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

Abstract

The present disclosure provides an on-press-developing-type lithographic printing plate original plate which has, in this order, a support body, an image recording layer, and an outermost layer, wherein the contact angle of water droplets two seconds after drop adhesion by an in-air water drop method on the surface of the outermost layer is greater than 36°. The present disclosure also provides the applications of the same.

Description

[Technical Field]

[0001] The present disclosure relates to an on-press development type lithographic printing plate precursor, a method for preparing a lithographic printing plate, and a lithographic printing method. [Background technology]

[0002] Generally, a lithographic printing plate has an oleophilic image area that accepts ink during the printing process and a hydrophilic non-image area that accepts fountain solution. Lithographic printing is a printing method in which differences in ink adhesion are created on the surface of a lithographic printing plate, ink is applied only to the image area, and then the ink is transferred to a substrate (e.g., paper). In lithographic printing, for example, the oleophilic image area of the lithographic printing plate is used as the ink-receptive area, and the hydrophilic non-image area is used as the fountain solution-receptive area (ink-non-receptive area). To prepare a lithographic printing plate, a lithographic printing plate precursor (PS plate) comprising an oleophilic photosensitive resin layer (image-recording layer) provided on a hydrophilic support has been widely used. Typically, a lithographic printing plate precursor is exposed through an original image such as a lithographic film, and then the image area of the image recording layer is left, while unnecessary image recording layer other than the image area is dissolved and removed with an alkaline developer or organic solvent, exposing the hydrophilic support surface and forming non-image areas, thereby producing a lithographic printing plate.

[0003] With growing concern about the global environment, attention has been focused on environmental issues related to waste liquids that accompany wet processes such as development. In response to these environmental issues, efforts are being made to simplify development or platemaking and eliminate the need for such processes. One simple production method is a method called "on-press development." On-press development is known as a method in which, for example, an exposed lithographic printing plate precursor is mounted on a printing press without undergoing conventional development using a developer, and unnecessary portions of the image-recording layer are removed at an early stage of the printing process (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 243036 Summary of the Invention [Problem to be solved by the invention]

[0005] In printing methods using a lithographic printing plate precursor, it is required to suppress discoloration of the lithographic printing plate precursor due to exposure to ozone generated by light exposure and ozone contained in the atmosphere, for example.

[0006] The present disclosure has been made in light of the above circumstances. An object of one embodiment of the present disclosure is to provide an on-press development type lithographic printing plate precursor that is suppressed from discoloring due to exposure to ozone. Another embodiment of the present disclosure has an object to provide a method for producing a lithographic printing plate using an on-press development type lithographic printing plate precursor that suppresses discoloration due to exposure to ozone. Another embodiment of the present disclosure has an object to provide a lithographic printing method using an on-press development type lithographic printing plate precursor that suppresses discoloration due to exposure to ozone. [Means for solving the problem]

[0007] The present disclosure includes the following aspects. <1> An on-press development type lithographic printing plate precursor having a support, an image recording layer, and an outermost layer in this order, wherein the contact angle of a water droplet on the surface of the outermost layer, measured by a water drop method in the air, 2 seconds after landing is greater than 36°. <2> The contact angle of an oil droplet on the surface of the outermost layer after 2 seconds from the droplet landing using the oil drop method in the air is 20° or less <1> 1. An on-press development type lithographic printing plate precursor according to claim 1. <3> The outermost layer comprises a hydrophobic polymer and a hydrophilic polymer. <1> or <2> 1. An on-press development type lithographic printing plate precursor according to claim 1. <4> The surface area ratio of the hydrophobic polymer on the surface of the outermost layer is 10% or more. <3> 1. An on-press development type lithographic printing plate precursor according to claim 1. <5> The hydrophobic polymer is in the form of particles. <3> or <4> 1. An on-press development type lithographic printing plate precursor according to claim 1. <6> The glass transition temperature of the hydrophobic polymer is 60°C or higher. <3> ~ <5> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <7> The content of the hydrophobic polymer is 1.7 times or more the content of the hydrophilic polymer on a mass basis. <3> ~ <6> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <8> The outermost layer contains a color-changing compound. <1> ~ <7> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <9> 110mJ / cm 2 When exposed to infrared light with a wavelength of 830 nm at an energy density of 1000 kJ / s, the change in brightness ΔL before and after exposure is 2.0 or more. <8> 1. An on-press development type lithographic printing plate precursor according to claim 1. <10> The color-changing compound includes a compound that develops color upon exposure to infrared light. <8> or <9> 1. An on-press development type lithographic printing plate precursor according to claim 1. <11> The color-changing compound includes a decomposable compound that decomposes due to exposure to infrared light. <8> ~ <10> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <12> The color-changing compound is a cyanine dye. <8> ~ <11> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <13> The color-changing compound is a compound represented by the following formula 1-1: <8> ~ <12> 10. An on-press development type lithographic printing plate precursor according to any one of the above items.

[0008] [ka]

[0009] In formula 1-1, R 1 represents a group represented by any one of the following formulas 2 to 4, and R 11 ~R 18 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -SR c , or -NR d R e represents R a ~R eeach independently represents a hydrocarbon group; A1, A2, and a plurality of R 11 ~R 18 may be linked to form a monocycle or polycycle, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, n 11 , and n 12 each independently represents an integer of 0 to 5, and n 11 and n 12 The sum of is 2 or more, and n 13 , and n 14 each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0010] [ka]

[0011] In formulas 2 to 4, R 20 , R 30 , R 41 , and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L. <14> The color-changing compound is a compound represented by the following formula 1-2: <8> ~ <13> 10. An on-press development type lithographic printing plate precursor according to any one of the above items.

[0012] [ka]

[0013] In formula 1-2, R 1 represents a group represented by any one of the following formulas 2 to 4, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d Re represents R 23 , and R 24 are each independently -R a represents R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , or R 23 and R 24 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 , and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion that neutralizes the charge.

