On-press-development-type planographic printing plate precursor, method for fabricating planographic printing plate, and planographic printing method

Abstract

Provided is an on-press-development-type planographic printing plate precursor comprising a substrate and an image recording layer on the substrate, wherein: the image recording layer contains a polymerizable compound and polymer particles; the median diameter of the polymer particles is 50-120 nm; the content of the polymer particles is 42-90 mass% with respect to the total mass of the image recording layer; and, in a cross-section image obtained by performing an osmium staining treatment on a thickness direction cross-section of the planographic printing plate precursor, subsequently obtaining a cross-section image by observing the cross-section with a scanning electron microscope, and binarizing said cross-section image into stained parts and non-stained parts, the standard deviation of the area ratio of the non-stained parts is less than 6. Also provided are a method for fabricating a planographic printing plate and a planographic printing method which use the on-press-development-type planographic printing plate precursor.

Description

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

[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.

[0002] Generally, a lithographic printing plate comprises an oleophilic image area that accepts ink during the printing process and a hydrophilic non-image area that accepts fountain solution. Lithographic printing utilizes the mutual repulsion of water and oil-based ink, with the oleophilic image area of ​​the lithographic printing plate serving as the ink-receptive area and the hydrophilic non-image area serving as the fountain solution-receptive area (ink-non-receptive area), creating a difference in ink adhesion on the surface of the lithographic printing plate. After ink is applied only to the image area, the ink is transferred to a substrate such as paper for printing. To prepare such lithographic printing plates, a lithographic printing plate precursor (PS plate) comprising an oleophilic photosensitive resin layer (image-recording layer) provided on a hydrophilic support has been widely used. Typically, a lithographic printing plate precursor is exposed to light through an original image such as a lithographic film, and then the image areas of the image recording layer are left, while the other unnecessary image recording layer is dissolved and removed with an alkaline developer or an organic solvent, exposing the hydrophilic support surface and forming non-image areas, thereby producing a lithographic printing plate.

[0003] Furthermore, growing concern about the global environment has focused attention on environmental issues related to wastewater from wet processes such as development. To address these environmental issues, efforts are being made to simplify development or platemaking, or to eliminate such processes. One simple production method is known as "on-press development." This method involves exposing a lithographic printing plate precursor to light, without the conventional development process, and directly mounting the plate on a printing press, and removing unnecessary portions of the image-recording layer 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] Examples of conventional lithographic printing plate precursors include those described in Patent Documents 1 and 2. Patent Document 1 discloses a lithographic printing plate precursor having an aluminum support and an image recording layer formed on the aluminum support, the image recording layer containing resin particles A having an ethylenically unsaturated group and a compound B other than the resin particles A having an ethylenically unsaturated group, and having an ethylenically unsaturated bond valence of 1.5 mmol / g or more.

[0005] Patent Document 2 discloses particles for an on-press development type lithographic printing plate precursor, which are particles containing a resin having a structural unit formed from an aromatic vinyl compound and a structural unit formed from an acrylonitrile compound, and the particles are particles that have been particulated with a surfactant, and an on-press development type lithographic printing plate precursor in which an image recording layer contains the particles for the on-press development type lithographic printing plate precursor.

[0006] Patent Document 1: International Publication No. 2020 / 262694 Patent Document 2: International Publication No. 2020 / 026809

[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 printing durability and development residue suppression.An object of another embodiment of the present disclosure is to provide a method for producing a lithographic printing plate using the on-press development type lithographic printing plate precursor, or a lithographic printing method.

[0008] Means for solving the above problems include the following aspects: <1> An on-press developable lithographic printing plate precursor having a support and an image recording layer on the support, the image recording layer containing a polymerizable compound and polymer particles, the polymer particles having a median diameter of 50 nm to 120 nm, and a content of the polymer particles of 42% by mass or more and 90% by mass or less relative to the total mass of the image recording layer, and wherein a cross-section of a thickness direction cross-section of the lithographic printing plate precursor is stained with osmium and then observed with a scanning electron microscope, and the cross-section image is binarized into dyed and undyed portions, and the standard deviation of the area ratio of the undyed portions in the cross-section image is less than 6. <2> The on-press existing lithographic printing plate precursor according to <1>, wherein the polymer particles are polymer particles having a structural unit formed from an acrylonitrile compound and a polyalkylene oxide structure. <3> The on-press developable lithographic printing plate precursor according to <2>, wherein the polymer particles are polymer particles having a structural unit formed by an aromatic vinyl compound, a structural unit formed by an acrylonitrile compound, and a structural unit having a polyalkylene oxide structure. <4> The on-press developable lithographic printing plate precursor according to <2> or <3>, wherein the polyalkylene oxide structure is a polyethylene oxide structure. <5> The on-press developable lithographic printing plate precursor according to any one of <2> to <4>, wherein the number of repeating units of the polyalkylene oxide structure is 3 to 10. <6> The on-press developable lithographic printing plate precursor according to any one of <2> to <5>, wherein the content of the structural unit having a polyalkylene oxide structure in the polymer particles is 10% by mass or more relative to the total mass of the polymer. <7> The on-press developable lithographic printing plate precursor according to any one of <1> to <6>, wherein the content of the polymer particles is 45% by mass or more relative to the total mass of the image recording layer. <8> The on-press development type lithographic printing plate precursor according to <7>, wherein the content of the polymer particles is 55% by mass or more relative to the total mass of the image recording layer. <9> The on-press development type lithographic printing plate precursor according to any one of <1> to <8>, wherein the polymer particles have a median diameter of 50 nm to 100 nm. <10> The on-press development type lithographic printing plate precursor according to <9>, wherein the polymer particles have a median diameter of 50 nm to 90 nm.<11> The on-press developable lithographic printing plate precursor according to any one of <1> to <10>, wherein the polymerizable compound comprises an oligomer. <12> The on-press developable lithographic printing plate precursor according to any one of <1> to <11>, further comprising an intermediate layer between the support and the image recording layer, the intermediate layer comprising a copolymer polymer having a support-adsorbing group and a hydrophilic group. <13> The on-press developable lithographic printing plate precursor according to any one of <1> to <12>, further comprising an overcoat layer on the image recording layer containing an inorganic stratiform compound. <14> The on-press developable lithographic printing plate precursor according to any one of <1> to <13>, further comprising an overcoat layer on the image recording layer containing a water-soluble polymer, the overcoat layer being thicker than the image recording layer. <15> The on-press development type lithographic printing plate precursor according to any one of <1> to <14>, which has an oxide film on the surface of the support, the oxide film having micropores extending in the depth direction from the surface of the oxide film on the image recording layer side, the micropores having large-diameter pores on the surface of the oxide film having an average pore diameter of 15 nm to 100 nm, and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend further in the depth direction from the communicating positions, the small-diameter pores having an average pore diameter of 15 nm or less. <16> The on-press development type lithographic printing plate precursor according to any one of <1> to <15>, which has an oxide film on the surface of the support, the oxide film having micropores that extend in the depth direction from the surface of the oxide film on the image recording layer side, the maximum diameter inside the micropores being 1.2 to 10 times the average pore diameter at the surface of the oxide film. <17> An on-press developable lithographic printing plate precursor comprising a support and an image recording layer on the support, the image recording layer containing a polymerizable compound and polymer particles, the polymer particles having a median diameter of 50 nm to 120 nm, a content of the polymer particles of 42% by mass or more and 90% by mass or less relative to the total mass of the image recording layer, and the polymer particles containing 65% by mass or more of structural units formed by an acrylonitrile compound and 10% by mass or more of structural units having a polyalkylene oxide structure relative to the total mass of the polymer particles.<18> A method for producing a lithographic printing plate, comprising: a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of <1> to <17>, 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. <19> A lithographic printing method, comprising: a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of <1> to <17>, 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 to produce a lithographic printing plate, and a step of printing with the obtained lithographic printing plate.

[0009] 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 printing durability and development residue suppression. According to another embodiment of the present disclosure, it is possible to provide a method for producing a lithographic printing plate using the on-press development type lithographic printing plate precursor, or a lithographic printing method.

[0010] Fig. 1 is a schematic cross-sectional view of one embodiment of a support; Fig. 2 is a schematic cross-sectional view of another embodiment of a support; Fig. 3 is a schematic view of an anodizing treatment apparatus used in anodizing treatment in a method for producing a support having an anodized film; Fig. 4 is a side view showing the concept of a brush graining process used in mechanical graining treatment in the production of an aluminum support; Fig. 5 is a graph showing an example of an alternating current waveform diagram used in electrochemical graining treatment; Fig. 6 is a side view showing an example of a radial cell in electrochemical graining treatment using alternating current;

[0011] The contents of the present disclosure will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment. In the present disclosure, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after the term are included as the lower and upper limits. Furthermore, in the notation of groups (atomic groups) in the present disclosure, notations that do not indicate substituted or unsubstituted encompass both unsubstituted and substituted groups. For example, the term "alkyl group" encompasses not only unsubstituted alkyl groups (unsubstituted alkyl groups) but also substituted alkyl groups (substituted alkyl groups). In the present disclosure, "(meth)acrylic" is a term used to encompass both acrylic and methacrylic groups, and "(meth)acryloyl" is a term used to encompass both acryloyl and methacryloyl groups. The term "process" in the present disclosure includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In the present disclosure, "mass %" and "wt %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Unless otherwise specified, in the present disclosure, each component in the composition or each structural unit in the polymer may be contained alone or in combination of two or more types. In the present disclosure, when a plurality of substances or structural units corresponding to each component or each structural unit in the polymer is present in the composition, the amount of each component in the composition or each structural unit in the polymer means the total amount of the corresponding plurality of substances present in the composition or the corresponding plurality of structural units present in the polymer, unless otherwise specified. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.Unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in this disclosure are molecular weights measured by a gel permeation chromatography (GPC) analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) in THF (tetrahydrofuran) as a solvent, detected by a differential refractometer, and converted using polystyrene as a standard. In this disclosure, the term "lithographic printing plate precursor" encompasses not only lithographic printing plate precursors but also disposable plate precursors. The term "lithographic printing plate" encompasses not only lithographic printing plates prepared from lithographic printing plate precursors, if necessary, through procedures such as exposure and development, but also disposable plates. In the case of disposable plate precursors, exposure and development procedures are not necessarily required. It should be noted that a throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when, for example, a portion of a page is printed in one color or two colors in color newspaper printing. In the present disclosure, "*" in a chemical structural formula indicates a bonding position with other structures.

[0012] <On-press development type lithographic printing plate precursor> A first embodiment of an 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 and an image recording layer on the support, the image recording layer containing a polymerizable compound and polymer particles, the median diameter of the polymer particles being 50 nm to 120 nm, the content of the polymer particles being 42 mass % or more and 90 mass % or less with respect to the total mass of the image recording layer, and the standard deviation of the area ratio of the undyed portion of a cross-section image obtained by subjecting a cross-section in the thickness direction of the lithographic printing plate precursor to an osmium staining treatment and then observing the cross-section image with a scanning electron microscope and binarizing the dyed and undyed portions is less than 6. A second embodiment of the on-press development type lithographic printing plate precursor according to the present disclosure comprises a support and an image recording layer on the support, the image recording layer containing a polymerizable compound and polymer particles, the polymer particles having a median diameter of 50 nm to 120 nm, a content of the polymer particles being 42% by mass or more but not more than 90% by mass, relative to the total mass of the image recording layer, and the polymer particles having, relative to the total mass of the polymer particles, 65% by mass or more of structural units formed by an acrylonitrile compound and 10% by mass or more of structural units having a polyalkylene oxide structure.

[0013] In this specification, unless otherwise specified, simply referring to "an on-press development type lithographic printing plate precursor according to the present disclosure" or "a lithographic printing plate precursor according to the present disclosure" refers to both the first embodiment and the second embodiment. Furthermore, unless otherwise specified, simply referring to an "image recording layer" or the like refers to both the image recording layer or the like of the first embodiment and the second embodiment.

[0014] In conventional on-press development type lithographic printing plate precursors, when small particle size polymer particles with a median diameter of 50 nm to 120 nm are contained in the image recording layer, the small particle size polymer particles tend to aggregate, resulting in an image recording layer in which many polymer particle aggregates are observed. Furthermore, even if an attempt is made to contain a large number of polymer particles in the image recording layer from the viewpoint of improving printing durability, many of the above aggregates similarly occur, and the above aggregates tend to accumulate as development residue. Furthermore, in the areas where the above aggregates occur, the strength of the image recording layer decreases, and printing durability and development residue suppression properties are insufficient. In a first embodiment of the lithographic printing plate precursor according to the present disclosure, the image recording layer comprises a polymerizable compound and polymer particles, the polymer particles have a median diameter of 50 nm to 120 nm, the content of the polymer particles is 42% by mass or more and 90% by mass or less, relative to the total mass of the image recording layer, and a cross-section of the thickness direction of the lithographic printing plate precursor is subjected to an osmium staining treatment, and then the cross-section image obtained by observing the cross-section with a scanning electron microscope and binarizing the dyed and undyed portions has a standard deviation of less than 6 for the undyed portions. This presumably makes it possible to provide an on-press development type lithographic printing plate precursor having excellent printing durability and development residue suppression properties, even in an image forming layer containing a large number of small particle diameter polymer particles, in which aggregation of the polymer particles is suppressed and the image recording layer has high polymer particle dispersibility and high uniformity.

[0013] Furthermore, in a second embodiment of the lithographic printing plate precursor according to the present disclosure, the image recording layer comprises a polymerizable compound and polymer particles, the polymer particles having a median diameter of 50 nm to 120 nm, the content of the polymer particles being 42% by mass or more and 90% by mass or less, relative to the total mass of the image recording layer, and the polymer particles having 65% by mass or more of structural units formed by an acrylonitrile compound and 10% by mass or more of structural units having a polyalkylene oxide structure, relative to the total mass of the polymer particles, thereby suppressing aggregation of the polymer particles, and providing an image recording layer with high dispersibility and uniformity of the polymer particles, even in an image forming layer containing a large number of small particle diameter polymer particles, and it is presumed that an on-press development type lithographic printing plate precursor excellent in printing durability and development residue suppression can be provided.

[0015] Hereinafter, each constituent element of the planographic printing plate precursor according to the present disclosure will be described in detail.

[0016] (Standard Deviation of Undyed Portions) In a first embodiment of the on-press development type lithographic printing plate precursor according to the present disclosure, a cross-section of the thickness direction of the lithographic printing plate precursor is subjected to an osmium staining treatment, and then the cross-section image obtained by observing the cross-section with a scanning electron microscope is binarized into dyed and undyed portions. The standard deviation of the area ratio of the undyed portions in the cross-section image is less than 6, and from the viewpoints of printing durability and development residue suppression, is preferably less than 5.1, and more preferably less than 4.2. A smaller standard deviation means that the non-polymerizable portions are more uniformly present in the film, resulting in better printing durability and development residue suppression. Furthermore, in a second embodiment of the on-press development type lithographic printing plate precursor according to the present disclosure, a cross-section of the thickness direction of the lithographic printing plate precursor is subjected to an osmium staining treatment, and then the cross-section image obtained by observing the cross-section with a scanning electron microscope is binarized into dyed and undyed portions. From the viewpoints of printing durability and suppression of development residue, the standard deviation of the area ratio of the undyed portions in the cross-section image is preferably less than 6, more preferably less than 5.1, and particularly preferably less than 4.2. A specific means for obtaining a lithographic printing plate precursor with a small standard deviation is to increase the dispersibility of polymer particles contained in the image recording layer. As particles with good dispersibility, polymer particles having a pendant group containing a hydrophilic poly(alkylene oxide) segment are preferred, as will be described in detail below.

