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

Abstract

The present invention provides an on-press-development-type planographic printing original plate which sequentially comprises a supporting body, an image recording layer and a overcoat layer in this order, wherein: the overcoat layer does not contain an inorganic compound, or alternatively, the content of inorganic compounds is more than 0% by mass but less than 1% by mass relative to the total mass of the overcoat layer; and the image recording layer contains an infrared absorbent, a polymerization initiator, a polymerizable compound and an oil agent. The present invention also provides: a method for producing a planographic printing plate with use of the above-described on-press-development-type planographic printing original plate; and a planographic printing method.

Description

[Technical Field]

[0001] The present disclosure relates to an on-press development type lithographic printing plate precursor, a method for preparing a lithographic printing plate, and a lithographic printing method. [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, with the oleophilic image area of ​​the lithographic printing plate acting as the ink-receptive area and the hydrophilic non-image area acting as the dampening water-receptive area (ink-non-receptive area), creating 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 substrate, such as paper, to produce a print. To prepare such a lithographic printing plate, a lithographic printing plate precursor (PS plate) comprising an oil-sensitive resin layer (image recording layer) provided on a hydrophilic support has hitherto been widely used. Typically, the lithographic printing plate precursor is exposed to light through an original image such as 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 surface of the hydrophilic support to form non-image areas, thereby obtaining a lithographic printing plate.

[0003] Furthermore, with growing concern about the global environment, environmental issues related to wastewater from wet processes such as development processing have come into focus. In response to the above environmental issues, efforts are being made to simplify development or platemaking, or to eliminate processing altogether. One of the simple production methods is a method called "on-press development." In other words, after exposing a lithographic printing plate precursor, the plate is directly mounted on a printing press without undergoing conventional development, and unnecessary portions of the image-recording layer are removed at an early stage of the normal printing process. In the present disclosure, a lithographic printing plate precursor that can be used for such on-press development is referred to as an "on-press development type lithographic printing plate precursor."

[0004] Conventional planographic printing plate precursors include those described in Patent Documents 1 and 2, for example. Patent Document 1 describes a lithographic printing plate precursor having a water-soluble or water-dispersible negative-tone image recording layer on a hydrophilized aluminum support, wherein the arithmetic mean height S a of the overcoat layer surface on the side opposite to the image recording layer is 0.3 μm or more and 20 μm or less, and the image recording layer contains an infrared absorber and thermoplastic polymer particles. Patent Document 2 describes a lithographic printing plate precursor comprising a substrate and an image-forming layer on the substrate, the image-forming layer being removable with either ink or fountain solution, or both ink and fountain solution, wherein the image-forming layer contains (A) at least one radical polymerization initiator and (B) at least one radically polymerizable group, and a radically polymerizable compound having at least one urethane bond and at least two distinct urea bonds, or at least one urea bond and at least two distinct urethane bonds.

[0005] Furthermore, a conventional method for producing a lithographic printing plate is disclosed in, for example, Patent Document 3. Patent Document 3 describes a method for producing a lithographic printing plate, the method comprising, in this order, an exposure step of imagewise exposing a positive lithographic printing plate precursor having an image recording layer on a support, and a development step of developing the exposed positive lithographic printing plate precursor using a developer to form image areas and non-image areas, wherein the image recording layer contains an infrared absorber, and either a polymer A having an acid group and a base group, or both a polymer B having an acid group and a polymer C having a base group, the content of the polymer A or the total content of the polymer B and the polymer C relative to the total mass of the polymers contained in the image recording layer is 10 mass% or more, the pKa of the acid group of the polymer A or the polymer B is 9 or less, and the method does not include a water washing step of washing the developed lithographic printing plate precursor with water after the development step.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-64269 Patent Document 2: Japanese Patent Application Laid-Open No. 2016-155271 Patent Document 3: Japanese Patent Application Laid-Open No. 2020-160348 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of one embodiment of the present disclosure is to provide an on-press development type lithographic printing plate precursor that is excellent in ultraviolet-curable ink (UV ink) printing durability, on-press development property, and suppression of turbidity of fountain solution. Another problem to be solved by another embodiment of the present disclosure is to provide a method for producing a lithographic printing plate or a lithographic printing method using the on-press development type lithographic printing plate precursor. [Means for solving the problem]

[0008] The means for solving the above problems include the following aspects. <1> An on-press development type lithographic printing plate precursor having a support, an image recording layer, and an overcoat layer in this order, wherein the overcoat layer does not contain an inorganic compound or the content of the inorganic compound is more than 0% by mass and less than 1% by mass relative to the total mass of the overcoat layer, and the image recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and an oil agent. <2> The oil agent includes an oil agent having a boiling point of 300°C or higher. <1> 1. An on-press development type lithographic printing plate precursor according to claim 1. <3> The oil agent contains two or more oil agents having different structures. <1> or <2> 1. An on-press development type lithographic printing plate precursor according to claim 1. <4> The clogP value of the above oil agent is 5.0 or more. <1> ~ <3> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <5> The oil agent includes an oil agent having an aromatic ring. <1> ~ <4> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <6> The oil agent includes an oil agent having a phosphorus atom. <1> ~ <5> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <7> The polymerization initiator includes an electron-donating polymerization initiator. <1> ~ <6> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <8> The electron-donating polymerization initiator is a borate compound. <7> 1. An on-press development type lithographic printing plate precursor according to claim 1. <9> the value of HOMO of the infrared absorber - HOMO of the electron-donating polymerization initiator is 0.70 eV or less; <7> or <8> 1. An on-press development type lithographic printing plate precursor according to claim 1. <10> The polymerization initiator contains an electron-accepting polymerization initiator, and the value of LUMO of the electron-accepting polymerization initiator minus LUMO of the infrared absorber is 0.70 eV or less. <1> ~ <9> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <11> The polymerizable compound includes a polymerizable compound having seven or more functional groups. <1> ~ <10> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <12> The polymerizable compound includes a polymerizable compound having 10 or more functional groups. <1> ~ <11> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <13> The image recording layer further contains polymer particles. <1> ~ <12> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <14> The overcoat layer contains a hydrophilic polymer. <1> ~ <13> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <15> The hydrophilic polymer comprises a cellulose derivative. <14> 1. An on-press development type lithographic printing plate precursor according to claim 1. <16> The polymerizable compound includes a difunctional or lower functional polymerizable compound. <1> ~ <15> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <17> The electron-accepting polymerization initiator contains a compound represented by the following formula (II): <10> 1. An on-press development type lithographic printing plate precursor according to claim 1.

[0009] [ka]

[0010] In formula (II), X A represents a halogen atom, and RA represents an aryl group.

[0011] <18> The image recording layer further contains polyvinyl butyral. <1> ~ <17> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <19> The overcoat layer comprises a hydrophobic polymer. <1> ~ <18> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <20> The hydrophobic polymer is a hydrophobic polymer particle. <19> 1. An on-press development type lithographic printing plate precursor according to claim 1. <21> The overcoat layer further contains a color-changing compound. <1> ~ <20> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <22> The color-changing compound includes a decomposable compound that decomposes due to exposure to infrared light. <21> 1. An on-press development type lithographic printing plate precursor according to claim 1. <23> The color-changing compound is a cyanine dye. <21> or <22> 1. An on-press development type lithographic printing plate precursor according to claim 1. <24> The color-changing compound is a compound represented by the following formula 1-1: <21> ~ <23> 10. An on-press development type lithographic printing plate precursor according to any one of the above items.

[0012] [ka]

[0013] In formula 1-1, R 1 represents a group represented by any one of the following formulas 2-1 to 4-1, 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 represents R a ~R e each independently represents a hydrocarbon group, and A1, A2 and a plurality of R 11 ~R 18may be linked to form a monocycle or polycycle, 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 2-1 to 4-1, 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 the bonding site with the group represented by L in the above formula 1-1.

[0016] <25> The color-changing compound is a compound represented by the following formula 1-2: <21> ~ <24> 10. An on-press development type lithographic printing plate precursor according to any one of the above items.

[0017] [ka]

[0018] 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 represents R 23and R 24 are each independently a hydrogen atom or -R a represents 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 that neutralizes the charge.

[0019] <26> The color-changing compound is a compound represented by any one of the following formulas 1-3 to 1-7: <21> ~ <25> 10. An on-press development type lithographic printing plate precursor according to any one of the above items.

[0020] [ka]

[0021] In formulas 1-3 to 1-7, R 1 represents a group represented by any one of the above formulas 2-1 to 4-1, 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 represents R 25 and R 26 are each independently a hydrogen atom, a halogen atom, or -R a represents R a ~R e each independently represents a hydrocarbon group, R 19 and R 20 , R 21 and R22 , 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. <27> W in the above formulas 1-2 to 1-7 1 and W 2 are each independently an alkyl group having a substituent, and are groups having at least one of -OCH2CH2-, a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group as the substituent. <25> or <26> 1. An on-press development type lithographic printing plate precursor according to claim 1.

[0022] <28> <1> ~ <27> and a step of 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. <29> <1> ~ <27> a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of the above items 1 to 5; 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; and a step of printing with the obtained lithographic printing plate. [Effects of the Invention]

[0023] According to one embodiment of the present disclosure, it is possible to provide an on-press development type lithographic printing plate precursor that is excellent in UV ink printing durability, on-press developability, and ability to inhibit turbidity of fountain solution. According to another embodiment of the present disclosure, it is possible to provide a method for producing a lithographic printing plate or a lithographic printing method using the on-press development type lithographic printing plate precursor. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic cross-sectional view of one embodiment of an aluminum support that can be suitably used in the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view of one embodiment of an aluminum support having an anodized coating. [Figure 3] FIG. 1 is a schematic view of an anodizing treatment apparatus used in an anodizing treatment in a method for producing an aluminum support having an anodized coating. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. Furthermore, in the description of groups (atomic groups) in this specification, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used as a concept that includes both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept that includes both acryloyl and methacryloyl. Furthermore, the term "step" in this specification does not only refer to an independent step, but also includes a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Furthermore, in this disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Unless otherwise specified, each component in a composition or each structural unit in a polymer in the present disclosure may be contained alone or in combination of two or more types. Furthermore, in the present disclosure, the amount of each component in a composition or each structural unit in a polymer means, unless otherwise specified, the total amount of the corresponding multiple substances present in the composition or the corresponding multiple structural units present in the polymer, when multiple substances or structural units corresponding to each component or each structural unit in the polymer are present in the composition. Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in the present disclosure are molecular weights determined by gel permeation chromatography (GPC) using columns of TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation), detection with a differential refractometer using THF (tetrahydrofuran) as a solvent, and conversion using polystyrene as a standard substance. In the present disclosure, the term "lithographic printing plate precursor" encompasses not only lithographic printing plate precursors but also throwaway plate precursors. Furthermore, the term "lithographic printing plate" encompasses 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 throwaway plate precursors, the operations of exposure and development are not necessarily required. A throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when, for example, printing a portion of a page in a single color or two colors in color newspaper printing. In this disclosure, "excellent printing durability" refers to a large number of printable sheets of a lithographic printing plate, and printing durability when ultraviolet-curable ink (UV ink) is used as the ink for printing will hereinafter also be referred to as "UV ink printing durability" or simply "UV printing durability." The present disclosure will be described in detail below.

[0026] (On-press development type lithographic printing plate original plate) The on-press development type lithographic printing plate precursor (also simply referred to as "lithographic printing plate precursor") according to the present disclosure has a support, an image recording layer, and an overcoat layer in this order, wherein the overcoat layer does not contain an inorganic compound or the content of the inorganic compound is more than 0% by mass and less than 1% by mass relative to the total mass of the overcoat layer, and the image recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and an oil agent. Furthermore, the on-press development type lithographic printing plate precursor according to the present disclosure may be either a negative working lithographic printing plate precursor or a positive working lithographic printing plate precursor, but is preferably a negative working lithographic printing plate precursor.

[0027] The present inventors have found that conventional on-press development type lithographic printing plate precursors may be insufficient in at least one of UV ink printing durability, on-press development property, and suppression of turbidity of fountain solution. As a result of extensive research, the present inventors have found that by adopting the above-mentioned configuration, it is possible to provide an on-press development type lithographic printing plate precursor that is excellent in UV ink printing durability, on-press developability, and suppression of turbidity of fountain solution. The detailed mechanism by which the above effects are obtained is unknown, but is speculated as follows. It is estimated that if the overcoat layer does not contain any inorganic compounds or the content of inorganic compounds is more than 0% by mass and less than 1% by mass relative to the total mass of the overcoat layer, and the image recording layer contains an oil agent, it is possible to suppress turbidity of the dampening water due to the inorganic compounds in the overcoat layer, and the oil agent can make the image recording layer more hydrophobic, thereby suppressing dissolution and dispersion of the image recording layer and its components in the dampening water.It is also estimated that the inclusion of the oil agent maintains the hydrophobicity of the image recording layer, while the plasticizing effect improves the permeability of the dampening water into the image recording layer, thereby imparting high UV ink printing durability and excellent on-press developability. Hereinafter, each constituent element of the planographic printing plate precursor according to the present disclosure will be described in detail.

[0028] <Image recording layer> The lithographic printing plate precursor according to the present disclosure has a support, an image recording layer, and an overcoat layer in this order, and the image recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and an oil agent.

[0029] [Oil agent] The image recording layer contains an oil agent. The oil agent in this disclosure refers to a hydrophobic compound that is in a liquid state at 80°C and is immiscible and separates when mixed with the same mass of water. When two or more oil agents are used, even if a compound with a melting point of 80°C or higher is included, it is sufficient that the two or more oil agents are in a liquid state at 80°C when mixed. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the dampening water, the oil agent is preferably a compound having a molecular weight of less than 1,000, more preferably a compound having a molecular weight of 200 to 800, and particularly preferably a compound having a molecular weight of 300 to 500. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the dampening water, the oil agent is preferably a compound having a boiling point of 200°C or higher at 1 atmosphere, more preferably a compound having a boiling point of 250°C or higher at 1 atmosphere, even more preferably a compound having a boiling point of 300°C or higher at 1 atmosphere, and particularly preferably a compound having a boiling point of 400°C or higher and 500°C or lower at 1 atmosphere. In this disclosure, unless otherwise specified, the term "boiling point" refers to the boiling point at 1 atmosphere. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the dampening water, the melting point of the oil agent at 1 atmosphere is preferably 50°C or lower, more preferably 30°C or lower, and particularly preferably −200°C or higher and 25°C or lower. In this disclosure, unless otherwise specified, the term "melting point" refers to the melting point at 1 atmosphere.

[0030] Examples of the oil agent include phosphate ester compounds, aromatic hydrocarbon compounds, glyceride compounds, fatty acid compounds, and aromatic ester compounds. Among these, from the viewpoints of UV printing durability, ink receptivity, on-press developability, and suppression of turbidity in dampening water, at least one compound selected from the group consisting of phosphate ester compounds, aromatic hydrocarbon compounds, glyceride compounds, and aromatic ester compounds is preferred, at least one compound selected from the group consisting of phosphate ester compounds, aromatic hydrocarbon compounds, and glyceride compounds is more preferred, at least one compound selected from the group consisting of phosphate ester compounds and aromatic hydrocarbon compounds is even more preferred, and a phosphate ester compound is particularly preferred.

[0031] As the phosphate ester compound, from the viewpoints of UV printing durability, ink receptivity, on-press developability, and suppression of turbidity in fountain solution, a phosphate triester compound is preferred, a phosphate triaryl ester compound is more preferred, tricresyl phosphate is even more preferred, and a mixture of two or more of the ortho-, meta-, and para-tricresyl phosphate is particularly preferred. As the aromatic hydrocarbon compound, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, a compound having two or more aromatic rings is preferred, and a compound having two or more non-fused benzene rings is more preferred. As the glyceride compound, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, a triglyceride compound is preferred, a fatty oil is more preferred, and a fatty oil that is liquid at 25°C, such as castor oil, is particularly preferred. As the fatty acid compound, from the viewpoint of on-press developability and suppression of turbidity of the fountain solution, unsaturated fatty acids are preferred, unsaturated fatty acids having 8 to 30 carbon atoms are more preferred, and unsaturated fatty acids having 12 to 24 carbon atoms are particularly preferred. As the aromatic ester compound, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, aromatic diester compounds are preferred, and aromatic diester compounds having an aliphatic ring are more preferred. As the aliphatic ester compound, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, an aliphatic ester compound having a branched alkyl group is preferred, and an aliphatic ester compound having a branched alkyl group and 10 to 24 carbon atoms is more preferred.

[0032] From the viewpoints of UV printing durability, ink receptivity, on-press developability, and suppression of turbidity of dampening water, the oil agent preferably contains an oil agent having a phosphorus atom, and more preferably is an oil agent having a phosphorus atom. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the dampening water, the oil agent preferably contains an oil agent having an aromatic ring, more preferably contains an oil agent having two or more aromatic rings, and particularly preferably contains an oil agent having two or more non-fused benzene rings.

[0033] From the viewpoints of UV printing durability, ink receptivity, on-press developability, and suppression of turbidity of dampening water, the clogP value of the oil agent is preferably 5.0 or more, more preferably 5.50 or more, even more preferably 5.50 or more and 10.0 or less, and particularly preferably 5.60 or more and 7.00 or less. The clogP value is a value obtained by calculating the common logarithm logP of the partition coefficient P between 1-octanol and water. Although publicly known methods and software can be used to calculate the clogP value, unless otherwise specified, the present disclosure will use the ClogP program incorporated into Cambridge Soft's ChemBioDraw Ultra 12.0.

[0034] Specific examples of the oil agent include tricresyl phosphate, dimethyl(1-phenylethyl)benzene, 2,4-diphenyl-4-methyl-1-pentene, dicyclohexyl phthalate, castor oil, α-linolenic acid, and tri(2-ethylhexyl) phosphate.

[0035] The oil agent may be used alone or in combination of two or more types. However, from the viewpoints of on-press developability and suppression of turbidity of the dampening water, it is preferable that the image recording layer contains two or more types of oil agents having different structures. The content of the oil agent is preferably 0.0001% by mass to 10.0% by mass, more preferably 0.0002% by mass to 1.0% by mass, even more preferably 0.0005% by mass to 0.5% by mass, and particularly preferably 0.001% by mass to 0.05% by mass, relative to the total mass of the image recording layer.

