Lithographic printing plate precursor, manufacturing method for lithographic printing plate, and printing method

Abstract

The present invention addresses the problem of providing a lithographic printing plate precursor in which the occurrence of abnormalities in appearance when left in high-humidity conditions is suppressed and the occurrence of scumming is suppressed, as well as providing a manufacturing method for the lithographic printing plate, and a printing method. This lithographic printing plate precursor has a support and an image recording layer which contains an onium salt. The support has an aluminum plate and an anodized film, and the anodized film is disposed on the surface of the support on the side having the image recording layer. The Fe content is more than 0.40 mass% with respect to the total mass of the aluminum plate, the Mg content is more than 0.25 mass% with respect to the total mass of the aluminum plate, the Zn content is more than 0.05 mass% with respect to the total mass of the aluminum plate, the Ti content is more than 0.03 mass% with respect to the total mass of the aluminum plate, and the combined Cr and Zr content is more than 0.03 mass% and at most 0.08 mass% with respect to the total mass of the aluminum plate.

Description

Planographic printing plate precursor, method for manufacturing planographic printing plates, printing method

[0001] The present invention relates to a lithographic printing plate precursor, a method for producing a lithographic printing plate, and a printing method.

[0002] Lithographic printing utilizes the mutual repulsion of water and oil-based ink by creating a difference in ink adhesion on the surface of a lithographic printing plate, with the lipophilic image areas serving as ink-receptive areas and the hydrophilic non-image areas serving as fountain solution-receptive areas (ink-non-receptive areas). The ink is then applied only to the image areas, and the ink is then transferred to a substrate such as paper for printing. To produce a lithographic printing plate having lipophilic image areas and hydrophilic non-image areas, a lithographic printing plate precursor (PS plate) comprising a lipophilic photosensitive resin layer (image-recording layer) on a hydrophilic support is widely used. Lithographic printing plate precursors are typically produced by exposing the plate through an original image such as lithographic film, leaving the image areas of the image-recording layer, and dissolving and removing the remaining unnecessary image-recording layer with an alkaline developer or organic solvent, thereby exposing the hydrophilic support surface and forming non-image areas.

[0003] An example of such a lithographic printing plate precursor is described in Patent Document 1. Patent Document 1 describes a technology relating to a lithographic printing plate precursor comprising a metal support obtained by forming a hydrophilic coating having a thermal conductivity in the film thickness direction of 0.05 to 0.5 W / (m·K) on a metal substrate that has been subjected to a surface roughening treatment, and an image recording layer that is cured by exposure to an infrared laser provided on the metal support.

[0004] Japanese Patent Application Laid-Open No. 2003-287894

[0005] The present inventors have studied the properties of lithographic printing plate precursors with reference to Patent Document 1, and have found that there are cases where abnormalities occur in the appearance of lithographic printing plate precursors left under high-humidity conditions, or where printing stains occur when printing is performed using the lithographic printing plate precursors, and that there is room for further improvement in lithographic printing plate precursors.

[0006] In view of the above circumstances, an object of the present invention is to provide a lithographic printing plate precursor that is suppressed from causing abnormal appearance when left under high-humidity conditions and that is suppressed from causing printing stains. Another object of the present invention is to provide a method for producing a lithographic printing plate, and a printing method.

[0007] The present inventors have found that the above problems can be solved by the following configuration.

[0008] [1] A lithographic printing plate precursor having a support and an image recording layer containing an onium salt, wherein the support has an aluminum plate and an anodized film, the anodized film being disposed on the surface of the support facing the image recording layer, and the aluminum plate has an Fe content of more than 0.40% by mass, relative to the total mass of the aluminum plate, an Mg content of more than 0.25% by mass, relative to the total mass of the aluminum plate, an Zn content of more than 0.05% by mass, relative to the total mass of the aluminum plate, an Ti content of more than 0.03% by mass, and a total content of Cr and Zr of more than 0.03% by mass but not more than 0.08% by mass, relative to the total mass of the aluminum plate. [2] The lithographic printing plate precursor according to [1], wherein the aluminum plate has an Fe content of more than 0.40% by mass and not more than 0.50% by mass, a Ti content of more than 0.03% by mass and not more than 0.05% by mass, and a combined Cr and Zr content of more than 0.03% by mass and not more than 0.05% by mass, relative to the total mass of the aluminum plate. [3] The lithographic printing plate precursor according to [1] or [2], wherein the aluminum plate has an Mg content of more than 0.25% by mass and not more than 0.32% by mass, relative to the total mass of the aluminum plate, and a Zn content of more than 0.05% by mass and not more than 0.07% by mass, relative to the total mass of the aluminum plate. [4] The lithographic printing plate precursor according to any one of [1] to [3], wherein the aluminum plate has a Si content of 0.25% by mass or less, relative to the total mass of the aluminum plate, a Cu content of 0.05% by mass or less, relative to the total mass of the aluminum plate, and a Mn content of 0.05% by mass or less, relative to the total mass of the aluminum plate. [5] The lithographic printing plate precursor according to any one of [1] to [4], wherein the average Si atomic weight calculated by measuring a circular region having a diameter of 30 mm on the surface of the anodized coating facing the image recording layer by X-ray fluorescence analysis is 0.008 to 0.140 mg. [6] The lithographic printing plate precursor according to any one of [1] to [5], wherein the image recording layer is a negative-tone image recording layer.[7] A method for producing a lithographic printing plate, comprising: an exposure step of imagewise exposing the image recording layer of the lithographic printing plate precursor according to any one of [1] to [6] to form exposed areas and unexposed areas, and an on-press development step of supplying at least one of printing ink and fountain solution on a printing press to remove the imagewise exposed unexposed areas of the image recording layer, thereby producing a lithographic printing plate. [8] A printing method, comprising: an exposure step of imagewise exposing the image recording layer of the lithographic printing plate precursor according to any one of [1] to [6] to form exposed areas and unexposed areas, an on-press development step of supplying at least one of printing ink and fountain solution on a printing press to remove the imagewise exposed unexposed areas of the image recording layer, thereby producing a lithographic printing plate, and a printing step of carrying out printing using the produced lithographic printing plate.

[0009] According to the present invention, it is possible to provide a lithographic printing plate precursor that is suppressed from causing abnormal appearance when left under high-humidity conditions and that is suppressed from causing printing stains. Furthermore, according to the present invention, it is possible to provide a method for producing a lithographic printing plate and a printing method.

[0010] Fig. 1 is a schematic cross-sectional view showing an example of the configuration of an on-press development type lithographic printing plate precursor of the present invention. Fig. 2 is a schematic cross-sectional view showing an example of an embodiment of an anodic oxide film. Fig. 3 is a schematic cross-sectional view showing another example of an embodiment of an anodic oxide film. Fig. 4 is a graph showing an example of an alternating waveform current waveform used in hydrochloric acid electrolysis in a method for producing a support. Fig. 5 is a side view showing an example of a radial cell used in hydrochloric acid electrolysis using alternating current in a method for producing a support. Fig. 6 is a schematic view of an anodizing treatment device used in anodizing treatment in the production of a support.

[0011] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. In this specification, "(meth)acrylic" is a term used to encompass both acrylic and methacrylic, and "(meth)acryloyl" is a term used to encompass both acryloyl and methacryloyl. The term "process" in this specification 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. Unless otherwise specified, measurements of each physical property value are performed at 25°C. Unless otherwise specified, each component in a composition or each structural unit in a polymer in this specification may be contained alone or in combination of two or more types. As used herein, the amount of each component in a composition or the amount of each structural unit in a polymer refers to the total amount of the corresponding substances or structural units present in the composition or the corresponding structural units present in the polymer, unless otherwise specified, when multiple substances or structural units corresponding to each component or each structural unit in the polymer are present in the composition. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. As used herein, "same" includes the error range generally accepted in the technical field. Unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) used herein are molecular weights obtained by detecting the molecular weight of the target compound in a THF (tetrahydrofuran) solvent with a differential refractometer using a gel permeation chromatography (GPC) analyzer equipped with columns TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all product names manufactured by Tosoh Corporation), and converting the molecular weight using polystyrene as a standard. In this specification, the term "lithographic printing plate precursor" includes not only lithographic printing plate precursors but also throwaway plate precursors.The term "lithographic printing plate" encompasses not only lithographic printing plates prepared by subjecting a lithographic printing plate precursor to operations such as exposure and development as necessary, but also throwaway plates. In the case of throwaway plates, the operations of exposure and development are not necessarily required. A throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when printing a portion of the page in monochrome or two colors, for example, in color newspaper printing. In this specification, the term "on-press development type" means that the lithographic printing plate precursor can be used for on-press development. In this specification, "excellent printing durability" means that the lithographic printing plate can print a large number of sheets.

[0012] [Lithographic Printing Plate Precursor] The lithographic printing plate precursor according to the present invention comprises a support and an image recording layer. The support comprises an aluminum plate and an anodized film.

[0013] The structure of the lithographic printing plate precursor of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing one example of the structure of the lithographic printing plate precursor of the present invention. The lithographic printing plate precursor 10 shown in FIG. 1 has a support 11 and an image recording layer 12. The support 11 has an aluminum plate 13 and an anodized film 14. The anodized film 14 is disposed on the surface of the support 11 facing the image recording layer 12. The structure of the lithographic printing plate precursor is not limited to the embodiment shown in FIG. 1. For example, as described below, an undercoat layer may be provided between the support and the image recording layer, or a protective layer may be provided on the surface of the image recording layer opposite the support.

[0014] [Support] The lithographic printing plate precursor according to the present invention has a support having an aluminum plate and an anodized film. The anodized film in the support is located on the image recording layer side. In other words, the lithographic printing plate precursor has an aluminum plate, an anodized film, and an image recording layer in this order. Hereinafter, the term "support" refers to a support having an aluminum plate and an anodized film, unless otherwise specified.

[0015] <Aluminum Plate> The aluminum plate in the lithographic printing plate precursor of the present invention contains dimensionally stable aluminum as a main component, and further, the composition of the aluminum plate with respect to the contents of each of Fe (iron), Mg (magnesium), Zn (zinc), and Ti (titanium), and the total content of Cr (chromium) and Zr (zirconium) satisfies the following condition A. (Condition A) The Fe content is more than 0.40% by mass, relative to the total mass of the aluminum plate. The Mg content is more than 0.25% by mass, relative to the total mass of the aluminum plate. The Zn content is more than 0.05% by mass, relative to the total mass of the aluminum plate. The Ti content is more than 0.03% by mass, relative to the total mass of the aluminum plate. The total content of Cr and Zr is more than 0.03% by mass and not more than 0.08% by mass, relative to the total mass of the aluminum plate.

[0016] The present inventors have discovered and completed a lithographic printing plate precursor having a support and an image recording layer containing an onium salt, and have found that, when the composition of the aluminum plate of the support satisfies the above-mentioned condition A, the occurrence of appearance abnormalities and the occurrence of printing stains can be suppressed when the plate is stored under high-humidity conditions. The mechanism by which the lithographic printing plate precursor of the present invention achieves the above-mentioned excellent effects is presumed to be as follows. It is presumed that, when the image recording layer contains an onium salt, anions derived from the onium salt are eluted to the interface between the image recording layer and the support over time during storage of the lithographic printing plate precursor, particularly under high-humidity conditions, and may affect corrosion of the support. Corrosion-caused areas on the support can cause appearance abnormalities. In contrast, in the lithographic printing plate precursor of the present invention, it is presumed that a specific metal element contained in a predetermined amount in the aluminum plate is eluted or precipitated to the interface between the support and the image recording layer during storage under high-humidity conditions, and interacts with anions derived from the onium salt, thereby suppressing corrosion of the support and preventing appearance abnormalities when the plate is stored under high-humidity conditions. On the other hand, if the aluminum plate contains too much Cr and Zr, it is presumed that local defects will occur in the process of forming the anodized coating, reducing the developability of the image recording layer and causing staining during printing using the lithographic printing plate precursor. In the lithographic printing plate precursor according to the present invention, it is presumed that by ensuring that the total content of Cr and Zr does not exceed a predetermined upper limit, it is possible to suppress the occurrence of the above-mentioned local defects in the anodized coating and to suppress the occurrence of staining during printing using the lithographic printing plate precursor.

[0017] The Fe content is more than 0.40% by mass relative to the total mass of the aluminum plate. The upper limit of the Fe content is not particularly limited, but is, for example, 0.53% by mass or less relative to the total mass of the aluminum plate. In terms of being more excellent in terms of suppressing appearance abnormalities under high-humidity conditions and suppressing print staining, the Fe content is preferably 0.50% by mass or less, and more preferably 0.45% by mass or less.

[0018] The Mg content is more than 0.25% by mass relative to the total mass of the aluminum plate. The upper limit of the Mg content is not particularly limited, but is preferably 0.32% by mass or less, and more preferably 0.30% by mass or less, relative to the total mass of the aluminum plate.

[0019] The Zn content is more than 0.05% by mass relative to the total mass of the aluminum plate. The upper limit of the Zn content is not particularly limited, but is, for example, 0.08% by mass or less relative to the total mass of the aluminum plate. In terms of superior printing durability, the Zn content is preferably 0.07% by mass or less, and more preferably 0.06% by mass or less.

[0020] The Ti content is more than 0.03 mass% relative to the total mass of the aluminum plate. The upper limit of the Ti content is not particularly limited, but is, for example, 0.07 mass% or less relative to the total mass of the aluminum plate, and is preferably 0.05 mass% or less, more preferably 0.04 mass% or less, from the viewpoint of being more excellent in suppressing appearance abnormalities under high-humidity conditions and suppressing print staining.

[0021] The total content of Cr and Zr is more than 0.03 mass% and not more than 0.08 mass%, relative to the total mass of the aluminum plate. In terms of being more excellent in terms of suppressing appearance abnormalities under high-humidity conditions and suppressing print stains, the total content of Cr and Zr is preferably more than 0.03 mass% and not more than 0.05 mass%, and more preferably more than 0.03 mass% and not more than 0.04 mass%.

[0022] The aluminum plate may contain at least one selected from the group consisting of Si (silicon), Cu (copper), and Mn (manganese). The Si content is, for example, 0.28% by mass or less, relative to the total mass of the aluminum plate, and is preferably 0.25% by mass or less in terms of superior printing durability. The lower limit of the Si content is not particularly limited, but is preferably more than 0.12% by mass, more preferably more than 0.15% by mass, relative to the total mass of the aluminum plate. The Cu content is, for example, 0.08% by mass or less, relative to the total mass of the aluminum plate, and is preferably 0.05% by mass or less in terms of superior printing durability. The lower limit of the Cu content is not particularly limited, but is preferably more than 0.03% by mass, more preferably more than 0.04% by mass, relative to the total mass of the aluminum plate. The Mn content is, for example, 0.08% by mass or less, relative to the total mass of the aluminum plate, and is preferably 0.05% by mass or less in terms of superior printing durability. The lower limit of the Mn content is not particularly limited, but is preferably more than 0.01 mass%, more preferably more than 0.03 mass%, based on the total mass of the aluminum plate. As the aluminum plate, an aluminum plate having the Si, Cu, and Mn contents each falling within the above ranges is particularly preferred.

[0023] The aluminum plate may contain impurity elements other than Fe, Mg, Zn, Ti, Cr, Zr, Si, Cu, Mn, and Al. The total content of the impurity elements is preferably 0.03 mass% or less, more preferably 0.01 mass% or less, based on the total mass of the aluminum plate. The total content of the impurity elements may be 0 mass% based on the total mass of the aluminum plate. Examples of impurity elements include V, Be, Ca, S, K, and Na.

[0024] The aluminum plate preferably contains 96% by mass or more, more preferably 98% by mass or more, and may contain the remainder excluding Fe, Mg, Zn, Ti, Cr, Zr, Si, Cu, and Mn.

[0025] Suitable examples of the aluminum plate include aluminum plates having the following compositions. Note that the contents of each metal are expressed relative to the total mass of the aluminum plate. (1) An aluminum plate having an Fe content of more than 0.40% by mass and not more than 0.53% by mass, an Mg content of more than 0.25% by mass, a Zn content of more than 0.05% by mass, a Ti content of more than 0.03% by mass and not more than 0.07% by mass, and a total Cr and Zr content of more than 0.03% by mass and not more than 0.08% by mass. (2) An aluminum plate according to (1), having an Fe content of more than 0.40% by mass and not more than 0.50% by mass, a Ti content of more than 0.03% by mass and not more than 0.05% by mass, and a total Cr and Zr content of more than 0.03% by mass and not more than 0.05% by mass. (3) The aluminum sheet of (1) or (2), having a Mg content of more than 0.25% by mass but not more than 0.32% by mass, and a Zn content of more than 0.05% by mass but not more than 0.08% by mass. (4) The aluminum sheet of any of (1) to (3), having a Mg content of more than 0.25% by mass but not more than 0.32% by mass, and a Zn content of more than 0.05% by mass but not more than 0.07% by mass. (5) The aluminum sheet of any of (1) to (4), having a Si content of 0.28% by mass or less, a Cu content of 0.08% by mass or less, and a Mn content of 0.08% by mass or less. (6) The aluminum sheet of any of (1) to (5), having a Si content of 0.25% by mass or less, a Cu content of 0.05% by mass or less, and a Mn content of 0.05% by mass or less. (7) The aluminum sheet of any one of (1) to (6), having a Si content of more than 0.12% by mass and not more than 0.25% by mass, a Cu content of more than 0.03% by mass and not more than 0.05% by mass, and a Mn content of more than 0.01% by mass and not more than 0.05% by mass. (8) The aluminum sheet of any one of (1) to (7), having an Al content of 98% by mass or more. (9) The aluminum sheet of any one of (1) to (8), having the remainder being Al.

[0026] The content of each metal contained in the aluminum plate can be measured, for example, by the emission spectroscopic analysis method for aluminum and aluminum alloys described in Japanese Industrial Standard JIS H 1305:2005. When performing the above measurement, the surface of the support having the anodized film and the aluminum plate opposite the image recording layer (hereinafter also referred to as the "target surface") is wiped with acetone to remove oil and used as a measurement sample. If inorganic substances including the anodized film and backcoat are attached to the target surface, they are removed from the target surface using a removal method appropriate for each substance before measurement. If removal is difficult, the target surface may be mechanically polished and mirror-finished.