[0014] [ka]

[0015] In formulas 2 to 4, R 20 , R 30 , R 41 , and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L. <15> The color-changing compound is a compound represented by any one of the following formulas 1-3 to 1-7: <8> ~ <14> 10. An on-press development type lithographic printing plate precursor according to any one of the above items.

[0016] [ka]

[0017] In formulas 1-3 to 1-7, R 1 represents a group represented by any one of the following formulas 2 to 4, and R 19 ~R 22are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e represents R 23 , and R 24 are each independently -R a represents R 25 , and R 26 are each independently a hydrogen atom, a halogen atom, or -R a represents R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , R 23 and R 24 , or R 25 and R 26 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 , and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion that neutralizes the charge.

[0018] [ka]

[0019] In formulas 2 to 4, R 20 , R 30 , R 41 , and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L. <16> The above W 1 , and the above W 2are each independently an alkyl group having a substituent, and the substituent is a group having at least -(OCH2CH2)-, a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group. <14> or <15> 1. An on-press development type lithographic printing plate precursor according to claim 1. <17> The image recording layer contains at least one selected from the group consisting of an electron-accepting polymerization initiator and an electron-donating polymerization initiator. <1> ~ <16> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <18> The electron-accepting polymerization initiator contains a compound represented by the following formula (II): <17> 1. An on-press development type lithographic printing plate precursor according to claim 1.

[0020] [ka]

[0021] In formula (II), X represents a halogen atom, and R 3 represents an aryl group. <19> The image recording layer contains a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form an ion pair. <1> ~ <16> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <20> the image recording layer contains an infrared absorbing agent, and the value of the HOMO energy level of the infrared absorbing agent minus the HOMO energy level of the electron-donating polymerization initiator is 0.70 eV or less; <17> ~ <19> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <21> the image recording layer contains an infrared absorber, and the value of the LUMO energy level of the electron-accepting polymerization initiator minus the LUMO energy level of the infrared absorber is 1.00 eV or less; <17> ~ <20> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <22> The image recording layer contains a polymerizable compound having seven or more polymerizable groups. <1> ~ <21> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <23> The image recording layer contains a polymerizable compound having 10 or more polymerizable groups. <1> ~ <22> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <24> The support has an aluminum plate and an anodized aluminum film disposed on the aluminum plate, the anodized aluminum film being located closer to the image recording layer than the aluminum plate, the anodized aluminum film having micropores extending in the depth direction from the surface on the image recording layer side, and the average diameter of the micropores on the surface of the anodized aluminum film being greater than 10 nm and not greater than 100 nm. <1> ~ <23> 10. An on-press development type lithographic printing plate precursor according to any one of the above items. <25> The micropores have large-diameter pores extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm, and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend from the communicating positions with the large-diameter pores to a depth of 20 nm to 2,000 nm, the average diameter of the large-diameter pores on the surface of the anodized film being 15 nm to 100 nm, and the average diameter of the small-diameter pores at the communicating positions being 13 nm or less. <24> 1. An on-press development type lithographic printing plate precursor according to claim 1. <26> <1> ~ <25> and a step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas. <27> <1> ~ <25> a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of the above items 1 to 10; a step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas to prepare a lithographic printing plate; and a step of printing with the obtained lithographic printing plate. [Effects of the Invention]

[0022] According to one embodiment of the present disclosure, there is provided an on-press development type lithographic printing plate precursor that is inhibited from discoloring due to exposure to ozone. According to another embodiment of the present disclosure, there is provided a method for producing a lithographic printing plate using an on-press development type lithographic printing plate precursor that is inhibited from discoloring due to exposure to ozone. According to another embodiment of the present disclosure, there is provided a lithographic printing method using an on-press development type lithographic printing plate precursor that is inhibited from discoloring due to exposure to ozone. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic cross-sectional view of a support according to one embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of a support according to another embodiment. [Figure 3] FIG. 3 is a schematic diagram showing an example of an anodizing treatment device. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In the present disclosure, the use of "to" indicating a range of values means that the values before and after it are included as the lower limit and upper limit. With respect to the numerical ranges described stepwise in the present disclosure, the upper or lower limit value defining a certain numerical range may be replaced with the upper or lower limit value of another numerical range. In addition, the upper or lower limit value of a numerical range in the present disclosure may be replaced with a value shown in an example. In the present disclosure, when a group (atomic group) is represented without specifying whether it is substituted or unsubstituted, it encompasses both a group having no substituent and a group having a substituent. For example, the term "alkyl group" encompasses not only an alkyl group having no substituent (i.e., an unsubstituted alkyl group) but also an alkyl group having a substituent (a substituted alkyl group). In the present disclosure, "(meth)acrylic" is a term used as a concept that encompasses both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept that encompasses both acryloyl and methacryloyl. With respect to the term "process" in the present disclosure, not only independent processes but also processes that cannot be clearly distinguished from other processes are included in the term as long as the intended purpose of the process is achieved. In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in this disclosure are molecular weights determined by gel permeation chromatography (GPC) using columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation), detection with a differential refractometer using THF (tetrahydrofuran) as a solvent, and conversion using polystyrene as a standard substance. In the present disclosure, the term "lithographic printing plate precursor" encompasses not only lithographic printing plate precursors but also disposable plate precursors. In this disclosure, the term "lithographic printing plate" includes not only a lithographic printing plate prepared by subjecting a lithographic printing plate precursor to operations such as exposure and development as necessary, but also a throwaway plate. In the case of a throwaway plate precursor, the operations of exposure and development are not necessarily required. Note that a throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when printing a portion of a page in monochrome or two colors, for example, in color newspaper printing. In this disclosure, "printing durability" refers to the number of printable sheets of a lithographic printing plate. Printing durability when ultraviolet-curable ink (UV ink) is used as the ink during printing is also referred to as "UV printing durability."

