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

Abstract

The present invention addresses the problem of providing an on-press development type lithographic printing plate precursor having excellent printing durability, a method for producing a lithographic printing plate, and a printing method. An on-press development type lithographic printing plate precursor according to the present invention comprises a support and an image recording layer. The support has an aluminum plate and an anodic oxide film disposed on the aluminum plate. The anodic oxide film has a plurality of micropores. The micropores each have a large-diameter hole portion extending from the film surface to a position at a depth of 0.05-0.50 μm, and a small-diameter hole portion communicating with the bottom part of the large-diameter hole portion. The average diameter of the large-diameter hole portions at the film surface is 0.015-0.070 μm, and when a circular area having a diameter of 30 mm of the surface on the image recording layer side of the anodic oxide film is measured by X-ray fluorescence analysis, the calculated average value of the Si atomic weight is 0.008-0.14 mg.

Description

On-press development type lithographic printing plate precursor, lithographic printing plate manufacturing method, printing method

[0001] The present invention relates to an on-press development type 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] With growing concern about the global environment, attention has been focused on issues related to waste liquids associated with wet processes such as development. To address these issues, efforts are being made to simplify or eliminate development or platemaking, and one of the countermeasures is a method called "on-press development." In other words, this method involves exposing a lithographic printing plate precursor to light and then directly mounting it on a printing press without development, and removing unnecessary portions of the image-recording layer at an early stage of the printing process.

[0004] An example of a lithographic printing plate precursor used for such on-press development is that described in Patent Document 1. Patent Document 1 describes a lithographic printing plate precursor having an image recording layer, which contains an infrared absorber, a polymerization initiator, and a polymerizable compound on an aluminum support that has been treated with an alkali metal silicate and is removable with printing ink and / or fountain solution, and in which the amount of Si element attached to the surface of the aluminum support during the alkali metal silicate treatment is 1 mg / m ２ 10mg / m or more ２ The technology relates to a lithographic printing plate precursor having a particle size of less than 1 / 2 mm.

[0005] Japanese Patent Application Laid-Open No. 2005-014348

[0006] The present inventors have studied the properties of the lithographic printing plate precursor described in Patent Document 1 and have found that when this lithographic printing plate precursor is used, it may not satisfy the higher level of printing durability that is currently required, and that there is room for further improvement in the printing durability of the lithographic printing plate precursor.

[0007] In view of the above circumstances, an object of the present invention is to provide an on-press development type lithographic printing plate precursor having excellent printing durability. Another object of the present invention is to provide a method for producing a lithographic printing plate and a printing method.

[0008] The present inventors have found that the above problems can be solved by the following configuration.

[0009] [1] An on-press development type lithographic printing plate precursor having a support and an image recording layer, wherein the support comprises an aluminum plate and an anodized film disposed on the aluminum plate, the anodized film having a plurality of micropores extending in the depth direction from the surface on the image recording layer side, the micropores having large-diameter pores extending from the surface of the anodized film to a depth of 0.05 to 0.50 μm, and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend in the depth direction from the communicating positions, the large-diameter pores having an average diameter of 0.015 to 0.070 μm at the surface of the anodized film, and the average Si atomic weight calculated by measuring a circular region with a diameter of 30 mm on the surface of the anodized film on the image recording layer side by X-ray fluorescence analysis is 0.008 to 0.14 mg. [2] The density of the micropores on the surface of the anodic oxide film is 200 to 2000 / μm ２[3] The on-press developable lithographic printing plate precursor according to [1], wherein the ratio of the average maximum diameter of the interior of the large diameter portions to the average diameter of the large diameter portions at the surface of the anodized film is 1.2 to 10.0. [4] The on-press developable lithographic printing plate precursor according to any one of [1] to [3], further comprising an undercoat layer disposed between the support and the image recording layer, the undercoat layer comprising a polymer having a support adsorptive group and a hydrophilic group. [5] The on-press developable lithographic printing plate precursor according to [4], wherein the polymer has a support adsorptive group, a hydrophilic group, and a polymerizable group. [6] The on-press developable lithographic printing plate precursor according to [4] or [5], wherein the hydrophilic group has a zwitterionic structure. [7] The on-press developable lithographic printing plate precursor according to any one of [1] to [6], wherein the image recording layer comprises an infrared absorbing agent. [8] The on-press developable lithographic printing plate precursor according to [7], wherein the infrared absorber has a substituent that is cleaved by infrared light or heat. [9] The on-press developable lithographic printing plate precursor according to any one of [1] to [8], wherein the image recording layer contains a borate compound.

[10] The on-press developable lithographic printing plate precursor according to any one of [1] to [9], wherein the image recording layer contains an acid color former.

[11] The on-press developable lithographic printing plate precursor according to any one of [1] to

[10] , wherein the average Si atomic weight calculated by measuring a circular region with a diameter of 30 mm on the surface of the anodized coating on the image recording layer side by X-ray fluorescence analysis is 0.010 to 0.080 mg.

[12] The on-press developable lithographic printing plate precursor according to any one of [1] to

[11] , wherein an 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 fluorescent X-ray analysis is 0.011 to 0.060 mg.

[13] A method for producing a lithographic printing plate, comprising: an exposure step of imagewise exposing the image recording layer of the on-press developable lithographic printing plate precursor according to any one of [1] to

[12] 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.

[14] A printing method comprising: an exposure step of imagewise exposing the image recording layer of the on-press developable lithographic printing plate precursor according to any one of [1] to

[12] 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 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.

[0010] According to the present invention, it is possible to provide an on-press development type lithographic printing plate precursor having excellent printing durability. Furthermore, according to the present invention, it is possible to provide a method for producing a lithographic printing plate and a printing method.

[0011] 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.

[0012] 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. In this specification, 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 in the composition or polymer, unless otherwise specified, when the composition contains multiple substances or structural units corresponding to each component or structural unit in the polymer. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are molecular weights obtained by detecting the molecular weight of a 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" encompasses not only lithographic printing plate precursors but also disposable plate precursors. The term "lithographic printing plate" includes not only a lithographic printing plate prepared by subjecting a lithographic printing plate precursor to exposure, development, and other procedures as necessary, but also a throwaway plate.In the case of a throwaway plate precursor, exposure and development operations are not necessarily required. A throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when, for example, a portion of a page is printed in one color or two colors in color newspaper printing. In 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.

[0013] [On-press development type lithographic printing plate precursor] The on-press development type lithographic printing plate precursor according to the present invention is an on-press development type lithographic printing plate precursor having a support and an image recording layer, wherein the support comprises an aluminum plate and an anodized coating disposed on the aluminum plate. The anodized coating has a plurality of micropores extending in the depth direction from the surface on the image recording layer side, and the micropores have large-diameter pores having a predetermined shape and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend in the depth direction from the communicating positions. Furthermore, the average Si atomic weight calculated by measuring the surface on the image recording layer side of the anodized coating by fluorescent X-ray analysis is 0.008 to 0.14 mg.

[0014] The structure of the on-press development type lithographic printing plate precursor (hereinafter also simply referred to as "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 disposed on the aluminum plate 13. It should be noted that the structure of the lithographic printing plate precursor is not limited to the embodiment shown in FIG. 1. For example, as will be described later, 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.

[0015] [Support] The lithographic printing plate precursor according to the present invention has a support having an aluminum plate and an anodized film disposed on the aluminum plate. 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 disposed on the aluminum plate, unless otherwise specified.

[0016] <Aluminum Plate> The aluminum plate is made of a dimensionally stable metal containing aluminum as a main component, and examples of such metals include aluminum and aluminum alloys. For the aluminum plate, reference can be made to the aluminum plate described in WO 2023 / 032992, the description of which is incorporated herein by reference.

[0017] <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:

[0018] (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.

[0019] In the present invention, the micropores formed in the anodized coating on the support have a pore structure (hereinafter also referred to as a "specific structure") in which the micropores have large-diameter pores extending from the surface of the coating to a depth of 0.05 to 0.5 μm and small-diameter pores communicating with the bottoms of the large-diameter pores and extending in the depth direction from the communicating positions, and the large-diameter pores have an average diameter d1 at the surface of the coating of 0.015 to 0.1 μm. The specific structure of the micropores will be described in more detail below with reference to the drawings. Note that the specific structure of the micropores in the anodized coating of the present invention is not limited to the embodiments shown in the drawings.

[0020] 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.