[0036] [Infrared absorber] The image recording layer in the present disclosure 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 Synthetic Chemistry Society, published in 1970) can be used. Specific examples 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.

[0037] Among these dyes, preferred are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. More preferred are cyanine dyes and indolenine cyanine dyes. Of these, cyanine dyes are particularly preferred.

[0038] The infrared absorber is preferably a cationic polymethine dye having an oxygen atom, a nitrogen atom, or a halogen atom at the meso position. Preferred examples of the cationic polymethine dye include cyanine dyes, pyrylium dyes, thiopyrylium dyes, and azulenium dyes. From the viewpoints of availability, solvent solubility during the introduction reaction, and the like, cyanine dyes are preferred.

[0039] Specific examples of cyanine dyes include the compounds described in paragraphs

[0017] to

[0019] of JP-A No. 2001-133969, the compounds described in paragraphs

[0016] to

[0021] of JP-A No. 2002-023360, and the compounds described in paragraphs

[0012] to

[0037] of JP-A No. 2002-040638, preferably the compounds described in paragraphs

[0034] to

[0041] of JP-A No. 2002-278057, and paragraphs

[0080] to

[0086] of JP-A No. 2008-195018, and particularly preferably the compounds described in paragraphs

[0035] to

[0043] of JP-A No. 2007-90850, and the compounds described in paragraphs

[0105] to

[0113] of JP-A No. 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.

[0040] Furthermore, as the infrared absorbing agent, a decomposable compound that decomposes due to exposure to infrared light, which will be described later as a discoloring compound in the overcoat layer, is also suitably used.

[0041] From the viewpoints of printing durability and visibility, the highest occupied molecular orbital (HOMO) of the infrared absorber is preferably −5.250 eV or less, more preferably −5.30 eV or less, even more preferably −5.80 eV or more and −5.35 eV or less, and particularly preferably −5.65 eV or more and −5.40 eV or less.

[0042] From the viewpoints of stability over time, improved sensitivity, and UV printing durability, the lowest unoccupied molecular orbital (LUMO) of the infrared absorber is preferably smaller than −3.70 eV, more preferably smaller than −3.80 eV, even more preferably at least −4.20 eV but less than −3.80 eV, and particularly preferably at least −4.00 eV but less than −3.80 eV.

[0043] The infrared absorber may be used alone or in combination of two or more kinds. However, from the viewpoints of UV printing durability, on-press developability, and suppression of turbidity of the dampening water, the image recording layer preferably contains two or more kinds of infrared absorbers, more preferably two to four kinds, and particularly preferably two kinds. Furthermore, a pigment and a dye may be used in combination as the infrared absorbing agent.

[0044] The content of the infrared absorbing agent is preferably 0.1% by mass to 10.0% by mass, and more preferably 0.5% by mass to 5.0% by mass, based on the total mass of the image recording layer.

[0045] [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-donating polymerization initiator, and more preferably contains an electron-accepting polymerization initiator and an electron-donating polymerization initiator. From the viewpoints of visibility of the exposed area and tone reproducibility, the image recording layer preferably further contains a polymerization initiator, and the decomposition product upon exposure is a decomposition product of the polymerization initiator upon exposure, and more preferably contains an electron-donating polymerization initiator, and the decomposition product upon exposure is a decomposition product of the electron-donating polymerization initiator upon exposure.

[0046] [Electron-donating polymerization initiator (polymerization aid)] The image recording layer in the lithographic printing plate precursor according to the present disclosure preferably further contains an electron-donating polymerization initiator (also referred to as a "polymerization aid") as a polymerization initiator. The electron-donating polymerization initiator is a compound that, when an electron of an infrared absorber is excited or moves intramolecularly upon exposure to infrared light, donates one electron to an orbital of the infrared absorber that has lost one electron 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.

[0047] From the viewpoints of visibility of the exposed area and tone reproducibility, the electron-donating polymerization initiator preferably contains a boron compound, more preferably contains a borate compound, further preferably contains a tetraarylborate compound, and particularly preferably contains a tetraphenylborate compound. From the viewpoints of printing durability and visibility, the borate compound is preferably a tetraarylborate compound or a monoalkyltriarylborate compound, and more preferably a tetraarylborate compound. Furthermore, from the viewpoints of printing durability and visibility, the borate compound is preferably a tetraarylborate compound having one or more electron-donating groups or electron-withdrawing groups, and more preferably a tetraarylborate compound having one electron-donating group or electron-withdrawing group in each aryl group. From the viewpoints of printing durability and visibility, the electron-donating group is preferably an alkyl group or an alkoxy group, and more preferably an alkoxy group. From the viewpoints of decomposability and visibility, examples of the electron-withdrawing group include a halogen atom, a halogenated alkyl group, an acyl group, and a carboxy group. 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. The counter cation of the borate compound may be a cationic polymethine dye in the infrared absorber described herein. For example, the borate compound may be used as a counter cation of a cyanine dye.

[0048] A specific example of the borate salt compound is sodium tetraphenylborate.

[0049] 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.

[0050] [ka]

[0051] Furthermore, from the viewpoint of improving sensitivity, the highest occupied molecular orbital (HOMO) of the electron-donating polymerization initiator is preferably −6.00 eV or more, more preferably −5.95 eV or more, even more preferably −5.93 eV or more, and particularly preferably greater than −5.90 eV. The upper limit is preferably −5.00 eV or less, and more preferably −5.40 eV or less.

[0052] The electron-donating polymerization initiator may be used alone or in combination of two or more kinds.

[0053] 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. Furthermore, from the viewpoint of UV printing durability, the content of the electron-donating polymerization initiator in the image recording layer is preferably greater than the content of the infrared absorber, more preferably 1.1 to 5 times the content of the infrared absorber, and particularly preferably 1.5 to 3 times the content of the infrared absorber.

[0054] In the present disclosure, the polymerization initiator may be a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form a counter salt. For example, in the present disclosure, a compound in which an anion in an electron-donating polymerization initiator and a cation in an electron-accepting polymerization initiator form a counter salt is preferred, a compound in which an onium cation and a borate anion form a counter salt is more preferred, a compound in which an iodonium cation or a sulfonium cation and a borate anion form a counter salt is even more preferred, and a compound in which a diaryliodonium cation or a triarylsulfonium cation and a tetraarylborate anion form a counter salt is particularly preferred. Preferred embodiments of the anion in the electron-donating polymerization initiator and the cation in the electron-accepting polymerization initiator are the same as the preferred embodiments of the anion in the electron-donating polymerization initiator and the cation in the electron-accepting polymerization initiator described above. When the image recording layer contains an anion that is an electron-donating polymerization initiator and a cation that is an electron-accepting polymerization initiator (i.e., when it contains a compound that forms the above-mentioned counter salt), the image recording layer is considered to contain an electron-accepting polymerization initiator and the above-mentioned electron-donating polymerization initiator. Furthermore, a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form a counter salt may be used as either an electron-donating polymerization initiator or an electron-accepting polymerization initiator. Furthermore, a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form a counter salt may be used in combination with the above-mentioned electron-donating polymerization initiator, or may be used in combination with the above-mentioned electron-accepting polymerization initiator.

[0055] The image recording layer in the present disclosure further contains an infrared absorber and an electron-donating polymerization initiator, and from the viewpoint of improving sensitivity and printing durability, the value of the HOMO of the infrared absorber minus the HOMO of the electron-donating polymerization initiator is preferably 0.70 eV or less, more preferably 0.60 eV or less, even more preferably 0.50 eV or less, and particularly preferably 0.50 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.

[0056] In the present disclosure, the MO (molecular orbital) energy calculations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are performed by the following method. First, free counter ions in the target compound are excluded from the calculation. For example, counter anions are excluded from the calculation for cationic one-electron-accepting polymerization agents and cationic infrared absorbers, and counter cations are excluded from the calculation for anionic one-electron-donating polymerization agents. "Free" here means that the target compound and its counter ion are not linked by a covalent bond. The quantum chemical calculation software Gaussian 16 is used, and structural optimization is performed using DFT (B3LYP / 6-31G(d)). MO energy calculations are performed using the quantum chemistry calculation software Gaussian 16 with the optimal structure obtained by the above structural optimization, using DFT (B3LYP / 6-31+G(d,p) / PCM(solvent=methanol)). Note that for compounds containing iodine, calculations are performed under DFT (B3LYP / DGDZVP / PCM(solvent=methanol)). The optimal structure here refers to the structure with the most stable total energy obtained from DFT calculations. The most stable structure can be found by repeating structural optimization as necessary. The MO energy Ebare (unit: hartree) obtained in the above MO energy calculation is converted to Escaled (unit: eV) which is used as the HOMO and LUMO values ​​in this disclosure using the following formula: [HOMO calculation formula] Escaled=0.823168×27.2114×Ebare-1.07634 [LUMO calculation formula] Escaled=0.820139×27.2114×Ebare-1.086039 Note that 27.2114 is simply a coefficient used to convert hartrees to eV, and the 0.823168 and -1.07634 used when calculating the HOMO, and the 0.820139 and -1.086039 used when calculating the UMO are adjustment coefficients determined so that the calculated HOMO and LUMO of the target compound match the measured values.

[0057] [Electron-accepting polymerization initiator] The image recording layer in the present disclosure preferably further contains an electron-accepting polymerization initiator as a polymerization initiator. The electron-accepting polymerization initiator is a compound that generates polymerization initiating species such as radicals by accepting one electron through intermolecular electron transfer when electrons in the infrared absorber are excited by exposure to infrared light. The electron-accepting polymerization initiator is a compound that generates polymerization initiating species such as radicals and cations 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 preferred, and an onium salt compound is more preferred. The electron-accepting polymerization initiator is preferably an infrared-sensitive polymerization initiator. Furthermore, from the viewpoint of improving sensitivity and UV printing durability, the electron-accepting polymerization initiator is preferably an iodonium salt compound or a compound having a halogenated alkyl group, and more preferably a compound having a halogenated alkyl group. Furthermore, as the compound having a halogenated alkyl group, from the viewpoint of improving sensitivity and UV printing durability, a compound having a perhalogenoalkylsulfonyl group is preferred, a compound having a trihalogenomethylsulfonyl group is more preferred, and a compound having a tribromomethylsulfonyl group is particularly preferred.

[0058] Among the electron-accepting polymerization initiators, preferred are oxime ester compounds and onium salt compounds from the viewpoint of curability. Among them, preferred are iodonium salt compounds, sulfonium salt compounds, and azinium salt compounds from the viewpoint of printing durability, more preferred are iodonium salt compounds or 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.

[0059] Preferred examples of iodonium salt compounds include diaryliodonium salt compounds, and 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 (4-t-butylphenyl)iodonium hexafluorophosphate.

[0060] Examples of counter anions of the iodonium salt compounds and sulfonium salt compounds 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. Of these, sulfonamide anions or sulfonimide anions are preferred, and sulfonimide anions are more preferred. The sulfonamide anion is preferably an arylsulfonamide anion. The sulfonimide anion is preferably a bisarylsulfonimide anion. It's nice. Specific examples of sulfonamide anions or sulfonimide anions include those described in WO 2019 / 013268.

[0061] Furthermore, 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):

[0062] [ka]

[0063] 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.

[0064] R in formula (II) A is 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, an aryl group substituted with an amide group is more preferred from the viewpoint of achieving an excellent balance between sensitivity and storage stability.

[0065] Furthermore, it is particularly preferable that the electron-accepting polymerization initiator contains a compound represented by formula (IV).

[0066] [ka]

[0067] In formula (IV), X A represents a halogen atom, and R A3 and RA4 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.

[0068] Specific examples of the electron-accepting polymerization initiator include the compounds shown below, but the present disclosure is not limited to these.

[0069] [ka]

[0070] [ka]

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] [ka]

[0075] [ka]

[0076] The lowest unoccupied molecular orbital (LUMO) of the electron-accepting polymerization initiator is preferably −3.00 eV or less, more preferably −3.02 eV or less, from the viewpoint of improving sensitivity. The lower limit is preferably −3.80 eV or more, and more preferably −3.50 eV or more.

[0077] The electron-accepting polymerization initiator may be used alone or in combination of two or more kinds.

[0078] 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, relative to the total mass of the image recording layer.

[0079] The image recording layer in the present disclosure further contains an infrared absorber and an electron-accepting polymerization initiator, and from the viewpoint of improving sensitivity and printing durability, the value of LUMO of the electron-accepting polymerization initiator minus LUMO of the infrared absorber is preferably 1.00 eV or less, more preferably 0.80 eV or less, even more preferably 0.70 eV or less, particularly preferably 0.70 eV to −0.10 eV or less, and most preferably 0.70 eV to 0.30 eV. A negative value means that the LUMO of the infrared absorber is higher than the LUMO of the electron-accepting polymerization initiator.

[0080] [Polymerizable compound] The image recording layer in the present disclosure contains a polymerizable compound. In the present disclosure, a polymerizable compound refers to a compound having a polymerizable group. The polymerizable group is not particularly limited as long as it is a known polymerizable group, but is preferably an ethylenically unsaturated group. The polymerizable group may be either a radically polymerizable group or a cationically polymerizable group, but is preferably a radically polymerizable group. Examples of the radically polymerizable group include a (meth)acryloyl group, an allyl group, a vinylphenyl group, and a vinyl group, and from the viewpoint of reactivity, a (meth)acryloyl group is preferred. The molecular weight of the polymerizable compound (weight average molecular weight when the polymerizable compound has a molecular weight distribution) is preferably 50 or more and less than 2,500.

[0081] The polymerizable compound used in the present disclosure may be, for example, a radically polymerizable compound or a cationically polymerizable compound, but is preferably an addition-polymerizable compound (ethylenically unsaturated compound) having at least one ethylenically unsaturated bond. The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, more preferably a compound having two or more terminal ethylenically unsaturated bonds. The polymerizable compound has a chemical form such as a monomer, a prepolymer, i.e., a dimer, a trimer, or an oligomer, or a mixture thereof. Among these, from the viewpoint of UV printing durability, the polymerizable compound preferably contains a trifunctional or higher polymerizable compound, more preferably a heptafunctional or higher polymerizable compound, and even more preferably a decafunctional or higher polymerizable compound. Furthermore, from the viewpoint of UV printing durability of the resulting lithographic printing plate, the polymerizable compound preferably contains a trifunctional or higher (preferably heptafunctional or higher, more preferably decafunctional or higher) ethylenically unsaturated compound, and even more preferably a trifunctional or higher (preferably heptafunctional or higher, more preferably decafunctional or higher) (meth)acrylate compound.

[0082] Furthermore, from the viewpoints of on-press developability and stain suppression, the polymerizable compound preferably contains a polymerizable compound having two or fewer functionalities, more preferably a bifunctional polymerizable compound, and particularly preferably a bifunctional (meth)acrylate compound. From the viewpoints of printing durability, on-press developability, and stain suppression, the content of the difunctional or less polymerizable compound (preferably a difunctional polymerizable compound) is preferably 5% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, and particularly preferably 50% by mass to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0083] <<Oligomer>> The polymerizable compound contained in the image recording layer preferably contains a polymerizable compound that is an oligomer (hereinafter also simply referred to as "oligomer"). In the present disclosure, an oligomer refers to a polymerizable compound having a molecular weight (weight average molecular weight when the molecular weight has a molecular weight distribution) of 600 or more and 10,000 or less and containing at least one polymerizable group. From the viewpoint of excellent chemical resistance and UV printing resistance, the molecular weight of the oligomer is preferably 1,000 or more and 5,000 or less.

[0084] Furthermore, from the viewpoint of improving UV printing durability, the number of polymerizable groups in one oligomer molecule is preferably 2 or more, more preferably 3 or more, even more preferably 6 or more, and particularly preferably 10 or more. There is no particular upper limit to the number of polymerizable groups in the oligomer, but the number of polymerizable groups is preferably 20 or less.

[0085] From the viewpoints of UV printing durability and on-press developability, the oligomer preferably has 7 or more polymerizable groups and a molecular weight of 1,000 or more and 10,000 or less, and more preferably has 7 or more polymerizable groups and a molecular weight of 1,000 or more and 5,000 or less. The oligomer may contain polymer components that may be generated during the process of producing the oligomer.

[0086] From the viewpoints of UV printing durability, visibility, and on-press developability, the oligomer preferably contains at least one selected from the group consisting of a compound having a urethane bond, a compound having an ester bond, and a compound having an epoxy residue, and more preferably contains a compound having a urethane bond. In the present disclosure, the epoxy residue refers to a structure formed by an epoxy group, and means, for example, a structure similar to the structure obtained by the reaction of an acid group (such as a carboxylic acid group) with an epoxy group.

[0087] The compound having a urethane bond, which is an example of an oligomer, is preferably, for example, 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).

[0088] [ka]

[0089] 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. 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 even more preferably an alkylene group having 4 to 8 carbon atoms. The alkylene group may have a branched or cyclic structure, but is preferably a linear alkylene group.

[0090] It is preferred that the wavy line portions in formula (Ac-1) or formula (Ac-2) are each independently directly bonded to the wavy line portions in the groups represented by formula (Ae-1) or formula (Ae-2) below.

[0091] [ka]

[0092] 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).

[0093] Furthermore, as the compound having a urethane bond, a compound obtained by introducing a polymerizable group into polyurethane obtained by a reaction between a polyisocyanate compound and a polyol compound through a polymer reaction may be used. For example, a compound having a urethane bond may be obtained by reacting a polyurethane oligomer obtained by reacting a polyol compound having an acid group with a polyisocyanate compound, with a compound having an epoxy group and a polymerizable group.

[0094] The number of polymerizable groups in the compound having an ester bond, which is an example of an oligomer, is preferably 3 or more, and more preferably 6 or more.