[0017] In the present disclosure, the method for measuring the standard deviation of the non-stained portion is as follows.

[0018] -Osmium dyeing method- A lithographic printing plate precursor is cut into pieces of approximately 10 mm square, and is subjected to vapor dyeing using a 2% by mass aqueous solution of osmic acid at approximately 22°C for 24 hours.

[0019] -Scanning electron microscope (SEM) observation method- After osmium staining, a cross section was exposed using an argon (Ar) ion beam, followed by a conductive treatment with a carbon coat, and backscattered electron observation was performed using a semi-in-lens SEM manufactured by Hitachi High-Tech Corporation at an accelerating voltage of 5 kV. Images were taken at a magnification of 50,000x with N = 10 fields of view. The image processing software ImageJ (Fiji) was used to binarize the stained and unstained portions of the obtained cross-sectional SEM image. From the obtained cross-sectional SEM image, an image recording layer was selected, and noise was filtered using a median filter (2 pixels), followed by binarization (therehold). The therehold threshold was set to Auto (Li). After noise was filtered from the obtained binarized image using a median filter (2 pixels), the area ratio of the unstained portion was measured. The standard deviation of the area ratio of the non-stained area is calculated from data of N=10 fields of view.

[0020] Osmium staining is a method in which osmium binds to an ethylenically unsaturated bond contained in a polymerizable compound, and the backscattered electrons at the stained portion are increased by the osmium, which has a large atomic number, making it possible to clearly observe the stained portion. The stained portion (polymerizable compound) appears white in the cross-sectional image taken by SEM, and the unstained portion (polymer particles and other non-polymerizable additives) appears black in the cross-sectional image taken by SEM.

[0021] (Image Recording Layer) The image recording layer in the lithographic printing plate precursor according to the present disclosure is preferably a water-soluble or water-dispersible negative image recording layer. From the viewpoint of on-press developability, it is also preferable that the unexposed portion of the image recording layer in the lithographic printing plate precursor according to the present disclosure is removable with at least one of fountain solution and printing ink.

[0022] Each component contained in the image recording layer will be described in detail below.

[0023] [Polymer Particles] The image recording layer contains polymer particles. The polymer particles contribute to improving printing durability and on-press developability. The polymer particles are preferably polymer particles that can convert the image recording layer to a hydrophobic state when heat is applied. The polymer particles are preferably at least one selected from the group consisting of hydrophobic thermoplastic polymer particles and microcapsules encapsulating a hydrophobic compound, with hydrophobic thermoplastic polymer particles being particularly preferred.

[0024] Specific examples of polymers constituting the hydrophobic thermoplastic polymer particles include homopolymers or copolymers of monomers such as ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, and acrylates or methacrylates having a polyalkylene structure, or mixtures thereof.

[0025] Examples of microcapsules include those in which all or part of the components of the image recording layer are encapsulated in microcapsules, as described in JP-A Nos. 2001-277740 and 2001-277742. The components of the image recording layer can also be contained outside the microcapsules. A preferred embodiment of the image recording layer containing microcapsules is one in which hydrophobic components are encapsulated in microcapsules and hydrophilic components are contained outside the microcapsules.

[0026] The median diameter of the polymer particles is 50 nm to 120 nm, and from the viewpoints of printing durability and suppression of development residue, it is preferably 50 nm to 100 nm, and more preferably 50 nm to 90 nm. The smaller the polymer particle diameter, the better the printing durability.

[0027] In the present disclosure, the median diameter of polymer particles is measured by dynamic light scattering. When the polymer particles are isolated from the plate and the particle size is measured, the obtained polymer particles are redispersed in a solvent by the following method, and then the particle size is measured.

[0028] -Method of isolating polymer particles from plate- A plate coated with an image recording layer is immersed in a mixed solvent A of 2-butanone / 1-methoxy-2-propanol / methanol / pure water (40 / 30 / 20 / 10) and ultrasonicated for 10 seconds to prepare a dispersion of the image recording layer. The dispersion is then centrifuged at 5,000 rpm for 10 minutes to obtain precipitate B at the bottom of the container. After discarding the supernatant, mixed solvent A is added again to re-disperse the precipitate, and the mixture is centrifuged at 5,000 rpm for 10 minutes to obtain precipitate C at the bottom of the container. After discarding the supernatant, precipitate C is vacuum-dried (50°C for 16 hours) to obtain a powder of polymer particles. The median diameter of the polymer particles may also be measured by calculation from images obtained with a semi-in-lens SEM. A specific measurement method is shown below. The obtained polymer particle powder is scattered and fixed on carbon tape, then subjected to a conductive treatment, and observed at an accelerating voltage of 2 kV using a semi-in-lens SEM manufactured by Hitachi High-Tech Corporation. The image is taken at a magnification of 100,000x. The number of fields of view taken is N = 15 or more (the number of images that will extract 400 or more particles, as described below). In the captured image, all polymer particles that do not overlap and whose outlines can be determined are extracted as much as possible, and the particle size of each is measured. The median diameter is calculated from the obtained particle sizes (400 or more).

[0029] The polymer particles may be used alone or in combination of two or more types. The content of the polymer particles in the lithographic printing plate precursor according to the present disclosure is 42% by mass or more and 90% by mass or less, relative to the total mass of the image recording layer, and from the viewpoints of printing durability and suppression of development residue, it is preferably 45% by mass or more and more preferably 55% by mass or more. Furthermore, from the viewpoints of printing durability and suppression of development residue, the content of the polymer particles in the lithographic printing plate precursor according to the present disclosure is preferably 45% by mass to 85% by mass and more preferably 55% by mass to 75% by mass, relative to the total mass of the image recording layer.

[0030] In a preferred embodiment, the hydrophobic thermoplastic polymer particles have a hydrophobic main chain and preferably contain both i) a structural unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a structural unit having a pendant group containing a hydrophilic poly(alkylene oxide) segment. The hydrophobic main chain is preferably an acrylic resin chain. Examples of the pendant cyano group include -[CH ２ CH(C≡N)-] or -[CH ２ C(CH ３ )(C≡N)—] is preferred. The structural unit having a pendant cyano group can be easily derived from an ethylenically unsaturated monomer, such as acrylonitrile or methacrylonitrile, or a combination thereof. The alkylene oxide in the hydrophilic poly(alkylene oxide) segment is preferably ethylene oxide or propylene oxide, and more preferably ethylene oxide.

[0031] The number of repeating units of the alkylene oxide structure in the hydrophilic poly(alkylene oxide) segment is preferably 2 to 100, more preferably 3 to 55, and particularly preferably 3 to 10.

[0032] Preferred examples of resin particles having a hydrophobic main chain and including both i) a constituent unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a constituent unit having a pendant group containing a hydrophilic poly(alkylene oxide) segment include those described in paragraphs 0039 to 0068 of JP-A No. 2008-503365.

[0033]

[0023] In a second embodiment of the lithographic printing plate precursor according to the present disclosure, the polymer particles are polymer particles having, relative to the total mass of the polymer particles, 65% by mass or more of structural units formed by an acrylonitrile compound and 10% by mass or more of structural units having a polyalkylene oxide structure, and from the viewpoints of printing durability and suppression of development residue, it is preferable that the polymer particles further have structural units formed by an aromatic vinyl compound. Furthermore, from the viewpoints of printing durability and suppression of development residue, the polymer particles in a first embodiment of the lithographic printing plate precursor according to the present disclosure are preferably polymer particles having structural units formed by an acrylonitrile compound and structural units having a polyalkylene oxide structure, and more preferably polymer particles having structural units formed by an aromatic vinyl compound, structural units formed by an acrylonitrile compound, and structural units having a polyalkylene oxide structure. Furthermore, in a first embodiment of the lithographic printing plate precursor according to the present disclosure, the polymer particles are polymer particles that, from the viewpoint of printing durability and development residue suppression, have, relative to the total mass of the polymer particles, 65% by mass or more of structural units formed from an acrylonitrile compound and 10% by mass or more of structural units having a polyalkylene oxide structure; and polymer particles having structural units formed from an acrylonitrile compound and structural units having a polyalkylene oxide structure, and polymer particles having structural units formed from an aromatic vinyl compound, structural units formed from an acrylonitrile compound, and structural units having a polyalkylene oxide structure are hydrophobic thermoplastic polymer particles, unless otherwise specified.

[0034] Examples of the acrylonitrile compound include acrylonitrile and methacrylonitrile, with acrylonitrile being preferred.

[0035] Examples of aromatic vinyl compounds include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene, with styrene being preferred.

[0036] For polymer particles having structural units formed from an aromatic vinyl compound and structural units formed from an acrylonitrile compound, the composition ratio (mass ratio) of the structural units formed from the aromatic vinyl compound to the structural units formed from the acrylonitrile compound is preferably 10:1 to 1:10.

[0037] From the viewpoints of on-press developability, printing durability, and development residue suppression, the polyalkylene oxide structure in the structural unit having a polyalkylene oxide structure is preferably a polyethylene oxide structure, a polypropylene oxide structure, or a polyethylene / propylene oxide structure, and more preferably a polyethylene oxide structure. From the viewpoints of on-press developability, printing durability, and development residue suppression, the number of repeating units of the alkylene oxide structure in the polyalkylene oxide structure is preferably 2 to 100, and more preferably 3 to 55.

[0038] In a first embodiment of the lithographic printing plate precursor according to the present disclosure, the content of structural units formed by an acrylonitrile compound in the polymer particles is preferably 20% by mass to 95% by mass, more preferably 50% by mass to 95% by mass, even more preferably 70% by mass to 90% by mass, and particularly preferably 75% by mass to 90% by mass, relative to the total mass of the polymer having structural units having a cyano group, from the viewpoints of printing durability and development residue suppression. In a second embodiment of the lithographic printing plate precursor according to the present disclosure, the content of structural units formed by an acrylonitrile compound in the polymer particles is 65% by mass or more, and from the viewpoints of printing durability and development residue suppression, the content is preferably 70% by mass to 95% by mass, more preferably 70% by mass to 90% by mass, and particularly preferably 75% by mass to 90% by mass, relative to the total mass of the polymer having structural units having a cyano group.

[0039] In a first embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural unit having a polyalkylene oxide structure in the polymer particles is preferably 1% by mass to 50% by mass, more preferably 5% by mass to 30% by mass, even more preferably 8% by mass to 25% by mass, and particularly preferably 10% by mass to 20% by mass, relative to the total mass of the polymer particles, from the viewpoints of dispersibility, printing durability, and development residue suppression. In a second embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural unit having a polyalkylene oxide structure in the polymer particles is 10% by mass or more, and from the viewpoints of dispersibility, printing durability, and development residue suppression, the content is preferably 10% by mass to 50% by mass, more preferably 10% by mass to 30% by mass, even more preferably 10% by mass to 25% by mass, and particularly preferably 10% by mass to 20% by mass, relative to the total mass of the polymer particles.

[0040] In a first embodiment of the lithographic printing plate precursor according to the present disclosure, the content of structural units formed by an aromatic vinyl compound in the polymer particles is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 5% by mass to 20% by mass, relative to the total mass of the polymer particles, from the viewpoints of printing durability and development residue suppression. In a second embodiment of the lithographic printing plate precursor according to the present disclosure, the content of structural units formed by an aromatic vinyl compound in the polymer particles is preferably 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 5% by mass to 20% by mass, relative to the total mass of the polymer particles, from the viewpoints of printing durability and development residue suppression.

[0041] From the viewpoint of printing durability and chemical resistance, the polymer particles may have a structural unit formed from an N-vinyl heterocyclic compound. Examples of the N-vinyl heterocyclic compound include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylimidazole, and N-vinylpyrrolidone is preferred.

[0042] In a first embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural units formed by the N-vinyl heterocyclic compound in the polymer particles 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 polymer particles, from the viewpoints of printing durability and chemical resistance. In a second embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural units formed by the N-vinyl heterocyclic compound in the polymer particles is preferably 5% by mass to 25% by mass, and more preferably 10% by mass to 20% by mass, relative to the total mass of the polymer particles, from the viewpoints of printing durability and chemical resistance.

[0043] The polymer 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 polymer particles do not contain a structural unit having an acidic group. Specifically, the content of the structural unit having an acidic group in the thermoplastic resin is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The lower limit of the content is not particularly limited and may be 0% by mass. Furthermore, the acid value of the thermoplastic resin is preferably 160 mg KOH / g or less, more preferably 80 mg KOH / g or less, and even more preferably 40 mg KOH / g or less. The lower limit of the acid value is not particularly limited and may be 0 mg KOH / g. In the present disclosure, the acid value is determined by a measurement method in accordance with JIS K0070:1992.

[0044] From the viewpoint of ink receptivity, the polymer 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. The structural unit containing a hydrophobic group is preferably a structural unit formed from an alkyl(meth)acrylate compound, an aryl(meth)acrylate compound, or an aralkyl(meth)acrylate compound, and more preferably a structural unit formed from an alkyl(meth)acrylate compound. The alkyl group in the alkyl(meth)acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched, or may have a cyclic structure. Examples of the alkyl(meth)acrylate compound include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and dicyclopentanyl(meth)acrylate. The aryl group in the aryl(meth)acrylate compound preferably has 6 to 20 carbon atoms, and more preferably is a phenyl group. The aryl group may have a known substituent. A preferred example of the aryl (meth)acrylate compound is phenyl (meth)acrylate. The alkyl group in the aralkyl (meth)acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched, or may have a cyclic structure. The aryl group in the aralkyl (meth)acrylate compound preferably has 6 to 20 carbon atoms, and is more preferably a phenyl group. A preferred example of the aralkyl (meth)acrylate compound is benzyl (meth)acrylate.

[0045] In the polymer particles of a first embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural unit having a hydrophobic group 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 polymer particles. In the second embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural unit having a hydrophobic group is preferably 5% by mass to 25% by mass, and more preferably 10% by mass to 20% by mass, relative to the total mass of the polymer particles.

[0046] From the viewpoint of printing durability and on-press developability, the resin contained in the polymer particles may have a hydrophilic group other than a polyalkylene oxide structure. The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxy group, a hydroxy group, and an amino group.

[0047] In a first embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural unit having a hydrophilic group other than a polyalkylene oxide structure in the polymer particles is preferably 1% by mass to 60% by mass, and more preferably 5% by mass to 30% by mass, relative to the total mass of the polymer particles. In a second embodiment of the lithographic printing plate precursor according to the present disclosure, the content of the structural unit having a hydrophilic group other than a polyalkylene oxide structure in the polymer particles is preferably 1% by mass to 25% by mass, and more preferably 5% by mass to 20% by mass, relative to the total mass of the polymer particles.

[0048] The method for producing the resin contained in the polymer particles is not particularly limited, and the resin can be produced by a known method. For example, the resin can be obtained by polymerizing a styrene compound, an acrylonitrile compound, and, if necessary, at least one compound selected from the group consisting of the N-vinyl heterocyclic compound, the compound used to form the structural unit having an acidic group, the compound used to form the structural unit having a hydrophobic group, and the compound used to form the other structural unit, by a known method. Furthermore, the polyalkylene oxide structure can be introduced by using a monomer having a polyalkylene oxide structure, or by a polymer reaction.

[0049] Specific examples of resins contained in the polymer particles are shown in the table below, but the resins used in the present disclosure are not limited to these.