[0021] The average diameter d1 (average opening diameter) of the large diameter pores 22 at the coating surface 21 is 0.015 to 0.070 μm. When the average diameter d1 of the large diameter pores 22 at the coating surface 21 is within the above range, the printing durability of the on-press development type lithographic printing plate precursor is further improved. The average diameter d1 of the large diameter pores 22 at the coating surface 21 is more preferably 0.020 to 0.050 μm, and even more preferably 0.022 to 0.040 μm, in terms of further improved printing durability. The average diameter d1 of the large diameter pores of the micropores at the coating surface 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 coating surface at four different locations. ２The value is obtained by arbitrarily selecting measurement areas on each image, measuring the diameters of 50 micropores present in the measurement area on each image, and arithmetically averaging the measured values ​​at 200 measurement points obtained from the four images. Note that when the shape of the openings of the large-diameter micropores on the coating surface is not circular, the opening diameter of each micropore can be determined by measuring the distance between the two points that are the greatest distance apart from each other on the periphery of the openings.

[0022] The depth D1 of the large diameter pores (the distance from the coating surface 21 to the bottom 22A) is 0.05 to 0.50 μm, and is preferably 0.08 to 0.30 μm, and more preferably 0.10 to 0.30 μm, in terms of better printing durability. The depth D1 of the large diameter pores, the depth D2 of the small diameter pores described below, and the depth of the micropores described below are values ​​obtained by observing the cross sections of the micropores along the depth direction of the anodized coating using an FE-SEM at a magnification of 150,000 times, observing four different cross sections, randomly selecting 25 or more micropores from the four observation images obtained, measuring the depths of the selected micropores, the large diameter pores, and the small diameter pores, and then arithmetically averaging the measured values.

[0023] The shape of the large diameter hole is not limited to the substantially straight tubular shape (substantially cylindrical shape) shown in Figure 2, and the diameter of the large diameter hole may change continuously or discontinuously in the depth direction. Examples of shapes in which the diameter of the large diameter hole changes 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 holes with different diameters are connected in the depth direction (see Figure 3). The shape of the large diameter hole is preferably a substantially straight tubular shape. The shape of the bottom of the large diameter hole is not particularly limited, and may be a curved (convex) shape like bottom 22A shown in Figure 2, or a flat shape.

[0024] 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. ｍａｘ is a value obtained by observing the cross section of a micropore along the depth direction of an anodized film using an FE-SEM at a magnification of 150,000 times, randomly selecting 25 micropores from four images obtained by observing four different cross sections, measuring the maximum diameter of the large-diameter pore portion of the selected micropores inside the anodized film, and arithmetically averaging the measured values.

[0025] 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.

[0026] The average diameter d2 of the small-diameter pores 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 pores 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. The lower limit is not particularly limited, but 5 nm or more is preferred. The average diameter d2 of the small-diameter pores at the communication positions is a value obtained by observing the cross section of the micropores along the depth direction of the anodized coating using a field-emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, observing at four different locations, obtaining four images, arbitrarily selecting 20 points from each of the four images, measuring the pore diameters (diameters) of the small-diameter pores at the communication positions, and then arithmetically averaging all the measured values.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 36A) and the depth D1b of the lower large-diameter hole portions 38 (the distance from the bottom 36A to the bottom 38A) corresponds to the depth D1 of the large-diameter hole portions, and is 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, and 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, and more preferably 0.05 to 0.2 μm. The depth D1u of the large diameter hole upper portion 36 and the depth D1b of the large diameter hole lower portion 38 can be measured in accordance with the method for measuring the depth D1 of the large diameter hole described above.

[0032] 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.

[0033] 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-machine 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-machine 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. The maximum diameter of the large-diameter hole lower portions 38 is preferably 1.2 to 10.0, more preferably 1.2 to 5.0, from the viewpoint of achieving both on-machine developability and printing durability. ｍａｘ It can be measured in accordance with the measurement method.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 depth of the micropores means the distance in the depth direction from the surface of the micropore coating to the deepest part of the bottom of the micropore.

[0038] 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 with 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.

[0039] 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.

[0040] (Si atomic weight) In the lithographic printing plate precursor according to the present invention, the average Si atomic weight (hereinafter also referred to as the "specific Si atomic weight") calculated by measuring a circular region with a diameter of 30 mm on the surface of the anodized coating on the support facing the image recording layer by X-ray fluorescence analysis is 0.008 to 0.14 mg.

[0041] The present inventors have discovered that the printing durability of a lithographic printing plate precursor can be further improved by providing micropores formed in an anodized coating on a support that have a specific structure consisting of large-diameter pores at the coating surface that are 0.05 to 0.5 μm deep and have an average diameter d1 of 0.015 to 0.1 μm at the coating surface, and small-diameter pores that communicate with the bottoms of the large-diameter pores, and by providing a specific Si atomic weight in the surface of the anodized coating that is within the above range. The details of the mechanism by which the on-press development type lithographic printing plate precursor according to the present invention has superior printing durability are not clear, but are presumed to be as follows. On the surface of an anodized coating on which micropores having the above-described specific structure are formed, the image recording layer not only accumulates on the apparent surface, but also potentially penetrates into the interior of each micropore. Therefore, in an anodized film having micropores having the above-mentioned specific structure formed on its surface, the area where the image recording layer is substantially in contact with the surface of the support is different from that of an anodized film having no micropores formed on its surface, and therefore the appropriate range of the Si content relative to the apparent surface is thought to be different. In the lithographic printing plate precursor according to the present invention, it is presumed that by specifying the specific Si atomic weight on the film surface to the above range corresponding to an anodized film having micropores having a specific structure formed on its surface, it has been possible to provide an on-press development type lithographic printing plate precursor having excellent printing durability (particularly printing durability under severe conditions).

[0042] The specific Si atomic weight is obtained by performing X-ray fluorescence analysis on a circular region of 30 mm diameter 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 surface of the anodized coating facing the image recording layer, 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.

[0043] In Patent Document 1, the amount of Si element deposited on the surface of an aluminum support treated with an alkali metal silicate is 10 mg / m ２ It is described that if the adhesion amount exceeds 10 mg / m2, the adhesion between the image recording layer and the aluminum support decreases, and printing durability decreases. Since it is described that this adhesion amount is measured by fluorescent X-ray analysis, it is presumed that the adhesion amount is usually calculated by dividing the measured amount of Si by the measurement area for fluorescent X-ray analysis. Here, the adhesion amount of 10 mg / m2 of Si element described in Patent Document 1 ２ When converted to the specific Si atomic weight in the 30 mm circular region of this case, this is calculated to be approximately 0.007 mg, which is not included in the range specified in the present invention. As shown in Comparative Examples 2 and 3 in the examples described later, when the specific Si atomic weight is 0.007 mg, the requirements of the present invention are not met, and it cannot be said that the technology disclosed in Patent Document 1 solves the problems of the present invention.

[0044] The specific Si atomic weight per circular region with a diameter of 30 mm on the surface of the anodized coating is preferably 0.08 to 0.14 mg, more preferably 0.010 to 0.080 mg, and even more preferably 0.011 to 0.060 mg, from the viewpoint of balancing on-press developability, ink removability, and printing durability.

[0045] 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.

[0046] (Recess Density) In terms of superior printing durability, the support has a density of recesses (hereinafter also referred to as "specific recesses") having a depth of 0.7 μm or more from the average surface, as measured by a non-contact three-dimensional roughness meter over an area of ​​400 μm × 400 μm on the surface of the support on the anodized film side, of 3,000 to 10,000 recesses / mm ２ is preferably 3500 to 8000 pieces / mm ２ More preferably, 5000 to 8000 pieces / mm２ is more preferred.

[0047] The density of specific recesses in the support refers to a value measured as follows. First, a non-contact three-dimensional roughness meter (VertScan, manufactured by Ryoka Systems Co., Ltd.) is used to scan a 400 μm × 400 μm area on the surface of the anodized film side (image recording layer side) of the support in a non-contact manner with a resolution of 1 μm to obtain three-dimensional data. The VertScan device details and measurement conditions are as follows: (1) Device details CCD camera: Sony HR-57 Objective lens: ×10 Lens barrel: ×1 Wavelength filter: 530 white (2) Measurement conditions Measurement mode: wave Field of view range: 400 μm × 400 μm Scan range: start +6 μm, stop -10 μm Next, the obtained three-dimensional data is subjected to image analysis using software (VS Viewer, manufactured by Ryoka Systems Co., Ltd.), and the number of recesses having a depth from the obtained average surface of 0.7 μm or more is determined. The average surface refers to the surface located at a height obtained by averaging the height values ​​of all measurement data on the surface of the support on the image recording layer side within the measurement area (400 μm×400 μm). Measurements were taken at five locations per sample, the number of predetermined recesses was calculated at each location, and the average value was then calculated to obtain the average value of the unit area (mm ２ ) and use this as the density of the specific recesses.