[0095] As a compound having an epoxy residue, which is an example of an oligomer, a compound containing a hydroxy group within the compound is preferred. The compound having an epoxy residue preferably has 2 to 6 polymerizable groups, and more preferably has 2 to 3 polymerizable groups. The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

[0096] Specific examples of oligomers are shown in the table below, but the oligomers used in the present disclosure are not limited to these. As the oligomer, commercially available products may be used, and examples thereof include UA510H, UA-306H, UA-306I, UA-306T (all manufactured by Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, UV7620EA (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), U-15HA (manufactured by Shin-Nakamura Chemical Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, EBECRYL860 (all manufactured by Daicel Allnex Corporation), but are not limited thereto.

[0097] From the viewpoint of improving chemical resistance, UV printing durability, and suppression of on-press development residue, the content of the oligomer is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0098] <<Low molecular polymerizable compounds>> The polymerizable compound may further contain a polymerizable compound other than the above-mentioned oligomer. From the viewpoint of chemical resistance, the polymerizable compound other than the oligomer is preferably a low molecular weight polymerizable compound, which may be in any chemical form such as a monomer, a dimer, a trimer, or a mixture thereof. Furthermore, from the viewpoint of chemical resistance, the low molecular weight polymerizable compound is preferably at least one polymerizable compound selected from the group consisting of polymerizable compounds having three or more ethylenically unsaturated groups and polymerizable compounds having an isocyanuric ring structure.

[0099] In the present disclosure, a low molecular weight polymerizable compound refers to a polymerizable compound having a molecular weight (weight average molecular weight when the compound has a molecular weight distribution) of 50 or more and less than 600. The molecular weight of the low-molecular-weight polymerizable compound is preferably 100 or more and less than 600, more preferably 300 or more and less than 600, and even more preferably 400 or more and less than 600, from the viewpoint of excellent chemical resistance, UV printing durability, and on-press development residue suppression.

[0100] When the polymerizable compound contains a low-molecular-weight polymerizable compound as a polymerizable compound other than an oligomer (when two or more types of low-molecular-weight polymerizable compounds are contained, the total amount of the low-molecular-weight polymerizable compounds), from the viewpoints of chemical resistance, UV printing durability, and suppression of on-press development residue, the ratio of the oligomer to the low-molecular-weight polymerizable compound (oligomer / low-molecular-weight polymerizable compound) is preferably 10 / 1 to 1 / 10, more preferably 10 / 1 to 3 / 7, and even more preferably 10 / 1 to 7 / 3, by mass.

[0101] Furthermore, as the low molecular weight polymerizable compound, the polymerizable compounds described in paragraphs 0082 to 0086 of WO 2019 / 013268 can also be suitably used.

[0102] Details of the method of use such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount added can be set arbitrarily. In particular, from the viewpoint of UV printing durability, the image recording layer preferably contains two or more polymerizable compounds. The content of the polymerizable compounds (when two or more polymerizable compounds are contained, the total content of the polymerizable compounds) is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 70% by mass, and even more preferably 15% by mass to 60% by mass, relative to the total mass of the image recording layer.

[0103] 〔particle〕 From the viewpoints of developability and UV printing durability, the image recording layer of the present disclosure preferably further contains particles. The particles may be inorganic particles or organic particles. Among these, it is preferable that the particles contain organic particles, and it is more preferable that the particles contain resin particles (polymer particles). As the inorganic particles, known inorganic particles can be used, and metal oxide particles such as silica particles and titania particles can be suitably used.

[0104] <<Resin particles>> Examples of resin particles include particles containing an addition polymerization type resin (i.e., addition polymerization type resin particles), particles containing a polyaddition type resin (i.e., polyaddition type resin particles), and particles containing a polycondensation type resin (i.e., polycondensation type resin particles). Among these, addition polymerization type resin particles and polyaddition type resin particles are preferred. Furthermore, the resin particles may be particles containing a thermoplastic resin (that is, thermoplastic resin particles) from the viewpoint of enabling thermal fusion.

[0105] The resin particles may also be in the form of microcapsules, microgels (ie, crosslinked resin particles), or the like.

[0106] The resin particles are preferably selected from the group consisting of thermoplastic resin particles, thermoreactive resin particles, resin particles having a polymerizable group, microcapsules encapsulating a hydrophobic compound, and microgels (crosslinked resin particles). Among these, resin particles having a polymerizable group are preferred. In a particularly preferred embodiment, the resin particles contain at least one ethylenically unsaturated group. The presence of such resin particles has the effect of improving the printing durability of exposed areas and the on-press developability of unexposed areas.

[0107] Preferred thermoplastic resin particles are 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, etc.

[0108] Specific examples of resins constituting the thermoplastic resin 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, and acrylates or methacrylates having a polyalkylene structure, or mixtures thereof.

[0109] From the viewpoint of ink receptivity and UV printing durability, the thermoplastic resin particles preferably contain a resin having a structural unit formed from an aromatic vinyl compound and a structural unit having a nitrile group.

[0110] 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.

[0111] From the viewpoint of ink receptivity, the content of the structural unit formed by the aromatic vinyl compound is preferably greater than the content of the structural unit having a nitrile group, which will be described later, and is more preferably 15% by mass to 85% by mass, and even more preferably 30% by mass to 70% by mass, relative to the total mass of the resin.

[0112] The structural unit having a nitrile group is preferably introduced using a monomer having a nitrile group. Examples of the monomer having a nitrile group include acrylonitrile compounds, and (meth)acrylonitrile is preferred. As a structural unit having a nitrile group, a structural unit formed from (meth)acrylonitrile is preferred.

[0113] From the viewpoint of ink receptivity, the content of the structural unit having a nitrile group is preferably less than the content of the structural unit formed from the aromatic vinyl compound, and is more preferably 55% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, relative to the total mass of the resin.

[0114] Furthermore, when the resin contained in the thermoplastic resin particles contains a structural unit formed by an aromatic vinyl compound and a structural unit having a nitrile group, the content ratio of the structural unit formed by the aromatic vinyl compound to the structural unit having a nitrile group (structural unit formed by the aromatic vinyl compound:structural unit having a nitrile group) is preferably 5:5 to 9:1, more preferably 6:4 to 8:2, by mass.

[0115] From the viewpoint of UV printing durability and chemical resistance, it is preferable that the resin contained in the thermoplastic resin particles further have a structural unit formed from an N-vinyl heterocyclic compound. Examples of N-vinyl heterocyclic compounds include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylimidazole, with N-vinylpyrrolidone being preferred.

[0116] The content of the structural unit formed by the N-vinyl heterocyclic compound is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 40% by mass, relative to the total mass of the thermoplastic resin.

[0117] The resin contained in the thermoplastic resin particles may contain a structural unit having an acidic group, but from the viewpoint of on-press developability and ink receptivity, it is preferable that the resin does not contain a structural unit having an acidic group. Specifically, the content of structural units having an acidic group in the thermoplastic resin is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The lower limit of the content is not particularly limited, and may be 0% by mass. The acid value of the thermoplastic resin is preferably 160 mgKOH / g or less, more preferably 80 mgKOH / g or less, and even more preferably 40 mgKOH / g or less. The lower limit of the acid value is not particularly limited, and may be 0 mgKOH / g. In the present disclosure, the acid value is determined by a measurement method in accordance with JIS K0070:1992.

[0118] From the viewpoint of ink receptivity, the resin contained in the thermoplastic resin particles may contain a structural unit containing a hydrophobic group. Examples of the hydrophobic group include an alkyl group, an aryl group, and an aralkyl group. As the structural unit containing a hydrophobic group, a structural unit formed from an alkyl(meth)acrylate compound, an aryl(meth)acrylate compound, or an aralkyl(meth)acrylate compound is preferred, and a structural unit formed from an alkyl(meth)acrylate compound is more preferred.

[0119] The content of structural units having a hydrophobic group in the resin contained in the thermoplastic resin particles is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the resin.

[0120] The thermoplastic resin contained in the thermoplastic resin particles preferably has a hydrophilic group from the viewpoints of UV printing durability and on-press developability. The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include acid groups such as a carboxy group, a hydroxy group, an amino group, a nitrile group, and a polyalkylene oxide structure. From the viewpoints of UV printing durability and on-press developability, the hydrophilic group is preferably a group having a polyalkylene oxide structure, a group having a polyester structure, or a sulfonic acid group, more preferably a group having a polyalkylene oxide structure or a sulfonic acid group, and even more preferably a group having a polyalkylene oxide structure.

[0121] From the viewpoint of on-press developability, the polyalkylene oxide structure is preferably a polyethylene oxide structure, a polypropylene oxide structure, or a poly(ethylene oxide / propylene oxide) structure. From the viewpoint of on-press developability, the hydrophilic group preferably has a polypropylene oxide structure as the polyalkylene oxide structure, and more preferably has a polyethylene oxide structure or a polypropylene oxide structure. The number of alkylene oxide structures in the polyalkylene oxide structure is preferably 2 or more, more preferably 5 or more, further preferably 5 to 200, and particularly preferably 8 to 150, from the viewpoint of on-press developability.

[0122] From the viewpoint of on-press developability, the hydrophilic group is preferably a group represented by the formula Z described below. Among the hydrophilic groups contained in the thermoplastic resin, groups represented by the following formula PO are preferred.

[0123] [ka]

[0124] During the expression PO, L P each independently represents an alkylene group; R P represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 100. During the expression PO, L P are each independently preferably an ethylene group, a 1-methylethylene group or a 2-methylethylene group, more preferably an ethylene group. In the formula PO, R P is preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, even more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom or a methyl group. In the formula PO, n is preferably an integer of 1 to 10, and more preferably an integer of 1 to 4.

[0125] The content of the structural unit having a hydrophilic group is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the resin.

[0126] The resin contained in the thermoplastic resin particles may further contain other structural units. The other structural units may contain structural units other than the above-mentioned structural units without any particular limitation, and examples thereof include structural units formed from an acrylamide compound, a vinyl ether compound, etc.

[0127] The content of other structural units in the resin contained in the thermoplastic resin particles is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the resin.

[0128] The heat-reactive resin particles include resin particles having heat-reactive groups, which form hydrophobic regions due to crosslinking caused by a thermal reaction and the resulting change in functional groups.

[0129] The thermally reactive group in the resin particles having a thermally reactive group may be any 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.), cationically polymerizable groups (e.g., vinyl groups, vinyloxy groups, epoxy groups, oxetanyl groups, etc.), isocyanato groups that undergo addition reactions or their block products, 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 that undergo condensation reactions and their reaction partners, hydroxy groups or amino groups, and acid anhydrides that undergo ring-opening addition reactions and their reaction partners, amino groups or hydroxy groups. The resin having the thermally reactive group may be an addition polymerization type resin, a polyaddition type resin, or a polycondensation type resin, or may be a thermoplastic resin.

[0130] As the microcapsules, those which encapsulate at least a part of the components of the image recording layer (preferably a hydrophobic compound) are preferred, as described in, for example, JP-A Nos. 2001-277740 and 2001-277742. In a preferred embodiment, the image recording layer containing microcapsules as resin particles has a hydrophobic component (i.e., a hydrophobic compound) among the components of the image recording layer encapsulated in the microcapsules and a hydrophilic component (i.e., a hydrophilic compound) contained outside the microcapsules. The microgel (crosslinked resin particle) can contain some of the components of the image recording layer on at least one of its surface and interior. In particular, a reactive microgel having a polymerizable group on its surface is preferred from the viewpoints of the sensitivity of the lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate. To obtain microcapsules containing the components of the image recording layer, known synthesis methods can be applied.

[0131] The microgel (crosslinked resin particle) can contain some of the components of the image recording layer on at least one of its surface and interior. In particular, a reactive microgel having a polymerizable group on its surface is preferred from the viewpoints of the sensitivity of the lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate. In order to obtain a microgel containing the components of the image recording layer, known synthesis methods can be applied.

[0132] From the viewpoint of the printing durability, stain resistance, and storage stability of the resulting lithographic printing plate, preferred resin particles are polyaddition type resin particles obtained by the reaction of a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in the molecule with isophorone diisocyanate, and 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. Furthermore, water can be used as the active hydrogen compound. When water is used, the amine generated by the reaction of the isocyanato group with water forms a urea bond, thereby forming particles. Preferred examples of resin particles obtained by reacting a polyvalent isocyanate compound, which is an adduct of a polyhydric phenol compound having two or more hydroxy groups in the molecule with isophorone diisocyanate, with a compound having active hydrogen include the resin particles described in paragraphs 0230 to 0234 of WO2018043259.

[0133] Furthermore, from the viewpoint of the printing durability and solvent resistance of the resulting lithographic printing plate, addition polymerization type resin particles having a hydrophobic main chain and including both i) a constituent unit having a nitrile group directly bonded to the hydrophobic main chain and ii) a constituent unit having a pendant group containing a hydrophilic polyalkylene oxide segment are preferred. Specifically, the particles described in paragraph 0156 of JP-A-2019-64269 are preferred.

[0134] <<Group represented by formula Z>> The resin particles in the present disclosure preferably have a group represented by the following formula Z as a hydrophilic group. *-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 to another structure. In addition, it is preferable that any of the hydrophilic structures contained in formula Z contains a polyalkylene oxide structure.

[0135] 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.

[0136] The divalent group having a hydrophilic structure in W of the above formula Z is preferably a group containing a polyalkylene oxide structure, and is preferably a polyalkyleneoxy group or a group having -CH2CH2NR at one end of the polyalkyleneoxy group. 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 6 to 120 carbon atoms (a divalent group obtained by removing one hydrogen atom from an alkylaryl group), or an aralkylene group having 6 to 120 carbon atoms.

[0137] 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 Among them, the monovalent group having a hydrophilic structure is preferably a group containing a polyalkylene oxide structure, and is preferably 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 having —CHCHN(R W )-bonded groups are preferred. The monovalent group having a hydrophobic structure represented by 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 6 to 120 carbon atoms, an aralkyl group having 6 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.

[0138] From the viewpoints of printing durability, ink receptivity, and on-press developability, it is more preferable that the resin particles having a group represented by the above formula Z are such that 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. The group represented by formula Z may function as a dispersing group that enhances the dispersibility of the resin particles.

[0139] From the viewpoints of printing durability and on-press developability, the resin particles in the present disclosure preferably have a polymerizable group (preferably an ethylenically unsaturated group), and more preferably contain resin particles having a polymerizable group on the surface. By using resin particles having a polymerizable group, printing durability (preferably UV printing durability) can be improved.

[0140] From the viewpoint of printing durability, the resin particles in the present disclosure are preferably resin particles having a hydrophilic group and a polymerizable group. The polymerizable group may be a cationically polymerizable group or a radically polymerizable group, but 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. Furthermore, the resin constituting the resin particles having a polymerizable group preferably has a structural unit having a polymerizable group. Incidentally, polymerizable groups may be introduced onto the surfaces of the resin particles by a polymer reaction.

[0141] Furthermore, from the viewpoints of printing durability, ink receptivity, on-press developability, and suppression of development residue during on-press development, the resin particles preferably contain a polyaddition resin having a urea bond, more preferably a polyaddition resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water, and particularly preferably a polyaddition 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. Furthermore, the particles containing the polyaddition resin having a urea bond are preferably microgels.

[0142] [ka]

[0143] In formula (Iso), n represents an integer of 0 to 10.

[0144] 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, some of the isocyanate groups are hydrolyzed by the water to generate amino groups, which then react with the isocyanate groups to form urea bonds and form dimers. Furthermore, the following reaction is repeated to form a polyaddition resin having urea bonds.

[0145] Furthermore, in the reaction described below, by adding a compound (compound having active hydrogen) reactive with an isocyanate group, such as an alcohol compound or an amine compound, the structure of the alcohol compound, amine compound, or the like can be introduced into a polyaddition resin having a urea bond. Preferred examples of the compound having active hydrogen include the compounds having active hydrogen already described.

[0146] [ka]

[0147] The polyaddition resin having a urea bond preferably has an ethylenically unsaturated group, and more preferably has a group represented by the following formula (PETA).

[0148] [ka]

[0149] In formula (PETA), the wavy line indicates the bonding position to other structures.

[0150] <<Synthesis of resin particles>> The method for synthesizing the resin particles is not particularly limited, and any method capable of synthesizing particles from the various resins described above may be used. Examples of the method for synthesizing the resin particles include known methods for synthesizing resin particles, such as emulsion polymerization, suspension polymerization, dispersion polymerization, soap-free polymerization, and microemulsion polymerization. Alternatively, known methods for synthesizing microcapsules, methods for synthesizing microgels (crosslinked resin particles), etc. may be used to synthesize the resin particles.

[0151] <<Average particle size>> The average particle size of the particles is preferably 0.01 μm to 3.0 μm, more preferably 0.03 μm to 2.0 μm, and even more preferably 0.10 μm to 1.0 μm. Within this range, good resolution and stability over time can be obtained. The average particle size of particles is measured by the light scattering method, or by taking an electron microscope photograph of the particles, measuring the particle size of a total of 5,000 particles on the photograph, and calculating the average. For non-spherical particles, the equivalent circle diameter of the particle on the photograph is used. In the present disclosure, the average particle size of particles is the volume average particle size unless otherwise specified.

[0152] The particles (preferably resin particles) may be used alone or in combination of two or more kinds.

[0153] From the viewpoints of developability and printing durability, the content of particles (preferably resin particles) 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.

[0154] [Other ingredients] The image recording layer in the present disclosure may contain components other than those already described. Examples of other components include binder polymers, color formers, color formers, chain transfer agents, low molecular weight hydrophilic compounds, oil sensitizers, and other additives.

[0155] Other components include colorants, printing-out agents, polymerization inhibitors, higher fatty acid derivatives, plasticizers, inorganic particles, and low-molecular-weight hydrophilic compounds, as disclosed in paragraphs 0181 to 0190 of JP-A No. 2009-255434. Other compounds include hydrophobic precursors (fine particles that can convert the image recording layer to a hydrophobic state when heat is applied), low-molecular-weight hydrophilic compounds, oil-sensitizing agents (for example, phosphonium compounds, nitrogen-containing low-molecular-weight compounds, and ammonium group-containing polymers), and chain transfer agents, all of which are disclosed in paragraphs 0191 to 0217 of JP2012-187907A.

