Lithographic printing plate precursor, method for preparing a lithographic printing plate, and lithographic printing method

Abstract

To provide a lithographic printing plate precursor that makes it possible to obtain a lithographic printing plate with excellent printing durability even when a UV ink is used, and to provide a method for preparing a lithographic printing plate or a lithographic printing method using the lithographic printing plate precursor.SOLUTION: Provided is a lithographic printing plate precursor having a support and an image-recording layer on the support, where the image-recording layer contains an infrared absorber, a polymerization initiator, and a polymer A, the weight-average molecular weight of the polymer A is more than 15,000 and 150,000 or less, and the ethylenically unsaturated bond valence of the polymer A is 3.0 mmol / g or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a lithographic printing plate precursor, a method for preparing a lithographic printing plate, and a lithographic printing method. [Background technology]

[0002] Generally, a lithographic printing plate consists of an oleophilic image area that accepts ink during the printing process, and a hydrophilic non-image area that accepts dampening water. Lithographic printing utilizes the mutual repulsion properties of water and oil-based ink, making the oleophilic image area of ​​the lithographic printing plate the ink-receptive area and the hydrophilic non-image area the dampening water-receptive area (ink-non-receptive area) to create a difference in ink adhesion on the surface of the lithographic printing plate, and after ink is applied only to the image area, the ink is transferred to the printing material such as paper to print. To prepare such a lithographic printing plate, a lithographic printing plate precursor (PS plate) having an oleophilic photosensitive resin layer (image recording layer) on a hydrophilic support has been widely used. Usually, the lithographic printing plate precursor is exposed to light through an original such as a lithographic film, and then the image areas of the image recording layer are left, while the other unnecessary image recording layer is dissolved and removed with an alkaline developer or organic solvent, exposing the hydrophilic support surface to form non-image areas, thereby obtaining a lithographic printing plate.

[0003] Furthermore, due to growing concern about the global environment, environmental issues related to waste liquids accompanying wet processing such as development processing have come into focus. In response to the above environmental issues, efforts are being made to simplify development or plate making, or to eliminate any processing. One of the simple manufacturing methods is a method called "on-press development." In other words, after exposing a lithographic printing plate precursor to light, it is mounted on a printing press as is, without undergoing conventional development, and unnecessary parts of the image recording layer are removed at an early stage of the normal printing process.

[0004] An example of a conventional lithographic printing plate precursor is described in Patent Document 1. Patent Document 1 describes a lithographic printing plate precursor having a water-soluble or water-dispersible negative-type image recording layer on a hydrophilized aluminum support, in which the arithmetic mean height Sa of the outermost layer surface on the side having the image recording layer is 0.3 μm or more and 20 μm or less.

[0005] Furthermore, examples of conventional surface treatment agents for lithographic printing plates include those described in Patent Document 2. Patent Document 2 describes a surface treatment agent for a lithographic printing plate, which is characterized by containing a star-shaped polymer having at least one support-adsorbing group and at least one hydrophilic group.

[0006] Patent Document 1: International Publication No. 2018 / 181993 Patent Document 2: JP 2012-200959 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a lithographic printing plate precursor which provides a lithographic printing plate having excellent printing durability even when UV ink is used. Another object of the present invention is to provide a method for producing a lithographic printing plate or a lithographic printing method using the above-mentioned lithographic printing plate precursor. [Means for solving the problem]

[0008] Means for solving the above problems include the following aspects. <1> A lithographic printing plate precursor having a support and an image recording layer on the support, the image recording layer containing an infrared absorbing agent, a polymerization initiator, and a polymer A, the weight average molecular weight of the polymer A being more than 15,000 and not more than 150,000, and the ethylenically unsaturated bond valence of the polymer A being 3.0 mmol / g or more. <2> The polymer A contains a resin represented by the following formula (I): <1> The lithographic printing plate precursor according to claim 1. A P-(B P ) nP Formula (I) In formula (I), A P represents an organic group having a valence of nP and a hydrogen-bonding group; B P represents a group having two or more polymerizable groups, and nP represents an integer of 2 or more. <3> The polymer A has at least one structure selected from the group consisting of an adduct structure, a biuret structure, and an isocyanurate structure. <1> or <2> The lithographic printing plate precursor according to claim 1. <4> The polymer A has a structure represented by any one of the following formulas (A-1) to (A-3): <1> ~ <3> 10. The lithographic printing plate precursor according to claim 9,

[0009] [ka]

[0010] In formula (A-1), R A1 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and the wavy line portion represents the bonding position to other structures.

[0011] <5> Above B P The polymerizable group in the formula (I) contains a (meth)acryloxy group. <2> The lithographic printing plate precursor according to claim 1. <6> Above B P is a group having three or more (meth)acryloxy groups <2> or <5> The lithographic printing plate precursor according to claim 1. <7> The image recording layer contains two or more types of polymer A. <1> ~ <6> 10. The lithographic printing plate precursor according to claim 9, <8> The image recording layer further contains a polymerizable compound B having a weight average molecular weight of 1,000 or more and 15,000 or less. <1> ~ <7> 10. The lithographic printing plate precursor according to claim 9, <9> The image recording layer further contains a polymerizable compound C having a molecular weight of less than 1,000. <1> ~ <8> 10. The lithographic printing plate precursor according to claim 9, <10> The image recording layer is the outermost layer. <1> ~ <9> 10. The lithographic printing plate precursor according to claim 9, <11> The image recording layer further comprises polymer particles. <1> ~ <10> 10. The lithographic printing plate precursor according to claim 9, <12> The polymer particles have a hydrophilic group. <11> The lithographic printing plate precursor according to claim 1. <13> The hydrophilic group is a group represented by the following formula Z: <12> The lithographic printing plate precursor according to claim 1. *-QWY formula Z In formula Z, Q represents a divalent linking group, W represents a divalent group having a hydrophilic structure or a divalent group having a hydrophobic structure, Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophobic structure, either W or Y has a hydrophilic structure, and * represents a bonding site with another structure. <14> The hydrophilic structure includes a polyalkylene oxide structure. <12> or <13> The lithographic printing plate precursor according to claim 1. <15> The polymer particles contain structural units formed by an aromatic vinyl compound. <11> ~ <14> 10. The lithographic printing plate precursor according to claim 9, <16> The polymerization initiator includes an electron donating polymerization initiator. <1> ~ <15> 10. The lithographic printing plate precursor according to claim 9, <17> The value of HOMO of the infrared absorber-HOMO of the electron-donating polymerization initiator is 0.70 eV or less. <16> The lithographic printing plate precursor according to claim 1. <18> The image recording layer further contains a color former. <1> ~ <17> 10. The lithographic printing plate precursor according to claim 9, <19> The aluminum support has an aluminum plate and an anodized aluminum film disposed on the aluminum plate, the anodized film is located closer to the image recording layer than the aluminum plate, the anodized film has micropores extending in a depth direction from the surface on the image recording layer side, the average diameter of the micropores on the surface of the anodized film is more than 10 nm and not more than 100 nm, and the L of the surface of the anodized film on the image recording layer side is * a * b * Lightness L in color system * The value is between 70 and 100. <1> ~ <18> 10. The lithographic printing plate precursor according to claim 9, <20> The micropores are composed of large diameter pores extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm, and small diameter pores that communicate with the bottoms of the large diameter pores and extend from the communicating positions to a depth of 20 nm to 2,000 nm, the large diameter pores having an average diameter of 15 nm to 100 nm on the surface of the anodized film, and the small diameter pores having an average diameter of 13 nm or less at the communicating positions. <19> The lithographic printing plate precursor according to claim 1. <21> A protective layer containing a color-changing compound is provided on the image recording layer. <1> ~ <20> 10. The lithographic printing plate precursor according to claim 9, <22> Energy density 110mJ / cm 2 When exposed to infrared light with a wavelength of 830 nm, the change in brightness ΔL before and after the exposure is 2.0 or more. <21> The lithographic printing plate precursor according to claim 1. <23> The color-changing compound includes a compound that changes color upon exposure to infrared light. <21> or <22> The lithographic printing plate precursor according to claim 1. <24> The color-changing compound includes a decomposable compound that decomposes due to exposure to infrared rays. <21> ~ <23> 10. The lithographic printing plate precursor according to claim 9, <25> The color-changing compound includes a decomposable compound that decomposes due to heat, electron transfer, or both, caused by exposure to infrared light. <24> The lithographic printing plate precursor according to claim 1. <26> The color-changing compound is a cyanine dye. <21> ~ <25> 10. The lithographic printing plate precursor according to claim 9, <27> The color-changing compound is a compound represented by the following formula 1-1: <21> ~ <26> 10. The lithographic printing plate precursor according to claim 9,

[0012] [ka]

[0013] In formula 1-1, R 1 represents a group represented by any one of the following formulas 2 to 4, and R 11 ~R 18 are each independently a hydrogen atom, a halogen atom, or -R a, -OR b , -SR c , or -NR d R e R a ~R e each independently represents a hydrocarbon group; A1, A2 and a plurality of R 11 ~R 18 may be linked to form a monocyclic or polycyclic ring, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, n 11 and n 12 Each independently represents an integer of 0 to 5, provided that n 11 and n 12 The sum of is 2 or more, and n 13 and n 14 each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0014] [ka]

[0015] In formulas 2 to 4, R 20 , R 30 , R 41 and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents a bonding site with the group represented by L in the above formula 1-1.

[0016] <28> The color-changing compound is a compound represented by the following formula 1-2: <21> ~ <27> 10. The lithographic printing plate precursor according to claim 9,

[0017] [ka]

[0018] In formula 1-2, R 1 represents a group represented by any one of the above formulas 2 to 4, and R19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e R 23 and R 24 Each independently represents a hydrogen atom or -R a R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , or R 23 and R 24 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion which neutralizes the charge.

[0019] <29> The color-changing compound is a compound represented by any one of the following formulas 1-3 to 1-7. <21> ~ <28> 10. The lithographic printing plate precursor according to claim 9,

[0020] [ka]

[0021] In formulas 1-3 to 1-7, R 1 represents a group represented by any one of the above formulas 2 to 4, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e R 25 and R26 each independently represents a hydrogen atom, a halogen atom, or -R a R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , or R 25 and R 26 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion which neutralizes the charge.

[0022] <30> W in the above formulas 1-2 to 1-7 1 and W 2 are each independently an alkyl group having a substituent, and the substituent is a group having at least -(OCH2CH2)-, a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group. <28> or <29> The lithographic printing plate precursor according to claim 1. <31> In the above formulas 1-2 to 1-7, L is an oxygen atom. <28> ~ <30> 10. The lithographic printing plate precursor according to claim 9, <32> The content M of the color-changing compound in the protective layer X and the content M of the infrared absorbing agent in the image recording layer. Y Compared to M X / M Y is 0.2 or more <21> ~ <31> 10. The lithographic printing plate precursor according to claim 9, <33> The protective layer comprises a water-soluble polymer. <21> ~ <32> 10. The lithographic printing plate precursor according to claim 9, <34> The water-soluble polymer contains polyvinyl alcohol having a degree of saponification of 50% or more. <33> The lithographic printing plate precursor according to claim 1. <35> The water-soluble polymer comprises polyvinylpyrrolidone. <33> or <34> The lithographic printing plate precursor according to claim 1. <36> The protective layer comprises a hydrophobic polymer. <33> ~ <35> 10. The lithographic printing plate precursor according to claim 9, <37> The hydrophobic polymer is a hydrophobic polymer particle. <36> The lithographic printing plate precursor according to claim 1. <38> The hydrophobic polymer comprises a polyvinylidene chloride resin. <36> or <37> The lithographic printing plate precursor according to claim 1. <39> The hydrophobic polymer comprises a styrene-acrylic copolymer. <36> ~ <38> 10. The lithographic printing plate precursor according to claim 9, <40> The protective layer contains an oil sensitizer. <21> ~ <39> 10. The lithographic printing plate precursor according to claim 9, <41> The amount of the protective layer is 0.1 g / m 2 ~2.0g / m 2 is <21> ~ <40> 10. The lithographic printing plate precursor according to claim 9, <42> <1> ~ <41> and supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas. <43> <1> ~ <41> a step of imagewise exposing the lithographic printing plate precursor according to any one of the above items 1 to 5; a step of removing the image recording layer in non-image areas on a printing press by supplying at least one selected from the group consisting of a printing ink and a fountain solution to prepare a lithographic printing plate; and a step of printing with the obtained lithographic printing plate. Effect of the Invention

[0023] According to an embodiment of the present invention, it is possible to provide a lithographic printing plate precursor which provides a lithographic printing plate having excellent printing durability even when a UV ink is used. According to another embodiment of the present invention, there can be provided a method for producing a lithographic printing plate or a lithographic printing method using the above-mentioned lithographic printing plate precursor. [Brief description of the drawings]

[0024] [Figure 1] FIG. 2 is a schematic cross-sectional view of one embodiment of an aluminum support. [Diagram 2] FIG. 2 is a schematic cross-sectional view of another embodiment of an aluminum support. [Diagram 3] 1 is a graph showing an example of an alternating current waveform used in electrochemical graining treatment in a method for producing an aluminum support. [Figure 4] FIG. 2 is a side view showing an example of a radial cell in electrochemical graining treatment using an alternating current in a method for producing an aluminum support. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The contents of the present disclosure will be described in detail below. The following description of the components may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment. In this specification, the use of "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower limit and upper limit. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples. In addition, in the description of groups (atomic groups) in this specification, descriptions that do not indicate whether they are substituted or unsubstituted include those that have no substituents as well as those that have a substituent. For example, an "alkyl group" includes not only an alkyl group that has no substituents (unsubstituted alkyl groups) but also an alkyl group that has a substituent (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used as a concept including both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept including both acryloyl and methacryloyl. In addition, the term "step" in this specification includes not only an independent step, but also a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved. In addition, in this disclosure, "mass %" and "weight %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present disclosure, combinations of two or more preferred embodiments are more preferred embodiments. In addition, unless otherwise specified, the weight average molecular weight (Mw) and number average molecular weight (Mn) in the present disclosure are molecular weights detected by a gel permeation chromatography (GPC) analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all of which are product names manufactured by Tosoh Corporation) in a solvent of THF (tetrahydrofuran) and a differential refractometer, and converted using polystyrene as a standard substance. In this specification, the term "lithographic printing plate precursor" includes not only lithographic printing plate precursors but also throwaway plate precursors. Furthermore, the term "lithographic printing plate" includes not only lithographic printing plates prepared by subjecting a lithographic printing plate precursor to operations such as exposure and development as necessary, but also throwaway plates. In the case of a throwaway plate precursor, the operations of exposure and development are not necessarily required. Note that a throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when, for example, a portion of the page is printed in one color or two colors in color newspaper printing. The present disclosure will be described in detail below.

[0026] (lithographic printing plate original plate) The lithographic printing plate precursor according to the present disclosure has a support and an image recording layer on the support, the image recording layer containing an infrared absorber, a polymerization initiator, and polymer A, the weight average molecular weight of polymer A being more than 15,000 and not more than 150,000, and the ethylenically unsaturated bond valence of polymer A being 3.0 mmol / g or more. Furthermore, the lithographic printing plate precursor according to the present disclosure is a negative-working lithographic printing plate precursor, and can be suitably used as an on-press development type lithographic printing plate precursor.

[0027] As a result of extensive research, the present inventors have found that by adopting the above-mentioned configuration, it is possible to provide a lithographic printing plate precursor which provides excellent printing durability of the resulting lithographic printing plate, even when UV ink is used. Although the detailed mechanism by which the above effects are obtained is unclear, it is speculated as follows. It is believed that by containing polymer A, which has a weight-average molecular weight within a specific range and an ethylenically unsaturated bond valence of 3 mmol / g or more, in the image recording layer, the polymerization efficiency of the image area is increased and the crosslinking density is increased, resulting in excellent printing durability (especially UV printing durability).

[0028] Furthermore, the lithographic printing plate precursor according to the present disclosure contains, in the image recording layer, polymer A having a weight-average molecular weight within a specific range and an ethylenically unsaturated bond valence of 3.0 mmol / g or more. This suppresses loss of the image area due to ink penetration, dissolution by the ink, printing abrasion, and the like in the cured image area, and provides excellent plate skip suppression even when UV ink is used. "Plate skipping" refers to the phenomenon in which the image recording layer of a lithographic printing plate is thinned and ink cannot be applied to certain parts of the plate. The number of prints made before "plate skipping" occurs on a lithographic printing plate is an index of whether or not the plate is "resistant to plate skipping."

[0029] <Image recording layer> The image recording layer in the lithographic printing plate precursor according to the present disclosure contains an infrared absorber, a polymerization initiator, and polymer A, wherein the weight average molecular weight of polymer A is more than 15,000 and not more than 150,000, and the ethylenically unsaturated bond valence of polymer A is 3.0 mmol / g or more. The image recording layer in the present disclosure is a negative type image recording layer, and is preferably a water-soluble or water-dispersible negative type image recording layer. The image recording layer in the present disclosure is preferably an on-press development type image recording layer. Furthermore, the image recording layer in the present disclosure is preferably the outermost layer from the viewpoints of UV printing durability and UV plate skipping suppression. Each component contained in the image recording layer will be described in detail below.

[0030] -Polymer A- The image recording layer contains polymer A, and the weight average molecular weight of polymer A is more than 15,000 and not more than 150,000, and the ethylenically unsaturated bond valence of polymer A is 3.0 mmol / g or more. Up to now, no polymer has been known that satisfies the above-mentioned range of weight average molecular weight and has an ethylenically unsaturated bond valence of 3.0 mmol / g or more, which is an extremely large amount of ethylenically unsaturated bonds per unit mass.

[0031] The weight average molecular weight (Mw) of the above polymer A is more than 15,000 and not more than 150,000. From the viewpoints of UV printing durability and UV plate skipping suppression, it is preferably from 20,000 to 150,000, more preferably from 40,000 to 150,000, and particularly preferably from 70,000 to 150,000. From the viewpoint of developability, the weight average molecular weight of the polymer A is preferably 130,000 or less.

[0032] The weight average molecular weight Mw of the polymer A or the polymerizable compound B described below is measured by the following measuring device and method. GPC measuring equipment: TOSOH HLC-8320GPC (manufactured by Tosoh Corporation) GPC mobile phase: Tetrahydrofuran (THF) Inspection equipment: Refractive index detector (RI) Flow rate: 0.35mL / min Columns: TSKgel SuperHZM-M, TSKgel SuperHZ4000, TSKgel SuperHZ3000, and TSKgel SuperHZ2000 (all manufactured by Tosoh Corporation) are used in combination. Column temperature: 40℃ Standard sample for molecular weight calibration curve: Polystyrene (PS)

[0033] The ethylenically unsaturated bond valence (also referred to as "C=C valence") of the above polymer A is 3.0 mmol / g or more, and from the viewpoints of UV printing durability and UV plate skipping suppression, it is preferably 4.0 mmol / g or more, more preferably 5.0 mmol / g or more, more preferably 4.5 mmol / g to 12.0 mmol / g, even more preferably 5.0 mmol / g to 10.0 mmol / g, and particularly preferably 5.5 mmol / g to 8.5 mmol / g.

[0034] The ethylenically unsaturated bond valence in the polymer A or the polymerizable compound B described below can be determined by the following method. First, for a given sample amount (e.g., 0.2 g) of a compound, the structure of the compound is identified using, for example, pyrolysis GC / MS, FT-IR, NMR, TOF-SIMS, etc., and the total amount (mmol) of ethylenically unsaturated groups is determined. The ethylenically unsaturated bond valence of the compound is calculated by dividing the determined total amount (mmol) of ethylenically unsaturated groups by the sample amount (g) of the compound.

[0035] The structure of the polymer A is not particularly limited and may be, for example, a graft polymer, a star polymer, a hyperbranched polymer, a dendrimer, or the like. As described below, preferred examples of the polymer A include a polymer in which the terminal isocyanate group of a multimer (including an adduct) of a polyfunctional isocyanate compound is blocked with a compound having an ethylenically unsaturated group.

[0036] From the viewpoints of UV printing durability and UV plate skipping suppression, the above polymer A preferably has a hydrogen-bonding group, and more preferably has three or more hydrogen-bonding groups. The hydrogen-bonding group may be any group capable of forming a hydrogen bond, and may be a hydrogen-bond donating group, a hydrogen-bond accepting group, or both. Examples of the hydrogen-bonding group include a hydroxy group, a carboxy group, an amino group, a carbonyl group, a sulfonyl group, a urethane group, a urea group, an imide group, an amide group, and a sulfonamide group. Among these, from the viewpoints of UV printing durability and UV plate skipping suppression, the hydrogen-bonding group is preferably at least one group selected from the group consisting of a urethane group, a urea group, an imide group, an amide group, and a sulfonamide group, more preferably at least one group selected from the group consisting of a urethane group, a urea group, an imide group, and an amide group, even more preferably at least one group selected from the group consisting of a urethane group, a urea group, and an imide group, and particularly preferably at least one group selected from the group consisting of a urethane group and a urea group.

[0037] Moreover, from the viewpoints of UV printing durability and UV plate skipping suppression, the polymer A preferably has a polymerizable group. The polymerizable group may be, for example, a cationic polymerizable group or a radically polymerizable group, but from the viewpoint of reactivity, a radically polymerizable group is preferable. The polymerizable group is not particularly limited, but from the viewpoints of reactivity, UV printing durability, and UV plate skipping suppression, it is preferably an ethylenically unsaturated group, more preferably at least one group selected from the group consisting of a vinylphenyl group (styryl group), a vinyl ester group, a vinyl ether group, an allyl group, a (meth)acryloxy group, and a (meth)acrylamide group, even more preferably at least one group selected from the group consisting of a vinylphenyl group (styryl group), a (meth)acryloxy group, and a (meth)acrylamide group, and particularly preferably a (meth)acryloxy group.

[0038] Furthermore, from the viewpoints of UV printing durability and UV plate skipping suppression, the polymerizable group of the polymer A is preferably a structure represented by the following formula (Po-1) or formula (Po-2), and more preferably a structure represented by the following formula (Po-1).

[0039] [ka]

[0040] In formula (Po-1) and formula (Po-2), R P each independently represents an acrylic group or a methacrylic group, and the wavy line portion represents the bonding position to other structures.

[0041] In formula (Po-1) or formula (Po-2), R P It is preferable that all of the groups are the same. In addition, in formula (Po-1) or formula (Po-2), R P is preferably an acrylic group.

[0042] From the viewpoints of UV printing durability and UV plate skipping suppression, the polymer A is preferably a (meth)acrylate compound having a urethane group, that is, a urethane (meth)acrylate. Furthermore, from the viewpoints of UV printing durability and UV plate skipping suppression, the above polymer A preferably has a structure in which a polyfunctional isocyanate compound is polymerized, and more preferably has a structure in which a bifunctional isocyanate compound is polymerized. From the viewpoints of UV printing durability and UV plate skipping suppression, the polymer A is preferably a polymer obtained by reacting a polyfunctional ethylenically unsaturated compound having a hydroxy group (also referred to as a "hydroxyl group") at the end of a polymer obtained by polymerizing a polyfunctional isocyanate compound (including an adduct of a polyfunctional alcohol compound such as a trimethylolpropane adduct), more preferably a polymer obtained by reacting a polyfunctional ethylenically unsaturated compound having a hydroxy group at the end of a polymer obtained by polymerizing a bifunctional isocyanate compound (including an adduct of a polyfunctional alcohol compound), and particularly preferably a polymer obtained by reacting a polyfunctional ethylenically unsaturated compound having a hydroxy group at the end of a polymer obtained by polymerizing hexamethylene diisocyanate (including an adduct of a polyfunctional alcohol compound). The polyfunctional isocyanate compound is not particularly limited, and any known compound can be used. It may be an aliphatic polyfunctional isocyanate compound or an aromatic polyfunctional isocyanate compound. Specific examples of the polyfunctional isocyanate compound include 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 9H-fluorene-2,7-diisocyanate, and 9H-fluoren-9-one-2,7-diisocyanate. Preferred examples of the polyisocyanate include 4,4'-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 2,2-bis(4-isocyanatophenyl)hexafluoropropane, 1,5-diisocyanatonaphthalene, and dimers and trimers (isocyanurate bonds) of these polyisocyanates. In addition, biuret compounds obtained by reacting the above polyisocyanate compounds with known amine compounds may be used. The polyfunctional ethylenically unsaturated compound having a hydroxy group is preferably a trifunctional or higher ethylenically unsaturated compound having a hydroxy group, and more preferably a pentafunctional or higher ethylenically unsaturated compound having a hydroxy group. Furthermore, the polyfunctional ethylenically unsaturated compound having a hydroxy group is preferably a polyfunctional (meth)acrylate compound having a hydroxy group.

[0043] From the viewpoints of UV printing durability and UV plate skipping suppression, the above polymer A preferably has at least one structure selected from the group consisting of an adduct structure, a biuret structure, and an isocyanurate structure, more preferably has at least one structure selected from the group consisting of a trimethylolpropane adduct structure, a biuret structure, and an isocyanurate structure, and particularly preferably has a trimethylolpropane adduct structure. From the viewpoints of UV printing durability and UV plate skipping suppression, the polymer A preferably has a structure represented by any one of the following formulas (A-1) to (A-3), and more preferably has a structure represented by the following formula (A-1).

[0044] [ka]

[0045] In formula (A-1), R A1 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and the wavy line portion represents the bonding position to other structures.

[0046] R in formula (A-1) A1 From the viewpoints of UV printing durability and UV plate skipping suppression, is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably an ethyl group.

[0047] The above polymer A preferably contains a resin represented by the following formula (I). A P -(B P ) nP Formula (I) In formula (I), A P represents an organic group having a valence of nP and a hydrogen-bonding group; B P represents a group having two or more polymerizable groups, and nP represents an integer of 2 or more.