[0050]

[0051]

[0052] In the above specific examples, the content ratio of each structural unit can be appropriately changed in accordance with the preferred range of the content of each structural unit described above. In addition, the weight average molecular weight of each compound shown in the above specific examples can be appropriately changed in accordance with the preferred range of the weight average molecular weight of the thermoplastic resin described above.

[0053] [Polymerizable Compound] The image recording layer 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.

[0054] The polymerizable compound 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, and 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, trimer, or oligomer, or a mixture thereof. Among these, from the viewpoint of printing durability, the polymerizable compound preferably contains a trifunctional or higher functional polymerizable compound, more preferably a heptafunctional or higher functional polymerizable compound, and even more preferably a decafunctional or higher functional polymerizable compound. Furthermore, from the viewpoint of printing durability of the resulting lithographic printing plate, the polymerizable compound preferably contains a trifunctional or higher functional ethylenically unsaturated compound (preferably a heptafunctional or higher functional compound, more preferably a decafunctional or higher functional (meth)acrylate compound).

[0055] From the viewpoints of on-press developability and stain suppression, the polymerizable compound preferably contains a difunctional or lower polymerizable compound, more preferably a difunctional polymerizable compound, and particularly preferably a difunctional (meth)acrylate compound. From the viewpoints of printing durability, on-press developability, and stain suppression, the content of the difunctional or lower polymerizable compound (preferably a bifunctional polymerizable compound) is preferably 5% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, and particularly preferably 15% by mass to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0056] -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 distribution is present) of 600 or more and 10,000 or less and containing at least one polymerizable group. From the viewpoint of excellent chemical resistance and printing durability, the molecular weight of the oligomer is preferably 1,000 or more and 5,000 or less.

[0057] Furthermore, from the viewpoint of improving printing durability, the number of polymerizable groups in one molecule of the oligomer is preferably 2 or more, more preferably 3 or more, even more preferably 6 or more, and particularly preferably 10 or more. Furthermore, 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.

[0058] From the viewpoints of printing durability and on-press developability, the oligomer preferably has 7 or more polymerizable groups and a molecular weight of 1,000 to 10,000, and more preferably has 7 or more polymerizable groups and a molecular weight of 1,000 to 5,000. The oligomer may contain polymer components that may be generated during the production process of the oligomer.

[0059] From the viewpoints of 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.

[0060] The compound having a urethane bond, which is an example of the oligomer, is preferably, for example, a compound having at least a group represented by the following formula (Ac-1) or formula (Ac-2), and more preferably a compound having at least a group represented by the following formula (Ac-1).

[0061]

[0062] 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 represents the bonding position to other structures. 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. It is preferable that the wavy line portions in formula (Ac-1) or formula (Ac-2) are each independently directly bonded to the wavy line portion in the group represented by formula (Ae-1) or formula (Ae-2) below.

[0063]

[0064] 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).

[0065] Alternatively, the compound having a urethane bond may be a compound obtained by introducing a polymerizable group into a polyurethane obtained by reacting a polyisocyanate compound with a polyol compound through a polymer reaction. 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.

[0066] 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.

[0067] As a compound having an epoxy residue, which is an example of an oligomer, a compound containing a hydroxy group is preferred. The number of polymerizable groups in the compound having an epoxy residue is preferably 2 to 6, and more preferably 2 to 3. The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

[0068] Specific examples of oligomers are shown in the table below, but the oligomers used in the present disclosure are not limited to these. Commercially available oligomers may be used, and examples thereof include UA510H, UA-306H, UA-306I, and UA-306T (all manufactured by Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, and UV7620EA (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), U-15HA (manufactured by Shin-Nakamura Chemical Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, and EBECRYL860 (all manufactured by Daicel Allnex Corporation), but are not limited thereto.

[0069] From the viewpoint of improving chemical resistance, 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.

[0070] -Low Molecular Weight Polymerizable Compound- The polymerizable compound may further contain a polymerizable compound other than the above-described oligomer. From the viewpoint of chemical resistance, the polymerizable compound other than the oligomer is preferably a low molecular weight polymerizable compound. The low molecular weight polymerizable compound may be in a 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.

[0071] 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. From the viewpoint of achieving excellent chemical resistance, printing durability, and on-press development residue suppression, 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.

[0072] 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, 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.

[0073] In addition, 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.

[0074] The 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 as desired. In particular, from the viewpoint of printing durability, it is preferable that the image recording layer contains two or more types of polymerizable compounds. The content of the polymerizable compounds (when two or more types of 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.

[0075] [Polymerization Initiator] The image recording layer in the present disclosure preferably contains a polymerization initiator. Furthermore, from the viewpoints of sensitivity, printing durability, on-press developability, and ink receptivity, 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.

[0076] -Electron-Accepting Polymerization Initiator- The image recording layer preferably contains an electron-accepting polymerization initiator as a polymerization initiator. The electron-accepting polymerization initiator is a compound that generates a polymerization initiating species such as a radical by accepting one electron through intermolecular electron transfer when electrons of the infrared absorber are excited by infrared exposure. The electron-accepting polymerization initiator used in the present disclosure is a compound that generates a polymerization initiating species such as a radical or a cation by the energy of light, heat, or both, and can be appropriately selected from known thermal polymerization initiators, compounds having bonds with low 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. Furthermore, as the electron-accepting polymerization initiator, an infrared-sensitive polymerization initiator is preferred. Examples of the electron-accepting radical polymerization initiator include (a) organic halides, (b) carbonyl compounds, (c) azo compounds, (d) organic peroxides, (e) metallocene compounds, (f) azide compounds, (g) hexaarylbiimidazole compounds, (i) disulfone compounds, (j) oxime ester compounds, and (k) onium salt compounds.

[0077] (a) Preferred examples of organic halides include the compounds described in paragraphs 0022 and 0023 of JP-A No. 2008-195018. (b) Preferred examples of carbonyl compounds include the compounds described in paragraph 0024 of JP-A No. 2008-195018. (c) Preferred examples of azo compounds include the azo compounds described in JP-A No. 8-108621. (d) Preferred examples of organic peroxides include the compounds described in paragraph 0025 of JP-A No. 2008-195018. (e) Preferred examples of metallocene compounds include the compounds described in paragraph 0026 of JP-A No. 2008-195018. (f) Preferred examples of azide compounds include 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone. Preferred examples of (g) hexaarylbiimidazole compounds include the compounds described in JP-A No. 2008-195018, paragraph 0027. Preferred examples of (i) disulfone compounds include the compounds described in JP-A Nos. 61-166544 and 2002-328465. Preferred examples of (j) oxime ester compounds include the compounds described in JP-A No. 2008-195018, paragraphs 0028 to 0030.

[0078] Among the above 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. Examples of iodonium salt compounds and sulfonium salt compounds include those described in paragraphs 0060 and 0061 of JP-A No. 2023-138231.

[0079] In addition, as the counter anion of the iodonium salt compound and the sulfonium salt compound, a sulfonamide anion or a sulfonimide anion is preferable, and a sulfonimide anion is more preferable. As the sulfonamide anion, an arylsulfonamide anion is preferable. Furthermore, as the sulfonimide anion, a bisarylsulfonimide anion is preferable. Specific examples of sulfonamide anions or sulfonimide anions include those described in WO 2020 / 262692.

[0080] Furthermore, from the viewpoints of developability and printing durability of the resulting lithographic printing plate, the electron-accepting polymerization initiator may contain a compound represented by the following formula (II).

[0081]

[0082] In formula (II), X Ａ represents a halogen atom, R Ａ represents an aryl group.

[0083] X in formula (II) Ａ Specific examples of R 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. Ａ As the group, an aryl group substituted with an amide group is preferred from the viewpoint of achieving an excellent balance between sensitivity and storage stability.

[0084] As specific examples of the electron-accepting polymerization initiator represented by the above formula (II), those described in WO 2020 / 262692 can be suitably used.

[0085] 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 and preventing plate skipping. The lower limit is preferably −3.80 eV or more, more preferably −3.60 eV or more.

[0086] The electron-accepting polymerization initiator may be used alone or in combination of two or more. The content of the electron-accepting polymerization initiator is preferably 0.1% by mass to 50% by mass, more preferably 0.5% by mass to 30% by mass, and particularly preferably 0.8% by mass to 20% by mass, based on the total mass of the image recording layer.

[0087] - Electron-Donating Polymerization Initiator - From the viewpoint of contributing to improvements in the chemical resistance and printing durability of the lithographic printing plate, the polymerization initiator preferably contains an electron-donating polymerization initiator, and more preferably contains both an electron-donating polymerization initiator and the above-mentioned electron-donating polymerization initiator. Examples of electron-donating polymerization initiators include the following five types. (i) Alkyl or aryl ate complexes: It is believed that the carbon-hetero bond is oxidatively cleaved to generate an active radical. Specific examples include borate salt compounds. (ii) Aminoacetic acid compounds: It is believed that the C-X bond on the carbon adjacent to the nitrogen is oxidatively cleaved to generate an active radical. X is preferably a hydrogen atom, a carboxy group, a trimethylsilyl group, or a benzyl group. Specific examples include N-phenylglycines (which may have a substituent on the phenyl group), N-phenyliminodiacetic acid (which may have a substituent on the phenyl group), and the like. (iii) Sulfur-containing compounds: Compounds in which the nitrogen atom of the aminoacetic acid compound described above is replaced with a sulfur atom can generate active radicals through a similar action. Specific examples include phenylthioacetic acid (the phenyl group may have a substituent). (iv) Tin-containing compounds: Compounds in which the nitrogen atom of the aminoacetic acid compound described above is replaced with a tin atom can generate active radicals through a similar action. (v) Sulfinates: Compounds in which active radicals can be generated by oxidation. Specific examples include sodium arylsulfinate.

[0088] Among these electron-donating polymerization initiators, the image recording layer preferably contains a borate salt compound. As the borate salt compound, a tetraarylborate salt compound or a monoalkyltriarylborate salt compound is preferred, and from the viewpoint of compound stability, a tetraarylborate salt compound is more preferred, and a tetraphenylborate salt compound is particularly preferred. The counter cation of the borate salt 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.

[0089] A specific example of the borate salt compound is sodium tetraphenylborate.

[0090] Furthermore, from the viewpoint of chemical resistance and printing durability, the highest occupied molecular orbital (HOMO) of the electron-donating polymerization initiator used in the present disclosure is preferably −6.00 eV or more, more preferably −5.95 eV or more, 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, more preferably −5.40 eV or less.

[0091] Preferred specific examples of the electron-donating polymerization initiator include those described in WO 2020 / 262692.

[0092] From the viewpoints of visibility, printing durability, and stability over time, the image recording layer preferably contains at least one compound selected from the group consisting of an onium salt compound as the electron-accepting polymerization initiator and a borate salt compound as the electron-donating polymerization initiator, and more preferably contains an onium salt compound as the electron-accepting polymerization initiator and a borate salt compound as the electron-donating polymerization initiator. The image recording layer preferably contains a borate salt compound as the electron-donating polymerization initiator, and more preferably contains a borate salt compound as the electron-donating polymerization initiator, and the value of HOMO of the infrared absorber - HOMO of the borate salt compound is 0.70 eV or less.

[0093] 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, based on the total mass of the image recording layer.

[0094] Furthermore, one preferred aspect of the present disclosure is an aspect in which the electron-accepting polymerization initiator and the electron-donating polymerization initiator form a salt. Specifically, for example, an aspect in which the onium salt compound is a salt of an onium ion and an anion in the electron-donating polymerization initiator (e.g., tetraphenylborate anion) can be mentioned. Furthermore, more preferred is an iodonium borate salt compound in which an iodonium cation in the iodonium salt compound (e.g., di-p-tolyliodonium cation) forms a salt with a borate anion in the electron-donating polymerization initiator. Specific examples of an aspect in which the electron-accepting polymerization initiator and the electron-donating polymerization initiator form a salt include those described in WO 2020 / 262692.

[0095] In the present disclosure, when the image recording layer contains an onium ion and an anion in the above-mentioned electron-donating polymerization initiator, the image recording layer is considered to contain an electron-accepting polymerization initiator and the above-mentioned electron-donating polymerization initiator.

[0096] [Infrared absorber] The image recording layer in the present disclosure preferably contains an infrared absorber. The infrared absorber is not particularly limited, and examples thereof include pigments and dyes. Examples of dyes that can be used as infrared absorbers include commercially available dyes and known dyes described in literature such as "Dye Handbook" (edited by the Society of Organic Synthetic Chemistry, published in 1970). Specific examples of such dyes 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.

[0097] Particularly preferred of these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Furthermore, cyanine dyes and indolenine cyanine dyes are also preferred. Of these, cyanine dyes are particularly preferred.

[0098] The infrared absorber is preferably a cationic polymethine dye having an oxygen or nitrogen atom at the meso position. Preferred examples of the cationic polymethine dye include cyanine dyes, pyrylium dyes, thiopyrylium dyes, and azulenium dyes. From the viewpoints of availability, solvent solubility during the introduction reaction, and the like, cyanine dyes are preferred.

[0099] Specific examples of cyanine dyes include the compounds described in paragraphs 0017 to 0019 of JP-A-2001-133969, the compounds described in paragraphs 0016 to 0021 of JP-A-2002-023360, and the compounds described in paragraphs 0012 to 0037 of JP-A-2002-040638, preferably the compounds described in paragraphs 0034 to 0041 of JP-A-2002-278057 and paragraphs 0080 to 0086 of JP-A-2008-195018, and particularly preferably the compounds described in paragraphs 0035 to 0043 of JP-A-2007-90850, and the compounds described in paragraphs 0105 to 0113 of JP-A-2012-206495. In addition, the compounds described in paragraphs 0008 to 0009 of JP-A No. 5-5005 and paragraphs 0022 to 0025 of JP-A No. 2001-222101 can also be preferably used. As the pigment, the compounds described in paragraphs 0072 to 0076 of JP-A No. 2008-195018 are preferred.

[0100] The infrared absorber may also contain an infrared absorber that decomposes upon exposure to infrared rays (decomposable infrared absorber). Examples of decomposable infrared absorbers include decomposable color-forming infrared absorbers. It is presumed that by using a decomposable infrared absorber as the infrared absorber, the infrared absorber or its decomposition products promote polymerization, and the decomposition products of the infrared absorber interact with the polymerizable compound, resulting in excellent printing durability. The decomposable infrared absorber is preferably an infrared absorber that has the function of absorbing infrared rays, decomposing, and developing a color upon infrared exposure. Hereinafter, a color-developed compound formed by the decomposable infrared absorber absorbing infrared rays and decomposing upon infrared exposure is also referred to as a "color-developing body of the decomposable infrared absorber." Furthermore, the decomposable infrared absorber preferably has the function of absorbing infrared rays upon infrared exposure and converting the absorbed infrared rays into heat. The decomposable infrared absorbent may be any that absorbs and decomposes at least a portion of light in the infrared wavelength region (wavelength 750 nm to 1 mm), but is preferably an infrared absorbent having a maximum absorption wavelength in the wavelength region of 750 nm to 1,400 nm, and more preferably an infrared absorbent having a maximum absorption wavelength in the wavelength region of 760 nm to 900 nm. More specifically, the decomposable infrared absorbent is preferably a compound that decomposes due to exposure to infrared light to produce a compound having a maximum absorption wavelength in the wavelength region of 500 nm to 600 nm.

[0101] The decomposable infrared absorber is preferably an infrared absorber that decomposes due to heat, electron transfer, or both caused by infrared exposure, and more preferably an infrared absorber that decomposes due to electron transfer caused by infrared exposure. Here, "decomposes due to electron transfer" means that electrons excited from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) of the decomposable infrared absorber by infrared exposure undergo intramolecular electron transfer to an electron-accepting group (a group having a potential close to that of the LUMO) within the molecule, resulting in decomposition.