[0027] An aluminum plate having the above-described composition can be obtained by, for example, manufacturing the aluminum plate using a raw material prepared by adding a metal selected from Fe, Mg, Zn, Ti, Cr, Zr, Si, Cu, and Mn to aluminum ingot to obtain a target composition. For example, high-purity aluminum ingot is used as the aluminum ingot. Alternatively, a recycled aluminum plate may be used as the aluminum ingot. The recycled aluminum plate may be obtained by carrying out a recycling process two or more times.

[0028] <Anodic oxide film> The anodic oxide film on the support is a film formed on the surface of the aluminum plate by anodizing treatment. The amount of the anodic oxide film is not particularly limited, but from the viewpoint of more excellent scratch resistance, it is preferable that the amount of the anodic oxide film is 2.0 g / m ２ More than 3.2 g / m is preferable. ２ More preferably, 3.4 g / m or more ２ The upper limit is not particularly limited, but is preferably 5.0 g / m ２ In most cases, it is 4.0 g / m ２ The following is preferred:

[0029] (Micropores) The anodized film has a plurality of micropores (fine holes) formed on the surface of the anodized film on the image recording layer side (hereinafter also referred to as the "film surface"). The micropores extend from the film surface in the depth direction (the direction toward the aluminum plate, the thickness direction). A large number of micropores are formed on the film surface, and in many cases, each is uniformly distributed on the film surface. Note that "micropores" is a term commonly used to describe the pore structure formed in the anodized film by anodizing treatment, and does not specify the size of the pores.

[0030] The density of micropores on the surface of the coating is not particularly limited, but from the viewpoint of achieving both on-press developability and printing durability, it is preferably 200 to 2000 pores / μm ２ is preferably 400 to 1500 particles / μm ２ The density of micropores is determined by observing the surface of the coating using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, and measuring the density of micropores by 400 × 600 nm in four images obtained by observing four different points. ２ A measurement area is arbitrarily selected, the number of micropores present in the measurement area is measured, the number of micropores per area of ​​the measurement area is calculated for each image, and the calculated values ​​are arithmetically averaged to obtain the value.

[0031] The average diameter (average opening diameter) of the micropores on the coating surface is preferably 15 to 100 nm, more preferably 20 to 50 nm, and even more preferably 23 to 35 nm, in terms of superior printing durability. The average diameter of the micropores was measured by observing the coating surface using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, and measuring 400 × 600 nm in four images obtained by observing the surface at four different locations. ２ The "equivalent circle diameter" is a value obtained by arbitrarily selecting a measurement area, measuring the diameters of the micropores present in the measurement area, and arithmetically averaging all the measured values. Note that if the shape of the openings of the micropores on the coating surface is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" refers to the diameter of a circle that has the same projected area as the projected area of ​​the opening.

[0032] The opening rate of the micropores on the surface of the coating is preferably 10 to 90%, more preferably 30 to 85%, from the viewpoint of achieving both on-press developability and printing durability. The opening rate is a value calculated by multiplying the average area of ​​the openings of the large-diameter pores of the micropores, calculated using the average radius obtained by dividing the average diameter of the large-diameter pores of the micropores on the surface of the coating by 2, by the density (number density) of the micropores on the surface of the coating, and converting the result into a percentage.

[0033] The depth of the micropores is not particularly limited, but from the viewpoint of achieving both on-press developability and printing durability, it is preferably 0.01 to 1 μm, more preferably 0.05 to 0.6 μm, and even more preferably 0.07 to 0.25 μm. The micropore depth refers to the distance in the depth direction from the surface of the micropore film to the deepest part of the bottom of the micropore. The micropore depth is a value obtained by observing a cross section of the anodized film along the depth direction with an FE-SEM at a magnification of 150,000 times, randomly selecting 25 or more micropores from four observation images obtained by observing four different cross sections, measuring the depths of the selected micropores, and arithmetically averaging the measured values.

[0034] The shape of the micropores is not particularly limited, and may be a substantially straight tube (substantially cylindrical) in which the diameter of the micropores remains almost constant in the depth direction, or the diameter of the micropores may change continuously or discontinuously in the depth direction. Examples of shapes in which the diameter of the micropores changes in the depth direction include a cone shape in which the diameter decreases in the depth direction, a truncated cone shape in which the diameter increases in the depth direction, and a shape in which a plurality of pores with different diameters are connected in the depth direction, as described below. Furthermore, the shape of the bottom of the micropore is not particularly limited, and may be a curved (convex) shape or a flat shape.

[0035] The shape of the micropores will be described in more detail below with reference to the drawings. It should be noted that the shape of the micropores in the anodized film of the present invention is not limited to the embodiments shown in the drawings. The size of each micropore portion described below is a value obtained by observing the cross section of the micropore along the depth direction of the anodized film using an FE-SEM at a magnification of 150,000 times, randomly selecting 25 or more micropores from four images obtained by observing four different cross sections, measuring the size of the target portion of the selected micropores, and arithmetically averaging the measured values.

[0036] Fig. 2 is a schematic cross-sectional view showing one example of an embodiment of an anodized coating. The anodized coating 14A shown in Fig. 2 has micropores 20 composed of large-diameter pores 22 and small-diameter pores 24. The large-diameter pores 22 are pores that extend from the coating surface 21 (the surface of the anodized coating 14A facing the image recording layer, not shown) to a depth D1 and communicate with the small-diameter pores 24 at their bottoms 22A. The small-diameter pores 24 are pores that communicate with the bottoms 22A of the large-diameter pores 22 and extend from a communication position 23 to a depth D2.

[0037] The average diameter of the large-diameter pores 22 at the coating surface 21 is the same as the average diameter of the micropores at the coating surface described above, and the preferred range of the average diameter and the measurement method are also the same. The depth D1 of the large-diameter pores (the distance from the coating surface 21 to the bottom 22A) is preferably 0.05 to 0.50 μm, more preferably 0.08 to 0.30 μm, and even more preferably 0.10 to 0.30 μm, in terms of superior printing durability.

[0038] When the anodized coating has micropores composed of large-diameter pores and small-diameter pores, the shape of the large-diameter pores is not limited to the substantially straight tubular shape (substantially cylindrical shape) shown in FIG. 2 , and the diameter of the large-diameter pores may vary continuously or discontinuously in the depth direction. Examples of shapes in which the diameter of the large-diameter pores varies in the depth direction include a truncated cone shape in which the diameter decreases in the depth direction, a truncated cone shape in which the diameter increases in the depth direction, and a shape in which multiple pores with different diameters are connected in the depth direction (see FIG. 3 ). The shape of the large-diameter pores is preferably substantially straight tubular. The shape of the bottom of the large-diameter pore is not particularly limited, and may be a curved (convex) shape like the bottom 22A shown in FIG. 2 or a flat shape.

[0039] It is also preferable that the large diameter pores have an internal maximum diameter portion in an internal region located deeper than the coating surface, where the pore diameter is larger than the average diameter at the coating surface. Examples of shapes having an internal maximum diameter portion include a shape in which a plurality of pores with different diameters are connected along the depth direction from the coating surface, as in the anodized oxide coating 14B shown in Figure 3 described below, and a truncated cone shape whose diameter increases along the depth direction. When the large diameter pores have an internal maximum diameter portion, the ratio of the average maximum diameter d1 inside the large diameter pores to the average diameter d1 at the coating surface of the large diameter pores is ｍａｘ (See Figure 3) ｍａｘ / d1) is preferably 1.1 to 10.0, more preferably 1.1 to 5.0.

[0040] The small diameter pores 24 are pores that communicate with the bottoms 22A of the large diameter pores 22 and extend further in the depth direction from the communication positions 23. In the micropore 20 shown in Figure 2, one large diameter pore 22 communicates with one small diameter pore 24, but the micropore may have two or more small diameter pores that communicate with one large diameter pore.

[0041] The average diameter d2 of the small diameter holes 24 at the communication positions 23 is not particularly limited as long as it is smaller than the average diameter d1 of the large diameter holes 22 at the coating surface, but from the viewpoint of better on-machine developability, it is preferably 15 nm or less, more preferably 13 nm or less, even more preferably 11 nm or less, and particularly preferably 10 nm or less. There is no particular lower limit, but it is preferably 5 nm or more.

[0042] The depth D2 of the small diameter hole portion 24 (the distance from the communication position 23 with the large diameter hole portion 22 to the bottom 24A of the small diameter hole portion 24) is preferably 0.1 to 5 μm, more preferably 0.2 to 4 μm, even more preferably 0.3 to 3 μm, and particularly preferably 0.5 to 1.8 μm, from the viewpoint of achieving both scratch resistance and productivity.

[0043] The shape of the small diameter hole is not limited to the substantially straight tubular shape (substantially cylindrical shape) shown in Fig. 2, and may be, for example, a conical shape whose diameter decreases in the depth direction, or a truncated conical shape whose diameter increases in the depth direction. The shape of the small diameter hole is preferably a substantially straight tubular shape. The shape of the bottom of the small diameter hole is not particularly limited, and may be a curved (convex) shape like bottom 24A shown in Fig. 2, or a flat shape.

[0044] The ratio (d1 / d2) of the average diameter d1 at the coating surface 21 of the large diameter hole portions 22 to the average diameter d2 at the communication positions 23 of the small diameter hole portions 24 is preferably 1.1 to 13, and more preferably 1.5 to 6.5. The ratio (D1 / D2) of the depth D1 of the large diameter hole portions 22 to the depth D2 of the small diameter hole portions 24 is preferably 0.005 to 50, and more preferably 0.025 to 40.

[0045] Figure 3 is a schematic cross-sectional view showing another example of an anodized coating. The anodized coating 14B shown in Figure 3 has micropores 30 each composed of a large-diameter pore portion 32 and a small-diameter pore portion 34. The large-diameter pore portion 32 is composed of an upper large-diameter pore portion 36 and a lower large-diameter pore portion 38. In the micropores 30, the upper large-diameter pore portion 36, the lower large-diameter pore portion 38, and the small-diameter pore portion 34 are all interconnected. The upper large-diameter pore portion 36 is a pore that extends from the coating surface 31 (the surface of the anodized coating 14B facing the image recording layer, not shown) to a depth D1u and is interconnected with the lower large-diameter pore portion 38 at a bottom 36A. Large diameter hole lower portion 38 corresponds to the maximum diameter portion described above, and is a hole portion that communicates with bottom portion 36A of large diameter hole upper portion 36, extends from communication position 37 with large diameter hole upper portion 36 to a position of depth D1b, and communicates with small diameter hole portion 34 at bottom portion 38A. Small diameter hole portion 34 is a hole portion that communicates with bottom portion 38A of large diameter hole lower portion 38, and extends from communication position 39 with large diameter hole lower portion 38 to bottom 36A at a position of depth D2.

[0046] The average diameter of the upper large-diameter hole portions 36 at the coating surface 31 is the same as the average diameter of the large-diameter hole portions at the coating surface described above, and the preferred average diameter range and measurement method are also the same. The sum of the depth D1u of the upper large-diameter hole portions 36 (the distance from the coating surface 31 to the bottom portion 36A) and the depth D1b of the lower large-diameter hole portions 38 (the distance from the bottom portion 36A to the bottom portion 38A) corresponds to the depth D1 of the large-diameter hole portions, and is preferably 0.05 to 0.5 μm. From the viewpoint of achieving both on-press developability and printing durability, the depth D1u of the upper large-diameter hole portions 36 is preferably 0.02 to 0.2 μm, more preferably 0.05 to 0.1 μm. Furthermore, from the viewpoint of achieving both on-press developability and printing durability, the depth D1b of the lower large-diameter hole portions 38 is preferably 0.05 to 0.3 μm, more preferably 0.05 to 0.2 μm.

[0047] The shape of the upper part of the large diameter hole is not limited to the substantially straight tubular shape (substantially cylindrical shape) shown in Fig. 3, but may be, for example, a conical shape whose diameter decreases in the depth direction, or a truncated conical shape whose diameter increases in the depth direction. The shape of the upper part of the large diameter hole is preferably substantially straight tubular.

[0048] The large diameter hole lower portion 38 is a hole portion that communicates with the bottom portion 36A of the large diameter hole upper portion 36 and extends further in the depth direction from the communicating position 37. As shown in FIG. 3, the maximum diameter of the large diameter hole lower portion 38 is equal to the maximum diameter d1 inside the large diameter hole 32. ｍａｘ From the viewpoint of achieving both on-press developability and printing durability, the maximum diameter of the large-diameter hole lower portions 38 is preferably 0.02 to 0.2 μm, more preferably 0.03 to 0.1 μm, and even more preferably 0.04 to 0.08 μm. Furthermore, from the viewpoint of achieving both on-press developability and printing durability, the ratio of the maximum diameter of the large-diameter hole lower portions 38 to the average diameter of the large-diameter hole upper portions 36 on the coating surface 31 ((maximum diameter of the large-diameter hole lower portions 38) / (average diameter of the large-diameter hole upper portions 36 on the coating surface 31)) is preferably 1.2 to 10.0, and more preferably 1.2 to 5.0.

[0049] The shape of the lower portion of the large-diameter hole is not limited to the substantially straight tubular shape (substantially cylindrical shape) shown in Figure 3, but may be, for example, a conical shape whose diameter decreases in the depth direction, or a truncated conical shape whose diameter increases in the depth direction. The shape of the lower portion of the large-diameter hole is preferably a substantially straight tubular shape. The shape of the bottom of the lower portion of the large-diameter hole is not particularly limited, and may be a curved (convex) shape or a flat shape.

[0050] The small diameter hole portion 34 is a hole portion that communicates with the bottom portion 38A of the large diameter hole portion lower portion 38 and extends further in the depth direction from the communication position 39. The shape and size of the small diameter hole portion 34, including preferred aspects, are similar to those of the small diameter hole portion 24 already described.

[0051] The structure of the micropores in the anodized coating is not limited to the embodiments shown in Figures 2 and 3. For example, as described above, the large-diameter pores may have a structure in which three or more pores with different diameters are connected to each other along the depth direction.

[0052] (Si atomic weight) The average Si atomic weight (hereinafter also referred to as the "specific Si atomic weight") calculated by measuring a 30 mm diameter circular region on the image recording layer side of the anodized coating on the support by X-ray fluorescence analysis is preferably 0.005 to 0.200 mg, more preferably 0.008 to 0.140 mg, and more preferably 0.030 to 0.140 mg, in order to achieve superior printing durability of the lithographic printing plate precursor. The specific Si atomic weight is obtained by performing X-ray fluorescence analysis on a 30 mm diameter circular region on the coating surface, measuring the Kα ray intensity of the Si element, and then quantifying the Si atomic weight present on the coating surface using a calibration curve. Here, the "average Si atomic weight" refers to a value obtained by selecting three or more non-overlapping circular regions on the image recording layer side of the anodized coating, determining the Si atomic weight for each region, and then arithmetically averaging the Si atomic weights obtained for each region. Details of the method for measuring the specific Si atomic weight by X-ray fluorescence analysis are described in the Examples below.

[0053] In the support of a lithographic printing plate precursor, a method for adjusting the specific Si atomic content on the surface of an anodized film within the above range includes, for example, forming an anodized film having the above micropores on an aluminum plate, and then subjecting the formed anodized film to a silicate treatment (described later) by changing any one of the silicate concentration in the treatment solution, the temperature of the treatment solution, and the treatment time.

[0054] If necessary, the support may have a backcoat layer on the surface facing the aluminum plate, which contains an organic polymer compound described in JP-A-5-045885 or a silicon alkoxy compound described in JP-A-6-035174.

[0055] <Method for manufacturing the support> The support used in the lithographic printing plate precursor of the present invention can be manufactured by a known method using the above-mentioned aluminum plate. Examples of the method for manufacturing the support include a method comprising a roughening step of roughening an aluminum plate, and an anodizing step of anodizing the roughened aluminum plate to form an aluminum anodized film on the aluminum plate. Also preferred is a method further comprising a silicate treatment step, described below, of the aluminum plate having the anodized film formed by the above treatment. The above-mentioned steps and optional treatments are described in detail below. The aluminum plate used for manufacturing the support, including preferred embodiments, is as described above.

[0056] (Surface Roughening Treatment Step) The surface roughening treatment step is a step of roughening the surface of an aluminum plate. As the surface roughening treatment, one or a combination of two or more of mechanical roughening treatment, chemical roughening treatment, and electrochemical roughening treatment is generally used. In terms of being able to efficiently produce a predetermined support, the surface roughening treatment step is preferably performed by subjecting the aluminum plate to a hydrochloric acid treatment solution which may contain sulfuric acid, at a temperature of the hydrochloric acid treatment solution of 30°C or less, and at a total electrical quantity participating in the anodic reaction of the aluminum plate of 500 C / dm ２ Below this, the peak current value of the AC current waveform is 80 A / dm ２ The method preferably includes a hydrochloric acid electrolysis step in which alternating current electrolysis is performed to produce a surface-roughened aluminum plate. When the hydrochloric acid treatment solution contains sulfuric acid, the ratio of the content of sulfuric acid to the content of hydrochloric acid is preferably 0.1 or less.

[0057] (Mechanical Graining Treatment) In the method for producing a support, mechanical graining treatment may be performed before the hydrochloric acid electrolysis step. Examples of the mechanical graining treatment method include a wire brush graining method in which the surface of an aluminum plate is scratched with a metal wire, a ball graining method in which the surface of an aluminum plate is grained with abrasive balls and an abrasive, and a brush graining method in which the surface is grained with a nylon brush and an abrasive, as described in JP-A-6-135175 and JP-B-50-040047.

[0058] (Hydrochloric Acid Electrolysis Treatment Step) The hydrochloric acid electrolysis treatment step included in the method for producing a support includes subjecting an aluminum plate to electrolysis in a hydrochloric acid treatment solution which may contain sulfuric acid, at a temperature of the hydrochloric acid treatment solution of 30°C or less, and at a total quantity of electricity participating in the anodic reaction of the aluminum plate of 500 C / dm ２ Below this, the peak current value of the AC current waveform is 80 A / dm ２ The following step is preferably a hydrochloric acid electrolysis step in which an aluminum plate is subjected to alternating current electrolysis to produce a surface-roughened aluminum plate. By performing such hydrochloric acid electrolysis and then anodizing treatment, which will be described later, the above-mentioned lithographic printing plate precursor can be efficiently produced.