[0048] A in formula (I) P The preferred embodiments of the hydrogen-bonding group in are the same as the preferred embodiments of the hydrogen-bonding group described above. A in formula (I) P is preferably an organic group having no ethylenically unsaturated bond. In addition, A in formula (I) Pis preferably a group formed by combining two or more structures selected from the group consisting of monovalent to nP-valent aliphatic hydrocarbon groups, monovalent to nP-valent aromatic hydrocarbon groups, urethane bonds, urea bonds, biuret bonds, and allophanate bonds, and more preferably a group formed by combining two or more structures selected from the group consisting of monovalent to nP-valent aliphatic hydrocarbon groups, monovalent to nP-valent aromatic hydrocarbon groups, urethane bonds, urea bonds, and biuret bonds. Further, A in formula (I) P From the viewpoints of UV printing durability and UV plate skipping suppression, is preferably a group obtained by removing a terminal isocyanate group from a polymer (including an adduct of a polyfunctional alcohol compound such as a trimethylolpropane adduct) obtained by polymerizing a polyfunctional isocyanate compound, more preferably a group obtained by removing a terminal isocyanate group from a polymer (including an adduct of a polyfunctional alcohol compound) obtained by polymerizing a bifunctional isocyanate compound, and particularly preferably a group obtained by removing a terminal isocyanate group from a polymer (including an adduct of a polyfunctional alcohol compound) obtained by polymerizing hexamethylene diisocyanate. In addition, A in formula (I) P From the viewpoints of UV printing durability and UV plate skipping suppression, the weight average molecular weight (Mw) of the resin is preferably from 10,000 to 145,000, more preferably from 30,000 to 140,000, and particularly preferably from 60,000 to 140,000. From the viewpoint of developability, A in formula (I) P The weight average molecular weight is preferably 120,000 or less.

[0049] B in formula (I) P The preferred embodiments of the polymerizable group in are the same as the preferred embodiments of the polymerizable group described above. Among them, B of formula (I) P From the viewpoints of UV printing durability and UV plate skipping suppression, the polymerizable group in B of formula (I) preferably contains a (meth)acryloxy group. Pis more preferably a group having 3 or more (meth)acryloxy groups, even more preferably a group having 5 or more (meth)acryloxy groups, and particularly preferably a group having 5 to 12 (meth)acryloxy groups. In addition, B in formula (I) P are each independently preferably a structure represented by the above formula (Po-1) or formula (Po-2), and more preferably a structure represented by the above formula (Po-1), from the viewpoints of UV printing durability and UV plate skipping suppression. Furthermore, B of formula (I) P It is preferable that all of the groups are the same. In addition, B in formula (I) P From the viewpoints of UV printing durability and UV plate skipping suppression, the molecular weight of the resin is preferably 300 or more and 1,000 or less, and more preferably 400 or more and 800 or less.

[0050] In addition, in formula (I), A P Weight average molecular weight / (B P From the viewpoints of UV printing durability and UV plate skipping suppression, the value of (molecular weight x nP) is preferably 1 or less, more preferably 0.1 to 0.9, and particularly preferably 0.2 to 0.8.

[0051] The polymer A may be used alone or in combination of two or more kinds. From the viewpoints of UV printing durability and UV plate skipping suppression, it is preferred that the image recording layer contains two or more kinds of polymer A. In addition, the polymer A may be a binder polymer in the image recording layer, or may be in the form of polymer particles. From the viewpoints of developability, UV printing durability, and UV plate skip suppression, the content of the polymer A in the image recording layer is preferably 5% by mass to 95% by mass, more preferably 10% by mass to 90% by mass, even more preferably 20% by mass to 90% by mass, and particularly preferably 50% by mass to 90% by mass, relative to the total mass of the image recording layer.

[0052] -Polymerizable compound B- From the viewpoints of UV printing durability and UV plate skipping suppression, it is preferable that the image recording layer further contains a polymerizable compound B having a weight average molecular weight of 1,000 or more and 15,000 or less.

[0053] The polymerizable compound B may be, for example, a radically polymerizable compound or a cationic polymerizable compound, but is preferably a radically polymerizable compound, and more preferably a compound having an ethylenically unsaturated group. The structure of the polymerizable compound B is not particularly limited, and a known oligomer can be used. Preferred examples thereof include a urethane (meth)acrylate compound and a star-shaped polymer. The polymerizable compound B is preferably a polyfunctional polymerizable compound. Furthermore, the polymerizable compound B preferably contains a polyfunctional polymerizable compound having 3 to 40 functionalities, more preferably a polyfunctional polymerizable compound having 5 to 30 functionalities, and particularly preferably a polyfunctional polymerizable compound having 10 to 20 functionalities. The preferred embodiments of the polymerizable group in the polymerizable compound B are the same as the preferred embodiments of the polymerizable group in the polymer A described above.

[0054] From the viewpoints of UV printing durability and UV plate skipping suppression, the polymerizable compound B preferably contains a compound having an ethylenically unsaturated bond valence of 1.0 mmol / g or more, more preferably contains a compound having an ethylenically unsaturated bond valence of 2.0 mmol / g to 12.0 mmol / g, and particularly preferably contains a compound having an ethylenically unsaturated bond valence of 5.0 mmol / g to 10.0 mmol / g.

[0055] From the viewpoints of UV printing durability and UV plate skipping suppression, the weight average molecular weight (Mw) of the polymerizable compound B is preferably 2,000 or more and 15,000 or less, more preferably 3,000 or more and 15,000 or less, even more preferably 5,000 or more and 15,000 or less, and particularly preferably 10,000 or more and 15,000 or less.

[0056] The urethane (meth)acrylate compound is not particularly limited, but examples thereof include compounds obtained by reacting a polyisocyanate compound with a compound having a hydroxy group and a (meth)acryloxy group.

[0057] The polyisocyanate compound may be a difunctional to pentafunctional polyisocyanate compound, and a difunctional or trifunctional polyisocyanate compound is preferred. Examples of the polyisocyanate compound include the polyisocyanate compounds described above in connection with Polymer A.

[0058] As the compound having a hydroxy group and a (meth)acryloxy group, a compound having one hydroxy group and one or more (meth)acryloxy groups is preferable, and a compound having one hydroxy group and two or more (meth)acryloxy groups is more preferable. Examples of compounds having a hydroxy group and a (meth)acryloxy group include hydroxyethyl (meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol penta(meth)acrylate.

[0059] The urethane (meth)acrylate compound is, for example, preferably a compound having at least a group represented by the following formula (Ac-1) or formula (Ac-2), and more preferably a compound having at least a group represented by the following formula (Ac-1).

[0060] [ka]

[0061] In formula (Ac-1) and formula (Ac-2), L 1 ~L 4 each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and the wavy line portion represents the bonding position to other structures.

[0062] L 1 ~L 4 are each independently preferably an alkylene group having 2 to 20 carbon atoms, more preferably an alkylene group having 2 to 10 carbon atoms, and further preferably an alkylene group having 4 to 8 carbon atoms. In addition, the alkylene group may have a branched or cyclic structure, but is preferably a linear alkylene group.

[0063] It is preferred that the wavy line moieties in formula (Ac-1) or formula (Ac-2) are each independently directly bonded to the wavy line moieties in the groups represented by formula (Ae-1) or formula (Ae-2) below.

[0064] [ka]

[0065] In formula (Ae-1) and formula (Ae-2), R each independently represents an acryloyloxy group or a methacryloyloxy group, and the wavy line portion represents the bonding position to the wavy line portion in formula (Ac-1) and formula (Ac-2).

[0066] In addition, as the urethane (meth)acrylate compound, a compound obtained by introducing a (meth)acryloxy group by a polymer reaction into a polyurethane obtained by reacting a polyisocyanate compound with a polyol compound may be used. For example, a urethane (meth)acrylate compound may be obtained by reacting a compound having an epoxy group and a (meth)acryloxy group with a polyurethane oligomer obtained by reacting a polyol compound having an acid group with a polyisocyanate compound.

[0067] As the star polymer, any known star polymer can be used, but a star polymer having a sulfide bond is preferable, and a star polymer containing a constituent unit derived from a multifunctional thiol compound having from 3 to 10 functionalities is more preferable. In addition, it is preferable that the polyfunctional thiol compound has a polymer chain bonded to a sulfide bond, and the polymer chain preferably has an ethylenically unsaturated group, and more preferably has a structural unit having an ethylenically unsaturated group. The star polymer preferably has only one constitutional unit derived from a polyfunctional thiol compound having from 3 to 10 functionalities. When the star polymer is a star macromolecule, it is preferably an n-star macromolecule, where n is an integer of 3-10. The star polymer may be a regular star macromolecule or a variegated star macromolecule. The star polymer can be produced by a known method such as a method of copolymerizing a monomer in the presence of a multifunctional thiol compound having 3 to 10 functionalities. For details of the method of producing the star polymer and the multifunctional thiol compound, the description in JP2012-148555A can be referred to.

[0068] The multifunctional thiol compound having 3 or more and 10 or less functionalities used in the present disclosure is not particularly limited, but is preferably a multifunctional thiol compound having 3 or more and 8 or less functionalities, and more preferably a multifunctional thiol compound having 3 or more and 6 or less functionalities. In addition, the polyfunctional thiol compound having 3 to 10 functionalities used in the present disclosure is preferably a compound represented by the following formula S-1.

[0069] [ka]

[0070] In formula S-1, L S represents an ns-valent hydrocarbon group which may contain an ether bond, R S represents a monovalent hydrocarbon group having a thiol group as a substituent, and ns represents an integer of 3 to 10. In formula S-1, L S is preferably an ns-valent aliphatic hydrocarbon group which may contain an ether bond, and more preferably an ns-valent unsaturated aliphatic hydrocarbon group which may contain an ether bond. L S Specific examples of the above include structures in which all hydroxy groups contained in a polyhydric alcohol compound such as pentaerythritol, dipentaerythritol, sorbitol, mannitol, iditol, dulcitol, or inositol have been removed, but are not limited thereto. In formula S-1, R S is preferably a monovalent aliphatic hydrocarbon group having a thiol group as a substituent, and more preferably a monovalent unsaturated aliphatic hydrocarbon group having a thiol group as a substituent. R S Specific examples of the mercapto group include, but are not limited to, a mercaptomethyl group, a 2-mercaptoethyl group, and a 2-mercaptopropyl group. In formula S-1, ns represents an integer of 3 to 10, preferably an integer of 3 to 8, and more preferably an integer of 3 to 6.

[0071] In addition, as the polyfunctional thiol compound, compounds A to F described in JP-A-2012-148555 can also be suitably used.

[0072] The introduction of a polymerizable group into the star polymer is not particularly limited, and may be carried out by a polymer reaction, or a polymer chain having an ethylenically unsaturated group may be introduced.

[0073] Star polymers include, for example, those described in WO 2019 / 151361.

[0074] The polymerizable compound B may be used alone or in combination of two or more kinds. From the viewpoints of developability, UV printing durability, and UV plate skip suppression, the content of the polymerizable compound B in the image recording layer is preferably 0.1% by mass to 50% by mass, more preferably 1% by mass to 40% by mass, and particularly preferably 5% by mass to 30% by mass, relative to the total mass of the image recording layer.

[0075] -Polymerizable compound C- From the viewpoints of UV printing durability and UV plate skipping suppression, it is preferable that the image recording layer further contains a polymerizable compound C having a molecular weight of less than 1,000. In addition, it is preferable that the polymerizable compound C contains a polymerizable compound having a molecular weight of 100 or more and less than 1,000. The polymerizable compound C used in the present disclosure may be, for example, a radical polymerizable compound or a cationic polymerizable compound, but is preferably a radical polymerizable compound, and more preferably a compound having an ethylenically unsaturated group (ethylenically unsaturated compound).The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, and more preferably a compound having two or more terminal ethylenically unsaturated bonds.

[0076] Examples of the monomer include unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), their esters, and amides. Preferably, esters of unsaturated carboxylic acids and polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and polyvalent amine compounds are used. In addition, addition reaction products of unsaturated carboxylic acid esters or amides having nucleophilic substituents such as hydroxyl groups, amino groups, and mercapto groups with monofunctional or polyfunctional isocyanates or epoxy groups, and dehydration condensation reaction products of monofunctional or polyfunctional carboxylic acids are also preferably used. In addition, addition reaction products of unsaturated carboxylic acid esters or amides having electrophilic substituents such as isocyanate groups and epoxy groups with monofunctional or polyfunctional alcohols, amines, and thiols, and substitution reaction products of unsaturated carboxylic acid esters or amides having eliminative substituents such as halogen atoms and tosyloxy groups with monofunctional or polyfunctional alcohols, amines, and thiols are also suitable. As another example, it is also possible to use a compound group in which the above unsaturated carboxylic acid is replaced with an 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, 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, JP-A-10-333321, and the like.

[0077] Specific examples of ester monomers of polyhydric alcohol compounds and unsaturated carboxylic acids include acrylic esters such as ethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, isocyanuric acid ethylene oxide (EO) modified triacrylate, and polyester acrylate oligomers. Examples of methacrylic acid esters include tetramethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, pentaerythritol trimethacrylate, bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane, and bis[p-(methacryloxyethoxy)phenyl]dimethylmethane. Specific examples of amide monomers of polyamine compounds and unsaturated carboxylic acids include methylene bisacrylamide, methylene bismethacrylamide, 1,6-hexamethylene bisacrylamide, 1,6-hexamethylene bismethacrylamide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, and xylylene bismethacrylamide.

[0078] Also suitable are urethane-based addition polymerizable compounds produced by an addition reaction between an isocyanate and a hydroxy group. Specific examples thereof include vinyl urethane compounds containing two or more polymerizable vinyl groups in one molecule, which are obtained by adding a vinyl monomer containing a hydroxy group represented by the following formula (M) to a polyisocyanate compound having two or more isocyanate groups in one molecule, as described in JP-B-48-41708. CH2=C(R M4 )COOCH2CH(R M5)OH (M) In formula (M), R M4 and R M5 each independently represents a hydrogen atom or a methyl group.

[0079] In addition, 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, JP-B-58-49860, JP-B-56-17654, JP-B-62-39417, and JP-B-62-39418 Also suitable are urethane compounds having an ethylene oxide skeleton described in JP-A-2000-250211 and JP-A-2007-94138, and urethane compounds having a hydrophilic group described in U.S. Pat. No. 7,153,632, JP-T-8-505958, JP-A-2007-293221 and JP-A-2007-293223.

[0080] The polymerizable compound C may contain a compound having one or two ethylenically unsaturated groups (hereinafter, also referred to as specific compound B2). The polymerizable group in the specific compound B2 may be, for example, a cationically polymerizable group or a radically polymerizable group, but from the viewpoint of reactivity, a radically polymerizable group is preferable. The polymerizable group is not particularly limited, but from the viewpoints of reactivity and printing durability, it is preferably an ethylenically unsaturated group, more preferably at least one group selected from the group consisting of a vinylphenyl group (styryl group), a vinyl ester group, a vinyl ether group, an allyl group, a (meth)acryloxy group, and a (meth)acrylamide group, even more preferably at least one group selected from the group consisting of a vinylphenyl group (styryl group), a (meth)acryloxy group, and a (meth)acrylamide group, and particularly preferably a (meth)acryloxy group. Moreover, the specific compound B2 is preferably a compound having two ethylenically unsaturated bond groups (that is, a bifunctional polymerizable compound).

[0081] From the viewpoints of on-press developability and printing durability, the specific compound B2 is preferably a methacrylate compound, that is, a compound having a methacryloxy group.

[0082] From the viewpoint of on-press developability, the specific compound B2 preferably contains an alkyleneoxy structure or a urethane bond.

[0083] The molecular weight of the specific compound B2 (when the compound has a molecular weight distribution, the weight average molecular weight) is preferably 50 or more and less than 1,000, more preferably 200-900, and further preferably 250-800.

[0084] Specific examples of the specific compound B2 are listed below, but the specific compound B2 used in the present disclosure is not limited to these. In addition, for example, in the compound (2) below, n+m=10,

[0085] [ka]

[0086] As the specific compound B2, the following commercially available products may be used, but the specific compound B2 used in the present disclosure is not limited thereto. Specific examples of the specific compound B2 include ethoxylated bisphenol A dimethacrylates such as BPE-80N (compound (1) above), BPE-100, BPE-200, and BPE-500 manufactured by Shin-Nakamura Chemical Co., Ltd., and CN104 (compound (1) above) manufactured by Sartomer Corporation. Specific examples of the specific compound B2 include ethoxylated bisphenol A diacrylates such as A-BPE-10 (the compound (2) above) and A-BPE-4 manufactured by Shin-Nakamura Chemical Co., Ltd. Further, specific examples of the specific compound B2 include bifunctional methacrylates such as FST 510 manufactured by AZ Electronics.

[0087] Here, the above-mentioned "FST 510" is a reaction product of 1 mole of 2,2,4-trimethylhexamethylene diisocyanate and 2 moles of hydroxyethyl methacrylate, and is an 82 mass % solution of the above-mentioned compound (3) in methyl ethyl ketone.

[0088] From the viewpoints of on-press developability and printing durability, the content of specific compound B2 is preferably 1% by mass to 60% by mass, more preferably 5% by mass to 55% by mass, and even more preferably 5% by mass to 50% by mass, relative to the total mass of the image recording layer.

[0089] The polymerizable compound C may be used alone or in combination of two or more kinds. From the viewpoints of developability, UV printing durability, and UV plate skip suppression, the content of the polymerizable compound C in the image recording layer is preferably 1% by mass to 75% by mass, more preferably 3% by mass to 70% by mass, and particularly preferably 5% by mass to 60% by mass, relative to the total mass of the image recording layer.

[0090] -Infrared absorbent- The image recording layer contains an infrared absorbing agent. The infrared absorbing agent is not particularly limited, and examples thereof include pigments and dyes. As the dye to be used as the infrared absorber, commercially available dyes and known dyes described in literature such as "Dye Handbook" (edited by the Organic Synthesis Chemistry Association, published in 1970) can be used. Specific examples of the dye include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complex dyes.

[0091] Particularly preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes.Furthermore, cyanine dyes and indolenine cyanine dyes are also included.Of these, cyanine dyes are particularly preferred.

[0092] The infrared absorbing agent is preferably a cationic polymethine dye having an oxygen or nitrogen atom at the meso position. Preferred examples of the cationic polymethine dye include cyanine dyes, pyrylium dyes, thiopyrylium dyes, and azulenium dyes, and from the viewpoints of availability, solubility in a solvent during the introduction reaction, and the like, cyanine dyes are preferred.

[0093] Specific examples of cyanine dyes include the compounds described in paragraphs 0017 to 0019 of JP-A-2001-133969, the compounds described in paragraphs 0016 to 0021 of JP-A-2002-023360, and the compounds described in paragraphs 0012 to 0037 of JP-A-2002-040638, preferably the compounds described in paragraphs 0034 to 0041 of JP-A-2002-278057, and the compounds described in paragraphs 0080 to 0086 of JP-A-2008-195018, and particularly preferably the compounds described in paragraphs 0035 to 0043 of JP-A-2007-90850, and the compounds described in paragraphs 0105 to 0113 of JP-A-2012-206495. In addition, the compounds described in paragraphs 0008 to 0009 of JP-A No. 5-5005 and paragraphs 0022 to 0025 of JP-A No. 2001-222101 can also be preferably used. As the pigment, the compounds described in paragraphs 0072 to 0076 of JP-A No. 2008-195018 are preferred.

[0094] The infrared absorbing agent may be used alone or in combination of two or more kinds. Also, a pigment and a dye may be used in combination as the infrared absorbing agent. The content of the infrared absorbing agent in the image recording layer is preferably from 0.1% by mass to 10.0% by mass, and more preferably from 0.5% by mass to 5.0% by mass, based on the total mass of the image recording layer.

[0095] -Polymerization initiator- The image recording layer in the lithographic printing plate precursor according to the present disclosure contains a polymerization initiator. The polymerization initiator preferably contains an electron-accepting polymerization initiator, and more preferably contains an electron-accepting polymerization initiator and an electron-donating polymerization initiator.

[0096] <<Electron-accepting polymerization initiator>> The image recording layer preferably contains an electron-accepting polymerization initiator as the polymerization initiator. The electron-accepting polymerization initiator is a compound that generates a polymerization initiating species such as a radical by accepting one electron through intermolecular electron transfer when electrons of an infrared absorbing agent are excited by exposure to infrared light. 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 can be appropriately selected from known thermal polymerization initiators, compounds having a bond with small bond dissociation energy, photopolymerization initiators, and the like. As the electron-accepting polymerization initiator, a radical polymerization initiator is preferable, and an onium salt compound is more preferable. The electron-accepting polymerization initiator is preferably an infrared-sensitive polymerization initiator. Examples of the electron-accepting radical polymerization initiator include (a) organic halides, (b) carbonyl compounds, (c) azo compounds, (d) organic peroxides, (e) metallocene compounds, (f) azide compounds, (g) hexaarylbiimidazole compounds, (i) disulfone compounds, (j) oxime ester compounds, and (k) onium salt compounds.

[0097] As the (a) organic halide, for example, the compounds described in paragraphs 0022 to 0023 of JP-A No. 2008-195018 are preferable. As the (b) carbonyl compound, for example, the compound described in paragraph 0024 of JP-A-2008-195018 is preferable. As the (c) azo compound, for example, the azo compounds described in JP-A-8-108621 can be used. (d) As the organic peroxide, for example, the compound described in paragraph 0025 of JP-A-2008-195018 is preferable. (e) As the metallocene compound, for example, the compound described in paragraph 0026 of JP-A-2008-195018 is preferable. (f) Examples of the azide compounds include 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone. (g) Preferred examples of the hexaarylbiimidazole compound include the compounds described in paragraph 0027 of JP-A-2008-195018. (i) Examples of the disulfone compound include the compounds described in JP-A-61-166544 and JP-A-2002-328465. As the (j) oxime ester compound, for example, the compounds described in paragraphs 0028 to 0030 of JP-A No. 2008-195018 are preferable.

[0098] Among the electron-accepting polymerization initiators, preferred from the viewpoint of curability are oxime ester compounds and onium salt compounds. Among them, from the viewpoint of printing durability, preferred are iodonium salt compounds, sulfonium salt compounds and azinium salt compounds, more preferred are iodonium salt compounds and sulfonium salt compounds, and particularly preferred are iodonium salt compounds. Specific examples of these compounds are shown below, but the present disclosure is not limited thereto.

[0099] Preferred examples of the iodonium salt compound include diaryliodonium salt compounds, more preferred are diphenyliodonium salt compounds substituted with electron-donating groups such as alkyl groups or alkoxy groups, and more preferred are asymmetric diphenyliodonium salt compounds. Specific examples include diphenyliodonium hexafluorophosphate, 4-methoxyphenyl-4-(2-methylpropyl)phenyliodonium hexafluorophosphate, 4-(2-methylpropyl)phenyl-p-tolyliodonium hexafluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium tetrafluoroborate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, and bis(4-t-butylphenyl)iodonium hexafluorophosphate.

[0100] As an example of the sulfonium salt compound, a triarylsulfonium salt compound is preferred, particularly a triarylsulfonium salt compound in which at least a part of the electron-withdrawing group, for example, the group on the aromatic ring, is substituted with a halogen atom, and more preferably a triarylsulfonium salt compound in which the total number of halogen atoms substituted on the aromatic ring is 4 or more. Specific examples include triphenylsulfonium hexafluorophosphate, triphenylsulfonium benzoylformate, bis(4-chlorophenyl)phenylsulfonium benzoylformate, bis(4-chlorophenyl)-4-methylphenylsulfonium tetrafluoroborate, tris(4-chlorophenyl)sulfonium 3,5-bis(methoxycarbonyl)benzenesulfonate, tris(4-chlorophenyl)sulfonium hexafluorophosphate, and tris(2,4-dichlorophenyl)sulfonium hexafluorophosphate.

[0101] Examples of the counter anion of the iodonium salt compound and the sulfonium salt compound include a sulfonate anion, a carboxylate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, a p-toluenesulfonate anion, a tosylate anion, a sulfonamide anion, and a sulfonimide anion. Among the above, a sulfonamide anion or a sulfonimide anion is preferred, and a sulfonimide anion is more preferred. The sulfonamide anion is preferably an arylsulfonamide anion. The sulfonimide anion is preferably a bisarylsulfonimide anion. Specific examples of sulfonamide anions or sulfonimide anions are shown below, but the present disclosure is not limited thereto. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group.

[0102] [ka]

[0103] In addition, from the viewpoints of visibility over time after exposure, developability, and UV printing durability of the resulting lithographic printing plate, the electron-accepting polymerization initiator preferably contains a compound represented by the following formula (II) or formula (III), and particularly preferably contains a compound represented by formula (II).

[0104] [ka]

[0105] In formula (II) and formula (III), X A represents a halogen atom, and R A , R A1 and R A2 each independently represents a monovalent hydrocarbon group having 1 to 20 carbon atoms.

[0106] R in formula (II) Ais preferably an aryl group. X in formula (II) and formula (III) A Examples of the fluorine atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a chlorine atom or a bromine atom is preferred because of its excellent sensitivity, and a bromine atom is particularly preferred. In addition, in formula (II) and formula (III), R A , R A1 and R A2 are each independently preferably an aryl group, and among these, from the viewpoint of achieving an excellent balance between sensitivity and storage stability, an aryl group substituted with an amide group is more preferable.

[0107] Moreover, it is particularly preferable that the electron-accepting polymerization initiator contains a compound represented by formula (IV).

[0108] [ka]

[0109] In formula (IV), X A represents a halogen atom, and R A3 and R A4 each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, and pA and qA each independently represent an integer of 1 to 5, provided that pA+qA=2 to 6.