[0102] In addition, from the viewpoint of color development properties, the infrared absorber preferably contains a compound represented by the following formula (X) as a decomposable infrared absorber.

[0103]

[0104] In formula (X), Ar １１ and Ar １２ each independently represents an atomic group necessary to form a substituted or unsubstituted aromatic ring or a substituted or unsubstituted heteroaromatic ring; R １１ and R １２ are each independently a substituted or unsubstituted alkyl group, R １３ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; R １４ represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; Y each independently represents an oxygen atom, a sulfur atom, or >C(R １５ R １６ ) represents a dialkylmethylene group represented by R １５ and R １６ each independently represents a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms; A １ and A ２ each independently represents a substituted or unsubstituted alkyl group, or a group of atoms containing 2 or 3 carbon atoms necessary to combine with each other to form a substituted or unsubstituted 5- or 6-membered non-aromatic carbocyclic ring, and Za represents a counter ion that neutralizes the charge. １１ and Ar １２ each independently represents an atomic group necessary to form a substituted or unsubstituted aromatic ring or a substituted or unsubstituted heteroaromatic ring, and examples of the substituent of the aromatic ring or heteroaromatic ring include an alkyl group, an alkoxy group, a halogen atom, a cyano group, a —COOR group, and —SO ３ R group, or —SO ２ R groups (R represents a substituted or unsubstituted alkyl group), and alkyl groups or halogen atoms are preferred. １１ and Ar １２ is preferably an atomic group necessary for forming a substituted or unsubstituted aromatic ring, and more preferably an atomic group necessary for forming a substituted or unsubstituted benzene ring or naphthalene ring.１５ R １６ ), and a dialkylmethylene group represented by >C(R １５ R １６ ) and R １５ and R １６ are preferably the same dialkylmethylene group. １５ and R １６ are each independently a substituted or unsubstituted alkyl group having 1 or 2 carbon atoms. １５ R １６ ) and R １５ and R １６ is preferably a dialkylmethylene group in which R is a methyl group. １１ and R １２ is preferably a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms. １１ and R １２ may contain an ether bond or an ester bond in the carbon chain of the substituted or unsubstituted alkyl group having 1 to 12 carbon atoms. １３ is preferably a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and more preferably a haloalkyl group in which one or more hydrogen atoms of the alkyl group having 1 to 12 carbon atoms are substituted with halogen atoms. In this case, preferred examples of the halogen atom include a chlorine atom and a bromine atom. Among these, the above R １１ and R １２ are each independently preferably a perfluoroalkyl group. １４ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 or 8 carbon atoms. １ and A ２ are preferably each independently a substituted or unsubstituted alkyl group, or an atomic group containing two or three carbon atoms necessary to bond with each other to form a cyclopentene ring or a cyclohexene ring. When Za is a counter anion, it is preferably an anion containing a halogen atom or an anion containing a boron atom. Specific examples of Za include ClO４ － , P.F. ６ － , B.F. ４ － , SbF ６ － , C.H. ３ SO ３ － , C.F. ３ SO ３ － , C ６ H ５ SO ３ － , C.H. ３ C ６ H ５ SO ３ － , H.O.C. ６ H ５ SO ３ － , ClC ６ H ５ SO ３ － , C.H. ３ C ６ H ５ SO ３ － , tetraarylborate anion (e.g., tetraphenylborate anion), etc. When Za is a counter cation, examples thereof include alkali metal ions, alkaline earth metal ions, tertiary ammonium ions, quaternary ammonium ions, onium ions (iodonium ions, sulfonium ions, phosphonium ions, etc.). Specific examples of compounds represented by formula (X) are listed below, but the present disclosure is not limited to these. Ph represents a phenyl group.

[0105]

[0106] As the infrared absorber and the infrared absorber that decomposes upon exposure to infrared light, those described in WO 2020 / 262692 can be suitably used. Furthermore, as the infrared absorber that decomposes upon exposure to infrared light, those described in JP-A-2008-544322 or WO 2016 / 027886 can be suitably used. Furthermore, as the cyanine dye that is a decomposable infrared absorber, the infrared absorbing compound described in WO 2019 / 219560 can be suitably used.

[0107] The infrared absorbing agent may be used alone or in combination of two or more. In one embodiment, the image recording layer preferably contains two or more infrared absorbing agents. A pigment and a dye may also be used in combination as the infrared absorbing agent. The total content of the infrared absorbing agents in the image recording layer is preferably 0.1% by mass to 10.0% by mass, more preferably 0.5% by mass to 7.5% by mass, based on the total mass of the image recording layer.

[0108] [Relationship Between Electron-Donating Polymerization Initiator, Electron-Accepting Polymerization Initiator, and Infrared Absorber] The image recording layer in the present disclosure preferably contains two or more electron-donating polymerization initiators and electron-accepting polymerization initiators, and further contains an infrared absorber. When the image recording layer contains two or more electron-donating polymerization initiators, electron-accepting polymerization initiators, and infrared absorbers, it is more preferable that the HOMO of at least one of the two or more electron-donating polymerization initiators is −6.0 eV or higher, and the LUMO of the electron-accepting polymerization initiator is −3.0 eV or lower. More preferable aspects of the HOMO of the two or more electron-donating polymerization initiators and the LUMO of the electron-accepting polymerization initiator are as described above. In the image recording layer in the present disclosure, it is presumed that energy is transferred between at least one of the two or more electron-donating polymerization initiators, the electron-accepting polymerization initiator, and the infrared absorber, for example, as shown in the chemical formula below. Therefore, when the HOMO of at least one of the two or more electron-donating polymerization initiators is −6.0 eV or higher and the LUMO of the electron-accepting polymerization initiator is −3.0 eV or lower, it is considered that the radical generation efficiency is improved, and therefore the chemical resistance and printing durability are more likely to be excellent.

[0109]

[0110] From the viewpoint of printing durability and chemical resistance, the HOMO value of the infrared absorber versus the HOMO of at least one electron-donating polymerization initiator is preferably 1.0 eV or less, more preferably 0.70 eV or less, and particularly preferably 0.60 eV or less. From the same viewpoint, the HOMO value of the infrared absorber versus the HOMO of at least one electron-donating polymerization initiator is preferably −0.200 eV or more, more preferably −0.100 eV or more. Note that a negative value means that the HOMO of at least one electron-donating polymerization initiator is higher than the HOMO of the infrared absorber. From the viewpoint of printing durability and chemical resistance, the LUMO value of the electron-accepting polymerization initiator versus the LUMO of the infrared absorber is preferably 1.00 eV or less, more preferably 0.700 eV or less. From the same viewpoint, the LUMO value of the electron-accepting polymerization initiator minus the LUMO value of the infrared absorber is preferably −0.200 eV or higher, and more preferably −0.100 eV or higher. From the same viewpoint, the LUMO value of the electron-accepting polymerization initiator minus the LUMO value of the infrared absorber is preferably 1.00 eV to −0.200 eV, and more preferably 0.700 eV to −0.100 eV. A negative value means that the LUMO of the infrared absorber is higher than the LUMO of the electron-accepting polymerization initiator.

[0111] [Color Former] The image recording layer preferably contains a color former, and more preferably contains an acid color former. As used in the present disclosure, "color former" refers to a compound that develops or fades color in response to stimulation such as light or acid, thereby changing the color of the image recording layer. Furthermore, "acid color former" refers to a compound that develops or fades color and changes the color of the image recording layer when heated in a state in which it accepts an electron-accepting compound (e.g., a proton from an acid, etc.). As the acid color former, particularly preferred 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 contacted with an electron-accepting compound. Examples of such acid color formers include the acid color formers described in JP-A-2023-16860.

[0112] Among these, from the viewpoint of color development, the color former used in the present disclosure is preferably at least one compound selected from the group consisting of spiropyran compounds, spirooxazine compounds, spirolactone compounds, and spirolactam compounds. From the viewpoint of visibility, the hue of the dye after color development is preferably green, blue, or black.

[0113] Furthermore, from the viewpoints of color development and visibility of exposed areas, the acid color former is preferably a leuco dye. The leuco dye is not particularly limited as long as it has a leuco structure, but it is preferably a dye having a spiro structure, and more preferably a dye having a spirolactone ring structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a 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).

[0114]

[0115] In formulas (Le-1) to (Le-3), ERG each independently represents an electron-donating group; １ ~X４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; X ５ ~X １０ each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Ra １ represents a hydrogen atom, an alkyl group, or an alkoxy group; Rb １ ~Rb ４each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group. From the viewpoints of color development and visibility of exposed areas, the electron-donating group in ERG of formulas (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, even 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 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, even 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 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. Note that, in the present disclosure, the ortho position in an aryl group or heteroaryl group other than a phenyl group refers to the bonding position (e.g., the 2nd position, etc.) adjacent to the bonding position 1 of the aryl group or heteroaryl group to another structure.Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group possessed by 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. １ ~X ４ 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. ５ ~X １０ are each independently, from the viewpoint 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, still more preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and particularly preferably a hydrogen atom. １ and Y ２ From the viewpoint of color development and visibility of exposed areas, it is preferable that at least one of the two is C, and Y １ and Y ２It is more preferable that both of Ra in formulas (Le-1) to (Le-3) are C. １ From the viewpoint of color development and visibility of exposed areas, Rb is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group. １ ~Rb ４ 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. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is more preferably a compound represented by any one of the following formulas (Le-4) to (Le-6), and even more preferably a compound represented by the following formula (Le-5):

[0116]

[0117] In formulas (Le-4) to (Le-6), ERG each independently represents an electron-donating group; １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Ra １ represents a hydrogen atom, an alkyl group, or an alkoxy group; Rb １ ~Rb ４ Each of ERG and X in formulae (Le-4) to (Le-6) independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group. １ ~X ４ , Y １ , Y ２ , Ra １ , and Rb １ ~Rb ４ are ERG and X in formulas (Le-1) to (Le-3), respectively. １ ~X４ , Y １ , Y ２ , Ra １ , and Rb １ ~Rb ４ Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is more preferably a compound represented by any one of the following formulas (Le-7) to (Le-9), and particularly preferably a compound represented by the following formula (Le-8):

[0118]

[0119] In formulas (Le-7) to (Le-9), X １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Ra １ ~Ra ４ each independently represents a hydrogen atom, an alkyl group, or an alkoxy group; Rb １ ~Rb ４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group; １ and Rc ２ Each of X in formulas (Le-7) to (Le-9) independently represents an aryl group or a heteroaryl group. １ ~X ４ , Y １ and Y ２ represents X in formulas (Le-1) to (Le-3). １ ~X ４ , Y １ and Y ２ The same applies to the preferred embodiments. １ ~Ra ４are 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. １ ~Rb ４ 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. １ and Rc ２ are each independently preferably a phenyl group or an alkylphenyl group, more preferably a phenyl group, from the viewpoints of color development and visibility of exposed areas. １ and Rc ２ are each independently, from the viewpoints of color development and visibility of exposed areas, 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, still 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. １ and Rc ２ In formula (Le-8), from the viewpoint of color development and visibility of exposed areas, X １ ~X ４ is a hydrogen atom, and Y １ and Y ２ is preferably C. Furthermore, in formula (Le-8), from the viewpoint of color development and visibility of exposed areas, it is preferable that Rb １ and Rb ２ are each independently an aryl group substituted with an alkyl group or an alkoxy group. １ and Rb ２are each independently preferably an aryl group or a heteroaryl group, more preferably an aryl group, further preferably an aryl group having an electron-donating group, and particularly preferably a phenyl group having an electron-donating group at the para position. １ , Rb ２ , Rc １ and Rc ２ From the viewpoints of color development and visibility of exposed areas, the electron-donating group in 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. Furthermore, from the viewpoints of color development and visibility of exposed areas, the acid color former preferably contains one or more compounds selected from the group consisting of compounds represented by the following formula (Le-10) and compounds represented by the following formula (Z-4). In other words, the image recording layer in the lithographic printing plate precursor according to the present disclosure preferably further contains one or more compounds selected from the group consisting of compounds represented by the following formula (Le-10) and compounds represented by the following formula (Z-4).

[0120]

[0121] In formula (Le-10), Ar １ each independently represents an aryl group or a heteroaryl group; Ar ２ each 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. １ represents Rb in formulas (Le-7) to (Le-9). １ and Rb ２ The same applies to the preferred embodiments of Ar in formula (Le-10). ２is Rc in formulas (Le-7) to (Le-9). １ and Rc ２ The meanings and preferred embodiments are also the same. The alkyl group in formulas (Le-1) to (Le-9) may be linear, branched, or have a cyclic structure. The number of carbon atoms in the alkyl group in formulas (Le-1) to (Le-9) is preferably 1 to 20, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 or 2. The number of carbon atoms in the aryl group in formulas (Le-1) to (Le-10) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8. Specific examples of the aryl group in formulas (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 Formulas (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. Furthermore, each of the monovalent organic groups, alkyl groups, aryl groups, heteroaryl groups, dialkylanilino groups, alkylamino groups, and alkoxy groups in Formulas (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. These substituents may be further substituted with other substituents.

[0122]

[0123] In formula (Z-4), Rza １ represents a hydrogen atom, an alkyl group, or an alkoxy group; Rzb１ ~Rb ４ each independently represents a hydrogen atom, an alkyl group, or an aryl group; Rzb １ and Rzb ２ , Rzb ３ and Rzb ４ may be linked to form a ring structure, X represents O or NR, R represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, Y １ and Y ２ Each independently represents CH or N. Rza in formula (Z-4) １ is preferably an alkyl group or an alkoxy group. １ and Rzb ２ are each preferably independently an alkyl group. ３ and Rzb ４ are each independently a hydrogen atom, an alkyl group, or an aryl group, and it is preferable that one of them is an aryl group. １ and Y ２ is preferably CH. The alkyl group in formula (Z-4) may be linear, branched, or have a cyclic structure. The alkyl group in formula (Z-4) preferably has 1 to 20 carbon atoms, more preferably 1 to 8, and even more preferably 1 to 5. The aryl group in formula (Z-4) preferably has 6 to 20 carbon atoms, more preferably 6 to 10, and particularly preferably 6 to 8. Each group in formula (Z-4), such as the alkyl group or aryl group, may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a cyano group. Furthermore, these substituents may be further substituted with other substituents.

[0124] Suitable leuco dyes having a phthalide structure or a fluoran structure include the following compounds: wherein Me represents a methyl group.

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133] As the color former, commercially available products can be used, such as 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 Vermilion. 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-Black XV, Blue-63, Blue-502, GN-169, GN-2, Green-118, Red-40, and Red-8 (all manufactured by Yamamoto Chemical Industry Co., Ltd.), and crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.). Among these commercially available products, ETAC, S-205, BLACK 305, BLACK 400, BLACK 100, BLACK 500, H-7001, GREEN 300, NIRBLACK 78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63, GN-169, and crystal violet lactone are preferred because the films they form have good visible light absorptance.

[0134] These color formers may be used alone or in combination of two or more. The content of the color former is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 7.5% by mass, based on the total mass of the image recording layer.