[0059] The hydrochloric acid treatment solution contains hydrochloric acid. The hydrochloric acid concentration in the hydrochloric acid treatment solution is preferably 5 to 30 g / L, more preferably 10 to 20 g / L. The hydrochloric acid treatment solution may contain sulfuric acid. When the hydrochloric acid treatment solution contains sulfuric acid, the sulfuric acid concentration in the hydrochloric acid treatment solution is preferably 2.0 g / L or less, more preferably 1.0 g / L or less, and even more preferably 0.5 g / L. When the hydrochloric acid treatment solution contains sulfuric acid, the lower limit of the sulfuric acid concentration in the hydrochloric acid treatment solution is not particularly limited, and may be greater than 0 g / L. The hydrochloric acid treatment solution may contain aluminum ions. When the hydrochloric acid treatment solution contains aluminum ions, the concentration of aluminum ions is preferably 1.0 to 30.0 g / L, more preferably 5.0 to 20.0 g / L. When the hydrochloric acid treatment solution contains sulfuric acid, the ratio of the sulfuric acid content to the hydrochloric acid content is preferably 0.1 or less. The lower limit is not particularly limited, and may be greater than 0. The temperature of the hydrochloric acid treatment solution is preferably 30° C. or lower, more preferably 26° C. or lower, and even more preferably 23° C. or lower. There is no particular lower limit, but the temperature is preferably 10° C. or higher, and more preferably 15° C. or higher.

[0060] In the hydrochloric acid electrolysis process, the total amount of electricity (the total amount of electricity involved in the anodic reaction of the aluminum plate at the time when the hydrochloric acid electrolysis process is completed) is 500 C / dm ２ Preferably, 350 C / dm or less ２ The lower limit of the total amount of electricity is not particularly limited, but is preferably 50 C / dm ２ More than 200 C / dm ２More preferably, the peak current value of the AC current waveform is 80 A / dm ２ Preferably, 70 A / dm or less ２ The peak current value is more preferably 10 A / dm or less. ２ More than 20 A / dm ２ The above is more preferable.

[0061] The alternating current waveform for hydrochloric acid electrolysis can be a sine wave, a square wave, a trapezoidal wave, a triangular wave, or the like. The frequency is preferably 0.1 to 250 Hz. FIG. 4 is a graph showing an example of an alternating current waveform diagram used for hydrochloric acid electrolysis. In FIG. 4, ta is the anode reaction time, tc is the cathode reaction time, tp is the time it takes for the current to reach its peak from 0, Ia is the peak current on the anode cycle side, and Ic is the peak current on the cathode cycle side. In the trapezoidal wave, the time it takes for the current to reach its peak from 0, tp, is preferably 1 to 10 msec. The conditions for one cycle of AC used in hydrochloric acid electrolysis are preferably such that the ratio tc / ta of the anode reaction time ta of the aluminum plate to the cathode reaction time tc is 1 to 20, the ratio Qc / Qa of the quantity of electricity Qc when the aluminum plate is the anode to the quantity of electricity Qa when the aluminum plate is the anode is 0.3 to 20, and the anode reaction time ta is 5 to 1000 msec. The current density is the peak value of the trapezoidal wave, and both the anode cycle side Ia and the cathode cycle side Ic of the current are within the above-mentioned range (80 A / dm ２ (see below) is preferred.

[0062] The apparatus shown in FIG. 5 can be used for hydrochloric acid electrolysis using AC. FIG. 5 is a side view showing an example of a radial cell used for hydrochloric acid electrolysis using AC. In FIG. 5 , 50 denotes a main electrolytic cell, 51 denotes an AC power source, 52 denotes radial drum rollers, 53a and 53b denote main electrodes, 54 denotes an electrolyte supply port, 55 denotes an electrolyte, 56 denotes a slit, 57 denotes an electrolyte passage, 58 denotes an auxiliary anode, 60 denotes an auxiliary anode cell, and W denotes an aluminum plate. When two or more electrolytic cells are used, the electrolysis conditions may be the same or different. The aluminum plate W is wound around a radial drum roller 52 immersed in the main electrolytic cell 50 and electrolyzed by the main electrodes 53a and 53b connected to an AC power source 51 during transport. Electrolyte 55 is supplied from the electrolyte supply port 54 through a slit 56 to an electrolyte passage 57 between the radial drum roller 52 and the main electrodes 53a and 53b. The aluminum sheet W treated in the main electrolytic cell 50 is then electrolyzed in an auxiliary anode cell 60. In this auxiliary anode cell 60, an auxiliary anode 58 is disposed opposite the aluminum sheet W, and an electrolytic solution 55 is supplied so as to flow through the space between the auxiliary anode 58 and the aluminum sheet W.

[0063] (Alkaline Etching Treatment) In the method for producing a support, it is preferable to carry out an alkaline etching treatment after the mechanical graining treatment described above, or before or after the hydrochloric acid electrolysis treatment described above. The alkaline etching treatment carried out before the hydrochloric acid electrolysis treatment is carried out for the purpose of removing rolling oil, dirt, and natural oxide films on the surface of the aluminum plate (rolled aluminum) if no mechanical graining treatment has been carried out, or for the purpose of dissolving the edges of the irregularities generated by the mechanical graining treatment and changing the sharp irregularities into a surface with a smooth undulation if the mechanical graining treatment has already been carried out.

[0064] When mechanical roughening treatment is not performed before the alkaline etching treatment, the etching amount is 0.1 to 10 g / m ２ is preferred, and 1 to 5 g / m ２ The etching amount is more preferably 1 to 10 g / m ２In this case, rolling oil, dirt, natural oxide film, etc., on the surface can be sufficiently removed. When mechanical roughening treatment is performed before alkaline etching treatment, the etching amount is 3 to 20 g / m ２ is preferred, and 5 to 15 g / m ２ is more preferred.

[0065] The alkaline etching treatment carried out immediately after the hydrochloric acid electrolysis is carried out for the purposes of dissolving smut formed in the acidic electrolyte and dissolving the edges of the irregularities formed by the hydrochloric acid electrolysis. The irregularities formed by the hydrochloric acid electrolysis differ depending on the type of electrolyte, and therefore the optimal etching amount also differs. However, the etching amount of the alkaline etching treatment carried out after the hydrochloric acid electrolysis is 0 to 0.5 g / m. ２ is preferred, and 0 to 0.3 g / m ２ is more preferred.

[0066] Examples of alkalis used in the alkaline solution include caustic alkalis and alkali metal salts. In particular, an aqueous solution of caustic soda is preferred.

[0067] The concentration of the alkaline solution can be determined depending on the etching amount, but is preferably 1 to 50 mass %, more preferably 10 to 35 mass %. When aluminum ions are dissolved in the alkaline solution, the concentration of the aluminum ions is preferably 0.01 to 10 mass %, more preferably 3 to 8 mass %. The temperature of the alkaline solution is preferably 20 to 90°C. The treatment time is preferably 0 to 120 seconds.

[0068] Examples of methods for contacting an aluminum plate with an alkaline solution include a method of passing the aluminum plate through a tank containing the alkaline solution, a method of immersing the aluminum plate in a tank containing the alkaline solution, and a method of spraying the alkaline solution onto the surface of the aluminum plate.

[0069] (Desmutting Treatment) In the method for producing a support, after the hydrochloric acid electrolysis or alkali etching treatment, it is preferable to perform pickling (desmutting treatment) to remove corrosive organisms remaining on the surface. Examples of acids used in the desmutting treatment include nitric acid, sulfuric acid, and hydrochloric acid, but other acids may also be used. The desmutting treatment is carried out, for example, by contacting the aluminum plate with an acidic solution (containing 0.01 to 5% by mass of aluminum ions) of hydrochloric acid, nitric acid, sulfuric acid, or the like, with a concentration of 0.5 to 30% by mass. Examples of methods for contacting the aluminum plate with the acidic solution include passing the aluminum plate through a tank containing the acidic solution, immersing the aluminum plate in a tank containing the acidic solution, and spraying the acidic solution onto the surface of the aluminum plate. Since the surface condition of the aluminum plate after the desmutting treatment affects the subsequent growth of a natural oxide film, the choice of acid, its concentration, and temperature conditions are appropriately selected depending on the purpose.

[0070] (Water washing treatment) In the method for producing a support, it is preferable to wash with water after completion of each of the above-mentioned treatment steps. In particular, washing with water at the end of the steps should be carried out thoroughly using pure water, well water, tap water, etc., because washing with water at the end of the steps affects the subsequent growth of a natural oxide film.

[0071] (Anodizing Treatment Step (First Anodizing Treatment Step)) The anodizing treatment step is a step in which an anodizing treatment is performed on the aluminum plate whose surface has been roughened by the above-mentioned surface roughening treatment step, thereby forming an anodized aluminum film on the aluminum plate. The anodizing treatment step may be performed once or multiple times. The procedure for the anodizing treatment step is not particularly limited, and known methods may be used. In the anodizing treatment step, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, or the like may be used as the electrolytic bath. For example, the sulfuric acid concentration may be 100 to 300 g / L. The anodizing treatment conditions are appropriately set depending on the electrolytic solution used, and may be, for example, a solution temperature of 5 to 70°C (preferably 10 to 60°C), a current density of 0.5 to 60 A / dm 2 (preferably 5 to 60 A / dm 2), voltage 1 to 100 V (preferably 5 to 50 V), electrolysis time 1 to 100 seconds (preferably 5 to 60 seconds), and coating amount 0.1 to 5 g / m 2 (preferably 0.2 to 3 g / m 2 ) are listed.

[0072] In the method for producing the support, the electrolytic bath used in the anodizing treatment step is preferably an aqueous solution containing sulfuric acid or phosphoric acid, in order to further increase the adhesion between the support and the image recording layer.

[0073] (Pore widening treatment step) The pore widening treatment step is a treatment (pore size enlargement treatment) step in which the aluminum plate on which the anodized film has been formed is subjected to an etching treatment after the above-mentioned anodized treatment step to enlarge the diameter of the micropores in the anodized film. The pore widening treatment can be carried out by contacting the aluminum plate obtained by the above-mentioned anodized treatment step with an acid aqueous solution or an alkaline aqueous solution. The contact method is not particularly limited, and examples thereof include an immersion method and a spray method.

[0074] (Second Anodizing Treatment) In the method for producing a support, it is preferable to carry out a second anodizing treatment step in which further anodizing treatment is carried out after the above-mentioned first anodizing treatment and pore widening treatment. The procedure of the second anodizing treatment step is not particularly limited, and known methods can be used. In the second 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 to 300 g / L. The conditions for the second anodizing treatment are appropriately set depending on the electrolytic solution used, but for example, a solution temperature of 5 to 70°C (preferably 10 to 60°C), a current density of 0.5 to 60 A / dm 2 (preferably 5 to 60 A / dm 2 ), voltage 1 to 100 V (preferably 5 to 50 V), electrolysis time 1 to 100 seconds (preferably 5 to 60 seconds), and coating amount 0.1 to 5 g / m 2 (preferably 0.2 to 3 g / m 2 The electrolytic bath used in the second anodizing treatment step is preferably an aqueous solution containing sulfuric acid or phosphoric acid, and more preferably an aqueous solution containing sulfuric acid.

[0075] (Third Anodizing Treatment Step) In the method for producing a support, after the first anodizing treatment and the pore widening treatment described above and before the second anodizing treatment described above, a step (third anodizing treatment step) of further anodizing treatment in a phosphoric acid solution to form an anodized film with larger pore diameters may be performed. The procedure for the third anodizing treatment step is not particularly limited, and known methods may be used. In the third anodizing treatment step, an aqueous phosphoric acid solution may be used as the electrolytic bath. For example, the concentration of phosphoric acid in the aqueous phosphoric acid solution may be 10 to 300 g / L. The conditions for the third anodizing treatment are appropriately set depending on the electrolytic solution used, and may be, for example, a solution temperature of 5 to 70°C (preferably 10 to 60°C), a current density of 0.5 to 60 A / dm 2 (preferably 5 to 60 A / dm 2 ), voltage 1 to 100 V (preferably 5 to 50 V), electrolysis time 1 to 100 seconds (preferably 5 to 60 seconds), and coating amount 0.1 to 5 g / m 2 (preferably 0.2 to 3 g / m 2 The electrolytic bath used in the third anodizing treatment is preferably an aqueous solution containing phosphoric acid.

[0076] (Silicate Treatment Step) The method for producing a support preferably includes a silicate treatment step in which an aluminum plate on which an anodized film has been formed by the above-mentioned anodizing treatment and pore widening treatment is subjected to silicate treatment. This is because the silicate treatment step makes it possible to easily produce a support having a specific Si atomic weight within a predetermined range. The silicate treatment is a treatment in which an aqueous solution containing an alkali metal silicate such as sodium silicate or potassium silicate (hereinafter also referred to as "treatment liquid") is brought into contact with the anodized film formed on the aluminum plate. In the silicate treatment, it is preferable to immerse the aluminum plate having the anodized film in the treatment liquid. For silicate treatment, reference can be made to the methods and procedures described in U.S. Pat. Nos. 2,714,066 and 3,181,461, the disclosures of which are incorporated herein by reference.

[0077] Examples of alkali metal silicates used in the silicate treatment include sodium silicate, potassium silicate, and lithium silicate. In addition to the alkali metal silicate, the treatment solution may further contain an appropriate amount of an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. The treatment solution may also contain an alkaline earth metal salt or a Group 4 (Group IVA) metal salt. Examples of alkaline earth metal salts include nitrates such as calcium nitrate, strontium nitrate, magnesium nitrate, and barium nitrate; sulfates; hydrochlorides; phosphates; acetates; oxalates; and borates. Examples of Group 4 (Group IVA) metal salts include titanium tetrachloride, titanium trichloride, potassium titanium fluoride, potassium titanium oxalate, titanium sulfate, titanium tetraiodide, zirconium oxide chloride, zirconium dioxide, zirconium oxychloride, and zirconium tetrachloride. These alkaline earth metal salts and Group 4 (Group IVA) metal salts may be used alone or in combination of two or more.

[0078] The treatment conditions for the silicate treatment and the concentration of the treatment solution are appropriately adjusted depending on the size of the aluminum plate and anodized film to be treated, as well as the structure and density of the micropores. The content of the alkali metal silicate in the treatment solution is, for example, 3 to 30 mass %, and preferably 3 to 10 mass %, relative to the total mass of the treatment solution. The temperature of the treatment solution used for the silicate treatment is, for example, 30 to 80°C, and more preferably 40 to 70°C. The treatment time for the silicate treatment is, for example, 1 to 15 seconds, and more preferably 3 to 10 seconds.

[0079] [Image Recording Layer] The lithographic printing plate precursor according to the present invention has an image recording layer. The image recording layer is preferably an image recording layer that is removable with at least one of printing ink and fountain solution. The image recording layer is preferably a negative image recording layer, and more preferably a water-soluble or water-dispersible negative image recording layer. Each component contained in the image recording layer will be described below.

[0080] <Onium Salt> The image recording layer contains an onium salt. The onium salt refers to a salt containing an onium ion or a derivative thereof generated by protonation of a hydride, and an anion (counter anion) that is a counter ion. Examples of the onium ion include an iodonium ion, a sulfonium ion, an azinium ion, an ammonium ion, a phosphonium ion, a fluoronium ion, a chloronium ion, and an oxonium ion.

[0081] The onium salt contained in the image recording layer is preferably a compound that functions as a polymerization initiator (hereinafter also referred to as an "onium-based polymerization initiator"), and more preferably a polymerization initiator that generates radicals as polymerization initiating species by the energy of light, heat, or both, and initiates the polymerization of a compound having a polymerizable unsaturated group (so-called radical polymerization initiator). Examples of onium-based polymerization initiators include compounds that, when electrons of an infrared absorber are excited by infrared exposure, accept electrons through intermolecular electron transfer to generate polymerization initiating species such as radicals. Examples of onium salts and onium-based polymerization initiators include the compounds described in paragraphs 0028 to 0030 of JP-A-2008-195018, the disclosures of which are incorporated herein by reference.

[0082] As the onium salt, an iodonium salt, a sulfonium salt or an azinium salt is preferred, an iodonium salt or a sulfonium salt is more preferred, and an iodonium salt is even more preferred, in terms of superior printing durability.

[0083] As the iodonium salt compound, diaryliodonium salt compounds are preferred, and diphenyliodonium salt compounds substituted with an electron-donating group, such as an alkyl group or an alkoxy group, are more preferred, and asymmetric diphenyliodonium salt compounds are even more preferred. Specific examples of the iodonium salt compound include the compounds described in European Patent No. 104,143, U.S. Pat. Nos. 339,049 and 410,201, and Japanese Patent Laid-Open Nos. 2-150848 and 2-296514.

[0084] As the counter anion of the iodonium salt compound and the sulfonium salt compound, a sulfonamide anion or a sulfonimide anion is preferred, and a sulfonimide anion is more preferred. As the sulfonamide anion, an arylsulfonamide anion is preferred. As the sulfonimide anion, a bisarylsulfonimide anion is preferred. Specific examples of the sulfonamide anion or the sulfonimide anion include the compounds described in WO 2020 / 262692.

[0085] The onium salt may be used alone or in combination of two or more kinds. The content of the onium salt is preferably from 0.1 to 50% by mass, more preferably from 0.5 to 30% by mass, and even more preferably from 0.8 to 20% by mass, based on the total mass of the image recording layer.

[0086] <Infrared absorbing agent> The image recording layer preferably contains an infrared absorbing agent. The infrared absorbing agent is not particularly limited, and examples thereof include pigments and dyes.

[0087] As the dye used as the infrared absorber, commercially available dyes and known dyes described in literature such as "Dye Handbook" (edited by the Society of Organic Synthetic Chemistry, published in 1970) can be used. Specific examples include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complex dyes. Among these dyes, cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes are preferred, cyanine dyes or indolenine cyanine dyes are more preferred, and cyanine dyes are even more preferred.

