, Et represents an ethyl group, and * represents a binding site.

In the formulas (a2) to (a4), specific examples of the alkylene group represented by R ^W2 to R ^W4 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. An ethylene group and an n-propylene group are particularly preferred.
In the formula (a3), two Ms may be the same or different.

において In the formulas (a2) to (a4), examples of the onium group represented by M include an ammonium group, an iodonium group, a phosphonium group, and a sulfonium group.

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

In Formula 1-A, R ⁴ and R ⁵ are each preferably an unsubstituted alkyl group. Preferably, R ⁴ and R ⁵ are the same group.

R ⁶ to R ⁹ each 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 naphthalene ring may have a substituent. Examples of the substituent include 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. Groups, phosphonic acid groups, and groups obtained by combining them. As the substituent, an alkyl group is preferable.
Further, from the viewpoint of increasing the maximum absorption wavelength of the compound represented by the formula 1-A and improving the color development and the printing durability of the lithographic printing plate, Ar ¹ and Ar ² are each independently a naphthalene ring. Or, a group that forms a benzene ring having an alkyl group or an alkoxy group as a substituent is preferable, a naphthalene ring or a group that forms a benzene ring having an alkoxy group as a substituent is more preferable, and a naphthalene ring or methoxy is preferable. A group forming a benzene ring having a group as a substituent is particularly preferred.

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

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

Za represents a counter ion for neutralizing the charge. However, when 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 necessary. When Za represents an anionic species, sulfonate ion, carboxylate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroantimonate ion, p-toluenesulfonate ion, perchlorate ion and the like can be mentioned. A phosphate ion or hexafluoroantimonate ion is preferred. When Za represents a cationic species, examples thereof include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion or a sulfonium ion, and a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion or a sulfonium ion are preferable, and sodium 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 anion structure or a cation structure, and R ¹ to R ⁹ , R ⁰ , Ar ¹ , Ar ² , If all of Y ¹ and Y ² are charge-neutral groups, Za is a monovalent counter anion, but for example, R ¹ to R ⁹ , R ⁰ , Ar ¹ , Ar ² , Y ¹ and When Y ² has two or more anionic structures, Za can also be a counter cation.

In the above formula 1 and formula 1-A, R ¹ -L bond is described below based on the cleaved by infrared exposure represented by R ^1.
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. And groups represented by any of the following formulas (1-1) to (1-3) are more preferable.

In the formulas (1-1) to (1-7), ● represents a bonding site to an oxygen atom represented by L in the formula 1 or 1-A, and R ²⁰ is each independently a hydrogen atom, Represents an alkyl group, an alkenyl group, an aryl group, -OR ²⁴ , -NR ²⁵ R ²⁶ or -SR ²⁷ ; R ²¹ each independently represents a hydrogen atom, an alkyl group or an 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, wherein R ²³ is an aryl group, an alkenyl group, an alkoxy group or an onium group R ²⁴ to R ²⁷ each independently represent a hydrogen atom, an alkyl group or an aryl group; R ²⁸ represents an alkyl group, an aryl group, —OR ²⁴ , —NR ²⁵ R ²⁶ or —SR ²⁷ ; ¹ charge It represents a counter ion to the sum.

Preferred embodiments in the case where R ²⁰ , R ²¹ and R ²⁴ to R ²⁸ are an alkyl group are the same as the preferred embodiments of the alkyl group 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 still more preferably 1 to 10.
Preferred embodiments when R ²⁰ to R ²⁸ are an aryl group are the same as the preferred embodiments of the aryl group for R ⁰ .

From the viewpoint of color developability, 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 , —SR ^27. NR ²⁵ R ²⁶ or ^{-SR 27,} more preferably, more preferably an alkyl group or ^{-OR 24,} ^{-OR 24} are 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. Is preferably an alkyl group having an arylthio group or an alkyloxycarbonyl group.
When R ²⁰ in the formula (1-1) is —OR ²⁴ , 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. -Butyl groups are particularly preferred.
When R ²⁰ in the formula (1-1) is an alkenyl group, the alkenyl group may be an alkenyl group having an aryl group or a hydroxyaryl group.

From the viewpoint of color development, R ²¹ in Formula (1-2) is preferably a hydrogen atom.
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 —C (＝ O) OR ²⁴ Or —OC (＝ O) OR ²⁴ is more preferred. 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 independently preferably a hydrogen atom or an alkyl group, and at least one R ²¹ in the formula (1-3) is more preferably an alkyl group.
Further, the alkyl group for 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 for R ²¹ is preferably an alkyl group having a branched or cyclic structure, and more preferably an isopropyl group, a cyclopentyl group, a cyclohexyl group, or a tert-butyl group. Further, the alkyl group for 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 further preferably a pyridinium group.
The onium group in R ^23, pyridinium group, an ammonium group, sulfonium group and the like. The onium group may have a substituent. Examples of the substituent include 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. Examples of the group include an alkyl group, an aryl group, and a combination thereof.
Among them, a pyridinium group is preferable, and an N-alkyl-3-pyridinium group, an N-benzyl-3-pyridinium group, an N- (alkoxypolyalkyleneoxyalkyl) -3-pyridinium group, an N-alkoxycarbonylmethyl-3-pyridinium group 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 preferred, N-alkyl-3-pyridinium group or N-alkyl-4-pyridinium group is still more preferred, and N-methyl-3-pyridinium group, N-octyl -3-pyridinium group, N-methyl-4-pyridinium group Or, particularly preferably N- octyl-4-pyridinium group, N- octyl-3-pyridinium group or, N- octyl-4-pyridinium group is most preferred.
When R ²³ is a pyridinium group, examples of the counter anion include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroantimonate ion, a p-toluenesulfonate ion, and a perchlorate ion. And the like, and p-toluenesulfonate ion, hexafluorophosphate ion or hexafluoroantimonate ion is preferable.

From the viewpoint of color development, R ²⁰ in Formula (1-4) is preferably an alkyl group or an aryl group, and one of the two R ²⁰ is more preferably an alkyl group and the other is more preferably an aryl group. The two R ²⁰ are linked to may form a ring.
From the viewpoint of color development, R ²⁰ in the formula (1-5) is preferably an alkyl group or an aryl group, more preferably an aryl group, and further preferably a p-methylphenyl group.
From the viewpoint of color development, R ²⁰ in the formula (1-6) is independently preferably an alkyl group or an aryl group, more preferably a methyl group or a phenyl group.
From the viewpoint of color development, Z ¹ in Formula (1-7) may be a counter ion for neutralizing the charge, and may be included in Za as a whole compound.
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. Fluorophosphate ions or hexafluoroantimonate ions are more preferred.

When L in Formula 1 or Formula 1-A is an oxygen atom, 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 each independently represent a hydrogen atom, an alkyl group or an aryl group, E represents an onium group, and * represents L in Formula 1 or Formula 1-A. Represents a bonding site to 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 for R ⁰ , and the preferred embodiment is also the same as the preferred embodiment for the aryl group for R ⁰ .
The onium group represented by E is the same as the onium group for R ²³ , and the preferred embodiment is also the same as the preferred embodiment of the onium group for R ²³ .

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

Wherein (6), R ¹⁷ represents a halogen atom, an alkyl group, an aryl group, hydroxy group or alkoxy group, if R ¹⁷ there are a plurality, the plurality of R ¹⁷ may be the same or different, or a plurality of R ¹⁷ may combine to form a ring. n2 represents an integer of 0 to 4. R ¹⁸ represents an alkyl group or an aryl group. Z _b represents a counter ion for neutralizing a charge.