[0135] [Binder Polymer] The image recording layer may contain a binder polymer. As the binder polymer, a binder polymer used in the image recording layer of an on-press development type lithographic printing plate precursor can be used. Specifically, the binder polymers described in paragraphs

[0288] to

[0317] of WO 2022 / 019217 can be suitably used. In the image recording layer used in the present disclosure, one binder polymer may be used alone, or two or more binder polymers may be used in combination. 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. Furthermore, when the image recording layer in the present disclosure contains another binder polymer, the content of the other binder polymer relative to the total mass of the thermoplastic resin particles and the other binder polymer is preferably more than 0 mass % and not more than 99 mass %, more preferably 20 mass % to 95 mass %, and even more preferably 40 mass % to 90 mass %.

[0136] [Oil Agent] The image recording layer may further contain an oil agent. In the present disclosure, the oil agent refers to a hydrophobic compound that is liquid at 80°C and that separates without being miscible when mixed with an equal 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 fountain solution, the oil agent is preferably a compound with a molecular weight of less than 1,000, more preferably a compound with a molecular weight of 200 to 800, and particularly preferably a compound with a molecular weight of 300 to 500. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, the oil agent is preferably a compound with a boiling point at 1 atmosphere of 200°C or higher, more preferably a compound with a boiling point at 1 atmosphere of 250°C or higher, even more preferably a compound with a boiling point at 1 atmosphere of 300°C or higher, and particularly preferably a compound with a boiling point at 1 atmosphere of 400°C or higher and 500°C or lower. In the present disclosure, unless otherwise specified, the term "boiling point" refers to the boiling point at 1 atmosphere. From the viewpoints of on-press developability and suppression of turbidity in 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 the present disclosure, unless otherwise specified, the term "melting point" refers to the melting point at 1 atmosphere.

[0137] Examples of oil agents include phosphate ester compounds, aromatic hydrocarbon compounds, glyceride compounds, fatty acid compounds, aromatic ester compounds, etc. 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.

[0138] As the phosphate ester compound, from the viewpoints of UV printing durability, ink receptivity, on-press developability, and suppression of fountain solution clouding, a phosphate triester compound is preferred, a triaryl phosphate 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 isomers is particularly preferred. As the aromatic hydrocarbon compound, from the viewpoints of on-press developability and suppression of fountain solution clouding, 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 fountain solution clouding, 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 viewpoints of on-press developability and suppression of fountain solution clouding, an unsaturated fatty acid is preferred, an unsaturated fatty acid having 8 to 30 carbon atoms is more preferred, and an unsaturated fatty acid having 12 to 24 carbon atoms is 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.

[0139] 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.

[0140] From the viewpoints of UV printing durability, ink receptivity, on-press developability, and dampening water turbidity suppression, the oil agent preferably contains an oil agent having a phosphorus atom, and more preferably an oil agent having a phosphorus atom. Also, from the viewpoints of on-press developability and dampening water turbidity suppression, 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-condensed benzene rings.

[0141] From the viewpoints of UV printing durability, ink receptivity, on-press developability, and dampening water turbidity suppression, 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. Known methods and software can be used to calculate the clogP value, but unless otherwise specified, the present disclosure will use the ClogP program incorporated into Cambridgesoft's ChemBioDraw Ultra 12.0.

[0142] Specific examples of oil agents 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.

[0143] Although only one oil agent may be used or two or more oil agents may be used in combination, 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 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, still 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.

[0144] [Chain Transfer Agent] The image recording layer may contain a chain transfer agent. The chain transfer agent may be a chain transfer agent used in the image recording layer of an on-press development type lithographic printing plate precursor. Specifically, the chain transfer agents described in paragraphs

[0388] to

[0393] of WO 2022 / 019217 may be suitably used. Only one chain transfer agent may be added, or two or more chain transfer agents may be added in combination. The content of the chain transfer agent is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 40% by mass, and even more preferably 0.1% by mass to 30% by mass, relative to the total mass of the image recording layer.

[0145] [Oil-Sensitizing Agent] The image recording layer may contain an oil-sensitizing agent to improve ink receptivity. The oil-sensitizing agent may be an oil-sensitizing agent used in the image recording layer of an on-press development type lithographic printing plate precursor. Specifically, the oil-sensitizing agents described in paragraphs 0395 to 0404 of WO 2022 / 019217 are preferably used. The content of the oil-sensitizing agent is preferably 1% by mass to 40.0% by mass, more preferably 2% by mass to 25.0% by mass, and even more preferably 3% by mass to 20.0% by mass, relative to the total mass of the image recording layer. The image recording layer may contain one oil-sensitizing agent alone, or two or more oil-sensitizing agents may be used in combination. One preferred embodiment of the image recording layer used in the present disclosure is an embodiment in which the image recording layer contains two or more compounds as oil-sensitizing agents. Specifically, from the viewpoint of achieving both on-press developability and ink receptivity, the image recording layer used in the present disclosure preferably uses, as the oil sensitizer, a phosphonium compound, a nitrogen-containing low-molecular-weight compound, and an ammonium group-containing polymer in combination, and more preferably uses, as the oil sensitizer, a phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer in combination.

[0146] [Development Accelerator] The image recording layer preferably further contains a development accelerator. The development accelerator preferably has a polarity term SP value of 6.0 to 26.0, more preferably 6.2 to 24.0, even more preferably 6.3 to 23.5, and particularly preferably 6.4 to 22.0. The SP value (solubility parameter, unit: (cal / cm)) in the present disclosure is３ ) １／２ The value of the polar term in the Hansen solubility parameter is the value of the polar term δp in the Hansen solubility parameter. The Hansen solubility parameter is a solubility parameter introduced by Hildebrand, which is divided into three components: a dispersion term δd, a polar term δp, and a hydrogen bond term δh, and is expressed in a three-dimensional space. In this disclosure, the polar term δp is used. δp [cal / cm ３ ] is the Hansen solubility parameter dipole-dipole term, V [cal / cm ３ ] is the molar volume, μ[D] is the dipole moment. For δp, the following formula simplified by Hansen and Beerbower is generally used:

[0147]

[0148] The development accelerator is preferably a hydrophilic polymer compound or a hydrophilic low-molecular-weight compound. In the present disclosure, "hydrophilic" refers to a polarity term of the SP value of 6.0 to 26.0, a hydrophilic polymer compound refers to a compound having a molecular weight (weight average molecular weight if the molecular weight distribution is present) of 3,000 or more, and a hydrophilic low-molecular-weight compound refers to a compound having a molecular weight (weight average molecular weight if the molecular weight distribution is present) of less than 3,000. Examples of hydrophilic polymer compounds include cellulose compounds, with cellulose compounds being preferred. Examples of cellulose compounds include cellulose or compounds in which at least a portion of cellulose has been modified (modified cellulose compounds), with modified cellulose compounds being preferred. Examples of modified cellulose compounds include compounds in which at least a portion of the hydroxy groups of cellulose have been substituted with at least one group selected from the group consisting of alkyl groups and hydroxyalkyl groups. The degree of substitution of the compound in which at least a portion of the hydroxy groups of cellulose have been substituted with at least one group selected from the group consisting of alkyl groups and hydroxyalkyl groups is preferably 0.1 to 6.0, and more preferably 1 to 4. The modified cellulose compound is preferably an alkyl cellulose compound or a hydroxyalkyl cellulose compound, and more preferably a hydroxyalkyl cellulose compound. A preferred example of the alkyl cellulose compound is methyl cellulose. A preferred example of the hydroxyalkyl cellulose compound is hydroxypropyl cellulose. The molecular weight of the hydrophilic polymer compound (weight average molecular weight when the compound has a molecular weight distribution) is preferably 3,000 to 5,000,000, and more preferably 5,000 to 200,000.

[0149] Examples of hydrophilic low-molecular-weight compounds include glycol compounds, polyol compounds, organic amine compounds, organic sulfonic acid compounds, organic sulfamine compounds, organic sulfuric acid compounds, organic phosphonic acid compounds, organic carboxylic acid compounds, and betaine compounds, with polyol compounds, organic sulfonic acid compounds, and betaine compounds being preferred. Examples of glycol compounds include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, as well as ether or ester derivatives of these compounds. Examples of polyol compounds include glycerin, pentaerythritol, and tris(2-hydroxyethyl)isocyanurate. Examples of organic amine compounds include triethanolamine, diethanolamine, monoethanolamine, and salts thereof. Examples of organic sulfonic acid compounds include alkylsulfonic acids, toluenesulfonic acids, benzenesulfonic acids, and salts thereof, with alkylsulfonic acids having an alkyl group of 1 to 10 carbon atoms being preferred. Examples of organic sulfamine compounds include alkylsulfamic acids and salts thereof. Examples of organic sulfate compounds include alkyl sulfates, alkyl ether sulfates, and salts thereof. Examples of organic phosphonic acid compounds include phenylphosphonic acid and salts thereof. Examples of organic carboxylic acid compounds include tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, and salts thereof. Examples of betaine compounds include phosphobetaine compounds, sulfobetaine compounds, and carboxybetaine compounds, with trimethylglycine being preferred. The molecular weight of the hydrophilic low-molecular-weight compound (weight-average molecular weight when there is a molecular weight distribution) is preferably 100 or more and less than 3,000, and more preferably 300 to 2,500.

[0150] The development accelerator is preferably a compound having a cyclic structure. The cyclic structure is not particularly limited, but examples include a glucose ring, an isocyanuric ring, an aromatic ring optionally containing a heteroatom, and an aliphatic ring optionally containing a heteroatom, each of which may have at least a portion of a hydroxy group substituted. A glucose ring or an isocyanuric ring is preferred. Examples of compounds having a glucose ring include the above-mentioned cellulose compounds. Examples of compounds having an isocyanuric ring include the above-mentioned tris(2-hydroxyethyl)isocyanurate. Examples of compounds having an aromatic ring include the above-mentioned toluenesulfonic acid and benzenesulfonic acid. Examples of compounds having an aliphatic ring include the above-mentioned alkyl sulfates in which the alkyl group has a cyclic structure. The above-mentioned compounds having a cyclic structure preferably have a hydroxy group. Examples of compounds having a hydroxy group and a cyclic structure preferably include the above-mentioned cellulose compounds and the above-mentioned tris(2-hydroxyethyl)isocyanurate. The development accelerator is preferably an onium salt compound. Examples of onium salt compounds include ammonium compounds and sulfonium compounds, with ammonium compounds being preferred. Examples of the development accelerator that is an onium salt compound include trimethylglycine, etc. The onium salt compound in the electron-accepting polymerization initiator is a compound in which the polarity term of the SP value is not 6.0 to 26.0, and is not included in the development accelerator.

[0151] The image recording layer may contain one type of development accelerator alone, or two or more types may be used in combination. One preferred embodiment of the image recording layer in the present disclosure is an embodiment in which the image recording layer contains two or more compounds as the development accelerator. Specifically, from the viewpoint of on-press developability and ink receptivity, the image recording layer preferably contains the above-mentioned polyol compound and the above-mentioned betaine compound, the above-mentioned betaine compound and the above-mentioned organic sulfonic acid compound, or the above-mentioned polyol compound and the above-mentioned organic sulfonic acid compound as the development accelerator. The content of the development accelerator relative to the total mass of the image recording layer is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less.

[0152] [Other Components] The image recording layer may contain other components such as surfactants, polymerization inhibitors, higher fatty acid derivatives, plasticizers, inorganic particles, inorganic layer compounds, etc. For specific details, see paragraphs 0114 to 0159 of JP-A-2008-284817.

[0153] <<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 described above in a known solvent to prepare a coating liquid, applying the coating liquid 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 ２Within this range, good sensitivity and good film properties of the image recording layer can be obtained. As the solvent, known solvents can be used. Specific examples include water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3-methoxy-1-propanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, methyl lactate, and ethyl lactate. The solvent may be used alone or in combination of two or more. The solid content concentration in the coating solution 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 preferably 0.3 g / m ２ ~3.0g / m ２ Preferably, the thickness of the image recording layer in the lithographic printing plate precursor according to the present disclosure is 0.1 μm to 3.0 μm, and more preferably 0.3 μm to 2.0 μm. In the present disclosure, the 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).

[0154] (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 a "hydrophilic support").

[0155] The support in the present disclosure preferably has an oxide film, and more preferably is an aluminum plate that has been roughened and anodized by a known method. That is, the support in the present disclosure preferably has an aluminum plate and an anodized aluminum film disposed on the aluminum plate.

[0156] Preferably, 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 facing the image recording layer, the micropores having an average diameter of more than 10 nm and not more than 100 nm at the surface of the anodized film. Furthermore, 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 communicating with the bottoms of the large-diameter pores and extending from the communicating positions to a depth of 20 nm to 2,000 nm, the large-diameter pores having an average diameter of 15 nm to 100 nm at the surface of the anodized film, and the small-diameter pores having an average diameter of 13 nm or less at the communicating positions. The support preferably has an oxide film on its surface, the oxide film having micropores extending in the depth direction from the surface of the oxide film on the image recording layer side, the micropores having large-diameter pores on the surface of the oxide film having an average pore diameter of 15 nm to 100 nm, and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend further in the depth direction from the communicating positions, the small-diameter pores having an average pore diameter of 15 nm or less.The support preferably has an oxide film on its surface, the oxide film having micropores extending in the depth direction from the surface of the oxide film on the image recording layer side, the maximum diameter of the micropores inside the micropores being 1.2 to 10 times the average pore diameter on the surface of the oxide film.

[0157] 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 coating 20a (hereinafter simply referred to as "anodized coating 20a") are laminated in this order. The anodized coating 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 coating, an image recording layer, and a water-soluble resin layer, in this order, on an aluminum plate.

[0158] - Anodized film - A preferred embodiment of the anodized film 20a will be described below. The anodized film 20a is a film produced on the surface of the aluminum plate 18 by anodizing, and this film 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).

[0159] The average diameter (average opening diameter) of the micropores 22a in the anodized coating 20a at the surface of the anodized coating is preferably greater than 10 nm and less than or equal to 100 nm. In particular, from the viewpoint of a balance between printing durability, stain resistance, and image visibility, 15 nm to 60 nm is more preferable, 20 nm to 50 nm is even more preferable, and 20 nm to 40 nm is particularly preferable. 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. Furthermore, when the average diameter is 100 nm or less, printing durability is excellent. The average diameter of the micropores 22a is determined by observing the surface of the anodized coating 20a (N = 4) using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, and measuring the diameters (diameters) of micropores present in a 400 nm × 600 nm range at 50 locations in the four obtained images, 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.

[0160] 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.

[0161] 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 that communicate with the bottoms of the large-diameter pores and extend from the communication positions to a certain depth. For example, as shown in Figure 2, an aluminum support 12b may include an aluminum plate 18 and an anodized coating 20b having micropores 22b each composed of large-diameter pores 24 and small-diameter pores 26. For example, the micropores 22b in the anodized coating 20b are composed of large-diameter pores 24 extending from the surface of the anodized coating to a depth of 10 nm to 1,000 nm (depth D: see Figure 2), and small-diameter pores 26 that communicate with the bottoms of the large-diameter pores 24 and extend from the communication positions to a depth of 20 nm to 2,000 nm. Specifically, for example, the embodiments described in paragraphs 0107 to 0114 of JP-A-2019-162855 can be used.

[0162] -Method for manufacturing support- A preferred method for manufacturing a support used in the present disclosure is, for example, a manufacturing method that performs the following steps in order: Surface roughening step: a step of roughening an aluminum plate; Anodizing step: a step of anodizing the surface-roughened aluminum plate; Pore widening step: a step of contacting the aluminum plate having the anodized film obtained in the anodizing step with an acid aqueous solution or an alkaline aqueous solution to enlarge the diameter of the micropores in the anodized film. The procedure of each step is described in detail below.