[0110] Specific examples of the electron-accepting polymerization initiator include the compounds shown below, but the present disclosure is not limited thereto. In the compounds shown below, Et is an ethyl group. n Pr is n-propyl group. n C4H9 is an n-butyl group, cHex is a cyclohexyl group, n C5H 11 is an n-pentyl group, t C5H 11 is a t-pentyl group, Ph is a phenyl group, n C8H 17 is an n-octyl group, t Bu is a t-butyl group. nBu is an n-butyl group. n C 12 H 25 represents an n-decyl group.

[0111] [ka]

[0112] [ka]

[0113] [ka]

[0114] [ka]

[0115] [ka]

[0116] [ka]

[0117] [ka]

[0118] The lowest unoccupied molecular orbital (LUMO) of the electron-accepting polymerization initiator is preferably −3.00 eV or less, and more preferably −3.02 eV or less, from the viewpoints of improving sensitivity and preventing plate skipping. The lower limit is preferably −3.80 eV or more, and more preferably −3.60 eV or more.

[0119] The electron-accepting polymerization initiator may be used alone or in combination of two or more kinds. The content of the electron-accepting polymerization initiator is preferably 0.1% by mass to 50% by mass, more preferably 0.5% by mass to 30% by mass, and particularly preferably 0.8% by mass to 20% by mass, based on the total mass of the image recording layer.

[0120] <<Electron-donating polymerization initiator (polymerization aid)>> The image recording layer preferably contains, as a polymerization initiator, an electron-donating polymerization initiator (also called a "polymerization auxiliary"), and more preferably contains an electron-accepting polymerization initiator and an electron-donating polymerization initiator. The electron-donating polymerization initiator in the present disclosure is a compound that, when an electron of an infrared absorber is excited or moves intramolecularly by exposure to infrared light, donates one electron to an orbital of the infrared absorber from which one electron has been lost through intermolecular electron transfer, thereby generating a polymerization initiating species such as a radical. The electron-donating polymerization initiator is preferably an electron-donating radical polymerization initiator. From the viewpoint of improving the printing durability of the lithographic printing plate, the image recording layer more preferably contains an electron-donating polymerization initiator as described below, examples of which include the following five types. (i) Alkyl or aryl ate complexes: It is believed that the carbon-hetero bond is oxidatively cleaved to generate an active radical. Specifically, borate compounds are preferred. (ii) N-arylalkylamine compounds: It is believed that the CX bond on the carbon adjacent to the nitrogen is cleaved by oxidation to generate an active radical. X is preferably a hydrogen atom, a carboxyl group, a trimethylsilyl group, or a benzyl group. Specific examples include N-phenylglycines (which may or may not have a substituent on the phenyl group) and N-phenyliminodiacetic acids (which may or may not have a substituent on the phenyl group). (iii) Sulfur-containing compounds: The above-mentioned amines in which the nitrogen atom is replaced with a sulfur atom can generate active radicals by the same action, such as phenylthioacetic acid (which may or may not have a substituent on the phenyl group). (iv) Tin-containing compounds: Compounds in which the nitrogen atom of the above-mentioned amines is replaced with a tin atom can generate active radicals by the same action. (v) Sulfinates: capable of generating active radicals by oxidation. Specific examples include sodium arylsulfinates.

[0121] Among these, from the viewpoint of printing durability, the image recording layer preferably contains a borate compound. From the viewpoints of printing durability and color development, the borate compound is preferably a tetraarylborate compound or a monoalkyltriarylborate compound, and more preferably a tetraarylborate compound. 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.

[0122] A specific example of a preferred borate compound is sodium tetraphenylborate.

[0123] Preferred specific examples of the electron-donating polymerization initiator include, but are not limited to, B-1 to B-9. In the following chemical formulas, Ph represents a phenyl group, and Bu represents an n-butyl group.

[0124] [ka]

[0125] In addition, the highest occupied molecular orbital (HOMO) of the electron donating polymerization initiator used in the present disclosure is preferably −6.00 eV or more, more preferably −5.95 eV or more, and even more preferably −5.93 eV or more, from the viewpoints of improving sensitivity and preventing plate skipping. The upper limit is preferably −5.00 eV or less, and more preferably −5.40 eV or less.

[0126] The electron-donating polymerization initiator may be added either alone or in combination of two or more kinds. From the viewpoints of sensitivity and printing durability, 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 even more preferably 0.1% by mass to 20% by mass, relative to the total mass of the image recording layer.

[0127] In the present disclosure, when the image recording layer contains an onium ion and an anion in the above-mentioned electron-donating polymerization initiator, the image recording layer contains an electron-accepting polymerization initiator and the above-mentioned electron-donating polymerization initiator.

[0128] -Relationship between electron donor polymerization initiators and infrared absorbers- From the viewpoints of improving sensitivity and suppressing UV plate skipping, the image recording layer in the present disclosure contains the above-mentioned electron-donating polymerization initiator and infrared absorber, and the value of HOMO of the infrared absorber - HOMO of the above-mentioned electron-donating polymerization initiator is preferably 0.70 eV or less, and more preferably 0.70 eV to -0.10 eV. A negative value means that the HOMO of the electron-donating polymerization initiator is higher than the HOMO of the infrared absorber.

[0129] -Preferred embodiments of infrared absorber and electron-accepting polymerization initiator- In terms of improving sensitivity and preventing plate skipping, a preferred embodiment of the infrared absorber according to the present disclosure has an organic anion in which Δd is 16 or more, Δp is 16 to 32, and Δh is 60% or less of Δp, in Hansen solubility parameters. In terms of improving sensitivity and preventing plate skipping, a preferred embodiment of the electron-accepting polymerization initiator according to the present disclosure has an organic anion in which Δd is 16 or more, Δp is 16 to 32, and Δh is 60% or less of Δp, in Hansen solubility parameters.

[0130] Here, δd, δp, and δh in the Hansen solubility parameters in this disclosure are the dispersion term δd [unit: MPa 0.5 ] and polar term δp [unit: MPa 0.5 Here, the Hansen solubility parameter is the solubility parameter introduced by Hildebrand, which is divided into three components, the dispersion term δd, the polarity term δp, and the hydrogen bond term δh, and expressed in three-dimensional space. Details of Hansen solubility parameters are described in the literature "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)" written by Charles M. Hansen.

[0131] In the present disclosure, the δd, δp, and δh in the Hansen solubility parameters of the organic anions are values ​​estimated from their chemical structures using computer software "Hansen Solubility Parameters in Practice (HSPiP ver.4.1.07)."

[0132] Specific examples of organic anions having a Δd of 16 or more, a Δp of 16 to 32, and a Δh of 60% or less of Δp in the Hansen solubility parameters include, but are not limited to, the above-mentioned I-1 to I-15, I-17 to I-21, and I-23 to I-25, as well as the following. Among these, bis(halogen-substituted benzenesulfonyl)imide anions are more preferred, and the above-mentioned I-5 is particularly preferred.

[0133] [ka]

[0134] -particle- The image recording layer preferably contains particles from the viewpoints of UV printing durability and UV plate skipping suppression. The particles may be organic particles or inorganic particles. From the viewpoints of UV printing durability and UV plate skipping suppression, it is preferable that the particles contain organic particles, and it is more preferable that the particles contain polymer particles other than polymer A. As the inorganic particles, known inorganic particles can be used, and metal oxide particles such as silica particles and titania particles can be suitably used.

[0135] The polymer particles are preferably selected from the group consisting of thermoplastic polymer particles, thermoreactive polymer particles, polymer particles having a polymerizable group, microcapsules containing a hydrophobic compound, and microgels (crosslinked polymer particles). Among them, polymer particles or microgels having a polymerizable group are preferred. In a particularly preferred embodiment, the polymer particles contain at least one ethylenically unsaturated polymerizable group. The presence of such polymer particles provides the effect of increasing the printing durability of the exposed area and the on-press developability of the unexposed area. The polymer particles are preferably thermoplastic polymer particles.

[0136] Preferred examples of the thermoplastic polymer particles include those described in Research Disclosure No. 33303 published in January 1992, JP-A Nos. 9-123387, 9-131850, 9-171249, and 9-171250, and European Patent No. 931647. Specific examples of the polymer constituting the thermoplastic polymer particles include homopolymers or copolymers of monomers such as ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, acrylates or methacrylates having a polyalkylene structure, or mixtures thereof. Preferred examples include copolymers containing polystyrene, styrene and acrylonitrile, or polymethyl methacrylate. The average particle size of the thermoplastic polymer particles is preferably 0.01 μm to 3.0 μm.

[0137] The thermally reactive polymer particles include polymer particles having a thermally reactive group, which form a hydrophobic region by crosslinking through a thermal reaction and by the change in the functional group.

[0138] The thermally reactive group in the polymer particles having a thermally reactive group may be a functional group that undergoes any reaction as long as a chemical bond is formed, but is preferably a polymerizable group, and preferred examples thereof include ethylenically unsaturated groups that undergo radical polymerization reactions (e.g., acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, etc.), cationic polymerizable groups (e.g., vinyl groups, vinyloxy groups, epoxy groups, oxetanyl groups, etc.), isocyanato groups or blocked groups thereof that undergo addition reactions, epoxy groups, vinyloxy groups, and functional groups having active hydrogen atoms that are their reaction partners (e.g., amino groups, hydroxy groups, carboxy groups, etc.), carboxy groups and their reaction partners, hydroxy groups or amino groups that undergo condensation reactions, and acid anhydrides and their reaction partners, amino groups or hydroxy groups, that undergo ring-opening addition reactions.

[0139] As the microcapsule, for example, as described in JP-A-2001-277740 and JP-A-2001-277742, at least a part of the components of the image recording layer is encapsulated in the microcapsule. The components of the image recording layer can also be contained outside the microcapsule. In a preferred embodiment, the image recording layer containing the microcapsule has a hydrophobic component encapsulated in the microcapsule and a hydrophilic component contained outside the microcapsule.

[0140] The microgel (crosslinked polymer particle) can contain a part of the components of the image recording layer on at least one of the surface or the inside thereof. In particular, a reactive microgel having a radical polymerizable group on its surface is preferred from the viewpoints of the sensitivity of the resulting lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate.

[0141] The components of the image recording layer can be microencapsulated or microgelled by known methods.

[0142] From the viewpoint of the printing durability, stain resistance and storage stability of the resulting lithographic printing plate, the polymer particles are preferably those obtained by reacting a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate, with a compound having active hydrogen. The polyhydric phenol compound is preferably a compound having a plurality of benzene rings each having a phenolic hydroxy group. The compound having active hydrogen is preferably a polyol compound or a polyamine compound, more preferably a polyol compound, and even more preferably at least one compound selected from the group consisting of propylene glycol, glycerin, and trimethylolpropane. Preferred examples of resin particles obtained by reacting a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in the molecule and isophorone diisocyanate, with a compound having active hydrogen include the polymer particles described in paragraphs 0032 to 0095 of JP2012-206495A.

[0143] Furthermore, from the viewpoint of the printing durability and solvent resistance of the resulting lithographic printing plate, it is preferable that the polymer particles have a hydrophobic main chain and contain both i) a constituent unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a constituent unit having a pendant group that includes a hydrophilic polyalkylene oxide segment. A preferred example of the hydrophobic main chain is an acrylic resin chain. Preferred examples of the pendant cyano group include -[CH2CH(C≡N)]- or -[CH2C(CH3)(C≡N)]-. Furthermore, the structural unit having a pendant cyano group can be easily derived from an ethylenically unsaturated monomer, such as acrylonitrile or methacrylonitrile, or a combination thereof. The alkylene oxide in the hydrophilic polyalkylene oxide segment is preferably ethylene oxide or propylene oxide, and more preferably ethylene oxide. The number of repeating alkylene oxide structures in the hydrophilic polyalkylene oxide segment is preferably 10-100, more preferably 25-75, and even more preferably 40-50. Preferred examples of resin particles having a hydrophobic main chain and including both i) a constituent unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a constituent unit having a pendant group containing a hydrophilic polyalkylene oxide segment include those described in paragraphs 0039 to 0068 of JP2008-503365A.

[0144] In addition, from the viewpoints of UV printing durability and on-press developability, the polymer particles preferably have a hydrophilic group. The hydrophilic group is not particularly limited as long as it has a structure having hydrophilicity, and examples of the hydrophilic group include acid groups such as a carboxy group, a hydroxy group, an amino group, a cyano group, and a polyalkylene oxide structure. Among these, from the viewpoints of on-press developability, UV printing durability, and UV plate skipping suppression, a polyalkylene oxide structure is preferred, and a polyethylene oxide structure, a polypropylene oxide structure, or a polyethylene / propylene oxide structure is more preferred. From the viewpoint of on-press developability and suppression of development residue during on-press development, the polyalkylene oxide structure preferably has a polypropylene oxide structure, and more preferably has a polyethylene oxide structure or a polypropylene oxide structure. From the viewpoints of printing durability, ink receptivity, and on-press developability, the hydrophilic group preferably contains a structural unit having a cyano group or a group represented by the following formula Z, more preferably contains a structural unit represented by the following formula (AN) or a group represented by the following formula Z, and particularly preferably contains a group represented by the following formula Z. *-QWY formula Z In formula Z, Q represents a divalent linking group, W represents a divalent group having a hydrophilic structure or a divalent group having a hydrophobic structure, Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophobic structure, either W or Y has a hydrophilic structure, and * represents a bonding site with another structure.

[0145] [ka]

[0146] In formula (AN), R AN represents a hydrogen atom or a methyl group.

[0147] From the viewpoint of UV printing durability, the polymer contained in the polymer particles preferably contains a structural unit formed from a compound having a cyano group. The cyano group is preferably introduced as a structural unit containing a cyano group by using a compound (monomer) having a cyano group. Examples of the compound having a cyano group include acrylonitrile compounds, and (meth)acrylonitrile is preferred. The structural unit having a cyano group is preferably a structural unit formed from an acrylonitrile compound, and more preferably a structural unit formed from (meth)acrylonitrile, that is, a structural unit represented by the above formula (AN). When the above polymer includes a polymer having a structural unit having a cyano group, the content of the structural unit having a cyano group, preferably the structural unit represented by the above formula (AN), in the polymer having a structural unit having a cyano group is, from the viewpoint of UV printing durability, preferably 5% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and particularly preferably 30% by mass to 60% by mass, relative to the total mass of the polymer having a structural unit having a cyano group.

[0148] From the viewpoint of UV printing durability, the polymer particles preferably contain structural units formed from an aromatic vinyl compound. The aromatic vinyl compound may be any compound having a structure in which a vinyl group is bonded to an aromatic ring, and examples thereof include styrene compounds and vinylnaphthalene compounds, with styrene compounds being preferred, and styrene being more preferred. Examples of the styrene compound include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene, with styrene being preferred. Examples of the vinylnaphthalene compound include 1-vinylnaphthalene, methyl-1-vinylnaphthalene, β-methyl-1-vinylnaphthalene, 4-methyl-1-vinylnaphthalene, 4-methoxy-1-vinylnaphthalene, and the like, with 1-vinylnaphthalene being preferred.

[0149] Furthermore, preferred examples of the structural unit formed from an aromatic vinyl compound include a structural unit represented by the following formula Z1.

[0150] [ka]

[0151] In formula Z1, R Z1 and R Z2 each independently represents a hydrogen atom or an alkyl group, Ar represents an aromatic ring group, R Z3 represents a substituent, and nz represents an integer of 0 or more and not exceeding the maximum number of substituents of Ar. In formula Z1, R Z1 and R Z2 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 further preferably all are a hydrogen atom. In formula Z1, Ar is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring. In formula Z1, R Z3 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 further preferably a methyl group or a methoxy group. In formula Z1, R Z3 If there are multiple R Z3 may be the same or different from each other. In formula Z1, nz is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0152] The polymer particles may contain one type of structural unit formed by an aromatic vinyl compound, or may contain two or more types. In the above polymer particles, the content of the structural unit formed by the aromatic vinyl compound is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and particularly preferably 1% by mass to 10% by mass, relative to the total mass of the polymer particles, from the viewpoint of ink receptivity.

[0153] From the viewpoint of UV printing durability, the polymer particles preferably have a crosslinked structure, and more preferably contain a structural unit having a crosslinked structure. Because the polymer particles have a cross-linked structure, the hardness of the polymer particles themselves is improved, which in turn improves the strength of the image area. It is believed that this will further improve printing durability (UV printing durability) even when using ultraviolet-curing ink, which is more likely to deteriorate the plate than other inks. The crosslinked structure is not particularly limited, but is preferably a structural unit obtained by polymerizing a polyfunctional ethylenically unsaturated compound, or a structural unit in which one or more reactive groups form a covalent bond inside a particle. The number of functions of the polyfunctional ethylenically unsaturated compound is preferably 2 to 15, more preferably 3 to 10, even more preferably 4 to 10, and particularly preferably 5 to 10, from the viewpoints of UV printing durability and on-press developability. In other words, the structural unit having the crosslinked structure is preferably a bifunctional to pentafunctional branch unit from the viewpoints of UV printing durability and on-press developability. The n-functional branch unit refers to a branch unit having n molecular chains, in other words, a structural unit having an n-functional branch point (crosslinked structure). In addition, a crosslinked structure may be preferably formed by using a polyfunctional mercapto compound.

[0154] The ethylenically unsaturated group in the polyfunctional ethylenically unsaturated compound is not particularly limited, but examples thereof include a (meth)acryloxy group, a (meth)acrylamide group, an aromatic vinyl group, and a maleimide group. The polyfunctional ethylenically unsaturated compound is preferably a polyfunctional (meth)acrylate compound, a polyfunctional (meth)acrylamide compound, or a polyfunctional aromatic vinyl compound.

[0155] Examples of the polyfunctional (meth)acrylate compound include diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, tricyclodecane dimethylol diacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol triacrylate, dipentaerythritol hexaacrylate, and tris(β-hydroxyethyl)isocyanurate triacrylate. Examples of the polyfunctional (meth)acrylate compound include N,N'-methylenebisacrylamide, N-[tris(3-acrylamidopropoxymethyl)methyl]acrylamide, and the like. The polyfunctional aromatic vinyl compound may, for example, be divinylbenzene.

[0156] The number of carbon atoms in the branch unit is not particularly limited, but is preferably 8-100, and more preferably 8-70.

[0157] The polymer particles may contain one type of structural unit having a crosslinked structure, or may contain two or more types. In the above polymer particles, the content of the structural unit having a crosslinked structure is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and particularly preferably 1% by mass to 10% by mass, relative to the total mass of the polymer particles, from the viewpoints of UV printing durability and on-press developability.

[0158] Moreover, from the viewpoints of printing durability, ink receptivity, and on-press developability, the polymer particles preferably contain polymer particles having a group represented by the formula Z above.

[0159] Q in the above formula Z is preferably a divalent linking group having 1 to 20 carbon atoms, and more preferably a divalent linking group having 1 to 10 carbon atoms. Furthermore, Q in the above formula Z is preferably an alkylene group, an arylene group, an ester bond, an amide bond, or a group consisting of a combination of two or more of these, and more preferably a phenylene group, an ester bond, or an amide bond.

[0160] The divalent group having a hydrophilic structure in W of the above formula Z is a polyalkyleneoxy group or a polyalkyleneoxy group having -CH2CH2NR at one end. W It is preferable that R W represents a hydrogen atom or an alkyl group. The divalent group having a hydrophobic structure in W of the above formula Z is -R WA -, -OR WA -O-, -R W NR WA -NR W -, -OC(=O)-R WA -O- or -OC(=O)-R WA It is preferable that R is —O—. WA each independently represents a linear, branched, or cyclic alkylene group having 6 to 120 carbon atoms, a haloalkylene group having 6 to 120 carbon atoms, an arylene group having 6 to 120 carbon atoms, an alkylylene group having 7 to 120 carbon atoms (a divalent group obtained by removing one hydrogen atom from an alkylaryl group), or an aralkylene group having 7 to 120 carbon atoms.

[0161] The monovalent group having a hydrophilic structure in Y of the above formula Z is -OH, -C(=O)OH, a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the end, or a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the other end, and -CH2CH2N(R W It is preferable that the aryl group is a group having a bond with . The monovalent group having a hydrophobic structure for Y in the above formula Z is a linear, branched or cyclic alkyl group having 6 to 120 carbon atoms, a haloalkyl group having 6 to 120 carbon atoms, an aryl group having 6 to 120 carbon atoms, an alkaryl group (alkylaryl group) having 7 to 120 carbon atoms, an aralkyl group having 7 to 120 carbon atoms, -OR WB , -C(=O)OR WB , or -OC(=O)R WB It is preferable that R WB represents an alkyl group having 6 to 20 carbon atoms.

[0162] From the viewpoints of printing durability, ink receptivity, and on-press developability, it is more preferable that in the polymer particles having a group represented by the above formula Z, W is a divalent group having a hydrophilic structure, Q is a phenylene group, an ester bond, or an amide bond, W is a polyalkyleneoxy group, and Y is a polyalkyleneoxy group whose terminal is a hydrogen atom or an alkyl group.

[0163] In addition, from the viewpoints of printing durability, ink adhesion, UV plate skip suppression, and on-press developability, the polymer particles preferably contain polymer particles having a polymerizable group, and more preferably contain polymer particles having a polymerizable group on the particle surface. Furthermore, from the viewpoint of printing durability, the polymer particles preferably contain polymer particles having a hydrophilic group and a polymerizable group. The polymerizable group may be a cationically polymerizable group or a radically polymerizable group, but from the viewpoint of reactivity, it is preferably a radically polymerizable group. The polymerizable group is not particularly limited as long as it is a polymerizable group, but from the viewpoint of reactivity, an ethylenically unsaturated group is preferred, a vinylphenyl group (styryl group), a (meth)acryloxy group, or a (meth)acrylamide group is more preferred, and a (meth)acryloxy group is particularly preferred. The polymer in the polymer particles having a polymerizable group preferably has a structural unit having a polymerizable group. Furthermore, polymerizable groups may be introduced onto the surfaces of the polymer particles by a polymer reaction.

[0164] In addition, from the viewpoints of printing durability, ink adhesion, UV plate skip suppression, on-press developability, and suppression of development residue during on-press development, the polymer particles preferably contain a resin having a urea bond, more preferably contain a resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water, and particularly preferably contain a resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water and having a polyethylene oxide structure and a polypropylene oxide structure as the polyoxyalkylene structure. In addition, the particles containing the resin having a urea bond are preferably microgels.

[0165] [ka]

[0166] In formula (Iso), n represents an integer of 0 to 10.

[0167] An example of the reaction between the isocyanate compound represented by the above formula (Iso) and water is the reaction shown below. Note that the following example is an example in which n=0 and the 4,4-isomer is used. As shown below, when the isocyanate compound represented by the above formula (Iso) is reacted with water, a part of the isocyanate group is hydrolyzed by the water to generate an amino group, and the generated amino group reacts with the isocyanate group to generate a urea bond, forming a dimer. The following reaction is repeated to form a resin having a urea bond. In addition, in the reaction described below, by adding a compound (a compound having active hydrogen) that is reactive with an isocyanate group, such as an alcohol compound or an amine compound, it is also possible to introduce the structure of an alcohol compound, an amine compound, or the like into a resin having a urea bond. Preferred examples of the compound having active hydrogen include those described above in relation to the microgel.

[0168] [ka]

[0169] The resin having a urea bond preferably has an ethylenically unsaturated group, and more preferably has a group represented by the following formula (PETA).

[0170] [ka]

[0171] In formula (PETA), the wavy line portion represents the bonding position to other structures.

[0172] The average particle size of the above particles is preferably 0.01 μm to 3.0 μm, more preferably 0.03 μm to 2.0 μm, and even more preferably 0.10 μm to 1.0 μm. Within this range, good resolution and stability over time can be obtained. The average primary particle size of the above particles in this disclosure is measured by a light scattering method, or by taking an electron microscope photograph of the particles, measuring the particle sizes of 5,000 particles in total on the photograph, and calculating the average value. Note that for non-spherical particles, the particle size is the particle size value of a spherical particle having the same particle area as the particle area on the photograph. In addition, the average particle size in this disclosure is taken to be the volume average particle size unless otherwise specified.

[0173] The image recording layer may contain one type of particles, particularly polymer particles, or may contain two or more types. Furthermore, from the viewpoints of developability, UV printing durability, and UV plate skip suppression, the content of particles, particularly polymer particles, in the image recording layer is preferably 5% by mass to 90% by mass, more preferably 10% by mass to 90% by mass, even more preferably 20% by mass to 90% by mass, and particularly preferably 50% by mass to 90% by mass, relative to the total mass of the image recording layer. Furthermore, from the viewpoints of developability, UV printing durability, and UV plate skip suppression, the content of the polymer particles in the image recording layer is preferably 20% by mass to 100% by mass, more preferably 35% by mass to 100% by mass, even more preferably 50% by mass to 100% by mass, and particularly preferably 80% by mass to 100% by mass, relative to the total mass of the components of the image recording layer having a molecular weight of 3,000 or more.

[0174] -Binder polymer- The image recording layer may contain a binder polymer other than polymer A. However, from the viewpoints of on-press developability, UV printing durability, and UV plate skipping suppression, it is preferable that the image recording layer does not contain a binder polymer. The binder polymer is a polymer other than the polymer particles, that is, a binder polymer not in particle form. The binder polymer is preferably a (meth)acrylic resin, a polyvinyl acetal resin, or a polyurethane resin.