Alkyl group or aryl group represented by R ¹⁷ or ^{R 18} ^is the same as the aryl group in the alkyl group, or ^{R 0} in R 2 ~ ^{R 9} and ^{R 0,} a preferred embodiment also the ^R 2 ~ ^{R 9} and ^{R 0} It is the same as the preferred embodiment of the alkyl group or the aryl group for R ⁰ .
The alkoxy group represented by R ¹⁷ is preferably an alkoxy group having 1 to 10 carbon atoms, and includes a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group and a tert-butoxy group. No.
n2 is preferably 0.
Counterions to neutralize the charge represented by Z _b is the same as Z ¹ in the formula (1-7), preferred embodiments are also the same as the preferred embodiment of Z ¹ in formula (1-7) .

When L is an oxygen atom in Formula 1 or Formula 1-A, specific examples of the group represented by R ¹ will be given below, but the present disclosure is not limited thereto. In the following structural formula, TsO 2 ^— represents a tosylate anion, and ● represents a bonding site to 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 R ¹ -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 the formula (2-1), ● represents a bonding site to the sulfur atom represented by L in the formula 1 or 1-A, and R ²¹ each independently represents a hydrogen atom, an alkyl group or an aryl group. And 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 the formula (3-1), ● represents a bonding site to the nitrogen atom contained in L in the formula 1 or 1-A, and X ¹ and X ² each independently represent an oxygen atom or a sulfur atom. And 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 represented by the above formulas (1-1) to (1-7). The description of the alkyl group, aryl group, alkenyl group, alkoxy group and onium group described above can be used.

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 formulas 1 and 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 R ^Z —O bond in the formula 2 is cleaved by infrared exposure.

In Formula 2, R ^Z represents an alkyl group, and the wavy line represents a bonding site with the 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 for R ² to R ⁹ and R ⁰ described above.
From the viewpoints of color developability and UV printing durability of the resulting lithographic printing plate, the alkyl group is preferably a secondary alkyl group or a tertiary alkyl group, and is preferably a tertiary alkyl group. Is preferred.
Further, from the viewpoints of color development and UV printing durability of the resulting lithographic printing plate, the alkyl group is preferably an alkyl group having 1 to 8 carbon atoms, and is preferably a branched alkyl group having 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.

<< The following are specific examples of the group represented by the above formula 2, but the present disclosure is not limited thereto. In the following structural formulas, ● represents a bonding site to L in Formula 1 or Formula 1-A.

Specific examples of the infrared absorbent that decomposes by infrared exposure are described below, but the present disclosure is not limited thereto.

Further, as the infrared absorbing agent that is decomposed by infrared exposure, those described in JP-T-2008-544322 or WO 2016/027886 can be suitably used.

One infrared absorber may be used alone, or two or more infrared absorbers 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 absorbent in the image recording layer is preferably from 0.1% by mass to 10.0% by mass, more preferably from 0.5% by mass to 5.0% by mass, based on the total mass of the image recording layer. preferable.

(Relation between electron donating polymerization initiator, electron accepting polymerization initiator, and infrared absorber)
The image recording layer according to the present disclosure includes the electron donating polymerization initiator, the electron accepting polymerization initiator, and the infrared absorbing agent, and the HOMO of the electron donating polymerization initiator is −6.0 eV or more. And the LUMO of the electron-accepting polymerization initiator is preferably -3.0 eV or less.
More preferred embodiments of the HOMO of the electron donating polymerization initiator and the LUMO of the electron accepting polymerization initiator are as described above.
In the image recording layer according to the present disclosure, the electron-donating polymerization initiator, the infrared absorber, and the electron-accepting polymerization initiator are, for example, performing energy transfer as described in the following chemical formula. Guessed.
Therefore, if the HOMO of the electron donating polymerization initiator is -6.0 eV or more and the LUMO of the electron accepting polymerization initiator is -3.0 eV or less, the efficiency of radical generation is improved. It is considered that it is easy to excel in chemical resistance and printing durability.

From the viewpoints of printing durability and chemical resistance, the difference between the HOMO of the electron donating polymerization initiator and the HOMO of the infrared absorber is preferably 1.00 eV to -0.200 eV, more preferably 0.700 eV. More preferably, it is -0.100 eV. A negative value means that the HOMO of the electron donating polymerization initiator is higher than the HOMO of the infrared absorber.
From the viewpoints of printing durability and chemical resistance, the difference between the LUMO of the infrared absorbing agent and the LUMO of the electron-accepting polymerization initiator is preferably 1.00 eV to -0.200 eV. More preferably, it is from .700 eV to -0.100 eV. A negative value means that the LUMO of the infrared absorbing agent is higher than the LUMO of the electron accepting polymerization initiator.

(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. Among them, polymer particles or microgels having a polymerizable group are preferable. In a particularly preferred embodiment, the polymer particles comprise at least one ethylenically unsaturated polymerizable group. Due to the presence of such polymer particles, the effect of improving the printing durability of exposed portions and the on-press developability of unexposed portions can be obtained.
Further, the polymer particles are preferably thermoplastic polymer particles.

As the thermoplastic polymer particles, Research Disclosure No. 1 of January 1992 can be used. Thermoplastic polymer particles described in JP-A-33303, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250 and European Patent No. 931647 are preferred.
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, vinyl carbazole, and a polyalkylene structure. Mention may be made of 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 used. The average particle size of the thermoplastic polymer particles is preferably from 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 a change in a functional group at that time.

The heat-reactive group in the polymer particles having a heat-reactive group may be any functional group that performs any reaction as long as a chemical bond is formed, but is preferably a polymerizable group. An ethylenically unsaturated group (for example, acryloyl group, methacryloyl group, vinyl group, allyl group, etc.), a cationically polymerizable group (for example, vinyl group, vinyloxy group, epoxy group, oxetanyl group, etc.) for performing radical polymerization reaction, addition reaction Isocyanate 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 hydroxy or amino group as a reaction partner, an acid anhydride for performing a ring-opening addition reaction, and an amino acid as a reaction partner. And a group or hydroxy group are preferably exemplified.

(4) The microcapsules are obtained by encapsulating at least a part of the components of the image recording layer in microcapsules as described in JP-A-2001-277740 and JP-A-2001-277742. The components of the image recording layer can be contained outside the microcapsules. In a preferred embodiment, the image recording layer containing microcapsules has a structure in which hydrophobic constituents are encapsulated in microcapsules and hydrophilic constituents are contained outside the microcapsules.

The microgel (crosslinked polymer particles) can contain a part of the constituent components of the image recording layer on at least one of the surface and the inside. In particular, a reactive microgel having a radical polymerizable group on its surface is preferable from the viewpoint of image formation sensitivity and printing durability.

公知 A known method can be applied to microencapsulate or microgel the components of the image recording layer.

As the polymer particles, from the viewpoints of printing durability, stain resistance and storage stability, a polyvalent isocyanate compound which is an adduct of a polyhydric phenol compound having two or more hydroxy groups in a molecule and isophorone diisocyanate And those obtained by the reaction of a compound having active hydrogen.
As the polyhydric phenol compound, a compound having a plurality of benzene rings having a phenolic hydroxy group is preferable.
As the compound having 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. preferable.
Examples of the resin particles obtained by the reaction of a polyvalent isocyanate compound which is an adduct of a polyhydric phenol compound having two or more hydroxy groups in the molecule with isophorone diisocyanate and a compound having active hydrogen are disclosed in JP-A-2012 Preferred are polymer particles described in paragraphs 0032 to 0095 of JP-A-206495.