[0156] -Binder polymer- The image recording layer may contain a binder polymer, if necessary. Here, the binder polymer refers to a polymer other than resin particles, that is, a polymer that is not in particle form. The binder polymer does not include ammonium salt-containing polymers in oil sensitizers and polymers used as surfactants.

[0157] As the binder polymer, known binder polymers (such as (meth)acrylic resins, polyvinyl acetal, polyurethane resins, etc.) used in the image recording layer of a lithographic printing plate precursor can be suitably used. 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 a side chain. Alternatively, 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 contains a poly(alkylene oxide) moiety, a polyurethane resin is preferred. Examples of the main chain polymer having a poly(alkylene oxide) moiety in the side chain include (meth)acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, polystyrene resin, novolac phenolic resin, polyester resin, synthetic rubber, and natural rubber, with (meth)acrylic resin being particularly preferred.

[0158] 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, polymer chains bonded to the core via sulfide bonds, and the polymer chains having polymerizable groups. As the star-shaped polymer compound, for example, the compounds described in JP-A-2012-148555 can be preferably used.

[0159] 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 in the star-shaped polymer compound forms crosslinks between molecules of the star-shaped polymer compound, accelerating curing. As the polymerizable group, an ethylenically unsaturated group such as a (meth)acrylic group, a vinyl group, an allyl group, or a vinylphenyl group (styryl group), an epoxy group, or the like is preferred, with a (meth)acrylic group, a vinyl group, or a vinylphenyl group (styryl group) being more preferred from the viewpoint of polymerization reactivity, and a (meth)acrylic group being particularly preferred. These groups can be introduced into a polymer by a polymer reaction or copolymerization. Specifically, for example, a reaction between a polymer having a carboxy group in the side chain and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be utilized.

[0160] 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 even more preferably 10,000 to 300,000, as calculated as polystyrene by the GPC method.

[0161] As the binder polymer, hydrophilic polymers such as polyacrylic acid, polyvinyl alcohol, and polyvinyl acetal described in JP-A-2008-195018 can be used in combination, if necessary. Also, a lipophilic polymer and a hydrophilic polymer can be used in combination. Among these, from the viewpoint of on-press developability, the image recording layer preferably contains polyvinyl acetal. Suitable examples of polyvinyl acetal include polyvinyl butyral.

[0162] The binder polymer may be used alone or in combination of two or more kinds.

[0163] The binder polymer can be contained in any amount in the image recording layer, but the content of the binder polymer is preferably 1% by mass to 90% by mass, and more preferably 5% by mass to 80% by mass, relative to the total mass of the image recording layer.

[0164] -Color former- The image recording layer of the present disclosure preferably further contains a color former, more preferably an acid color former, and preferably contains a leuco compound as the color former. As used herein, the term "color former" refers to a compound that develops or loses color 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" refers to a compound that develops or loses color when heated in a state in which it has accepted an electron-accepting compound (e.g., a proton from an acid, etc.). Preferred acid color formers are colorless compounds that have a partial skeleton such as a lactone, lactam, sultone, spiropyran, ester, or amide, and that rapidly open or cleave this partial skeleton when they come into contact with an electron-accepting compound.

[0165] Examples of such acid color formers include the compounds described in paragraphs 0184 to 0191 of JP-A-2019-18412.

[0166] Among these, from the viewpoint of visibility, 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 color of the dye after color development preferably has a maximum absorption in the range of 450 to 650 nm, and the color is preferably red, purple, blue, or black-green.

[0167] In addition, the acid color former is preferably a leuco dye from the viewpoint of visibility and visibility of exposed areas. The leuco dye is not particularly limited as long as it has a leuco structure, but preferably has a spiro structure, and more preferably has a spirolactone ring structure. Furthermore, from the viewpoint of visibility and visibility of exposed areas, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure. Furthermore, from the viewpoint of visibility and visibility of exposed areas, the leuco dye having the phthalide structure or the 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).

[0168] [ka]

[0169] 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, and X5 to X 10 each independently represent 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; 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, an aryl group, or a heteroaryl group.

[0170] From the viewpoints of color development and visibility of exposed areas, 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 heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group; more preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, or an aryloxy group; still more preferably a monoalkylmonoarylamino group, a diarylamino group, a diheteroarylamino group, or a monoarylmonoheteroarylamino group; and particularly preferably a monoalkylmonoarylamino group. Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group in the above-mentioned ERG is preferably a di-substituted amino group having an aryl group having a substituent at at least one ortho-position or a heteroaryl group having a substituent at at least one ortho-position, more preferably a di-substituted amino group having a phenyl group having a substituent at at least one ortho-position and an electron-donating group at the para-position, still more preferably an amino group having a phenyl group having a substituent at at least one ortho-position and an electron-donating group at the para-position and an aryl group or a heteroaryl group, and particularly preferably an amino group having a phenyl group having a substituent at at least one ortho-position and an electron-donating group at the para-position and an aryl group having an electron-donating group or a heteroaryl group having an electron-donating group. In the present disclosure, the ortho position in an aryl group or heteroaryl group other than a phenyl group refers to the bonding position adjacent to the bonding position 1 (e.g., 2nd position, etc.) of the aryl group or heteroaryl group to another structure, where the bonding position is 1st position. Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group contained in the aryl group or heteroaryl group is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

[0171] In the formulae (Le-1) to (Le-3), X1 to X4 are each independently preferably a hydrogen atom or a chlorine atom, more preferably a hydrogen atom, from the viewpoint of color development and visibility of exposed areas. X5 to X in formula (Le-2) or formula (Le-3) 10 are each independently, from the viewpoints of color development and visibility of exposed areas, preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, or a cyano group, 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 terms of color development and visibility of exposed areas, at least one of Y1 and Y2 in formulae (Le-1) to (Le-3) is preferably C, and both Y1 and Y2 are preferably 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 are each independently preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, and particularly preferably a methyl group, from the viewpoints of color development and visibility of exposed areas.

[0172] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having the phthalide structure or the 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).

[0173] [ka]

[0174] In formulas (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, provided that 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, an aryl group, or a heteroaryl group.

[0175] ERG, X1 to X4, Y1, Y2, Ra1, and Rb1 to Rb4 in formulae (Le-4) to (Le-6) 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.

[0176] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having the phthalide structure or the 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).

[0177] [ka]

[0178] In formulas (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 is not present; when Y2 is N, X4 is not present; 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, an aryl group, or a heteroaryl group; and Rc1 and Rc2 each independently represent an aryl group or a heteroaryl group.

[0179] 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 terms of color development and visibility of exposed areas, Ra1 to Ra4 in formula (Le-7) or formula (Le-9) 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 exposed areas. In formulae (Le-7) to (Le-9), Rb1 to Rb4 are each independently preferably a hydrogen atom, or an aryl group substituted with an alkyl group or an alkoxy group, more preferably an alkyl group, and particularly preferably a methyl group, from the viewpoints of color development and visibility of exposed areas. In formula (Le-8), Rc1 and Rc2 are each independently preferably a phenyl group or an alkylphenyl group, more preferably a phenyl group, from the viewpoint of color development and visibility of exposed areas. Furthermore, in terms of color development and visibility of exposed areas, Rc1 and Rc2 in formula (Le-8) are each independently preferably an aryl group having a substituent at at least one ortho position or a heteroaryl group having a substituent at at least one ortho position, more preferably an aryl group having a substituent at at least one ortho position, even more preferably a phenyl group having a substituent at at least one ortho position, and particularly preferably a phenyl group having a substituent at at least one ortho position and an electron-donating group at the para position. Examples of the substituents in Rc1 and Rc2 include the substituents described below. In addition, in formula (Le-8), from the viewpoint 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 viewpoint of color development and visibility of exposed areas, it is preferred that Rb1 and Rb2 each independently represent an aryl group substituted with an alkyl group or an alkoxy group. Furthermore, in formula (Le-8), from the viewpoints of color development and visibility of exposed areas, Rb1 and Rb2 are each preferably independently an aryl group or a heteroaryl group, more preferably an aryl group, still more preferably an aryl group having an electron-donating group, and particularly preferably a phenyl group having an electron-donating group at the para position. Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group in Rb1, Rb2, Rc1, and Rc2 is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

[0180] Moreover, from the viewpoint of color development and visibility of exposed areas, it is preferable that the acid color former contains a compound represented by the following formula (Le-10).

[0181] [ka]

[0182] In formula (Le-10), each Ar1 independently represents an aryl group or a heteroaryl group, and each Ar2 independently represents an aryl group having a substituent at at least one ortho-position, or a heteroaryl group having a substituent at at least one ortho-position.

[0183] Ar1 in formula (Le-10) has the same meaning as Rb1 and Rb2 in formulae (Le-7) to (Le-9), and preferred embodiments are also the same. Ar2 in formula (Le-10) has the same meaning as Rc1 and Rc2 in formulae (Le-7) to (Le-9), and preferred embodiments are also the same.

[0184] The alkyl group in formulae (Le-1) to (Le-9) may be linear, branched, or have a ring structure. The alkyl group in formulae (Le-1) to (Le-9) preferably has 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, even more preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. The aryl group in formulae (Le-1) to (Le-10) preferably has 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms, and particularly preferably 6 to 8 carbon atoms. Specific examples of the aryl group in formulae (Le-1) to (Le-10) include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group, each of which may have a substituent. Specific examples of the heteroaryl group in formulae (Le-1) to (Le-10) include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group, each of which may have a substituent.

[0185] Furthermore, each of the monovalent organic groups, alkyl groups, aryl groups, heteroaryl groups, dialkylanilino groups, alkylamino groups, alkoxy groups, etc. in Formulae (Le-1) to (Le-10) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, and a cyano group. Furthermore, these substituents may be further substituted with other substituents.

[0186] Suitable leuco dyes having a phthalide structure or a fluoran structure include the following compounds:

[0187] [ka]

[0188] [ka]

[0189] [ka]

[0190] [ka]

[0191] [ka]

[0192] [ka]

[0193] [ka]

[0194] [ka]

[0195] 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, and H-2114 (all manufactured by Fukui Yamada Chemical Co., Ltd.), ORANGE-DCF, and Vermilio. Examples of such dyes include n-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF, and 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, and Red-8 (all manufactured by Yamamoto Chemical Industries, Ltd.), and crystal violet lactone (manufactured by Tokyo Chemical Industry 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 absorptivity.

[0196] As leuco dyes that are preferably used, the following compounds can be mentioned from the viewpoints of visibility and visibility of exposed areas.

[0197] [ka]

[0198] These color formers may be used alone or in combination of two or more components. The content of the color former is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass, based on the total mass of the image recording layer.

[0199] -Color-forming compound- In the on-press development type lithographic printing plate precursor according to the present disclosure, the image recording layer preferably contains a color former capable of undergoing a color reaction with a decomposition product generated by exposure of the image recording layer. In the present disclosure, a "color reaction" refers to a chemical reaction that involves the phenomenon of color development or color change. The decomposition product generated by exposure of the image recording layer is not particularly limited, but from the viewpoint of visibility of the exposed area, it is preferably a decomposition product of a polymerization initiator generated by exposure or a decomposition product of an infrared absorber generated by exposure, more preferably a decomposition product of a polymerization initiator generated by exposure, and particularly preferably a decomposition product of an electron-donating polymerization initiator generated by exposure. The decomposition products generated by exposure of the image recording layer include not only decomposition products formed by decomposition of the image recording layer by exposure, but also compounds generated by further decomposition or modification of the decomposition products. From the viewpoint of visibility of the exposed area, the color reaction is preferably a complex formation reaction, and more preferably a boron complex formation reaction.

[0200] An example of the color reaction is shown below. The following shows the color reaction when curcumin is used as the color former and sodium tetraphenylborate decomposes to produce boric acid as a decomposition product produced by exposure of the image recording layer. Curcumin generates an enol form in equilibrium due to keto-enol tautomerism. The reaction of the enol form with boric acid produces the following boron complex, which causes a color reaction from curcumin (yellow) to the following boron complex (red). Although the following shows an example in which the compound was hydrolyzed to boric acid, for example, a complex may be formed between curcumin and diphenylmonohydroxyboron, monophenyldihydroxyboron, etc., or triphenylboron may coordinate to enol-type curcumin as a zero-valent ligand to form a complex.

[0201] [ka]

[0202] From the viewpoints of visibility of exposed areas and tone reproducibility, the color-forming compound is preferably a compound having one or more ketone structures, more preferably a compound having one or more 1,3-diketone structures, β-hydroxyketone structures, or β-aminoketone structures, even more preferably a compound having one or more 1,3-diketone structures or β-hydroxyketone structures, and particularly preferably a compound having one or more 1,3-diketone structures. The color former also includes compounds having one or more 1-hydroxy-3-amino structures or 1-hydroxy-3-imino structures. Furthermore, from the viewpoints of visibility of exposed areas and tone reproducibility, the color-forming compound is preferably a compound having an aromatic ring structure, more preferably a compound having two or more aromatic ring structures, even more preferably a compound having two to four aromatic ring structures, and particularly preferably a compound having two aromatic ring structures. As the aromatic ring structure, from the viewpoints of visibility of exposed areas and tone reproducibility, at least one selected from the group consisting of a benzene ring structure and a naphthalene ring structure is preferred, and a benzene ring structure is more preferred. The color former may be a salt or a hydrate. Furthermore, when the color former reacts with decomposition products generated by exposure of the image recording layer to form a complex, the complex may be a monodentate or polydentate ligand. From the viewpoints of complex formation, visibility of the exposed area, and tone reproducibility, the complex is preferably a polydentate ligand, more preferably a bidentate to hexadentate ligand, even more preferably a bidentate to tetradentate ligand, particularly preferably a bidentate or tridentate ligand, and most preferably a bidentate ligand.

[0203] From the viewpoints of visibility of exposed areas and tone reproducibility, the on-press development type lithographic printing plate precursor according to the present disclosure preferably contains a compound represented by the following formula 1C or formula 2C as the color former, and more preferably contains a compound represented by the following formula 1C: Furthermore, in the on-press developable lithographic printing plate precursor according to the present disclosure, after exposure, it is preferred that a compound represented by the following formula 1C or 2C reacts with a decomposition product resulting from exposure of the image recording layer to form a complex having the compound represented by the following formula 1C or 2C as a zerovalent ligand or an anion obtained by removing one hydrogen atom from the compound represented by the following formula 1C or 2C as a monovalent ligand, and it is more preferred that a compound represented by the following formula 1C or 2C reacts with a decomposition product resulting from exposure of the image recording layer to form a complex having the anion obtained by removing one hydrogen atom from the compound represented by the following formula 1C or 2C as a monovalent ligand.

[0204] [ka]

[0205] In Formula 1C and Formula 2C, R 1C ~R 4C each independently represents a monovalent organic group; L1C and L 2C each independently represents a divalent organic group; A C is OH or NR 5C R 6C represents R 5C and R 6C each independently represents a hydrogen atom or a monovalent organic group, and the dotted line represents a moiety which may be a double bond.

[0206] In Formula 1C, R 1C , L 1C , and R 2C Two or more of these may be bonded to form a ring structure. In Formula 2C, R 3C , L 2C , R 4C , R 5C , and R 6C Two or more of these may be bonded to form a ring structure. R in Equation 1C 1C and R 2C are each independently, from the viewpoints of visibility of exposed areas and tone reproducibility, preferably a monovalent organic group having an aromatic ring, more preferably an aryl group or an alkenyl group having an aryl group, and particularly preferably a 2-arylvinyl group. The aryl group may have a substituent. From the viewpoint of visibility of exposed areas and tone reproducibility, the aryl group is preferably an aryl group having, as a substituent, one or more groups selected from the group consisting of hydroxy groups and alkoxy groups, more preferably a phenyl group having, as a substituent, one or more groups selected from the group consisting of hydroxy groups and alkoxy groups, and particularly preferably a phenyl group having, as a substituent, a hydroxy group and an alkoxy group. Furthermore, R in Formula 1C 1C and R 2C The carbon number (number of carbon atoms) of each is independently preferably 6 to 50, more preferably 6 to 20, and particularly preferably 8 to 20. Also, R in Formula 1C 1C and R 2C are preferably the same group. L in Equation 1C 1C From the viewpoints of visibility of exposed areas and tone reproducibility, is preferably an alkylene group or an alkylene group having an acyloxy group, and more preferably a methylene group or an acyloxymethylene group. Furthermore, from the viewpoint of visibility of exposed areas, the acyloxy group is preferably an acyloxy group having 1 to 10 carbon atoms, more preferably an acyloxy group having 1 to 4 carbon atoms, and particularly preferably an acetoxy group.

[0207] R in Equation 2C 3C From the viewpoints of visibility of exposed areas and tone reproducibility, is preferably a monovalent organic group having an aromatic ring, and more preferably an aryl group or an alkenyl group having an aryl group. In Equation 2C, from the viewpoint of visibility of the exposed area and tone reproducibility, L 2C and R 4C and preferably bond to form an aromatic ring, and L 2C and R 4C and more preferably bond to form a benzene ring. Also, R in Equation 2C 3C and R 4C The number of carbon atoms in each of the groups is preferably 6 to 50, more preferably 6 to 30, and particularly preferably 6 to 20. L in Equation 2C 2C is R 4C When the compound is not bonded to the compound, from the viewpoints of visibility of the exposed area and tone reproducibility, the compound is preferably an alkylene group or an alkylene group having an acyloxy group, and more preferably a methylene group or an acyloxymethylene group. Furthermore, from the viewpoint of visibility of exposed areas, the acyloxy group is preferably an acyloxy group having 1 to 10 carbon atoms, more preferably an acyloxy group having 1 to 4 carbon atoms, and particularly preferably an acetoxy group. Also, L in Equation 2C 2C is R 4Cand preferably bonds to form a ring member of an aromatic ring structure. From the viewpoints of visibility of exposed areas and tone reproducibility, the compound represented by Formula 2C is preferably a compound having a 1-hydroxyanthraquinone structure or a 1-aminoanthraquinone structure, and more preferably a compound having a 1-hydroxyanthraquinone structure. A in Equation 2C C From the viewpoint of visibility of exposed areas and tone reproduction, OH or NHR 6C is preferred, and OH is more preferred. NR in Equation 2C 5C R 6C R in 5C is preferably a hydrogen atom, an alkyl group, or an aryl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom. NR in Equation 2C 5C R 6C R in 6C is preferably a hydrogen atom, an alkyl group, or an anthraquinolyl group, more preferably an anthraquinolyl group, and particularly preferably a 1-anthraquinolyl group.