[0048] (Specific Surface Area ΔS) The specific surface area ΔS is calculated by the following formula (S1) using the actual area Sx determined by the approximate three-point method from three-dimensional data obtained by measuring 256 × 256 points in a 25 μm × 25 μm area on the surface of the support facing the anodized film using an atomic force microscope, and the geometrically measured area S0 of the surface of the anodized film. In terms of superior printing durability, the specific surface area ΔS is preferably 20 to 70%, and more preferably 30 to 60%: ΔS = (Sx - S0) / S0 × 100(%) ... (S1)

[0049] The specific surface area ΔS of the support is a value measured as follows. Specifically, the support is cut into 1 cm square pieces and placed on a horizontal sample stage on a piezo scanner. The cantilever is brought close to the sample surface. Once it reaches the region where atomic force is active, it is scanned in the XY direction, capturing the unevenness of the sample by the displacement of the piezo in the Z direction. A piezo scanner capable of scanning 100 μm in the XY direction and 15 μm in the Z direction is used. A cantilever with a resonant frequency of 120 to 200 kHz and a spring constant of 7 to 20 N / m (e.g., "OMCL-AC200-TS" (manufactured by Olympus Corporation) and "SI-DF20" (manufactured by NANOPROBE) is used, and measurements are performed in DFM mode (Dynamic Force Mode). Furthermore, slight tilts of the sample are corrected by least-squares approximation of the obtained three-dimensional data to determine the reference plane. The measurement is performed at 512 x 512 points over a 25 x 25 μm area on the surface, with a resolution of 0.05 μm in the X direction, 0.05 μm in the Y direction, and 1 nm in the Z direction, and a scanning speed of 18 μm / sec.

[0050] (Lightness) From the viewpoint of improving the image visibility of an on-press development type lithographic printing plate precursor, it is useful for the surface of the anodic oxide film of the support to have high lightness. In the printing process of a lithographic printing plate, a plate inspection is usually carried out to check whether the intended image has been recorded before the printing plate is mounted on the printing press. Since it is required to check the image at the stage of image exposure for an on-press development type lithographic printing plate precursor, a means of producing a so-called print-out image in the image-exposed area is applied. A method for quantitatively evaluating the visibility (visibility) of the image area of ​​an image-exposed on-press development type lithographic printing plate precursor is to measure the lightness of the image-exposed area and the lightness of the unexposed area and calculate the difference between them. Here, lightness is measured using the CIE L ＊ a ＊ b ＊ Lightness L in the color system ＊The value of the lightness can be used, and the lightness can be measured using a color difference meter (SpectroEye (registered trademark), manufactured by X-Rite). The larger the difference in lightness between the image-exposed part and the unexposed part obtained by measurement, the easier the image part will be to see. Improvement in visibility, that is, the larger the difference in lightness between the image-exposed part and the unexposed part, the better the L of the anodized film surface. ＊ a ＊ b ＊ Lightness L in the color system ＊ The value is preferably 60 to 100, more preferably 70 to 90.

[0051] 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.

[0052] <Support Manufacturing Method> The support used in the lithographic printing plate precursor of the present invention can be manufactured using known methods. Examples of methods for manufacturing a support include a roughening step in which an aluminum plate is roughened, and an anodizing step in which the roughened aluminum plate is anodized to form an aluminum anodized film on the aluminum plate. Among these, a method that further includes a pore-widening step in which, after the anodizing step, the aluminum plate on which the anodized film has been formed is etched to enlarge the diameter of the micropores in the anodized film, and a second anodizing step in which the pore-widening step is further anodized is also preferred. Also preferred is a method that further includes a silicate treatment step in which the aluminum plate on which the anodized film has been formed is subjected to a silicate treatment, as described below. 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.

[0053] (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.

[0054] (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.

[0055] (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.

[0056] 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.

[0057] 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 ２ More 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.

[0058] 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.

[0059] 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.

[0060] (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.

[0061] 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., can be sufficiently removed from the surface. 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] (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.

[0067] (Water washing treatment) In the method for producing a support, it is preferable to wash with water after the 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.

[0068] (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.

[0069] 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.

[0070] (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.

[0071] (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.

[0072] (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.

[0073] (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.

[0074] 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.

[0075] 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 (specific 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.

[0076] [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.

[0077] <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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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, and WO 2019 / 219560, the descriptions of which are incorporated herein by reference.

[0086] Examples of the substituent that is cleaved by infrared rays or heat that the decomposable infrared absorber has include —O—R １ , -NR ａ R ｂ , -NR ｃ (SO ２ R ｄ ) and -NR ｅ (CO ２ R ｆ ) groups represented by the formula (I) are exemplified. １ is irradiated by heat or infrared exposure. １ represents a substituent in which the —O bond is cleaved, and R ａ and R ｂ each independently represents an aryl group; R ｃ , R ｅ and Rｆ each independently represents an alkyl group or an aryl group; R ｄ is an alkyl group, an aryl group, or —NR ｄ１ R ｄ２ represents R ｄ１ and R ｄ２ Each of the —O—R independently represents a hydrogen atom, an alkyl group, or an aryl group. １ , -NR ａ R ｂ , -NR ｃ (SO ２ R ｄ ) and -NR ｅ (CO ２ R ｆ Preferred embodiments of the group represented by the formula (I) will be described later.

[0087] From the viewpoint of on-press developability and chemical resistance, the decomposable infrared absorber is more preferably a compound represented by the following formula (A).

[0088]

[0089] In formula A, ＋ Y Ａ１ = has the following structure:

[0090]

[0091] and Y Ａ２ - has the following structure:

[0092]

[0093] n is 0, 1, 2 or 3; p and q are each independently 0, 1 or 2; R Ａ１ and R Ａ２ each independently represents a hydrocarbon group, or R Ａ１ , R Ａ２ , R Ａｄ and R Ａａ two of R comprise the atoms necessary to form a cyclic structure together; Ａｄ At least one of the R Ａｄ represents a group that is converted into a group that is a stronger electron donor, or R ＡａAt least one of the R Ａａ represents a group that is converted into a group that is a stronger electron donor, and other R Ａｄ and R Ａａ are each independently a hydrogen atom, a halogen atom, or —R Ａｅ , -OR Ａｆ , -SR Ａｇ and -NR Ａｕ R Ａｖ represents a group selected from the group consisting of Ａｅ , R Ａｆ , R Ａｇ , R Ａｕ and R Ａｖ each independently represents an aliphatic hydrocarbon group, an aryl group, or a heteroaryl group, and the conversion is a conversion that provides an increase in light absorption in the wavelength range of 400 nm to 700 nm. Ａ１ and R Ａ２ and the hydrocarbon group in R Ａｅ , R Ａｆ , R Ａｇ , R Ａｕ and R Ａｖ The aliphatic hydrocarbon group, aryl group or heteroaryl group in may have a substituent.

[0094] In addition, the above R Ａｄ is preferably any one of the groups shown below.

[0095]

[0096] In the above formula, Aa, Ab, Ac, and Ad each independently represent 0 or 1; Ａ - represents a bonding group, R Ａ１７ represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group, or R Ａ１７ and R Ａ３ , R Ａ１７ and R Ａ５ , or R Ａ１７ and R Ａ１１ and R Ａ４ is -ORＡ１０ , -NR Ａ１３ R Ａ１４ or -CF ３ and R Ａ１０ represents an optionally substituted aryl group, an optionally substituted heteroaryl group, or an α-branched aliphatic hydrocarbon group; R Ａ１３ and R Ａ１４ each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group, or R Ａ１３ and R Ａ１４ and R Ａ３ is a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group, or R Ａ３ is R Ａ１０ , R Ａ１３ and R Ａ１４ and R Ａ６ represents an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, an optionally substituted heteroaryl group, —OR Ａ１０ , -NR Ａ１３ R Ａ１４ or -CF ３ where R Ａ１０ , R Ａ１３ and R Ａ１４ is R Ａ４ has the same meaning as in Ａ５ represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group, or R Ａ５ is R Ａ１０ , R Ａ１３ and R Ａ１４ and R Ａ１１ , R Ａ１５ and R Ａ１６each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group, or R Ａ１５ and R Ａ１６ and R Ａ１２ represents an optionally substituted aliphatic hydrocarbon group, an optionally substituted aryl group, or an optionally substituted heteroaryl group; R Ａ７ and R Ａ９ each independently represents a hydrogen atom or an optionally substituted aliphatic hydrocarbon group, R Ａ８ is -COO- or -COOR Ａ８’ where R Ａ８’ represents a hydrogen atom, an alkali metal cation, an ammonium ion, or a mono-, di-, tri-, or tetra-alkylammonium ion; R Ａ１８ represents an optionally substituted aryl group, an optionally substituted heteroaryl group, or an α-branched aliphatic hydrocarbon group.