[0175] Among them, the binder polymer may suitably be a known binder polymer used in the image recording layer of a lithographic printing plate precursor. As an example, a binder polymer used in an on-press development type lithographic printing plate precursor (hereinafter, also referred to as an on-press development binder polymer) will be described in detail. The binder polymer for on-press development is preferably a binder polymer having an alkylene oxide chain. The binder polymer having an alkylene oxide chain may have a poly(alkylene oxide) moiety in the main chain or in the side chain. In addition, the binder polymer may be a graft polymer having a poly(alkylene oxide) in the side chain, or a block copolymer of a block composed of a poly(alkylene oxide)-containing repeating unit and a block composed of a non-(alkylene oxide)-containing repeating unit. When the main chain has a poly(alkylene oxide) moiety, polyurethane resin is preferred. When the main chain has a poly(alkylene oxide) moiety in the side chain, examples of the polymer of the main chain include (meth)acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, polystyrene resin, novolac type phenolic resin, polyester resin, synthetic rubber, and natural rubber, and (meth)acrylic resin is particularly preferred.

[0176] Another preferred example of the binder polymer is a polymer compound (hereinafter also referred to as a star-shaped polymer compound) having a 6- to 10-functional polyfunctional thiol core, a polymer chain bonded to the core by a sulfide bond, and the polymer chain having a polymerizable group. For example, the compound described in JP-A-2012-148555 can be preferably used as the star-shaped polymer compound.

[0177] Examples of star-shaped polymer compounds include those having a polymerizable group such as an ethylenically unsaturated bond in the main chain or side chain, preferably in the side chain, for improving the film strength in the image area as described in JP-A-2008-195018. The polymerizable group forms a crosslink between polymer molecules, accelerating curing. As the polymerizable group, an ethylenically unsaturated group such as a (meth)acrylic group, a vinyl group, an allyl group, or a styryl group, or an epoxy group, etc. are preferred, and a (meth)acrylic group, a vinyl group, or a styryl group is more preferred from the viewpoint of polymerization reactivity, and a (meth)acrylic group is particularly preferred. These groups can be introduced into a 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 an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be utilized. These groups may be used in combination.

[0178] The molecular weight of the binder polymer is preferably a weight average molecular weight (Mw) of 2,000 or more, more preferably 5,000 or more, and further preferably 10,000 to 300,000, as calculated as polystyrene by the GPC method.

[0179] If necessary, a hydrophilic polymer such as polyacrylic acid or polyvinyl alcohol described in JP-A-2008-195018 can be used in combination. Also, a lipophilic polymer and a hydrophilic polymer can be used in combination. Among these, from the viewpoint of on-machine developability, the image recording layer preferably contains polyvinyl acetal. Suitable examples of polyvinyl acetal include polyvinyl butyral.

[0180] Polyvinyl acetal is a resin obtained by acetalizing the hydroxyl groups of polyvinyl alcohol with an aldehyde. In particular, polyvinyl butyral obtained by acetalizing (that is, butyralizing) the hydroxyl groups of polyvinyl alcohol with butylaldehyde is preferred. The polyvinyl acetal preferably contains a structural unit represented by the following (a) obtained by acetalizing the hydroxyl group of polyvinyl alcohol with an aldehyde.

[0181] [ka]

[0182] Here, R represents the residue of the aldehyde used in the acetalization. Examples of R include a hydrogen atom, an alkyl group, and an ethylenically unsaturated group described below.

[0183] The content of the structural unit represented by (a) (also referred to as the amount of ethylene groups in the main chain contained in the structural unit represented by (a) above, and also referred to as the degree of acetalization) is preferably 50 mol% to 90 mol%, more preferably 55 mol% to 85 mol%, and even more preferably 55 mol% to 80 mol%, relative to all structural units of the polyvinyl acetal (total amount of ethylene groups in the main chain). The degree of acetalization is a molar fraction calculated by dividing the amount of ethylene groups to which acetal groups are bonded (the amount of ethylene groups in the main chain contained in the structural unit represented by (a) above) by the total amount of ethylene groups in the main chain, expressed as a percentage. The same applies to the content of each structural unit of the polyvinyl acetal described below.

[0184] From the viewpoint of improving printing durability, the polyvinyl acetal preferably has an ethylenically unsaturated group. Here, the ethylenically unsaturated group contained in the polyvinyl acetal is not particularly limited, and from the viewpoints of reactivity, on-press developability, and printing durability, it is more preferably at least one group selected from the group consisting of a vinylphenyl group (styryl group), a vinyl ester group, a vinyl ether group, an allyl group, a (meth)acryloxy group, and a (meth)acrylamide group, and a vinyl group, an allyl group, a (meth)acryloxy group, etc. are preferred.

[0185] From the viewpoint of improving printing durability, the polyvinyl acetal preferably contains a structural unit having an ethylenically unsaturated group. The structural unit having an ethylenically unsaturated group may be the above-mentioned structural unit having an acetal ring, or may be a structural unit other than the structural unit having an acetal ring. Among them, from the viewpoint of increasing the crosslink density during exposure, the polyvinyl acetal is preferably a compound having an ethylenically unsaturated group introduced into the acetal ring, i.e., in the constitutional unit represented by (a) above, it is preferable that R has an ethylenically unsaturated group.

[0186] When the structural unit having an ethylenically unsaturated group is a structural unit other than a structural unit having an acetal ring, it may be, for example, a structural unit having an acrylate group, specifically, a structural unit represented by the following (d).

[0187] [ka]

[0188] When the structural unit having an ethylenically unsaturated group is a structural unit other than a structural unit having an acetal ring, the content of this structural unit (also referred to as the amount of acrylate groups) is preferably 1 mol% to 15 mol%, and more preferably 1 mol% to 10 mol%, based on the total structural units of the polyvinyl acetal.

[0189] The polyvinyl acetal preferably further contains a structural unit having a hydroxy group from the viewpoint of on-machine developability, etc. In other words, the polyvinyl acetal preferably contains a structural unit derived from vinyl alcohol. An example of a structural unit having a hydroxy group is the structural unit represented by the following (b).

[0190] [ka]

[0191] From the viewpoint of on-machine developability, the content of the structural unit represented by (b) (also referred to as the amount of hydroxyl groups) is preferably 5 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 20 mol% to 40 mol%, based on the total structural units of the polyvinyl acetal.

[0192] The polyvinyl acetal may further contain other structural units. Examples of other structural units include structural units having an acetyl group, specifically, the structural unit represented by the following (c).

[0193] [ka]

[0194] The content of the structural unit represented by (c) (also referred to as the amount of acetyl groups) is preferably 0.5 mol % to 10 mol %, more preferably 0.5 mol % to 8 mol %, and even more preferably 1 mol % to 3 mol %, based on all structural units of the polyvinyl acetal.

[0195] Here, the degree of acetalization, the amount of acrylate groups, the amount of hydroxyl groups, and the amount of acetyl groups can be determined as follows. That is, 1 The molar content is calculated from the proton peak area ratio of the methyl or methylene moiety of the acetal, the methyl moiety of the acrylate group, the hydroxyl group, and the methyl moiety of the acetyl group by H NMR measurement.

[0196] The weight average molecular weight of the polyvinyl acetal is preferably 18,000 to 150,000.

[0197] The solubility parameter (also called SP value) of the above polyvinyl acetal is 17.5MPa. 1 / 2 ~20.0MPa 1 / 2 It is preferable that the pressure is 18.0 MPa. 1 / 2 ~19.5MPa 1 / 2 It is more preferable that: Here, the "solubility parameter (unit: (MPa) 1 / 2 ) shall use Hansen solubility parameters. The Hansen solubility parameter is a solubility parameter introduced by Hildebrand, which is divided into three components, the dispersion term δd, the polarity term δp, and the hydrogen bond term δh, and expressed in three-dimensional space. In this disclosure, the solubility parameter (hereinafter also referred to as the SP value) is expressed as δ (unit: (MPa) 1 / 2 ) and the value calculated using the following formula is used. δ(MPa) 1 / 2 =(δd2 +δp 2 +δh 2 ) 1 / 2 The dispersion term δd, polar term δp, and hydrogen bond term δh have been extensively studied by Hansen and his successors, and are described in detail in Polymer Handbook (fourth edition), VII-698 to 711. Details of the Hansen solubility parameters are described in the book "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)" by Charles M. Hansen. In the present disclosure, the Hansen solubility parameter of a partial structure of a compound may be a value estimated from the chemical structure by using computer software "Hansen Solubility Parameters in Practice (HSPiP ver.4.1.07)". In addition, in the present disclosure, when a compound is a polymer of an addition polymerization type, polycondensation type, or the like, the SP value is expressed as a total amount obtained by multiplying the SP value of each monomer unit by the molar fraction, and when a compound is a low molecular weight compound having no monomer units, the SP value is the SP value of the entire compound. In the present disclosure, the SP value of a polymer may be calculated from the molecular structure of the polymer by the Hoy method described in Polymer Handbook (fourth edition).

[0198] Specific examples of the polyvinyl acetal [P-1 to P-3] are given below, but the polyvinyl acetal used in the present disclosure is not limited to these. In the following structure, "l" is 50 mol% to 90 mol%, "m" is 0.5 mol% to 10 mass%, "n" is 5 mol% to 50 mol%, and "o" is 1 mol% to 15 mol%.

[0199] [ka]

[0200] As the polyvinyl acetal, commercially available products can be used. Commercially available polyvinyl acetal products include the S-LEC series from Sekisui Chemical Co., Ltd. (specifically, S-LEC BX-L, BX-1, BX-5, BL-7Z, BM-1, BM-5, BH-6, BH-3, etc.).

[0201] The image recording layer in the present disclosure preferably contains a resin having a fluorine atom, more preferably contains a fluorohydrocarbon group-containing copolymer, and particularly preferably contains a fluoroaliphatic hydrocarbon group-containing copolymer. By using a resin having a fluorine atom, in particular a copolymer containing a fluorohydrocarbon group, it is possible to suppress abnormal surface quality due to foaming during the formation of the image recording layer, improve the coating surface condition, and further improve the ink receptivity of the formed image recording layer. Furthermore, an image recording layer containing a fluorohydrocarbon group-containing copolymer provides high gradation, for example high sensitivity to laser light, and provides a lithographic printing plate with good resistance to fogging caused by scattered light, reflected light, etc. and excellent printing durability.

[0202] The above-mentioned fluorohydrocarbon group-containing copolymer preferably has a structural unit formed from a compound represented by any one of the following formulas (F1) to (F3), and more preferably has a structural unit formed from a compound represented by the following formula (F2) or formula (F3).

[0203] [ka]

[0204] In formulas (F1) to (F3), R F1 each independently represents a hydrogen atom or a methyl group; L F represents a single bond or a divalent linking group, Cf represents a linear or branched hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms of the hydrocarbon group are substituted with fluorine atoms, R F2 represents a hydrogen atom or a fluorine atom, XF each independently represents an oxygen atom, a sulfur atom, or -N(R F3 )-, w1 to w3 each independently represent an integer of 0 to 9, w4 represents an integer of 1 to 10, w5 represents an integer of 0 to 2, R F3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0205] L in formula (F1) F is preferably a single bond, an alkylene group having 1 to 20 carbon atoms, or a divalent arylene group having 6 to 20 carbon atoms, more preferably a single bond or a divalent arylene group having 6 to 20 carbon atoms, and particularly preferably a single bond. Cf in formula (F1) is preferably an aromatic hydrocarbon group having 6 to 10 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms, more preferably a phenyl group in which some or all of the hydrogen atoms have been substituted with fluorine atoms, and particularly preferably a perfluorophenyl group. X in formula (F2) and formula (F3) F Each independently represents an oxygen atom or -N(R F3 )-, and more preferably an oxygen atom. R in formula (F2) F2 is preferably a fluorine atom. In formula (F2), w1 is preferably an integer of 0 to 2, more preferably 1 or 2, and particularly preferably 2. In formula (F2), w2 is preferably an integer of 0 to 4, and more preferably 0. In formula (F2), w3 is preferably 0 or 1, and more preferably 0. In formula (F2), w4 is preferably an integer of 2 to 10, more preferably an integer of 4 to 8, and particularly preferably an integer of 4 to 6. In formula (F3), w5 is preferably 0 or 1, and more preferably 0. R in formula (F3) F3 is preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and more preferably a hydrogen atom or a methyl group.

[0206] Specific examples of the fluorine atom-containing monomer used in the fluorine atom-containing resin are shown below, but the present invention is not limited thereto.

[0207] [ka]

[0208] [ka]

[0209] [ka]

[0210] [ka]

[0211] [ka]

[0212] [ka]

[0213] [ka]

[0214] [ka]

[0215] [ka]

[0216] From the viewpoints of on-press developability, coatability, and on-press development residue suppression, the above-mentioned fluorohydrocarbon group-containing copolymer preferably contains a structural unit having a polyalkylene oxide structure, and more preferably contains a structural unit formed from a compound represented by any one of the above formulas (F1) and (F2), and a structural unit having a polyalkylene oxide structure. It is preferable that the above-mentioned fluorohydrocarbon group-containing copolymer further has, in addition to the structural units formed from the compounds represented by either of the above-mentioned formulas (F1) and (F2), a structural unit formed from at least one compound selected from the group consisting of poly(oxyalkylene)acrylates and poly(oxyalkylene)methacrylates.

[0217] The polyoxyalkylene group in the poly(oxyalkylene) acrylate and poly(oxyalkylene) methacrylate is -(OR F3 ) x - can be expressed as R F3 represents an alkyl group, and x represents an integer of 2 or more. F3 is preferably a linear or branched alkylene group having 2 to 4 carbon atoms. The linear or branched alkylene group having 2 to 4 carbon atoms is preferably -CH2CH2-, -CH2CH2CH2-, -CH(CH3)CH2-, or -CH(CH3)CH(CH3)-. x is preferably an integer of 2 to 100. In the polyoxyalkylene group, x "OR F3 " may be the same or different. In other words, the polyoxyalkylene group may have two or more "OR F3 " may be bonded regularly or irregularly. For example, the polyoxyalkylene group may be a group in which linear or branched oxypropylene units and oxyethylene units are bonded regularly or irregularly. More specifically, the polyoxyalkylene group may be a group in which blocks of linear or branched oxypropylene units and blocks of oxyethylene units are bonded. The polyoxyalkylene group may contain one or more linking groups (for example, -CONH-Ph-NHCO-, -S-, etc., where Ph represents a phenylene group). The molecular weight of the polyoxyalkylene group is preferably 250 to 3,000.

[0218] As the poly(oxyalkylene)acrylate and poly(oxyalkylene)methacrylate, commercially available products or synthetic products may be used. The above poly(oxyalkylene) acrylates and poly(oxyalkylene) methacrylates can be synthesized, for example, by reacting a hydroxypoly(oxyalkylene) compound with acrylic acid, methacrylic acid, acrylic chloride, methacrylic chloride, acrylic anhydride, or the like by a known method. As the hydroxypoly(oxyalkylene) compound, commercially available products may be used, such as ADEKA PLURONIC (registered trademark) manufactured by ADEKA CORPORATION, ADEKA POLYETHER (registered trademark) manufactured by ADEKA CORPORATION, Carbowax (registered trademark) manufactured by Union Carbide Corporation, Triton (registered trademark) manufactured by The Dow Chemical Company, and PEG (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. As the poly(oxyalkylene) acrylate and poly(oxyalkylene) methacrylate, poly(oxyalkylene) diacrylate and the like synthesized by a known method may be used.

[0219] In the image recording layer used in the present disclosure, the binder polymer may be used alone or in combination of two or more kinds. The binder polymer can be contained in any amount in the image recording layer, but from the viewpoints of on-press developability, UV printing durability, and UV plate skip suppression, it is preferable that the image recording layer does not contain the binder polymer or the content of the binder polymer is more than 0 mass% and 20 mass% or less, relative to the total mass of the image recording layer, it is more preferable that the image recording layer does not contain the binder polymer or the content of the binder polymer is more than 0 mass% and 10 mass% or less, relative to the total mass of the image recording layer, it is even more preferable that the image recording layer does not contain the binder polymer or the content of the binder polymer is more than 0 mass% and 5 mass% or less, relative to the total mass of the image recording layer, it is particularly preferable that the image recording layer does not contain the binder polymer or the content of the binder polymer is more than 0 mass% and 2 mass% or less, relative to the total mass of the image recording layer, and it is most preferable that the image recording layer does not contain the binder polymer.

[0220] -Color former- The image recording layer preferably contains a color former, more preferably an acid color former, and the color former preferably contains a leuco compound. The term "color former" as used in the present disclosure means a compound that has the property of developing or decoloring in response to a stimulus such as light or acid, thereby changing the color of the image recording layer, and the term "acid color former" means a compound that has the property of developing or decoloring in response to heating while accepting an electron-accepting compound (e.g., a proton such as an acid), thereby changing the color of the image recording layer. As the acid color former, in particular, a colorless compound having a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, or the like, which quickly opens or cleaves the partial skeleton when it comes into contact with an electron-accepting compound, is preferred.

[0221] Examples of such acid color formers include 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (also called "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-methylphenyl)phthalide, and 3-(4-dimethylaminophenyl)-3-(1,2-dimethylindol-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-bis(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,

[0222] 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-methylin phthalides such as 3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-diethylaminophenyl)phthalide, 3-[1,1-di(1-ethyl-2-methylindol-3-yl)ethylene-2-yl]-3-(4-N-ethyl-N-phenylaminophenyl)phthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)phthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl)phthalide, and 3-(2-methyl-4-diethylaminophenyl)-3-(1-n-octyl-2-methylindol-3-yl)phthalide;

[0223] 4,4-Bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoauramine, rhodamine-B-anilinolactam, rhodamine-(4-nitroanilino)lactam, rhodamine-B-(4-chloroanilino)lactam, 3,7-bis(diethylamino)-10-benzoylphenoxazine, benzoylleuco methylene blue, 4-nitrobenzoyl methylene blue,

[0224] 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,

[0225] 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-n-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-ethyl N-butyl-N-methylamino-6-methyl-7-anilinofluoran, 3-N-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-N-hexyl-N-methylamino amino-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-Nn-butylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-Nn-hexylamino-6-methyl-7-anilinofluoran, 3-N-cyclohexyl-Nn-octylamino-6-methyl-7-anilinofluoran,

[0226] 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-methylamino-6-methyl-7-anilinofluoran, 3-N-(3'-ethoxypropyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(3'-ethoxypropyl)-N-ethylamino-6-methyl-7-anilinofluoran, 3-N-(2'-tetrahydrofurfuryl)- 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, fluorans such as 3-di-n-butylamino-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-[4'-(4-phenylaminophenyl)aminophenyl]amino-6-methyl-7-chlorofluoran, and 3-[4'-(dimethylaminophenyl)]amino-5,7-dimethylfluoran;

[0227] 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 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3,3-bis(1-n-octyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-octyl-2-methylindol-3-yl)-4 or 7-azaphthalide, 3-( 2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-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, 3-(2-butoxy-4-diethylaminophenyl)-3-(1-ethyl-2-phenylindol-3 -yl)-4 or 7-azaphthalide 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran-3,6-bis(dimethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3,6-bis(diethylamino)fluorene-9-spiro-3'-(6'-dimethylamino)phthalide and other phthalides;

[0228] Other examples include 2'-anilino-6'-(N-ethyl-N-isopentyl)amino-3'-methylspiro[isobenzofuran-1(3H),9'-(9H)xanthene-3-one, 2'-anilino-6'-(N-ethyl-N-(4-methylphenyl))amino-3'-methylspiro[isobenzofuran-1(3H),9'-(9H)xanthene]-3-one, 3'-N,N-dibenzylamino-6'-N,N-diethylaminospiro[isobenzofuran-1(3H),9'-(9H)xanthene]-3-one, and 2'-(N-methyl-N-phenyl)amino-6'-(N-ethyl-N-(4-methylphenyl))aminospiro[isobenzofuran-1(3H),9'-(9H)xanthene]-3-one.

[0229] Among these, from the viewpoint of color development, the color former used in the present disclosure is preferably at least one compound selected from the group consisting of spiropyran compounds, spirooxazine compounds, spirolactone compounds, and spirolactam compounds. From the viewpoint of visibility, the hue of the dye after color development is preferably green, blue or black.

[0230] In addition, the acid color former is preferably a leuco dye from the viewpoints of color development and visibility of exposed areas. The leuco dye is not particularly limited as long as it has a leuco structure, but it preferably has a spiro structure, and more preferably has a spirolactone ring structure. From the viewpoints of color development and visibility of exposed areas, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having the above-mentioned phthalide structure or fluoran structure is preferably a compound represented by any one of the following formulas (Le-1) to (Le-3), and more preferably a compound represented by the following formula (Le-2).

[0231] [ka]

[0232] In formulae (Le-1) to (Le-3), ERG each independently represents an electron donating group, X1 to X4 each independently represent a hydrogen atom, a halogen atom or a dialkylanilino group, X5 to X 10 each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group; Y1 and Y2 each independently represent C or N; when Y1 is N, X1 is not present; and when Y2 is N, X4 is not present; Ra1 represents a hydrogen atom, an alkyl group, or an alkoxy group; and Rb1 to Rb4 each independently represent a hydrogen atom, an alkyl group, or an aryl group.

[0233] The electron-donating group in ERG of formulae (Le-1) to (Le-3) is preferably an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, an alkoxy group, an aryloxy group, or an alkyl group, more preferably an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, an alkoxy group, or an aryloxy group, still more preferably an arylamino group, a monoalkylmonoarylamino group, or a diarylamino group, and particularly preferably an arylamino group or a monoalkylmonoarylamino group. In the formulae (Le-1) to (Le-3), X1 to X4 each independently represent preferably a hydrogen atom or a chlorine atom, and more preferably a hydrogen atom, from the viewpoints of color development and visibility of exposed areas. X5 to X in formula (Le-2) or formula (Le-3) 10are each independently, from the viewpoints of color development and visibility of the exposed area, preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, or a cyano group, more preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group, even more preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and particularly preferably a hydrogen atom. In the formulae (Le-1) to (Le-3), from the viewpoints of color development and visibility of exposed areas, at least one of Y1 and Y2 is preferably C, and it is more preferable that both of Y1 and Y2 are C. From the viewpoints of color development and visibility of exposed areas, Ra1 in formulae (Le-1) to (Le-3) is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group. In formulae (Le-1) to (Le-3), Rb1 to Rb4 each independently represent, from the viewpoints of color development and visibility of exposed areas, preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, and particularly preferably a methyl group.

[0234] From the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is more preferably a compound represented by any one of the following formulas (Le-4) to (Le-6), and even more preferably a compound represented by the following formula (Le-5).

[0235] [ka]

[0236] In formulae (Le-4) to (Le-6), ERG each independently represents an electron donating group, X1 to X4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, Y1 and Y2 each independently represent C or N, and when Y1 is N, X1 does not exist, and when Y2 is N, X4 does not exist, Ra1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb1 to Rb4 each independently represent a hydrogen atom, an alkyl group, or an aryl group.

[0237] In formulae (Le-4) to (Le-6), ERG, X1 to X4, Y1, Y2, Ra1, and Rb1 to Rb4 have the same meanings as ERG, X1 to X4, Y1, Y2, Ra1, and Rb1 to Rb4 in formulae (Le-1) to (Le-3), respectively, and preferred embodiments are also the same.

[0238] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is more preferably a compound represented by any one of the following formulas (Le-7) to (Le-9), and particularly preferably a compound represented by the following formula (Le-8).

[0239] [ka]

[0240] In formulae (Le-7) to (Le-9), X1 to X4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group; Y1 and Y2 each independently represent C or N; when Y1 is N, X1 does not exist; when Y2 is N, X4 does not exist; Ra1 to Ra4 each independently represent a hydrogen atom, an alkyl group, or an alkoxy group; Rb1 to Rb4 each independently represent a hydrogen atom, an alkyl group, or an aryl group; and Rc1 and Rc2 each independently represent an aryl group.

[0241] X1 to X4, Y1 and Y2 in formulae (Le-7) to (Le-9) have the same meanings as X1 to X4, Y1 and Y2 in formulae (Le-1) to (Le-3), and preferred embodiments are also the same. In formulae (Le-7) to (Le-9), Ra1 to Ra4 are each independently preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group, from the viewpoints of color development and visibility of the exposed area. In formulae (Le-7) to (Le-9), Rb1 to Rb4 each independently represent, from the viewpoints of color development and visibility of the exposed area, preferably a hydrogen atom, an alkyl group, or an aryl group substituted with an alkyl group or an alkoxy group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom or a methyl group. In formula (Le-8), Rc1 and Rc2 each independently represent, from the viewpoints of color development and visibility of exposed areas, preferably a phenyl group or an alkylphenyl group, and more preferably a phenyl group. In formula (Le-8), from the viewpoints of color development and visibility of exposed areas, it is preferable that X1 to X4 are hydrogen atoms, and Y1 and Y2 are C. Furthermore, in formula (Le-8), from the viewpoints of color development and visibility of the exposed area, it is preferable that Rb1 and Rb2 are each independently a hydrogen atom, an alkyl group, or an aryl group substituted with an alkyl group or an alkoxy group, and more preferably a hydrogen atom or an alkyl group.

[0242] The alkyl group in the formulae (Le-1) to (Le-9) may be linear, branched, or have a ring structure. In addition, the alkyl group in formulae (Le-1) to (Le-9) preferably has 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, further preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. The aryl group in formulae (Le-1) to (Le-9) preferably has 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms, and particularly preferably 6 to 8 carbon atoms.

[0243] In addition, each group such as a monovalent organic group, an alkyl group, an aryl group, a dialkylanilino group, an alkylamino group, and an alkoxy group in the formulae (Le-1) to (Le-9) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a cyano group. In addition, these substituents may be further substituted with these substituents.

[0244] Suitable leuco dyes having a phthalide structure or a fluoran structure include the following compounds, where Me represents a methyl group.

[0245] [ka]

[0246] [ka]

[0247] [ka]

[0248] [ka]

[0249] [ka]

[0250] Commercially available products can be used as acid colorants, including 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, and Vermilio. Examples of such dyes include n-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF, TH-107 (all manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green-118, Red-40, Red-8 (all manufactured by Yamamoto Chemical Industry Co., Ltd.), and crystal violet lactone (manufactured by Tokyo Kaseihin Kogyo Co., Ltd.). Among these commercially available products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63, GN-169, and crystal violet lactone are preferred because the films formed have good visible light absorptance.