[0088] 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, and cyanine dyes are more preferred from the viewpoints of availability, solvent solubility during the introduction reaction, and the like.

[0089] 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, the compounds described in paragraphs

[0012] to

[0037] of JP-A-2002-040638, the compounds described in paragraphs

[0034] to

[0041] of JP-A-2002-278057, the compounds described in paragraphs

[0080] to

[0086] of JP-A-2008-195018, the compounds described in paragraphs

[0035] to

[0043] of JP-A-2007-090850, 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. 5-005005 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.

[0090] The infrared absorber preferably contains an infrared absorber that decomposes due to exposure to infrared rays (a decomposable infrared absorber), and more preferably contains a decomposition-coloring infrared absorber. It is presumed that by using a decomposable infrared absorber as the infrared absorber, the decomposable infrared absorber or its decomposition products promote polymerization, and further, the decomposition products of the decomposable infrared absorber interact with the polymerizable compound, thereby improving printing durability.

[0091] The decomposable infrared absorber preferably has a substituent that is cleaved by infrared light or heat. The substituent that is cleaved by infrared light exposure or heat is a substituent that has a bond that is cleaved by any of the energy generated when returning from an excited state generated by infrared light absorption to a ground state, a chemical reaction that proceeds from the excited state, and heat generated by infrared light. The decomposable infrared absorber preferably has a function of absorbing infrared light generated by infrared light exposure and converting the absorbed infrared light into heat.

[0092] 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 to 1,400 nm, more preferably an infrared absorbent having a maximum absorption wavelength in the wavelength region of 760 to 900 nm. Furthermore, 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 to 600 nm.

[0093] 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) of the decomposable infrared absorber to the LUMO (lowest unoccupied molecular orbital) undergo intramolecular electron transfer to an electron-accepting group (a group having a potential close to that of the LUMO) in the molecule, resulting in decomposition.

[0094] Preferred specific examples of the infrared absorber (particularly an infrared absorber that decomposes upon exposure to infrared light) include compounds described in WO 2020 / 262692, JP 2008-544322 A, WO 2016 / 027886 A, WO 2019 / 219560 A, and JP 2023-138231 A, the descriptions of which are incorporated herein by reference.

[0095] The infrared absorbing agent may be used alone or in combination of two or more. Furthermore, a pigment and a dye may be used in combination as the infrared absorbing agent. The content of the infrared absorbing agent in the image recording layer is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 5.0% by mass, based on the total mass of the image recording layer.

[0096] <Acid Color Former> The image recording layer may contain an acid color former, and preferably contains an acid color former. In this specification, "acid color former" refers to a compound that develops color in the presence of an electron-accepting compound such as an acid, thereby changing the color of the image recording layer. The acid color former is preferably a compound that develops color when heated in a state in which it has accepted an electron-accepting compound such as an acid. Examples of the acid include protonic acids and Lewis acids. The heating temperature during the heating is preferably 80 to 200°C, and more preferably 100 to 180°C.

[0097] Examples of acid color formers include compounds having a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, and amide, and are colorless compounds in which the partial skeleton rapidly undergoes ring-opening or cleavage upon contact with an electron-accepting compound. Among these, from the viewpoints of color development and visibility, the acid color former preferably contains a leuco dye, and more preferably is a leuco dye. From the viewpoints of color development and visibility, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure.

[0098] Preferred specific examples of the acid color former (particularly the leuco dye) include the compounds described in JP-A No. 2023-138231, the disclosure of which is incorporated herein by reference.

[0099] These acid color formers may be used alone or in combination of two or more. The content of the acid color former is preferably from 0.5 to 10% by mass, more preferably from 1 to 5% by mass, based on the total mass of the image recording layer.

[0100] <Polymerization initiator> The image recording layer may contain a polymerization initiator other than an onium salt (hereinafter also referred to as "another polymerization initiator"). The other polymerization initiator 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 does not contain an onium ion. As the other polymerization initiator, a compound that generates a radical by the energy of light, heat, or both, and initiates polymerization of a compound having a polymerizable unsaturated group (so-called radical polymerization initiator) is preferred.

[0101] Examples of the other polymerization initiator include an electron-accepting polymerization initiator other than an onium salt (hereinafter also referred to as "another electron-accepting polymerization initiator") and an electron-donating polymerization initiator. It is more preferable that the image recording layer contains an electron-donating polymerization initiator as the other polymerization initiator together with the onium salt.

[0102] (Other Electron-Accepting Polymerization Initiators) The other electron-accepting polymerization initiator 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 does not contain an onium ion. As the other electron-accepting polymerization initiator, known thermal polymerization initiators, compounds having a bond with small bond dissociation energy, photopolymerization initiators, etc. can be used as appropriate.

[0103] The other electron-accepting polymerization initiator is preferably a radical polymerization initiator, such as (a) an organic halide, (b) a carbonyl compound, (c) an azo compound, (d) an organic peroxide, (e) a metallocene compound, (f) an azide compound, (g) a hexaarylbiimidazole compound, (i) a disulfone compound, and (j) an oxime ester compound.

[0104] (a) Examples of organic halides include the compounds described in paragraphs 0022 and 0023 of JP-A No. 2008-195018. (b) Examples of carbonyl compounds include the compounds described in paragraph 0024 of JP-A No. 2008-195018. (c) Examples of azo compounds include the azo compounds described in JP-A No. 8-108621. (d) Examples of organic peroxides include the compounds described in paragraph 0025 of JP-A No. 2008-195018. (e) Examples of metallocene compounds include the compounds described in paragraph 0026 of JP-A No. 2008-195018. (f) Examples of azide compounds include compounds such as 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone. (g) Examples of hexaarylbiimidazole compounds include the compounds described in JP-A-2008-195018, paragraph 0027. (i) Examples of disulfone compounds include the compounds described in JP-A-61-166544 and JP-A-2002-328465.

[0105] The other electron-accepting polymerization initiators may be used alone or in combination of two or more. When the image recording layer contains the other electron-accepting polymerization initiator, the total content of the onium salt and the other electron-accepting polymerization initiator is preferably 0.1 to 50% by mass, more preferably 0.5 to 30% by mass, and still more preferably 0.8 to 20% by mass, based on the total mass of the image recording layer.

[0106] (Electron-Donating Polymerization Initiator) The polymerization initiator preferably contains an electron-donating polymerization initiator, as this provides superior chemical resistance and printing durability in the lithographic printing plate. Examples of electron-donating polymerization initiators include the following compounds: (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 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) and N-phenyliminodiacetic acid (which may have a substituent on the phenyl group). (iii) Sulfur-containing compounds: Compounds in which the nitrogen atom of the above aminoacetic acid compounds is replaced with a sulfur atom can generate active radicals by a similar action. Specific examples include phenylthioacetic acid (which may have a substituent on the phenyl group). (iv) Tin-containing compounds: The nitrogen atoms of the aminoacetic acid compounds described above are replaced with tin atoms, which can generate active radicals through the same action. (v) Sulfinates: These can generate active radicals through oxidation. Specific examples include sodium arylsulfinate. Specific examples of electron-donating polymerization initiators include the electron-donating polymerization initiators described in International Publication No. 2020 / 262692.

[0107] The image recording layer preferably contains a borate compound as an electron-donating polymerization initiator. The borate compound is preferably a tetraarylborate compound or a monoalkyltriarylborate compound, and from the viewpoint of compound stability, a tetraarylborate compound is more preferred, and a tetraphenylborate compound is even more preferred. The counter cation of the borate compound is not particularly limited, but is preferably an alkali metal ion or a tetraalkylammonium ion, and more preferably a sodium ion, a potassium ion, or a tetrabutylammonium ion. The borate compound is preferably sodium tetraphenylborate. When the image recording layer contains an onium salt and a borate compound as an electron-donating polymerization initiator, the image recording layer exhibits better visibility, printing durability, and stability over time.

[0108] One embodiment of the borate compound is a borate compound represented by the following formula (1) (hereinafter also referred to as a "specific borate compound"). The borate compound represented by formula (1) is used as an electron-donating polymerization initiator in the image recording layer. The specific borate compound is a compound that generates polymerization initiating species such as radicals and cations by the energy of light, heat, or both.

[0109]

[0110] In formula (1), R １ , R ２ , R ３ and R ４ each independently represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkenyl group, or an unsubstituted or substituted alkynyl group; R １ , R ２ , R ３ and R ４ may each independently have a ring structure. １ , R ２ , R ３ and R ４ At least one of them is different from the others. ＋ represents a cation.

[0111] R １, R ２ , R ３ or R ４ Examples of the alkyl group represented by the formula (I) include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, s-butyl, t-butyl, isopentyl, neopentyl, 1-methylbutyl, isohexyl, 2-ethylhexyl, 2-methylhexyl, cyclohexyl, cyclopentyl, and 2-norbornyl. The alkyl group may be linear, branched, or have a ring structure.

[0112] Also, R １ , R ２ , R ３ or R ４ The alkyl group represented by the formula (R) may have a substituent. Examples of the substituent of the alkyl group include a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, a sulfonyl group, an amino group, an amide group, and a combination thereof. １ , R ２ , R ３ or R ４ The alkyl groups represented by the formula (I) are each independently preferably an unsubstituted, linear or branched alkyl group having 1 to 12 carbon atoms, more preferably an unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms, and even more preferably an unsubstituted, linear or branched alkyl group having 1 to 6 carbon atoms. Of these, from the viewpoint of suppressing development defects over time, a branched, unsubstituted alkyl group is particularly preferred.

[0113] R １ , R ２ , R ３ or R ４Examples of the aryl group represented by the formula (I) include aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, anthryl, phenanthryl, indenyl, acenabutenyl, and fluorenyl. Examples of the substituent on the aryl group include the above-mentioned alkyl group substituents. １ , R ２ , R ３ or R ４ The aryl groups represented by the following formula (I) are each independently preferably an unsubstituted or substituted phenyl group.

[0114] R １ , R ２ , R ３ or R ４ Examples of the alkenyl group represented by R include alkenyl groups having 2 to 20 carbon atoms, such as vinyl, 1-propenyl, 1-butenyl, cinnamyl, and 2-chloro-1-ethenyl. １ , R ２ , R ３ or R ４ The alkenyl group represented by the formula (I) may be linear, branched, or have a ring structure. Examples of the substituent of the alkenyl group include the above-mentioned substituents of the alkyl group. １ , R ２ , R ３ or R ４ The alkenyl groups represented by the following formula (I) are each independently preferably an unsubstituted alkenyl group having 2 to 20 carbon atoms.

[0115] R １ , R ２ , R ３ or R ４ Examples of the alkynyl group represented by the formula (I) include alkynyl groups having 2 to 20 carbon atoms, such as an ethynyl group, a 1-propynyl group, a 1-butynyl group, a trimethylsilylethynyl group, a phenylethynyl group, etc. The alkynyl group may be linear or branched.

[0116] Among the above functional groups, R １ , R ２ , R ３ and R ４are preferably each independently a substituted or unsubstituted aryl group. １ , R ２ , R ３ and R ４ are each independently a substituted or unsubstituted aryl group, the HOMO potential of the borate compound is lowered, improving the film stability of the image recording layer, thereby extending the life of the lithographic printing plate.

[0117] In this disclosure, R １ , R ２ , R ３ and R ４ At least one of them is different from the others. １ , R ２ , R ３ and R ４ Among them, R １ , R ２ and R ３ are identical, and R ４ But, R １ , R ２ and R ３ This allows a high purity borate compound to be obtained. In addition, the generation of radicals can be suppressed, making it difficult for side reactions to occur. In the above case, R １ , R ２ and R ３ However, it is more preferably a phenyl group.

[0118] Also, R １ , R ２ , R ３ and R ４ It is also preferred that at least two of R are phenyl groups and at least one is a substituted aryl group. １ , R ２ and R ３ is a phenyl group, and R ４ is more preferably an aryl group having a substituent (i.e., a substituted aryl group).

[0119] R １ , R ２ and R ３ is a phenyl group, and R ４When the aryl group has a substituent, the total number of carbon atoms and oxygen atoms in the substituent of the aryl group is preferably 2 or more, and more preferably 3 or more. The upper limit is, for example, 8 or less.

[0120] The compound represented by formula (1) is preferably a compound represented by the following formula (II):

[0121]

[0122] In formula (II), R represents an alkyl group having two or more carbon atoms or an alkoxy group having two or more carbon atoms and oxygen atoms in total. ＋ represents an iodonium cation or an infrared absorbing dye cation.

[0123] In formula (II), the alkyl group represented by R preferably has 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms. Examples of the alkyl group include an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, an isobutyl group, a sec-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a neopentyl group, and an isopropyl group. The alkyl group may be linear, branched, or have a ring structure.

[0124] In formula (II), the alkoxy group represented by R preferably has a total of 2 to 4 carbon atoms and oxygen atoms. Examples of the alkoxy group include a methoxy group, an n-propoxy group, an isopropoxy group, and an n-butoxy group. The alkoxy group may be linear or branched.

[0125] In addition, in formula (1), R １ , R ２ or R ３ The phenyl group represented by the formula (I) is preferably a phenyl group substituted with an electron-withdrawing group. Examples of the electron-withdrawing group include a halogen atom and a fluoroalkyl group. Among these, a fluorine atom, a chlorine atom, and a fluoroalkyl group having 1 to 3 carbon atoms are preferred.

[0126] In formula (1), R ４ The substituent that the aryl group represented by the formula (I) has is preferably an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, or an amide group, more preferably an alkyl group, an alkenyl group, or an alkoxy group, and still more preferably an alkyl group or an alkoxy group.

[0127] In the present disclosure, the compound represented by the above formula (1) may be a compound represented by the following formula (I):

[0128]

[0129] In formula (I), R represents a group having a total of 2 or more carbon atoms and oxygen atoms, X represents a halogen atom, an alkyl group, or an alkoxy group, and the sum of the Hammett values ​​of R and X is −0.09 to 0.09. ＋ Li ＋ , Na ＋ , K. ＋ , iodonium cation or infrared absorbing dye cation.

[0130] Examples of R in formula (I) include an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, a sulfonyl group, an amide group, and combinations thereof.

[0131] In formula (I), examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, and a bromine atom. The alkyl group and alkoxy group represented by X in formula (I) are the same as the alkyl group and alkoxy group in formula (II), and preferred embodiments are also the same.

[0132] In particular, R in formula (I) is preferably an alkyl group having 2 to 4 carbon atoms or an alkoxy group having 2 to 4 carbon atoms in total, and more preferably an alkyl group having 2 to 4 carbon atoms. In the above case, X is preferably a halogen atom. Here, the halogen atoms may each independently be different halogen atoms, but it is more preferable that all of them are the same halogen atom.

[0133] In formula (I), the sum of the Hammett σ values ​​of the substituents (R and X) introduced into the aryl skeleton is preferably within the range of -0.2 to 0.2, and more preferably within the range of -0.09 to 0.09. By being within this range, the HOMO potential can be adjusted to a desired range, and an excellent balance between the film stability and printing durability of the image recording layer is achieved. In the present disclosure, the sum of the Hammett σ values ​​of the substituents introduced into the aryl skeleton was calculated using the values ​​described in the reference "Chemical Seminar 10: Hammett Side - Structure and Reactivity -" (by Naoki Inamoto, Maruzen Co., Ltd., published in June 1983).

[0134] M in formula (1) ＋ represents a cation. ＋ is a counter cation of the boron anion. ＋ is not particularly limited as long as it is a cation that can neutralize the boron anion, but from the viewpoint of suppressing staining during development, it is preferably at least one selected from the group consisting of inorganic cations, iodonium cations, and infrared absorbing dye cations. One counter cation may be used alone, or two or more counter cations may be used in combination. In formula (I), M ＋ Li ＋ , Na ＋ , K. ＋ , an iodonium cation, or an infrared absorbing dye cation. ＋ represents an iodonium cation or an infrared absorbing dye cation.

[0135] When two or more counter cations are used, the combination is not particularly limited, but is preferably a combination of inorganic cations, a combination of iodonium cations, or a combination of infrared absorbing dye cations, and more preferably a combination of iodonium cations or a combination of infrared absorbing dye cations, which further improves the ability to suppress development defects over time and printing durability.

[0136] The iodonium cation may be the cation moiety of an electron-accepting polymerization initiator described later, and the infrared absorbing dye cation may be the cation moiety of an infrared absorber described later. In the image recording layer, the cation moiety of the electron-donating polymerization initiator and the cation moiety of the infrared absorber can bond with the anion moiety of the borate compound represented by formula (1) to form a salt.

[0137] Examples of inorganic cations include lithium cations, sodium cations, potassium cations, calcium cations, and magnesium cations. Among these, sodium cations, lithium cations, and potassium cations are preferred, and sodium cations are more preferred.

[0138] The iodonium cation can be the cation moiety of an electron-accepting polymerization initiator described below. Specific examples are shown in the following structural formulas: In the following structural formulas, Me represents a methyl group. However, the iodonium cation is not limited to the following specific examples.

[0139]

[0140] The infrared absorbing dye cation can be the cation moiety of the infrared absorber described below. Specific examples are shown in the following structural formulas: In the following structural formulas, Me represents a methyl group, and Bu represents a butyl group. Note that the infrared absorbing dye cation is not limited to the following specific examples.

[0141]

[0142]

[0143] From the viewpoints of chemical resistance and printing durability, the highest occupied molecular orbital (HOMO) of the specific borate compound is preferably −6.0 eV or higher, more preferably −5.95 eV or higher, and even more preferably −5.93 eV or higher. The upper limit is preferably −5.00 eV or lower, more preferably −5.40 eV or lower. A range of −5.93 eV to −5.70 eV is particularly preferred.

[0144] In the present disclosure, calculations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are performed using the following method. First, the counter anion in the compound to be calculated is ignored. Quantum chemistry calculation software Gaussian09 is used, and structural optimization is performed using DFT (B3LYP / 6-31G(d)). MO (molecular orbital) energy calculations are performed using DFT (B3LYP / 6-31+G(d,p) / CPCM (solvent=methanol)) with the structure obtained by the structural optimization. The MO energy Ebare (unit: hearttree) obtained in the above MO energy calculation is converted to Escaled (unit: eV), which is used as the HOMO and LUMO values ​​in the present disclosure, using the following formula: Escaled = 0.823168 x 27.2114 x Ebare - 1.07634 Note that 27.2114 is simply a coefficient for converting heartle to eV, and 0.823168 and -1.07634 are adjustment coefficients that are determined so that the HOMO and LUMO of the compound to be calculated match the measured values.