[0163] <<Surface Roughening Treatment Step>> The surface roughening treatment step is a step of performing a surface roughening treatment, including electrochemical surface roughening treatment, on the surface of an aluminum plate. This step is preferably performed before the anodizing treatment step described below, but may not be performed if the surface of the aluminum plate already has a preferred surface shape. This can be performed by the method described in paragraphs 0086 to 0101 of JP 2019-162855 A.

[0164] <<Anodizing Treatment Step>> The procedure for the anodizing treatment step is not particularly limited as long as the above-described 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, or the like can be used as the electrolytic bath. For example, the sulfuric acid concentration can be 100 g / L to 300 g / L. The anodizing treatment conditions are appropriately set depending on the electrolytic solution used, but for example, a solution temperature of 5°C to 70°C (preferably 10°C to 60°C), a current density of 0.5 A / dm ２ ~60 A / dm ２ (preferably 1 A / dm ２ ~60 A / 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 0.1 g / m ２ ~5g / m ２ (preferably 0.2 g / m ２ ~3g / m ２ ) are listed.

[0165] <<Pore Widening Treatment>> The pore widening treatment is a treatment (pore size enlargement treatment) that enlarges the diameter (pore diameter) of micropores present in the anodized coating formed by the above-mentioned anodizing treatment step. The pore widening treatment can be carried out by contacting the aluminum plate obtained by the above-mentioned anodizing treatment step with an acid aqueous solution or an alkaline aqueous solution. The contact method is not particularly limited, and examples include immersion and spraying.

[0166] The support may have, if necessary, a backcoat layer containing an organic polymer compound described in JP-A-5-45885 or a silicon alkoxy compound described in JP-A-6-35174 on the surface opposite to the image recording layer.

[0167] (Undercoat layer (intermediate 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 while suppressing a decrease in 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.

[0168] Compounds used in the undercoat layer include polymers having an adsorptive group (support-adsorbing group) capable of adsorbing to the support surface and a hydrophilic group. In order to improve adhesion to the image-recording layer, polymers having an adsorptive group and a hydrophilic group and further having a crosslinkable group are preferred. 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.

[0169] When the compound used in the undercoat layer is a polymer, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferred. Examples of the adsorptive group that can be adsorbed onto the support surface include a phenolic hydroxy group, a carboxy group, a -PO ３ H ２ , -OPO ３ H ２ , -CONHSO ２ -, -SO ２ NHSO ２ --, --COCH ２ COCH ３ is preferred. As the hydrophilic group, a sulfo group or a salt thereof, or a salt of a carboxy group is preferred. As the crosslinkable group, an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, or the like is preferred. 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.

[0170] Specifically, preferred examples include silane coupling agents having an addition-polymerizable ethylenic double bond reactive group, as described in JP-A-10-282679, and phosphorus compounds 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 an adsorptive group, a hydrophilic group, and a crosslinkable group that can be adsorbed to the support surface, as described in JP-A-2005-125749 and JP-A-2006-188038.

[0171] The content of ethylenically unsaturated bond groups in the polymer used in the undercoat layer is preferably 0.1 mmol to 10.0 mmol, more preferably 0.2 mmol to 5.5 mmol, per 1 g of the polymer. The weight-average molecular weight (Mw) of the polymer used in the undercoat layer is preferably 5,000 or more, more preferably 10,000 to 300,000.

[0172] In addition to the above-described compounds for use in an undercoat layer, the undercoat layer may contain, in order to prevent staining over time, a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, a compound having an amino group or a functional group having polymerization inhibitory 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, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, etc.), and the like.

[0173] In particular, from the viewpoints of printing durability and on-press developability, it is preferred that the lithographic printing plate precursor according to the present disclosure further comprises an intermediate layer between the support and the image recording layer, and that the intermediate layer contains a copolymer having a support-adsorbing group and a hydrophilic group.

[0174] The undercoat layer is applied by a known method. The coating amount (solid content) of the undercoat layer is 0.1 mg / m２ ~100 mg / m ２ is preferred, and 1 mg / m ２ ~30 mg / m ２ is more preferred.

[0175] <Overcoat layer> The lithographic printing plate precursor according to the present disclosure preferably has an overcoat layer (sometimes referred to as a "protective layer") on the surface of the image recording layer opposite the support side. The lithographic printing plate precursor according to the present disclosure preferably has a support, an image recording layer, and an overcoat layer in this order. The overcoat layer has the function of suppressing image formation inhibiting reactions by blocking oxygen, and may also have the function of preventing scratches on the image recording layer and ablation during exposure to high-intensity laser light.

[0176] Overcoat layers with such properties are described, for example, in U.S. Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. The low-oxygen-permeable polymer used in the overcoat layer can be selected from either a water-soluble polymer or a water-insoluble polymer, and two or more types can be mixed as needed. However, from the viewpoint of on-press developability, it is preferable to include a water-soluble polymer. In this disclosure, a water-soluble polymer refers to a polymer having a solubility in water at 25°C of greater than 5% by mass. Examples of water-soluble polymers used in the overcoat layer include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, cellulose derivatives, polyethylene glycol, poly(meth)acrylonitrile, and the like. Furthermore, it is preferable that the hydrophilic polymer include at least one selected from the group consisting of modified polyvinyl alcohol and cellulose derivatives. As the modified polyvinyl alcohol, an acid-modified polyvinyl alcohol having a carboxy group or a sulfo group is preferably used. Specific examples include the modified polyvinyl alcohols described in JP-A Nos. 2005-250216 and 2006-259137. Examples of cellulose derivatives include methyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.

[0177] Among the water-soluble polymers, polyvinyl alcohol is preferably contained, and polyvinyl alcohol having a degree of saponification of 50% or more is more preferably contained. The degree of saponification is preferably 60% or more, more preferably 70% or more, and even more preferably 85% or more. The upper limit of the degree of saponification is not particularly limited, and it is sufficient that it is 100% or less. The degree of saponification is measured according to the method described in JIS K 6726:1994. Another preferred embodiment of the overcoat layer includes polyvinyl alcohol and polyethylene glycol.

[0178] When the overcoat layer in the present disclosure contains a water-soluble polymer, the content of the water-soluble polymer relative to the total mass of the overcoat layer 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.

[0179] The overcoat layer preferably contains a hydrophobic polymer. A hydrophobic polymer refers to a polymer that dissolves in an amount of less than 5 g in 100 g of pure water at 125°C or does not dissolve at all. Examples of hydrophobic polymers include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly(meth)acrylic acid alkyl esters (e.g., polymethyl(meth)acrylate, polyethyl(meth)acrylate, polybutyl(meth)acrylate, etc.), and copolymers of raw material monomers for these resins. The hydrophobic polymer preferably contains a polyvinylidene chloride resin. Furthermore, the hydrophobic polymer preferably contains a styrene-acrylic copolymer (also referred to as a styrene-acrylic resin). Furthermore, from the viewpoint of on-press developability, the hydrophobic polymer is preferably a hydrophobic polymer particle.

[0180] The hydrophobic polymer may be used alone or in combination of two or more kinds.

[0181] When the overcoat layer contains a hydrophobic polymer, the content of the hydrophobic polymer is preferably 1% by mass to 70% by mass, more preferably 5% by mass to 50% by mass, and even more preferably 10% by mass to 40% by mass, relative to the total mass of the overcoat layer.

[0182] In the present disclosure, the area ratio of the hydrophobic polymer on the surface of the overcoat layer is preferably 30 area % or more, more preferably 40 area % or more, and even more preferably 50 area % or more. The upper limit of the area ratio of the hydrophobic polymer on the surface of the overcoat layer can be, for example, 90 area %. The area ratio of the hydrophobic polymer on the surface of the overcoat layer can be measured as follows. Using a PHI nano TOFII time-of-flight secondary ion mass spectrometer (TOF-SIMS) manufactured by ULVAC-PHI, Inc., a Bi ion beam (primary ions) is irradiated onto the surface of the overcoat layer at an acceleration voltage of 30 kV, and the peak of ions (secondary ions) emitted from the surface corresponding to the hydrophobic portion (i.e., the region due to the hydrophobic polymer) is measured to map the hydrophobic portion. ２ The area of ​​the hydrophobic portion per unit area is measured to determine the occupied area ratio of the hydrophobic portion, which is defined as the "occupied area ratio of the hydrophobic polymer on the surface of the overcoat layer." For example, when the hydrophobic polymer is an acrylic resin, ６ H １３ O － When the hydrophobic polymer is polyvinylidene chloride, the measurement is performed based on the peak of C ２ H ２ Cl ＋ The above occupied area ratio can be adjusted by the amount of hydrophobic polymer added, etc.

[0183] The overcoat layer preferably contains a filler from the viewpoint of suppressing development defects. Examples of fillers include inorganic particles, organic resin particles, and inorganic layered compounds. Among these, inorganic layered compounds are preferred. By using inorganic layered compounds, it is possible to effectively suppress redeposited material from the roll surface from directly adhering to the surface of the image recording layer. Examples of inorganic particles include metal oxide particles such as silica particles. Examples of organic resin particles include crosslinked resin particles. The inorganic layered compounds are particles having a thin, flat shape, and include, for example, mica groups such as natural mica and synthetic mica, and compounds of the formula: 3MgO.4SiO.H ２ Examples of the inorganic layered compound include talc, taeniolite, montmorillonite, saponite, hectorite, zirconium phosphate, etc., represented by the formula: A(B, C) ２－５ D ４ O １０ (OH, F, O) ２ [wherein A is any of K, Na, and Ca, B and C are any of Fe(II), Fe(III), Mn, Al, Mg, and V, and D is Si or Al.]

[0184] In the mica group, natural micas include muscovite, sodalite, phlogopite, biotite, and lepidolite. Synthetic micas include fluorphlogopite KMg. ３ (AlSi ３ O １０ ) F ２ , potassium tetrasilicic mica KMg ２．５ Si ４ O １０ ) F ２ Non-swelling mica such as Na tetrasilicic mica NaMg ２．５ (Si ４ O １０ ) F ２ , Na or Li taeniolite (Na, Li) Mg ２ Li(Si ４ O １０ ) F ２ , montmorillonite-based Na or Li hectorite (Na, Li) １／８ Mg２／５ Li １／８ (Si ４ O １０ ) F ２ Examples of suitable micas include swellable micas such as those listed above. Synthetic smectite is also useful.

[0185] Among the mica compounds mentioned above, fluorine-based swellable mica is particularly useful. That is, swellable synthetic mica has a layered structure consisting of unit crystal lattice layers with a thickness of about 10 Å to 15 Å (1 Å = 0.1 nm), and the metal atom substitution within the lattice is significantly greater than that of other clay minerals. As a result, the lattice layers have a positive charge deficiency, and to compensate for this, Li is inserted between the layers. ＋ , Na ＋ , Ca ２＋ , Mg ２＋ The cations present between these layers are called exchangeable cations and can be exchanged with various cations. In particular, the cations between the layers are Li ＋ , Na ＋ In the case of mica, the ionic radius is small, so the bonds between the layered crystal lattices are weak, and it swells greatly in water. When shear is applied in this state, it cleaves easily and forms a stable sol in water. Swellable synthetic mica has a strong tendency in this regard, and is particularly preferred.

[0186] Regarding the shape of the mica compound, from the viewpoint of diffusion control, the thinner the thickness, the better, and the larger the planar size, the better, as long as it does not impair the smoothness of the coated surface or the transmittance of actinic rays. Therefore, the aspect ratio is preferably 20 or more, more preferably 100 or more, and particularly preferably 200 or more. The aspect ratio is the ratio of the major axis to the thickness of the particle, and can be measured, for example, from a projection view of a particle in a micrograph. The larger the aspect ratio, the greater the effect obtained.

[0187] The particle size of the mica compound is preferably 0.3 μm to 20 μm, more preferably 0.5 μm to 10 μm, and particularly preferably 1 μm to 5 μm in terms of average major axis. The average particle thickness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.01 μm or less. Specifically, for example, in the case of swellable synthetic mica, a representative compound, a preferred embodiment is one in which the thickness is about 1 nm to 50 nm and the face size (major axis) is about 1 μm to 20 μm.

[0188] The content of the inorganic layered compound is preferably 1% by mass to 60% by mass, more preferably 3% by mass to 50% by mass, based on the total mass of the overcoat layer. Even when multiple types of inorganic layered compounds are used in combination, the total amount of the inorganic layered compounds is preferably within the above range. Within the above range, oxygen barrier properties are improved, good sensitivity is obtained, and a decrease in ink receptivity can be prevented.

[0189] The overcoat layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coatability, inorganic particles for controlling surface slippage, etc. The overcoat layer may also contain an oil-sensitizing agent as described in the image-recording layer.

[0190] The overcoat layer is applied by 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, 0.02 g / m ２ ~1g / m ２ The thickness of the overcoat layer in the lithographic printing plate precursor according to the present disclosure is preferably 0.1 μm to 5.0 μm, and more preferably 0.3 μm to 4.0 μm.

[0191] In particular, from the viewpoints of printing durability and development residue suppression, the lithographic printing plate precursor according to the present disclosure preferably further has an overcoat layer containing an inorganic layer compound on the image recording layer. Also, from the viewpoints of printing durability and development residue suppression, the lithographic printing plate precursor according to the present disclosure preferably further has an overcoat layer containing a water-soluble polymer on the image recording layer, and the thickness of the overcoat layer is preferably greater than the thickness of the image recording layer.

[0192] 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 known layers may be included. For example, a backcoat layer may be provided on the side of the support opposite to the image recording layer side, as needed.

[0193] (Method for preparing a lithographic printing plate and a lithographic printing method) A lithographic printing plate can be prepared by imagewise exposing the lithographic printing plate precursor according to the present disclosure and then subjecting it to a development process. The method for preparing a lithographic printing plate according to the present disclosure preferably includes a step of imagewise exposing the on-press development type lithographic printing plate precursor according to the present disclosure (hereinafter also referred to as an "exposure step"), and 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 (hereinafter also referred to as an "on-press development step"). The lithographic printing method according to the present disclosure preferably includes a step of imagewise exposing the on-press development type lithographic printing plate precursor according to the present disclosure (exposure step), 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 to prepare a lithographic printing plate (on-press development step), and a step of printing with the obtained lithographic printing plate (printing step).

[0194] Further, a method for producing a lithographic printing plate according to the present disclosure includes a step of imagewise exposing an on-press development type lithographic printing plate precursor to an infrared laser, 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 a non-image area, wherein the on-press development type lithographic printing plate precursor has a support and an image recording layer on the support, the image recording layer contains an infrared absorber capable of donating an electron to the initiator, and a color former precursor, and the energy density of the infrared laser exposure at a wavelength of 830 nm is 110 mJ / cm. ２ and a method for producing a lithographic printing plate, in which when the image recording layer is exposed to an infrared laser, the change in lightness ΔL of the image recording layer before and after the exposure is 3.0 or more. Furthermore, the method for producing a lithographic printing plate according to the present disclosure preferably comprises the steps of imagewise exposing an on-press developable lithographic printing plate precursor to an infrared laser, and supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas, wherein the on-press developable lithographic printing plate precursor has a support and an image recording layer on the support, the image recording layer contains an initiator, an infrared absorber, and a color former precursor, and the image recording layer satisfies the following formula L: 2.0≦L1−L0 Formula L In formula L, L1 represents the visibility of the image recording layer, and L0 represents the visibility of a layer that is the same as the image recording layer except for the absence of the color former precursor. Furthermore, with regard to the lithographic printing method according to the present disclosure, each of these aspects preferably further includes the printing step described above.