Further, from the viewpoint of printing durability and solvent resistance, the polymer particles have a hydrophobic main chain, and i) a constituent unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) It preferably contains both structural units having pendant groups containing hydrophilic polyalkylene oxide segments.
The hydrophobic main chain is preferably an acrylic resin chain.
Preferred examples of the pendant cyano group include-[CH ₂ CH (C≡N)-] or-[CH ₂ C (CH ₃ ) (C≡N)-].
Further, the constituent unit having a pendant cyano group can be easily derived from an ethylenically unsaturated monomer such as acrylonitrile or methacrylonitrile, or a combination thereof.
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 repeating alkylene oxide structures in the hydrophilic polyalkylene oxide segment is preferably from 10 to 100, more preferably from 25 to 75, and even more preferably from 40 to 50.
Both a structural unit having a hydrophobic main chain and i) having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a structural unit having a pendant group including a hydrophilic polyalkylene oxide segment Preferred examples of the resin particles containing are those described in paragraphs 0039 to 0068 of JP-T-2008-503365.

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 still more preferably 0.10 μm to 1.0 μm. In this range, good resolution and stability over time can be obtained.
The average primary particle size of each of the particles in the present disclosure is measured by a light scattering method, or an electron micrograph of the particles is taken, and the total particle size of the particles is measured on the photograph to be 5,000. The value shall be calculated. In addition, as for the non-spherical particles, the particle diameter value of the spherical particles having the same particle area as the particle area on the photograph is defined as the particle diameter.
Further, the average particle size in the present disclosure is a volume average particle size unless otherwise specified.
The content of the polymer particles is preferably 5% by mass to 90% by mass based on the total mass of the image recording layer.

(Acid color former)
The image recording layer used in the present disclosure preferably contains an acid coloring agent.
The “acid color former” used in the present disclosure means a compound having a property of developing a color when heated while receiving an electron accepting compound (for example, a proton such as an acid). As the acid coloring agent, in particular, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, and amide, and when contacted with an electron accepting compound, these partial skeletons are rapidly opened or cleaved. Compounds are preferred.

Examples of such acid color formers include 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide (referred to as “crystal violet lactone”), 3,3-bis (4- Dimethylaminophenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1 , 2-Dimethylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3) -Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bi (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide,

3,3-bis [1,1-bis (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis ( 4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3,3-bis [1- (4-dimethylaminophenyl) -1- (4-methoxyphenyl) Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-pyrrolidinophenyl) -1- (4-methoxyphenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3- [1,1-di (1-ethyl-2-methylindol-3-yl) ethylene-2-yl] -3- (4-diethylaminophenyl ) Phthalide, 3- [1,1-di (1-ethyl-2-me Ruindol-3-yl) ethylene-2-yl] -3- (4-N-ethyl-N-phenylaminophenyl) phthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-n -Octyl-2-methylindol-3-yl) -phthalide, 3,3-bis (1-n-octyl-2-methylindol-3-yl) -phthalide, 3- (2-methyl-4-diethylaminophenyl) Phthalides such as) -3- (1-n-octyl-2-methylindol-3-yl) -phthalide;

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

3,6-dimethoxyfluoran, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3 -Diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6,7-dimethylfluoran, 3-N-cyclohexyl-Nn-butylamino-7-methylfluoran, 3-diethylamino-7- Dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-di-n-hexylaminofluoran, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7- ( 2'-fluorophenylamino) fluoran, 3-diethylamino 7- (2'-chlorophenylamino) fluoran, 3-diethylamino-7- (3'-chlorophenylamino) fluoran, 3-diethylamino-7- (2 ', 3'-dichlorophenylamino) fluoran, 3-diethylamino-7- (3′-trifluoromethylphenylamino) fluoran, 3-di-n-butylamino-7- (2′-fluorophenylamino) fluoran, 3-di-n-butylamino-7- (2′-chlorophenylamino ) Fluoran, 3-N-isopentyl-N-ethylamino-7- (2′-chlorophenylamino) fluoran,

3-Nn-hexyl-N-ethylamino-7- (2'-chlorophenylamino) fluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-di-n-butylamino-6- Chloro-7-anilinofluoran, 3-diethylamino-6-methoxy-7-anilinofluoran, 3-di-n-butylamino-6-ethoxy-7-anilinofluoran, 3-pyrrolidino-6- Methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-morpholino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7- Anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di- -Pentylamino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-methylamino-6-methyl-7-anilinofluoran, 3-Nn-propyl-N-methylamino- 6-methyl-7-anilinofluoran, 3-NN-propyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-NN-butyl-N-methylamino-6- Methyl-7-anilinofluoran, 3-Nn-butyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-isobutyl-N-methylamino-6-methyl-7- Anilinofluoran, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluoran, 3 -Nn-hex 3-N-methylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-Nn- Propylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-NNn-butylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-Nn-hexylamino -6-methyl-7-anilinofluoran, 3-N-cyclohexyl-NNn-octylamino-6-methyl-7-anilinofluoran,

3-N- (2'-methoxyethyl) -N-methylamino-6-methyl-7-anilinofluoran, 3-N- (2'-methoxyethyl) -N-ethylamino-6-methyl-7 -Anilinofluoran, 3-N- (2'-methoxyethyl) -N-isobutylamino-6-methyl-7-anilinofluoran, 3-N- (2'-ethoxyethyl) -N-methylamino -6-methyl-7-anilinofluoran, 3-N- (2'-ethoxyethyl) -N-ethylamino-6-methyl-7-anilinofluoran, 3-N- (3'-methoxypropyl ) -N-methylamino-6-methyl-7-anilinofluoran, 3-N- (3'-methoxypropyl) -N-ethylamino-6-methyl-7-anilinofluoran, 3-N- (3'-ethoxypropyl) -N- Tylamino-6-methyl-7-anilinofluoran, 3-N- (3'-ethoxypropyl) -N-ethylamino-6-methyl-7-anilinofluoran, 3-N- (2'-tetrahydro Furfuryl) -N-ethylamino-6-methyl-7-anilinofluoran, 3-N- (4'-methylphenyl) -N-ethylamino-6-methyl-7-anilinofluoran, 3- Diethylamino-6-ethyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (3'-methylphenylamino) fluoran, 3-diethylamino-6-methyl-7- (2 ', 6'- Dimethylphenylamino) fluoran, 3-di-n-butylamino-6-methyl-7- (2 ', 6'-dimethylphenylamino) fluoran, 3-di-n-butylamino-7- 2 ', 6'-dimethylphenylamino) fluoran, 2,2-bis [4'-(3-N-cyclohexyl-N-methylamino-6-methylfluoran) -7-ylaminophenyl] propane, 3- Fluoranes such as [4 '-(4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluorane and 3- [4'-(dimethylaminophenyl)] amino-5,7-dimethylfluorane Kind,

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

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) xanthen] -3-one, 3'-N , N-Dibenzylamino-6'-N, N-diethylaminospiro [isobenzofuran-1 (3H), 9 '-(9H) xanthen] -3-one, 2'-(N-methyl-N-phenyl) Amino-6 '-(N-ethyl-N- (4-methylphenyl)) aminospiro [isobenzofuran-1 (3H), 9'-(9H) xanthen] -3-one.

Above all, the acid color former used in the present disclosure may be at least one compound selected from the group consisting of a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound, from the viewpoint of coloration. preferable.
The hue of the dye after coloring is preferably green, blue or black from the viewpoint of visibility.

Commercially available products can also be used as the acid colorant. 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 (both manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Gre n-118, Red-40, Red-8 (manufactured by Yamamoto Chemicals Co., Ltd.), crystal violet lactone (manufactured by Tokyo Kasei Kogyo Co., Ltd.), and the like. Among these commercial products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63 , GN-169, and crystal violet lactone are preferable because the visible light absorption of the formed film is good.