[0097] As the compound having a substituent that is cleaved by exposure to heat or infrared light, a compound represented by the following formula (1) is particularly preferred from the viewpoints of on-machine developability and chemical resistance.

[0098]

[0099] In formula (1), M １ is a substituent that is cleaved by exposure to heat or infrared light, and R ２ and R ３ each independently represents a hydrogen atom or an alkyl group; R ２ and R ３ may be linked to each other to form a ring, and Ar １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring; Y １ and Y ２ are each independently an oxygen atom, a sulfur atom, or —NR ０ - or a dialkylmethylene group, R ４ and R５ each independently represents an aliphatic hydrocarbon group, R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group; R ０ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0100] The compound represented by the formula (1) is preferably a compound that decomposes upon exposure to heat or infrared rays to produce a compound having a maximum absorption wavelength in the range of 500 nm to 600 nm.

[0101] M in formula (1) １ Preferred embodiments of R will be described later. ２ ~R ９ , R ０ , Ar １ and Ar ２ may have a substituent such as a hydrophilic group, which will be described later. Examples of the substituent include an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, a phosphonic acid group, a phosphonate group, and combinations thereof. When the above group is an anionic group, it may form a salt, and the counter cation may be a cation of a cyanine dye structure, a proton, a metal cation, an onium, or the like.

[0102] R in formula (1) ２ ~R ９ and R ０ The alkyl group in the formula (I) is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and even more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a cyclic structure. Among the alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is preferred.

[0103] R ０The aryl group in the formula (I) is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms. The aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and combinations thereof. Specific examples include a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, and a naphthyl group.

[0104] R ２ and R ３ are preferably linked to form a ring. ２ and R ３ When they are linked to form a ring, the ring is preferably a 5- or 6-membered ring, more preferably a 6-membered ring.

[0105] Y １ and Y ２ are each independently an oxygen atom, a sulfur atom, or —NR ０ represents - or a dialkylmethylene group, -NR ０ - or a dialkylmethylene group is preferred, and a dialkylmethylene group is more preferred. ０ represents a hydrogen atom, an alkyl group or an aryl group, and is preferably an alkyl group.

[0106] R ４ and R ５ are preferably the same group. ４ and R ５ When R has an anionic group, ４ and R ５ It is preferable that R has an anionic group and is the same group except for whether it has a counter cation or not. ４ and R ５are each independently preferably a linear alkyl group or an alkyl group having a terminal sulfonate group, more preferably a methyl group, an ethyl group, or a butyl group having a terminal sulfonate group. The counter cation of the sulfonate group may be a quaternary ammonium group in formula (1), or an alkali metal cation or an alkaline earth metal cation.

[0107] R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom. １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a group formed by combining these groups.

[0108] Za represents a counter ion that neutralizes the charge, and when it represents an anionic species, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, and a perchlorate ion, with a hexafluorophosphate ion being particularly preferred. When it represents a cationic species, an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is preferred, a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is more preferred, and a sodium ion, a potassium ion, or an ammonium ion is even more preferred. R １ ~R ９ , R ０ , Ar １ , Ar ２ , Y １ and Y ２ may have an anionic structure or a cationic structure, and R １ ~R ９ , R０ , Ar １ , Ar ２ , Y １ and Y ２ If all of R are charge-neutral groups, Za is a monovalent counter anion. １ ~R ９ , R ０ , Ar １ , Ar ２ , Y １ and Y ２ When the compound has two or more anionic structures, Za can also be a counter cation.

[0109] M in the above formula (1) １ is -NR from the viewpoint of edge stain suppression, color development, and color development over time. ａ R ｂ , -NR ｃ (SO ２ R ｄ ) or -NR ｅ (CO ２ R ｆ ) is preferable, provided that R ａ and R ｂ each independently represents an aryl group; R ｃ , R ｅ and R ｆ each independently represents an alkyl group or an aryl group; R ｄ is an alkyl group, an aryl group, or —NR ｄ１ R ｄ２ represents R ｄ１ and R ｄ２ each independently represents a hydrogen atom, an alkyl group, or an aryl group.

[0110] R ｃ ~R ｆ , R ｄ１ and R ｄ２ The alkyl group in R is preferably an alkyl group having 1 to 20 carbon atoms. ａ ~R ｆ , R ｄ１ and R ｄ２ The aryl group in R is preferably an aryl group having 6 to 20 carbon atoms. ａ ~R ｆ , R ｄ１ and Rｄ２ The alkyl group and aryl group in may have a substituent. Examples of the substituent include an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, a phosphonic acid group, a phosphonate group, and combinations thereof. When the above group is an anionic group, it may form a salt, and the counter cation may be a cation of a cyanine dye structure, a proton, a metal cation, an onium, or the like.

[0111] Furthermore, M in the above formula (1) １ is -O-R １ However, it is preferable that R １ is irradiated by heat or infrared exposure. １ represents a substituent in which the —O bond is cleaved.

[0112] From the viewpoint of color development, R １ is preferably a group represented by any one of the following formulas 1-1 to 1-7, and more preferably a group represented by any one of the following formulas 1-1 to 1-3.

[0113]

[0114] In Formula 1-1 to Formula 1-7, ● represents a bonding site with an oxygen atom, and R ２０ are each independently a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or —OR ２４ , -NR ２５ R ２６ or -SR ２７ represents R ２１ each independently represents a hydrogen atom, an alkyl group, or an aryl group; R ２２ is an aryl group, —OR ２４ , -NR ２５ R ２６ , -SR ２７ , -C(=O)R ２８ , -OC(=O)R ２８ or a halogen atom, R ２３ represents an aryl group, an alkenyl group, an alkoxy group, or an onium group; R ２４ ~R２７ each independently represents a hydrogen atom, an alkyl group, or an aryl group; R ２８ are each independently an alkyl group, an aryl group, or —OR ２４ , -NR ２５ R ２６ or -SR ２７ represents Z １ represents a counter ion that neutralizes the charge.

[0115] Specific examples of the above compounds are shown below. In the following structural formula, Me represents a methyl group, and TsO － represents the tosylate anion.

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131] 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.

[0132] <Acid Color Former> The image recording layer 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, more preferably 100 to 180°C.

[0133] 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.

[0134] As the acid color former, from the viewpoints of developability, color developability, and visibility after aging, a compound represented by the following formula (3a) or formula (3b) is preferred, and a compound represented by the following formula (3a) is more preferred.

[0135]

[0136] In formula (3a), Ar １ and Ar ２ each independently represents an aryl group which may have a substituent or a heteroaryl group which may have a substituent, R １０ and R １１ each independently represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent.

[0137] In formula (3b), each ERG independently represents an electron-donating group, n represents an integer of 1 to 5, and X １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group; Y １ and Y ２ each independently represents C or N, Y １ If N, then X １ does not exist, and Y ２ If N, then X ４ does not exist, and R １２ and R １３ each independently represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent.

[0138] The alkyl group in formula (3a) or formula (3b) may be linear, branched, or have a ring structure. The number of carbon atoms in the alkyl group in formula (3a) or formula (3b) is preferably 1 to 20, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 or 2. The number of carbon atoms in the aryl group in formula (3a) or formula (3b) is preferably 6 to 20, more preferably 6 to 10, and even more preferably 6 to 8. Examples of the aryl group in formula (3a) or formula (3b) include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group, each of which may have a substituent. Examples of the heteroaryl group in formula (3a) or formula (3b) include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group, each of which may have a substituent.

[0139] In addition, each group such as an alkyl group, an aryl group, and a heteroaryl group in formula (3a) or formula (3b) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, and a cyano group. In addition, these substituents may be further substituted with these substituents.

[0140] The substituent may be an electron-donating group. From the viewpoints of color development and visibility, the electron-donating group represented by ERG and the electron-donating group that is the substituent are preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and still more preferably an alkoxy group.