[0025] <On-press development type lithographic printing plate original plate> An on-press development type lithographic printing plate precursor according to one embodiment of the present disclosure has a support, an image recording layer, and an outermost layer in this order, and the contact angle of a water droplet on the surface of the outermost layer 2 seconds after landing by the airborne water drop method is greater than 36°. According to one embodiment of the present disclosure, there is provided an on-press development type lithographic printing plate precursor that suppresses discoloration due to exposure to ozone (hereinafter also referred to as "ozone discoloration").

[0026] The reason why the on-press development type lithographic printing plate precursor according to one embodiment of the present disclosure exhibits the above-described effects is presumed to be as follows. In the on-press development type lithographic printing plate precursor according to one embodiment of the present disclosure, the contact angle of a water droplet on the surface of the outermost layer 2 seconds after landing by the airborne water drop method is greater than 36°. The above-described characteristics improve the hydrophobicity of the surface of the outermost layer, reducing the affinity of the outermost layer for ozone. Therefore, one embodiment of the present disclosure provides an on-press development type lithographic printing plate precursor that suppresses discoloration due to ozone exposure.

[0027] Hereinafter, the on-press development type lithographic printing plate precursor will be specifically described. Hereinafter, the "on-press development type lithographic printing plate precursor" may be simply referred to as the "lithographic printing plate precursor."

[0028] <<Outermost layer>> The on-press developable lithographic printing plate precursor according to an embodiment of the present disclosure has an outermost layer. The outermost layer may function, for example, as a protective layer. The outermost layer may have, for example, a function to suppress an image formation inhibiting reaction by blocking oxygen, a function to prevent scratches on the image recording layer, and a function to prevent ablation during exposure to a high-intensity laser. Layers having the above-described properties are described, for example, in U.S. Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729.

[0029] [Contact angle] The contact angle of a water droplet on the surface of the outermost layer 2 seconds after landing by the airborne water drop method (hereinafter simply referred to as the "contact angle of the water droplet") is greater than 36°. A contact angle of the water droplet greater than 36° can suppress ozone discoloration. From the viewpoint of suppressing ozone discoloration and suppressing the generation of development residue, the contact angle of the water droplet is preferably 40° or more, more preferably 50° or more, even more preferably 60° or more, and particularly preferably 70° or more. There is no upper limit to the contact angle of the water droplet. The contact angle of the water droplet may be, for example, 80° or less, or 70° or less. In the present disclosure, unless otherwise specified, the "surface of the outermost layer" means the surface of the outermost layer facing away from the surface facing the image recording layer. In the present disclosure, the contact angle of a water droplet is measured using a fully automatic contact angle meter (for example, DM-501 manufactured by Kyowa Interface Science Co., Ltd.) as a measuring device, and is the contact angle of a water droplet dropped on the surface of a measurement object at 25° C. (contact angle 2 seconds after landing). The contact angle is measured at three or more locations on the surface of the same measurement object, and the measured values are then averaged.

[0030] The contact angle of an oil droplet on the surface of the outermost layer 2 seconds after landing by the oil drop method (hereinafter simply referred to as the "oil drop contact angle") is preferably 20° or less, more preferably 15° or less, and particularly preferably 12° or less, from the viewpoints of suppressing ozone discoloration and suppressing the generation of development residue. There is no lower limit for the oil drop contact angle. The oil drop contact angle may, for example, be greater than 0°. From the viewpoint of on-press developability, the oil drop contact angle is preferably 3° or more, more preferably 5° or more, and particularly preferably 8° or more. In the present disclosure, the oil drop contact angle is measured as the contact angle of linseed oil dropped on the surface of a measurement object at 25°C (contact angle 2 seconds after landing) using a fully automatic contact angle meter (e.g., DM-501 manufactured by Kyowa Interface Science Co., Ltd.). Contact angles are measured at three or more locations on the surface of the same measurement object, and the average of the measured values is calculated.

[0031] The contact angles of water droplets and oil droplets on the surface of the outermost layer can be adjusted, for example, by the composition of the outermost layer. For example, the contact angles of water droplets and oil droplets can be adjusted by using a hydrophobic polymer or a hydrophilic polymer, as described below, and by adjusting the content of the hydrophobic polymer or the hydrophilic polymer, as described below. However, the method for adjusting the contact angle is not limited to the above-mentioned method. Known methods may be used to adjust the contact angle.

[0032] [polymer] The outermost layer preferably contains a polymer. Examples of the polymer include a hydrophobic polymer and a hydrophilic polymer. The outermost layer preferably contains a hydrophobic polymer, and more preferably contains a hydrophobic polymer and a hydrophilic polymer. The hydrophobic polymer and the hydrophilic polymer will be specifically described below.

[0033] (hydrophobic polymer) The outermost layer preferably contains a hydrophobic polymer from the viewpoints of suppressing ozone discoloration and suppressing the generation of development residue. In the present disclosure, the term "hydrophobic polymer" refers to a polymer having a solubility of 5% by mass or less in water at 25°C.

[0034] Examples of hydrophobic polymers include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly(meth)acrylic acid alkyl esters (e.g., poly(methyl(meth)acrylate), poly(ethyl(meth)acrylate), and poly(butyl(meth)acrylate)), fluorine atom-containing (meth)acrylic resins, and copolymers of monomers that are raw materials for these polymers. The hydrophobic polymer preferably includes a styrene-acrylic copolymer.

[0035] From the viewpoint of suppressing ozone discoloration and suppressing generation of development residue, the glass transition temperature (Tg) of the hydrophobic polymer is preferably 30°C or higher, more preferably 60°C or higher, and particularly preferably 70°C or higher. There is no upper limit to the glass transition temperature of the hydrophobic polymer. The glass transition temperature of the hydrophobic polymer may be 150°C or lower, or 120°C or lower.