These acid colorants may be used alone or in combination of two or more.
The content of the acid colorant 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 polymer other than specific binder polymer)
The image recording layer may contain a binder polymer other than the specific binder polymer (hereinafter, also referred to as “other binder polymer”).
The specific binder polymer and the polymer corresponding to the polymer particles do not correspond to the other binder polymer. 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 a styrene 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 precursor can be suitably used. As an example, a binder polymer (hereinafter also referred to as a binder polymer for on-press development) used in an on-press development type lithographic printing plate precursor will be described in detail.
As the binder polymer for on-press 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) site in the main chain or a side chain. Further, 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 may be used.
When a poly (alkylene oxide) moiety is present in the main chain, a polyurethane resin is preferred. Examples of the main chain polymer having a poly (alkylene oxide) moiety in a side chain include (meth) acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, polystyrene resin, and novolak type Phenol resins, polyester resins, synthetic rubbers, and natural rubbers are exemplified, and (meth) acrylic resins are particularly preferred.

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

The star-shaped polymer compound has a polymerizable group such as an ethylenically unsaturated bond for improving the film strength of an image portion as described in JP-A-2008-195018, and has a main chain or a side chain, preferably a side chain. What is possessed in the chain is mentioned. Crosslinks are formed between polymer molecules by the polymerizable group, and curing is accelerated.
As the polymerizable group, an ethylenically unsaturated group such as a (meth) acryl group, a vinyl group, an allyl group, and a vinylphenyl group (styryl group) and an epoxy group are preferable, and a (meth) acryl group, a vinyl group, a vinylphenyl A group (styryl group) is more preferable from the viewpoint of polymerization reactivity, and a (meth) acryl group is particularly preferable. These groups can be introduced into the polymer by a polymer reaction or copolymerization. For example, a reaction between a polymer having a carboxy group in a side chain and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and a carboxylic acid having an ethylenically unsaturated group such as methacrylic acid can be used. These groups may be used in combination.

Regarding 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 more preferably 10,000 to 300, More preferably, 000.

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

In the image recording layer used in the present disclosure, another binder polymer may be used alone or in combination of two or more.
The other binder polymer can be contained in an arbitrary amount in the image recording layer, but the content of the binder polymer is preferably 1% by mass to 90% by mass based on the total mass of the image recording layer. It is more preferably from 5% by mass to 80% by mass.
When the image recording layer in the present disclosure includes another binder polymer, the content of the other binder polymer based on the total mass of the specific binder polymer and the other binder polymer is more than 0% by mass and 99% by mass or less. 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 improving the printing durability of 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 a boiling point (difficulty of volatilization), and a compound having a mercapto group on an 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.

Only one type of chain transfer agent may be added, or two or more types 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 more preferably 0.1% by mass to 30% by mass based on the total mass of the image recording layer. % Is more preferred.

(Degreasing agent)
The image recording layer may contain a sensitizing agent such as a phosphonium compound, a nitrogen-containing low molecular weight compound, or an ammonium group-containing polymer in order to improve the inking property. In particular, when the overcoat layer contains an inorganic layered compound, these compounds function as a surface coating agent for the inorganic layered compound, and can suppress a decrease in the inking property of the inorganic layered compound during printing.
As the sensitizer, it is preferable to use a phosphonium compound, a nitrogen-containing low-molecular compound, and an ammonium group-containing polymer in combination, and it is preferable to use a phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer in combination. Is more preferred.

-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), 1,7-bis (tri Phenylphosphonio) heptane sulfate, 1,9-bis (triphenylphosphonio) nonane = naphthalene-2,7-disulfonate and the like.

-Nitrogen-containing low molecular compounds-
Examples of the nitrogen-containing low molecular weight compound include amine salts and quaternary ammonium salts. Further, imidazolinium salts, benzimidazolinium salts, pyridinium salts, and quinolinium salts are also included. Among them, quaternary ammonium salts and pyridinium salts are preferred. Specific examples include tetramethylammonium = hexafluorophosphate, tetrabutylammonium = hexafluorophosphate, dodecyltrimethylammonium = p-toluenesulfonate, benzyltriethylammonium = hexafluorophosphate, benzyldimethyloctylammonium = hexafluorophosphate Phthalate, benzyldimethyldodecylammonium = hexafluorophosphate, compounds described in paragraphs 0021 to 0037 of JP-A-2008-284858, compounds described in paragraphs 0030 to 0057 of JP-A-2009-90645, and the like are included.

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

The ammonium salt-containing polymer preferably has a reduced specific viscosity (unit: ml / g) in the range of 5 to 120, preferably 10 to 110, determined according to the measuring method described in JP-A-2009-208458. Are more preferable, and those in the range of 15 to 100 are particularly preferable. When the reduced specific viscosity is converted to a weight average molecular weight (Mw), it is preferably 10,000 to 150,0000, more preferably 17,000 to 140,000, and particularly preferably 20,000 to 130,000.

Hereinafter, specific examples of the ammonium group-containing polymer will be described.
(1) 2- (trimethylammonio) ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10/90, Mw 45,000)
(2) 2- (trimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(3) 2- (ethyldimethylammonio) ethyl methacrylate = p-toluenesulfonate / hexyl methacrylate copolymer (molar ratio 30/70, Mw 45,000)
(4) 2- (trimethylammonio) ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20/80, Mw 60,000)
(5) 2- (trimethylammonio) ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (40/60 molar ratio, Mw 70,000)
(6) 2- (butyldimethylammonio) ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 25/75, Mw 65,000)
(7) 2- (butyldimethylammonio) ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80, Mw 65,000)
(8) 2- (butyldimethylammonio) ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecane sulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20/80) , Mw 75,000)

The content of the sensitizer is preferably 1% by mass to 40.0% by mass, more preferably 2% by mass to 25.0% by mass, and more preferably 3% by mass to 20% by mass based on the total mass of the image recording layer. % Is more preferred.

(Development accelerator)
The image recording layer used in the present disclosure may include a development accelerator.
As the development accelerator, a hydrophilic high molecular compound or a hydrophilic low molecular compound is preferable.
In the present disclosure, a hydrophilic high molecular compound refers to a compound having a molecular weight (weight average molecular weight when having a molecular weight distribution) of 3,000 or more, and a hydrophilic low molecular compound refers to a molecular weight (weight average when having a molecular weight distribution). Molecular weight) of less than 3,000.

-Hydrophilic polymer compound-
Examples of the hydrophilic polymer compound include a cellulose compound and polyvinyl alcohol, and a cellulose compound is 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.
As the modified cellulose compound, a compound in which at least a part of the hydroxy group of cellulose is substituted by at least one selected from the group consisting of an alkyl group and a hydroxyalkyl group is preferably exemplified.
As the modified cellulose compound, an alkyl cellulose compound or a hydroxyalkyl cellulose compound is preferable, and a hydroxyalkyl cellulose compound is more preferable.
Preferred examples of the alkyl cellulose compound include methyl cellulose.
Preferred examples of the hydroxyalkyl cellulose compound include hydroxypropyl cellulose.

(4) The molecular weight of the hydrophilic polymer compound (weight average molecular weight when it has a molecular weight distribution) is preferably from 3,000 to 300,000, more preferably from 10,000 to 150,000.

－Hydrophilic low molecular weight compound－
Examples of the hydrophilic low molecular weight compound include a glycol compound, a polyol compound, an organic amine compound, an organic sulfonic acid compound, an organic sulfamine compound, an organic sulfate compound, an organic phosphonic acid compound, an organic carboxylic acid compound, and a betaine compound. , An organic sulfonic acid compound or a betaine compound.

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 an alkyl sulfonic acid having an alkyl group having 8 to 20 carbon atoms is preferable.
Examples of the organic sulfamine compound include alkylsulfamic acid and the like and salts thereof.
Examples of the organic sulfate compound include alkyl sulfate, alkyl ether sulfate, 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 tartaric 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 preferably a trimethylglycine.

分子 The molecular weight of the hydrophilic low molecular weight compound (weight average molecular weight when having a molecular weight distribution) is preferably 50 or more and less than 3,000, and more preferably 100 to 1,000.