[0141] R in formula (3a) １０ and R １１ From the viewpoint of color development and visibility, each of Ar and Ar in Formula (3a) is preferably an alkyl group or an aryl group which may have an electron-donating group, more preferably a methyl group or an aryl group having an electron-donating group, and even more preferably a phenyl group having an electron-donating group at the para position. １ and Ar ２From the viewpoint of color development and visibility, each of the groups is preferably an aryl group which may have at least one substituent at the ortho position, or a heteroaryl group which may have at least one substituent at the ortho position, more preferably an aryl group which has at least one substituent at the ortho position, still more preferably a phenyl group which has at least one substituent at the ortho position, and particularly preferably a phenyl group which has at least one substituent at the ortho position and an electron-donating group at the para position.

[0142] R in formula (3b) １２ and R １３ From the viewpoint of color development and visibility, X is preferably a hydrogen atom or an aryl group substituted with an alkyl group or an alkoxy group, more preferably an alkyl group, and still more preferably a methyl group. n in formula (3b) is preferably an integer of 1 to 3, more preferably 1 or 2. X in formula (3b) １ ~X ４ are each independently preferably a hydrogen atom or a chlorine atom, more preferably a hydrogen atom, from the viewpoint of color development and visibility. １ and Y ２ From the viewpoint of color development and visibility, it is preferable that at least one of Y is C, １ and Y ２ It is more preferable that both of are C.

[0143] Specific preferred examples of the acid color former include the following compounds S-1 to S-20, where Me represents a methyl group, Et represents an ethyl group, and Ph represents a phenyl group.

[0144]

[0145]

[0146]

[0147]

[0148]

[0149] 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.

[0150] <Polymerization initiator> The image recording layer preferably contains a polymerization initiator. The 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. As the 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.

[0151] Examples of the polymerization initiator include an electron-accepting polymerization initiator and an electron-donating polymerization initiator. The image recording layer preferably contains at least one of an electron-accepting polymerization initiator and an electron-donating polymerization initiator as the polymerization initiator, and more preferably contains both an electron-accepting polymerization initiator and an electron-donating polymerization initiator.

[0152] (Electron-accepting polymerization initiator) The 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. As the electron-accepting polymerization initiator, a known thermal polymerization initiator, a compound having a bond with small bond dissociation energy, a photopolymerization initiator, etc. can be appropriately used.

[0153] The 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, (j) an oxime ester compound, and (k) an onium salt compound.

[0154] (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. (k) Examples of onium salt compounds include the compounds described in JP-A-2008-195018, paragraphs 0028 to 0030.

[0155] The radical polymerization initiator is preferably an onium-based polymerization initiator. The onium-based polymerization initiator is an onium salt compound that generates a polymerization initiating species such as a radical by accepting electrons through intermolecular electron transfer when electrons of an infrared absorber are excited by infrared exposure. As the onium-based polymerization initiator, an iodonium salt compound, a sulfonium salt compound, or an azinium salt compound is preferred, in terms of superior printing durability, and an iodonium salt compound is more preferred, with an iodonium salt compound being even more preferred.

[0156] 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.

[0157] 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.

[0158] The electron-accepting polymerization initiator may be used alone or in combination of two or more. The content of the electron-accepting polymerization initiator is preferably 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.

[0159] (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.

[0160] The image recording layer preferably contains a borate compound as an electron-donating polymerization initiator. As the borate compound, a tetraarylborate compound or a monoalkyltriarylborate compound is preferred, 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. As the borate compound, sodium tetraphenylborate is preferred.

[0161] When the image recording layer contains a borate compound as an electron-donating polymerization initiator, it is more preferable that the image recording layer further contains an onium salt compound as an electron-accepting polymerization initiator, from the viewpoints of visibility, printing durability, and stability over time.

[0162] A preferred example of a preferred embodiment of the image recording layer containing both an electron-accepting polymerization initiator and an electron-donating polymerization initiator is an embodiment in which the electron-accepting polymerization initiator and the electron-donating polymerization initiator form a salt. Examples of salts formed by the electron-accepting polymerization initiator and the electron-donating polymerization initiator include iodonium borate compounds formed by an iodonium compound, which is an onium polymerization initiator, and a borate compound. Specific examples of the iodonium borate compounds include the compounds described in International Publication No. 2020 / 262692.

[0163] 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.

[0164] The content of the polymerization initiator (total content of the electron-accepting polymerization initiator and the 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.

[0165] The content of the polymerization initiator (total content of the electron-accepting polymerization initiator and the 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.

[0166] <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.

[0167] 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).

[0168] 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.

[0169] (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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] (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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] <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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] <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.

[0189] 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.

[0190] 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.

[0191]

[0044] <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, unwanted thermal polymerization of polymerizable compounds, particularly radically polymerizable compounds, can be prevented during production or storage of the image recording layer.

[0192] Examples of polymerization inhibitors include hydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), and N-nitroso-N-phenylhydroxylamine aluminum salt.

[0193] As the polymerization inhibitor, a compound represented by the following formula (Ph) is preferred in that it has better stability over time and developability after aging.

[0194]

[0195] In the formula (Ph), X Ｐ represents O, S or NH, Y Ｐ represents N or CH, R Ｐ１ represents a hydrogen atom or an alkyl group, R Ｐ２ and R Ｐ３ each independently represents a halogen atom, an alkylthio group, an arylthio group, an alkoxy group, an aryloxy group, an alkyl group, an aryl group, an acylthio group, or an acyl group; mp and np each independently represent an integer of 0 to 4.

[0196] X in formula (Ph) Ｐ In terms of stability over time and developability after aging, Y is preferably O or S, and more preferably S. Ｐ In terms of stability over time and developability after aging, R is preferably N. Ｐ１ From the viewpoint of stability over time and developability after aging, R is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom. Ｐ２ and R Ｐ３are each independently preferably a halogen atom, an alkylthio group, an arylthio group, an alkoxy group, an aryloxy group, an alkyl group, or an aryl group. In formula (Ph), mp and np are each independently preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0, from the viewpoints of stability over time and developability after time.

[0197] 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.

[0198] <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 having 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.

[0199] 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.

[0200] <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.

[0201] <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 in, for example, 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.

[0202] 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).

[0203] [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.

[0204] <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.

[0205] The components constituting the undercoat layer are not particularly limited, but in terms of better printing durability, it is preferable that the undercoat layer contain a polymer having a support-adsorbing group and a hydrophilic group (hereinafter also referred to as "polymer I"). Although the details of the mechanism by which the undercoat layer containing polymer I improves the printing durability of a lithographic printing plate precursor are not clear, it is presumed that by forming micropores having the specific structure described above and disposing an undercoat layer containing polymer I on the surface of an anodized coating having a specific Si atomic weight within a predetermined range, an attractive interaction occurs between the Si atoms present on the coating surface and the inner walls of the micropores and the support-adsorbing groups of polymer I, and the hydrophilic groups of polymer I act on the image recording layer, resulting in improved adhesion between the support and the image recording layer and improved printing durability.

[0206] 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.

[0207] 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 resistance to staining due to leaving the ink unattended. 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 a neutral overall structure. 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.

[0208] Polymer I is preferably a copolymer having a repeating unit having a group selected from the group consisting of a phosphonic acid group, a phosphate ester group, and a salt thereof at its side chain, and a repeating unit having at least one of a zwitterionic structure and a polyalkyleneoxy structure at its side chain. This embodiment provides superior printing durability and resistance to staining due to longevity. In this specification, the term "main chain" refers to the relatively longest linking chain in the molecule of the polymer compound constituting the resin, and the term "side chain" refers to a linking chain branched from the main chain. In this specification, a repeating unit having a group selected from the group consisting of a phosphonic acid group, a phosphate ester group, and a salt thereof is also referred to as repeating unit A, and a repeating unit having a zwitterionic structure is also referred to as repeating unit B.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] The weight-average molecular weight (Mw) of polymer I can be set arbitrarily depending on the performance design of the lithographic printing plate precursor. In terms of better printing durability and stain resistance, 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.

[0213] 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).

[0214] 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.

[0215] (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.

[0216] <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.

[0217] 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 water-soluble polymers or hydrophobic polymers (water-insoluble polymers), and two or more types can be mixed as needed. However, from the viewpoint of on-press developability, water-soluble polymers are 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. Examples of water-soluble polymers used in the protective layer include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, cellulose derivatives, polyethylene glycol, and poly(meth)acrylonitrile. Furthermore, the water-soluble polymer preferably contains at least one selected from the group consisting of modified polyvinyl alcohol and cellulose derivatives. The modified polyvinyl alcohol preferably used is an acid-modified polyvinyl alcohol having a carboxy group or a sulfo group. Specific examples include the modified polyvinyl alcohols described in JP-A Nos. 2005-250216 and 2006-259137. Examples of cellulose derivatives include methyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.