[0251] Furthermore, examples of leuco dyes that can be suitably used include the following compounds.

[0252] [ka]

[0253] These color formers may be used alone or in combination of two or more kinds. The content of the color former is preferably from 0.5% by mass to 10% by mass, and more preferably from 1% by mass to 5% by mass, based on the total mass of the image recording layer.

[0254] - 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. The chain transfer agent is preferably a thiol compound, more preferably a thiol having 7 or more carbon atoms from the viewpoint of boiling point (difficulty of volatilization), and further preferably a compound having a mercapto group on an aromatic ring (aromatic thiol compound).The thiol compound is preferably a monofunctional thiol compound.

[0255] Specific examples of the chain transfer agent include the following compounds.

[0256] [ka]

[0257] [ka]

[0258] [ka]

[0259] [ka]

[0260] The chain transfer agent may be added alone or in combination of two or more kinds. The content of the chain transfer agent is preferably from 0.01% by mass to 50% by mass, more preferably from 0.05% by mass to 40% by mass, and even more preferably from 0.1% by mass to 30% by mass, based on the total mass of the image recording layer.

[0261] -Low molecular hydrophilic compounds- The image recording layer may contain a low molecular weight hydrophilic compound in order to improve on-press developability while suppressing deterioration of printing durability. The low molecular weight hydrophilic compound is preferably a compound having a molecular weight of less than 1,000, more preferably a compound having a molecular weight of less than 800, and even more preferably a compound having a molecular weight of less than 500. Examples of low molecular weight hydrophilic compounds include water-soluble organic compounds such as glycols and their ether or ester derivatives, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol; polyols, such as glycerin, pentaerythritol, and tris(2-hydroxyethyl)isocyanurate; organic amines and their salts, such as triethanolamine, diethanolamine, and monoethanolamine; organic sulfonic acids and their salts, such as alkylsulfonic acid, toluenesulfonic acid, and benzenesulfonic acid; organic sulfamic acids and their salts, such as alkylsulfamic acid; organic sulfuric acids and their salts, such as alkylsulfuric acid and alkyl ether sulfuric acid; organic phosphonic acids and their salts, such as phenylphosphonic acid; organic carboxylic acids and their salts, such as tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, and amino acids; and betaines.

[0262] As the low molecular weight hydrophilic compound, it is preferable to contain at least one selected from the group consisting of polyols, organic sulfates, organic sulfonates, and betaines.

[0263] Specific examples of organic sulfonates include alkyl sulfonates such as sodium n-butyl sulfonate, sodium n-hexyl sulfonate, sodium 2-ethylhexyl sulfonate, sodium cyclohexyl sulfonate, and sodium n-octyl sulfonate; alkyl sulfonates containing an ethylene oxide chain such as sodium 5,8,11-trioxapentadecane-1-sulfonate, sodium 5,8,11-trioxaheptadecane-1-sulfonate, sodium 13-ethyl-5,8,11-trioxaheptadecane-1-sulfonate, and sodium 5,8,11,14-tetraoxatetracosane-1-sulfonate. arylsulfonates such as sodium benzenesulfonate, sodium p-toluenesulfonate, sodium p-hydroxybenzenesulfonate, sodium p-styrenesulfonate, sodium isophthalate dimethyl-5-sulfonate, sodium 1-naphthylsulfonate, sodium 4-hydroxynaphthylsulfonate, disodium 1,5-naphthalenedisulfonate, and trisodium 1,3,6-naphthalenetrisulfonate; and the compounds described in paragraphs 0026 to 0031 of JP-A No. 2007-276454 and paragraphs 0020 to 0047 of JP-A No. 2009-154525. The salt may be a potassium salt or a lithium salt.

[0264] The organic sulfates include sulfates of alkyl, alkenyl, alkynyl, aryl, or heterocyclic monoether of polyethylene oxide. The number of ethylene oxide units is preferably 1 to 4, and the salt is preferably a sodium salt, a potassium salt, or a lithium salt. Specific examples include the compounds described in paragraphs 0034 to 0038 of JP-A-2007-276454.

[0265] As the betaines, compounds in which the number of carbon atoms in the hydrocarbon substituent on the nitrogen atom is 1 to 5 are preferable, and specific examples include trimethylammonium acetate, dimethylpropylammonium acetate, 3-hydroxy-4-trimethylammoniobutyrate, 4-(1-pyridinio)butyrate, 1-hydroxyethyl-1-imidazolioacetate, trimethylammonium methanesulfonate, dimethylpropylammonium methanesulfonate, 3-trimethylammonio-1-propanesulfonate, and 3-(1-pyridinio)-1-propanesulfonate.

[0266] Since the structure of the hydrophobic portion of a low molecular weight hydrophilic compound is small and it has almost no surfactant effect, the dampening water does not penetrate into the exposed area (image area) of the image recording layer and reduce the hydrophobicity or film strength of the image area, and the ink receptivity and printing durability of the image recording layer can be maintained at a good level.

[0267] The content of the low molecular weight hydrophilic compound is preferably 0.5% by mass to 20% by mass, more preferably 1% by mass to 15% by mass, and even more preferably 2% by mass to 10% by mass, based on the total mass of the image recording layer. Within this range, good on-press developability and printing durability can be obtained. The low molecular weight hydrophilic compound may be used alone or in combination of two or more kinds.

[0268] -Oil sensitizer- In order to improve ink receptivity, the image recording layer may contain an oil sensitizer such as a phosphonium compound, a nitrogen-containing low molecular weight compound, an ammonium group-containing polymer, etc. In particular, when an inorganic layer compound is contained in the protective layer, these compounds function as a surface coating agent for the inorganic layer compound, and can suppress a decrease in ink receptivity during printing caused by the inorganic layer compound. As the oil sensitizer, it is preferable to use a phosphonium compound, a nitrogen-containing low molecular weight compound, and an ammonium group-containing polymer in combination, and it is more preferable to use a phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer in combination.

[0269] Examples of the phosphonium compound include those 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(triphenylphosphonio)heptane=sulfate, and 1,9-bis(triphenylphosphonio)nonane=naphthalene-2,7-disulfonate.

[0270] Examples of the nitrogen-containing low molecular weight compound include amine salts and quaternary ammonium salts. Examples of the nitrogen-containing low molecular weight compound include imidazolinium salts, benzimidazolinium salts, pyridinium salts, and quinolinium salts. Among them, quaternary ammonium salts and pyridinium salts are preferred. Specific examples include tetramethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, dodecyltrimethylammonium p-toluenesulfonate, benzyltriethylammonium hexafluorophosphate, benzyldimethyloctylammonium hexafluorophosphate, benzyldimethyldodecylammonium hexafluorophosphate, and the compounds described in paragraphs 0021 to 0037 of JP-A-2008-284858 and paragraphs 0030 to 0057 of JP-A-2009-90645.

[0271] The ammonium group-containing polymer may have an ammonium group in its structure, and is preferably a polymer containing 5 mol % to 80 mol % of a (meth)acrylate having an ammonium group in a side chain as a copolymerization component. Specific examples include the polymers described in paragraphs 0089 to 0105 of JP-A-2009-208458.

[0272] The ammonium salt-containing polymer preferably has a reduced specific viscosity (unit: ml / g) value determined according to the measurement method described in JP 2009-208458 A in the range of 5 to 120, more preferably 10 to 110, and particularly preferably 15 to 100. When the reduced specific viscosity is converted into 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.

[0273] Specific examples of the ammonium group-containing polymer are shown below. (1) 2-(trimethylammonio)ethyl methacrylate = p-toluenesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 10 / 90, Mw 45,000) (2) 2-(trimethylammonio)ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20 / 80, Mw 60,000) (3) 2-(ethyldimethylammonio)ethyl methacrylate = p-toluenesulfonate / hexyl methacrylate copolymer (molar ratio 30 / 70, Mw 45,000) (4) 2-(trimethylammonio)ethyl methacrylate = hexafluorophosphate / 2-ethylhexyl methacrylate copolymer (molar ratio 20 / 80, Mw 60,000) (5) 2-(trimethylammonio)ethyl methacrylate = methyl sulfate / hexyl methacrylate copolymer (molar ratio 40 / 60, Mw 70,000) (6) 2-(butyldimethylammonio)ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 25 / 75, Mw 65,000) (7) 2-(butyldimethylammonio)ethyl acrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20 / 80, Mw 65,000) (8) 2-(butyldimethylammonio)ethyl methacrylate = 13-ethyl-5,8,11-trioxa-1-heptadecanesulfonate / 3,6-dioxaheptyl methacrylate copolymer (molar ratio 20 / 80, Mw 75,000) (9) 2-(butyldimethylammonio)ethyl methacrylate = hexafluorophosphate / 3,6-dioxaheptyl methacrylate / 2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer (molar ratio 15 / 80 / 5, Mw 65,000)

[0274] The oil sensitizer may be used alone or in combination of two or more kinds. The content of the oil sensitizer is preferably from 0.01% by mass to 30.0% by mass, more preferably from 0.1% by mass to 15.0% by mass, and even more preferably from 1% by mass to 10% by mass, based on the total mass of the image recording layer.

[0275] -Other ingredients- The image recording layer may contain other components such as surfactants, polymerization inhibitors, higher fatty acid derivatives, plasticizers, inorganic particles, inorganic layer compounds, etc. For details, see paragraphs 0114 to 0159 of JP2008-284817A.

[0276] - Formation of image recording layer - The image recording layer in the lithographic printing plate precursor according to the present disclosure can be formed, for example, as described in paragraphs

[0142] to

[0143] of JP2008-195018A, by dispersing or dissolving each of the necessary components described above in a known solvent to prepare a coating liquid, applying the coating liquid onto a support by a known method such as bar coater coating, and drying. As the solvent, a known solvent can be used.Specific examples of the solvent include water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3-methoxy-1-propanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, methyl lactate, and ethyl lactate. The solvent may be used alone or in combination of two or more kinds. The solid content concentration in the coating liquid is preferably about 1 to 50 mass %. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer, it is 0.3 g / m 2 ~3.0g / m 2 is preferred.

[0277] <Aluminum support> The aluminum support in the lithographic printing plate precursor according to the present disclosure can be appropriately selected from known aluminum supports for lithographic printing plate precursors. Hereinafter, the aluminum support may also be simply referred to as "support". The aluminum support is preferably an aluminum support having a hydrophilic surface (hereinafter, also referred to as "hydrophilic aluminum support").

[0043] From the viewpoint of preventing scratches and stains, the aluminum support in the lithographic printing plate precursor according to the present disclosure has a contact angle with water, as measured by a water drop method in the air, on the surface of the aluminum support on the image recording layer side, of preferably 110° or less, more preferably 90° or less, even more preferably 80° or less, even more preferably 50° or less, particularly preferably 30° or less, more particularly preferably 20° or less, and most preferably 10° or less.

[0278] In the present disclosure, the contact angle with water on the surface of the aluminum support on the side of the image recording layer is measured by the following method using a water drop method in the air. The lithographic printing plate precursor is immersed in a solvent capable of removing the image recording layer (e.g., the solvent used in the coating liquid for the image recording layer), and the image recording layer is scraped off with at least one of a sponge and cotton, thereby dissolving the image recording layer in the solvent to expose the surface of the aluminum support. The contact angle with water on the surface of the exposed aluminum support on the image recording layer side is measured as the contact angle of a water droplet on the surface at 25°C (after 0.2 seconds) using a fully automatic contact angle meter (e.g., DM-501 manufactured by Kyowa Interface Science Co., Ltd.) as a measuring device.

[0279] The aluminum support in the present disclosure is preferably an aluminum plate that has been subjected to a surface roughening treatment and anodization treatment by a known method. That is, the aluminum support in the present disclosure preferably has an aluminum plate and an anodized aluminum coating disposed on the aluminum plate.

[0280] An example of a preferred embodiment of the aluminum support used in the present disclosure (the aluminum support according to this example is also referred to as "support (1)") is shown below. That is, the support (1) has an aluminum plate and an anodized aluminum film disposed on the aluminum plate, the anodized film is located closer to the image recording layer than the aluminum plate, the anodized film has micropores extending in the depth direction from the surface on the image recording layer side, the average diameter of the micropores on the surface of the anodized film is more than 10 nm and not more than 100 nm, and the L of the surface of the anodized film on the image recording layer side is * a * b * Lightness L in color system * The value is between 70 and 100.

[0281] FIG. 1 is a schematic cross-sectional view of one embodiment of an aluminum support 12a. The aluminum support 12a has a laminated structure in which an aluminum plate 18 and an aluminum anodized film 20a (hereinafter also simply referred to as "anodized film 20a") are laminated in this order. The anodized film 20a in the aluminum support 12a is located closer to the image recording layer than the aluminum plate 18. In other words, the lithographic printing plate precursor according to the present disclosure preferably has at least an anodized film, an image recording layer, and a water-soluble resin layer, in this order, on an aluminum plate.

[0282] -Anodized film- A preferred embodiment of the anodic oxide coating 20a will now be described. The anodized film 20a is a film produced on the surface of the aluminum plate 18 by anodizing, and has extremely fine micropores 22a that are approximately perpendicular to the film surface and are uniformly distributed. The micropores 22a extend from the surface of the anodized film 20a on the image recording layer side (the surface of the anodized film 20a on the side opposite to the aluminum plate 18 side) along the thickness direction (toward the aluminum plate 18).

[0283] The average diameter (average opening diameter) of the micropores 22a in the anodized coating 20a at the surface of the anodized coating is preferably more than 10 nm and not more than 100 nm. In terms of the balance between printing durability, stain resistance, and image visibility, the average opening diameter is more preferably 15 nm to 60 nm, even more preferably 20 nm to 50 nm, and particularly preferably 25 nm to 40 nm. The diameter inside the pores may be wider or narrower than that at the surface layer. If the average diameter exceeds 10 nm, the printing durability and image visibility are further improved, and if the average diameter is 100 nm or less, the printing durability is further improved. The average diameter of the micropores 22a is calculated as the arithmetic mean value by observing N=4 images of the surface of the anodized film 20a using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, measuring the diameters of 50 micropores present in an area of ​​400 nm x 600 nm in the four images obtained. When the shape of the micropores 22a is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle having the same projected area as the projected area of ​​the opening.

[0284] The depth of the micropores 22a is not particularly limited, but is preferably from 10 nm to 3,000 nm, more preferably from 50 nm to 2,000 nm, and further preferably from 300 nm to 1,600 nm. The above depth is calculated by taking a photograph (150,000 times) of the cross section of the anodic oxide film 20a, measuring the depth of 25 or more micropores 22a, and averaging the measured value.

[0285] 1, the micropores 22a are substantially straight (cylindrical), but may be conical with a diameter decreasing in the depth direction (thickness direction). The shape of the bottom of the micropores 22a is not particularly limited, and may be curved (convex) or flat.

[0286] The L of the surface of the aluminum support 12a on the image recording layer side (the surface of the anodized film 20a on the image recording layer side) * a * b * Lightness L in color system* The value is preferably from 70 to 100. Among these, from the viewpoint of a better balance between printing durability and image visibility, a value from 75 to 100 is preferred, and a value from 75 to 90 is more preferred. Above lightness L * The measurement is carried out using a color difference meter Spectro Eye manufactured by X-Rite Corporation.

[0287] In the support (1), the micropores are preferably composed of large-diameter pores extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm, and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend from the communicating positions to a depth of 20 nm to 2,000 nm, and the large-diameter pores have an average diameter of 15 nm to 150 nm at the surface of the anodized film, and the small-diameter pores have an average diameter of 13 nm or less at the communicating positions (hereinafter, the support according to the above support is also referred to as "support (2)"). FIG. 2 is a schematic cross-sectional view of an aluminum support 12a according to another embodiment different from that shown in FIG. In FIG. 2, the aluminum support 12b includes an aluminum plate 18 and an anodized film 20b having micropores 22b each composed of a large diameter portion 24 and a small diameter portion . Micropores 22b in anodized film 20b are composed of large diameter pores 24 extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm (depth D: see Figure 2), and small diameter pores 26 that communicate with the bottom of large diameter pores 24 and extend from the communicating position to a depth of 20 nm to 2,000 nm. The large diameter hole portion 24 and the small diameter hole portion 26 will be described in detail below.

[0288] The average diameter of the large diameter pores 24 on the surface of the anodized film 20b is the same as the average diameter of the micropores 22a in the anodized film 20a on the surface of the anodized film, that is, more than 10 nm but not more than 100 nm, and the preferred range is also the same. The method for measuring the average diameter of the large diameter pores 24 on the surface of the anodized film 20b is the same as the method for measuring the average diameter of the micropores 22a in the anodized film 20a on the surface of the anodized film.

[0289] The bottoms of the large diameter holes 24 are located at a depth of 10 nm to 1,000 nm (hereinafter also referred to as depth D) from the surface of the anodized film. That is, the large diameter holes 24 are holes that extend from the surface of the anodized film to a position 10 nm to 1,000 nm in the depth direction (thickness direction). The depth is preferably 10 nm to 200 nm. The above depth is calculated by taking a photograph (150,000 times) of a cross section of the anodic oxide coating 20b, measuring the depth of 25 or more large diameter holes 24, and averaging the measured value.

[0290] The shape of the large diameter hole portion 24 is not particularly limited, and examples thereof include a substantially straight tube shape (substantially cylindrical shape) and a cone shape whose diameter decreases in the depth direction (thickness direction), with a substantially straight tube shape being preferred.

[0291] As shown in FIG. 2, the small diameter hole portion 26 is a hole portion that communicates with the bottom of the large diameter hole portion 24 and extends further in the depth direction (thickness direction) from the communicating position. The average diameter of the small diameter holes 26 at the communicating positions is preferably 13 nm or less. In particular, it is preferably 11 nm or less, and more preferably 10 nm or less. There is no particular lower limit, but it is often 5 nm or more.

[0292] The average diameter of the small pores 26 is obtained by observing the surface of the anodized film 20a with an FE-SEM at a magnification of 150,000 times, observing the diameters (diameters) of the micropores (small pores) present in the range of 400 nm × 600 nm in the four images obtained, and calculating the arithmetic average value. If the large pores are deep, the upper part of the anodized film 20b (the area where the large pores are located) may be cut (e.g., cut with argon gas) as necessary, and then the surface of the anodized film 20b may be observed with the FE-SEM to determine the average diameter of the small pores. If the shape of the small diameter hole 26 is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle having the same projected area as the projected area of ​​the opening.

[0293] The bottoms of the small diameter holes 26 are located at positions extending 20 nm to 2,000 nm in the depth direction from the positions where the small diameter holes 26 communicate with the large diameter holes 24. In other words, the small diameter holes 26 are holes extending in the depth direction (thickness direction) from the positions where the small diameter holes 26 communicate with the large diameter holes 24, and the depth of the small diameter holes 26 is 20 nm to 2,000 nm. The depth is preferably 500 nm to 2,000 nm. The above depth is calculated by taking a photograph (50,000 times) of the cross section of the anodic oxide coating 20b, measuring the depth of at least 25 small diameter holes, and averaging the measured value.

[0294] The shape of the small diameter hole portion 26 is not particularly limited, and examples thereof include a substantially straight tube shape (substantially cylindrical shape) and a cone shape whose diameter decreases in the depth direction, with a substantially straight tube shape being preferred.

[0295] -Method of manufacturing aluminum support- As a method for producing the aluminum support used in the present disclosure, for example, a production method in which the following steps are carried out in order is preferable. Surface roughening process: A process for roughening the surface of aluminum plates. Anodizing process: A process of anodizing a roughened aluminum plate. Pore ​​widening process: A process in which the aluminum plate having the anodized film obtained in the anodizing process is brought into contact with an acidic or alkaline aqueous solution to expand the diameter of the micropores in the anodized film. The procedure for each step is described in detail below.

[0296] [Surface roughening treatment process] The surface roughening step is a step of roughening the surface of the aluminum plate, including electrochemical roughening. This step is preferably carried out before the anodizing step described below, but may not be necessary if the surface of the aluminum plate already has a desired surface shape.

[0297] The surface roughening treatment may be performed by electrochemical surface roughening alone, or may be performed by combining electrochemical surface roughening treatment with mechanical surface roughening treatment and / or chemical surface roughening treatment. When mechanical graining and electrochemical graining are combined, it is preferable to carry out the electrochemical graining after the mechanical graining. The electrochemical graining treatment is preferably carried out in an aqueous solution mainly containing nitric acid or hydrochloric acid, using a direct current or an alternating current. The method for mechanically roughening the surface is not particularly limited, but may be, for example, the method described in JP-B-50-40047. The chemical roughening treatment is not particularly limited, and known methods can be used.

[0298] After the mechanical roughening treatment, the following chemical etching treatment is preferably carried out. The chemical etching treatment carried out after the mechanical graining treatment is carried out to smooth out the uneven edges of the surface of the aluminum plate, prevent the ink from catching during printing, improve the stain resistance of the printing plate, and remove any unwanted material such as abrasive particles remaining on the surface. Examples of chemical etching treatments include etching with an acid and etching with an alkali, and a method that is particularly excellent in terms of etching efficiency is a chemical etching treatment using an aqueous alkali solution (hereinafter, also referred to as "alkaline etching treatment").

[0299] The alkaline agent used in the alkaline aqueous solution is not particularly limited, but examples thereof include caustic soda, caustic potash, sodium metasilicate, sodium carbonate, sodium aluminate, and sodium gluconate. The alkaline aqueous solution may contain aluminum ions. The concentration of the alkaline agent in the alkaline aqueous solution is preferably 0.01% by mass or more, more preferably 3% by mass or more, and is preferably 30% by mass or less.

[0300] When the alkaline etching treatment is carried out, it is preferable to carry out a chemical etching treatment (hereinafter also referred to as a "desmutting treatment") using a low-temperature acidic aqueous solution in order to remove products produced by the alkaline etching treatment. The acid used in the acidic aqueous solution is not particularly limited, but examples thereof include sulfuric acid, nitric acid, and hydrochloric acid. The temperature of the acidic aqueous solution is preferably 20°C to 80°C.

[0301] As the surface roughening step, a method in which the treatments shown in embodiment A or embodiment B are carried out in the order shown below is preferred.

[0302] ~A mode~ (2) Chemical etching treatment using an alkaline aqueous solution (first alkaline etching treatment) (3) Chemical etching treatment using an acidic aqueous solution (first desmutting treatment) (4) Electrochemical roughening treatment using an aqueous solution mainly containing nitric acid (first electrochemical roughening treatment) (5) Chemical etching treatment using an alkaline aqueous solution (second alkaline etching treatment) (6) Chemical etching treatment using an acidic aqueous solution (second desmutting treatment) (7) Electrochemical roughening treatment in an aqueous solution mainly containing hydrochloric acid (second electrochemical roughening treatment) (8) Chemical etching treatment using an alkaline aqueous solution (third alkaline etching treatment) (9) Chemical etching treatment using an acidic aqueous solution (third desmutting treatment)

[0303] ~B mode~ (10) Chemical etching treatment using an alkaline aqueous solution (fourth alkaline etching treatment) (11) Chemical etching treatment using an acidic aqueous solution (fourth desmutting treatment) (12) Electrochemical roughening treatment using an aqueous solution mainly containing hydrochloric acid (third electrochemical roughening treatment) (13) Chemical etching treatment using an alkaline aqueous solution (fifth alkaline etching treatment) (14) Chemical etching treatment using an acidic aqueous solution (5th desmutting treatment)

[0304] Before the treatment (2) in the above embodiment A or before the treatment (10) in the above embodiment B, a mechanical graining treatment (1) may be carried out, if necessary.

[0305] The amount of aluminum plate dissolved in the first and fourth alkaline etching treatments was 0.5 g / m 2 ~30g / m 2 is preferred, and 1.0 g / m 2 ~20g / m 2 is more preferred.

[0306] The aqueous solution mainly containing nitric acid for use in the first electrochemical graining treatment in embodiment A includes an aqueous solution for use in electrochemical graining treatment using direct or alternating current, such as an aqueous solution obtained by adding aluminum nitrate, sodium nitrate, ammonium nitrate, or the like to a 1 to 100 g / L aqueous solution of nitric acid. The aqueous solution mainly containing hydrochloric acid used in the second electrochemical graining treatment in the embodiment A and the third electrochemical graining treatment in the embodiment B includes an aqueous solution used in an ordinary electrochemical graining treatment using direct or alternating current. For example, an aqueous solution obtained by adding 0 g / L to 30 g / L of sulfuric acid to an aqueous solution of hydrochloric acid of 1 g / L to 100 g / L may be included. Note that this solution may further include nitrate ions such as aluminum nitrate, sodium nitrate, and ammonium nitrate; or chloride ions such as aluminum chloride, sodium chloride, and ammonium chloride.

[0307] The AC power waveform for the electrochemical graining treatment may be a sine wave, a square wave, a trapezoidal wave, a triangular wave, etc. The frequency is preferably 0.1 Hz to 250 Hz. FIG. 3 is a graph showing an example of an alternating current waveform used in electrochemical surface roughening treatment. In FIG. 3, ta is the anode reaction time, tc is the cathode reaction time, tp is the time from 0 to the peak of the current, Ia is the current at the peak on the anode cycle side, Ic is the current at the peak on the cathode cycle side, AA is the current of the anode reaction of the aluminum plate, and CA is the current of the cathode reaction of the aluminum plate. In the trapezoidal wave, the time tp from 0 to the peak of the current is preferably 1 ms to 10 ms. The conditions of one cycle of the alternating current used for electrochemical surface roughening are preferably in the range of 1 to 20 for the ratio tc / ta of the anode reaction time ta of the aluminum plate to the cathode reaction time tc, 0.3 to 20 for the ratio Qc / Qa of the quantity of electricity when the aluminum plate is the anode to the quantity of electricity Qa when the aluminum plate is the anode, and 5 ms to 1,000 ms for the anode reaction time ta. The current density is 10 A / dm2 at the peak value of the trapezoidal wave for both the anode cycle side Ia and the cathode cycle side Ic. 2 ~200A / dm 2 The ratio Ic / Ia is preferably 0.3 to 20. The total amount of electricity involved in the anodic reaction of the aluminum plate at the time when the electrochemical graining is completed is preferably 25 C / dm 2 ~1,000C / dm 2 is preferred.