-Content-
The content of the development accelerator based on the total mass of the image recording layer is preferably from 0.1% by mass to 20% by mass, more preferably from 0.5% by mass to 15% by mass, and more preferably from 1% by mass to 10% by mass. % By mass or less is more preferable.

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

(Formation of image recording layer)
The image recording layer in the lithographic printing plate precursor according to the present disclosure is coated, for example, by dispersing or dissolving the necessary components described above in a known solvent, as described in paragraphs 0142 to 0143 of JP-A-2008-195018. A liquid can be formed by preparing a liquid, applying a coating liquid on a support by a known method such as coating with a bar coater, and drying. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the use, but is preferably from 0.3 g / m ² to 3.0 g / m ² . Within this range, good sensitivity and good film properties 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, Propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3- Methoxy-1-propanol, methoxymethoxy Tanol, 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-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone , Methyl lactate, ethyl lactate and the like. The solvents may be used alone or in combination of two or more. The solid content concentration in the coating solution is preferably from 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 properties of the image recording layer, 0.3 g / m ² to 3.0 g / m. m ² is preferred.
Further, the thickness of the image recording layer in the lithographic printing plate precursor according to the present disclosure is preferably from 0.1 μm to 3.0 μm, and more preferably from 0.3 μm to 2.0 μm.
In the present disclosure, the thickness of each layer in the lithographic printing plate precursor is determined by preparing a slice cut in a direction perpendicular to the surface of the lithographic printing plate precursor, and observing a cross section of the slice with a scanning microscope (SEM). Confirmed by

<Overcoat layer>
The lithographic printing plate precursor according to the present disclosure has an overcoat layer (sometimes called a “protective layer”) on the surface of the image recording layer opposite to the support.
The thickness of the overcoat layer is larger than the thickness of the image recording layer.
The overcoat layer has a function of preventing damage to the image recording layer and a function of preventing ablation at the time of high-intensity laser exposure, in addition to a function of suppressing an image formation inhibition reaction by blocking oxygen.

The overcoat layer having such characteristics is described in, for example, US Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. As the low oxygen permeable polymer used for the overcoat layer, any of a water-soluble polymer and a water-insoluble polymer can be appropriately selected and used, and if necessary, a mixture of two or more types may be used. However, it is preferable to contain a water-soluble polymer from the viewpoint of on-press developability.
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 a solution in which 1 g of the polymer is dissolved in 70 ° C. and 100 g of pure water is cooled to 25 ° C. It means a polymer that does not precipitate even if it is deposited.
Examples of the water-soluble polymer used in the overcoat layer include polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, a 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 include modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137.

Among the above water-soluble polymers, it is preferable to include polyvinyl alcohol, and it is more preferable to include polyvinyl alcohol having a saponification degree of 50% or more.
The saponification degree is preferably at least 60%, more preferably at least 70%, even more preferably at least 85%. The upper limit of the degree of saponification 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 embodiment of the overcoat layer, an embodiment containing polyvinyl alcohol and polyethylene glycol is also preferably exemplified.

When the overcoat layer according to the present disclosure includes a water-soluble polymer, the content of the water-soluble polymer is preferably 1% by mass to 99% by mass, and more preferably 3% by mass to 97% by mass based on the total mass of the overcoat layer. More preferably, it is 5 to 95% 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 tabular shape, for example, a group of mica such as natural mica and synthetic mica, talc, teniolite, montmorillonite, saponite, hectotype represented by the formula: 3MgO.4SiO.H ₂ O Light, zirconium phosphate and the like.
The inorganic layer compound preferably used is a mica compound. Examples of the mica compound include a compound represented by the formula: A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O) ₂ [where A is any of K, Na, and Ca; One of Fe (II), Fe (III), Mn, Al, Mg, and V, and D is Si or Al. ] Mica groups such as natural mica and synthetic mica.

In the mica group, natural mica includes muscovite, soda mica, phlogopite, biotite and scale mica. Examples of the synthetic mica include non-swelling mica such as fluorophlogopite mica ₃ (AlSi ₃ O ₁₀ ) F ₂ , potassium tetrasilicic mica KMg _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 hectorite (Na, Li) _８ Mg _{2 / 5} Li _1/8 (Si ₄ O ₁₀ ) F _{2 and} other swellable mica. Further, synthetic smectite is also useful.

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

形状 From the viewpoint of diffusion control, the shape of the mica compound is preferably as thin as possible, and the planar size is preferably as large as not to impair the smoothness of the coated surface and the transmittance of active light. 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, and can be measured, for example, from a projection of a particle by a micrograph. The greater the aspect ratio, the greater the effect obtained.

粒子 The average particle diameter 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, 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 has a thickness of about 1 nm to 50 nm and a plane size (major axis) of about 1 μm to 20 μm.

含有 The content of the inorganic layered compound is preferably from 1% by mass to 60% by mass, more preferably from 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, the total amount of the inorganic layered compounds is preferably the above-mentioned content. Within the above range, oxygen barrier properties are improved, and good sensitivity is obtained. Further, it is possible to prevent a decrease in the inking property.

The overcoat layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coating properties, and inorganic particles for controlling surface slipperiness. Further, the sensitizer 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 of the overcoat layer (solid content) is preferably from ^{^{0.01g / m 2 ~ 10g / m}} 2, more preferably ^{^{0.02g / m 2 ~ 3g / m}} 2, 0.02g / m 2 ~ 1g / m ² is particularly preferred.
The thickness of the overcoat layer in the lithographic printing plate precursor according to the present disclosure is preferably from 0.1 μm to 5.0 μm, and more preferably from 0.3 μm to 4.0 μm.
The thickness of the overcoat layer in the lithographic printing plate precursor according to the present disclosure is preferably 1.1 to 5.0 times, and preferably 1.5 to 3.0 times, the film thickness of the image recording layer. More preferably, it is twice.

<Undercoat layer>
The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (sometimes called an intermediate layer) between the image recording layer and the support. The undercoat layer enhances the adhesion between the support and the image recording layer in the exposed area, and easily peels off the image recording layer from the support in the unexposed area, while suppressing a decrease in printing durability. It contributes to improving developability. In addition, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, which also has the effect of preventing heat generated by exposure from diffusing to the support and lowering the sensitivity.

化合物 Examples of the compound used for the undercoat layer include a polymer having an adsorptive group and a hydrophilic group that can be adsorbed on the support surface. 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 low molecular compound or a polymer. The compounds used in the undercoat layer may be used as a mixture of two or more as necessary.

When the compound used in 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.
Examples of the adsorptive group that can be adsorbed on the support surface include a phenolic hydroxy group, a carboxy group, —PO ₃ H ₂ , —OPO ₃ H ₂ , —CONHSO ₂ —, —SO ₂ NHSO ₂ —, and —COCH ₂ COCH _3. Is preferred. As the hydrophilic group, a sulfo group or a salt thereof, and a salt of a carboxy group are preferable. As the crosslinkable group, an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, and the like are preferable.
The polymer may have a polar substituent of the polymer, a substituent having a countercharge with the polar substituent and a crosslinkable group introduced by salt formation with a compound having an ethylenically unsaturated bond, Other monomers, preferably hydrophilic monomers, may be further copolymerized.

Specifically, a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679 and an ethylenic double bond described in JP-A-2-304441 are disclosed. A preferred example is a phosphorus compound having a heavy bond reactive group. JP-A-2005-238816, JP-A-2005-125749, JP-A-2006-239867 and JP-A-2006-215263, crosslinkable groups (preferably ethylenically unsaturated bonding groups), and supports Low-molecular or high-molecular compounds having a functional group and a hydrophilic group that interact with the surface are also preferably used.
More preferred are high-molecular polymers having an adsorptive group, a hydrophilic group and a crosslinkable group that can be adsorbed on the support surface described in JP-A-2005-125749 and JP-A-2006-188038.