[0145] Preferred specific examples of the specific borate compound are shown below, but the compound is not limited to these. In the following structural formula, Me represents a methyl group.

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] Another embodiment of the borate compound is a borate compound represented by the following formula (1a): The borate compound represented by formula (1a) is one embodiment of the borate compound represented by formula (1), and is used as an electron-donating polymerization initiator in the image recording layer.

[0153]

[0154] In formula (1a), R １ , R ２ , R ３ and R ４ each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group; R １ , R ２ , R ３ and R ４ may each independently have a ring structure. １ , R ２ , R ３ and R ４ At least one of them is different from the others. ＋ represents an iodonium cation.

[0155] In formula (1a), R １ , R ２ , R ３ and R ４ is R in the above formula (1). １ , R ２ , R ３ and R ４ The same applies to the preferred embodiments.

[0156] In formula (1a), Ma ＋ represents an iodonium cation. That is, the iodonium cation is a counter cation of the boron anion. In the present disclosure, the iodonium cation is not particularly limited as long as it is a cation that can neutralize the boron anion. Only one type of iodonium cation may be contained, or two or more types may be contained.

[0157] Examples of iodonium cations include those represented by the structural formulas described in the section on specific borate compounds.

[0158] The highest occupied molecular orbital (HOMO) of the borate compound represented by formula (1a) is similar to the preferred embodiment of the borate compound represented by formula (1). The calculation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is also similar to the above method.

[0159] Preferred specific examples of the borate compound represented by formula (1a) include the above-mentioned B-18, B-19, B-31 to B-33, B-45, and B-46, but are not limited thereto.

[0160] The image recording layer may contain only one type of specific borate compound, or may contain two or more types. From the viewpoints of color development, color development over time after exposure, developability, and suppression of development defects over time in the resulting lithographic printing plate, the content of the specific borate compound 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, in terms of the weight of the anion moiety of the specific borate compound, relative to the total mass of the image recording layer.

[0161] A preferred example of the image recording layer containing an electron-donating polymerization initiator is a salt formed by an onium salt and an electron-donating polymerization initiator.The salt formed by an onium salt and an electron-donating polymerization initiator can be, for example, an iodonium borate compound formed by an iodonium compound, which is an onium salt, and a borate compound.Specific examples of the iodonium borate compound include the compounds described in WO 2020 / 262692.

[0162] The content of the electron-donating polymerization initiator (preferably a borate compound) is preferably from 0.01 to 30% by mass, more preferably from 0.05 to 25% by mass, and even more preferably from 0.1 to 20% by mass, based on the total mass of the image recording layer.

[0163] The content of the polymerization initiator containing an onium salt (the total content of the onium salt, other electron-accepting polymerization initiator, and electron-donating polymerization initiator) is preferably from 0.1 to 50% by mass, more preferably from 0.5 to 30% by mass, and even more preferably from 0.8 to 20% by mass, based on the total mass of the image recording layer.

[0164] The content of the polymerization initiator (total content of the onium salt, other electron-accepting polymerization initiator, and electron-donating polymerization initiator) is preferably 0.5 molar equivalents or more, more preferably 1.0 molar equivalents or more, and even more preferably 3.0 molar equivalents or more relative to the content of the acid color former, in terms of better visibility. There is no particular upper limit, but it is preferably 10.0 molar equivalents or less relative to the content of the acid color former.

[0165] <Polymerizable Compound> The image recording layer preferably contains a polymerizable compound. In this specification, the polymerizable compound refers to a compound having a polymerizable group. The polymerizable group is not particularly limited and may be a radically polymerizable group or a cationically polymerizable group, but a radically polymerizable group is preferred. Examples of the radically polymerizable group include groups having an ethylenically unsaturated group such as 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.

[0166] 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 may have a chemical form such as a monomer, a prepolymer, i.e., a dimer, trimer, or oligomer, or a mixture thereof. 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 polymerizable compound, more preferably a decafunctional or higher functional (meth)acrylate compound).

[0167] From the viewpoints of on-press developability and suppression of color development failure over time, the image recording layer preferably contains a difunctional or lower polymerizable compound, more preferably a difunctional polymerizable compound, and even more preferably a difunctional (meth)acrylate compound. From the viewpoints of printing durability, on-press developability, and suppression of color development failure over time, the content of the difunctional or lower polymerizable compound (preferably a bifunctional polymerizable compound) is preferably 5 to 100% by mass, more preferably 10 to 100% by mass, and even more preferably 15 to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0168] (Oligomer) The polymerizable compound contained in the image recording layer is preferably a polymerizable compound that is an oligomer. In this specification, oligomer refers to a polymerizable compound having a molecular weight (weight average molecular weight when the molecular weight distribution is present) of 600 to 40,000 and containing at least one polymerizable group. Hereinafter, a polymerizable compound that is an oligomer contained in the image recording layer will also be simply referred to as "oligomer." From the viewpoint of excellent chemical resistance and printing durability, the molecular weight of the oligomer is preferably 1,000 to 25,000.

[0169] 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. 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.

[0170] From the viewpoints of printing durability and on-press developability, the oligomer is preferably a polymerizable compound having 7 or more polymerizable groups and a molecular weight of 1,000 to 40,000, and more preferably a polymerizable compound having 7 or more to 20 polymerizable groups and a molecular weight of 1,000 to 25,000. The image recording layer may contain a polymer component that may be generated in the process of producing the oligomer.

[0171] 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 this specification, 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.

[0172] As a compound having a urethane bond, the compounds described in WO 2020 / 262692 can be suitably used. As a compound having a urethane bond, a compound in which a polymerizable group is introduced by a polymer reaction into a polyurethane obtained by reacting a polyisocyanate compound with a polyol compound may be used. For example, a compound having a urethane bond may be obtained by reacting a polyurethane oligomer obtained by reacting a polyol compound having an acid group with a polyisocyanate compound with a compound having an epoxy group and a polymerizable group.

[0173] The number of polymerizable groups in the compound having an ester bond, which is an example of the oligomer, is preferably 3 or more, more preferably 6 or more. The upper limit is preferably 20 or less.

[0174] 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, more preferably 2 or 3. The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

[0175] As the oligomer, commercially available products may be used, and examples thereof include UA510H, UA-306H, UA-306I, UA-306T (all manufactured by Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, UV7620EA (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), U-15HA (manufactured by Shin-Nakamura Chemical Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, EBECRYL860 (all manufactured by Daicel Allnex Corporation), but are not limited thereto.

[0176] From the viewpoint of improving chemical resistance, printing durability, and suppression of on-press development residue, the content of the oligomer is preferably 30 to 100 mass %, more preferably 50 to 100 mass %, and even more preferably 80 to 100 mass %, relative to the total mass of the polymerizable compounds in the image recording layer.

[0177] (Low Molecular Weight Polymerizable Compound) The polymerizable compound may further contain a polymerizable compound other than the oligomer. As the polymerizable compound other than the oligomer, a low molecular weight polymerizable compound is preferred from the viewpoint of chemical resistance. The low molecular weight polymerizable compound may be in a chemical form such as a monomer, a dimer, a trimer, or a mixture thereof. As the low molecular weight polymerizable compound, from the viewpoint of chemical resistance, 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 is preferred.

[0178] In this specification, the term "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.

[0179] 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.

[0180] 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.

[0181] The details of the method of use, such as the structure of the polymerizable compound, whether to use it 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 polymerizable compounds. The content of the polymerizable compounds (when two or more polymerizable compounds are contained, the total content of the polymerizable compounds) is preferably 5 to 75% by mass, more preferably 10 to 70% by mass, and even more preferably 15 to 60% by mass, based on the total mass of the image recording layer.

[0182] <Particles> From the viewpoint of printing durability, the image recording layer preferably contains particles. The particles may be either organic particles or inorganic particles, but from the viewpoint of printing durability, organic particles are preferred, and polymer particles are more preferred. Organic particles refer to particles made of an organic substance, and polymer particles refer to particles made of a polymer. In other words, polymer particles refer to polymers that have a particle shape among the polymers contained in the image recording layer.

[0183] The polymer particles are preferably particles selected from the group consisting of thermoplastic resin particles, thermoreactive resin particles, polymer particles having polymerizable groups, microcapsules encapsulating hydrophobic compounds, and microgels (crosslinked polymer particles). Among these, polymer particles or microgels having polymerizable groups are preferred. The polymer particles preferably contain at least one ethylenically unsaturated group, as this provides the effect of improving the printing durability of exposed areas and the on-press developability of unexposed areas. From the viewpoint of printing durability and on-press developability, thermoplastic resin particles are preferred as polymer particles. Specific examples of the polymer particles that may be contained in the image recording layer include the polymer particles described in International Publication No. 2020 / 262692, the disclosure of which is incorporated herein by reference.

[0184] As the inorganic particles, known inorganic particles can be used, and metal oxide particles such as silica particles and titania particles can be suitably used.

[0185] The average particle size of the particles is preferably 0.01 to 3.0 μm, more preferably 0.03 to 2.0 μm, and even more preferably 0.10 to 1.0 μm. Within this range, good resolution and stability over time can be obtained. The average particle size of the particles is measured by dynamic light scattering, similar to the average particle size of the thermoplastic resin particles. Instead of measuring by dynamic light scattering, electron microscope photographs of the particles may be taken, and the particle sizes of a total of 5,000 particles may be measured on the photograph, and the arithmetic average value may be calculated to determine the average particle size of the particles. For non-spherical particles, the average particle size is the diameter of a circle having the same area as the particle area on the photograph. Unless otherwise specified, the average particle size of the particles is the volume average particle size.

[0186] The image recording layer may contain one type of particle (preferably polymer particles) alone or two or more types. From the viewpoints of on-press developability and printing durability, the content of the particles (preferably polymer particles) in the image recording layer is preferably 5 to 90% by mass, more preferably 10 to 90% by mass, even more preferably 20 to 90% by mass, and particularly preferably 50 to 90% by mass, based on the total mass of the image recording layer.

[0187] <Binder Polymer> The image recording layer may contain a binder polymer. The polymer particles do not fall under the category of the binder polymer. That is, the binder polymer is a polymer that is not in a particle form. The binder polymer is preferably a (meth)acrylic resin, a polyvinyl acetal resin, or a polyurethane resin.

[0188] As the binder polymer, known binder polymers used in the image recording layer of a lithographic printing plate precursor can be used, and binder polymers used in on-press development-type lithographic printing plate precursors (also referred to as on-press development binder polymers) can be preferably used. As the on-press development binder polymer, binder polymers having an alkylene oxide chain are preferred. Other preferred examples of binder polymers include star-shaped polymer compounds, binder polymers having structural units formed by aromatic vinyl compounds, polyvinyl acetals, and resins having fluorine atoms (more preferably fluoroaliphatic group-containing copolymers). The star-shaped polymer compound is a polymer compound having a hexa- to 10-functional polyfunctional thiol core, a polymer chain bonded to this core by a sulfide bond, and the polymer chain having a polymerizable group. Specific examples of the binder polymer that may be contained in the image recording layer include the polymers described in JP 2012-148555 A and WO 2020 / 262692, the descriptions of which are incorporated herein by reference.

[0189] The binder polymer may be used alone or in combination of two or more. The binder polymer may be contained in any amount in the image recording layer. When the image recording layer contains a binder polymer, the content of the binder polymer is preferably 1 to 90% by mass, more preferably 5 to 80% by mass, based on the total mass of the image recording layer.

[0190] <Polymerization inhibitor> The image recording layer preferably contains a polymerization inhibitor in order to improve stability over time and developability after aging. By containing a polymerization inhibitor in the image recording layer, unnecessary thermal polymerization of polymerizable compounds, particularly radically polymerizable compounds, can be prevented during production or storage of the image recording layer. Examples of the polymerization inhibitor include the polymerization inhibitors described in WO 2023 / 030714, and the descriptions thereof are incorporated herein.

[0191] The content of the polymerization inhibitor is preferably from 0.001 to 5% by mass, more preferably from 0.01 to 1% by mass, based on the total mass of the image recording layer.

[0192] <Chain Transfer Agent> The image recording layer may contain a chain transfer agent. The chain transfer agent contributes to improving the printing durability of the lithographic printing plate. As the chain transfer agent, a thiol compound is preferred, and from the viewpoint of boiling point (difficulty of volatilization), a thiol compound having 7 or more carbon atoms is more preferred, and a compound having 7 or more carbon atoms and a mercapto group on an aromatic ring (aromatic thiol compound) is even more preferred. As the thiol compound, a monofunctional thiol compound is preferred. Specific examples of the chain transfer agent include the compounds described in WO 2020 / 262692.

[0193] The chain transfer agent may be used alone or in combination of two or more. The content of the chain transfer agent is preferably from 0.01 to 50% by mass, more preferably from 0.05 to 40% by mass, and even more preferably from 0.1 to 30% by mass, based on the total mass of the image recording layer.

[0194] <Hydrogen donor compound>

[0195] -OH, -NH-, -SO ２ -NH-, -SO ２ A group selected from the group consisting of —OH, —CO—NH—, and —CO—OH (hereinafter, also simply referred to as a “hydrogen-donating group”) is a group capable of donating a hydrogen atom. The hydrogen-donating compound is a compound different from the polymerization initiator, the polymerizable compound, the infrared absorber, and the acid-cleavable compound, and is a group selected from the group consisting of —OH, —NH—, —SO ２ -NH-, -SO ２It is a compound having at least one group selected from the group consisting of -OH, -CO-NH-, and -CO-OH in the molecule, and having a molecular weight of less than 3,000. "-OH" represents a hydroxyl group, which is different from "-CO-OH" (a carboxyl group), and -SO ２ - is a non-bonding group. "-NH-" is -SO ２ - and -CO- are groups that do not bond.

[0196] The term "compounds different from polymerization initiators, polymerizable compounds, infrared absorbers, and acid-cleavable compounds" means that even if a compound has the above-mentioned hydrogen-donating group and has a molecular weight of less than 3,000, it is not included in the hydrogen-donating compound as long as it is any one of a compound that functions as a polymerization initiator, a compound that functions as a polymerizable compound, a compound that functions as an infrared absorber, and an acid-cleavable compound. The polymerization initiator, polymerizable compound, and infrared absorber are each as described above.

[0197] The acid-cleavable compound refers to a compound that is cleaved by the action of an acid, specifically, a ring in the molecule is cleaved (opened) by the action of an acid. So-called acid color formers that develop color upon cleavage by the action of an acid are included in the acid-cleavable compound. The hydrogen-donor compound is a compound that is different from an acid color former.

[0198] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the following formula (I) in the molecule:

[0199]

[0200] In formula (I), X is —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. １Ａ ~R ３Ａ R are each independently a group having at least one atom selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. １Ａ ~R ３Ａ At least two of the groups may be linked to form a ring. When X is a monovalent group, R １Ａ ~R ３ＡWhen X is a divalent group, one or more hydrogen atoms contained in R １Ａ ~R ３Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0201] The hydrogen donating group for X is preferably —OH, —NH—, or —SO 3 from the viewpoints of preventing fading when exposed to white light and of compatibility with the image recording layer. ２ -NH- or -CO-NH- is preferred, and -OH or -SO ２ —NH— is more preferred.

[0202] R １Ａ ~R ３Ａ The group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom (hereinafter also referred to as "substituent A") is not particularly limited, but is preferably a group having 0 to 30 carbon atoms. The halogen atom is not particularly limited, but examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The heteroatom is not particularly limited, but examples thereof include a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. The substituent A is not particularly limited, but is preferably a hydrogen atom or a hydrocarbon group. The hydrocarbon group may have a heteroatom or a halogen atom.

[0203] R １Ａ ~R ３Ａ At least two of the above may be linked to form a ring. The ring formed may be a monocyclic ring or a polycyclic ring. Examples of the ring formed include an aromatic ring and an aliphatic hydrocarbon ring, and the number of ring atoms of the ring formed is preferably 6 to 14. When X is a monovalent group (specifically, -OH, -SO ２ -OH and -CO-OH) is R １Ａ ~R ３Ａ When X is a divalent group (specifically, -NH-, -SO ２ -NH- and -CO-NH-) can constitute a partial structure in formula (I), but R １Ａ ~R ３ＡOne or more hydrogen atoms contained in may be further removed to form bonds.

[0204] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the above formula (I) in the molecule, and may be a compound having at least two or more partial structures represented by the above formula (I) in the molecule. The number of partial structures represented by the above formula (I) in the molecule is not particularly limited, but is preferably 1 to 10, and more preferably 1 to 5.

[0205] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the following formula (II) in the molecule:

[0206]

[0207] In formula (II), Ar represents an aromatic ring group, and X represents —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. ４Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. m represents an integer of 1 to 5. When m represents an integer of 2 or more, multiple Xs may be the same or different. n represents an integer of 0 to 5. When n represents an integer of 2 or more, multiple R ４Ａ may be the same or different. When n is 2 or more, a plurality of R ４Ａ may be linked to form a ring. When all Xs are monovalent groups, R ４Ａ When at least one X is a divalent group, R ４Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0208] X has the same meaning as X in formula (I), and the preferred range is also the same. Examples of the aromatic ring in the aromatic ring group of Ar include an aromatic hydrocarbon ring and an aromatic heterocycle. The aromatic hydrocarbon ring may be a monocycle or a polycycle. The number of ring atoms is preferably 6 to 15, and more preferably 6 to 10. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring. Of these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred.

[0209] The aromatic heterocycle may be a monocycle or a polycycle. The number of ring atoms is preferably 5 to 15. Examples of the heterocycle having aromaticity include a furan ring, a thiophene ring, a benzofuran ring, a benzothiophene ring, a dibenzofuran ring, a dibenzothiophene ring, a pyridine ring, an indole ring, a benzodiazole ring, and a carbazole ring.