[0308] For electrochemical roughening using alternating current, the apparatus shown in FIG. 4 can be used. FIG. 4 is a side view showing an example of a radial cell in electrochemical surface roughening treatment using an alternating current. In Fig. 4, 50 is a main electrolytic cell, 51 is an AC power source, 52 is a radial drum roller, 53a and 53b are main electrodes, 54 is an electrolyte supply port, 55 is an electrolyte, 56 is a slit, 57 is an electrolyte passage, 58 is an auxiliary anode, 60 is an auxiliary anode cell, and W is an aluminum plate. In Fig. 4, arrow A1 indicates the electrolyte supply direction, and arrow A2 indicates the electrolyte discharge direction. When two or more electrolytic cells are used, the electrolysis conditions may be the same or different. The aluminum sheet W is wound around a radial drum roller 52 immersed in a main electrolytic cell 50, and is electrolyzed by main electrodes 53a and 53b connected to an AC power source 51 during transportation. An electrolyte 55 is supplied from an electrolyte supply port 54 through a slit 56 to an electrolyte passage 57 between the radial drum roller 52 and the main electrodes 53a and 53b. The aluminum sheet W treated in the main electrolytic cell 50 is then electrolyzed in an auxiliary anode cell 60. In this auxiliary anode cell 60, an auxiliary anode 58 is disposed opposite the aluminum sheet W, and the electrolyte 55 is supplied so as to flow through the space between the auxiliary anode 58 and the aluminum sheet W.

[0309] The amount of aluminum plate dissolved in the second alkaline etching treatment is set to 1.0 g / m2 in order to facilitate the production of a desired printing plate precursor. 2 More than 2.0 g / m is preferable. 2 ~10g / m 2 is more preferred.

[0310] The amount of dissolution of the aluminum plate in the third alkaline etching treatment and the fourth alkaline etching treatment is set to 0.01 g / m so that a predetermined printing plate precursor can be easily produced. 2 ~0.8g / m 2 is preferred, and 0.05 g / m 2 ~0.3g / m 2 is more preferred.

[0311] In the chemical etching treatments (first to fifth desmutting treatments) using an acidic aqueous solution, an acidic aqueous solution containing phosphoric acid, nitric acid, sulfuric acid, chromic acid, hydrochloric acid, or a mixed acid containing two or more of these acids is suitably used. The acid concentration of the acidic aqueous solution is preferably 0.5% by mass to 60% by mass.

[0312] [Anodizing process] The procedure for the anodizing treatment step is not particularly limited as long as the above-mentioned micropores can be obtained, and known methods can be used. In the anodizing process, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, etc. can be used as an electrolytic bath. For example, the concentration of sulfuric acid can be 100 g / L to 300 g / L. The conditions for the anodizing treatment are appropriately set depending on the electrolyte used. For example, the electrolyte temperature is 5°C to 70°C (preferably 10°C to 60°C), the current density is 0.5 A / dm 2 ~60A / dm 2 (Preferably 1A / dm 2 ~60A / dm 2 ), voltage 1V to 100V (preferably 5V to 50V), electrolysis time 1 second to 100 seconds (preferably 5 seconds to 60 seconds), and coating amount 0.1g / m 2 ~5g / m 2 (Preferably 0.2 g / m 2 ~3g / m 2 ) are mentioned.

[0313] [Pore widening treatment] The pore widening treatment is a treatment (pore diameter enlargement treatment) for enlarging the diameter (pore diameter) of the micropores present in the anodized film formed by the above-mentioned anodizing treatment process. The pore widening treatment can be carried out by contacting the aluminum plate obtained by the above-mentioned anodizing treatment step with an acid aqueous solution or an alkaline aqueous solution. The contacting method is not particularly limited, and examples thereof include a dipping method and a spraying method.

[0314] <Undercoat layer> The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (sometimes called an intermediate layer) between the image recording layer and the support. The undercoat layer strengthens the adhesion between the support and the image recording layer in the exposed area, and facilitates peeling of the image recording layer from the support in the unexposed area, thereby contributing to improving developability without impairing printing durability. In addition, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, thereby preventing the heat generated by exposure from diffusing to the support and reducing sensitivity.

[0315] The compound used in the undercoat layer may be a polymer having an adsorptive group and a hydrophilic group that can be adsorbed to the support surface. In order to improve adhesion with the image recording layer, a polymer having an adsorptive group and a hydrophilic group and further having a crosslinkable group is preferred. The compound used in the undercoat layer may be a low molecular weight compound or a polymer. The compound used in the undercoat layer may be a mixture of two or more kinds, if necessary.

[0316] When the compound used in the undercoat layer is a polymer, it is preferably a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group. The adsorptive group capable of being adsorbed to the surface of the support is preferably a phenolic hydroxy group, a carboxy group, -PO3H2, -OPO3H2, -CONHSO2-, -SO2NHSO2-, or -COCH2COCH3. The hydrophilic group is preferably a sulfo group or a salt thereof, or a salt of a carboxy group. The crosslinkable group is preferably an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, or an allyl group. The polymer may have a crosslinkable group introduced by salt formation between a polar substituent of the polymer and a compound having an ethylenically unsaturated bond and a substituent having an opposite charge to the polar substituent, or may further be copolymerized with a monomer other than the above-mentioned monomers, preferably a hydrophilic monomer.

[0317] Specifically, preferred examples include a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679 and a phosphorus compound having an ethylenic double bond reactive group described in JP-A-2-304441. Also preferred are low-molecular or high-molecular compounds having a crosslinkable group (preferably an ethylenic unsaturated bond group), a functional group that interacts with the support surface, and a hydrophilic group described in JP-A-2005-238816, JP-A-2005-125749, JP-A-2006-239867, and JP-A-2006-215263. More preferred examples include polymers having an adsorptive group, a hydrophilic group and a crosslinkable group capable of being adsorbed onto the surface of a support, as described in JP-A Nos. 2005-125749 and 2006-188038.

[0318] The content of the ethylenically unsaturated bond group in the polymer used in the undercoat layer is preferably from 0.1 mmol to 10.0 mmol, and more preferably from 0.2 mmol to 5.5 mmol, per 1 g of the polymer. The weight average molecular weight (Mw) of the polymer used in the undercoat layer is preferably 5,000 or more, and more preferably from 10,000 to 300,000.

[0319] [Hydrophilic compound] From the viewpoint of developability, the undercoat layer preferably contains a hydrophilic compound. The hydrophilic compound is not particularly limited, and any known hydrophilic compound used in an undercoat layer can be used. Preferred examples of the hydrophilic compound include phosphonic acids having an amino group such as carboxymethyl cellulose and dextrin, organic phosphonic acids, organic phosphoric acids, organic phosphinic acids, amino acids, and hydrochlorides of amines having a hydroxyl group. Preferred examples of the hydrophilic compound include compounds having an amino group or a functional group having polymerization-inhibiting ability and a group that interacts with the support surface (e.g., 1,4-diazabicyclo[2.2.2]octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, ethylenediaminetetraacetic acid (EDTA) or a salt thereof, hydroxyethylethylenediaminetriacetic acid or a salt thereof, dihydroxyethylethylenediaminediacetic acid or a salt thereof, hydroxyethyliminodiacetic acid or a salt thereof, etc.).

[0320] From the viewpoint of scratch and stain suppression, the hydrophilic compound preferably contains a hydroxycarboxylic acid or a salt thereof. From the viewpoint of scratch and stain suppression, the hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, is preferably contained in a layer on the aluminum support. The layer on the aluminum support is preferably a layer on the side on which an image recording layer is formed, and is preferably a layer in contact with the aluminum support. The layer on the aluminum support is preferably a subbing layer or an image recording layer as a layer in contact with the aluminum support. A layer other than the layer in contact with the aluminum support, such as a protective layer or an image recording layer, may contain a hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof. In the lithographic printing plate precursor according to the present disclosure, the image recording layer preferably contains a hydroxycarboxylic acid or a salt thereof from the viewpoint of scratch and stain suppression. In another preferred embodiment of the lithographic printing plate precursor according to the present disclosure, the surface of the aluminum support on the image recording layer side is surface-treated with a composition (e.g., an aqueous solution) containing at least a hydroxycarboxylic acid or a salt thereof. In the above embodiment, at least a portion of the treated hydroxycarboxylic acid or a salt thereof can be detected in a layer (e.g., an image recording layer or an undercoat layer) on the image recording layer side in contact with the aluminum support. By including a hydroxycarboxylic acid or a salt thereof in a layer on the image recording layer side that is in contact with the aluminum support, such as an undercoat layer, the surface of the aluminum support on the image recording layer side can be made hydrophilic, and the contact angle with water, as measured by a water drop method in the air, on the surface of the aluminum support on the image recording layer side can be easily made to be 110° or less, resulting in excellent scratch and stain prevention.

[0321] Hydroxycarboxylic acid is a general term for organic compounds that have one or more carboxy groups and one or more hydroxy groups in one molecule, and is also called hydroxy acid, oxy acid, oxycarboxylic acid, or alcohol acid (see Iwanami Dictionary of Physics and Chemistry, 5th Edition, published by Iwanami Shoten Co., Ltd. (1998)). The above hydroxycarboxylic acid or a salt thereof is preferably represented by the following formula (HC): R HC (OH)mhc (COOM HC ) nhc Formula (HC) In formula (HC), R HC represents an organic group with mhc+nhc valence, and M HC each independently represents a hydrogen atom, an alkali metal or an onium; mhc and nhc each independently represent an integer of 1 or more; when n is 2 or more, M may be the same or different.

[0322] In the formula (HC), the mhc+nhc valence organic group represented by R includes a mhc+nhc valence hydrocarbon group, etc. The hydrocarbon group may have a substituent and / or a linking group. Examples of the hydrocarbon group include mhc+nhc valence groups derived from aliphatic hydrocarbons, such as alkylene groups, alkanetriyl groups, alkanetetrayl groups, alkanpentyl groups, alkenylene groups, alkenetriyl groups, alkenetetrayl groups, alkenepentyl groups, alkynylene groups, alkyntriyl groups, alkyntetrayl groups, alkynpentyl groups, etc., and mhc+nhc valence groups derived from aromatic hydrocarbons, such as arylene groups, arenetriyl groups, arenetetrayl groups, arenepentyl groups, etc. Examples of the substituents other than the hydroxyl group and the carboxyl group include alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, aryl groups, etc. Specific examples of the substituent include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, a 2-norbornyl group, a methoxymethyl group, a methoxyethoxyethyl group, an allyloxymethyl group, a phenoxymethyl group, an acetyloxymethyl group, a benzoyloxymethyl group, and the like. Examples of the linking group include an alkyl group, a benzyl group, a phenethyl group, an α-methylbenzyl group, a 1-methyl-1-phenylethyl group, a p-methylbenzyl group, a cinnamyl group, an allyl group, a 1-propenylmethyl group, a 2-butenyl group, a 2-methylallyl group, a 2-methylpropenylmethyl group, a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a phenyl group, a biphenyl group, a naphthyl group, a tolyl group, a xylyl group, a mesityl group, a cumenyl group, a methoxyphenyl group, a ethoxyphenyl group, a phenoxyphenyl group, an acetoxyphenyl group, a benzoyloxyphenyl group, a methoxycarbonylphenyl group, an ethoxycarbonylphenyl group, a phenoxycarbonylphenyl group, etc. The linking group is composed of at least one atom selected from the group consisting of a hydrogen atom, a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, and a halogen atom, and the number of atoms is preferably 1 to 50.Specific examples include an alkylene group, a substituted alkylene group, an arylene group, and a substituted arylene group, and these divalent groups may have a structure in which a plurality of them are linked together via amide bonds, ether bonds, urethane bonds, urea bonds, or ester bonds.

[0323] M HC Examples of the alkali metal represented by the formula (I) include lithium, sodium, and potassium, with sodium being particularly preferred. Examples of the onium include ammonium, phosphonium, and sulfonium, with ammonium being particularly preferred. Also, M HC From the viewpoint of scratch and stain suppression, is preferably an alkali metal or an onium, and more preferably an alkali metal. The total number of mhc and nhc is preferably 3 or more, more preferably 3 to 8, and even more preferably 4 to 6.

[0324] The hydroxycarboxylic acid or salt thereof preferably has a molecular weight of 600 or less, more preferably 500 or less, and particularly preferably 300 or less. In addition, the molecular weight is preferably 76 or more. Specific examples of the hydroxycarboxylic acid constituting the above hydroxycarboxylic acid or the salt of the above hydroxycarboxylic acid include gluconic acid, glycolic acid, lactic acid, tartronic acid, hydroxybutyric acid (2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, etc.), malic acid, tartaric acid, citramalic acid, citric acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricineraidic acid, cerebroside acid, quinic acid, shikimic acid, monohydroxybenzoic acid derivatives (salicylic acid, creosinoic acid, etc.), and the like. Examples of the benzoic acid derivatives include benzoic acid (homosalicylic acid, hydroxy(methyl)benzoic acid), vanillic acid, syringic acid, etc.), dihydroxybenzoic acid derivatives (pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, orselliic acid, etc.), trihydroxybenzoic acid derivatives (gallic acid, etc.), phenylacetic acid derivatives (mandelic acid, benzilic acid, atrolactic acid, etc.), hydrocinnamic acid derivatives (mellitic acid, phloretic acid, coumaric acid, umbellic acid, caffeic acid, ferulic acid, sinapic acid, cerebronic acid, carminic acid, etc.).

[0325] Among these, from the viewpoint of scratch and stain suppression, the hydroxycarboxylic acid or the hydroxycarboxylic acid constituting the salt of the hydroxycarboxylic acid is preferably a compound having two or more hydroxy groups, more preferably a compound having three or more hydroxy groups, even more preferably a compound having five or more hydroxy groups, and particularly preferably a compound having 5 to 8 hydroxy groups. As an acid having one carboxy group and two or more hydroxy groups, gluconic acid or shikimic acid is preferred. As an acid having two or more carboxy groups and one hydroxy group, citric acid or malic acid is preferable. As an acid having two or more carboxy groups and two or more hydroxy groups, tartaric acid is preferred. Among these, gluconic acid is particularly preferred as the hydroxycarboxylic acid.

[0326] The hydrophilic compounds may be used alone or in combination of two or more. When the undercoat layer contains a hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, the content of the hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, relative to the total mass of the undercoat layer is preferably 0.01% by mass to 50% by mass, more preferably 0.1% by mass to 40% by mass, and particularly preferably 1.0% by mass to 30% by mass.

[0327] In addition to the above-mentioned compounds for the undercoat layer, the undercoat layer may contain a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, etc., to prevent staining over time.

[0328] The undercoat layer is applied by a known method. The coating amount (solid content) of the undercoat layer is 0.1 mg / m 2 ~100mg / m 2 is preferred, and 1 mg / m 2 ~30mg / m 2 is more preferred.

[0329] <Protective layer> The lithographic printing plate precursor according to the present disclosure may have a protective layer (sometimes called an overcoat layer) on the image recording layer. The protective layer has a function of suppressing an image formation inhibiting reaction by blocking oxygen, as well as a function of preventing the occurrence of scratches in the image recording layer and ablation during exposure to a high-intensity laser.

[0330] A protective layer having such characteristics is described, for example, in U.S. Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. As the low oxygen permeability polymer used in the protective layer, either a water-soluble polymer or a water-insoluble polymer can be appropriately selected and used, and two or more types can be mixed and used as necessary. Specific examples include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, water-soluble cellulose derivatives, poly(meth)acrylonitrile, etc. The modified polyvinyl alcohol is preferably an acid-modified polyvinyl alcohol having a carboxy group or a sulfo group, specifically, the modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137.

[0331] The protective layer preferably contains an inorganic layered compound to improve the oxygen barrier properties. The inorganic layered compound is a thin, tabular particle, and examples thereof include mica groups such as natural mica and synthetic mica, talc represented by the formula: 3MgO·4SiO·H2O, taeniolite, montmorillonite, saponite, hectorite, zirconium phosphate, and the like. The inorganic layered compound preferably used is a mica compound. Examples of the mica compound include those represented by the formula: A(B,C) 2-5 D4O 10 Examples of mica include natural mica and synthetic mica represented by the formula (OH,F,O)2 (wherein A is K, Na, or Ca, B and C are Fe(II), Fe(III), Mn, Al, Mg, or V, and D is Si or Al).

[0332] In the mica group, natural micas include muscovite, sodalite, phlogopite, biotite and lepidolite. Synthetic micas include fluorphlogopite KMg3(AlSi3O 10 )F2, potassium tetrasilicic mica KMg 2.5 SiO 10 )F2 and other non-swelling micas, and Na tetrasilicic mica NaMg 2.5 (SiO 10 )F2, Na or Li taeniolite (Na,Li)Mg2Li(SiO 10 ) F2, Na or Li hectorite of the montmorillonite series (Na, Li) 1 / 8 Mg 2 / 5 Li 1 / 8 (SiO 10 Examples of suitable micas include swellable micas such as )F2. Synthetic smectite is also useful.

[0333] Among the above mica compounds, fluorine-based swellable mica is particularly useful. That is, swellable synthetic mica has a layered structure consisting of unit crystal lattice layers with a thickness of about 10 Å to 15 Å (1 Å = 0.1 nm), and the metal atom substitution within the lattice is significantly larger than that of other clay minerals. As a result, the lattice layers have a positive charge deficiency, and to compensate for this, Li is inserted between the layers. + , Na + , Ca 2+ , Mg 2+ The cations present between these layers are called exchangeable cations and can be exchanged with various other cations. In particular, the cations present between the layers are Li + , Na + In the case of , the bond between the layered crystal lattices is weak due to the small ionic radius, and it swells greatly in water. When shear is applied in this state, it easily cleaves and forms a stable sol in water. Swellable synthetic mica has a strong tendency in this case, and is particularly preferred.

[0334] As for the shape of the mica compound, from the viewpoint of diffusion control, the thinner the thickness, the better, and the larger the planar size, the better, as long as it does not impede the smoothness of the coating surface or the transmittance of actinic rays. 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 the particle in a microscopic photograph. The larger the aspect ratio, the greater the effect obtained.

[0335] The particle size 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 in terms of average major axis. The average thickness of the particles is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.01 μm or less. Specifically, for example, in the case of swellable synthetic mica, which is a representative compound, the preferred embodiment has a thickness of about 1 nm to 50 nm and a surface size (major axis) of about 1 μm to 20 μm.

[0336] The content of the inorganic layered compound is preferably 1% by mass to 60% by mass, more preferably 3% by mass to 50% by mass, based on the total solid content of the protective layer. Even when a plurality of inorganic layered compounds are used in combination, the total amount of the inorganic layered compounds is preferably within the above content. Within the above range, oxygen barrier properties are improved and good sensitivity is obtained. Also, deterioration of ink receptivity can be prevented.

[0337] -Color changing compounds- The protective layer preferably contains a color-changing compound. The protective layer may contain other components such as a water-soluble polymer, a hydrophobic polymer, an oil sensitizer, an acid generator, and an infrared absorbing agent in addition to the color-changing compound.

[0338] The lithographic printing plate precursor according to the present disclosure has an energy density of 110 mJ / cm from the viewpoint of improving the visibility of the exposed area. 2 When exposed to infrared light having a wavelength of 830 nm at 1000 nm, the change in brightness ΔL before and after exposure is preferably 2.0 or more. The lightness change ΔL is more preferably 3.0 or more, further preferably 5.0 or more, particularly preferably 8.0 or more, and most preferably 10.0 or more. The upper limit of the lightness change ΔL is, for example, 20.0. In particular, when the protective layer contains a color-changing compound, it is preferable that the lightness change ΔL satisfies the above-mentioned preferred numerical range.

[0339] The change in brightness ΔL is measured by the following method. The lithographic printing plate precursor was exposed to light using a Fujifilm Graphic Systems Co., Ltd. Luxel PLATESETTER T-9800 equipped with an infrared semiconductor laser with a wavelength of 830 nm under the following conditions: output 99.5%, external drum rotation speed 220 rpm (revolutions per minute), resolution 2,400 dpi (dots per inch, 1 inch = 25.4 mm) (energy density 110 mJ / cm 2 The exposure is performed in an environment of 25°C and 50% RH. The change in brightness of the lithographic printing plate precursor before and after exposure is measured. The measurements are performed using the X-Rite eXact spectrophotometer. * a * b * Color space L * The L value (brightness) of the image recording layer after exposure was used. * value and L of the image recording layer before exposure * The absolute value of the difference between the values ​​is taken as the luminance change ΔL.

[0340] In the present disclosure, the term "color-changing compound" refers to a compound whose absorption in the visible light region (wavelength: 400 nm or more and less than 750 nm) changes due to infrared exposure. In other words, in the present disclosure, "color change" refers to a change in absorption in the visible light region (wavelength: 400 nm or more and less than 750 nm) due to infrared exposure. Specifically, the color-changing compounds in the present disclosure include (1) compounds whose absorption in the visible light region increases upon exposure to infrared light compared to before exposure to infrared light, (2) compounds whose absorption in the visible light region comes to be acquired upon exposure to infrared light, and (3) compounds whose absorption in the visible light region comes to be lost upon exposure to infrared light. In addition, the infrared rays in this disclosure are light rays with a wavelength of 750 nm to 1 mm, and preferably light rays with a wavelength of 750 nm to 1,400 nm.

[0341] The color-changing compound preferably includes a compound that develops color due to exposure to infrared light. In addition, the color-changing compound preferably includes a decomposable compound that decomposes due to exposure to infrared rays, and more preferably includes a decomposable compound that decomposes due to heat, electron transfer, or both, caused by exposure to infrared rays. More specifically, the color-changing compound in the present disclosure is preferably a compound that decomposes due to infrared exposure (more preferably, decomposes due to heat, electron transfer, or both caused by infrared exposure) and that exhibits increased absorption in the visible light region or that exhibits absorption at shorter wavelengths in the visible light region compared to before infrared exposure. Here, "decomposed by electron transfer" means that electrons excited from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) of the color-changing compound by exposure to infrared rays undergo intramolecular electron transfer to an electron-accepting group (a group with an electric potential close to that of the LUMO) within the molecule, resulting in decomposition.

[0342] The decomposable compound, which is an example of the discoloration compound, will be described below. The decomposable compound may be any compound that absorbs and decomposes at least a portion of light in the infrared wavelength range (750 nm to 1 mm, preferably 750 nm to 1,400 nm), but is preferably a compound that has a maximum absorption in the wavelength range of 750 nm to 1,400 nm. More specifically, the decomposable compound is preferably a compound that decomposes due to exposure to infrared rays to generate a compound having a maximum absorption wavelength in the wavelength range of 500 nm to 600 nm.

[0343] The decomposable compound is a group that decomposes upon exposure to infrared light (specifically, R 1 ) is preferably a cyanine dye. From the viewpoint of improving the visibility of the exposed area, the decomposable compound is more preferably a compound represented by the following formula 1-1.

[0344] [ka]

[0345] In formula 1-1, R 1 represents a group represented by any one of the following formulas 2 to 4, and R 11 ~R 18 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -SR c , or -NR d R e R a ~R e each independently represents a hydrocarbon group; A1, A2 and a plurality of R 11~R 18 may be linked to form a monocyclic or polycyclic ring, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, n 11 and n 12 Each independently represents an integer of 0 to 5, provided that n 11 and n 12 The sum of is 2 or more, and n 13 and n 14 each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0346] [ka]

[0347] In formulas 2 to 4, R 20 , R 30 , R 41 and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents a bonding site with the group represented by L in formula 1-1 above.

[0348] When the compound of formula 1-1 is exposed to infrared light, R 1 The -L bond is cleaved and L is =O, =S, or =NR 10 and discoloration.

[0349] In Formula 1-1, R 1 represents a group represented by any one of the above formulas 2 to 4. The group represented by formula 2, the group represented by formula 3, and the group represented by formula 4 will be described below.

[0350] In formula 2, R 20 represents an alkyl group or an aryl group, and the wavy line portion represents the bonding site with the group represented by L in formula 1-1. R 20The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and further preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a ring structure. R 20 The aryl group represented by the following formula is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms. R 20 From the viewpoint of color development, the alkyl group is preferably an alkyl group.

[0351] In addition, from the viewpoint of decomposability and color development, R 20 The alkyl group represented by the formula (I) is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. Furthermore, from the viewpoint of decomposability and color development, R 20 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0352] Specific examples of the group represented by the above formula 2 are given below, but the present disclosure is not limited thereto. In the following structural formula, ● represents a bonding site with the group represented by L in formula 1-1.

[0353] [ka]

[0354] In formula 3, R 30 represents an alkyl group or an aryl group, and the wavy line portion represents the bonding site with the group represented by L in formula 1-1. R 30 As the alkyl group and the aryl group represented by the formula 2, R 20The same applies to the alkyl and aryl groups represented by the following formula (1) and preferred embodiments are also the same.

[0355] From the viewpoint of decomposability and color development, R 30 The alkyl group represented by the formula (I) is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. In addition, from the viewpoint of decomposability and color development, R 30 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group. Furthermore, from the viewpoint of decomposability and color development, R 30 The alkyl group represented by the formula (I) is preferably a substituted alkyl group, more preferably a fluoro-substituted alkyl group, further preferably a perfluoroalkyl group, and particularly preferably a trifluoromethyl group.