[0036] The glass transition temperature of a polymer is measured using differential scanning calorimetry (DSC). The specific measurement method is based on the method described in "JIS K 7121 (1987)" or "JIS K 6240 (2011)." An appropriate JIS standard is selected depending on the polymer composition. The glass transition temperature in this disclosure is the extrapolated glass transition onset temperature (hereinafter also referred to as "Tig"). The method for measuring the glass transition temperature is described in more detail below. To measure the glass transition temperature, the apparatus is held at a temperature approximately 50°C lower than the expected glass transition temperature of the polymer until the apparatus stabilizes, and then heated at a heating rate of 20°C / min to a temperature approximately 30°C higher than the temperature at which the glass transition ends, thereby creating a differential thermal analysis (DTA) curve or DSC curve. The extrapolated glass transition onset temperature (Tig), i.e., the glass transition temperature (Tg) in the present disclosure, is determined as the temperature at the intersection of a straight line extending the low-temperature baseline of a DTA curve or DSC curve toward a higher temperature and a tangent drawn at the point where the gradient of the curve in the stepwise change portion of the glass transition is maximum.

[0037] The hydrophobic polymer is preferably in the form of particles. The particulate form of the hydrophobic polymer can further improve the hydrophobicity of the surface of the outermost layer. For example, a particulate hydrophobic polymer can form a sea-island structure on the surface of the outermost layer, with the hydrophobic polymer forming island regions. Such a sea-island structure can contribute to improving the hydrophobicity. In the present disclosure, a hydrophobic polymer whose outline is confirmed by surface observation of the outermost layer (i.e., a planar view) is considered to be in the form of a particle. The outline shape of the hydrophobic polymer confirmed by surface observation of the outermost layer is not limited to a perfect circle, and may be, for example, an ellipse, a polygon, or an irregular shape. When observing the surface of the outermost layer, the observation method used for measuring the "occupied area ratio of the hydrophobic polymer" described below may be used, if necessary.

[0038] From the viewpoints of suppressing ozone discoloration and suppressing the generation of development residue, the area occupied by the hydrophobic polymer on the surface of the outermost layer is preferably 5% or more, more preferably 10% or more, even more preferably 20% or more, particularly preferably 50% or more, and most preferably 60% or more. The area occupied by the hydrophobic polymer on the surface of the outermost layer may be 70% or more, or 80% or more. There is no upper limit to the area occupied by the hydrophobic polymer on the surface of the outermost layer. The area occupied by the hydrophobic polymer on the surface of the outermost layer may be less than 100%, 95% or less, 90% or less, or 85% or less.

[0039] The area ratio of the hydrophobic polymer on the surface of the outermost layer is measured using the following method. After applying a 3-nm carbon film or a 3-nm Pt-Pd film as a conductive treatment to the surface of the object to be measured, backscattered electron images are observed using a Hitachi High-Technologies Corporation SU8010 FE-SEM at an accelerating voltage of 5 kV to 10 kV. Images are taken at three locations at 1,000 to 10,000x magnification (adjusted to the desired magnification depending on the size of the hydrophobic polymer being observed). Using image processing software (e.g., ImageJ), binarization is performed using the contrast difference between the hydrophobic polymer (e.g., convex portions) and its surroundings to calculate the area ratio of the hydrophobic polymer. The area ratio of the hydrophobic polymer is calculated by dividing the "area of the hydrophobic polymer" by the "area of the field of view (the sum of the area of the hydrophobic polymer and the area of the region other than the hydrophobic polymer)." However, when the hydrophobic polymer cannot be observed in the image obtained by the above method, the content (unit: mass %) of the hydrophobic polymer contained in the outermost layer is taken as the occupied area ratio of the hydrophobic polymer.

[0040] The outermost layer may contain one or more hydrophobic polymers.

[0041] From the viewpoints of suppressing ozone discoloration and suppressing the generation of development residue, the content of the hydrophobic polymer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, particularly preferably 50% by mass or more, and most preferably 60% by mass or more, relative to the total mass of the outermost layer. The content of the hydrophobic polymer may be 70% by mass or more, or 80% by mass or more, relative to the total mass of the outermost layer. There is no upper limit for the content of the hydrophobic polymer. The content of the hydrophobic polymer may be less than 100% by mass, 95% by mass or less, 90% by mass or less, or 85% by mass or less, relative to the total mass of the outermost layer.

[0042] When the outermost layer contains a hydrophobic polymer and a hydrophilic polymer, the content of the hydrophobic polymer is preferably greater than the content of the hydrophilic polymer. Having a higher content of the hydrophobic polymer than the content of the hydrophilic polymer can further suppress ozone discoloration. It can also further suppress the generation of development residue. Specifically, the content of the hydrophobic polymer is preferably 1.7 times or more, more preferably 2.9 times or more, and particularly preferably 3.2 times or more, of the content of the hydrophilic polymer, by mass. There is no upper limit to the ratio of the content of the hydrophobic polymer to the content of the hydrophilic polymer. The content of the hydrophobic polymer may be 10.0 times or less, by mass, of the content of the hydrophilic polymer.

[0043] (hydrophilic polymer) From the viewpoint of on-press developability, the outermost layer preferably contains a hydrophilic polymer. In the present disclosure, the term "hydrophilic polymer" refers to a polymer having a solubility in water at 25°C of more than 5% by mass.

[0044] Examples of hydrophilic polymers include polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, cellulose derivatives, polyethylene glycol, and poly(meth)acrylonitrile. Acid-modified polyvinyl alcohols having carboxyl or sulfo groups are preferably used as modified polyvinyl alcohols. Specific examples include the modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137. Examples of cellulose derivatives include methyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.

[0045] In one embodiment, the hydrophilic polymer preferably includes at least one selected from the group consisting of modified polyvinyl alcohol and cellulose derivatives.

[0046] In one embodiment, the hydrophilic polymer preferably contains polyvinyl alcohol. Among polyvinyl alcohols, polyvinyl alcohols having a degree of saponification of 50% or more are more preferred. The degree of saponification is preferably 60% or more, more preferably 70% or more, and particularly preferably 85% or more. There is no upper limit to the degree of saponification. The degree of saponification may be 100% or less. The degree of saponification is measured according to the method described in "JIS K 6726:1994."