[0208] Specific examples of the color-developing compound include curcumin (C-1, which will be described later in the Examples), demethoxycurcumin (C-2, which will be described later in the Examples), alizarin (C-3, which will be described later in the Examples), iminodianthraquinone (C-4, which will be described later in the Examples), carminic acid (C-5, which will be described later in the Examples), azomethine H (C-6, which will be described later in the Examples), 1,3-bis(4-methoxyphenyl)-1,3-propanedione (C-7, which will be described later in the Examples), 4-methoxychalcone (C-8, which will be described later in the Examples), 1,3-bis(4-dimethylaminophenyl)-1,3-propanedione (C-9, which will be described later in the Examples), and acetoxycurcumin (C-10, which will be described later in the Examples).

[0209] The color formers may be used alone or in combination of two or more. The compounds represented by the above formula 1C or 2C may be used alone or in combination of two or more. Furthermore, only one type of the above complex may be formed, or two or more types may be formed. From the viewpoints of visibility of exposed areas and tone reproducibility, the content of the color-forming compound is preferably 0.001% by mass to 5% by mass, more preferably 0.01% by mass to 3% by mass, even more preferably 0.05% by mass to 2.5% by mass, and particularly preferably 0.05% by mass to 1.0% by mass, relative to the total mass of the image recording layer.

[0210] The content M of the color former (preferably the compound represented by Formula 1 or Formula 2) in the image recording layer C and the content M of the polymerization initiator described below. I The molar ratio of M C / M I =0.001 to 1, and M C / M I More preferably, M = 0.01 to 0.8. C / M I It is particularly preferable that .gtoreq.0.05 to 0.5. Furthermore, the molybdenum content M of the color former (preferably the compound represented by Formula 1 or Formula 2) in the image recording layer is C and the content M of the electron-donating polymerization initiator described below. DI The molar ratio of M C / M DI =0.001 to 1.5, and M C / M DI More preferably, M = 0.01 to 1. C / M DI It is particularly preferable that .gtoreq.0.05 to 0.8.

[0211] [Formation of Image Recording Layer] The image recording layer in the lithographic printing plate precursor according to the present disclosure can be formed by dispersing or dissolving the necessary components in a known solvent to prepare a coating solution, applying the coating solution to a support by a known method such as bar coater coating, and drying, as described in paragraphs

[0142] and

[0143] of JP-A No. 2008-195018, for example. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but is generally 0.3 g / m 2 ~3.0g / m 2 Within this range, good sensitivity and good film properties of the image recording layer can be obtained. As the solvent, known solvents can be used, specifically, for example, water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3-methoxy-1-propanol, 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, ethyl lactate, etc. The solvent may be used alone or in combination of two or more. The solid content concentration in the coating liquid is preferably 1% by mass to 50% by mass. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer, it is 0.3 g / m 2 ~3.0g / m2 is preferred. Furthermore, the film thickness of the image recording layer in the lithographic printing plate precursor according to the present disclosure is preferably 0.1 μm to 3.0 μm, and more preferably 0.3 μm to 2.0 μm. In the present disclosure, the film thickness of each layer in the lithographic printing plate precursor is confirmed by preparing a slice cut in a direction perpendicular to the surface of the lithographic printing plate precursor and observing the cross section of the slice with a scanning electron microscope (SEM).

[0212] <Overcoat layer> The on-press development type lithographic printing plate precursor according to the present disclosure has a support, an image recording layer, and an overcoat layer in this order, and the overcoat layer does not contain any inorganic compound, or the content of the inorganic compound is more than 0% by mass and less than 1% by mass relative to the total mass of the overcoat layer. From the viewpoints of on-press developability and suppression of turbidity of the dampening water, it is preferable that the overcoat layer does not contain any inorganic compounds, or that the content of inorganic compounds is more than 0% by mass and less than 0.5% by mass relative to the total mass of the overcoat layer, and it is more preferable that the overcoat layer does not contain any inorganic compounds. From the viewpoint of visibility, the overcoat layer preferably contains a color-changing compound. The overcoat layer is an overcoat layer on the image recording layer side of the support in an on-press development type lithographic printing plate precursor. The overcoat layer may have functions such as preventing scratches on the image recording layer and abrasion during exposure to high-intensity laser light, in addition to the function of inhibiting image formation by blocking oxygen.

[0213] -Color-changing compounds- The overcoat layer preferably contains a color-changing compound. The overcoat layer may contain, in addition to the color-changing compound, other components such as a water-soluble polymer, a hydrophobic polymer, an oil-sensitizing agent, an acid generator, and an infrared absorber. It is preferable that the overcoat layer contains a color-changing compound and a water-soluble polymer, and it is more preferable that the overcoat layer contains a color-changing compound, a water-soluble polymer, and a hydrophobic polymer.

[0214] In the present disclosure, a "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 increases upon exposure to infrared light, and (3) compounds whose absorption in the visible light region disappears upon exposure to infrared light. Infrared rays in the present disclosure are rays with a wavelength of 750 nm to 1 mm, and preferably rays with a wavelength of 750 nm to 1,400 nm.

[0215] The color-changing compound preferably includes a compound that develops color upon exposure to infrared light. Furthermore, 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, "decomposition 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. The color-changing compound is preferably a cyanine dye from the viewpoint of improving the visibility of the exposed area.

[0216] 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 light to generate a compound having a maximum absorption wavelength in the wavelength range of 500 nm to 600 nm.

[0217] 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.

[0218] [ka]

[0219] In formula 1-1, R 1 represents a group represented by any one of the following formulas 2-1 to 4-1, 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 represents 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 monocycle or polycycle, 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 12The 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.

[0220] [ka]

[0221] In formulas 2-1 to 4-1, 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 the bonding site with the group represented by L in the above formula 1-1.

[0222] When exposed to infrared light, the compound of formula 1-1 reacts with R 1 The -L bond is cleaved and L is =O, =S, or =NR 10 and discoloration occurs.

[0223] In Formula 1-1, R 1 represents a group represented by any one of the above formulas 2-1 to 4-1. The group represented by formula 2-1, the group represented by formula 3-1, and the group represented by formula 4-1 will be explained below.

[0224] In formula 2-1, R 20 represents an alkyl group or an aryl group, and the wavy line portion represents the bonding site to the group represented by L in formula 1-1. R 20 The 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 even more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a ring structure. R 20The aryl group represented by the formula (I) 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 visibility, the group is preferably an alkyl group.

[0225] In addition, from the viewpoint of decomposability and visibility, 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 visibility, 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, and is particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0226] Specific examples of the group represented by formula 2-1 above are listed below, but the present disclosure is not limited to these. In the following structural formula, ● represents the bonding site with the group represented by L in formula 1-1.

[0227] [ka]

[0228] In formula 3-1, R 30 represents an alkyl group or an aryl group, and the wavy line portion represents the bonding site to the group represented by L in formula 1-1. R 30 The alkyl group and aryl group represented by the formula 2-1 are 20 The same applies to the alkyl and aryl groups represented by the following formula (1), and the preferred embodiments are also the same.

[0229] From the viewpoint of decomposability and visibility, R 30The 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 visibility, 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, and is particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group. Furthermore, from the viewpoint of decomposability and visibility, 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.

[0230] From the viewpoint of decomposability and visibility, R 30 The aryl group represented by the 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).

[0231] Specific examples of the group represented by formula 3-1 above are listed below, but the present disclosure is not limited to these. In the following structural formula, ● represents the bonding site with the group represented by L in formula 1-1.

[0232] [ka]

[0233] In formula 4-1, 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 portion represents the bonding site with the group represented by L in formula 1-1. R 41 or R 42 The alkyl group and aryl group represented by the formula 20The same applies to the alkyl and aryl groups represented by the following formula (1), and the preferred embodiments are also the same. R 41 From the viewpoints of decomposability and visibility, the group is preferably an alkyl group. R 42 From the viewpoints of decomposability and visibility, the group is preferably an alkyl group.

[0234] From the viewpoint of decomposability and visibility, 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 visibility, 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 visibility, 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, and is particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0235] Zb in formula 4-1 may be a counter ion for neutralizing the charge, and the entire compound 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.

[0236] Specific examples of the group represented by the above formula 4-1 are listed below, but the present disclosure is not limited to these. In the following structural formula, ● represents the bonding site with the group represented by L in formula 1-1.

[0237] [ka]

[0238] 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. These aryl groups may have a substituent.

[0239] In Formula 1-1, R 11 ~R 18 are each independently 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 formula (I) 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 hydrocarbon group, an alkyl group is particularly preferred.

[0240] 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 even more 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.

[0241] 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 groups formed by combining these groups.

[0242] R in Formula 1-1 11 ~R 14 are each independently a hydrogen atom or -R a (i.e., a hydrocarbon group), more preferably a hydrogen atom or an alkyl group, and even more preferably a hydrogen atom, except in the following cases. Among them, R bonded to the carbon atom bonded to the carbon atom bonded to L 11 and R 13 is preferably an alkyl group, and more preferably the two are linked to form a ring. The ring formed 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 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.

[0243] In Formula 1-1, n 13 is 1 and R 16 -R a (i.e., a hydrocarbon group) is preferred. Also, R 16 is A1 + R attached to the carbon atom to which 12 It is preferable that the ring is linked to the above to form a ring. The ring formed is preferably an indolium ring, a pyrylium ring, a thiopyrylium ring, a benzoxazoline ring, or a benzimidazoline ring, and from the viewpoint of improving the visibility of the exposed area, 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) is preferred. Also, R 18 is the R bonded to the carbon atom to which A2 is bonded. 14 It is preferable that the ring is linked to the above to form a ring. The ring formed is preferably an indole ring, a pyran ring, a thiopyran ring, a benzoxazole ring, or a benzimidazole ring, and from the viewpoint of improving the visibility of the exposed area, 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 preferably form a ring of the same structure.

[0244] R in Formula 1-1 15 and R17 are preferably the same group. 15 and R 17 -R a (i.e., a hydrocarbon group), more preferably an alkyl group, and even more preferably a substituted alkyl group.

[0245] 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).

[0246] [ka]

[0247] 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 represents R W5 represents an alkyl group having 1 to 12 carbon atoms, and 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.

[0248] In formula (a1), R W0 Specific 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. 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 W1is 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, an n-dodecyl group, and the like. 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:

[0249] Specific examples of the group represented by formula (a1) are shown below, but the present disclosure is not limited to these. In the following structural formula, Me represents a methyl group, Et represents an ethyl group, and * represents a bonding site.

[0250] [ka]

[0251] In formulas (a2) to (a4), R W2 ~R W4 Specific 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, an n-dodecylene group, and the like. 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), two M's may be the same or different.

[0252] 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 + or R in Formula 1-1 1 - may be a cation that can be contained in L.

[0253] Among the groups represented by formulae (a1) to (a4), groups represented by formula (a1), formula (a2) or formula (a4) are preferred.

[0254] n in Formula 1-1 11 and n 12 are preferably the same, and are both preferably integers of 1 to 5, more preferably integers of 1 to 3, further preferably 1 or 2, and particularly preferably 2.

[0255] In formula 1-1, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, and a nitrogen atom is preferred. In formula 1-1, A1 and A2 are preferably the same atom.

[0256] Za in Formula 1-1 represents a counter ion that neutralizes the charge. R 11 ~R 18 and R 1 If 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 anionic structures, Za can also be a counter cation. If the cyanine dye represented by formula 1-1 has a charge-neutral structure as a whole compound except for Za, Za is not necessary. When Za is a counter anion, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, and a perchlorate ion, with a 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.

[0257] 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).

[0258] [ka]

[0259] In formula 1-2, R 1 represents a group represented by any one of the above formulas 2-1 to 4-1, 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 represents R 23 and R 24 are each independently a hydrogen atom or -R a represents 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 R10 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.

[0260] R in Equation 1-2 1 is R in Equation 1-1 1 The same applies to the preferred embodiments.

[0261] 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 -R expressed as a is preferably an alkyl group or an alkenyl group. R 19 ~R 22 All of -R a If 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.

[0262] In Formula 1-2, R 23and 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.

[0263] 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 preferred.

[0264] In Equation 1-2, W 1 and W 2 are each independently preferably 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 2 are each independently an alkyl group having a substituent, and preferably a group having at least one of —OCHCH—, a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group, from the viewpoint of on-press developability.

[0265] Za represents a counter ion that neutralizes the charge within 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 anionic structures, Za can also be a counter cation. If the compound represented by formula 1-2 has a charge-neutral structure as a whole except for Za, Za is not necessary. Examples of when Za is a counter anion are the same as Za in formula 1-1, and preferred embodiments are also the same. Examples of when Za is a counter cation are the same as Za in formula 1-1, and preferred embodiments are also the same.

[0266] From the viewpoints of decomposability and visibility, 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 visibility, a compound represented by any one of formulas 1-3, 1-5, and 1-6 is preferred.

[0267] [ka]

[0268] In formulas 1-3 to 1-7, R 1 represents a group represented by any one of the above formulas 2-1 to 4-1, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -Ra , -OR b , -CN, -SR c , or -NR d R e represents R 25 and R 26 are each independently a hydrogen atom, a halogen atom, or -R a represents 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 that neutralizes the charge.

[0269] 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 ~R 22 , R d1 ~R d4 , W 1 , W 2 , and L, and the preferred embodiments are also the same. R in Equation 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.

[0270] Specific examples of cyanine dyes that are decomposable compounds are listed below, but the present disclosure is not limited to these.

[0271] [ka]

[0272] Furthermore, as the cyanine dye, which is a decomposable compound, the infrared absorbing compounds described in WO 2019 / 219560 can be suitably used.

[0273] 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 same applies to the preferred embodiments.

[0274] 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.

[0275] From the viewpoint of visibility, the content of the color-changing compound in the overcoat 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, relative to the total mass of the overcoat layer.

[0276] The content M of the color-changing compound in the overcoat layer X and the content M of the infrared absorber in the image recording layer. Y Relative to M X / M Y However, from the viewpoint of visibility, 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.

[0277] -Hydrophilic polymer- From the viewpoint of removability during development (more preferably, on-machine developability), the overcoat layer preferably contains a hydrophilic polymer, and more preferably contains a water-soluble polymer. In the present disclosure, a water-soluble polymer refers to a polymer that dissolves in an amount of 1 g or more 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 water-soluble polymers used in the overcoat layer include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, 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, and specific examples thereof include the modified polyvinyl alcohols described in JP-A Nos. 2005-250216 and 2006-259137. Among these, from the viewpoint of on-machine developability, cellulose derivatives are preferred as the hydrophilic polymer, and hydroxyalkyl cellulose is more preferred.

[0278] The water-soluble polymer is preferably polyvinyl alcohol, and more preferably polyvinyl alcohol having a degree of saponification of 50% or more. The saponification degree 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 saponification degree, as long as it is 100% or less. The degree of saponification is measured according to the method described in JIS K 6726:1994.

[0279] The water-soluble polymer also preferably includes polyvinylpyrrolidone. As the hydrophilic polymer, it is also preferable to use a combination of polyvinyl alcohol and polyvinylpyrrolidone.

[0280] The water-soluble polymers may be used alone or in combination of two or more.

[0281] When the overcoat 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 overcoat layer.

[0282] -Other ingredients- The overcoat layer may contain other components such as a hydrophobic polymer, an oil sensitizer, an acid generator, an infrared absorber, etc., in addition to the above-mentioned color-changing compound and water-soluble polymer. The other components will be described below.

[0283] <<Hydrophobic polymer>> The overcoat layer preferably contains a hydrophobic polymer. A hydrophobic polymer is a polymer that dissolves in 100 g of pure water at 70°C in an amount of less than 1 g or does not dissolve at all. Examples of hydrophobic polymers include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly(alkyl(meth)acrylate) (e.g., polymethyl(meth)acrylate, polyethyl(meth)acrylate, polybutyl(meth)acrylate, etc.), 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.

[0284] The hydrophobic polymer may be used alone or in combination of two or more kinds.

[0285] When the overcoat layer contains a hydrophobic polymer, the content of the hydrophobic polymer is preferably 1% by mass to 80% by mass, and more preferably 5% by mass to 50% by mass, based on the total mass of the overcoat layer.

[0286] <<Acid generator>> When an acid color former is used as the color-changing compound, the overcoat layer preferably contains an acid generator. The term "acid generator" as used herein refers to a compound that generates an acid when exposed to light or heat, and specifically refers to a compound that decomposes upon exposure to infrared light to generate an acid. The acid to be 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 aforementioned acid color former to change color.

[0287] Specifically, from the viewpoints of sensitivity and stability, onium salt compounds are preferred as the acid generator. 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.

[0288] The acid generators may be used alone or in combination of two or more. When the overcoat 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 overcoat layer.

[0289] The overcoat layer may contain known additives such as an oil sensitizer, an inorganic layer compound, a surfactant, etc., in addition to the components already described.

[0290] The overcoat layer is formed by coating and drying using a known method. The coating amount (solid content) of the overcoat 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 overcoat layer is preferably 0.1 μm to 5.0 μm, and more preferably 0.3 μm to 4.0 μm.

[0291] The thickness of the overcoat 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.

[0292] The overcoat layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coatability, and inorganic particles for controlling surface slippage.

[0293] <Support> The lithographic printing plate precursor according to the present disclosure has a support. The support can be appropriately selected from known supports for lithographic printing plate precursors. The support is preferably a support having a hydrophilic surface (hereinafter also referred to as "hydrophilic support").

[0294] The 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 support in the present disclosure preferably comprises an aluminum plate and an anodized aluminum coating disposed on the aluminum plate.