[0218] Among the water-soluble polymers, polyvinyl alcohol is preferably contained, and polyvinyl alcohol having a degree of saponification of 50% or more is more preferably contained. The degree of saponification is preferably 60% or more, more preferably 70% or more, and even more preferably 85% or more. The upper limit of the degree of saponification is not particularly limited, and it is sufficient that it is 100% or less. The degree of saponification is measured according to the method described in JIS K 6726:1994. Another preferred embodiment of the protective layer includes polyvinyl alcohol and polyethylene glycol.

[0219] 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 from 1 to 99% by mass, more preferably from 3 to 97% by mass, and even more preferably from 5 to 95% by mass.

[0220] The protective layer preferably contains a hydrophobic polymer. A hydrophobic polymer refers to a polymer that dissolves in an amount of less than 5 g in 100 g of pure water at 125°C or does not dissolve at all. Examples of hydrophobic polymers include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly(meth)acrylic acid alkyl esters (e.g., polymethyl(meth)acrylate, polyethyl(meth)acrylate, polybutyl(meth)acrylate, etc.), and copolymers combining the raw material monomers of these resins. The hydrophobic polymer preferably contains a polyvinylidene chloride resin. Furthermore, the hydrophobic polymer preferably contains a styrene-acrylic copolymer (also referred to as a styrene-acrylic resin). From the viewpoint of on-press developability, the hydrophobic polymer is preferably a hydrophobic polymer particle.

[0221] The hydrophobic polymer may be used alone or in combination of two or more. When the protective layer contains a hydrophobic polymer, the content of the hydrophobic polymer is preferably 1 to 70% by mass, more preferably 5 to 50% by mass, and still more preferably 10 to 40% by mass, based on the total mass of the protective layer.

[0222] 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.

[0223] 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.

[0224] From the viewpoint of suppressing development defects, the protective layer preferably contains a filler. Examples of the filler 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 suppress redeposited matter from the roll surface from directly adhering to the surface of the image recording layer.

[0225] The inorganic layered compound is a particle having a thin, tabular shape, and examples thereof include mica groups such as natural mica and synthetic mica, and compounds having the formula: 3MgO.4SiO.H ２ Examples of the inorganic layered compound include talc, taeniolite, montmorillonite, saponite, hectorite, and zirconium phosphate represented by the formula: A(B, C) ２－５ D ４ O １０ (OH, F, O) ２[wherein A is any of K, Na, and Ca, B and C are any of Fe(II), Fe(III), Mn, Al, Mg, and V, and D is Si or Al. ] Examples of the inorganic layered compound include mica groups such as natural mica and synthetic mica. Examples of the inorganic layered compound include the inorganic layered compounds described in WO 2020 / 262692, the description of which is incorporated herein by reference.

[0226] Examples of inorganic particles include metal oxide particles such as silica particles. The inorganic layered compounds described below are not included in the inorganic particles. Examples of organic resin particles include crosslinked resin particles.

[0227] The content of the filler (preferably an inorganic layered compound) is preferably 1 to 60% by mass, and 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] [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.

[0232] 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).

[0233] 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.

[0234] [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>.

[0235] 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.

[0236] [Method for producing a 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 are described below. The method for producing a lithographic printing plate of the present invention includes a step of imagewise exposing the image recording layer of the lithographic printing plate precursor to light (imagewise exposure) to form exposed and unexposed areas (exposure step), and a step of supplying at least one of printing ink and fountain solution on a printing press to remove the unexposed areas of the image recording layer to produce a lithographic printing plate (on-press development step). The printing method of the present invention includes, for example, a step of imagewise exposing the image recording layer of the lithographic printing plate precursor to light (imagewise exposure) to form exposed and unexposed areas (exposure step), a step of supplying at least one of printing ink and fountain solution on a printing press to remove the unexposed areas of the image recording layer to produce a lithographic printing plate (on-press development step), and a step of printing using the produced lithographic printing plate (printing step). Each of these steps is described in detail below.

[0237] <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. Image exposure can be carried out by a conventional method using a plate setter or the like. Image exposure may also be carried out on the printing press after the lithographic printing plate precursor is mounted on the printing press.

[0238] <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.

[0239] <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.

[0240] In the method for preparing a lithographic printing plate and the printing method, the entire surface of the lithographic printing plate precursor or the 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 preferable to heat it under mild conditions of 150°C or less, so that problems such as hardening of the unexposed areas can be prevented. When the lithographic printing plate is heated after development, it is preferable to heat it under very strong conditions, for example, in the range of 100 to 500°C, so that sufficient image strengthening can be achieved and problems such as deterioration of the support and thermal decomposition of the image areas can be suppressed.

[0241] 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. Furthermore, the notation "%" means "% by mass," and the notation "parts" means "parts by mass."

[0242] [Production Example 1: Production of Support] An aluminum plate (aluminum alloy plate) having a thickness of 0.3 mm and a material of 1S was subjected to the following treatments to produce Support 1. Note that a water-rinsing treatment was carried out between all treatment steps, and after the water-rinsing treatment, the liquid was removed using nip rollers.

[0243] <Alkali Etching Treatment (1)> An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The aluminum was then rinsed with water by spraying. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m. ２ It was.

[0244] <Desmutting Treatment Using Acidic Aqueous Solution (1)> Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used in the desmutting treatment was an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature was 30°C.

[0245] <Hydrochloric Acid Electrolysis> Next, hydrochloric acid electrolysis was 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 was 25°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The waveform of the alternating current was a sine wave with symmetrical positive and negative waveforms, the frequency was 50 Hz, the anode reaction time and cathode reaction time in one cycle of the alternating current were 1:1, and the current density was 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 was carried out four times with a 2.5 second interval between each test. A carbon electrode was used as the counter electrode for the aluminum plate. After that, the aluminum plate was washed with water.

[0246] <Alkali Etching Treatment (2)> After the hydrochloric acid electrolysis, the aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions onto the plate at a temperature of 45° C. The amount of dissolved aluminum on the surface subjected to the hydrochloric acid electrolysis was 0.2 g / m ２ After that, a water washing treatment was carried out.

[0247] <Desmutting Treatment Using Acidic Aqueous Solution (2)> Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used in the desmutting treatment had a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The liquid temperature was 35°C.

[0248] <First Anodizing Treatment> The first anodizing treatment was performed using a DC electrolysis anodizing apparatus having the structure shown in FIG. 6 . Anodizing treatment was performed under the conditions shown in Table 1 to form an anodized film with a predetermined thickness. The sulfuric acid concentration in the first anodizing treatment was 170 g / L. In the anodizing treatment apparatus 610 shown in FIG. 6 , an aluminum sheet 616 is conveyed 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 conveyed upward in the power supply tank 612 by rollers 622, redirected downward by nip rollers 624, and conveyed 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.

[0249] <Pore Widening Treatment> The aluminum plate that had been subjected to the first anodizing treatment was immersed in an aqueous caustic soda solution having a temperature of 40°C, a caustic soda concentration of 5 mass %, and an aluminum ion concentration of 0.5 mass %, to perform a pore widening treatment for the treatment time shown in Table 1. Thereafter, the aluminum plate was washed with water by spraying.

[0250] <Second Anodizing Treatment> The aluminum plate that had been subjected to the pore widening treatment was subjected to a second anodizing treatment using an anodizing apparatus using direct current electrolysis having the structure shown in Fig. 6. More specifically, the anodizing treatment was performed under the conditions shown in the "Second Anodizing Treatment" column in Table 1, to form an anodized film having a predetermined structure. The concentration of sulfuric acid in the second anodizing treatment was 170 g / L.

[0251] <Silicate Treatment> The aluminum plate that had been subjected to the second anodizing treatment was subjected to a silicate treatment to obtain a support 1. More specifically, the aluminum plate that had been subjected to the second anodizing treatment was immersed for 12 seconds in a No. 3 aqueous solution of sodium silicate with a concentration of 5% by mass and a liquid temperature of 40°C.

[0252] [Production Examples 2 to 29] Supports 2 to 29 were produced in the same manner as in Production Example 1, except that the conditions for each treatment carried out in Production Example 1 were changed to the conditions shown in Table 1. In the table, the "Concentration (mass %)" column for "Silicate Treatment" indicates the percentage of the alkali metal silicate content relative to the total mass of the No. 3 aqueous sodium silicate solution used in the silicate treatment.