[0356] From the viewpoint of decomposability and color development, R 30 The aryl group represented by the following formula (I) is preferably a substituted aryl group, and examples of the substituent include an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms) and an alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms).

[0357] Specific examples of the group represented by the above formula 3 are given below, but the present disclosure is not limited thereto. In the following structural formula, ● represents a bonding site with the group represented by L in formula 1-1.

[0358] [ka]

[0359] In formula 4, R 41 and R 42each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line portion represents a bonding site with the group represented by L in formula 1-1. R 41 or R 42 As the alkyl group and the aryl group represented by the formula 2, R 20 The same applies to the alkyl and aryl groups represented by the following formula (1) and preferred embodiments are also the same. R 41 From the viewpoints of decomposability and color development, the alkyl group is preferably an alkyl group. R 42 From the viewpoints of decomposability and color development, the alkyl group is preferably an alkyl group.

[0360] From the viewpoint of decomposability and color development, R 41 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group. From the viewpoint of decomposability and color development, R 42 The alkyl group represented by the formula (I) is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. In addition, from the viewpoint of decomposability and color development, R 42 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0361] Zb in formula 4 may be any counter ion for neutralizing the charge, and the compound as a whole may be included in Za in formula 1-1. Zb is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a tetrafluoroborate ion.

[0362] Specific examples of the group represented by the above formula 4 are given below, but the present disclosure is not limited thereto. In the following structural formula, ● represents a bonding site with the group represented by L in formula 1-1.

[0363] [ka]

[0364] In formula 1-1, L is an oxygen atom or -NR 10 - is preferred, and an oxygen atom is particularly preferred. Also, -NR 10 -R in 10 is preferably an alkyl group. 10 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 10 carbon atoms. 10 The alkyl group represented by the formula (I) may be linear, branched, or have a ring structure. Among the alkyl groups, a methyl group or a cyclohexyl group is preferred. -NR 10 -R in 10 When is an aryl group, it is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms. In addition, these aryl groups may have a substituent.

[0365] In Formula 1-1, R 11 ~R 18 each independently represents a hydrogen atom, -R a , -OR b , -SR c , or -NR d R e It is preferable that: R a ~R e The hydrocarbon group represented by the following formula is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably a hydrocarbon group having 1 to 15 carbon atoms, and even more preferably a hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group may be linear, branched, or have a ring structure. As the above-mentioned hydrocarbon group, an alkyl group is particularly preferred.

[0366] The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and further preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a ring structure. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, a s-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group. Among the alkyl groups, a methyl group, an ethyl group, a propyl group or a butyl group is preferred.

[0367] 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 combinations thereof.

[0368] R in Formula 1-1 11 ~R 14 Each independently represents a hydrogen atom or -R a (that is, a hydrocarbon group), more preferably a hydrogen atom or an alkyl group, and further preferably a hydrogen atom, except in the following cases. Among them, R bonded to the carbon atom bonded to L and the carbon atom bonded to 11 and R 13is preferably an alkyl group, and more preferably the two are linked to form a ring. The ring formed may be a monocyclic ring or a polycyclic ring. Specific examples of the ring formed include monocyclic rings such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, and a cyclohexadiene ring, and polycyclic rings such as an indene ring and an indole ring. Also, A1 + R attached to the carbon atom to which 12 is R 15 or R 16 (Preferably R 16 ) to form a ring, and R bonded to the carbon atom to which A2 is bonded is preferably 14 is R 17 or R 18 (Preferably R 18 ) to form a ring.

[0369] In formula 1-1, n 13 is 1, and R 16 -R a (i.e., a hydrocarbon group). Also, R 16 is A1 + R attached to the carbon atom to which 12 It is preferable that the ring is formed by linking with the ring. The ring formed is preferably an indolium ring, a pyrylium ring, a thiopyrylium ring, a benzoxazoline ring, or a benzimidazoline ring, and from the viewpoint of improving the visibility of the exposed part, an indolium ring is more preferable. These rings may further have a substituent. In formula 1-1, n 14 is 1, and R 18 -R a (i.e., a hydrocarbon group). Also, R 18 is the R bonded to the carbon atom to which A2 is bonded. 14 It is preferable that the ring is formed by linking with the above ring. The ring formed is preferably an indole ring, a pyran ring, a thiopyran ring, a benzoxazole ring, or a benzimidazole ring, and from the viewpoint of improving the visibility of the exposed part, an indole ring is more preferable. These rings may further have a substituent. R in Formula 1-1 16 and R 18 are preferably the same group, and when each of them forms a ring, A1 + and A2, it is preferable that they form a ring having the same structure.

[0370] R in Formula 1-1 15 and R 17 are preferably the same group. 15 and R 17 -R a (that is, a hydrocarbon group), more preferably an alkyl group, and further preferably a substituted alkyl group.

[0371] In the compound represented by formula 1-1, from the viewpoint of improving water solubility, R 15 and R 17 is preferably a substituted alkyl group. R 15 or R 17 Examples of the substituted alkyl group represented by the formula (a1) include groups represented by any of the following formulas (a1) to (a4).

[0372] [ka]

[0373] In 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 from 1 to 45, and R W1 is an alkyl group having 1 to 12 carbon atoms or -C(=O)-R W5 R W5 represents an alkyl group having 1 to 12 carbon atoms, R W2 ~R W4 each independently represents a single bond or an alkylene group having 1 to 12 carbon atoms, and M represents a hydrogen atom, a sodium atom, a potassium atom, or an onium group.

[0374] In formula (a1), R W0Specific examples of the alkylene group represented by the formula (I) include an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, and the like. Of these, an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferred, and an n-propylene group is particularly preferred. n W1 is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3. R W1 Specific examples of the alkyl group represented by the formula (I) 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, a neopentyl group, an n-hexyl group, an n-octyl group, and an n-dodecyl group. Of these, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or a tert-butyl group is preferred, a methyl group or an ethyl group is more preferred, and a methyl group is particularly preferred. R W5 The alkyl group represented by R W1 The preferred embodiment is the same as the alkyl group represented by R W1 The preferred embodiments are the same as those of the alkyl group represented by the following formula:

[0375] Specific examples of the group represented by formula (a1) are shown below, but the present disclosure is not limited thereto. In the following structural formula, Me represents a methyl group, Et represents an ethyl group, and * represents a bonding site.

[0376] [ka]

[0377] In formula (a2) to formula (a4), R W2 ~R W4Specific examples of the alkylene group represented by the formula (I) include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, an n-octylene group, and an n-dodecylene group. An ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferred, and an ethylene group or an n-propylene group is particularly preferred. In formula (a3), the two M's may be the same or different.

[0378] In the formulae (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. CO2M in formula (a2), PO3M2 in formula (a2), and SO3M in formula (a4) may each have an anionic structure in which M is dissociated. The counter cation of the anionic structure is A1 + R in formula 1-1 may be 1 -L may be a cation that can be contained therein.

[0379] Among the groups represented by formulae (a1) to (a4), the groups represented by formula (a1), formula (a2) or formula (a4) are preferred.

[0380] n in Formula 1-1 11 and n 12 are preferably the same, and both are preferably an integer of 1 to 5, more preferably an integer of 1 to 3, further preferably 1 or 2, and particularly preferably 2.

[0381] In formula 1-1, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, and preferably a nitrogen atom. In formula 1-1, A1 and A2 are preferably the same atom.

[0382] Za in formula 1-1 represents a counter ion that neutralizes the charge. R 11 ~R 18 and R 1If all of -L are charge-neutral groups, Za is a monovalent counter anion. 11 ~R 18 and R 1 -L may have an anionic or cationic structure, for example, R 11 ~R 18 and R 1 When -L has two or more anion structures, Za can also be a counter cation. If the cyanine dye represented by formula 1-1 has a structure in which the entire compound is charge neutral except for Za, Za is not necessary. When Za is a counter anion, examples of the counter anion include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, a perchlorate ion, and the like, with the tetrafluoroborate ion being preferred. When Za is a counter cation, examples of the counter cation include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, and a sulfonium ion. Of these, a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is preferred, and a sodium ion, a potassium ion, or an ammonium ion is more preferred.

[0383] From the viewpoint of improving the visibility of the exposed area, the decomposable compound is more preferably a compound represented by the following formula 1-2 (that is, a cyanine dye).

[0384] [ka]

[0385] In formula 1-2, R 1 represents a group represented by any one of the above formulas 2 to 4, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e R23 and R 24 Each independently represents a hydrogen atom or -R a R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , or R 23 and R 24 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion which neutralizes the charge.

[0386] R in Formula 1-2 1 is R in formula 1-1 1 The same applies to the preferred embodiments.

[0387] In formula 1-2, R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, -R a , -OR b or -CN. More specifically, R 19 and R 21 is a hydrogen atom or -R a It is preferable that: Also, R 20 and R 22 is a hydrogen atom, -R a , -OR b or -CN. R 19 ~R 22 Represented by -R a As the group, an alkyl group or an alkenyl group is preferable. R 19 ~R 22 All of the above are -R aIf R 19 and R 20 and R 21 and R 22 are preferably linked to form a monocyclic or polycyclic ring. R 19 and R 20 or R 21 and R 22 Examples of the ring formed by linking include a benzene ring and a naphthalene ring.

[0388] In formula 1-2, R 23 and R 24 are preferably linked to form a monocycle or polycycle. R 23 and R 24 The ring formed by linking may be a monocycle or a polycycle. Specific examples of the ring formed include monocycles such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, and a cyclohexadiene ring, and polycycles such as an indene ring.

[0389] In formula 1-2, R d1 ~R d4 is preferably an unsubstituted alkyl group. d1 ~R d4 are preferably the same group. The unsubstituted alkyl group may be an unsubstituted alkyl group having 1 to 4 carbon atoms, and among these, a methyl group is preferable.

[0390] In formula 1-2, W 1 and W 2 are each preferably independently a substituted alkyl group from the viewpoint of increasing the water solubility of the compound represented by formula 1-2. W 1 and W 2 Examples of the substituted alkyl group represented by the formula (a1) include groups represented by any one of formulas (a1) to (a4) in formula 1-1, and preferred embodiments are also the same. Also, W 1 and W 2are each independently, from the viewpoint of on-press developability, an alkyl group having a substituent, and the substituent is preferably a group having at least -(OCHCH)-, a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group.

[0391] Za represents a counter ion that neutralizes the charge in the molecule. R 19 ~R 22 , R 23 ~R 24 , R d1 ~R d4 , W 1 , W 2 , and R 1 If all of -L are charge-neutral groups, Za is a monovalent counter anion. 19 ~R 22 , R 23 ~R 24 , R d1 ~R d4 , W 1 , W 2 , and R 1 -L may have an anionic or cationic structure, for example, R 19 ~R 22 , R 23 ~R 24 , R d1 ~R d4 , W 1 , W 2 , and R 1 When -L has two or more anion structures, Za can also be a counter cation. In addition, when the compound represented by formula 1-2 has a structure in which the entire compound is charge neutral except for Za, Za is not necessary. Examples of Za when it is a counter anion are the same as Za in formula 1-1, and preferred embodiments are also the same. Examples of Za when it is a counter cation are the same as Za in formula 1-1, and preferred embodiments are also the same.

[0392] From the viewpoints of decomposability and color development, the cyanine dye as the decomposable compound is more preferably a compound represented by any one of the following formulas 1-3 to 1-7. In particular, from the viewpoints of decomposability and color development, a compound represented by any one of formulas 1-3, 1-5, and 1-6 is preferred.

[0393] [ka]

[0394] In formulas 1-3 to 1-7, R 1 represents a group represented by any one of the above formulas 2 to 4, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e R 25 and R 26 each independently represents a hydrogen atom, a halogen atom, or -R a R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , or R 25 and R 26 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion which neutralizes the charge.

[0395] R in Formulas 1-3 to 1-7 1 , R 19 ~R 22 , R d1 ~R d4 , W 1 , W 2 , and L is R in Formula 1-2 1 , R 19 ~R22 , R d1 ~R d4 , W 1 , W 2 and L, and the preferred embodiments are also the same. R in Formula 1-7 25 and R 26 are each independently preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, and particularly preferably a methyl group.

[0396] Specific examples of cyanine dyes that are decomposable compounds are listed below, but the present disclosure is not limited thereto.

[0397] [ka]

[0398] In addition, as the cyanine dye, which is a decomposable compound, the infrared absorbing compounds described in WO 2019 / 219560 can be suitably used.

[0399] The color-changing compound may also contain an acid color former. As the acid color former, those described as the acid color former in the image recording layer can be used, and the preferred embodiments are also the same.

[0400] The color-changing compound may be used alone or in combination of two or more components. As the color-changing compound, the above-mentioned decomposable compound and the below-mentioned acid generator may be used in combination.

[0401] From the viewpoint of color development, the content of the color-changing compound in the protective layer is preferably 0.10% by mass to 50% by mass, more preferably 0.50% by mass to 30% by mass, and even more preferably 1.0% by mass to 20% by mass, based on the total mass of the protective layer.

[0402] The content M of the color-changing compound in the protective layer X and the content M of the infrared absorbing agent in the image recording layer.Y Compared to M X / M Y However, from the viewpoint of color development, it is preferably 0.1 or more, more preferably 0.2 or more, and particularly preferably 0.3 or more and 3.0 or less.

[0403] -Water-soluble polymer- The protective layer preferably contains a water-soluble polymer from the viewpoint of removability during development (more preferably, on-machine developability). In the present disclosure, a water-soluble polymer refers to a polymer that dissolves at least 1 g in 100 g of pure water at 70°C and does not precipitate even when a solution in which 1 g of the polymer is dissolved in 100 g of pure water at 70°C is cooled to 25°C. Examples of the water-soluble polymer used in the protective layer include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, water-soluble cellulose derivatives, polyethylene glycol, and poly(meth)acrylonitrile. The modified polyvinyl alcohol is preferably an acid-modified polyvinyl alcohol having a carboxy group or a sulfo group, specifically, the modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137.

[0404] The water-soluble polymer is preferably polyvinyl alcohol, and more preferably, the water-soluble polymer is polyvinyl alcohol having a degree of saponification of 50% or more. The degree of saponification is preferably 60% or more, more preferably 70% or more, and even more preferably 85% or more. There is no particular upper limit to the degree of saponification, so long as it is 100% or less. The degree of saponification is measured according to the method described in JIS K 6726:1994.

[0405] As the water-soluble polymer, polyvinylpyrrolidone is also preferred. As the hydrophilic polymer, it is also preferable to use polyvinyl alcohol and polyvinylpyrrolidone in combination.

[0406] The water-soluble polymers may be used alone or in combination of two or more kinds.

[0407] When the protective layer contains a water-soluble polymer, the content of the water-soluble polymer is preferably 1% by mass to 99% by mass, more preferably 3% by mass to 97% by mass, and even more preferably 5% by mass to 95% by mass, relative to the total mass of the protective layer.

[0408] -Other ingredients- The protective layer may contain other components such as a hydrophobic polymer, an oil sensitizer, an acid generator, and an infrared absorbing agent in addition to the above-mentioned color-changing compound and water-soluble polymer. The other ingredients will be described below.

[0409] [Hydrophobic polymer] The protective layer preferably contains a hydrophobic polymer. The hydrophobic polymer refers to a polymer which dissolves in 100 g of pure water at 70° C. in an amount of less than 1 g or which does not dissolve at all. Examples of hydrophobic polymers include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly(alkyl(meth)acrylate)s (e.g., poly(methyl(meth)acrylate), poly(ethyl(meth)acrylate), poly(butyl(meth)acrylate), and copolymers of combinations of raw material monomers for these polymers. The hydrophobic polymer preferably contains a polyvinylidene chloride resin. Furthermore, the hydrophobic polymer preferably contains a styrene-acrylic copolymer. Furthermore, from the viewpoint of on-press developability, the hydrophobic polymer is preferably in the form of hydrophobic polymer particles.

[0410] The hydrophobic polymer may be used alone or in combination of two or more kinds.

[0411] When the protective layer contains a hydrophobic polymer, the content of the hydrophobic polymer is preferably from 1 to 80% by mass, and more preferably from 5 to 50% by mass, based on the total mass of the protective layer.

[0412] [Oil Sensitizer] From the viewpoint of ink receptivity, the protective layer preferably contains an oil sensitizer. As the oil sensitizer used in the protective layer, the oil sensitizers described in the image recording layer can be used, and the preferred embodiments are also the same.

[0413] The oil sensitizer may be used alone or in combination of two or more kinds. When the protective layer contains an oil sensitizer, the content of the oil sensitizer is preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass, based on the total mass of the protective layer.

[0414] [Acid Generator] When an acid color former is used as the color-changing compound, the protective layer preferably contains an acid generator. In the present disclosure, the term "acid generator" refers to a compound that generates an acid when exposed to light or heat, and specifically refers to a compound that decomposes when exposed to infrared light to generate an acid. The acid generated is preferably a strong acid such as sulfonic acid or hydrochloric acid having a pKa of 2 or less. The acid generated from the acid generator can cause the above-mentioned acid color former to change color.

[0415] Specifically, from the viewpoints of sensitivity and stability, the acid generator is preferably an onium salt compound. Specific examples of onium salts suitable as acid generators include the compounds described in paragraphs 0121 to 0124 of WO 2016 / 047392. Among them, triarylsulfonium or diaryliodonium sulfonates, carboxylates, BPh4 - , BF4 - , PF6 - , ClO4 -etc. are preferred. Here, Ph represents a phenyl group.

[0416] The acid generator may be used alone or in combination of two or more kinds. When the protective layer contains an acid generator, the content of the acid generator is preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass, based on the total mass of the protective layer.

[0417] The protective layer may contain known additives such as inorganic layer compounds and surfactants in addition to the components already described.

[0418] The protective layer is formed by applying the coating material by a known method and drying the applied coating material. The coating weight (solid content) of the protective layer is 0.01 g / m 2 ~10g / m 2 is preferred, and 0.02 g / m 2 ~3g / m 2 More preferably, 0.1 g / m 2 ~2.0g / m 2 is particularly preferred. The thickness of the protective layer is preferably from 0.1 μm to 5.0 μm, and more preferably from 0.3 μm to 4.0 μm.

[0419] The thickness of the protective layer is preferably 0.1 to 5.0 times, and more preferably 0.2 to 3.0 times, the thickness of the image recording layer described below.

[0420] The protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coatability, and inorganic particles for controlling the surface slipperiness.

[0421] (Method of making a lithographic printing plate and method of lithographic printing) A lithographic printing plate can be prepared by imagewise exposing the lithographic printing plate precursor according to the present disclosure and then subjecting it to a development treatment. The method for producing a lithographic printing plate according to the present disclosure preferably includes a step of exposing the lithographic printing plate precursor according to the present disclosure to light in an imagewise manner (hereinafter also referred to as an "exposure step"), and a step of removing the image recording layer in the non-image areas on the printing press by supplying at least one selected from the group consisting of printing ink and fountain solution (hereinafter also referred to as an "on-press development step"). The lithographic printing method according to the present disclosure preferably includes a step of exposing the lithographic printing plate precursor according to the present disclosure in an imagewise manner (exposure step), a step of supplying at least one selected from the group consisting of printing ink and fountain solution to remove the image recording layer in non-image areas on the printing press to prepare a lithographic printing plate (on-press development step), and a step of printing with the obtained lithographic printing plate (printing step). Hereinafter, preferred aspects of each step of the method for producing a lithographic printing plate according to the present disclosure and the lithographic printing method according to the present disclosure will be described in order. Note that the lithographic printing plate precursor according to the present disclosure can also be developed with a developer. The exposure step and on-press development step in the method for preparing a lithographic printing plate will be described below, 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, and the on-press development step in the method for preparing a lithographic printing plate according to the present disclosure is the same as the on-press development step in the lithographic printing method according to the present disclosure. It is also assumed that during on-press development, the outermost layer is partially removed and partially remains on the surface of the image area or penetrates into the inside of the image area with the printing ink.

[0422] <Exposure process> The method for producing a lithographic printing plate according to the present disclosure preferably includes an exposure step of imagewise exposing the lithographic printing plate precursor according to the present disclosure to form an exposed area and an unexposed area. The lithographic printing plate precursor according to the present disclosure is preferably imagewise exposed by laser exposure through a transparent original having a line image, a halftone dot image, or the like, or by laser light scanning based on digital data. The wavelength of the light source is preferably 750 nm to 1,400 nm. As a light source with a wavelength of 750 nm to 1,400 nm, a solid-state laser or a semiconductor laser that emits infrared rays is suitable. With regard to the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably 20 microseconds or less, and the amount of irradiation energy is preferably 10 mJ / cm. 2 ~300mJ / cm 2 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 type, an external drum type, a flatbed type, and the like. Image exposure can be carried out by a conventional method using a plate setter, etc. In the case of on-press development, the lithographic printing plate precursor may be mounted on a printing press and then image exposure may be carried out on the printing press.

[0423] <On-press development process> The method for producing a lithographic printing plate according to the present disclosure preferably includes an on-press development step of supplying at least one selected from the group consisting of printing ink and fountain solution to remove the image recording layer in non-image areas on the printing press. The on-press development method will be described below.

[0424] [On-press development method] In the on-press development method, it is preferable that an oil-based ink and an aqueous component are supplied to the image-exposed lithographic printing plate precursor on a printing press, and the image recording layer in the non-image areas is removed to prepare a lithographic printing plate. That is, after image exposure, the lithographic printing plate precursor is mounted on a printing press as it is without any development treatment, or the lithographic printing plate precursor is mounted on a printing press and then image exposure is performed on the printing press, and then an oil-based ink and an aqueous component are supplied to print. In the early stage of printing, the uncured image recording layer is dissolved or dispersed by either or both of the supplied oil-based ink and aqueous component in the non-image area and removed, exposing a hydrophilic surface in that area. On the other hand, in the exposed area, the image recording layer cured by exposure forms an oil-based ink receptive area having an oleophilic surface. The first thing supplied to the plate surface may be an oil-based ink or an aqueous component, but it is preferable to supply an oil-based ink first in order to prevent the aqueous component from being contaminated by the component of the image recording layer that has been removed. In this way, the lithographic printing plate precursor is developed on the press and used as it is for printing a large number of sheets. As the oil-based ink and aqueous component, printing ink and fountain solution for normal lithographic printing are preferably used.

[0425] As the laser for imagewise exposing the lithographic printing plate precursor according to the present disclosure, the wavelength of the light source is preferably 300 nm to 450 nm or 750 nm to 1,400 nm. In the case of a light source 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 as the light source having a wavelength of 750 nm to 1,400 nm, the above-mentioned light sources are preferably used. As the light source having a wavelength of 300 nm to 450 nm, a semiconductor laser is suitable.

[0426] <Developer development process> The method for producing a lithographic printing plate according to the present disclosure may be a method including a step of exposing the lithographic printing plate precursor according to the present disclosure to light in an imagewise manner, and a step of removing the image recording layer in the non-image area using a developer to produce a lithographic printing plate (also referred to as a "developer development step"). In addition, the lithographic printing method according to the present disclosure may be a method including the steps of exposing the lithographic printing plate precursor according to the present disclosure to light in an imagewise manner, removing the image recording layer in the non-image areas with a developer to prepare a lithographic printing plate, and printing with the obtained lithographic printing plate. As the developer, a known developer can be used. The pH of the developer is not particularly limited and may be a strong alkaline developer, but preferred examples of the developer have a pH of 2 to 11. Preferred examples of the developer having a pH of 2 to 11 include developers containing at least one of a surfactant and a water-soluble polymer compound. In the development process using a strong alkaline developer, the protective layer is removed in a pre-washing step, followed by alkaline development, the alkali is removed in a post-washing step, a gum solution treatment is performed, and then drying is performed in a drying step. In addition, when using the above-mentioned developer containing a surfactant or a water-soluble polymer compound, development and gum solution treatment can be performed simultaneously. Therefore, a post-rinsing step is not particularly required, and development and gum solution treatment can be performed with one solution, followed by a drying step. Furthermore, removal of the protective layer can be performed simultaneously with development and gum solution treatment, so a pre-rinsing step is not particularly required. After development, it is preferable to remove excess developer using a squeeze roller or the like, and then perform drying.

[0427] <Printing process> The lithographic printing method according to the present disclosure includes a printing step of supplying printing ink to a lithographic printing plate to print a recording medium. The printing ink is not particularly limited, and various known inks can be used as desired. Preferred examples of the printing ink include oil-based inks and ultraviolet-curable inks (UV inks). In the printing process, dampening water may be supplied as necessary. The printing step may be carried out consecutively to the on-press development step or the developer development step without stopping the printing press. The recording medium is not particularly limited, and any known recording medium can be used as desired.

[0428] In the method for preparing a lithographic printing plate from a lithographic printing plate precursor according to the present disclosure and the lithographic printing method according to the present disclosure, the entire surface of the lithographic printing plate precursor may be heated as necessary before exposure, during exposure, or between exposure and development. Such heating promotes the image formation reaction in the image recording layer, and can provide advantages such as improved sensitivity and printing durability and stabilization of sensitivity. Heating before development is preferably performed under mild conditions of 150° C. or less. In the above embodiment, problems such as hardening of non-image areas can be prevented. For heating after development, stronger conditions than those described above are preferably used, and the range is preferably 100° C. to 500° C. In the above range, sufficient image strengthening effect can be obtained, and problems such as deterioration of the support and thermal decomposition of the image area can be suppressed. EXAMPLES

[0429] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited thereto. In the examples, "%" and "parts" mean "% by mass" and "parts by mass", respectively, unless otherwise specified.