[0295] Furthermore, it is preferable that the support has an aluminum plate and an anodized aluminum film disposed on the aluminum plate, the anodized film being located closer to the image recording layer than the aluminum plate, the anodized film having micropores extending in the depth direction from the surface on the image recording layer side, and the average diameter of the micropores on the surface of the anodized film being greater than 10 nm and not greater than 100 nm. Furthermore, it is preferable that 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, and that the average diameter of the large-diameter pores at the surface of the anodized film is 15 nm to 100 nm, and the average diameter of the small-diameter pores at the communicating positions is 13 nm or less.

[0296] 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 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.

[0297] -Anodic oxide film- A preferred embodiment of the anodic oxide coating 20a will now be described. The anodized film 20a is a film formed on the surface of the aluminum plate 18 by anodizing, and has extremely fine micropores 22a that are substantially 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 the aluminum plate 18) along the thickness direction (toward the aluminum plate 18).

[0298] 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. From the viewpoint of a balance between printing durability, stain resistance, and image visibility, the average 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. When the average diameter exceeds 10 nm, printing durability and image visibility are excellent, and when the average diameter is 100 nm or less, printing durability is excellent. The average diameter of the micropores 22a was determined by observing the surface of the anodized film 20a using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times (N=4), measuring the diameter of the micropores present in an area of ​​400 nm x 600 nm at 50 locations in the four images obtained, and averaging the measured values. 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.

[0299] The shape of the micropores 22a is not particularly limited, and although they are generally straight (cylindrical) in Fig. 1, they may also be conical with a diameter that decreases 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.

[0300] In the support, the micropores may be composed of large-diameter pores extending from the surface of the anodized coating to a certain depth, and small-diameter pores communicating with the bottoms of the large-diameter pores and extending from the communicating position to a certain depth. For example, as shown in FIG. 2, an aluminum support 12b may include an aluminum plate 18 and an anodized film 20b having micropores 22b each composed of a large diameter pore portion 24 and a small diameter pore portion . For example, the micropores 22b in the anodized coating 20b are composed of large-diameter pores 24 that extend from the surface of the anodized coating to a depth of 10 nm to 1,000 nm (depth D: see FIG. 2), and small-diameter pores 26 that communicate with the bottoms of the large-diameter pores 24 and extend from the communicating position to a depth of 20 nm to 2,000 nm. Specifically, for example, the embodiments described in paragraphs 0107 to 0114 of JP 2019-162855 A can be used.

[0301] -Method of manufacturing support- As a method for producing a support used in the present disclosure, for example, a production method in which the following steps are carried out in order is preferred. Surface roughening process: A process of roughening the surface of aluminum plates. Anodizing process: A process of anodizing a roughened aluminum plate. Pore ​​widening process: The aluminum plate with the anodized film obtained in the anodizing process is brought into contact with an acidic or alkaline aqueous solution to widen the diameter of the micropores in the anodized film. The procedure for each step will be described in detail below.

[0302] <<Surface roughening process>> The surface roughening step is a step of roughening the surface of an aluminum plate, including electrochemical roughening. This step is preferably performed before the anodizing step described below, but may not be necessary if the surface of the aluminum plate already has a desired surface shape. This step can be performed by the method described in paragraphs 0086 to 0101 of JP 2019-162855 A.

[0303] <<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 treatment step, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, etc. can be used as the electrolytic bath. For example, the concentration of sulfuric acid can be 100 g / L to 300 g / L. The conditions for anodizing treatment are appropriately set depending on the electrolyte used, but for example, the solution 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 0.2g / m 2 ~3g / m 2 ) are mentioned.

[0304] <<Porewide processing>> The pore widening treatment is a treatment (pore diameter enlargement treatment) for enlarging the diameter of the micropores (pore diameter) present in the anodized film formed by the above-mentioned anodizing treatment step. The pore widening treatment can be carried out by bringing the aluminum plate obtained by the above-mentioned anodizing treatment step into contact 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.

[0305] If necessary, the support may have a backcoat layer on the side opposite the image recording layer, which contains an organic polymer compound described in JP-A-5-45885 or a silicon alkoxy compound described in JP-A-6-35174.

[0306] <Undercoat layer> The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (sometimes referred to as an intermediate layer) between the image recording layer and the support. The undercoat layer strengthens adhesion between the support and the image recording layer in exposed areas and facilitates peeling of the image recording layer from the support in unexposed areas, 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 heat generated by exposure from diffusing to the support and reducing sensitivity.

[0307] Compounds used in the undercoat layer include polymers having an adsorptive group and a hydrophilic group that can be adsorbed to the support surface. Polymers having an adsorptive group and a hydrophilic group and also a crosslinkable group are preferred to improve adhesion to the image recording layer. The compounds used in the undercoat layer may be low-molecular-weight compounds or polymers. Two or more compounds may be mixed together as needed.

[0308] 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. Preferred adsorptive groups that can be adsorbed onto the surface of a support include phenolic hydroxy groups, carboxy groups, -PO3H2, -OPO3H2, -CONHSO2-, -SON2NHSO2-, and -COCH2COCH3. Preferred hydrophilic groups include sulfo groups or salts thereof, and carboxy group salts. Preferred crosslinkable groups include acrylic groups, methacrylic groups, acrylamide groups, methacrylamide groups, and allyl groups. 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 be further copolymerized with a monomer other than the above, preferably a hydrophilic monomer.

[0309] Specific examples of suitable compounds include a silane coupling agent having an addition-polymerizable ethylenic double bond reactive group, as described in JP-A-10-282679, and a phosphorus compound having an ethylenic double bond reactive group, as described in JP-A-2-304441. Also preferred are low-molecular-weight or high-molecular-weight compounds having a crosslinkable group (preferably an ethylenically unsaturated bond group), a functional group that interacts with the support surface, and a hydrophilic group, as described in JP-A-2005-238816, JP-A-2005-125749, JP-A-2006-239867, and JP-A-2006-215263. More preferred examples include high molecular weight polymers having adsorptive groups, hydrophilic groups, and crosslinkable groups capable of being adsorbed onto the surface of a support, as described in JP-A Nos. 2005-125749 and 2006-188038.

[0310] The content of the ethylenically unsaturated bond group in the polymer used in the undercoat layer is preferably 0.1 mmol to 10.0 mmol, and more preferably 0.2 mmol to 5.5 mmol, per 1 g of the polymer. The weight average molecular weight (Mw) of the polymer used in the undercoat layer is preferably 5,000 or more, more preferably 10,000 to 300,000.

[0311] -Hydrophilic compounds- From the viewpoint of developability, the undercoat layer preferably contains a hydrophilic compound. The hydrophilic compound is not particularly limited, and known hydrophilic compounds used in undercoat layers can be used. Preferred examples of the hydrophilic compound include carboxymethyl cellulose, phosphonic acids having an amino group such as dextrin, organic phosphonic acids, organic phosphoric acids, organic phosphinic acids, amino acids, and hydrochlorides of amines having a hydroxy 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.).

[0312] 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 prevention, the hydrophilic compound, preferably a hydroxycarboxylic acid or a salt thereof, is preferably contained in a layer on the aluminum support, and 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 that is in contact with the aluminum support. A layer other than the layer in contact with the aluminum support, such as an overcoat 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 this embodiment, at least a portion of the treated hydroxycarboxylic acid or a salt thereof can be detected in a layer (e.g., the image recording layer or an undercoat layer) on the image recording layer side that is 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 contacts 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 on the surface of the aluminum support on the image recording layer side, as measured by the airborne water drop method, can be easily reduced to 110° or less, resulting in excellent scratch and stain resistance.

[0313] Hydroxycarboxylic acid is a general term for organic compounds that have one or more carboxyl groups and one or more hydroxyl 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, Iwanami Shoten, 1998). The 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 HC may be the same or different.

[0314] In formula (HC), R HC Examples of the mhc+nhc valent organic group represented by the formula include mhc+nhc valent hydrocarbon groups, etc. The hydrocarbon group may have a substituent and / or a linking group. Examples of the hydrocarbon group include mhc+nhc valent 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, and alkynpentyl groups, and mhc+nhc valent groups derived from aromatic hydrocarbons, such as arylene groups, arenetriyl groups, arenetetrayl groups, and arenepentyl groups. Examples of the substituent include alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, and aryl groups. Specific examples of the substituent include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, 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, an ethoxyphenyl group, a phenoxyphenyl group, an acetoxyphenyl group, a benzoyloxyphenyl group, a methoxycarbonylphenyl group, an ethoxycarbonylphenyl group, and a phenoxycarbonylphenyl group. 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 alkylene groups, substituted alkylene groups, arylene groups, and substituted arylene groups, and these divalent groups may have a structure in which a plurality of these groups are linked together by any of amide bonds, ether bonds, urethane bonds, urea bonds, and ester bonds.

[0315] 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 prevention, 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.

[0316] 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. The molecular weight is preferably 76 or more. Specific examples of the hydroxycarboxylic acids constituting the above hydroxycarboxylic acids or salts of the above hydroxycarboxylic acids 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, ricinelaideic acid, cerebronic acid, quinic acid, shikimic acid, monohydroxybenzoic acid derivatives (salicylic acid, creosoteic acid, etc.), and the like. Examples of suitable benzoates 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.).

[0317] 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 five to eight hydroxy groups. Furthermore, gluconic acid or shikimic acid is preferred as an acid having one carboxy group and two or more hydroxy groups. As an acid having two or more carboxy groups and one hydroxy group, citric acid or malic acid is preferred. Tartaric acid is preferred as an acid having two or more carboxy groups and two or more hydroxy groups. Among these, gluconic acid is particularly preferred as the hydroxycarboxylic acid.

[0318] 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.

[0319] 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.

[0320] The primer layer is applied by known methods. The coating amount (solid content) of the primer layer is 0.1 mg / m 2 ~300mg / m 2 is preferred, and 5 mg / m 2 ~200mg / m 2 is more preferred.

[0321] The lithographic printing plate precursor according to the present disclosure may have layers other than those described above. The other layers are not particularly limited, and any known layers may be used. For example, a backcoat layer may be provided on the side of the support opposite to the image recording layer side, as needed.

[0322] (Method for producing a lithographic printing plate and lithographic printing method) 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 in an imagewise manner (exposure step), and a step of supplying at least one selected from the group consisting of printing ink and fountain solution to the exposed lithographic printing plate precursor on a printing press to remove the image recording layer in non-image areas (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 to light in an imagewise manner (exposure step), a step of supplying at least one selected from the group consisting of printing ink and dampening water on a printing press to remove the image recording layer in non-image areas to prepare a lithographic printing plate (on-press development step), and a step of printing with the obtained lithographic printing plate (hereinafter also referred to as a "printing step").

[0323] <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 exposed areas and unexposed areas. 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 beam scanning using digital data. The wavelength of the light source used 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 semiconductor laser that emits infrared light 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 irradiation energy amount 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, or 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.

[0324] <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 dampening water on the printing press to remove the image recording layer in the non-image areas. The on-press development method will be described below.

[0325] [On-press development method] In the on-press development method, it is preferred 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 imagewise exposure, the lithographic printing plate precursor is either mounted on a printing press without any development process, or mounted on a printing press and imagewise exposed on the press, followed by supplying oil-based ink and aqueous components for printing. During the initial printing process, the uncured image-recording layer in the non-image areas is dissolved or dispersed by either or both of the supplied oil-based ink and aqueous components, thereby exposing a hydrophilic surface. Meanwhile, in the exposed areas, the image-recording layer cured by exposure forms an oil-based ink-receptive area with a lipophilic surface. Either oil-based ink or aqueous components may be applied first to the plate surface, but applying oil-based ink first is preferred to prevent contamination of the aqueous components by the components of the removed image-recording layer. In this way, the lithographic printing plate precursor is developed on the press and used directly for printing multiple sheets. Typical lithographic printing inks and fountain solutions are preferably used as the oil-based ink and aqueous components.

[0326] The laser used for imagewise exposing the lithographic printing plate precursor according to the present disclosure has a light source wavelength of 750 nm to 1,400 nm. The light source having a wavelength of 750 nm to 1,400 nm is preferably one of those described above.

[0327] <Printing process> The lithographic printing method according to the present disclosure includes supplying printing ink to a lithographic printing plate to print a recording medium. Includes the printing process. 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 ink and ultraviolet-curable ink (UV ink). In the printing process, dampening water may be supplied as needed. The printing step may be carried out consecutively to the on-press developing step or the developer developing step without stopping the printing press. The recording medium is not particularly limited, and any known recording medium can be used as desired.

[0328] 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-forming reaction in the image-recording layer, resulting in advantages such as improved sensitivity and printing durability and stabilized sensitivity. Heating before development is preferably carried out under mild conditions at 150°C or less. This embodiment can prevent problems such as hardening of non-image areas. Heating after development is preferably carried out under very strong conditions, preferably in the range of 100°C to 500°C. Within this range, sufficient image strengthening effect can be obtained and problems such as support degradation and thermal decomposition of image areas can be suppressed. [Example]

[0329] The present disclosure will be described in detail below using examples, but the present disclosure is not limited thereto. In these examples, "%" and "parts" mean "% by mass" and "parts by mass", respectively, unless otherwise specified. In addition, in polymer compounds, unless otherwise specified, the molecular weight is the weight average molecular weight (Mw), and the ratio of the constituent repeating units is expressed as a molar percentage. In addition, the weight average molecular weight (Mw) is a value measured as a polystyrene equivalent value by gel permeation chromatography (GPC).

[0330] (Examples 1 to 38 and Comparative Examples 1 to 6) <Preparation of Supports A and B> <<Processes A and B>> (Aa) Alkaline etching treatment An aqueous solution of caustic soda with a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass was sprayed onto the aluminum plate at a temperature of 70°C to carry out an etching treatment. After that, the aluminum plate was rinsed with water by spraying. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m 2 It was.

[0331] (Ab) Desmutting treatment using an acidic aqueous solution (first desmutting treatment) Next, a desmutting treatment was carried out using an acidic aqueous solution. The acidic aqueous solution used for the desmutting treatment was an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature was 30°C. The acidic aqueous solution was sprayed onto the aluminum plate, and the desmutting treatment was carried out for 3 seconds. After that, a water rinsing treatment was carried out.

[0332] (Ac) Electrochemical roughening treatment Next, electrochemical graining treatment was performed using an electrolytic solution with a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L, using an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The AC waveform is a sine wave with symmetrical positive and negative waveforms, the frequency is 50 Hz, the anode reaction time and cathode reaction time in one AC cycle are 1:1, and the current density is 75 A / dm at the peak current value of the AC waveform. 2 The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm 2 and electrolytic treatment is 112.5C / dm 2 The test was carried out four times, with a 4-second interval between each test. A carbon electrode was used as the counter electrode for the aluminum plate. After that, the plate was washed with water.

[0333] (Ad) Alkaline etching treatment After electrochemical graining, the aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions at 45°C. The amount of dissolved aluminum on the electrochemical graining surface was 0.2 g / m 2 After that, a water washing treatment was carried out.

[0334] (Ae) Desmutting treatment using an acidic aqueous solution Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used for the desmutting treatment had a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The liquid temperature was 30°C.

[0335] (Af) First stage anodizing The first stage of anodizing treatment was carried out using a DC electrolysis anodizing device with the structure shown in Figure 3. Anodizing treatment was carried out under the conditions in the "First anodizing treatment" column in Table 1, and an anodized film of the specified film thickness was formed.

[0336] (Ag) Pore-wide processing The anodized aluminum plate was subjected to a pore widening treatment by immersing it in an aqueous solution of caustic soda with a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass at a temperature of 40°C for the time shown in Table 1. It was then rinsed with water by spraying.

[0337] (Ah) Second stage anodizing The second stage of anodizing treatment was carried out using a DC electrolysis anodizing device with the structure shown in Figure 3. Anodizing treatment was carried out under the conditions in the "Second Anodizing Treatment" column shown in Table 1, and an anodized film of the specified film thickness was formed. As shown in Table 1, the second stage of anodizing treatment was not carried out for surface treatment B.

[0338] [Table 1]

[0339] <Preparation of supports C to E> <<Surface Treatment C>> (Ca) Mechanical roughening treatment (brush grain method) Using the apparatus shown in Figure 5, a pumice suspension (specific gravity 1.1 g / cm 3) was supplied to the surface of the aluminum plate as an abrasive slurry, while mechanical roughening treatment was performed using a rotating bundled brush. In Fig. 5, 1 is the aluminum plate, 2 and 4 are roller-shaped brushes (bundled brushes in this example), 3 is the abrasive slurry, and 5, 6, 7, and 8 are support rollers. The mechanical roughening treatment used a 30 μm median abrasive diameter (μm), four brushes, and a brush rotation speed (rpm) of 250 rpm. The brush bundles were made of 6·10 nylon, with bristles of 0.3 mm diameter and 50 mm length. The brushes were densely packed into holes drilled into a 300 mm diameter stainless steel cylinder. The distance between the two support rollers (φ200 mm) below the brush bundles was 300 mm. The brush bundles were pressed down until the load on the drive motor rotating the brushes was 10 kW higher than the load before pressing the brush bundles against the aluminum plate. The brush rotation direction was the same as the movement direction of the aluminum plate.

[0340] (Cb) Alkaline etching treatment The aluminum plate obtained above was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass at a temperature of 70°C using a spray tube. Thereafter, the plate was washed with water using a spray. The amount of dissolved aluminum was 10 g / m 2 It was.

[0341] (Cc) Desmutting in an acidic aqueous solution Next, desmutting treatment was carried out in a nitric acid aqueous solution. The nitric acid aqueous solution used in the desmutting treatment was the waste nitric acid solution used in the subsequent electrochemical roughening process. The liquid temperature was 35°C. The desmutting solution was sprayed onto the surface for 3 seconds.