[0253]

[0254]

[0255] [Preparation of Undercoat Layer Coating Liquid] The components shown below were mixed to prepare undercoat layer coating liquids A to C used for forming the undercoat layer.

[0256] (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, K.I. Chemical Co., Ltd.): 0.00149 parts Water: 2.8219 parts

[0257]

[0258] (Undercoat layer coating solution B) Undercoat layer compound (2): 0.010 parts Chelest 400 (chelating agent, manufactured by Chelest Co., Ltd.): 0.0280 parts Chelest 3EAF (chelating agent, manufactured by Chelest Co., Ltd.): 0.0499 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts Preservative (Biohope L, manufactured by K.I. Kasei Co., Ltd.): 0.00149 parts Water: 2.8219 parts

[0259]

[0260] Compound (3) for undercoat layer: 0.010 parts Chelest 400 (chelating agent, manufactured by Chelest Co., Ltd.): 0.0280 parts Chelest 3EAF (chelating agent, manufactured by Chelest Co., Ltd.): 0.0499 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts Preservative (Biohope L, K.I. Kasei Co., Ltd.): 0.00149 parts Water: 2.8219 parts

[0261]

[0262] [Preparation of Image Recording Layer Coating Liquid] <Image Recording Layer Coating Liquid A> The components shown below were mixed to prepare image recording layer coating liquid A. 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-based 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

[0263]

[0264]

[0265]

[0266]

[0267]

[0268] (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 were 1:1), t-butylbenzoquinone (0.02 parts), and methyl ethyl ketone (11.5 parts) was heated to 65 ° C. To the reaction solution, Neostan (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 was carried out with an eluent of tetrahydrofuran (THF). The weight average molecular weight of the polymerizable compound M-4 was 20,000.

[0269] (Preparation of Microgel Liquid (5)) The following components were mixed to prepare a microgel liquid (5) to be used in preparing an 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

[0270] Preparation of Microgel (4) The oil phase components and aqueous phase components listed below were mixed and emulsified for 10 minutes at 12,000 rpm using a homogenizer. The resulting emulsion was stirred at 45°C for 4 hours, 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 was measured by light scattering using a dynamic light scattering particle size distribution analyzer LB-500 (manufactured by Horiba, Ltd.) and found to be 0.28 μm.

[0271] (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

[0272] (Aqueous phase components) Distilled water 46.87 parts

[0273] - 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). Once the heat generation subsided, the reaction temperature was set to 50°C, and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50% by mass) of polyisocyanate compound (1).

[0274]

[0275] <Image Recording Layer Coating Solution B> The following components were mixed to prepare image recording layer coating solution B. 2-Butanone: 5.3155 parts 1-Methoxy-2-propanol: 2.8825 parts Methanol: 2.3391 parts Polymerizable compound (M-4 above, 70%): 0.3571 parts Electron-accepting polymerization initiator (I-1 above): 0.025 parts Borate compound (sodium tetraphenylborate (TPB)): 0.030 parts Cleavable color-forming compound (infrared absorber) (IR-3 below): 0.035 parts Tricresyl phosphate: 0.0125 parts Anionic surfactant (A-1 above): 0.0162 parts Microgel liquid (5): 2.8779 parts Fluorine-based surfactant (1) (structure above): 0.0042 parts

[0276]

[0277] [Preparation of Protective Layer Coating Solution] The following components were mixed to prepare a protective layer coating solution A used for forming 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.

[0278] [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 method described above was applied with a bar, and then dried in an oven at 120°C for 40 seconds to form a dry coating amount of 1.0 g / m ２ Thus, a laminate was obtained in which the support 1, the undercoat layer A, and the image recording layer A were laminated. Next, the protective layer coating solution A described below was applied to the surface of the formed image recording layer A with a bar, and the resultant was dried in an oven at 120°C for 60 seconds, resulting in a dry coating amount of 0.80 g / m ２A protective layer A of the above was formed, and a lithographic printing plate precursor having the support, undercoat layer A, image recording layer A, and protective layer A laminated thereon was prepared.

[0279] [Examples 2 to 22, Comparative Examples 1 to 4] 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 in accordance with the method described in Example 1, except that Supports 2 to 22 and 26 to 29 were used instead of Support 1, as shown in Table 2 below.

[0280] [Example 23] A lithographic printing plate precursor having a support, an undercoat layer B, an image recording layer A, and a protective layer A laminated together was prepared in accordance with the method described in Example 6, except that Support 23 was used instead of Support 1, and that Undercoat Layer Coating Liquid B was used instead of Undercoat Layer Coating Liquid A to form Undercoat Layer B.

[0281] [Example 24] A lithographic printing plate precursor having a support, an undercoat layer C, an image recording layer A, and a protective layer A laminated together was prepared in accordance with the method described in Example 6, except that support 24 was used instead of support 1, and undercoat layer C was formed using undercoat layer coating liquid C instead of undercoat layer coating liquid A.

[0282] [Example 25] A lithographic printing plate precursor having a support, an undercoat layer A, an image recording layer B, and a protective layer A laminated together was prepared in accordance with the method described in Example 6, except that Support 25 was used instead of Support 1, and that Image Recording Layer Coating Liquid B was used instead of Image Recording Layer Coating Liquid A to form Image Recording Layer B.

[0283] [Measurement] <Micropore Density> The density of micropores in the anodized film on each of the supports produced in Production Examples 1 to 29 was measured by the method using the FE-SEM described above. The density of micropores in the anodized film measured for each support (unit: number / μm ２ ) are shown in Table 2 below.

[0284] <Specific Si Atomic Weight on Coating Surface> The specific Si atomic weight in the anodized coating of each of the supports produced in Production Examples 1 to 29 was measured using X-ray fluorescence analysis and a calibration curve method. The standard sample used to create the calibration curve was an aqueous solution containing a known amount of silicon atoms, which was uniformly dropped onto an aluminum plate within an area of ​​30 mmφ and then dried. The measurement conditions for the X-ray fluorescence analysis are shown below.

[0285] 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

[0286] [Evaluation] The lithographic printing plate precursors produced in each of the Examples and Comparative Examples were evaluated for the following performance.

[0287] <Evaluation of Printing Durability (1)> 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 mounted on 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 performed, followed by printing 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 performed with the peripheral speed difference (slip ratio) between the plate cylinder and the water roller set to 9%.

[0288] As the number of prints increased, the image recording layer gradually wore away, and the ink density on the prints decreased. The number of prints at which it was visually confirmed that the density of the solid image began to decrease compared to when printing began was taken as the number of prints evaluated. From the obtained number of prints evaluated, printing durability under severe conditions was evaluated according to the following evaluation criteria. The higher the number of prints evaluated, the better the printing durability.

[0289] (Evaluation criteria for printing durability evaluation (1)) 10: The number of evaluated prints is 100,000 or more. 9: The number of evaluated prints is 90,000 or more but less than 100,000. 8: The number of evaluated prints is 80,000 or more but less than 90,000. 7: The number of evaluated prints is 70,000 or more but less than 80,000. 6: The number of evaluated prints is 60,000 or more but less than 70,000. 5: The number of evaluated prints is 50,000 or more but less than 60,000. 4: The number of evaluated prints is 40,000 or more but less than 50,000. 3: The number of evaluated prints is 30,000 or more but less than 40,000. 2: The number of evaluated prints is 20,000 or more but less than 30,000. 1: The number of evaluated prints is less than 20,000.

[0290] <Evaluation of printing durability (2)> The lithographic printing plate precursor prepared as described above was exposed using an exposure machine equipped with an infrared semiconductor laser ("Luxel PLATESETTER T-6000III" manufactured by Fujifilm Corporation) 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 is 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 exposed lithographic printing plate precursor obtained was mounted on the plate cylinder of a printing press ("LITHRONE26" manufactured by Komori Corporation) without development processing. Using a dampening solution of Ecology-2 (manufactured by Fujifilm Corporation) / tap water = 2 / 98 (volume ratio) and a light blue spot color ink (ink with a calcium carbonate content of 20% by mass), the dampening solution and ink were supplied using the standard automatic print start method of the printing press, and on-press development was performed, 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. In order to evaluate printing durability under harsh conditions, an ink with a calcium carbonate content of 20% by mass was used.