[0047] In one embodiment, the hydrophilic polymer preferably includes polyvinylpyrrolidone. It is also preferable to use a combination of polyvinyl alcohol and polyvinylpyrrolidone as the hydrophilic polymer.

[0048] The outermost layer may contain one or more hydrophilic polymers.

[0049] The content of the hydrophilic polymer is preferably 10% by mass or more relative to the total mass of the outermost layer from the viewpoint of on-machine developability, and is preferably 90% by mass or less relative to the total mass of the outermost layer from the viewpoint of suppressing ozone discoloration and suppressing generation of development residue.

[0050] [Color-changing compounds] The outermost layer preferably contains a color-changing compound. In the present disclosure, the term "color-changing compound" refers to a compound whose absorption in the visible light region (wavelength: 400 nm or more and less than 750 nm) changes upon exposure to infrared light. In other words, in the present disclosure, "color change" refers to a change in absorption in the visible light region (wavelength: 400 nm or more and less than 750 nm) upon exposure to infrared light. Examples of color-changing compounds include (1) compounds whose absorption in the visible light region increases upon exposure to infrared light compared to before exposure to infrared light, (2) compounds whose absorption in the visible light region changes upon exposure to infrared light, and (3) compounds whose absorption in the visible light region changes away upon exposure to infrared light. In the present disclosure, "infrared" refers to light in a wavelength region of 750 nm to 1 mm, preferably light in a wavelength region of 750 nm to 1,400 nm.

[0051] The color-changing compound preferably contains a compound that develops color upon exposure to infrared light. The color-changing compound preferably contains a decomposable compound that decomposes upon exposure to infrared light, and more preferably contains a decomposable compound that decomposes due to heat, electron transfer, or both, resulting from infrared exposure. Specifically, the color-changing compound is preferably a compound that decomposes upon exposure to infrared light (more preferably decomposes due to heat, electron transfer, or both, resulting from infrared exposure), and exhibits increased absorption in the visible light region or shorter wavelength absorption than before infrared exposure, resulting in absorption in the visible light region. Here, "decomposes due to electron transfer" means that electrons excited from the HOMO (highest occupied molecular orbital) of the color-changing compound to the LUMO (lowest unoccupied molecular orbital) upon infrared exposure undergo intramolecular electron transfer to an electron-accepting group (a group with a potential close to that of the LUMO) within the molecule, resulting in decomposition.

[0052] The decomposable compound may be, for example, a compound that absorbs and decomposes at least a portion of light in the infrared wavelength range (750 nm to 1 mm, preferably 750 nm to 1,400 nm). The decomposable compound is preferably a compound that has a maximum absorption in the wavelength range of 750 nm to 1,400 nm. Specifically, the decomposable compound is preferably a compound that decomposes upon exposure to infrared light to produce a compound that has a maximum absorption wavelength in the wavelength range of 500 nm to 600 nm.

[0053] Preferred examples of the color-changing compound include compounds represented by the following formulas: 1, 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, and 1-7.

[0054] (Compound represented by formula 1) The color-changing compound preferably includes a compound represented by the following formula 1:

[0055] [ka]

[0056] In Formula 1, R1 and R2 each independently represent a hydrogen atom or an alkyl group, and R1 and R2 may be bonded to each other to form a ring; R3 to R6 each independently represent a hydrogen atom or an alkyl group; R7 and R8 each independently represent an alkyl group or an aryl group; Y1 and Y2 each independently represent an oxygen atom, a sulfur atom, -NR0-, or a dialkylmethylene group; R0 represents a hydrogen atom, an alkyl group, or an aryl group; Ar1 and Ar2 each independently represent a group forming a benzene ring or a naphthalene ring which may have a group represented by Formula 2 described below; and A1 is -NR9R 10 , -X1-L1 or a group represented by formula 2 described below, R9 and R 10 each independently represents an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group; X1 represents an oxygen atom or a sulfur atom; L1 represents a hydrocarbon group, a heteroaryl group, or a group whose bond to X1 is cleaved by heat or exposure to infrared light; Za represents a counter ion that neutralizes the charge; and at least one of Ar1 and Ar2 has a group represented by the following formula 2: -X: expression 2 In Formula 2, X represents a halogen atom, -C(=O)-X2-R 11 , -C(=O)-NR 12 R 13 , -OC(=O)-R 14 , -CN, -SO2NR 15 R 16 or a perfluoroalkyl group, X2 represents a single bond or an oxygen atom, R 11 and R 14 each independently represents an alkyl group or an aryl group, R 12 , R 13 , R 15 and R 16 each independently represents a hydrogen atom, an alkyl group, or an aryl group.

[0057] Ar1 and Ar2 each independently represent a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent other than -X. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, and a combination thereof, but an alkyl group is preferred. In addition, in Formula 1, at least one of Ar1 and Ar2 has a group represented by the above Formula 2, and from the viewpoints of printing durability and visibility, it is preferable that both Ar1 and Ar2 have a group represented by the above Formula 2.

[0058] X in formula 2 is a halogen atom, -C(=O)-X2-R 11 , -C(=O)-NR 12 R 13 , -OC(=O)-R 14 , -CN, -SO2NR 15 R 16 or a perfluoroalkyl group, and from the viewpoints of printing durability, visibility, and stability over time, a halogen atom, —C(═O)—X2—R 11 , -C(=O)-NR 12 R 13 , -OC(=O)-R 14 , CN, or -SO2NR 15 R 16 is preferably a halogen atom, —C(═O)—OR 11 , -C(=O)-NR 12 R 13 , or -OC(=O)-R 14 is preferably a halogen atom, —C(═O)—OR 11 , or -OC(=O)-R 14 It is more preferable that the group is a fluorine atom, a chlorine atom, a bromine atom, or —C(═O)OR 17 is particularly preferred, and a chlorine atom or a bromine atom is most preferred.