[0342] (Cd) Electrochemical roughening treatment A continuous electrochemical roughening treatment was carried out using nitric acid electrolysis and a 60 Hz AC voltage. The electrolyte used was an aqueous solution of nitric acid at 35°C, 10.4 g / L, to which aluminum nitrate was added to adjust the aluminum ion concentration to 4.5 g / L. The AC power waveform was as shown in Figure 3, with a time tp from zero to peak of 0.8 msec, a duty ratio of 1:1, and a trapezoidal square wave AC current. Ferrite was used as the auxiliary anode. The electrolytic cell used was as shown in Figure 4. The current density was 30 A / dm at the peak current value. 2 5% of the current flowing from the power supply was shunted to the auxiliary anode. 2 ) is the total amount of electricity when the aluminum plate is the anode, 185C / dm 2 After that, the surface was washed with water using a spray.

[0343] (Ce) Alkaline etching treatment The aluminum plate obtained above was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass at a temperature of 50°C using a spray tube. Thereafter, the plate was washed with water using a spray. The amount of dissolved aluminum was 0.5 g / m 2 It was.

[0344] (Cf) Desmutting in an acidic aqueous solution Next, desmutting treatment was carried out in an aqueous sulfuric acid solution. The aqueous sulfuric acid solution used for the desmutting treatment had a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The solution temperature was 30°C. The desmutting solution was sprayed onto the material for 3 seconds.

[0345] (Cg) Electrochemical roughening treatment Continuous electrochemical roughening treatment was performed using hydrochloric acid electrolysis at 60 Hz AC voltage. The electrolyte used was a 6.2 g / L aqueous solution of hydrochloric acid at 35°C, with aluminum chloride added to adjust the aluminum ion concentration to 4.5 g / L. The AC power waveform was as shown in Figure 3, with a zero-to-peak current time (tp) of 0.8 msec, a duty ratio of 1:1, and a trapezoidal square wave AC. Ferrite was used as the auxiliary anode. The electrolytic cell used was as shown in Figure 4. The peak current density is 25A / dm 2 and the amount of electricity in hydrochloric acid electrolysis (C / dm 2 ) is the total amount of electricity when the aluminum plate is the anode, 63C / dm 2 After that, the surface was washed with water using a spray.

[0346] (Ch) Alkaline etching treatment The aluminum plate obtained above was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass at a temperature of 50°C using a spray tube. Thereafter, the plate was washed with water using a spray. The amount of dissolved aluminum was 0.1 g / m 2 It was.

[0347] (Ci) Desmutting in acidic aqueous solution Next, desmutting was carried out in an aqueous sulfuric acid solution. Specifically, the waste liquid generated in the anodizing process (a 170 g / L aqueous sulfuric acid solution containing 5 g / L of aluminum ions) was used, and the desmutting was carried out for 4 seconds at a liquid temperature of 35°C. The desmutting solution was sprayed onto the material for 3 seconds.

[0348] (Cj) First stage anodizing The first stage of anodizing treatment was performed using a DC electrolysis anodizing apparatus with the structure shown in FIG. 3. Anodizing treatment was performed under the conditions shown in Table 1, and an anodized film with a predetermined thickness was formed. In the anodizing treatment apparatus 610, an aluminum sheet 616 was transported as shown by the arrow in FIG. 3. In a power supply tank 612 containing an electrolytic solution 618, the aluminum sheet 616 was positively charged by a power supply electrode 620. The aluminum sheet 616 was then transported upward in the power supply tank 612 by rollers 622, redirected downward by nip rollers 624, transported toward an electrolytic treatment tank 614 containing an electrolytic solution 626, and redirected horizontally by rollers 628. The aluminum sheet 616 was then negatively charged by an electrolytic electrode 630, forming an anodized film on its surface. The aluminum sheet 616 then left the electrolytic treatment tank 614 and was transported to a subsequent process. In the anodizing treatment device 610, a direction changing means is formed by a roller 622, a nip roller 624, and a roller 628, and the aluminum plate 616 is transported in a mountain shape and an inverted U shape by the rollers 622, 624, and 628 in the space between the power supply tank 612 and the electrolytic treatment tank 614. The power supply electrode 620 and the electrolysis electrode 630 are connected to a DC power supply 634.

[0349] (Ck) Porewide processing The anodized aluminum plate was subjected to a pore widening treatment by immersing it in an aqueous solution of caustic soda with a temperature of 35°C, a caustic soda concentration of 5 mass%, and an aluminum ion concentration of 0.5 mass% under the conditions shown in Table 1. It was then rinsed with water by spraying.

[0350] (Cl) Second stage anodizing The second stage of anodizing treatment was carried out using a direct current electrolysis anodizing apparatus with the structure shown in Figure 3. Anodizing treatment was carried out under the conditions shown in Table 2, and an anodized film with a specified film thickness was formed.

[0351] (Cm) Third stage anodizing The third stage of anodizing treatment was carried out using a direct current electrolysis anodizing apparatus with the structure shown in Figure 3. Anodizing treatment was carried out under the conditions shown in Table 2, and an anodized film with a specified film thickness was formed.

[0352] <<Surface Treatment D>>: [Support having large diameter hole portions and small diameter hole portions] (Da) Alkaline etching treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda (sodium hydroxide) with a concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass onto the plate using a spray tube at a temperature of 70°C. The plate was then rinsed with water using a spray. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 1.0 g / m. 2 It was.

[0353] (Db) Desmutting treatment in an acidic aqueous solution (first desmutting treatment) Next, desmutting treatment was carried out in an acidic aqueous solution. The acidic aqueous solution used for the desmutting treatment was an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature was 30°C. The desmutting solution was sprayed onto the surface for 3 seconds, followed by a water rinsing treatment.

[0354] (Dc) Electrochemical roughening treatment in hydrochloric acid solution Next, an electrolytic surface roughening treatment was carried out using an alternating current in an electrolyte solution with a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L. The temperature of the electrolyte was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The alternating current waveform was a sine wave with symmetrical positive and negative waveforms, a frequency of 50 Hz, the anode reaction time and cathode reaction time in one cycle of the alternating current were 1:1, and the current density was 75 A / dm at the peak current value of the alternating current waveform. 2 The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm 2 and electrolytic treatment is 125C / dm 2 The test was carried out four times, with a 4-second interval between each test. A carbon electrode was used as the counter electrode for the aluminum plate. After that, the plate was washed with water.

[0355] (Dd) Alkaline etching treatment After electrochemical graining, the aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions onto the plate at 45°C using a spray tube. The amount of dissolved aluminum on the electrochemically grained surface was 0.2 g / m. 2 After that, a water washing treatment was carried out.

[0356] (De) Desmutting in an acidic aqueous solution Next, a desmutting treatment was carried out in an acidic aqueous solution. The acidic aqueous solution used for the desmutting treatment was waste liquid generated in the anodizing treatment process (a 170 g / L aqueous solution of sulfuric acid with 5.0 g / L of aluminum ions dissolved in it). The liquid temperature was 30°C. The desmutting solution was sprayed onto the surface for 3 seconds.

[0357] (Df) First stage anodizing The first stage of anodizing treatment was carried out using a direct current electrolysis anodizing apparatus with the structure shown in Figure 3. Anodizing treatment was carried out under the conditions shown in Table 2, and an anodized film with a specified film thickness was formed.

[0358] (Dg) Porewide processing The anodized aluminum plate was subjected to a pore widening treatment by immersing it in an aqueous solution of caustic soda with a temperature of 35°C, a caustic soda concentration of 5 mass%, and an aluminum ion concentration of 0.5 mass% under the conditions shown in Table 1. It was then rinsed with water by spraying.

[0359] (Dh) Second stage anodizing The second stage of anodizing treatment was carried out using a direct current electrolysis anodizing apparatus with the structure shown in Figure 3. Anodizing treatment was carried out under the conditions shown in Table 2, and an anodized film with a specified film thickness was formed.

[0360] By the above surface treatment C or D, supports C to E shown in Tables 2 and 3 were obtained.

[0361] The average diameter (nm) of the large pores on the surface of the anodized film after the second anodizing treatment step, the average diameter (nm) of the small pores at the interconnected positions, the depth (nm) of the large pores and the small pores, and the pit density (density of micropores, unit: pits / μm 2 ), and the thickness (nm) of the anodic oxide film from the bottom of the small diameter hole to the surface of the aluminum plate are shown in Table 2. The average diameter of the micropores (average diameter of the large-diameter pore portion and the small-diameter pore portion) was determined by observing the surfaces of the large-diameter pore portion and the small-diameter pore portion using an FE-SEM at a magnification of 150,000 times (N=4), measuring the diameters of the micropores (large-diameter pore portion and small-diameter pore portion) present within a range of 400 nm × 600 nm in the four images obtained, and averaging them. When the large-diameter pore portion was deep and the diameter of the small-diameter pore portion was difficult to measure, or when measuring enlarged-diameter pores within the small-diameter pore portion, the upper part of the anodized film was cut, and then the various diameters were determined. The micropore depths (depths of large-diameter pores and small-diameter pores) were determined by observing the cross section of the support (anodic oxide film) with an FE-SEM (large-diameter pore depth observation: 150,000x, small-diameter pore depth observation: 50,000x), measuring the depths of 25 randomly selected micropores in the resulting image, and averaging the measured values. In Table 2, the film amount (AD) in the first anodizing treatment column and the film amount (AD) in the second anodizing treatment column represent the film amount obtained by each treatment. The electrolyte used is an aqueous solution containing the components shown in Table 2.

[0362] [Table 2]

[0363] [Table 3]

[0364] <Method for forming undercoat layers A to C> On the support shown in Tables 5 to 8, one of the undercoat layer coating solutions A to C having the following compositions shown in Tables 5 to 8 was applied in a dry coating amount of 20 mg / m 2The coating was dried in an oven at 100°C for 30 seconds to form a primer layer.

[0365] - Composition of primer layer coating solution A - Polymer (U-1) [structure below]: 0.18 parts Hydroxyethyliminodiacetic acid: 0.10 parts ·Wednesday: 61.4 parts

[0366] [ka]

[0367] - Composition of primer layer coating solution B - Polymer (U-1): 0.14 parts Sodium gluconate: 0.07 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.0016 parts Preservative (BioHope L, manufactured by K.I. Kasei Co., Ltd.): 0.0015 parts ·Wednesday: 3.29 parts

[0368] - Composition of primer layer coating solution C - Polymer (U-1): 0.14 parts Chelate 400: 0.035 parts Chelate 3EAF: 0.035 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.0016 parts Preservative (BioHope L, manufactured by K.I. Kasei Co., Ltd.): 0.0015 parts ·Wednesday: 3.29 parts

[0369] -Synthesis of polymer (U-1)- <<Purification of Monomer M-1>> 420 parts of Light Ester P-1M (2-methacryloyloxyethyl acid phosphate, Kyoeisha Chemical Co., Ltd.), 1,050 parts of diethylene glycol dibutyl ether, and 1,050 parts of distilled water were added to a separatory funnel, vigorously stirred, and then allowed to stand. After discarding the upper layer, 1,050 parts of diethylene glycol dibutyl ether was added, vigorously stirred, and then allowed to stand. The upper layer was discarded, yielding 1,300 parts of an aqueous solution of Monomer M-1 (10.5% by mass in terms of solids content).

[0370] <<Synthesis of Polymer (U-1)>> A three-neck flask was charged with 53.73 parts of distilled water and 3.66 parts of the monomer M-2 shown below, and the temperature was raised to 55°C under a nitrogen atmosphere. Next, the dropping solution 1 shown below was added dropwise over 2 hours. After stirring for 30 minutes, 0.386 parts of VA-046B (Fujifilm Wako Pure Chemical Industries, Ltd.) was added, the temperature was raised to 80°C, and the mixture was stirred for 1.5 hours. After the reaction solution was returned to room temperature (25°C), a 30% by weight aqueous solution of sodium hydroxide was added to adjust the pH to 8.0, and then 0.005 parts of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO) was added. Through the above operations, 180 parts of an aqueous solution of polymer (U-1) was obtained. The weight-average molecular weight (Mw) calculated as a polyethylene glycol equivalent by gel permeation chromatography (GPC) was 200,000.

[0371] [ka]

[0372] <<Composition of Dropping Solution 1>> Aqueous solution of the above monomer M-1: 87.59 parts Monomer M-2: 14.63 parts VA-046B (2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.): 0.386 parts Distilled water: 20.95 parts

[0373] <Formation of image recording layer> An image recording layer coating solution having the composition shown in Tables 5 to 8 (wherein the image recording layer coating solution contained each of the components shown in Tables 5 to 8 and was prepared in a mixed solvent of 1-methoxy-2-propanol (MFG):methyl ethyl ketone (MEK):methanol = 4:4:1 (mass ratio) so that the solid content was 6 mass %. The amounts added shown in Tables 5 to 8 indicate the solid amount, excluding the inorganic layer compound dispersion) was bar coated on the support or undercoat layer, and the resulting solution was oven-dried at 120°C for 40 seconds to form an image recording layer with the dry coating amount shown in Tables 5 to 8. The components used in the image recording layer are shown below.

[0374] [Oil agent] O-1 to O-13: The following compounds (physical properties and the like are shown in Table 4 below).

[0375] [ka]

[0376] [Table 4]

[0377] [Infrared absorber] IR-1 to IR-10: Compounds with the following structure

[0378] [ka]

[0379] In addition, Bu represents an n-butyl group, Ph represents a phenyl group, and TsO - represents the tosylate anion.

[0380] [Electron-accepting polymerization initiator] Int-1 to Int-5: Compounds with the following structures, - represents a tosylate anion, and Ph represents a phenyl group.

[0381] [ka]

[0382] Electron-donating polymerization initiator B-1 to B-4: Compounds with the following structures

[0383]

Chemical formula

[0384] Polymerizable compound M-1: The following compound M-2: The following compound M-3: Dipentaerythritol pentaacrylate, SR-399 manufactured by Sartomer M-4: Urethane acrylate, U-15HA manufactured by Shin-Nakamura Chemical Co., Ltd. M-5: Monomer synthesized by the following synthesis method

[0385]

Chemical formula

[0386] <Synthesis of M-5> A mixed solution of Takenate D-160N (polyisocyanate trimethylolpropane adduct, manufactured by Mitsui Chemicals, Inc., 4.7 parts), Aronix M-403 (manufactured by Toagosei Co., Ltd., in an amount such that the NCO value of Takenate D-160N and the hydroxyl value of Aronix M-403 were 1:1), t-butylbenzoquinone (0.02 parts), and methyl ethyl ketone (11.5 parts) was heated to 65°C. Neostan U-600 (bismuth-based polycondensation catalyst, manufactured by Nitto Kasei Co., Ltd., 0.11 parts) was added to the reaction solution, and the mixture was heated at 65°C 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 solids content of 50% by mass. Using a recycle-type GPC (instrument: LC908-C60, columns: JAIGEL-1H-40 and 2H-40 (manufactured by Japan Analytical Industry Co., Ltd.)), molecular weight fractionation of the urethane acrylate (M-5) solution was carried out with an eluent of tetrahydrofuran (THF). The weight-average molecular weight was 20,000.

[0387] [Binder polymer] P-1: Polyvinyl alcohol, S-LEC BX-5Z manufactured by Sekisui Chemical Co., Ltd. P-2: Polyvinyl alcohol, S-LEC BL10 manufactured by Sekisui Chemical Co., Ltd. P-3: Resin synthesized by the following synthesis method

[0388] <Synthesis of binder polymer P-3> 78.0 parts of 1-methoxy-2-propanol were weighed into a three-neck flask and heated to 70 ° C. under a nitrogen stream. A mixed solution consisting of 52.1 parts of Blenmer PME-100 (methoxydiethylene glycol monomethacrylate, manufactured by Nippon Oil & Fats Co., Ltd.), 21.8 parts of methyl methacrylate, 14.2 parts of methacrylic acid, 2.15 parts of hexakis(3-mercaptopropionic acid)dipentaerythritol, 0.38 parts of V-601 (2,2'-azobis(isobutyrate)dimethyl, manufactured by Wako Pure Chemical Industries, Ltd.), and 54 parts of 1-methoxy-2-propanol was added dropwise to the reaction vessel over 2 hours and 30 minutes. After the dropwise addition was completed, the temperature was raised to 80 ° C., and the reaction was continued for another 2 hours. A mixed solution consisting of 0.04 parts of V-601 and 4 parts of 1-methoxy-2-propanol was added, and the temperature was raised to 90° C., followed by reaction for 2.5 hours. After completion of the reaction, the reaction solution was cooled to room temperature. To the above reaction solution, 137.2 parts of 1-methoxy-2-propanol, 0.24 parts of 4-hydroxytetramethylpiperidine-N-oxide, 26.0 parts of glycidyl methacrylate, and 3.0 parts of tetraethylammonium bromide were added and stirred thoroughly, followed by heating at 90°C. After 18 hours, the reaction solution was cooled to room temperature (25°C) and then diluted with 99.4 parts of 1-methoxy-2-propanol. The binder polymer P-3 thus obtained had a solid content concentration of 23% by mass and a weight average molecular weight of 35,000 in terms of polystyrene measured by GPC.

[0389] [ka]

[0390] [Acid color former] S-1 to S-8: the following compounds

[0391] [ka]

[0392] In addition, Me represents a methyl group, and Et represents an ethyl group.

[0393] [Color-forming compound] Curcumin: The following compound

[0394] [ka]

[0395] [Hydrophilic compound] T-1: Tris(2-hydroxyethyl) isocyanurate T-2: Compound of the following structure T-3: Hydroxypropyl cellulose, Klucel M, manufactured by Hercules

[0396] [ka]

[0397] [Surfactant] F-1: Anionic surfactant, Rapisol A-80, manufactured by NOF Corporation F-2: Fluorine-based surfactant, Megafac F-781F (DIC Corporation) F-3: The following compound

[0398] [ka]

[0399] [Polymer particles] <Preparation of Polymer Particles R-1> Microgel (polymer particles R-1): 2.640 parts Distilled water: 2.425 parts The preparation method of the above microgel is as follows.

[0400] -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. Once 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).