The content of the ethylenically unsaturated bonding 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.

The undercoat layer is, in addition to the undercoat layer compound described above, a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, an amino group or a functional group having a polymerization inhibiting ability, and a support surface in order to prevent contamination with time. Such as 1,4-diazabicyclo [2.2.2] octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, Ethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, etc.).

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

(Lithographic printing plate manufacturing method and lithographic printing method)
The lithographic printing plate precursor according to the present disclosure is subjected to image exposure and development processing to produce a lithographic printing plate.
The method for preparing a lithographic printing plate according to the present disclosure includes a step of imagewise exposing the on-press development type lithographic printing plate precursor according to the present disclosure (hereinafter, also referred to as an “exposure step”), and printing on a printing press. A step of supplying at least one selected from the group consisting of ink and fountain solution to remove the image recording layer in the non-image area (hereinafter, also referred to as “on-press development step”).
The lithographic printing method according to the present disclosure includes a step of exposing the on-press development type lithographic printing plate precursor according to the present disclosure imagewise (exposure step), and at least one selected from the group consisting of a printing ink and a fountain solution. Supplying the image recording layer of the non-image portion on a printing press to produce a lithographic printing plate (on-press development process); and printing (printing process) with the obtained lithographic printing plate. Is preferred.
Hereinafter, a preferred embodiment of each step of the method for preparing a lithographic printing plate according to the present disclosure and the lithographic printing method according to the present disclosure will be described in order. The lithographic printing plate precursor according to the present disclosure can be developed with a developer.
Hereinafter, the exposure step and the on-press development step in the method for preparing a lithographic printing plate will be described, but the exposure step in the method for preparing a lithographic printing plate according to the present disclosure is the same as the exposure step in the lithographic printing method according to the present disclosure. The on-press development step in the lithographic printing plate manufacturing method according to the present disclosure is the same as the on-press development step in the lithographic printing method according to the present disclosure.

<Exposure process>
The method for preparing a lithographic printing plate according to the present disclosure preferably includes an exposure step of exposing the lithographic printing plate precursor according to the present disclosure imagewise to form an exposed portion and an unexposed portion. The lithographic printing plate precursor according to the present disclosure is preferably exposed imagewise by laser exposure through a transparent original having a line image, a halftone dot image, or the like, or by laser beam scanning using digital data.
The wavelength of the light source is preferably from 750 nm to 1,400 nm. As a light source having a wavelength of 750 nm to 1,400 nm, a solid-state laser and a semiconductor laser that emit infrared rays are suitable. Regarding the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably within 20 microseconds, and the irradiation energy amount is 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 internal drum system, an external drum system, a flatbed system, and the like.
Image exposure can be performed by a conventional method using a plate setter or the like. In the case of on-press development, after the lithographic printing plate precursor is mounted on the printing press, image exposure may be performed on the printing press.

<On-press development process>
The method of preparing a lithographic printing plate according to the present disclosure includes an on-press development step of supplying at least one selected from the group consisting of a printing ink and a fountain solution on a printing press to remove an image recording layer of a non-image portion. It is preferred to include.
The on-press development method will be described below.

[On-machine development method]
In the on-press development system, an imagewise exposed lithographic printing plate precursor is supplied with an oil-based ink and an aqueous component on a printing press, and the image recording layer in the non-image area is removed to produce a lithographic printing plate. Is preferred.
That is, after imagewise exposing the lithographic printing plate precursor, the lithographic printing plate precursor is directly mounted on a printing machine without any development processing, or, after the lithographic printing plate precursor is mounted on a printing machine, image exposure is performed on the printing machine. When an oil-based ink and an aqueous component are supplied and printed, an uncured image recording layer is formed in a non-image portion at an early stage during printing by one or both of the supplied oil-based ink and the aqueous component. It is removed by dissolution or dispersion, and a hydrophilic surface is exposed at 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. An oil-based ink or an aqueous component may be supplied to the plate first, but the oil-based ink is supplied first in order to prevent the aqueous component from being contaminated by the components of the image recording layer from which the aqueous component has been removed. Is preferred. In this way, the lithographic printing plate precursor is developed on-press on a printing press and used as is for printing a large number of sheets. As the oil-based ink and the aqueous component, a normal printing ink for lithographic printing and a fountain solution are suitably used.

レーザー As the laser for imagewise exposing the lithographic printing plate precursor according to the present disclosure, the wavelength of the light source is preferably from 300 nm to 450 nm or from 750 nm to 1,400 nm. In the case of a light source having a wavelength of 300 nm to 450 nm, a lithographic printing plate precursor containing a sensitizing dye having an absorption maximum in this wavelength region in an image recording layer is preferably used, and the light source having a wavelength of 750 nm to 1,400 nm is preferably as described above. Used. As the light source having a wavelength of 300 nm to 450 nm, a semiconductor laser is preferable.

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

In the method of preparing a lithographic printing plate from the lithographic printing plate precursor according to the present disclosure, and the lithographic printing method according to the present disclosure, if necessary, before the exposure, during the exposure, between the exposure and the development, the lithographic printing The entire surface of the plate master may be heated. By such heating, an image forming reaction in the image recording layer is promoted, and advantages such as improvement in sensitivity and printing durability, stabilization of sensitivity, and the like may be generated. Heating before development is preferably performed under mild conditions of 150 ° C. or less. According to the above aspect, problems such as hardening of the non-image portion can be prevented. It is preferable to use very strong conditions for heating after development, and it is preferable that the temperature be in the range of 100 ° C. to 500 ° C. When the content is in the above range, a sufficient image strengthening 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 with reference to Examples, but the present disclosure is not limited thereto. In this example, “%” and “parts” mean “% by mass” and “parts by mass”, respectively, unless otherwise specified. In the polymer compounds, unless otherwise specified, the molecular weight is the weight average molecular weight (Mw), and the ratio of the constituent repeating units is a mole percentage. The weight average molecular weight (Mw) is a value measured as a polystyrene equivalent value by gel permeation chromatography (GPC).

(Examples 1 to 17, Comparative Examples 1 to 4)
<Preparation of support>
To remove rolling oil on the surface of an aluminum plate (material: JIS A 1050) having a thickness of 0.3 mm, a 10% by mass aqueous sodium aluminate solution was subjected to a degreasing treatment at 50 ° C. for 30 seconds. The surface of the aluminum plate was grained using three 3-mm bundled nylon brushes and a Pumice-water suspension having a median diameter of 25 μm (specific gravity: 1.1 g / cm ³ ), and thoroughly washed with water. The aluminum plate was etched by immersing it in a 25% by mass aqueous solution of sodium hydroxide at 45 ° C. for 9 seconds, washed with water, and further immersed in a 20% by mass aqueous solution of nitric acid at 60 ° C. for 20 seconds and washed with water. The amount of etching on the grained surface was about 3 g / m ² .

Next, an electrochemical surface 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 temperature of the solution was 50 ° C. The AC power supply waveform is an electrochemical roughening process using a trapezoidal rectangular wave alternating current with a time TP for the current value from zero to a peak to reach a peak of 0.8 ms, a duty ratio of 1: 1 and a carbon electrode as a counter electrode. Was done. Ferrite was used for 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 supply was shunted to the auxiliary anode. The amount of electricity in the nitric acid electrolysis was 175 C / dm ² when the aluminum plate was an anode. Thereafter, water washing by spraying was performed.