[0059] X2 represents a single bond or an oxygen atom, and is preferably an oxygen atom. R11 and R 14 each independently represents an alkyl group or an aryl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. R 12 , R 13 , R 15 and R 16 each independently represents a hydrogen atom, an alkyl group, or an aryl group, and is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and even more preferably an alkyl group having 1 to 12 carbon atoms. R 17 represents an alkyl group or an aryl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms.

[0060] A1 is -NR9R 10 , -X1-L1 or -X, and from the viewpoint of printing durability, visibility and stability over time, -NR9R 10 or -X1-L1, and -NR 18 R 19 , -SR 20 It is more preferable that: Furthermore, from the viewpoints of UV plate skip suppression, GLV suitability, and UV printing durability, A1 is preferably -X, more preferably a halogen atom, still more preferably a chlorine atom or a bromine atom, and particularly preferably a chlorine atom. R9 and R 10 each independently represents an alkyl group, an aryl group, an alkoxycarbonyl group, or an arylsulfonyl group, and is preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms. X1 represents an oxygen atom or a sulfur atom, and when L1 is a hydrocarbon group or a heteroaryl group, it is preferably a sulfur atom, and L1 is preferably a group whose bond to X1 is cleaved by heat or exposure to infrared light. L1 represents a hydrocarbon group, a heteroaryl group, or a group whose bond to X1 is cleaved by heat or infrared exposure. From the viewpoint of printing durability, L1 is preferably a hydrocarbon group or a heteroaryl group, more preferably an aryl group or a heteroaryl group, and even more preferably a heteroaryl group. Furthermore, from the viewpoint of visibility and prevention of fading over time, L1 is preferably a group in which the bond to X1 is cleaved by heat or exposure to infrared light. The group whose bond to X1 is cleaved by heat or exposure to infrared rays will be described later. R 18 and R 19 each independently represents an aryl group, preferably an aryl group having 6 to 20 carbon atoms, more preferably a phenyl group. R 20 represents a hydrocarbon group or a heteroaryl group, preferably an aryl group or a heteroaryl group, and more preferably a heteroaryl group.

[0061] L1 and R 20 Preferred examples of the heteroaryl group in the formula include the following groups:

[0062] [ka]

[0063] R1~R 10 The alkyl group in R0 is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and even more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a ring structure. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group. Among these alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is particularly preferred.

[0064] The alkyl group may have a substituent, such as 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, or a combination thereof.

[0065] R9, R 10 , R 18 , R 19 The aryl group in R0 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, such as 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, or a combination thereof. Specific examples of the aryl group include a phenyl group, a naphthyl group, a p-tolyl group, a p-chlorophenyl group, a p-fluorophenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, a p-methylthiophenyl group, and a p-phenylthiophenyl group. Of these aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, or a naphthyl group is preferred.

[0066] It is preferred that R1 and R2 are linked to form a ring. When R1 and R2 are bonded to form a ring, the ring is preferably a 5- or 6-membered ring, more preferably a 6-membered ring. In addition, the ring formed by bonding R1 and R2 is preferably a hydrocarbon ring which may have an ethylenically unsaturated bond.

[0067] Y1 and Y2 each independently represent an oxygen atom, a sulfur atom, -NR0- or a dialkylmethylene group, preferably -NR0- or a dialkylmethylene group, and more preferably a dialkylmethylene group. R0 represents a hydrogen atom, an alkyl group or an aryl group, and is preferably an alkyl group.

[0068] It is preferred that R7 and R8 are the same group. Furthermore, R7 and R8 are each preferably a linear alkyl group or an alkyl group having a terminal sulfonate group, and 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 the cation on the nitrogen atom in formula 1, or may be an alkali metal cation or an alkaline earth metal cation. Furthermore, from the viewpoint of making the compound represented by formula 1 water-soluble, R7 and R8 are each independently preferably an alkyl group having an anionic structure, more preferably an alkyl group having a carboxylate group or a sulfonate group, and even more preferably an alkyl group having a sulfonate group at the terminal. Furthermore, in order to lengthen the maximum absorption wavelength of the compound represented by Formula 1 and from the viewpoints of visibility and printing durability of the lithographic printing plate, R7 and R8 are each independently preferably an alkyl group having an aromatic ring, more preferably an alkyl group having an aromatic ring at the terminal, and particularly preferably a 2-phenylethyl group, a 2-naphthalenylethyl group, or a 2-(9-anthracenyl)ethyl group.

[0069] R3 to R6 each independently represent a hydrogen atom or an alkyl group, and are preferably a hydrogen atom.

[0070] Furthermore, from the viewpoints of stability over time, UV plate skip suppression, GLV suitability, and UV printing durability, the compound represented by formula 1 preferably has one or more halogen atoms, more preferably at least one selected from the group consisting of A1, Ar1, and Ar2 has one or more halogen atoms, and particularly preferably A1, Ar1, and Ar2 each have one or more halogen atoms. Furthermore, from the viewpoints of stability over time, UV plate skip suppression, GLV suitability, and UV printing durability, the compound represented by Formula 1 more preferably has two or more halogen atoms, still more preferably has three or more halogen atoms, and particularly preferably has three to six halogen atoms. The halogen atom is preferably a chlorine atom or a bromine atom. Furthermore, from the viewpoints of stability over time, UV plate skip suppression, GLV suitability, and UV printing durability, the compound represented by formula 1 preferably has a halogen atom in at least one of Ar1 and Ar2, more preferably has a chlorine atom or a bromine atom in at least one of Ar1 and Ar2, and particularly preferably has a bromine atom in at least one of Ar1 and Ar2.