[0195]

[0033] Preferred aspects of each step in the method for preparing a lithographic printing plate according to the present disclosure and the lithographic printing method according to the present disclosure will be described below in order. The lithographic printing plate precursor according to the present disclosure can also be developed using a developer. The exposure step and on-press development step in the method for preparing a lithographic printing plate according to the present disclosure are the same step, and the on-press development step in the method for preparing a lithographic printing plate according to the present disclosure is the same step.

[0196] <Exposure Step> 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 and unexposed areas. The lithographic printing plate precursor according to the present disclosure is preferably exposed to laser light through a transparent original having a line image, a halftone dot image, or the like, or imagewise by laser light 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 10 mJ / cm. ２ ~300 mJ / cm ２ It is preferable to use a multi-beam laser device to shorten the exposure time. The exposure mechanism may be any of an internal drum system, an external drum system, a flatbed system, etc. Image exposure can be carried out by a conventional method using a plate setter or the like. 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.

[0197] <On-Press Development Step> The method for producing a lithographic printing plate according to the present disclosure preferably includes an on-press development step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image-recording layer in non-image areas.

[0198] [On-Press Development Method] In the on-press development method, an image-wise exposed lithographic printing plate precursor is preferably supplied with an oil-based ink and an aqueous component on a printing press, and the image-recording layer in non-image areas is removed to produce a lithographic printing plate. That is, after image-wise exposure, the lithographic printing plate precursor is either mounted on a printing press as is without any development treatment, or the lithographic printing plate precursor is mounted on a printing press, image-wise exposed on the press, and then oil-based ink and an aqueous component are supplied to print. In the early stages of printing, 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 component, thereby exposing a hydrophilic surface in those areas. Meanwhile, in the exposed areas, the image-recording layer cured by exposure forms an oil-based ink-receptive area with an oleophilic surface. Either an oil-based ink or an aqueous component may be supplied first to the plate surface, but it is preferable to supply the oil-based ink first to prevent contamination of the aqueous component with the components of the image-recording layer from which the aqueous component has been removed. In this way, the lithographic printing plate precursor is developed on the press and used as is for printing a large number of sheets. As the oil-based ink and aqueous component, printing ink and fountain solution for ordinary lithographic printing are preferably used.

[0199] The laser used for imagewise exposure of the lithographic printing plate precursor according to the present disclosure preferably has a light source wavelength of 300 nm to 450 nm or 750 nm to 1,400 nm. In the case of a light source of 300 nm to 450 nm, a lithographic printing plate precursor containing in an image recording layer a sensitizing dye having an absorption maximum in this wavelength region is preferably used, and for a light source of 750 nm to 1,400 nm, the above-mentioned light sources are preferably used. As a light source of 300 nm to 450 nm, a semiconductor laser is suitable.

[0200] <Printing Step> The lithographic printing method according to the present disclosure includes a printing step in which printing ink is supplied to a lithographic printing plate to print a recording medium. The printing ink is not particularly limited, and various known inks can be used as desired. Examples of preferred printing inks include oil-based inks and ultraviolet-curable inks (UV inks). In the printing step, dampening water may be supplied as needed. The printing step may be performed consecutively to the on-press development step without stopping the printing press. The recording medium is not particularly limited, and known recording media can be used as desired.

[0201] In the method for preparing a lithographic printing plate from a lithographic printing plate precursor according to the present disclosure and the lithographic printing method according to the present disclosure, the entire surface of the lithographic printing plate precursor may be heated, as necessary, before exposure, during exposure, or between exposure and development. Such heating promotes the image formation reaction in the image recording layer, 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.

[0202] 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).

[0203] (Examples 1 to 20, and Comparative Examples 1 and 2) <Preparation of Support> -Preparation of Support 1- A 0.3 mm thick aluminum plate (aluminum alloy plate) made of material 1S was subjected to the following treatments (F-a) to (F-g) to prepare Support 1. Note that a water rinsing treatment was performed between all treatment steps, and after the water rinsing treatment, the liquid was removed using nip rollers.

[0204] (F-a) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m. ２ It was.

[0205] (Fb) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 150 g / L and a liquid temperature of 30° C. was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0206] (F-c) Electrochemical Graining Treatment Electrochemical graining treatment was carried out 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, and an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The waveform of the alternating current was a sine wave with symmetrical positive and negative waveforms, the frequency was 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 the electrolysis temperature is 112.5 C / 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 to the aluminum plate.

[0207] (F-d) Alkali Etching Treatment An 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 aluminum plate at a temperature of 45°C. The amount of dissolved aluminum on the electrochemically roughened surface was 0.2 g / m. ２ It was.

[0208] (Fe) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L and a liquid temperature of 35°C was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0209] (F-f) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 3. A 150 g / L aqueous phosphoric acid solution was used as the electrolyte, and the solution temperature was 35°C and the current density was 4.5 A / dm ２ Anodizing treatment was carried out under the conditions of ２ An anodized film of the formula (I) was formed on the surface of the aluminum plate 616. In the anodizing treatment apparatus 610 shown in FIG. 3, the aluminum plate 616 is transported as indicated by the arrow in FIG. 3. In a power supply tank 612 containing an electrolytic solution 618, the aluminum plate 616 is positively charged by a power supply electrode 620. The aluminum plate 616 is 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 plate 616 is then negatively charged by an electrolytic electrode 630, thereby forming an anodized film on the surface of the aluminum plate 616. The aluminum plate 616 leaves the electrolytic treatment tank 614 and is transported to a subsequent process. In the anodizing device 610, a roller 622, a nip roller 624, and a roller 628 constitute a direction-changing means, and the aluminum plate 616 is transported in a mountain-like and inverted U-like 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.

[0210] (F-g) Second-stage anodizing treatment: The second-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in FIG. 3. A 170 g / L aqueous sulfuric acid solution was used as the electrolyte, and the solution temperature was 50°C and the current density was 13 A / dm ２ Anodizing treatment was carried out under the conditions of ２ The anodized film of the support 1 was formed. After that, the support was washed with water by spraying. The average diameter of the micropores in the support 1 was 40 nm. ＊ a ＊ b ＊ Lightness L in the color system ＊ The value was 83.7.

[0211] - Preparation of Support 2 - A 0.3 mm thick aluminum plate (aluminum alloy plate) made of material 1S was subjected to the following treatments (F-a) to (F-f) to prepare Support 2. Note that a water rinsing treatment was performed between all treatment steps, and after the water rinsing treatment, the liquid was removed using nip rollers.

[0212] (F-a) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m. ２ It was.

[0213] (Fb) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 150 g / L and a liquid temperature of 30° C. was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0214] (F-c) Electrochemical Graining Treatment Electrochemical graining treatment was carried out 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, and an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The waveform of the alternating current was a sine wave with symmetrical positive and negative waveforms, the frequency was 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. ２The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm ２ and the electrolysis temperature is 112.5 C / 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 to the aluminum plate.

[0215] (F-d) Alkali Etching Treatment An 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 aluminum plate at a temperature of 45°C. The amount of dissolved aluminum on the electrochemically roughened surface was 0.2 g / m. ２ It was.

[0216] (Fe) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L and a liquid temperature of 35°C was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0217] (F-f) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 3. A 150 g / L aqueous phosphoric acid solution was used as the electrolyte, and the solution temperature was 35°C and the current density was 4.5 A / dm ２ Anodizing treatment was carried out under the conditions of ２ The average diameter of the micropores in the support 2 was 40 nm. ＊ a ＊ b ＊ Lightness L in the color system ＊ The value was 82.4.

[0218] -Preparation of support 3- Support 3 was prepared according to the support manufacturing method of Example 5 of WO 2021 / 067054.

[0219] - Preparation of Support 4 - A 0.3 mm thick aluminum plate (aluminum alloy plate) of material 1S was subjected to the following treatments (Ja) to (Jm) to produce Support 4. Note that a water rinsing treatment was performed between all treatment steps, and after the water rinsing treatment, the liquid was removed using nip rollers.

[0220] (Ja) Mechanical roughening treatment (brush graining method) Using an apparatus such as that shown in FIG. 4, a suspension of pumice (specific gravity 1.1 g / cm ３ ) was supplied to the surface of the aluminum plate as an abrasive slurry, while a mechanical roughening treatment was performed using a rotating bundled brush. In Figure 4, 31 is an aluminum plate, 32 and 34 are roller-shaped brushes (bundled brushes in this example), 33 is an abrasive slurry, and 35, 36, 37, and 38 are support rollers. In the mechanical roughening treatment, the median diameter (μm) of the abrasive was 30 μm, the number of brushes was 4, and the brush rotation speed (rpm) was 250 rpm. The bundled brush was made of 6-10 nylon, with a bristle diameter of 0.3 mm and a bristle length of 50 mm. The brush was densely packed in a φ300 mm stainless steel cylinder with holes drilled into it. The distance between the two support rollers (φ200 mm) below the bundled brush was 300 mm. The bundled brush was pressed down until the load of the drive motor rotating the brush was 10 kW higher than the load before pressing the bundled brush against the aluminum plate. The direction of rotation of the brush was the same as the direction of movement of the aluminum plate.

[0221] (J-b) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 10 g / m. ２ It was.

[0222] (J-c) Desmutting Treatment Using Acidic Aqueous Solution Desmutting treatment was performed by spraying the nitric acid waste solution used in the subsequent electrochemical graining treatment at a liquid temperature of 35°C onto the aluminum plate for 3 seconds as the acidic aqueous solution.

[0223] (J-d) Electrochemical graining treatment using aqueous nitric acid solution Continuous electrochemical graining treatment was performed using a 60 Hz AC voltage. The electrolyte used was an aqueous solution of nitric acid 10.4 g / L to which aluminum nitrate was added to adjust the aluminum ion concentration to 4.5 g / L, and the electrolyte temperature was 35°C. The AC power source waveform was the waveform shown in Figure 5, and the time tp until the current value reached its peak from zero was 0.8 msec, the duty ratio was 1:1, and a trapezoidal square wave AC was used. Electrochemical graining treatment was performed using a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode. The electrolytic cell shown in Figure 6 was used. The current density was 30 A / dm at the peak current value. ２ 5% of the current flowing from the power supply was diverted to the auxiliary anode. ２ ) is the total amount of electricity when the aluminum plate is the anode, 185 C / dm ２ It was.

[0224] (Je) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 27% by mass of caustic soda and 2.5% by mass of aluminum ions onto the aluminum plate at a temperature of 50°C. The amount of dissolved aluminum was 3.5 g / m ２ It was.

[0225] (J-f) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L and a liquid temperature of 30°C was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0226] (J-g) Electrochemical graining treatment using a hydrochloric acid solution Continuous electrochemical graining treatment was performed using a 60 Hz AC voltage. The electrolyte used was an aqueous solution of 6.2 g / L hydrochloric acid with aluminum chloride added to adjust the aluminum ion concentration to 4.5 g / L, and the electrolyte temperature was 35°C. The AC power source waveform was the waveform shown in Figure 5, and the time tp until the current value reached its peak from zero was 0.8 msec, the duty ratio was 1:1, and a trapezoidal square wave AC was used. Electrochemical graining treatment was performed using a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode. The electrolytic cell shown in Figure 6 was used. The current density was 25 A / dm at the peak current value.２ and the quantity of electricity in hydrochloric acid electrolysis (C / dm ２ ) is the total amount of electricity when the aluminum plate is the anode, 63 C / dm ２ It was.

[0227] (J-h) Alkali Etching Treatment An 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 aluminum plate at a temperature of 60°C. The amount of dissolved aluminum was 0.2 g / m ２ It was.

[0228] (J-i) Desmutting Treatment Using Acidic Aqueous Solution An aqueous solution of waste liquid (sulfuric acid concentration 170 g / L and aluminum ion concentration 5 g / L) generated in the anodizing treatment step at a liquid temperature of 35°C was sprayed onto the aluminum plate for 4 seconds to perform desmutting treatment.

[0229] (J-j) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in FIG. 3. A 170 g / L aqueous sulfuric acid solution was used as the electrolytic solution, and the solution temperature was 50°C and the current density was 30 A / dm ２ Anodizing treatment was carried out under the conditions of ２ An anodic oxide film was formed.

[0230] (Jk) Pore Widening Treatment The anodized aluminum plate was immersed 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 40° C. for 3 seconds to perform a pore widening treatment.

[0231] (J-l) Second-stage anodizing treatment: The second-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 3. A 170 g / L aqueous sulfuric acid solution was used as the electrolyte, and the solution temperature was 50°C and the current density was 13 A / dm ２ Anodizing treatment was carried out under the conditions of ２ An anodic oxide film was formed.

[0232] (J-m) Hydrophilization Treatment To ensure hydrophilicity in non-image areas, the aluminum plate was subjected to silicate treatment by immersing it in a 2.5% by mass aqueous solution of No. 3 sodium silicate at 50°C for 7 seconds. The amount of Si attached was 8.5 mg / m ２ The average diameter of the micropores was 30 nm. ＊ a ＊ b ＊ Lightness L in the color system ＊ The value was 72.3.

[0233] <Formation of Undercoat Layer> - Formation of Undercoat Layer 1 - An undercoat layer coating solution (1) having the following composition was applied onto a support in a dry coating amount of 0.03 g / m ２ The undercoat layer 1 was formed by coating the mixture in such a manner that the thickness of the undercoat layer 1 becomes 1 / 2 mm.

[0234] <<Undercoat Layer Coating Liquid (1)>> Polyacrylic acid aqueous solution (40% by mass, Jurymer AC-10S, manufactured by Toagosei Co., Ltd.): 3.0 parts Water: 27.0 parts

[0235] - Formation of Undercoat Layer 2 - A coating solution (2) for undercoat layer having the following composition was applied onto the support in a dry coating amount of 0.1 g / m ２ The undercoat layer 2 was formed by coating the mixture so that the thickness became

[0236] <<Coating Liquid for Undercoat Layer (2)>> Undercoat layer compound (3): 0.010 parts Chelest 400 (chelating agent; manufactured by Chelest Co., Ltd.): 0.0280 parts Chelest 3EAF (chelating agent; manufactured by Chelest Co., Ltd.): 0.0499 parts Surfactant (Emalex (registered trademark) 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts Preservative (Biohope L, manufactured by K.I. Kasei Co., Ltd.): 0.00149 parts Water: 2.8219 parts

[0237]

[0238] - Formation of Undercoat Layer 3 - An undercoat layer coating solution (3) having the following composition was applied onto the support in a dry coating amount of 26 mg / m ２ The undercoat layer 3 was formed by coating the undercoat layer 3 so that the thickness of the undercoat layer 3 was 1 / 4 of that of the undercoat layer 3.

[0239] <<Undercoat Layer Coating Solution (3)>> Undercoat layer compound (2) (structure below): 0.013 parts Hydroxyethyliminodiacetic acid: 0.005 parts Tetrasodium ethylenediaminetetraacetate: 0.005 parts Polyoxyethylene lauryl ether: 0.0003 parts Water: 3.15 parts

[0240]

[0241] The numerical value in the parentheses to the right of each structural unit in the compound (2) for undercoat layer indicates the mass ratio, and the numerical value in the parentheses to the right of the ethyleneoxy unit indicates the number of repetitions.

[0242] <Formation of Image Recording Layer> —Formation of Image Recording Layers 1 to 14— For image recording layers 1 to 14, each of the image recording layer coating solutions (image recording layer coating solutions (1) to (13)) having the following composition was applied by bar coating, and dried in an oven at 110° C. for 40 seconds to a dry weight of 0.8 g / m ２ The image recording layers were prepared as follows.