Subsequently, nitric acid electrolysis was performed using a 0.5% by mass aqueous solution of hydrochloric acid (containing 0.5% by mass of aluminum ions) and an electrolytic solution at a liquid temperature of 50 ° C. under the conditions of an electric charge of 50 C / dm ² when the aluminum plate was an anode. Electrochemical surface roughening treatment was performed in the same manner as described above, and then water washing was performed by spraying.
Next, a DC anodized film of 2.5 g / m ² was formed on the aluminum plate at a current density of 15 A / dm ^{2 using a} 15% by mass aqueous solution of sulfuric acid (containing 0.5% by mass of aluminum ions) as an electrolytic solution, followed by water washing After drying, a support was prepared. The average pore diameter (surface average pore diameter) in the surface layer of the anodized film was 10 nm.
The pore diameter in the surface layer of the anodic oxide film was measured using an ultra-high resolution SEM (scanning electron microscope, S-900 manufactured by Hitachi, Ltd.) at a relatively low accelerating voltage of 12 V to impart conductivity. The surface was observed at a magnification of 150,000 times without performing a vapor deposition process or the like, and 50 pores were randomly extracted to obtain an average value. The standard deviation was ± 10% or less of the average value.

<Formation of lithographic printing plate precursor>
An undercoat liquid (1) having the following composition was applied on the support so as to have a dry coating amount of 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 solution (1) was coated on the undercoat layer with a bar, and dried in an oven at 100 ° C. for 60 seconds. The image recording layer having a dry coating amount of 0.60 g / m ² (film thickness = about 0.60 μm) Was formed to obtain a lithographic printing plate precursor.
Thereafter, an overcoat layer coating solution (1) having the following composition was applied on the image recording layer, and oven-dried at 100 ° C. for 60 seconds to dry the coating amount of 1.0 g / m ² (film thickness = about 1.0 μm). ) Was formed to obtain a lithographic printing plate precursor.

[Undercoat liquid (1)]
-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 >>
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 are added to a separating funnel, and the mixture is vigorously stirred and then left to stand. Was placed. After discarding the upper layer, 1,050 parts of diethylene glycol dibutyl ether was added, and the mixture was stirred vigorously and 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 following monomer M-2 were added to a three-necked flask, and the temperature was raised to 55 ° C. under a nitrogen atmosphere. Next, the following drop solution 1 was added dropwise over 2 hours, stirred for 30 minutes, 0.386 parts of VA-046B (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the temperature was raised to 80 ° C. Stir for 1.5 hours. After returning the reaction solution to room temperature (25 ° C.), a 30% by mass aqueous sodium hydroxide solution was added to adjust the pH to 8.0, and then 4-hydroxy-2,2,6,6-tetramethylpiperidine-1 was added. 0.005 parts of -oxyl (4-OH-TEMPO) was added. 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.

<<<< dripping liquid 1 >>
-Aqueous solution of the monomer M-1: 87.59 parts-14.63 parts of the monomer M-2-VA-046B (2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate Fate dihydrate, manufactured by Wako Pure Chemical Industries, Ltd.): 0.386 parts, distilled water: 20.95 parts

<Image recording layer coating liquid (1)>
-Infrared absorbing agent shown in Table 1 (compound having the following structure): 0.030 part-di-p-tolyliodonium-PF ₆ salt (manufactured by Aldrich): 0.1 in Table 1 if "Yes". 032 parts, NK ester A-9300 (manufactured by Shin-Nakamura Chemical Co., Ltd.): 0.100 parts; A-DPH (manufactured by Shin-Nakamura Chemical Co., Ltd.): 0 100 parts • Specific binder polymer described in Table 1: 0.825 parts • BYK306 (Byk Chemie): 0.008 parts • 1-methoxy-2-propanol: 8.609 parts • Methyl ethyl ketone: 1.091 parts • Electron-donating type polymerization initiator described in Table 1: Amount described in Table 1

<Overcoat layer coating solution>
・ Poval PVA105 (manufactured by Kuraray Co., Ltd., saponification degree 80% or more): 0.6 parts by mass ・ PEG4000 (manufactured by Tokyo Chemical Industry Co., Ltd.): 0.39 parts by mass ・ Surfactant (Lapisol A-80, Japan) Oil (manufactured by Oil Corporation): 0.01 parts by mass. Water: amount of 10 parts by mass as a whole.

<Evaluation>
[Printing durability]
The lithographic printing plate precursor obtained in each of the Examples and Comparative Examples was mounted on a Luxel PLATESETTER T-6000III manufactured by Fuji Film Co., Ltd. equipped with an infrared semiconductor laser, and the outer drum rotation speed was 1,000 rpm (revolutions per minute) and the laser output was 70. % And a resolution of 2,400 dpi (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 lithographic printing plate precursor was attached to a plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. After the water supply roller is decelerated by 5% with respect to the plate cylinder, dampening water of Ecolity-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) and space color fusion G ink ( DIC Graphics Co., Ltd.), and using a LITHONE 26 standard automatic printing start method, supplying dampening water and ink and developing on the machine. Then, at a printing speed of 10,000 sheets per hour, Tokishi Art ( Printing was performed on 50,000 sheets of paper (manufactured by Mitsubishi Paper Industries, Ltd., continuous weight: 76.5 kg).
With the increase in the number of printed sheets, the image recording layer was gradually worn and the ink receptivity was reduced, so that the ink density on the printing paper was reduced. The number of copies is defined as the number of copies when the value measured by x-lite (manufactured by x-lite) of the 3% halftone dot area ratio of the FM screen in printed matter is 5% lower than the measured value of the 100th printed sheet. The printing durability was evaluated as follows.

〔chemical resistance〕
The lithographic printing plate precursors of Examples and Comparative Examples were exposed and printed in the same manner as in the evaluation of the printing durability. Each time 5,000 sheets were printed, the chemical resistance was evaluated in the same manner as in the evaluation of the printing durability described above, except that a step of wiping the plate surface with a cleaner (manufactured by Fuji Film Co., Ltd., multi-cleaner) was added.
Specifically, the ratio of the number of printed sheets obtained by adding the step of wiping the plate surface to the number of printed sheets in the evaluation of the printing durability was used as an index value, and evaluation was performed according to the following evaluation criteria.
The larger the index value is, the smaller the change in printing durability is, even in the case where a step of wiping the plate surface with a cleaner is added, and the better the chemical resistance is.

-Evaluation criteria-
5: Index value is 95% or more and 100% or less 4: Index value is 80% or more and less than 95% 3: Index value is 60% or more and less than 80% 2: Index value is 40% or more and less than 60% 1: Index value is less than 40%

(On-press development)
The lithographic printing plate precursor obtained in each Example or Comparative Example was mounted on a Luxel PLATESETTER T-6000III manufactured by FUJIFILM Corporation equipped with an infrared semiconductor laser. Exposure was performed at 400 dpi. The exposed image included a solid image, a 50% halftone dot chart of a 20 μm dot FM screen, and a non-image portion.
The obtained exposed master was mounted on a plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Komori Co., Ltd. using a dampening solution of Ecolity-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) and Space Color Fusion G yellow ink (manufactured by DIC Graphics Co., Ltd.) After a dampening solution and ink were supplied and developed on the machine by the standard automatic printing start method of the corporation printing machine LITHRONE 26, the printing was performed at a printing speed of 10,000 sheets per hour at Toshibishi Art (Mitsubishi Paper Corp. Amount: 76.5 kg) 500 prints were made on paper.
The on-press development property was measured as the number of sheets of printing paper required until the on-press development of the unexposed portion of the image recording layer on the printing press was completed and no ink was transferred to the non-image portion. It can be said that the smaller the number, the more excellent the on-press developability.

[Ink deposition (printing initial ink deposition)]
The lithographic printing plate was exposed under the same exposure conditions as in the above evaluation of the on-press development property (the exposed image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen). It was attached to the plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation. Standard automatic of LITHRONE 26 using Equity-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) and Value-G (N) black ink (manufactured by DIC Corporation) Printing is started by supplying dampening water and ink by the printing start method, and printing on Tokishi Art (Mitsubishi Paper Corp., continuous weight: 76.5 kg) paper at a printing speed of 10,000 sheets per hour. Was performed 100 times.
The ink density in the solid image area was measured using a Macbeth densitometer (exact, manufactured by X-rite), and the number of printing papers required until the density reached 1.0 or more was determined by the ink deposition property (initial printing ink deposition). (Meat property) was evaluated according to the following evaluation criteria. The smaller the number of sheets, the better the lithographic printing plate is.