[0071] Za represents a counter ion that neutralizes the charge, and examples of an anionic species include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a perchlorate ion, a sulfonamide anion, and a sulfonimide anion. Examples of a cationic species include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, or a sulfonium ion, more preferably a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion, still more preferably a sodium ion, a potassium ion, or an ammonium ion, and particularly preferably a sodium ion, a potassium ion, or a trialkylammonium ion. Among these, from the viewpoints of printing durability and visibility, Za is preferably an organic anion containing a carbon atom, more preferably a sulfonate ion, a carboxylate ion, a sulfonamide anion, or a sulfonimide anion, still more preferably a sulfonamide anion or a sulfonimide anion, and particularly preferably a sulfonimide anion. R1 to R8, R0, A1, Ar1, Ar2, Y1, and Y2 may have an anionic structure or a cationic structure. When all of R1 to R8, R0, A1, Ar1, Ar2, Y1, and Y2 are electrically neutral groups, Za is a monovalent counter anion. However, when, for example, R1 to R8, R0, A1, Ar1, Ar2, Y1, and Y2 have two or more anionic structures, Za can also be a counter cation. In addition, in formula 1, if the moieties other than Za are electrically neutral, Za may be omitted.

[0072] The sulfonamide anion is preferably an arylsulfonamide anion. The sulfonimide anion is preferably a bisarylsulfonimide anion. Specific examples of sulfonamide anions or sulfonimide anions are shown below, but the present disclosure is not limited to these. In the following specific examples, Ph represents a phenyl group, Me represents a methyl group, and Et represents an ethyl group.

[0073] [ka]

[0074] From the viewpoint of visibility, the group whose bond to X1 is cleaved by exposure to heat or infrared rays 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).

[0075] [ka]

[0076] In formulas (1-1) to (1-7), ● represents a bonding site with X1 in formula 1, and R 10 are each independently a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, -OR 14 , -NR 15 R 16 or -SR 17 represents R 11 each independently represents a hydrogen atom, an alkyl group, or an aryl group; R 12 is an aryl group, -OR 14 , -NR 15 R 16 , -SR 17 , -C(=O)R 18 , -OC(=O)R 18 or a halogen atom, R 13 represents an aryl group, an alkenyl group, an alkoxy group, or an onium group; R 14 ~R 17 each independently represents a hydrogen atom, an alkyl group, or an aryl group; R 18 are each independently an alkyl group, an aryl group, or -OR 14 , -NR 15 R 16 or -SR 17 represents Z 1 represents a counter ion that neutralizes the charge.

[0077] R 10 , R 11and R 14 ~R 18 In a preferred embodiment, when R is an alkyl group, 2 ~R 9 and R 0 The preferred embodiments of the alkyl group are the same as those in the above. R 10 and R 13 The alkenyl group in the formula (I) preferably has 1 to 30 carbon atoms, more preferably 1 to 15 carbon atoms, and even more preferably 1 to 10 carbon atoms. R 10 ~R 18 In a preferred embodiment, when R is an aryl group, 0 The preferred embodiments are the same as those of the aryl group in the above.

[0078] From the viewpoint of visibility, R in Equation (1-1) 10 represents an alkyl group, an alkenyl group, an aryl group, -OR 14 , -NR 15 R 16 or -SR 17 is preferably an alkyl group, -OR 14 , -NR 15 R 16 or -SR 17 More preferably, it is an alkyl group or -OR 14 More preferably, -OR 14 It is particularly preferred that: In addition, R in formula (1-1) 10 When is an alkyl group, the alkyl group is preferably an alkyl group having an arylthio group or an alkyloxycarbonyl group at the α-position. R in formula (1-1) 10 -OR 14 If R 14 is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, further preferably an isopropyl group or a t-butyl group, and particularly preferably a t-butyl group.

[0079] From the viewpoint of visibility, R in Equation (1-2) 11is preferably a hydrogen atom. In addition, from the viewpoint of visibility, R in formula (1-2) 12 is -C(=O)OR 14 , -OC(=O)OR 14 or a halogen atom, preferably —C(═O)OR 14 or -OC(=O)OR 14 It is more preferable that R in formula (1-2) is 12 -C(=O)OR 14 or -OC(=O)OR 14 If R 14 is preferably an alkyl group.

[0080] From the viewpoint of visibility, R in Equation (1-3) 11 are each independently preferably a hydrogen atom or an alkyl group, and at least one R 11 However, it is more preferably an alkyl group. Also, R 11 The alkyl group in the formula (I) is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 3 to 10 carbon atoms. Furthermore, R 11 The alkyl group in is preferably a branched alkyl group or a cycloalkyl group, more preferably a secondary or tertiary alkyl group or a cycloalkyl group, and further preferably an isopropyl group, a cyclopentyl group, a cyclohexyl group, or a t-butyl group. In addition, from the viewpoint of visibility, R in Equation (1-3) 13 is preferably an aryl group, an alkoxy group or an onium group, more preferably a p-dimethylaminophenyl group or a pyridinium group, and even more preferably a pyridinium group. R 13Examples of the onium group in (I) include a pyridinium group, an ammonium group, and a sulfonium group. The onium 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 sulfo group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a combination thereof, with an alkyl group, an aryl group, and a combination thereof being preferred. Among these, a pyridinium group is preferred, and examples thereof include an N-alkyl-3-pyridinium group, an N-benzyl-3-pyridinium group, an N-(alkoxypolyalkyleneoxyalkyl)-3-pyridinium group, an N-alkoxycarbonylmethyl-3-pyridinium group, an N-alkyl-4-pyridinium group, an N-benzyl-4-pyridinium group, an N-(alkoxypolyalkyleneoxyalkyl)-4-pyridinium group, and an N-alkoxycarbonylmethyl-4-pyridinium group. An N-methyl-3-pyridinium group, an N-octyl-3-pyridinium group, an N-methyl-4-pyridinium group, or an N-octyl-4-pyridinium group is particularly preferred, and an N-octyl-3-pyridinium group or an N-octyl-4-pyridinium group is most preferred. Also, R 13 is a pyridinium group, examples of the counter anion include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, a perchlorate ion, and the like, with a p-toluenesulfonate ion or a hexafluorophosphate ion being preferred.