[0210] R ４Ａ The group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom (hereinafter also referred to as "substituent A1") as the substituent A1 is not particularly limited, but is preferably a group having 0 to 24 carbon atoms. Examples of halogen atoms include, but are not particularly limited to, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of heteroatoms include, but are not particularly limited to, a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. Examples of substituent A1 include, but are not particularly limited to, a hydrogen atom or a hydrocarbon group. The hydrocarbon group may have a heteroatom or a halogen atom.

[0211] m represents an integer of 1 to 5. m preferably represents an integer of 1 to 3, and more preferably represents an integer of 1 or 2. n represents an integer of 0 to 5. n preferably represents an integer of 0 to 2, and more preferably represents an integer of 0 or 1.

[0212] When n is 2 or more, multiple R ４Ａ may be linked to form a ring. ４ＡHowever, the ring formed by linking may be a monocyclic ring or a polycyclic ring. Examples of the ring formed include an aromatic ring and an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0213] When X is a monovalent group (specifically, —OH, —SO ２ -OH and -CO-OH) is R ４Ａ When X is a divalent group (specifically, -NH-, -SO ２ -NH- and -CO-NH-) can constitute a partial structure in formula (I), but R ４Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0214] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the above formula (II) in the molecule, and may be a compound having at least two or more partial structures represented by the above formula (II) in the molecule. The number of partial structures represented by the above formula (I) in the molecule is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.

[0215] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the following formula (III) in the molecule.

[0216]

[0217] In formula (III), X is —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. ５Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. p represents an integer of 1 to 5. When p represents an integer of 2 or more, multiple Xs may be the same or different. q represents an integer of 0 to 5. When q represents an integer of 2 or more, multiple R ５may be the same or different. When q is 2 or more, a plurality of R ５Ａ may be linked to form a ring. p+q is 6 or less. When all Xs are monovalent groups, R ５Ａ When at least one X is a divalent group, R ５Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0218] X has the same meaning as X in formula (I), and the preferred range is also the same. ５Ａ The group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom (hereinafter also referred to as "substituent A2") as the substituent A2 is not particularly limited, but is preferably a group having 0 to 24 carbon atoms. Examples of halogen atoms include, but are not particularly limited to, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of heteroatoms include, but are not particularly limited to, a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. Examples of substituent A2 include, but are not particularly limited to, a hydrogen atom or a hydrocarbon group. The hydrocarbon group may have a heteroatom or a halogen atom.

[0219] p represents an integer of 1 to 5. p preferably represents an integer of 1 to 3, and more preferably represents an integer of 1 or 2. q represents an integer of 0 to 5. q preferably represents an integer of 0 to 2, and more preferably represents an integer of 0 or 1.

[0220] When q is 2 or more, a plurality of R ５Ａ may be linked to form a ring. ５Ａ However, the ring formed by linking may be a monocyclic ring or a polycyclic ring. Examples of the ring formed include an aromatic ring and an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0221] The hydrogen donating group in the hydrogen donating compound is preferably —OH, —NH—, or —SO 3 from the viewpoints of preventing fading when exposed to white light and being easily compatible with the image recording layer. ２A group selected from the group consisting of —NH— and —CO—NH— is preferred, and —OH and —SO ２ A group selected from the group consisting of -NH- is more preferred. From the viewpoint of suppressing fading upon exposure to white light, the hydrogen donor compound preferably contains at least one of the above-mentioned hydrogen donor groups, more preferably contains at least two, and even more preferably contains at least three. The number of hydrogen donor groups contained in the hydrogen donor compound is not particularly limited, but is, for example, preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less.

[0222] In a preferred embodiment, the hydrogen donor compound is —OH, —NH—, or —SO ２ -NH-, -SO ２ It is preferable that the hydrogen donor compound is a compound having at least two groups selected from the group consisting of —OH, —CO—NH—, and —CO—OH in the molecule. In a preferred embodiment, the hydrogen donor compound is a compound having at least two groups selected from the group consisting of —OH and —SO ２ In a preferred embodiment, the hydrogen donor compound has at least one group selected from the group consisting of —OH and —SO ２ It is preferred that the alkyl group has at least two groups selected from the group consisting of —NH—.

[0223] The hydrogen donor compound preferably has at least one phenolic hydroxyl group. The phenolic hydroxyl group represents a hydroxyl group (—OH) directly bonded to an aromatic ring (specifically, a benzene ring). The hydrogen donor compound preferably has two or more phenolic hydroxyl groups. The hydrogen donor compound preferably has two to six phenolic hydroxyl groups, and more preferably has two to four phenolic hydroxyl groups. The phrase “having two or more phenolic hydroxyl groups” means that an aromatic ring bonded to one phenolic hydroxyl group may further have one or more phenolic hydroxyl groups bonded thereto, or an aromatic ring different from the aromatic ring bonded to one phenolic hydroxyl group may further have one or more phenolic hydroxyl groups bonded thereto.

[0224] The hydrogen donor compound is preferably a compound represented by the following formula (IV) or a compound represented by the following formula (V).

[0225]

[0226] In formula (IV), X Ａ represents —OH. ６Ａ represents an organic group or a halogen atom. r represents an integer of 1 to 5. s represents an integer of 0 to 5. When s represents an integer of 2 or more, a plurality of R ６Ａ may be the same or different. When s is 2 or more, a plurality of R ６Ａ may be linked to form a ring. In formula (V), L represents a single bond or a divalent linking group. X Ｂ represents —OH. ７Ａ represents an organic group or a halogen atom. ｃ represents —OH. ８Ａ represents an organic group or a halogen atom; t represents an integer of 1 to 5; u represents an integer of 0 to 5. When u represents an integer of 2 or more, a plurality of R ７Ａ may be the same or different. When u is 2 or more, a plurality of R ７Ａ may be linked to form a ring. v represents an integer of 1 to 5. w represents an integer of 0 to 5. When w represents an integer of 2 or more, a plurality of R ８Ａ may be the same or different. When w is 2 or more, a plurality of R ８Ａ may be linked to form a ring.

[0227] R ６Ａ , R ７Ａ , R ８Ａ The organic group in R is not particularly limited, but examples thereof include alkyl groups and aryl groups. The alkyl group may be linear or branched, and examples thereof include alkyl groups having 1 to 10 carbon atoms. The aryl group may be monocyclic or polycyclic, and examples thereof include aryl groups having 6 to 20 carbon atoms. ６Ａ , R ７Ａ , R ８Ａ The halogen atom is not particularly limited, but includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0228] r represents an integer of 1 to 5. r preferably represents an integer of 1 to 3, more preferably 1 or 2. s represents an integer of 0 to 5. s preferably represents an integer of 0 to 3, more preferably 0 or 1. r+s is preferably 6 or less. Multiple R ６Ａ However, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0229] The divalent linking group of L is not particularly limited, and examples thereof include an alkylene group, —CO—, and —SO ２ -, -O-, or a combination thereof. Examples of the alkylene group include linear or branched alkylene groups having 1 to 5 carbon atoms. The alkylene group may further have a substituent. The substituent is not particularly limited, but examples include aryl groups (preferably having 6 to 10 carbon atoms). The aryl group may further have a substituent, and examples of the further substituent include a hydroxyl group.

[0230] t represents an integer of 1 to 5. t preferably represents an integer of 1 to 3, more preferably 1 or 2. u represents an integer of 0 to 5. u preferably represents an integer of 0 to 3, more preferably 0 or 1. t+u is preferably 6 or less. ７Ａ However, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0231] v represents an integer of 1 to 5. v preferably represents an integer of 1 to 3, more preferably 1 or 2. w represents an integer of 0 to 5. w preferably represents an integer of 0 to 3, more preferably 0 or 1. v+w is preferably 6 or less. ８ＡHowever, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0232] The hydrogen donor compound is a low molecular weight compound having a molecular weight of less than 3,000, preferably a low molecular weight compound of 1,500 or less, and more preferably a low molecular weight compound of 1,000 or less. Here, with regard to the hydrogen donor compound, the low molecular weight compound is not a so-called polymer or oligomer obtained by cleaving the unsaturated bond of a compound having an unsaturated bond (a so-called polymerizable monomer) using an initiator and growing the bond in a chain reaction, but a compound having a constant molecular weight of 3,000 or less (more preferably 2,000 or less, and even more preferably 1,000 or less) (a compound having substantially no molecular weight distribution).

[0233] The molecular weight of the hydrogen donor compound is not particularly limited, but is preferably at least 50, more preferably at least 100, and more preferably at least 200. In a preferred embodiment, from the viewpoints of on-press developability and printing durability, the molecular weight of the hydrogen donor compound is preferably from 50 to 3,000, more preferably from 100 to 1,500, and even more preferably from 200 to 1,000.

[0234] Specific examples of the hydrogen donor compound are shown below, but the hydrogen donor compound is not limited to these.

[0235]

[0236]

[0237]

[0238] The hydrogen donor compound may be used alone or in combination of two or more. The content of the hydrogen donor compound is preferably from 0.5 to 30% by mass, more preferably from 1 to 20% by mass, and even more preferably from 1 to 10% by mass, of the total solid content of the image recording layer.

[0239] <Other Components> The image recording layer may contain other components besides those described above, such as an oil-sensitizing agent (e.g., a phosphonium compound, a nitrogen-containing low molecular weight compound, an ammonium group-containing polymer), a development accelerator, a surfactant, a higher fatty acid derivative, a plasticizer, and an inorganic layer compound. For details of these other components, see paragraphs 0114 to 0159 of JP-A-2008-284817. Specific examples of development accelerators include the compounds described in WO 2020 / 262692.

[0240] <Method of Forming Image Recording Layer> The image recording layer can be formed by dispersing or dissolving the above components 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, for example, in paragraphs

[0142] and

[0143] of JP-A No. 2008-195018. Known solvents can be used. Specific examples of solvents include those described in paragraph

[0142] of JP-A No. 2008-195018. The solvents may be used alone or in combination of two or more. The solid content concentration in the coating liquid is preferably 1 to 50% by mass. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but is preferably 0.3 to 3.0 g / m from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer. ２ is preferred.

[0241] The thickness of the image recording layer is preferably 0.1 to 3.0 μm, more preferably 0.3 to 2.0 μm. The thickness of each layer in the lithographic printing plate precursor can be measured by preparing a slice by cutting the lithographic printing plate precursor in a direction perpendicular to the surface thereof and observing the cross section of the slice with a scanning electron microscope (SEM).

[0242] [Other Layers] The lithographic printing plate precursor may include layers other than the support and image recording layer described above. For example, the lithographic printing plate precursor may have an undercoat layer disposed between the support and the image recording layer, if necessary, to improve adhesion between the support and the image recording layer. Furthermore, the lithographic printing plate precursor may have a protective layer (overcoat layer) on the image recording layer, if necessary, to prevent scratches on the image recording layer, block oxygen, and prevent ablation during exposure to high-intensity laser light.

[0243] <Undercoat layer> The lithographic printing plate precursor preferably has an undercoat layer. By having the lithographic printing plate precursor have an undercoat layer, for example, in the case of a negative-type image recording layer, the adhesion between the support and the image recording layer is strengthened in the exposed areas, and the image recording layer is more likely to peel from the support in the unexposed areas, thereby improving developability while suppressing a decrease in printing durability. Furthermore, 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.

[0244] The components constituting the undercoat layer are not particularly limited, but in terms of superior printing durability, it is preferable to include a polymer having a support-adsorbing group and a hydrophilic group (hereinafter also referred to as "polymer I"). The support-adsorbing group refers to a group that interacts with the support, allowing a compound having the support-adsorbing group to remain on the support even during development processing on a printing press. Examples of the support-adsorbing group include an oxo acid structure of a phosphorus atom, an oxo acid salt structure of a phosphorus atom, an oxo acid ester structure of a phosphorus atom, and an oxo acid ester salt structure of a phosphorus atom. A group selected from the group consisting of a phosphonic acid group, a phosphate ester group, and salts thereof is preferred, and a phosphate ester group or a salt thereof is more preferred.

[0245] Examples of hydrophilic groups include groups having a zwitterionic structure (betaine structure), groups having a polyalkyleneoxy structure, sulfonic acid groups and their salts, and carboxylic acid groups and their salts. Among these, groups having a zwitterionic structure or groups having a polyalkyleneoxy structure are preferred, and groups having a zwitterionic structure are more preferred, in that they suppress ink residue on the support and provide superior printing stain suppression performance. Here, a zwitterionic structure refers to a structure having at least one cation and at least one anion. Typically, the number of cations and the number of anions are equal, resulting in overall neutrality. However, in this specification, a zwitterionic structure also refers to a structure having a necessary amount of counter ions to cancel out the charge when the number of cations and the number of anions are not equal.

[0246] Polymer I is preferably a copolymer having a repeating unit A having a group selected from the group consisting of a phosphonic acid group, a phosphate ester group, and salts thereof in its side chain, and a repeating unit B having at least one of a zwitterionic structure and a polyalkyleneoxy structure in its side chain. This embodiment provides superior printing durability and print stain suppression performance. In this specification, the term "main chain" refers to the relatively longest linking chain in the molecules of the polymer compound that constitutes the resin, and the term "side chain" refers to a linking chain branching from the main chain.

[0247] From the viewpoints of printing durability, resistance to soiling after storage, and developability, the content of repeating unit A in polymer I is preferably 1 to 40% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass, relative to the total mass of polymer I. From the viewpoints of resistance to soiling after storage and developability, the content of repeating unit B in polymer I is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 85% by mass, relative to the total mass of polymer I.

[0248] It is preferable that polymer I further has a polymerizable group. That is, polymer I is preferably a polymer having a support-adsorbing group, a hydrophilic group, and a polymerizable group. It is more preferable that polymer I further has an ethylenically unsaturated group as the polymerizable group, and even more preferable that polymer I has a repeating unit having an ethylenically unsaturated group in a side chain (also referred to as "repeating unit C"). When polymer I contains repeating unit C, the content of repeating unit C is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, relative to the total mass of the polymer, from the viewpoints of printing durability and resistance to soiling after storage.

[0249] Polymer I is preferably an acrylic resin obtained by polymerizing a (meth)acrylate compound and / or a (meth)acrylamide compound. From the viewpoints of resistance to soiling after leaving and developability, the total content of repeating units A and B in Polymer I is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, and even more preferably 80 to 95% by mass, based on the total mass of the polymer.

[0250] The weight-average molecular weight (Mw) of polymer I can be set arbitrarily depending on the performance design of the lithographic printing plate precursor. From the viewpoint of achieving better printing durability and better suppression of printing stains, the weight-average molecular weight of polymer I is preferably from 2,000 to 1,000,000, more preferably from 4,000 to 500,000, and even more preferably from 5,000 to 400,000.

[0251] Polymer I can also be synthesized by known methods. Preferred methods for synthesizing Polymer I include radical polymerization, followed by a urea reaction in which an amino group in a polymer side chain is reacted with an isocyanate compound having a radical polymerization reactive group, or an amidation reaction in which an amino group in a polymer side chain is reacted with an acid anhydride having a radical polymerization reactive group. Examples of radical polymerization methods that can be used include those described in New Polymer Experiments 3 (edited by the Society of Polymer Science, Kyoritsu Shuppan, published March 28, 1996), Polymer Synthesis and Reactions 1 (edited by the Society of Polymer Science, Kyoritsu Shuppan, published May 1992), New Experimental Chemistry Lectures 19, Polymer Chemistry (I) (edited by the Chemical Society of Japan, Maruzen, published November 20, 1980), and Materials Engineering Lectures: Polymer Synthetic Chemistry (Tokyo Denki University Press, published September 1995).

[0252] The polymer I contained in the undercoat layer may be used alone or in combination of two or more. The content of the polymer I in the undercoat layer is preferably 50 to 100 mass %, more preferably 60 to 100 mass %, and still more preferably 70 to 100 mass %, based on the total mass of all solids in the undercoat layer excluding volatile components.

[0253] (Method of Forming Undercoat Layer) The method of forming the undercoat layer is not particularly limited, and examples thereof include a method of applying an undercoat layer-forming coating liquid containing components constituting the undercoat layer, such as polymer I, onto the anodized film of the support. The undercoat layer-forming coating liquid preferably contains a solvent. Examples of the solvent include water, organic solvents such as alcohol compounds, and mixed solvents thereof. Examples of the method of applying the undercoat layer-forming coating liquid include various known methods. Examples include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating. The coating amount (solid content) of the undercoat layer is 0.1 to 100 mg / m ２ is preferred, and 1 to 30 mg / m ２ is more preferred.

[0254] <Protective Layer> The lithographic printing plate precursor preferably has a protective layer (also referred to as an "overcoat layer") on the surface of the image recording layer opposite the support. That is, a lithographic printing plate precursor having a support, an image recording layer, and a protective layer in this order is preferred. The protective layer may have at least one of the following functions: a function of suppressing an image formation inhibiting reaction by blocking oxygen, a function of preventing scratches on the image recording layer, and a function of preventing ablation during exposure to a high-intensity laser.

[0255] Protective layers with such properties are described, for example, in U.S. Pat. No. 3,458,311 and Japanese Patent Publication No. 55-049729. The low-oxygen-permeable polymer used in the protective layer can be selected from either a water-soluble polymer or a hydrophobic polymer (water-insoluble polymer), and two or more types can be mixed and used as needed. However, from the viewpoint of on-press developability, a water-soluble polymer is preferred. In this specification, the term "water-soluble polymer" refers to a polymer having a solubility of more than 5% by mass in pure water at 25°C. When the protective layer contains a water-soluble polymer, the content of the water-soluble polymer relative to the total mass of the protective layer is preferably 1 to 99% by mass, more preferably 3 to 97% by mass, and even more preferably 5 to 95% by mass.

[0256] The protective layer preferably contains a hydrophobic polymer. The 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. The hydrophobic polymer may be used alone or in combination of two or more types. When the protective layer contains a hydrophobic polymer, the content of the hydrophobic polymer is preferably 1 to 70 mass %, more preferably 5 to 50 mass %, and even more preferably 10 to 40 mass %, based on the total mass of the protective layer.