[0291] As the number of prints increased, the image recording layer gradually wore away, resulting in a decrease in ink density on the prints. The number of prints at which it was visually confirmed that the density of the solid image had begun to decrease compared to when printing began was taken as the number of prints evaluated. From the obtained number of prints evaluated, printing durability under severe conditions was evaluated according to the following evaluation criteria. The higher the number of prints evaluated, the better the printing durability.

[0292] (Evaluation criteria for printing durability evaluation (2)) 10: The number of evaluated prints is 100,000 or more. 9: The number of evaluated prints is 90,000 or more but less than 100,000. 8: The number of evaluated prints is 80,000 or more but less than 90,000. 7: The number of evaluated prints is 70,000 or more but less than 80,000. 6: The number of evaluated prints is 60,000 or more but less than 70,000. 5: The number of evaluated prints is 50,000 or more but less than 60,000. 4: The number of evaluated prints is 40,000 or more but less than 50,000. 3: The number of evaluated prints is 30,000 or more but less than 40,000. 2: The number of evaluated prints is 20,000 or more but less than 30,000. 1: The number of evaluated prints is less than 20,000.

[0293] <Evaluation of on-press developability> The obtained lithographic printing plate precursor was exposed using an exposure machine equipped with an infrared semiconductor laser ("Luxel PLATESETTER T-6000III" manufactured by Fujifilm Corporation) under conditions of an outer drum rotation speed of 1000 rpm, a laser output of 70%, and a resolution of 2,400 dpi. The exposure was imagewise exposure including a solid image and a 50% halftone dot chart of an FM (Frequency Modulation) screen. The image-exposed lithographic printing plate precursor was attached to the plate cylinder of a printing machine "LITHRONE26" (manufactured by Komori Corporation) without being developed. Using a dampening solution of Ecology-2 (manufactured by Fujifilm Corporation) / tap water = 2 / 98 (volume ratio) and Values-G(N) black ink (manufactured by Dainippon Ink and Chemicals, Inc.), the dampening solution and ink were supplied using the standard automatic printing start method of the printing press described above, and on-press development was performed. Then, printing was performed on 100 sheets of Tokubishi art paper (ream weight: 76.5 kg, manufactured by Mitsubishi Paper Mills, Ltd.) at a printing speed of 10,000 sheets per hour. The number of printed sheets required until on-press development of the unexposed areas of the 50% halftone dot chart was completed on the printing press and no ink was transferred to the non-halftone dot image areas (hereinafter also referred to as "number of sheets wasted") was measured. On-press developability was evaluated based on the measured number of sheets wasted, according to the following criteria. As described below, the fewer the number of sheets wasted, the better the on-press developability.

[0294] (Evaluation criteria for on-press developability) 10: 5 or fewer sheets were lost. 9: 6 to 10 sheets were lost. 8: 11 to 15 sheets were lost. 7: 16 to 19 sheets were lost. 6: 20 to 25 sheets were lost. 5: 26 to 29 sheets were lost. 4: 30 to 34 sheets were lost. 3: 35 to 39 sheets were lost. 2: 40 to 50 sheets were lost. 1: 51 or more sheets were lost.

[0295] <Evaluation of Ink Removal Properties> In the above-mentioned on-press developability evaluation test, after a good printout was obtained in which no ink had been transferred to the halftone dot non-image areas, an evaluation test ink, which was made by adding varnish to ink ("Fushion-EZ(S)" manufactured by Dainippon Ink and Chemicals, Inc.), was applied to the non-image areas of the lithographic printing plate, and printing was resumed. After printing was resumed, the number of sheets of printing paper required to obtain a good printout with no visible stains (number of sheets wasted) was measured. Ink removability was evaluated from the measured number of sheets wasted based on the following criteria. As shown below, the fewer the number of sheets wasted, the better the ink removability.

[0296] (Ink removal performance evaluation criteria) 10: 5 or fewer sheets were lost. 9: 6 to 10 sheets were lost. 8: 11 to 15 sheets were lost. 7: 16 to 19 sheets were lost. 6: 20 to 25 sheets were lost. 5: 26 to 29 sheets were lost. 4: 30 to 34 sheets were lost. 3: 35 to 39 sheets were lost. 2: 40 to 50 sheets were lost. 1: 51 or more sheets were lost.

[0297] Table 2 shows the structure and evaluation results of the planographic printing plate precursors of each Example and Comparative Example. ｍａｘ " and "D1" columns indicate the average diameter d1 on the coating surface of the large diameter hole portion and the average maximum diameter d1 inside, respectively. ｍａｘand depth D1. In the "Small diameter pore" column, the "d2" and "D2" columns indicate the average diameter d2 and depth D2, respectively, at the positions where the small diameter pores communicate with the large diameter pores. In the table, "*1" means that in the lithographic printing plate precursors of Comparative Examples 1 and 2, the micropores formed in the anodized coating were cylindrical pores with an average diameter of 0.012 μm at the coating surface and extending to a depth of 1 μm from the coating surface.

[0298]

[0299] As is clear from Table 2, it was confirmed that the lithographic printing plate precursors of Examples 1 to 25 had better printing durability than the lithographic printing plate precursors of Comparative Examples 1 and 2, in which the micropores did not have a specific structure, and the lithographic printing plate precursors of Comparative Examples 3 and 4, in which the specific Si atomic weight was less than 0.008 mg or more than 0.14 mg.

[0300] From a comparison of Examples 1 to 10, it was confirmed that when the specific Si atomic weight is 0.008 to 0.138 mg, the printing durability of the lithographic printing plate precursor is even better, and when the specific Si atomic weight is 0.012 to 0.035 mg, the printing durability of the lithographic printing plate precursor is particularly good.

[0301] From a comparison between Examples 1 and 11 to 14, it was confirmed that when the average diameter d1 of the large diameter pores on the coating surface was 0.022 to 0.040 μm, the printing durability of the lithographic printing plate precursor was superior.

[0302] From a comparison between Examples 1 and 15 to 18, it was confirmed that when the depth D1 of the large diameter pores from the coating surface was 0.08 to 0.30 μm, the printing durability of the lithographic printing plate precursor was superior.

[0303] Comparison of Examples 6, 23 and 24 confirmed that the use of a polymer having a polymerizable group in the undercoat layer resulted in a lithographic printing plate precursor with superior printing durability.

[0304] 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. An on-press development type lithographic printing plate precursor having a support and an image recording layer, wherein the support comprises an aluminum plate and an anodized film disposed on the aluminum plate, the anodized film has a plurality of micropores extending in the depth direction from the surface on the image recording layer side, the micropores having large diameter portions extending from the surface of the anodized film to a depth of 0.05 to 0.50 μm and small diameter portions communicating with the bottoms of the large diameter portions and extending in the depth direction from the communicating positions, the large diameter portions having an average diameter of 0.015 to 0.070 μm on the surface of the anodized film, and the average Si atomic weight calculated by measuring a circular region having a diameter of 30 mm on the surface of the anodized film on the image recording layer side by X-ray fluorescence analysis is 0.008 to 0.14 mg.

2. The density of the micropores on the surface of the anodized film is 200 to 2000 pores / μm ２ The on-press development type lithographic printing plate precursor according to claim 1 , 3. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the ratio of the average maximum diameter inside the large diameter portions to the average diameter on the surface of the anodized film of the large diameter portions is 1.2 to 10.

0.

4. The on-press development type lithographic printing plate precursor according to claim 1 or 2, further comprising an undercoat layer disposed between the support and the image recording layer, the undercoat layer comprising a polymer having a support-adsorbing group and a hydrophilic group.

5. The on-press development type lithographic printing plate precursor according to claim 4, wherein the polymer has a support-adsorbing group, a hydrophilic group and a polymerizable group.

6. The on-press development type lithographic printing plate precursor according to claim 4, wherein the hydrophilic group has a zwitterionic structure.

7. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the image recording layer contains an infrared absorbing agent.

8. The on-press development type lithographic printing plate precursor according to claim 7, wherein the infrared absorber has a substituent which is cleaved by infrared light or heat.

9. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the image recording layer contains a borate compound.

10. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the image recording layer contains an acid color former.

11. The on-press development type 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 anodized coating facing the image recording layer by fluorescent X-ray analysis is 0.010 to 0.080 mg.

12. The on-press development type 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 anodized coating facing the image recording layer by fluorescent X-ray analysis is 0.011 to 0.060 mg.

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

14. A printing method comprising: an exposure step of exposing the image recording layer of the on-press development type 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 image recording layer that has been imagewise exposed to light, thereby preparing a lithographic printing plate; and a printing step of carrying out printing using the prepared lithographic printing plate.

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