[0243] <<Image Recording Layer Coating Liquids (1) to (14)>> 1-propanol: 5.000 parts 2-butanone: 2.500 parts 1-methoxy-2-propanol: 4.200 parts γ-butyrolactone: 0.1500 parts Water: 0.6600 parts Polymer particles (20% by mass) shown in Table 1: amount shown in Table 1 KLUCEL E ※１ :0.0070 copies ・BYK 336 ※２ : 0.0720 parts Iodonium salt (I-1): 0.9500 parts Infrared absorber (IR-1): 0.4500 parts Polymerizable compound (M-1): 0.4250 parts Polymerizable compound (M-2): 0.2125 parts Color former (S-1): 0.0200 parts *1: Klucel E means hydroxypropyl cellulose available from Hercules. *2: Xylene / methoxypropyl acetate solution containing modified polydimethylsiloxane copolymer at a concentration of 25% by mass (manufactured by BYK Chemical Co.)

[0244]

[0245]

[0246] M-1 is a urethane acrylate (40% by weight solution in 2-butanone) obtained by reacting DESMODUR® N100 (manufactured by Bayer Corp., Milford, CT) with hydroxyethyl acetate and pentaerythritol triacrylate in a molar ratio of approximately 1:1.5:1.5. M-2 is a bisphenol A ethoxylate (10 mole ethylene oxide (EO) adduct) diacrylate (40% by weight solution in 2-butanone).

[0247] - Formation of Image Recording Layer 15 - For the image recording layer 15, an image recording layer coating solution (15) having the following composition was applied by bar coating, and dried in an oven at 120°C for 40 seconds to give a dry weight of 1.0 g / m ２ An image recording layer 15 having the above composition was prepared.

[0248] <<Coating liquid for image recording layer (15)>> Infrared absorber (IR-2 below): 0.0200 parts Infrared absorber (IR-3 below): 0.0050 parts Color former (S-2 below): 0.0300 parts Color former (S-3 below): 0.0120 parts Onium polymerization initiator (I-2 below): 0.0980 parts Borate compound (sodium tetraphenylborate (TPB)): 0.0270 parts Polymerizable compound (M-3 below): 0.4363 parts Fluorine-based surfactant (1) (structure below): 0.004 parts Anionic surfactant (A-1 below, 30%): 0.1620 parts 2-butanone: 6.0000 parts 1-methoxy-2-propanol: 3.7000 parts Methanol: 2.3000 parts Polymer particles (R-1, 20% by mass): 2.2500 parts (Note that Table 1 shows the amounts converted into the amounts in the image recording layer coating solutions (1) to (14)).

[0249]

[0250]

[0251]

[0252]

[0253]

[0254] <<Method for Synthesizing Polymerizable Compound M-3>> 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., 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. To the reaction solution, Neostan U-600 (bismuth-based polycondensation catalyst, manufactured by Nitto Kasei Co., Ltd., 0.11 parts) was added, 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 (polymerizable M-3) solution with a solids content of 70% 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 solution was carried out with an eluent of tetrahydrofuran (THF). The weight average molecular weight was 20,000.

[0255] <Formation of Overcoat Layer> - Formation of Overcoat Layer 1 - An overcoat layer coating solution (1) having the following composition was applied onto the image recording layer with a bar, and then dried in an oven at 120°C for 60 seconds to obtain a dry coating amount of 0.1 g / m ２ An overcoat layer 1 was formed.

[0256] <<Coating Liquid for Overcoat (1)>> Inorganic layered compound dispersion (1) (below): 0.625 parts Hydrophilic polymer (1) (structure below, Mw: 30,000): 0.03 parts Metrose SM04: 0.0600 parts Rapisol A-80 (80% aqueous solution): 0.0063 parts Water: 2.0 parts

[0257] <<Preparation of Inorganic Layered Compound Dispersion (1)>> 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 volume average particle size (laser scattering method) reached 3 μm. The aspect ratio of the resulting dispersed particles was 100 or more.

[0258] - Formation of Overcoat Layer 2 - Overcoat layer coating solution (2) having the following composition was applied onto the image recording layer so as to give a dry film thickness of 1.0 μm, and the coating was oven-dried at 100° C. for 60 seconds to form overcoat layer 2.

[0259] <<Overcoat Layer Coating Solution (2)>> Poval PVA105 (polyvinyl alcohol, saponification degree = 98 mol% to 99 mol%), manufactured by Kuraray Co., Ltd.): 1.0 part by mass PEG4000 (manufactured by Tokyo Chemical Industry Co., Ltd.): 0.39 part by mass Surfactant (Rapisol A-80, manufactured by NOF Corporation): 0.01 part by mass Water: amount that makes the total 10 parts by mass

[0260] As shown in Table 1, each support, undercoat layer, image recording layer, and, if necessary, overcoat layer were formed to obtain lithographic printing plate precursors of Examples 1 to 20 and Comparative Examples 1 and 2, respectively.

[0261] (Evaluation of printing durability) The obtained lithographic printing plate precursor 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). ２The exposed image included a solid image and an AM screen (Amplitude Modulation Screen) 10% halftone dot chart. The exposed plate master obtained was attached to the cylinder of a Heidelberg SX-74 printing press (Kikuban size) without development processing. A 100 L capacity dampening water circulating tank equipped with a nonwoven fabric filter and a temperature control device was connected to this printing press. Eighty liters of 3.5% dampening solution S-Z1 (manufactured by Fujifilm Corporation) was charged into the circulation device, and UV CORE TYPE-A J Sumi GE M (manufactured by T&K TOKA Corporation) was used as the printing ink. After supplying the dampening solution and ink using the standard automatic printing start method, 1,000 sheets were printed on Shiraoi paper (ream weight 48.5 kg, manufactured by Nippon Paper Industries Co., Ltd.) at a printing speed of 10,000 sheets per hour. Further printing was then performed. As the number of prints increased, the image area gradually wore away, resulting in a decrease in ink density on the prints. Printing durability was evaluated by determining the number of prints completed when the dot area ratio of the 10% AM screen dots on the prints, measured using an eXact spectrophotometer (manufactured by X-Rite Corporation), fell 3% from the value measured on the 1,000th print. The relative printing durability was evaluated according to the following criteria, with 50,000 printed sheets being set as 100. The higher the value, the better the printing durability. Relative printing durability = (number of printed sheets of target lithographic printing plate precursor / 50,000) x 100 - Evaluation criteria - 5: The relative printing durability value exceeds 110. 4: The relative printing durability value is greater than 100 and not more than 110. 3: The relative printing durability value is greater than 90 and not more than 100. 2: The relative printing durability value is greater than 75 and not more than 90. 1: The relative printing durability value is 75 or less.

[0262] (Evaluation of on-press development residue suppression (development residue suppression)) The obtained lithographic printing plate precursor was exposed using a Luxel PLATESETTER T-6000III equipped with an infrared semiconductor laser manufactured by Fujifilm Corporation under conditions of an outer drum rotation speed of 1,000 rpm, a laser output of 70%, and a resolution of 2,400 dpi. The exposed image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen. The obtained exposed plate precursor was attached to the plate cylinder of a LITHRONE26 printing press manufactured by Komori Corporation without being developed. Using a dampening solution of Ecology-2 (manufactured by Fujifilm Corporation) / tap water = 2 / 98 (volume ratio) and Space Color Fusion G yellow ink (manufactured by DIC Graphics Corporation), the dampening solution and ink were supplied using the standard automatic print start method of a LITHRONE 26, and on-press development was performed. 500 sheets were printed on Tokubishi Art paper (manufactured by Mitsubishi Paper Mills, Ltd., ream weight: 76.5 kg) at a printing speed of 10,000 sheets per hour. After replacing the plate with a new one, the on-press developability evaluation was repeated three times, and the developer residue adhering to the water roller in the printing press was transferred to cellophane tape, which was then affixed to OK topcoat paper (manufactured by Oji Paper Co., Ltd., model number: OK Topcoat+), and the cyan color density D(C) was measured using a color densitometer X-Rite (manufactured by X-Rite). - Evaluation criteria - Evaluation 1: D(C) is less than 0.1 Evaluation 2: D(C) is 0.1 or more and less than 0.3 Evaluation 3: D(C) is 0.3 or more and less than 0.5 Evaluation 4: D(C) is 0.5 or more and less than 1.0 Evaluation 5: D(C) is 1.0 or more

[0263]

[0264] Details of each polymer particle listed in Table 1 are shown in Table 2.

[0265]

[0266] Synthesis Example 1 (Synthesis of R-1) Under a nitrogen flow, 218 g of 1-propanol and 5 g of polyethylene glycol monomethyl ether acrylate (Mn=232, number of repeating units in the polyethylene oxide structure: 3) were placed in a three-neck flask and heated to 75°C. 10 g of styrene and 35 g of acrylonitrile were mixed, and a solution in which 0.35 g of azobisisobutyronitrile (0.3 mol% based on the monomer) was dissolved was added dropwise over 2 hours. The mixture was then allowed to react for 2 hours at 75°C. The median diameter of the resulting particles (R-1) was measured by dynamic light scattering and was found to be 75 nm.

[0267] <Synthesis Examples 2 to 10: Synthesis of R-2 to R-10> Particles (R-2 to R-10) were synthesized in the same manner as in the synthesis of R-1, except that the mass ratio of each structural unit, the molecular weight of polyethylene glycol monomethyl ether acrylate, and the amount of azobisisobutyronitrile added were changed to the amounts shown in Table 2.

[0268] The abbreviations for the structural units listed in Table 2 represent the structural units formed by the following: St: styrene AN: acrylonitrile PEGMA: polyethylene glycol monomethyl ether acrylate

[0269] The results shown in Table 1 demonstrate that the lithographic printing plate precursors according to the examples are excellent in printing durability and development residue suppression.

[0270] The disclosure of Japanese Patent Application No. 2023-187017, filed on October 31, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0271] 12a, 12b: aluminum support, 14: undercoat layer, 16: image recording layer, 18: aluminum plate, 20a, 20b: anodized film, 22a, 22b: micropores, 24: large diameter hole portion, 26: small diameter hole portion, D: depth of large diameter hole portion, 30: lithographic printing plate precursor, 31: aluminum plate, 32, 34: roller-shaped brush, 33: polishing slurry liquid, 35, 36, 37, 38: support roller, 50: main electrolytic cell, 51: AC power source, 52: radial drum roller, 53a, 53b: main electrode, 54: electrolyte supply port, 55: electrolyte, 56: auxiliary anode, 57: electrolyte passage, 58: auxiliary anode, 60: auxiliary anode cell, 610: Anodizing treatment device, 612: power supply tank, 614: electrolytic treatment tank, 616: aluminum plate, 618, 26: electrolyte, 620: power supply electrode, 622, 628: rollers, 624: nip roller, 630: electrolytic electrode, 632: tank wall, 634: DC power supply, W: aluminum plate, S: liquid supply direction, Ex: electrolyte discharge direction, ta: anode reaction time, tc: cathode reaction time, tp: time required for current to reach peak from 0, Ia: peak current on the anode cycle side, Ic: peak current on the cathode cycle side, AA: current of the anode reaction of the aluminum plate, CA: current of the cathode reaction of the aluminum plate

Claims

1. An on-press development type lithographic printing plate precursor comprising a support and an image recording layer on the support, the image recording layer containing a polymerizable compound and polymer particles, the median diameter of the polymer particles being 50 nm to 120 nm, the content of the polymer particles being 42% by mass or more and 90% by mass or less with respect to the total mass of the image recording layer, and a cross-section of the thickness direction of the lithographic printing plate precursor is stained with osmium, and then the cross-section image obtained by observing the cross-section with a scanning electron microscope is binarized into dyed and undyed portions, the standard deviation of the area ratio of the undyed portions of the cross-section image being less than 6.

2. The on-press type lithographic printing plate precursor according to claim 1, wherein the polymer particles are polymer particles having a structural unit formed from an acrylonitrile compound and a polyalkylene oxide structure.

3. The on-press development type lithographic printing plate precursor according to claim 2, wherein the polymer particles are polymer particles having a structural unit formed from an aromatic vinyl compound, a structural unit formed from an acrylonitrile compound, and a structural unit having a polyalkylene oxide structure.

4. The on-press development type lithographic printing plate precursor according to claim 2, wherein the polyalkylene oxide structure is a polyethylene oxide structure.

5. The on-press development type lithographic printing plate precursor according to claim 2, wherein the number of repeating units of the polyalkylene oxide structure is 3 to 10.

6. The on-press development type lithographic printing plate precursor according to claim 2, wherein the content of the constitutional unit having a polyalkylene oxide structure in the polymer particles is 10% by mass or more based on the total mass of the polymer.

7. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the content of the polymer particles is 45% by mass or more based on the total mass of the image recording layer.

8. The on-press development type lithographic printing plate precursor according to claim 7, wherein the content of the polymer particles is 55% by mass or more based on the total mass of the image recording layer.

9. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the polymer particles have a median diameter of 50 nm to 100 nm.

10. The on-press development type lithographic printing plate precursor according to claim 9, wherein the polymer particles have a median diameter of 50 nm to 90 nm.

11. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the polymerizable compound contains an oligomer.

12. An on-press development type lithographic printing plate precursor according to claim 1 or 2, further comprising an intermediate layer between the support and the image recording layer, the intermediate layer comprising a copolymer having a support-adsorbing group and a hydrophilic group.

13. The on-press development type lithographic printing plate precursor according to claim 1 or 2, further comprising an overcoat layer on the image recording layer, the overcoat layer containing an inorganic layer compound.

14. An on-press development type lithographic printing plate precursor as described in claim 1 or 2, further comprising an overcoat layer on the image recording layer containing a water-soluble polymer, the overcoat layer having a thickness greater than that of the image recording layer.

15. An on-press development type lithographic printing plate precursor according to claim 1 or claim 2, which has an oxide film on the surface of the support, and the oxide film has micropores extending in the depth direction from the surface of the oxide film on the image recording layer side, and the micropores have large diameter pores on the surface of the oxide film having an average pore diameter of 15 nm to 100 nm, and small diameter pores that communicate with the bottoms of the large diameter pores and extend further in the depth direction from the communicating positions and have an average pore diameter of 15 nm or less.

16. An on-press development type lithographic printing plate precursor according to claim 1 or 2, which has an oxide film on the surface of the support, the oxide film having micropores extending in the depth direction from the surface of the oxide film on the image recording layer side, and the maximum diameter of the micropores inside the micropores is 1.2 to 10 times the average pore diameter of the oxide film surface.

17. An on-press development type lithographic printing plate precursor comprising a support and an image recording layer on the support, the image recording layer containing a polymerizable compound and polymer particles, the median diameter of the polymer particles being 50 nm to 120 nm, the content of the polymer particles being 42% by mass or more and 90% by mass or less relative to the total mass of the image recording layer, and the polymer particles having, relative to the total mass of the polymer particles, 65% by mass or more of structural units formed by an acrylonitrile compound and 10% by mass or more of structural units having a polyalkylene oxide structure.

18. A method for producing a lithographic printing plate, comprising the steps of: exposing the on-press development type lithographic printing plate precursor according to claim 1 or claim 17 in an imagewise manner; and supplying at least one selected from the group consisting of printing ink and fountain solution on the printing press to remove the image recording layer in non-image areas.

19. A lithographic printing method comprising the steps of: exposing the on-press development type lithographic printing plate precursor according to claim 1 or claim 17 in an imagewise manner; 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 to prepare a lithographic printing plate; and printing with the obtained lithographic printing plate.

Images