[0257] The protective layer preferably contains a color former precursor from the viewpoint of improving the visibility of exposed areas. The color former precursor refers to a compound that develops color in response to stimuli such as light and acid, and has the property of changing the color of the image recording layer. Examples of the color former precursor include an infrared absorber and an acid color former. The protective layer preferably contains an infrared absorber as the color former precursor, and more preferably contains a decomposable infrared absorber. The infrared absorber and acid color former contained in the protective layer are the same as the infrared absorber and acid color former contained in the image recording layer, including their preferred forms.

[0258] The color former precursor contained in the protective layer may be used alone or in combination of two or more components. From the viewpoint of color development, the content of the color former precursor in the protective layer is preferably 0.10 to 50% by mass, more preferably 0.50 to 30% by mass, and even more preferably 1.0 to 20% by mass, relative to the total mass of the protective layer.

[0259] The protective 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 an inorganic layered compound, it is possible to effectively prevent redeposited matter from the roll surface from directly adhering to the surface of the image recording layer. Examples of inorganic layered compounds include the inorganic layered compounds described in WO 2020 / 262692, the disclosure of which is incorporated herein by reference. Examples of inorganic particles include metal oxide particles such as silica particles. The following inorganic layered compounds are not included in inorganic particles. Examples of organic resin particles include crosslinked resin particles.

[0260] The content of the filler (preferably an inorganic layered compound) is preferably 1 to 60% by mass, more preferably 3 to 50% by mass, based on the total mass of the protective layer. When the inorganic layered compound is contained in the above range, the oxygen barrier property is improved, good sensitivity is obtained, and a decrease in ink receptivity can be prevented.

[0261] In addition to the above components, the protective layer may contain known additives such as a plasticizer for imparting flexibility and a surfactant for improving coatability. The protective layer may also contain the oil-sensitizing agent described in the image-recording layer.

[0262] The protective layer can be formed by a known method of coating a composition containing the above components. The coating amount of the protective layer (in terms of solid content) is 0.0 to 10 g / m ２ is preferred, and 0.02 to 3 g / m ２ More preferably, 0.02 to 1 g / m ２ The thickness of the protective layer in the lithographic printing plate precursor is not particularly limited, but is preferably from 0.1 to 5.0 μm, more preferably from 0.3 to 4.0 μm.

[0263] The lithographic printing plate precursor may further have any known layer laminated on the lithographic printing plate precursor other than those described above. For example, a backcoat layer may be provided on the surface of the support opposite to the image recording layer, as needed.

[0264] [Laminate] The lithographic printing plate precursor may be configured as a laminate formed by stacking multiple lithographic printing plate precursors. A laminate formed by stacking multiple lithographic printing plate precursors preferably further comprises a protective material for protecting the lithographic printing plate precursors. Because a lithographic printing plate precursor is a single thin plate with a metal support, if it is bent, scratched, or deformed at the corners, sides, or inside, problems such as blurred images when exposed to light or uneven ink distribution when printed are likely to occur. Therefore, when configuring a laminate formed by stacking multiple precursors, it is preferable to place a protective material on each predetermined number of precursors to protect the precursors. For example, by packaging a laminate including multiple lithographic printing plate precursors and a protective material in a packaging material to form a package, and handling the package (transportation, storage, etc.), deformation (warping, etc.) of the precursors during handling is less likely to occur, thereby suppressing damage to the precursors. Furthermore, even if an external force acts on the package, a portion of the force is absorbed by the protective material, thereby suppressing deformation and damage to the precursors.

[0265] The location of the protective material in the laminate is not particularly limited, and examples thereof include the top of the laminate, between the laminated lithographic printing plate precursors, and the bottom of the laminate. The protective material is preferably located at least at the top of the laminate, and more preferably at both the top and bottom. The material of the protective material is not particularly limited, and examples thereof include cardboard, cardboard, and plastic. Among these, cardboard or plastic is preferred, and plastic is more preferred, from the viewpoint of preventing development defects. Examples of plastic include polyester, polycarbonate, and polyolefin, with polyester being preferred. The size (length and width) and thickness of the protective material are not particularly limited, and can be appropriately selected depending on the lithographic printing plate precursor to be protected. The moisture content of the protective material is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of preventing development defects. The lower limit of the moisture content is 0% by mass. The moisture content (equilibrium moisture content) of the protective material is measured in accordance with the method described in JIS P 8202 (1998).

[0266] The laminate may have an interleaf paper between the planographic printing plate precursors. Examples of the material for the interleaf paper include paper made from 100% wood pulp, paper made from a mixture of wood pulp and synthetic pulp, and paper having a low-density or high-density polyethylene layer provided on the surface thereof. The laminate may also be entirely packaged in a known packaging material.

[0267] [Uses of lithographic printing plate precursors] Lithographic printing plate precursors are used in the manufacture of lithographic printing plates and in printing using lithographic printing plates. In particular, lithographic printing plate precursors can be suitably used as on-press development type lithographic printing plate precursors that are developed by a method called on-press development. Here, on-press development refers to a development method in which, after exposure, the lithographic printing plate precursor is not subjected to conventional development, but is instead mounted on a printing press, and unnecessary portions of the image recording layer are removed at an early stage of the printing process. The lithographic printing plate precursor may also be used in the manufacture of lithographic printing plates that have a conventional development step of developing with a developer without being mounted on a printing press.

[0268] [Method for manufacturing a lithographic printing plate precursor] Examples of a method for manufacturing a lithographic printing plate precursor of the present invention include a method comprising the steps of: preparing a support comprising an aluminum plate and an anodized film; and forming an image recording layer on the surface of the prepared support that faces the anodized film. The step of preparing the support is described above in <Method for manufacturing a support>, and the step of forming the image recording layer is described above in <Method for forming an image recording layer>.

[0269] If necessary, after the step of preparing the support, a step of forming an undercoat layer on the surface of the obtained support facing the anodized film may be carried out, and then a step of forming the above-mentioned image recording layer on the surface of the formed undercoat layer may be carried out. Furthermore, after the step of forming the above-mentioned image recording layer, a step of forming a protective layer on the surface of the formed image recording layer may be carried out. The method of forming the undercoat layer and the step of forming the protective layer have been described above.

[0270] [Production method of lithographic printing plate, printing method] A method for producing a lithographic printing plate using the lithographic printing plate precursor of the present invention, and a printing method using the lithographic printing plate of the present invention will be described below. The production method of a lithographic printing plate of the present invention includes, for example, an exposure step in which a lithographic printing plate precursor is imagewise exposed (imagewise exposed) to form exposed areas and unexposed areas, and a removal step in which the unexposed areas of the imagewise exposed lithographic printing plate precursor are removed. A specific example of the production method of a lithographic printing plate includes a method including the above-mentioned exposure step and a developer treatment step in which the unexposed areas of the lithographic printing plate precursor are removed using a developer having a pH of 2 to 12. Another specific example of the production method of a lithographic printing plate includes a method including the above-mentioned exposure step and an on-press development step in which at least one of printing ink and fountain solution is supplied on a printing press to remove the unexposed areas of the image-wise exposed image-recording layer, thereby producing a lithographic printing plate.

[0271] The printing method of the present invention includes, for example, an exposure step of imagewise exposing a lithographic printing plate precursor to light (imagewise exposure) to form exposed and unexposed areas, a removal step of removing the unexposed areas of the imagewise exposed lithographic printing plate precursor to prepare a lithographic printing plate, and a printing step of carrying out printing using the prepared lithographic printing plate. A specific example of a method for producing a lithographic printing plate includes a method comprising the above-mentioned exposure step, the above-mentioned developer treatment step, and the above-mentioned printing step. Another specific example of a method for producing a lithographic printing plate includes a method comprising the above-mentioned exposure step, the above-mentioned on-press development step, and the above-mentioned printing step. Each of the above steps will be described in detail below.

[0272] <Exposure Step> The method for producing a lithographic printing plate and the printing method include an exposure step in which the image recording layer of the lithographic printing plate precursor is imagewise exposed to form exposed and unexposed areas. Imagewise exposure is carried out, for example, by laser exposure through a transparent original having a line image or a halftone dot image, or by laser light scanning using digital data. The wavelength of the light source for imagewise exposure is preferably 750 to 1400 nm. When using a light source that emits light with a wavelength of 750 to 1400 nm, it is preferable to use an image recording layer that contains an infrared absorber that absorbs in this wavelength range. Examples of light sources that emit light with a wavelength of 750 to 1400 nm include solid-state lasers and semiconductor lasers that emit infrared rays. With regard to infrared lasers, 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 to 300 mJ / cm. ２ is preferred. In addition, it is preferred to use a multi-beam laser device in order to shorten the exposure time. The exposure mechanism may be any of an internal drum system, an external drum system, a flatbed system, etc. Imagewise exposure can be carried out by a conventional method using a plate setter or the like. In the case of the on-press development system described below, the lithographic printing plate precursor may be mounted on a printing press and then imagewise exposure may be carried out on the printing press.

[0273] Examples of the removal step of removing the image-wise exposed lithographic printing plate precursor include a developer treatment step of removing the unexposed areas with a developer having a pH of 2 to 12, and an on-press development step of removing the unexposed areas with at least one of printing ink and fountain solution on a printing press.

[0274] <Developer Treatment Step> In the developer treatment step, the image-wise exposed lithographic printing plate precursor is treated with a developer having a pH of 2 to 14, and the image recording layer in the unexposed areas is removed to produce a lithographic printing plate. The developer preferably contains a compound having at least one acid group selected from the group consisting of a phosphoric acid group, a phosphonic acid group, and a phosphinic acid group, and one or more carboxyl groups, and has a pH of 5 to 10. For the developer treatment step, reference can be made to the methods and apparatuses for developer treatment described in WO 2023 / 032992, and the descriptions thereof are incorporated herein by reference.

[0275] <On-press development process> In the on-press development process, at least one of printing ink and fountain solution is supplied to the image-wise exposed lithographic printing plate precursor on a printing press, thereby removing the image recording layer in the unexposed areas, thereby producing a lithographic printing plate. That is, after imagewise exposure, the lithographic printing plate precursor is either mounted on a printing press as is without any developer treatment, or the lithographic printing plate precursor is mounted on a printing press and imagewise exposed on the press, and then printing is carried out by supplying printing ink and fountain solution. In the early stages of printing, the unexposed areas of the image recording layer are dissolved or dispersed and removed by the supplied printing ink and / or fountain solution in the unexposed areas, exposing a hydrophilic surface in those areas. Meanwhile, in the exposed areas, the image recording layer hardened by exposure forms an oil-based ink-receptive area having an oleophilic surface. Although either printing ink or fountain solution may be supplied to the plate surface first, it is preferable to supply printing ink first in order to prevent the fountain solution from being contaminated by the image-recording layer components that have been removed. In this way, a lithographic printing plate precursor is produced on a printing press by on-press development and is used as is for printing a large number of sheets.

[0276] <Printing Step> The printing method includes a printing step of printing a recording medium using a lithographic printing plate manufactured by the exposure step and on-press development step. As the printing ink used in the printing step, various known inks can be used as desired. As the printing ink, oil-based ink or ultraviolet-curable ink (UV ink) is preferred. In the printing step, dampening water may be further supplied as needed. The printing step may be performed continuously with the on-press development step without stopping the printing press. As the recording medium, known recording media can be used as desired.

[0277] In the method for producing a lithographic printing plate and the printing method, the entire surface of the lithographic printing plate precursor or lithographic printing plate may be heated, as necessary, at any stage: before exposure, during exposure, between exposure and development, or after development. Such heating promotes the image-forming reaction in the image-recording layer, and can provide advantages such as improved sensitivity and printing durability, and stabilized sensitivity. When the lithographic printing plate precursor is heated before development, it is preferably heated under mild conditions of 150°C or less, so that problems such as hardening of unexposed areas can be prevented. When the lithographic printing plate is heated after development, it is preferably heated under very strong conditions, for example, in the range of 100 to 500°C, so that sufficient image strengthening effect can be obtained and problems such as deterioration of the support and thermal decomposition of the image areas can be suppressed.

[0278] The present invention will be described in detail below using examples. However, the materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Note that for polymers, the molecular weight is the weight average molecular weight (Mw), and the ratio of repeating units is expressed as a mole percentage. Unless otherwise specified, the notation "%" means "% by mass" and the notation "parts" means "parts by mass."

[0279] [Production Example 1: Production of Support] <Production of Aluminum Plate> A molten aluminum alloy consisting of Si (0.27% by mass), Fe (0.52% by mass), Cu (0.07% by mass), Mn (0.07% by mass), Mg (0.26% by mass), Zn (0.08% by mass), Ti (0.06% by mass), the sum of Cr and Zr (0.06% by mass), and Al (98.61% by mass) was continuously cast using a twin-roll continuous casting method to a cast plate thickness of 5.5 mm. The molten aluminum alloy was obtained by adding various metals to high-purity aluminum ingot to adjust the content. The resulting continuously cast plate was then cold-rolled to a thickness of 0.9 mm, and then subjected to intermediate annealing heat treatment at 450°C for 4 hours. It was then cold-rolled again to a thickness of 0.3 mm. Flatness correction was then performed using a tension leveler to produce aluminum plate 1.

[0280] The resulting aluminum plate 1 is subjected to the following treatments to produce a support 1. Note that a water-washing treatment is carried out between all of the following treatment steps, and after the water-washing treatment, the liquid is drained off with nip rollers.

[0281] <Alkali Etching Treatment (1)> An aluminum plate is 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 aluminum plate is then rinsed with water by spraying. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment is 5 g / m. ２ is.

[0282] <Desmutting Treatment Using Acidic Aqueous Solution (1)> Next, desmutting treatment is performed using an acidic aqueous solution. Specifically, the acidic aqueous solution is sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used for the desmutting treatment is an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature is 30°C.

[0283] <Hydrochloric Acid Electrolysis> Next, hydrochloric acid electrolysis is performed using an electrolytic solution with a hydrochloric acid concentration of 13 g / L, an aluminum ion concentration of 15 g / L, and a sulfuric acid concentration of 1.0 g / L, using an alternating current. The temperature of the electrolytic solution is 25°C. The aluminum ion concentration is adjusted by adding aluminum chloride. The waveform of the alternating current is a sine wave with symmetrical positive and negative waveforms, a frequency of 50 Hz, the anode reaction time and cathode reaction time in one cycle of the alternating current are 1:1, and the current density is 35 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 300 C / dm ２ The electrolytic treatment is 75 C / dm ２ The test is carried out four times with a 2.5 second interval between each test. A carbon electrode is used as the counter electrode for the aluminum plate. After that, the plate is washed with water.

[0284] <Alkali Etching Treatment (2)> After the hydrochloric acid electrolysis, the aluminum plate is etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions at a temperature of 45° C. The amount of dissolved aluminum on the surface subjected to the hydrochloric acid electrolysis is 0.2 g / m ２ After that, a water washing process is carried out.

[0285] <Desmutting Treatment Using Acidic Aqueous Solution (2)> Next, desmutting treatment is performed using an acidic aqueous solution. Specifically, the acidic aqueous solution is sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used for the desmutting treatment is an aqueous solution with a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The liquid temperature is 35°C.

[0286] <First Anodizing Treatment> The first anodizing treatment is performed using a DC electrolysis anodizing apparatus having the structure shown in FIG. 6 . The anodizing treatment is performed under the conditions listed in the "First Anodizing Treatment" column in the table below, forming an anodized film with a predetermined thickness. The sulfuric acid concentration in the first anodizing treatment is 170 g / L. In the anodizing treatment apparatus 610 shown in FIG. 6 , an aluminum sheet 616 is transported as indicated by the arrow in FIG. 6 . In a power supply tank 612 containing an electrolytic solution 618, the aluminum sheet 616 is positively charged by a power supply electrode 620. The aluminum sheet 616 is then transported upward in the power supply tank 612 by rollers 622, redirected downward by nip rollers 624, and then transported toward an electrolytic treatment tank 614 containing an electrolytic solution 626, where it is redirected horizontally by rollers 628. Next, the aluminum plate 616 is negatively charged by the electrolysis electrode 630, thereby forming an anodized film on its surface, and the aluminum plate 616 leaving the electrolysis bath 614 is transported to a subsequent process. In the anodization device 610, a direction changing means is formed by the roller 622, the nip roller 624, and the roller 628, and the aluminum plate 616 is transported in a mountain-like and inverted U-like shape between the power supply bath 612 and the electrolysis bath 614 by the roller 622, the nip roller 624, and the roller 628. The power supply electrode 620 and the electrolysis electrode 630 are connected to a DC power supply 634. A bath wall 632 is disposed between the power supply bath 612 and the electrolysis bath 614.

[0287] <Pore Widening Treatment> The aluminum plate that has been subjected to the first anodizing treatment is immersed for 5 seconds in a caustic soda aqueous solution having a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass at a temperature of 40°C to perform a pore widening treatment. Thereafter, the aluminum plate is spray-washed and rinsed with water.

[0288] <Second Anodizing Treatment> The aluminum plate that has been subjected to the pore widening treatment is subjected to a second anodizing treatment using an anodizing apparatus that uses direct current electrolysis and has the structure shown in Figure 6. More specifically, the anodizing treatment is performed under the conditions described in the "Second Anodizing Treatment" column in the table below, to form an anodized film with a predetermined structure. The concentration of sulfuric acid in the second anodizing treatment is 170 g / L.

[0289] <Silicate Treatment> The aluminum plate that has been subjected to the second anodizing treatment is subjected to a silicate treatment to obtain a support 1. More specifically, the aluminum plate that has been subjected to the second anodizing treatment is immersed for 2.5 seconds in a No. 3 aqueous solution of sodium silicate with a concentration of 5% by mass and a liquid temperature of 45° C. This produces a support 1 that includes an aluminum plate and an anodized film.

[0290] [Production Examples 2 to 5, Comparative Production Examples 1 and 2] Supports 2 to 5 and C1 to C2 were produced in the same manner as in Production Example 1, except that in the <Production of Aluminum Plate> of Production Example 1, a molten aluminum alloy having the same composition as the composition of the aluminum plate shown in the table below was used.

[0291] [Preparation Examples 6 to 9] Supports 6 to 9 are prepared in the same manner as in Preparation Example 1, except that the conditions for the silicate treatment carried out in Preparation Example 1 are changed to the conditions shown in the table below.