[0430] <Synthesis of polymers P1 to P9> A mixed solution of 4.7 parts by mass of polyisocyanate (all manufactured by Mitsui Chemicals, Inc.) shown in Table 1, hydroxyl group-containing polyfunctional acrylate (all manufactured by Toagosei Co., Ltd.) shown in Table 1 in an amount such that the NCO value of the polyisocyanate and the hydroxyl group value of the hydroxyl group-containing polyfunctional acrylate are 1:1, 0.02 parts by mass of t-butylbenzoquinone, and 11.5 parts by mass of methyl ethyl ketone was heated to 65°C. 0.11 parts by mass of Neostan U-600 (bismuth-based polycondensation catalyst, manufactured by Nitto Kasei Co., Ltd.) was added to the reaction solution, and the mixture was heated at the same temperature for 4 hours. The reaction solution was cooled to room temperature (25°C) and methyl ethyl ketone was added to synthesize a urethane acrylate solution with a solid content of 50% by mass. Next, the urethane acrylate solution was subjected to molecular weight fractionation using a recycle GPC (instrument: LC908-C60, columns: JAIGEL-1H-40 and 2H-40 (manufactured by Japan Analytical Industry Co., Ltd.)) with tetrahydrofuran (THF) eluent. Then, P1 to P9 listed in Table 1 were obtained, respectively.

[0431] <Measurement of weight average molecular weight (Mw) and ethylenically unsaturated bond value (C=C value)> The weight average molecular weight Mw of the compound was measured by the following measuring device and method. GPC measurement equipment: TOSOH HLC-8320GPC, GPC fluid phase: THF Inspection equipment: Differential refractive index detector (RI), flow rate: 0.35mL / min Columns: TSKgel SuperHZM-M, TSKgel SuperHZ4000, TSKgel SuperHZ3000, and TSKgel SuperHZ2000 were used in combination. Column temperature: 40℃ Standard sample for molecular weight calibration curve: Polystyrene (PS) In addition, the ethylenically unsaturated bond valence (C=C valence) of the compound is 1 The (model) structure of the compound was analyzed and calculated by H-NMR measurement.

[0432] P13: A star-shaped polymer having the following structure. The composition of the polymer chain shown below is a / b / c=33 / 42 / 25 in terms of the polymerization molar ratio of monomers. P14: Star polymer having the following structure. The composition of the polymer chain shown below is a / b / c=4.7 / 46.8 / 48.5 in terms of the polymerization molar ratio of monomers.

[0433] [ka]

[0434] [Table 1]

[0435] <Preparation of support> An aluminum alloy plate of material 1S having a thickness of 0.3 mm was subjected to (Aa) mechanical roughening treatment (brush grain method) described in paragraph 0126 of JP2012-158022A to (Ai) desmutting treatment in an acidic aqueous solution described in paragraph 0134 of JP2012-158022A. Next, the conditions for each of the treatments, from (Aj) the first-stage anodizing treatment described in paragraph 0135 of JP 2012-158022 A to (Am) the third-stage anodizing treatment described in paragraph 0138, were appropriately adjusted to form an anodized coating having large-diameter pores with an average diameter of 35 nm and a depth of 100 nm and small-diameter pores with an average diameter of 10 nm and a depth of 1,000 nm, with the ratio of the depth of the large-diameter pores to the average diameter of the large-diameter pores being 2.9, thereby obtaining an aluminum support A. In addition, a water washing treatment was carried out between all the processing steps, and after the water washing treatment, the liquid was removed by using nip rollers.

[0436] <Formation of lithographic printing plate precursor> On the above-mentioned support A (printing surface side), a coating solution for an undercoat layer having the following composition was applied in a dry amount of 87 mg / m 2 The undercoat layer was formed by coating so as to become The image recording layer coating solution (1) described below was applied onto the undercoat layer with a bar and dried in an oven at 120° C. for 40 seconds to obtain a dry coating amount of 0.971 g / m 2 An image recording layer of the above formula was formed, and a lithographic printing plate precursor was obtained. The image recording layer coating solution (1) containing polymer particles (microgel) was prepared by mixing and stirring a photosensitive solution containing components other than the microgel solution described below with the microgel solution described below just before coating.

[0437] <Coating solution for undercoat layer> Undercoat layer compound (P-1): 0.1370 parts Sodium gluconate: 0.0700 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts Preservative (Biohope L, manufactured by K.I. Kasei Co., Ltd.): 0.00149 parts ·Wed: 3.29000 copies

[0438] [ka]

[0439] <Image recording layer coating liquid (1)> IR-1 (infrared absorbing agent, compound below): 0.01970 parts Color developer (S-15): 0.02000 parts IA-1 (electron-accepting polymerization initiator, compound below) 0.11000 parts Borate compound (sodium tetraphenylborate, electron donating polymerization initiator): the amount listed in Table 2 Polymer A shown in Table 2: Amount shown in Table 2 Polymerizable compound B described in Table 2: the amount described in Table 2 M-1 (polymerizable compound C, the following compound): 0.00244 parts Anionic surfactant (A-1, the compound shown below): the amount shown in Table 2 Fluorine-based surfactant (W-1, the following compound): 0.00416 parts 2-Butanone: 4.92 parts 1-Methoxy-2-propanol: 3.10 parts Methanol: 2.79 parts Microgel liquid: 2.32 parts

[0440] [Infrared absorbing agent] IR-1: Compound having the following structure, HOMO=-5.35 eV, LUMO=-3.73 eV, where Ph represents a phenyl group.

[0441] [ka]

[0442] Color former (S-15): The following compound

[0443] [ka]

[0444] [Electron Acceptor Polymerization Initiator] IA-1: Compound having the following structure, LUMO=-3.02 eV, where Me represents a methyl group.

[0445] [ka]

[0446] [Polymerizable compound C] M-1: Dipentaerythritol hexaacrylate, Aronix M-403 (penta(%) 50-60), manufactured by Toagosei Co., Ltd.

[0447] [Surfactant] Anionic surfactant (A-1): The following compound Fluorosurfactant (W-1): The following compound

[0448] [ka]

[0449] [ka]

[0450] <Preparation of microgel solution> Microgel (polymer particles): 2.640 parts Distilled water: 2.425 parts The method for preparing the microgel used in the above microgel solution is as follows.

[0451] -Preparation of polyisocyanate compounds- To a suspension of 17.78 parts (80 molar equivalents) of isophorone diisocyanate and 7.35 parts (20 molar equivalents) of the following polyhydric phenol compound (1) in ethyl acetate (25.31 parts), 0.043 parts of bismuth tris(2-ethylhexanoate) (Neostan U-600, manufactured by Nitto Kasei Co., Ltd.) was added and stirred. When the heat generation subsided, the reaction temperature was set to 50°C, and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50% by mass) of the polyhydric isocyanate compound (1).

[0452] [ka]

[0453] -Preparation of microgels- The following oil phase components and water phase components were mixed and emulsified for 10 minutes at 12,000 rpm using a homogenizer. The resulting emulsion was stirred at 45°C for 4 hours, and then 5.20 g of a 10% by mass aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, San-Apro Co., Ltd.) was added, stirred at room temperature for 30 minutes, and allowed to stand at 45°C for 24 hours. The solid content was adjusted to 20% by mass with distilled water, and an aqueous dispersion of microgel (1) was obtained. The average particle size was measured by a light scattering method and found to be 0.28 μm.

[0454] ~Oily phase components~ (Component 1) Ethyl acetate: 12.0 parts (Component 2) 3.76 parts of an adduct (50% by mass in ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.) obtained by adding trimethylolpropane (6 molar equivalents) and xylylene diisocyanate (18 molar equivalents) to which one-terminal methylated polyoxyethylene (1 molar equivalent, number of repeating oxyethylene units: 90) has been added. (Component 3) Polyisocyanate compound (1) (as a 50% by mass solution in ethyl acetate): 15.0 parts (Component 4) 65% by weight solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Corporation) in ethyl acetate: 11.54 parts (Component 5) 10% ethyl acetate solution of sulfonate surfactant (Paionin A-41-C, Takemoto Oil Co., Ltd.): 4.42 parts

[0455] ~Aqueous phase components~ Distilled water: 46.87 parts

[0456] <Evaluation> (1) UV-curable ink printing durability (UV printing durability) The lithographic printing plate precursor prepared as described above was exposed to light (irradiation energy 110 mJ / cm) using a Kodak Magnus800 Quantum equipped with an infrared semiconductor laser under the conditions of an output of 27 W, an outer drum rotation speed of 450 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch is 2.54 cm). 2The exposure image included a solid image and an AM screen (Amplitude Modulation Screen) 10% halftone dot chart. The exposed plate obtained was attached to the cylinder of a Heidelberg SX-74 printing press of the 1900 format without development. A 100 L dampening water circulating tank with a built-in nonwoven fabric filter and temperature control device was connected to this printing press. 80 L of 2.0% dampening water S-Z1 (FUJIFILM Corporation) was charged into the circulating device, and T&K UV OFS K-HS Sumi GE-M (T&K TOKA Corporation) was used as the printing ink. After supplying the dampening water and ink using the standard automatic printing start method, 500 sheets were printed on Tokubishi Art paper (ream weight: 76.5 kg, Mitsubishi Paper Mills Co., Ltd.) at a printing speed of 10,000 sheets per hour. Further printing was then carried out. As the number of prints increased, the image area gradually wore away, causing the ink density on the prints to decrease. The number of prints when the dot area ratio of the AM screen 10% dots on the prints, measured with a Gretag densitometer (manufactured by GretagMacbeth), was 3% lower than the measurement value on the 500th print, was taken as the number of prints completed and printing durability was evaluated. Relative printing durability, with 50,000 prints taken as 100, was evaluated according to the following criteria. The higher the value, the better the printing durability. The evaluation results are shown in Table 2. Relative printing durability = (number of prints of the target lithographic printing plate precursor) / 50,000 x 100 -Evaluation criteria- A: Relative printing durability value exceeds 90 B: The relative printing durability value is more than 75 and is 90 or less. C: Relative printing durability is 75 or less

[0457] (2) UV plate skipping prevention The lithographic printing plate precursor prepared as described above was exposed to light (irradiation energy 110 mJ / cm) using a Kodak Magnus800 Quantum equipped with an infrared semiconductor laser under the conditions of an output of 27 W, an outer drum rotation speed of 450 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch is 2.54 cm). 2The exposure image included a solid image and an AM screen (Amplitude Modulated Screening) 3% halftone dot chart. A 0.4 mm diameter piano wire (manufactured by Esco Co., Ltd.) was attached to the halftone dots of the obtained exposed original plate in a direction perpendicular to the rotation direction of the plate cylinder, and without development processing, it was attached to the cylinder of a Heidelberg SX-74 printing press of 1920 size. A 100 L capacity dampening water circulation tank with a built-in nonwoven fabric filter and temperature control device was connected to this printing press. 80 L of dampening water S-Z1 (manufactured by Fujifilm Co., Ltd.) 2.0% dampening water was charged into the circulation device, and T&K UV OFS K-HS ink GE-M (manufactured by T&K TOKA Co., Ltd.) was used as printing ink. After supplying dampening water and ink using the standard automatic printing start method, printing was performed on Tokubishi Art paper (manufactured by Mitsubishi Paper Mills Co., Ltd., ream weight: 76.5 kg) at a printing speed of 10,000 sheets per hour. When the number of printed sheets reached 2,000, the piano wire was removed from the plate, and it was set back on the printing press, and printing was started again. After restarting, the 100th printed sheet was checked, and the image area corresponding to the position of the piano wire was confirmed, and a 50x magnifying glass was used to visually check whether there was any ink adhesion failure. Checks were made in the same way every 2,000 sheets, and the evaluation was terminated when ink adhesion failure occurred. The evaluation results are shown in Table 2. -Evaluation criteria- A: The number of prints before plate skipping occurs on a lithographic printing plate is 20,000 or more. B: The number of printed sheets before "plate skipping" occurs in the lithographic printing plate is 4,000 sheets or more and less than 20,000 sheets. C: The number of printed sheets before "plate skipping" occurs in the lithographic printing plate is less than 4,000 sheets.

[0458] [Table 2]

[0459] The results shown in Table 2 show that the planographic printing plate precursors of Examples 1 to 11, which are planographic printing plate precursors according to the present disclosure, provide planographic printing plates with excellent printing durability even when UV ink is used. Furthermore, from the results shown in Table 2, the lithographic printing plate precursors of Examples 1 to 11, which are the lithographic printing plate precursors according to the present disclosure, are also excellent in suppressing UV plate skipping.

[0460] (Examples 12 to 22) The steps up to the formation of the image recording layer were the same as in Example 11.

[0461] <Formation of protective layer> A protective layer coating solution containing the components shown in Table 4 below (wherein the protective layer coating solution contained each component shown in Table 4 and was prepared so that the solid content was 20 mass % by ion exchange) was applied onto the image recording layer with a bar, and dried in an oven at 120° C. for 60 seconds to obtain a dry coating amount of 0.50 g / m 2 A protective layer of Through the above steps, a lithographic printing plate precursor was obtained.

[0462] <Evaluation of lithographic printing plate precursors> The UV plate skipping property and UV printing durability were evaluated in the same manner as above.

[0463] [On-press developability] The exposed original plate obtained in the same manner as in the evaluation of UV plate skipping was attached to the cylinder of a Heidelberg SX-74 printing machine with a size of 636 mm x 939 mm without development. A 100 L dampening water circulation tank with a built-in nonwoven fabric filter and temperature control device was connected to this printing machine. 80 L of dampening water containing 2.0 mass % of dampening water S-Z1 (manufactured by Fujifilm Corporation) was charged into the circulation device, and T&K UV OFS K-HS ink GE-M (manufactured by T&K TOKA Corporation), which is a UV-curable ink, was used as the printing ink. After supplying the dampening water and ink using the standard automatic printing start method, printing was performed on 500 sheets of Tokubishi Art paper (ream weight: 76.5 kg, Mitsubishi Paper Mills Co., Ltd.) at a printing speed of 10,000 sheets per hour. During printing, the number of sheets of printing paper required until no ink was transferred to the non-image areas was measured as on-press developability. The fewer the number of sheets, the better the on-press developability. The results are shown in Table 3. The obtained lithographic printing plate precursor was irradiated with white light for 2 hours at room temperature (25°C) and 50% humidity using a Mitsubishi Electric OSRAM FLR40SW fluorescent lamp as a light source and a Tokyo Koden pocket illuminometer ANA-F9 model at an illuminance of 1000lx. The irradiated lithographic printing plate was used to measure on-press developability in the same manner as above. The results are shown in Table 3.

[0464] [Visibility (color development): Measurement of the change in brightness ΔL before and after exposure] Immediately after exposure and after storing in a dark place (25°C) for 24 hours after exposure, the lithographic printing plate precursor was subjected to irradiation with a Luxel PLATESETTER T-9800 manufactured by Fujifilm Graphic Systems Co., Ltd., equipped with an infrared semiconductor laser with a wavelength of 830 nm, under the following conditions: output 99.5%, external drum rotation speed 220 rpm, resolution 2,400 dpi (dots per inch, 1 inch = 25.4 mm) (energy density 110 mJ / cm 2 The exposure was carried out in an environment of 25°C and 50% RH. The change in brightness of the lithographic printing plate precursor before and after exposure was measured. For the measurement, a spectrophotometer eXact manufactured by X-Rite was used. * a * b * Color space L * The L value (brightness) of the image recording layer after exposure was used. * value and L of the image recording layer before exposure * The absolute value of the difference between the values ​​was taken as the lightness change ΔL. The larger ΔL is, the better the visibility of the exposed area is evaluated to be. The ΔL values ​​obtained using the lithographic printing plate precursor immediately after exposure are shown in the "ΔL (immediately after)" column of Table 3. In addition, the ΔL values ​​obtained using the lithographic printing plate precursor after storage for 24 hours are shown in the "ΔL (after 24 hours)" column of Table 3.

[0465] [Scratch resistance (resistance to scratches and stains)] The obtained lithographic printing plate precursor was exposed to light using a Luxel PLATESETTER T-6000III equipped with an infrared semiconductor laser manufactured by Fujifilm Corp. under conditions of an outer drum rotation speed of 1,000 rpm (revolutions per minute), a laser output of 70%, and a resolution of 2,400 dpi (dots per inch). After exposure, the obtained lithographic printing plate was scratched using a scratch tester in an environment of a temperature of 25° C. and a humidity of 70%. The scratch tester used was a HEIDON scratching intersity TESTER HEIDEN-18, and a scratch load of 50 (g) was used with a sapphire needle of 0.1 mm in diameter. The scratched plate was attached to the plate cylinder of a Mitsubishi Dia IF2 printing press without development processing. Using dampening water of IF102 (manufactured by Fujifilm Corporation) / tap water = 3 / 97 (volume ratio) and Values-G (N) black ink (manufactured by DIC Corporation), dampening water and ink were supplied by the standard automatic printing start method of Dia IF2 to perform on-press development, and then printing was performed using Tokubishi Art Paper (ream weight: 76.5 kg, manufactured by Mitsubishi Paper Mills Co., Ltd.) at a printing speed of 10,000 sheets per hour, and the scratched area was evaluated for print stains. The results are shown in Table 3. In addition, for intermediate points such as 9 points and 7 points, the intermediate points were evaluated when they were between the upper limit evaluation criteria. It is preferable that the evaluation criteria be 10 points to 6 points. -Evaluation criteria- 10 points: The scratched area does not stain the print. 8 points: Slight printing stains that cannot be seen with the naked eye are found in the scratched area. 6 points: Slight stains on the print are visible on the scratched area. 4 points: Print stains are visible on the scratched area. 2 points: Clear printing stains are observed in the scratched area.

[0466] [Table 3]

[0467] Details of the compounds listed in Table 3 other than those mentioned above are shown below. [Color changing compounds] IR-1 to IR-7: Compounds having the following structures

[0468] [ka]

[0469] [ka]

[0470] [Acid color former] S-1: Compound having the following structure S-2: Compound having the following structure

[0471] [ka]

[0472] [Water-soluble polymer] PVA-1: Mowiol 4-88, Mowiol® 4-88 from Sigma Aldrich PVA-2: Mowiol 8-88, Mowiol® 8-88 from Sigma Aldrich WP-1: Compound with the following structure (polyvinylpyrrolidone, weight average molecular weight 45,000)

[0473] [ka]

[0474] [Hydrophobic polymer] P-1: Compound with the following structure (polyvinylidene chloride resin, weight average molecular weight 40,000) P-2: Compound with the following structure (styrene-methyl acrylate copolymer, n=0.3, m=0.7, weight average molecular weight 40,000)

[0475] [ka]

[0476] [Acid Generator] Int-1: A compound having the following structure, where Ph represents a phenyl group.

[0477] [ka]

[0478] [Oil Sensitizer] A-1: Compound having the following structure

[0479] [ka]

[0480] The results shown in Table 3 show that the planographic printing plate precursors of Examples 12 to 22, which are planographic printing plate precursors according to the present disclosure, provide planographic printing plates with excellent printing durability even when UV ink is used. Furthermore, from the results shown in Table 3, the planographic printing plate precursors of Examples 12 to 22, which are planographic printing plate precursors according to the present disclosure, are also excellent in UV plate skip suppression, visibility (color development), visibility over time (color development over time), on-machine developability, on-machine developability over time, and scratch resistance.

[0481] The disclosures of Japanese Patent Application No. 2019-180621, filed on September 30, 2019, and Japanese Patent Application No. 2020-034237, filed on February 28, 2020, are incorporated herein by reference in their entireties. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0482] 18: aluminum plate, ta: anode reaction time, tc: cathode reaction time, tp: time until the current reaches the peak from 0, Ia: current at the peak on the anode cycle side, Ic: current at the peak on the cathode cycle side, AA: current of the anode reaction of the aluminum plate, CA: current of the cathode reaction of the aluminum plate, 10: lithographic printing plate precursor, 12a, 12b: aluminum support, 14: undercoat layer, 16: image recording layer, 20a, 20b: anodized film, 22a, 22b: micropores, 24: large diameter pore portion, 26: Small diameter hole portion, D: depth of large diameter hole portion, 50: main electrolytic cell, 51: AC power source, 52: radial drum roller, 53a, 53b: main electrode, 54: electrolyte supply port, 55: electrolyte, 56: auxiliary anode, 60: auxiliary anode cell, W: aluminum plate, A1: liquid supply direction, A2: electrolyte discharge direction, 610: anodizing treatment device, 612: power supply cell, 614: electrolytic treatment cell, 616: aluminum plate, 618, 26: electrolyte, 620: power supply electrode, 622, 628: roller, 624: nip roller, 630: electrolytic electrode, 632: cell wall, 634: DC power source

Claims

1. A support and an image recording layer on the support, the image recording layer contains an infrared absorbing agent, a polymerization initiator, and a polymer A; The weight average molecular weight of the polymer A is more than 15,000 and not more than 150,000; The ethylenically unsaturated bond valence of the polymer A is 3.0 mmol / g or more, The polymer A has a structure represented by the following formula (A-2): Planographic printing plate original plate. 【Chemistry 1】 In formula (A-2), the wavy line portion represents the bonding position to other structures.

2. The lithographic printing plate precursor according to claim 1 , wherein the polymer A comprises a resin represented by the following formula (I): A Ｐ - (B Ｐ ) ｎＰ Formula (I) In formula (I), A Ｐ represents an organic group having a valence of nP and having a hydrogen-bonding group; B Ｐ represents a group having two or more polymerizable groups, and nP represents an integer of 2 or more.

3. The lithographic printing plate precursor according to claim 1 or 2, wherein the polymer A has at least one structure selected from the group consisting of an adduct structure, a biuret structure, and an isocyanurate structure.

4. B Ｐ The lithographic printing plate precursor according to claim 2 , wherein the polymerizable group comprises a (meth)acryloxy group.

5. B Ｐ The lithographic printing plate precursor according to claim 2 or 4, wherein is a group having three or more (meth)acryloxy groups.

6. The lithographic printing plate precursor according to any one of claims 1 to 5, wherein the image recording layer comprises two or more types of polymer A.

7. The lithographic printing plate precursor according to any one of claims 1 to 6, wherein the image recording layer further comprises a polymerizable compound B having a weight average molecular weight of 1,000 or more and 15,000 or less.

8. 8. The lithographic printing plate according to claim 1, wherein the image recording layer is an outermost layer. Original version.

9. The lithographic printing plate precursor according to any one of claims 1 to 8, wherein the image recording layer further contains polymer particles.

10. The lithographic printing plate precursor according to any one of claims 1 to 9, wherein the polymerization initiator comprises an electron-donating polymerization initiator.

11. The lithographic printing plate precursor according to claim 10, wherein a value of HOMO of the infrared absorber-HOMO of the electron-donating polymerization initiator is 0.70 eV or less.

12. The lithographic printing plate precursor according to any one of claims 1 to 11, wherein the image recording layer further contains a color former.

13. the support is an aluminum support, and has an aluminum plate and an anodized aluminum coating disposed on the aluminum plate; the anodized film is located closer to the image recording layer than the aluminum plate, the anodized coating has micropores extending in a depth direction from a surface on the image recording layer side, the average diameter of the micropores on the surface of the anodized coating is greater than 10 nm and not greater than 100 nm; The L of the surface of the anodized film on the image recording layer side ＊ a ＊ b ＊ Lightness L in color system ＊ is between 70 and 100, the micropores are composed of large-diameter pores extending from the surface of the anodized coating to a depth of 10 nm to 1,000 nm, and small-diameter pores communicating with the bottoms of the large-diameter pores and extending from the communicating positions to a depth of 20 nm to 2,000 nm, the average diameter of the large diameter pores on the surface of the anodized film is 15 nm to 100 nm; The lithographic printing plate precursor according to any one of claims 1 to 12, wherein the small diameter pores have an average diameter of 13 nm or less at the communicating positions.

14. The lithographic printing plate precursor according to any one of claims 1 to 13, further comprising a protective layer on the image recording layer, the protective layer comprising a color-changing compound.

15. The lithographic printing plate precursor according to claim 14, wherein the color-changing compound is a compound represented by the following formula 1-1: 【Chemistry 2】 In formula 1-1, R １ represents a group represented by any one of the following formulas 2 to 4, and R １１ ~R １８ teeth Each independently represents a hydrogen atom, a halogen atom, or -R ａ , -OR ｂ , -SR ｃ , or -NR ｄ R ｅ represents R ａ ~R ｅ each independently represents a hydrocarbon group; A １ , A ２ and multiple R １１ ~R １８ may be linked to form a monocyclic or polycyclic ring, A １ and A ２ each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom; １１ and n １２ Each independently represents an integer of 0 to 5, provided that １１ and n １２ The sum of n is 2 or more, １３ and n １４ each independently represents 0 or 1; L represents an oxygen atom, a sulfur atom, or -NR １０ - represents R １０ represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge. 【Chemistry 3】 In formulas 2 to 4, R ２０ , R ３０ , R ４１ and R ４２ each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents a bonding site with the group represented by L in formula 1-1 above.

16. The content M of the color-changing compound in the protective layer Ｘ and the content M of the infrared absorbing agent in the image recording layer. Ｙ Compared to M Ｘ / M Ｙ The lithographic printing plate precursor according to claim 14 or 15, wherein

17. The lithographic printing plate precursor according to any one of claims 14 to 16, wherein the protective layer comprises a water-soluble polymer and a hydrophobic polymer.

18. A step of imagewise exposing the lithographic printing plate precursor according to any one of claims 1 to 17; and a step of removing the image recording layer in the non-image area by supplying at least one selected from the group consisting of printing ink and dampening water on the printing press. How to make a lithographic printing plate.

19. A step of imagewise exposing the lithographic printing plate precursor according to any one of claims 1 to 17; a step of removing the image recording layer in the non-image area on the printing press by supplying at least one selected from the group consisting of printing ink and dampening water to prepare a lithographic printing plate; and printing with the resulting lithographic printing plate. Lithographic printing method.

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