-Evaluation criteria-
1: The index value is 100 sheets or more 2: The index value is 50 sheets or more and less than 100 sheets 3: The index value is 30 sheets or more and less than 50 sheets 4: The index value is 20 sheets or more and less than 30 sheets 5 : Index value is less than 20 sheets

In Table 1, the description in the column of “Type” of the electron donating polymerization initiator indicates which of the following compounds 1 to 10 was used.
In Table 1, the description in the column of “Type” of the infrared absorbent indicates which compound of the following infrared absorbents 1 to 5 was used. The unit of HOMO and LUMO described below is eV.
In Table 1, the description in the column of "Type" in the column of the specific binder polymer indicates which compound of Polymer 1 or Polymer 2 below was used.
In Table 1, Comparative Example 2 is an example in which the dry coating amount of the overcoat layer was changed to 0.1 g / m ² (film thickness = about 0.1 μm).
Details of the compounds described in Table 1 are as follows. In the following chemical structural formula, Me represents a methyl group, and Bu represents a butyl group.

(Synthesis of specific binder polymer)
-Synthesis of binder polymer 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 dropped into this reaction vessel over 30 minutes. After the completion of the dropwise addition, the reaction was further continued for 7.5 hours. Thereafter, 0.3 g of AIBN was added, and the reaction was further continued for 12 hours. After the completion of the reaction, the reaction solution was cooled to room temperature. The composition ratio of the structural unit formed by the compound 1 to the structural unit formed by the compound 2 was 50:50 (mass ratio), and the weight average molecular weight of the binder polymer 1 was 75,000. The solid content was 20% by mass.

-Synthesis of binder polymer 5-
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 composed of 50.0 g of Compound 1, 30.0 g of Compound 2, 20.0 g of Compound 3, 0.7 g of AIBN, and 100 g of methyl ethyl ketone was dropped into this reaction vessel over 30 minutes. After the completion of the dropwise addition, the reaction was further continued for 7.5 hours. Thereafter, 0.3 g of AIBN was added, and the reaction was further continued for 12 hours. After the completion of the reaction, the reaction solution was cooled to room temperature. The composition ratio of the structural unit formed by the compound 1, the structural unit formed by the compound 2, and the structural unit formed by the compound 3 is 50:30:20 (mass ratio), and the weight average of the binder polymer 5 is obtained. The molecular weight was 75,000. The solid content was 20% by mass.

[Comparative specific binder polymer (Polymer 2)]
Polymer 2: polymethyl methacrylate (20% by mass 1-methoxy-2-propanol (MFG) solution), weight average molecular weight = 75,000

From the results shown in Table 1, according to the planographic printing plate precursor according to the example, a planographic printing plate excellent in chemical resistance, printing durability, and ink adhesion was obtained, and the on-press developability was also improved. It turns out that it is excellent.

The disclosure of Japanese Patent Application No. 2018-142865 filed on July 30, 2018 and the disclosure of Japanese Patent Application No. 2018-205750 filed on October 31, 2018 are entirely incorporated. Incorporated herein by reference.
All publications, patent applications, and technical standards referred to in this specification are to the same extent as if each individual publication, patent application, and technical standard were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims

A support, an image recording layer, and an overcoat layer, in this order,
The image recording layer contains a binder polymer, and an electron-donating polymerization initiator,
The binder polymer has a structural unit formed by an aromatic vinyl compound, and a structural unit formed by an acrylonitrile compound,
An on-press development type lithographic printing plate precursor wherein the thickness of the overcoat layer is larger than the thickness of the image recording layer.
2. The image recording layer according to claim 1, wherein the image recording layer further contains a polymerizable compound, and the content of the binder polymer based on the total mass of the polymerizable compound in the image recording layer is more than 0% by mass and 400% by mass or less. On-press development type lithographic printing plate precursor.
3. The on-press development type lithographic printing plate precursor according to claim 1, wherein the overcoat layer contains a water-soluble polymer.
4. The on-press development type lithographic printing plate precursor according to claim 3, wherein the water-soluble polymer contains polyvinyl alcohol having a degree of saponification of 50% or more.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 4, wherein the electron donating polymerization initiator is a borate compound.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 5, wherein the electron donating polymerization initiator is a tetraaryl borate compound.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 6, wherein the electron donating polymerization initiator is a tetraphenyl borate compound.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 7, wherein the highest occupied orbit of the electron donating type polymerization initiator is -6.0 eV or more.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 8, wherein the image recording layer further contains an electron-accepting polymerization initiator.
10. The on-press development type lithographic printing plate precursor according to claim 9, wherein the electron-accepting polymerization initiator is an onium compound.
The on-press development type lithographic printing plate precursor according to claim 9 or 10, wherein the lowest free orbit of the electron-accepting polymerization initiator is -3.0 eV or less.
The on-press development type lithographic printing plate precursor according to any one of claims 9 to 11, wherein the electron-accepting type polymerization initiator and the electron-donating type polymerization initiator form a salt.
The on-press development type lithographic printing plate precursor according to any one of claims 9 to 12, further comprising an iodonium borate compound as the electron-accepting polymerization initiator and the electron-donating polymerization initiator.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 13, wherein the binder polymer further has a structural unit formed of N-vinylpyrrolidone.
The on-press development type lithographic printing plate precursor according to any one of claims 1 to 14, wherein the image recording layer further contains an infrared absorbing agent.
16. The on-press development type lithographic printing plate precursor according to claim 15, wherein the infrared absorbing agent is an infrared absorbing agent that is decomposed by infrared exposure.
17. The on-press development type lithographic printing plate precursor according to claim 15, wherein the infrared absorbing agent is an infrared absorbing agent that is decomposed by heat, electron transfer, or both due to infrared exposure.
18. The on-press development type lithographic printing plate precursor according to any one of claims 15 to 17, wherein the infrared absorbing agent is a cyanine dye.
19. The on-press development type lithographic printing plate precursor according to claim 15, wherein the infrared absorbent is a compound represented by the following formula 1.

In Formula 1, R 1 represents a group capable of cleaving the R 1 -L bond by infrared exposure, and R 11 to R 18 each independently represent a hydrogen atom, a halogen atom, —Ra, —ORb, —SRc or —NRdRe. And Ra to Re each independently represent a hydrocarbon group, A 1 and A 2 and a plurality of R 11 to R 18 may be linked to form a monocyclic or polycyclic ring, and A 1 and A 2 Each independently represents an oxygen atom, a sulfur atom or a nitrogen atom; n 11 and n 12 each independently represent an integer of 0 to 5, provided that the sum of n 11 and n 12 is 2 or more; 13 and n 14 each 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 neutralizer. Represents a counter ion.
R 1 in the formula 1, on-press development type lithographic printing plate precursor as claimed in claim 19, which is a group represented by the following formula 2.

In Formula 2, R Z represents an alkyl group, and a wavy line represents a bonding site with the group represented by L in Formula 1 above.
21. An imagewise exposure of the on-press development type lithographic printing plate precursor according to any one of claims 1 to 20,
Supplying at least one selected from the group consisting of a printing ink and a fountain solution on a printing press to remove the image recording layer in the non-image area.
21. Image-wise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 20,
A step of providing a lithographic printing plate by supplying at least one selected from the group consisting of printing ink and fountain solution and removing the image recording layer of the non-image portion on a printing press,
Printing with the obtained lithographic printing plate.