[0401] [ka]

[0402] -Preparation of microgels- The oil phase and aqueous phase components listed below were mixed and emulsified using a homogenizer at 12,000 rpm for 10 minutes. The resulting emulsion was stirred at 45°C for 4 hours, after which 5.20 g of a 10% by weight aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) was added. The mixture was stirred at room temperature for 30 minutes and then allowed to stand at 45°C for 24 hours. The solids concentration was adjusted to 20% by weight with distilled water, yielding an aqueous dispersion of microgel. The average particle size was measured by light scattering and found to be 0.20 μm.

[0403] ~Oily phase ingredients~ (Component 1) Ethyl acetate: 12.0 parts (Component 2) 3.76 parts of an adduct (50% by mass ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.) obtained by adding trimethylolpropane (6 molar equivalents) and xylene diisocyanate (18 molar equivalents) to which one-terminal methylated polyoxyethylene (1 molar equivalent, number of repeating oxyethylene units: 90) was added. (Component 3) Polyisocyanate compound (1) (as a 50% by mass ethyl acetate solution): 15.0 parts (Component 4) 65% by weight ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Corporation): 11.54 parts (Component 5) 10% ethyl acetate solution of sulfonate surfactant (Paionin A-41-C, manufactured by Takemoto Oil & Fat Co., Ltd.): 4.42 parts

[0404] ~Aqueous phase components~ Distilled water: 46.87 parts

[0405] <Preparation of polymer particles R-2> -Preparation of oil phase components- 6.66 g of a polyfunctional isocyanate compound (PM-200: manufactured by Wanka Chemical Co., Ltd.), 5.46 g of a 50% by mass ethyl acetate solution of "Takenate (registered trademark) D-116N (an adduct of trimethylolpropane (TMP), m-xylylene diisocyanate (XDI), and polyethylene glycol monomethyl ether (EO90) (structure shown below))" manufactured by Mitsui Chemicals, Inc., 11.24 g of a 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer), 14.47 g of ethyl acetate, and 0.45 g of Paionin (registered trademark) A-41-C manufactured by Takemoto Oil & Fat Co., Ltd. were mixed and stirred at room temperature (25°C) for 15 minutes to obtain an oil phase component.

[0406] [ka]

[0407] -Preparation of aqueous phase components- As the aqueous phase component, 47.2 g of distilled water was prepared.

[0408] -Microcapsule formation process- The aqueous phase component was added to the oil phase component and mixed, and the resulting mixture was emulsified using a homogenizer at 12,000 rpm for 16 minutes to obtain an emulsion. To the resulting emulsion was added 16.8 g of distilled water, and the resulting liquid was stirred at room temperature for 10 minutes. The stirred liquid was then heated to 45°C and stirred for 4 hours while maintaining the liquid temperature at 45°C, thereby distilling off ethyl acetate from the liquid. Next, 5.12 g of a 10% by mass aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) was added, stirred at room temperature for 30 minutes, and allowed to stand at 45°C for 24 hours. The solids concentration was adjusted to 20% by mass with distilled water, yielding an aqueous dispersion of polymer particles R-2. The volume average particle size of R-2 was measured using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.) and found to be 165 nm.

[0409] <Preparation of Polymer Particles R-3> A four-neck flask was charged with 10.0 parts of the following compound B-1 (n=45) as a dispersion unit, 85.0 parts of distilled water, and 240.0 parts of n-propanol, and the mixture was heated and stirred at 70° C. under a nitrogen atmosphere. Next, a mixture of 20.0 parts of the following compound A-1, 70.0 parts of the following compound A-2, and 0.7 parts of 2,2'-azobisisobutyronitrile, which had been mixed in advance, was added dropwise to the four-neck flask over 2 hours. After the dropwise addition was completed, the reaction was continued for 5 hours, and then 0.5 parts of 2,2'-azobisisobutyronitrile was added, and the temperature was raised to 80° C. 0.4 parts of 2,2'-azobisisobutyronitrile was added every 6 hours, and the reaction was continued for a total of 19 hours. The reaction liquid was allowed to cool to room temperature (25° C.) to obtain a dispersion liquid of polymer particles R-3 (solid content 23%).

[0410] [ka]

[0411] The median diameter of the polymer particles R-3 was 150 nm, and the coefficient of variation was 23%. Furthermore, when the dispersibility of the polymer particles R-3 was confirmed by the method already described, it was found that the resin particles R-3 were particles that were dispersible in water and also in organic solvents.

[0412] <Preparation of Polymer Particles R-4> A three-neck flask was charged with 350 parts of distilled water, 50 parts of Compound A-1, 20 parts of Compound A-2, 20 parts of Compound A-3, and 10 parts of Compound B-1 (n=45), and the mixture was heated to 70°C under a nitrogen atmosphere. Next, 1.0 part of potassium persulfate (KPS) was added, and the mixture was heated and stirred for 3 hours, after which the mixture was heated to 95°C and reacted for 4 hours. The reaction solution was allowed to cool to room temperature (25°C), yielding an aqueous dispersion of polymer particles R-4 (solid content 22%). The average particle size of polymer particles R-4 was 142nm.

[0413] [ka]

[0414] <Preparation of Polymer Particles R-5> 288 parts of ion-exchanged water, 1.6 parts of sodium dodecylbenzenesulfonate, 0.5 parts of A-1, and 0.2 parts of A-2 were added to a three-neck flask, and the mixture was emulsified under stirring at 75° C. and 200 rpm for 15 minutes under a nitrogen atmosphere. 0.15 parts of potassium persulfate (KPS) and 7 parts of ion-exchanged water were added, and the mixture was heated and stirred at 80°C for 30 minutes. 24.7 parts of A-1, 12.8 parts of A-2, and 6.7 parts of A-4 were added dropwise over 3 hours, followed by stirring under heating for 1 hour. The reaction solution was allowed to cool to room temperature (25°C), yielding an aqueous dispersion of polymer particles R-5 (solid content 13%). The average particle size of the polymer particles R-5 was 40 nm.

[0415] [ka]

[0416] [ka]

[0417] <Formation of Overcoat Layer> The following overcoat layer coating solution (1) (wherein the overcoat layer coating solution (1) contains the components listed in Tables 5 to 8 and is prepared with ion-exchanged water so that the solid content is 6% by mass) was applied onto the image recording layer using a bar, and dried in an oven at 120°C for 60 seconds to form an overcoat layer with the dry coating amount listed in Tables 5 to 8.

[0418] The method for preparing the inorganic layer compound dispersion used in the overcoat layer coating solution (1) will be described below. <<Preparation of inorganic layered compound dispersion>> 6.4 parts of synthetic mica (Somasif ME-100, manufactured by Co-op Chemical Co., Ltd.) was added to 193.6 parts of ion-exchanged water, and the mixture was dispersed using a homogenizer until the average particle size (laser scattering method) reached 3 μm. The aspect ratio of the resulting dispersed particles was 100 or more.

[0419] [Color-changing compounds] wIR-1 to wIR-3: the following compounds

[0420] [ka]

[0421] [Hydrophilic polymer] WP-1: Polyvinyl alcohol, Mowiol 4-88 manufactured by Sigma-Aldrich WP-2: Polyvinyl alcohol, Mowiol 8-88 manufactured by Sigma-Aldrich WP-3: The following resin WP-4: Cellulose, Metrose 60SH-15 manufactured by Shin-Etsu Chemical Co., Ltd. WP-5: Polyvinyl alcohol, Mitsubishi Chemical Corporation's Gohsenol L-3266, saponification degree 86% to 89% or more WP-6: Cellulose, Metrose SM04 manufactured by Shin-Etsu Chemical Co., Ltd. WP-7: The following resin (Mw=30,000)

[0422] [ka]

[0423] [ka]

[0424] [Hydrophobic polymer] L-1: Polyvinylidene chloride aqueous dispersion, Diofan (registered trademark) A50 manufactured by Solvin L-2: Styrene-acrylic resin, FS-201 manufactured by Nippon Paint Industrial Coatings Co., Ltd. L-3: Styrene-acrylic resin, FS-102 manufactured by Nippon Paint Industrial Coatings Co., Ltd.

[0425] <Preparation of lithographic printing plate precursor> As shown in Tables 5 to 8, lithographic printing plate precursors of Examples 1 to 38 and Comparative Examples 1 to 6 were prepared according to the methods for forming the supports and the layers described above.

[0426] <Evaluation of lithographic printing plate precursors> The lithographic printing plate precursor prepared as described above was exposed (irradiation energy 110 mJ / cm) using a Kodak Magnus 800 Quantum equipped with an infrared semiconductor laser under the conditions of an output of 27 W, an outer drum rotation speed of 450 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch is 2.54 cm). 2 The exposure image included a solid image, an AM screen (Amplitude Modulation Screen) 3% halftone dot chart, and an FM screen (Frequency Modulation Screen) 20% halftone dot chart.

[0427] [On-press developability] The resulting exposed plate was mounted without development on the cylinder of a Heidelberg SX-74 printing press (Kikuban format). A 100 L dampening solution circulating tank with a built-in nonwoven fabric filter and temperature control device was connected to the press. Eighty liters of 2.0% dampening solution S-Z1 (Fujifilm Corporation) was charged into the circulating system, and T&K UV OFS K-HS Sumi GE-M (T&K TOKA Corporation) printing ink was used. After supplying the dampening solution 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. In the on-press development, the number of sheets of printing paper required until no ink was transferred to the non-image area was measured as on-press developability. The measurement results are shown in Tables 5 to 8. The lower the number of sheets, the better the on-press developability.

[0428] [UV-curable ink printing durability (UV printing durability)] After the evaluation of on-press developability described above, printing was continued. As the number of prints increased, the image area gradually wore away, resulting in a decrease in ink density on the prints. The number of prints when the dot area ratio of the 3% AM screen dots on the prints, measured using a Gretag densitometer (manufactured by GretagMacbeth), was 1% lower than the value measured on the 500th print, was defined as the number of prints completed, and printing durability was evaluated. Relative printing durability was evaluated, with 50,000 prints being set at 100. The higher the value, the better the printing durability. The evaluation results are shown in Tables 5 to 8. Relative printing durability = (number of prints made with the target lithographic printing plate precursor) / 50,000 x 100

[0429] [Ink receptivity (special color ink receptivity)] Printing was carried out in the same manner as for the UV printing durability test, except that the special ink Epple Pantone Blau 072C (Epple ink) was used. The 10,000th sheet of printed paper was sampled, and the ink density of the 20% FM halftone dot area was measured using a Gretag densitometer. Based on the measured values ​​(rounded to the second decimal place), the ink receptivity of the special ink was evaluated using the following index, as shown in Tables 5 to 8. -Evaluation criteria- A: Ink density 1.8-1.9: No decrease in ink density at all, good ink adhesion B: Ink density 1.5-1.7: Ink density is slightly reduced, but still within the acceptable range C: Ink density 1.0-1.4: The ink density has clearly decreased and is at an unacceptable level D: Ink density 0.9 or less: Ink density has decreased significantly

[0430] [Prevents turbidity of dampening water] After adjusting the water-ink balance using an adjustment plate (Fujifilm XP-F), 1,000 sheets were printed. After that, the adjustment plate was removed and the blanket was washed. Next, the ink fountain key was set to zero. The dampening water used during adjustment was discarded and new dampening water was added. At this time, the dampening water circulation system was stopped and the outlet was closed with a rubber stopper. Next, the following operations X1 to X3 were repeated 10 times. X1: The prepared lithographic printing plate precursor (unexposed plate) was subjected to manual pre-damping 50 times. X2: After 50 washings, 100 sheets were printed on Shiraoi (high-quality paper, manufactured by Nippon Paper Industries Co., Ltd.). X3: The plate was removed. The printing conditions are as follows: Printing machine: Lithrone printing machine LS26 / 104 manufactured by Komori Corporation Ink: UV ink (UV CORE TYPE-AJ yellow, manufactured by T&K TOKA Corporation) Dampening solution: PRESSMAX S-Z1 2% (Fujifilm Corporation) Pre-dampening: 50 times The rubber stopper was then removed, the dampening water was collected, and the turbidity was measured by measuring the transparency of the dampening water. The transparency was measured in accordance with JIS K0102 (2019) and evaluated according to the following criteria. The evaluation results are shown in Tables 5 to 8. -Evaluation criteria- A: Transparency 8cm or more B: Transparency 5cm or more but less than 8cm C: Transparency less than 5cm

[0431] [Table 5]

[0432] [Table 6]

[0433] [Table 7]

[0434] [Table 8]

[0435] Here, ΔE1 represents the value of LUMO of the electron-accepting polymerization initiator - LUMO of the infrared absorber, and ΔE2 represents the value of HOMO of the infrared absorber - HOMO of the electron-donating polymerization initiator. The results shown in Tables 5 to 8 show that the planographic printing plate precursors according to the Examples provide planographic printing plate precursors superior in UV printing durability, on-press developability, and suppression of turbidity of fountain solution compared to the planographic printing plate precursors according to the Comparative Examples. Furthermore, the planographic printing plate precursors according to the present disclosure provide planographic printing plates with excellent ink receptivity.

[0436] The disclosures of Japanese Patent Application No. 2021-012032, filed on January 28, 2021, and Japanese Patent Application No. 2021-061164, filed on March 31, 2021, 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]

[0437] 12a, 12b: aluminum support, 14: undercoat layer, 16: image recording layer, 18: aluminum plate, 20a, 20b: anodized film, 22a, 22b: micropores, 24: large diameter pore portion, 26: small diameter pore portion, D: depth of large diameter pore portion, 610: anodizing treatment device, 612: power supply tank, 614: electrolytic treatment tank, 616: aluminum plate, 618, 26: electrolyte, 620: power supply electrode, 622, 628: roller, 624: nip roller, 630: electrolytic electrode, 632: tank wall, 634: DC power source

Claims

1. a support, an image recording layer, and an overcoat layer in this order; the overcoat layer does not contain any inorganic compound, or the content of the inorganic compound is more than 0% by mass and less than 1% by mass with respect to the total mass of the overcoat layer; the image recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and an oil agent, The oil agent includes two or more oil agents having different structures. On-press development type lithographic printing plate precursor.

2. The on-press development type lithographic printing plate precursor according to claim 1, wherein the oil agent contains an oil agent having a boiling point of 300°C or higher.

3. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the oil agent has a clog P value of 5.0 or more.

4. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 3, wherein the oil agent contains an oil agent having an aromatic ring.

5. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 4, wherein the oil agent contains an oil agent having a phosphorus atom.

6. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 5, wherein the polymerization initiator comprises an electron-donating polymerization initiator.

7. The on-press development type lithographic printing plate precursor according to claim 6, wherein the electron-donating polymerization initiator is a borate compound.

8. 8. The on-press development type lithographic printing plate precursor according to claim 6, wherein a value of HOMO of the infrared absorber - HOMO of the electron-donating polymerization initiator is 0.70 eV or less.

9. the polymerization initiator comprises an electron-accepting polymerization initiator, The on-press development type lithographic printing plate precursor according to any one of claims 1 to 8, wherein a value of LUMO of the electron-accepting polymerization initiator - LUMO of the infrared absorber is 0.70 eV or less.

10. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 9, wherein the polymerizable compound comprises a polymerizable compound having seven or more functionalities.

11. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 10, wherein the polymerizable compound comprises a polymerizable compound having 10 or more functionalities.

12. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 11, wherein the image recording layer further contains polymer particles.

13. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 12, wherein the overcoat layer contains a hydrophilic polymer.

14. The on-press development type lithographic printing plate precursor according to claim 13, wherein the hydrophilic polymer comprises a cellulose derivative.

15. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 14, wherein the polymerizable compound comprises a polymerizable compound having two or fewer functionalities.

16. The on-press development type lithographic printing plate precursor according to claim 9, wherein the electron-accepting polymerization initiator comprises a compound represented by the following formula (II): 【Chemistry 1】 In formula (II), X Ａ represents a halogen atom, R Ａ represents an aryl group.

17. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 16, wherein the image recording layer further contains polyvinyl butyral.

18. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 17, wherein the overcoat layer contains a hydrophobic polymer.

19. The on-press development type lithographic printing plate precursor according to claim 18, wherein the hydrophobic polymer is a hydrophobic polymer particle.

20. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 19, wherein the overcoat layer further contains a color-changing compound.

21. The on-press developable lithographic printing plate precursor according to claim 20, wherein the color-changing compound comprises a decomposable compound that decomposes upon exposure to infrared light.

22. The on-press development type lithographic printing plate precursor according to claim 20 or 21, wherein the color-changing compound is a cyanine dye.

23. The on-press development type lithographic printing plate precursor according to any one of claims 20 to 22, 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 2-1 to 4-1, 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 represents R ａ ~R ｅ each independently represents a hydrocarbon group; 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; n １１ and n １２ each independently represents an integer of 0 to 5, provided that n １１ and n １２ The sum of n is 2 or more, １３ and n １４ each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or —NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge. 【Transformation 3】 In formulas 2-1 to 4-1, 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 the bonding site with the group represented by L in formula 1-1.

24. The on-press development type lithographic printing plate precursor according to any one of claims 20 to 23, wherein the color-changing compound is a compound represented by the following formula 1-2: 【Chemistry 4】 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 represents R ２３ and R ２４ are each independently a hydrogen atom or -R ａ represents 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 -, and 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.

25. The on-press development type lithographic printing plate precursor according to any one of claims 20 to 24, wherein the color-changing compound is a compound represented by any one of the following formulas 1-3 to 1-7: 【Transformation 5】 In formulas 1-3 to 1-7, R １ represents a group represented by any one of the above formulas 2-1 to 4-1, 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 represents R ２５ and R ２６ are each independently a hydrogen atom, a halogen atom, or -R ａ represents 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 -, and 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.

26. W in the formulas 1-2 to 1-7 １ and W ２ are each independently a substituted alkyl group, and the substituent is —OCH ２ CH ２ The on-press development type lithographic printing plate precursor according to claim 25, wherein the aryl group is a group having at least one of a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group.

27. a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 26; and a step of supplying at least one selected from the group consisting of printing ink and dampening water on the printing press to remove the image recording layer in the non-image areas.

28. a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 26; 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 the non-image area on the printing press to prepare a lithographic printing plate; and printing with the resulting lithographic printing plate.

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