[0292] [Production Example 10] A support 10 is produced in accordance with the same procedure as in Production Example 1, except that in <Production of Aluminum Plate> of Production Example 1, a molten aluminum alloy having the same composition as the composition of the aluminum plate shown in the table below is used, and the silicate treatment conditions are changed to the conditions shown in the table below.

[0293] The following table shows the composition of the aluminum plate of the support obtained in each production example. The composition of the aluminum plate of each support is the same as the composition of the molten aluminum alloy used in the production.

[0294] [Preparation of Undercoat Layer Coating Liquid] The components shown below are mixed to prepare an undercoat layer coating liquid A used for forming an undercoat layer.

[0295] (Undercoat layer coating solution A) Undercoat layer compound (1): 0.010 parts Chelest (registered trademark) 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 (registered trademark) L, manufactured by K.I. Kasei Co., Ltd.): 0.00149 parts Water: 2.8219 parts

[0296]

[0297] [Preparation of Image Recording Layer Coating Solution] The following components are mixed to prepare image recording layer coating solution A. The onium polymerization initiator represented by the following formula I-1 is an iodonium salt. Infrared absorber (IR-1 below): 0.0200 parts Infrared absorber (IR-2 below): 0.0050 parts Acid color former (S-1 below): 0.0300 parts Acid color former (S-2 below): 0.0120 parts Onium polymerization initiator (I-1 below): 0.0981 parts Borate compound (sodium tetraphenylborate (TPB)): 0.0270 parts Polymerizable compound (M-4 below, 70%): 0.3536 parts Fluorine-based surfactant (1) (structure below) 0.004 parts Anionic surfactant (A-1 below, 30%): 0.1620 parts 2-butanone: 5.3155 parts 1-methoxy-2-propanol: 2.8825 parts Methanol: 2.3391 parts Microgel liquid (5): 2.8779 parts

[0298]

[0299]

[0300]

[0301]

[0302]

[0303] (Synthesis of Polymerizable Compound M-4) A mixed solution of Takenate (registered trademark) D-160N (polyisocyanate trimethylolpropane adduct, manufactured by Mitsui Chemicals, Inc., 4.7 parts), Aronix (registered trademark) 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 are 1:1), t-butylbenzoquinone (0.02 parts), and methyl ethyl ketone (11.5 parts) was heated to 65°C. To the reaction solution, Neostan (registered trademark) 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 compound M-4) solution with a solids content of 50% by mass. Using a recycle-type GPC (instrument: LC908-C60, columns: JAIGEL-1H-40 and 2H-40 (manufactured by Japan Analytical Industry Co., Ltd.)), molecular weight fractionation of the urethane acrylate solution is carried out with an eluent of tetrahydrofuran (THF). The weight average molecular weight of the polymerizable compound M-4 is 20,000.

[0304] (Preparation of Microgel Liquid (5)) The following components are mixed to prepare the microgel liquid (5) used in preparing the image recording layer coating liquid A: Microgel (4) (solid content concentration: 21.8% by mass) 2.2707 parts 1-methoxy-2-propanol 0.6072 parts

[0305] Preparation of Microgel (4) The oil phase and aqueous phase components listed below were mixed and emulsified using a homogenizer at 12,000 rpm for 10 minutes. The resulting emulsion was stirred at 45°C for 4 hours, after which 5.20 parts of a 10% by weight aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) was added, stirred at room temperature for 30 minutes, and allowed to stand at 45°C for 24 hours. Distilled water was added to adjust the solids concentration to 21.8% by weight, yielding an aqueous dispersion of Microgel (4). The volume-average particle size measured by light scattering using a dynamic light scattering particle size distribution analyzer LB-500 (manufactured by Horiba, Ltd.) was 0.28 μm.

[0306] (Oil phase components) (Component 1) Ethyl acetate 12.0 parts (Component 2) An adduct obtained by adding trimethylolpropane (6 moles) and xylene diisocyanate (18 moles) to which one methyl-terminated polyoxyethylene (1 mole, number of repeating oxyethylene units: 90) has been added (50% by mass ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.) 3.76 parts (Component 3) Polyvalent isocyanate compound (1) (as a 50% by mass ethyl acetate solution) 15.0 parts (Component 4) 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer) 11.54 parts (Component 5) 10% ethyl acetate solution of sulfonate-type surfactant (Paionin A-41-C, manufactured by Takemoto Oil & Fat Co., Ltd.) 4.42 parts

[0307] (Aqueous phase components) Distilled water 46.87 parts

[0308] - Preparation of Polyisocyanate Compound (1) - 0.043 parts of bismuth tris(2-ethylhexanoate) (Neostane U-600, manufactured by Nitto Kasei Co., Ltd.) was added and stirred to a suspension of 17.78 parts (80 molar equivalents) of isophorone diisocyanate and 7.35 parts (20 molar equivalents) of the following polyhydric phenol compound (1) in ethyl acetate (25.31 parts). When the heat generation subsided, the reaction temperature was set to 50°C, and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50% by mass) of polyisocyanate compound (1).

[0309]

[0310] [Preparation of Protective Layer Coating Solution] The following components are mixed to prepare a protective layer coating solution A used to form a protective layer: Water: 1.0161 parts, Metrose (registered trademark) SM04 (methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd., methoxy substitution degree = 1.8): 0.0600 parts, FS-102 (styrene-acrylic resin, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg = 103°C, 17% aqueous dispersion): 0.1177 parts, Rapisol (registered trademark) A-80 (anionic surfactant, manufactured by NOF Corporation, 80% aqueous solution): 0.0063 parts

[0311] Example 1 The undercoat layer coating solution A was applied to the surface of the anodized film side of the support 1 produced in Production Example 1 in a dry coating amount of 0.1 g / m ２ and dried at 120°C for 40 seconds to form undercoat layer A. Onto the surface of the formed undercoat layer A, the image recording layer coating solution A prepared by the above method is applied with a bar, and dried in an oven at 120°C for 40 seconds to form a dry coating amount of 1.0 g / m ２ To obtain a laminate comprising the support 1, the undercoat layer A, and the image recording layer A, the following protective layer coating solution A is then applied to the surface of the formed image recording layer A with a bar, and dried in an oven at 120°C for 60 seconds to obtain a dry coating amount of 0.80 g / m ２ A protective layer A is formed on the support 1, the undercoat layer A, the image recording layer A, and the protective layer A are laminated to prepare a lithographic printing plate precursor.

[0312] [Examples 2 to 10, Comparative Examples 1 and 2] Lithographic printing plate precursors each having a support, an undercoat layer A, an image recording layer A, and a protective layer A laminated thereon were prepared according to the method described in Example 1, except that Supports 2 to 10 and C1 to C2 were used instead of Support 1, respectively.

[0313] [Measurement] <Specific Si atomic weight on coating surface> The specific Si atomic weight in the anodized coating of each support produced in Production Examples 1 to 10 and Comparative Production Examples 1 and 2 was measured using X-ray fluorescence analysis and a calibration curve method. The standard sample used to create the calibration curve was prepared by uniformly dropping an aqueous solution containing a known amount of silicon atoms onto an aluminum plate within an area of ​​30 mmφ and then drying it. The measurement conditions for the X-ray fluorescence analysis are shown below.

[0314] X-ray fluorescence analyzer: RIX3000 manufactured by Rigaku Electric Industrial Co., Ltd., X-ray tube: Rh, measurement spectrum: Si-Kα, tube voltage: 50 kV, tube current: 50 mA, slit: COARSE, analyzing crystal: RX4, detector: F-PC, analysis area: 30 mmφ, peak position (2θ): 144.75 deg., background (2θ): 140.70 deg. and 146.85 deg., accumulation time: 80 seconds / sample

[0315] [Evaluation] The lithographic printing plate precursors produced in each of the Examples and Comparative Examples were evaluated for the following performance.

[0316] <Evaluation of printing durability> The lithographic printing plate precursor prepared as described above was exposed using an infrared semiconductor laser exposure machine (FUJIFILM Corporation, "Luxel PLATESETTER T-6000III") under conditions of an outer drum rotation speed of 1000 rpm, a laser output of 70%, and a resolution of 2400 dpi (dots per inch, 1 inch = 2.54 cm). The exposed image included a solid image and a 50% halftone dot chart of a 20 μm dot FM (Frequency Modulation) screen. The resulting exposed lithographic printing plate precursor was attached to the plate cylinder of a Heidelberg SX-74 printing press without development. A 100 L fountain solution circulating tank equipped with a nonwoven fabric filter and a temperature control device was connected to this printing press. Using a dampening solution of Ecology-2 (manufactured by Fujifilm Corporation) / tap water = 2 / 98 (volume ratio) and Values-G(N) black ink (manufactured by Dainippon Ink and Chemicals, Inc.), the dampening solution and ink were supplied using the standard automatic print start method of the SX-74 printing press, and on-press development was carried out, after which printing was carried out on Tokubishi art paper (manufactured by Mitsubishi Paper Mills, ream weight 76.5 kg) at a printing speed of 10,000 sheets per hour. Note that in order to evaluate printing durability under harsh conditions, the above printing was carried out with the peripheral speed difference (slip rate) between the plate cylinder and the water roller set to 9%.

[0317] As the number of prints increases, the image recording layer gradually wears away, causing the ink density on the print to decrease. The number of prints at which it is visually recognized that the density of the solid image has begun to decrease compared to when printing began is taken as the number of prints evaluated. From the obtained number of prints evaluated, printing durability under severe conditions is evaluated according to the following evaluation criteria. The higher the number of prints evaluated, the better the printing durability.

[0318] (Evaluation criteria for print durability evaluation) A: The number of evaluated prints is 100,000 or more. B: The number of evaluated prints is 90,000 or more and less than 100,000. C: The number of evaluated prints is 80,000 or more and less than 90,000. D: The number of evaluated prints is 70,000 or more and less than 80,000. E: The number of evaluated prints is less than 70,000.

[0319] <Evaluation of print stains> In the above-mentioned printing durability evaluation test, the number of sheets of printing paper required from the start of on-press development to the completion of on-press development is measured. Immediately after the start of on-press development, the unexposed areas of the image recording layer may not be sufficiently peeled off by on-press development, and ink may be transferred from the unexposed areas to non-image areas on the paper surface of the printed matter (print stains). On-press development is judged to be complete when it is confirmed by visual observation that no ink has adhered to the non-image areas and no print stains are observed. Print stains are evaluated based on the number of prints at the time on-press development is completed, according to the following evaluation criteria. The smaller the number of prints, the better the performance in suppressing the occurrence of print stains.

[0320] (Evaluation criteria for print staining) A: On-press development is completed with 10 or fewer prints. B: On-press development is completed with 11 to 50 prints. C: On-press development is completed with 51 to 100 prints. D: Print staining occurs even when the number of prints exceeds 100, and on-press development is not completed.

[0321] <Evaluation of Time-Dependent Corrosion Failure Under High Humidity Conditions> After conditioning the lithographic printing plate precursor for 1 hour in a 25°C, 60% humidity environment, it was packaged in light-shielding, moisture-proof paper made of unbleached kraft paper laminated with polyethylene film and aluminum foil. The package was then heated at 60°C for 4 days. After heating, all ring-shaped colored areas within a 50 mm x 300 mm area were marked by scratching with an iron pen. After marking, the photosensitive layer was removed using a mixture of ethyl methyl ketone, 1-methoxy-2-propanol, and water (40% by weight, 40% by weight, and 20% by weight) to expose the support surface. The marked areas on the support surface were observed under a scanning electron microscope (SEM) at 2000x magnification, and the number of areas where corrosion marks were observed (number of corrosion marks) was counted. From the obtained number of corrosion marks, time-dependent corrosion failure under high humidity conditions was evaluated according to the following evaluation criteria. The fewer the number of corroded spots, the better the performance in suppressing corrosion failure over time under high humidity conditions and suppressing abnormal appearance under high humidity conditions.The greater the number of evaluated printed sheets, the better the printing durability.

[0322] (Evaluation criteria for corrosion failure over time under high humidity conditions) A: No corrosion. B: 1 to 10 corrosion. C: 11 to 20 corrosion. D: More than 20 corrosion.

[0323] The following table shows the configuration and evaluation results of the lithographic printing plate precursors of each Example and Comparative Example. In the table, the column "Liquid concentration (mass%)" for "Silicate treatment" indicates the percentage of the alkali metal silicate content relative to the total mass of the No. 3 sodium silicate aqueous solution used in the silicate treatment.

[0324]

[0325]

[0326] As shown in the table, the lithographic printing plate precursors of Examples 1 to 10 were rated highly for corrosion failure over time, and were able to suppress the occurrence of abnormal appearance even when left under high-humidity conditions, and were also able to suppress printing stains on the lithographic printing plate precursors, compared to the lithographic printing plate precursors of Comparative Examples 1 and 2, in which the aluminum plate did not satisfy the specific composition.

[0327] Comparison of Examples 1 and 6 to 9 reveals that when the specific Si atomic weight is 0.008 to 0.140 mg, the printing durability of the lithographic printing plate precursor is improved.

[0328] A comparison between Examples 1 and 2 shows that when the Fe content is more than 0.40 mass% and not more than 0.50 mass%, the Ti content is more than 0.03 mass% and not more than 0.05 mass%, and the total content of Cr and Zr is more than 0.03 mass% and not more than 0.05 mass%, relative to the total mass of the aluminum plate, the performance of suppressing appearance abnormalities under high-humidity conditions is improved.

[0329] A comparison between Examples 2 and 3 shows that the print stain suppression performance is improved when the Fe content is more than 0.40 mass% and not more than 0.45 mass%, the Ti content is more than 0.03 mass% and not more than 0.04 mass%, and the total content of Cr and Zr is more than 0.03 mass% and not more than 0.04 mass%, relative to the total mass of the aluminum plate.

[0330] A comparison between Examples 1 and 4 shows that when the Zn content is more than 0.05 mass % and not more than 0.07 mass % relative to the total mass of the aluminum plate, the performance of suppressing print staining is improved.

[0331] A comparison of Examples 1 and 5 shows that printing durability is improved when the Si content is 0.25 mass% or less, the Cu content is 0.05 mass% or less, and the Mn content is 0.05 mass% or less, relative to the total mass of the aluminum plate.

[0332] ta: Anode reaction time tc: Cathode reaction time tp: Time until current reaches its peak from 0 Ia: Current at peak in the anode cycle Ic: Current at peak in the cathode cycle 10: Planographic printing plate precursor 11: Support 12: Image recording layer 13: Aluminum plate 14, 14A, 14B: Anodized film 20, 30: Micropores 21, 31: Film surface 22, 32: Large diameter hole portion 22A, 24A, 32A, 34A, 36A: Bottom 23, 37, 39: Communication position 24, 34: Small diameter hole portion 36: Upper portion of large diameter hole portion 38: Lower portion of large diameter hole portion 50: Main electrolytic cell 51: AC power supply 52: Radial drum roller 53a, 53b: Main electrode 54: Electrolyte supply port 55: Electrolyte 56: Slit 57: Electrolyte passage 58 Auxiliary anode 60: Auxiliary anode cell W: Aluminum plate 610: Anodizing treatment device 612: Power supply cell 614: Electrolytic treatment cell 616: Aluminum plate 618, 626: Electrolyte 620: Power supply electrode 622, 628: Roller 624: Nip roller 630: Electrolytic electrode 632: Cell wall 634: DC power supply

Claims

1. A lithographic printing plate precursor having a support and an image recording layer containing an onium salt, wherein the support has an aluminum plate and an anodized film, the anodized film being disposed on the surface of the support facing the image recording layer, and the aluminum plate has an Fe content of more than 0.40 mass% relative to the total mass of the aluminum plate, an Mg content of more than 0.25 mass% relative to the total mass of the aluminum plate, a Zn content of more than 0.05 mass% relative to the total mass of the aluminum plate, a Ti content of more than 0.03 mass% relative to the total mass of the aluminum plate, and a total content of Cr and Zr of more than 0.03 mass% but not more than 0.08 mass% relative to the total mass of the aluminum plate.

2. The lithographic printing plate precursor according to claim 1, wherein the aluminum plate has an Fe content of more than 0.40 mass% and not more than 0.50 mass% relative to the total mass of the aluminum plate, a Ti content of more than 0.03 mass% and not more than 0.05 mass% relative to the total mass of the aluminum plate, and a combined Cr and Zr content of more than 0.03 mass% and not more than 0.05 mass% relative to the total mass of the aluminum plate.

3. The lithographic printing plate precursor according to claim 1 or 2, wherein the aluminum plate has a Mg content of more than 0.25 mass% and not more than 0.32 mass% relative to the total mass of the aluminum plate, and a Zn content of more than 0.05 mass% and not more than 0.07 mass% relative to the total mass of the aluminum plate.

4. The lithographic printing plate precursor according to claim 1 or 2, wherein the aluminum plate has an Si content of 0.25 mass% or less relative to the total mass of the aluminum plate, an Cu content of 0.05 mass% or less relative to the total mass of the aluminum plate, and an Mn content of 0.05 mass% or less relative to the total mass of the aluminum plate.

5. The lithographic printing plate precursor according to claim 1 or 2, wherein the average Si atomic weight calculated by measuring a circular region having a diameter of 30 mm on the surface of the anodic oxide coating on the image recording layer side by X-ray fluorescence analysis is 0.008 to 0.140 mg.

6. The lithographic printing plate precursor according to claim 1 or 2, wherein the image recording layer is a negative-working image recording layer.

7. A method for producing a lithographic printing plate, comprising: an exposure step of exposing the image recording layer of the lithographic printing plate precursor according to claim 1 or 2 to light in an imagewise manner to form exposed and unexposed areas; and an on-press development step of supplying at least one of printing ink and fountain solution on a printing press to remove the unexposed areas of the imagewise exposed image recording layer, thereby producing a lithographic printing plate.

8. A printing method comprising: an exposure step of exposing the image recording layer of the lithographic printing plate precursor according to claim 1 or 2 to light in an imagewise manner to form exposed and unexposed areas; an on-press development step of supplying at least one of printing ink and dampening water on a printing press to remove the unexposed areas of the imagewise exposed image recording layer, thereby preparing a lithographic printing plate; and a printing step of carrying out printing using the prepared lithographic printing plate.

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