[0081] From the viewpoint of visibility, R in Equation (1-4) 10 is preferably an alkyl group or an aryl group, and two R 10 It is more preferable that one of them is an alkyl group and the other is an aryl group. From the viewpoint of visibility, R in Equation (1-5)10 is preferably an alkyl group or an aryl group, more preferably an aryl group, and even more preferably a p-methylphenyl group. From the viewpoint of visibility, R in Equation (1-6) 10 are each independently preferably an alkyl group or an aryl group, more preferably a methyl group or a phenyl group. From the viewpoint of visibility, Z in Eq. (1-7) 1 is any counter ion that neutralizes the charge, and the compound as a whole may be included in the above Za. Z 1 is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a p-toluenesulfonate ion or a hexafluorophosphate ion.

[0082] Furthermore, the group whose bond to X1 is cleaved by heat or infrared exposure is particularly preferably a group represented by formula (1-8).

[0083] [ka]

[0084] In formula (1-8), ● represents a bonding site with X1 in formula 1, and R 19 and R 20 each independently represents an alkyl group, and Za' represents a counter ion that neutralizes the charge.

[0085] The pyridinium ring and R in formula (1-8) 20 The bonding position to the hydrocarbon group containing the following is preferably the 3rd or 4th position of the pyridinium ring, more preferably the 4th position of the pyridinium ring. R 19 and R 20 The alkyl group in the formula (I) may be linear, branched, or have a ring structure. The alkyl group may have a substituent, and preferred examples of the substituent include an alkoxy group and a terminal alkoxypolyalkyleneoxy group. R 19 is preferably an alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, even more preferably a linear alkyl group having 1 to 8 carbon atoms, and particularly preferably a methyl group or an n-octyl group. R 20 is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 8 carbon atoms, further preferably an isopropyl group or a t-butyl group, and particularly preferably an isopropyl group. Za' may be any counter ion that neutralizes the charge, and the entire compound may be included in the above Za. Za' is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a p-toluenesulfonate ion or a hexafluorophosphate ion.

[0086] The decomposable compound, which is a kind of color-changing compound, is preferably a cyanine dye from the viewpoint of enhancing the visibility of the exposed area, and is preferably a compound having a group that decomposes upon exposure to infrared light (specifically, R 1 ) is more preferably a cyanine dye having the formula

[0087] (Compound represented by formula 1-1) The decomposable compound, which is a type of color-changing compound, is preferably a compound represented by the following formula 1-1, from the viewpoint of improving the visibility of the exposed area.

[0088] [ka]

[0089] In formula 1-1, R 1represents a group represented by any one of the following formulas 2 to 4, and R 11 ~R 18 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -SR c , or -NR d R e represents R a ~R e each independently represents a hydrocarbon group; A1, A2, and a plurality of R 11 ~R 18 may be linked to form a monocycle or polycycle, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, n 11 , and n 12 each independently represents an integer of 0 to 5, and n 11 and n 12 The sum of is 2 or more, and n 13 , and n 14 each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0090] [ka]

[0091] In formulas 2 to 4, R 20 , R 30 , R 41 , and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L.

[0092] When the compound of formula 1-1 is exposed to infrared light, R 1 The -L bond is cleaved and L is =O, =S, or =NR 10 Through the process described above, the compound represented by formula 1-1 changes color.

[0093] In Formula 1-1, R 1 represents a group represented by any one of the above formulas 2 to 4. The group represented by formula 2, the group represented by formula 3, and the group represented by formula 4 will be explained below.

[0094] In formula 2, R 20 represents an alkyl group or an aryl group, and the wavy line represents the bonding site to L.

[0095] R 20 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and particularly preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear or branched. The alkyl group may have a ring structure.

[0096] R 20 The aryl group represented by the formula (I) is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and particularly preferably an aryl group having 6 to 12 carbon atoms. 20 is preferably an alkyl group from the viewpoint of color development properties.

[0097] From the viewpoint of decomposability and color development, R 20 The alkyl group represented by R is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. 20 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0098] Specific examples of the group represented by formula 2 are shown below. However, the group represented by formula 2 is not limited to the specific examples shown below. In the following structural formula, "●" represents the bonding site with L in formula 1-1.

[0099] [ka]

[0100] In formula 3, R 30 represents an alkyl group or an aryl group, and the wavy line represents the bonding site with L. 30 The alkyl group and aryl group represented by R in Formula 2 are 20 The meanings and preferred embodiments are the same as those of the alkyl group and aryl group represented by the following formula:

[0101] From the viewpoint of decomposability and color development, R 30 The alkyl group represented by R is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. 30 The alkyl group represented by R is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, and is particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group. Furthermore, from the viewpoints of decomposability and color development, 30 The alkyl group represented by the formula (I) is preferably a substituted alkyl group, more preferably a fluoro-substituted alkyl group, further preferably a perfluoroalkyl group, and particularly preferably a trifluoromethyl group.

[0102] From the viewpoint of decomposability and color development, R 30 The aryl group represented by the formula (I) is preferably a substituted aryl group. Examples of the substituent in the substituted aryl group include an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms) and an alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms).

[0103] Specific examples of the group represented by formula 3 are shown below. However, the group represented by formula 3 is not limited to the specific examples shown below. In the following structural formula, "●" represents the bonding site with L in formula 1-1.

[0104] [ka]

[0105] In formula 4, R 41 , and R 42 each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L. 41 or R 42 The alkyl group and aryl group represented by R in Formula 2 are 20 The meanings and preferred embodiments are the same as those of the alkyl group and aryl group represented by the following formula:

[0106] In Equation 4, R 41 From the viewpoint of decomposability and color development, R is preferably an alkyl group. 41 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group.

[0107] In Equation 4, R 42 From the viewpoint of decomposability and color development, R is preferably an alkyl group. 42 The alkyl group represented by R is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. 42 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0108] In Formula 4, Zb may be any counter ion for neutralizing the charge, and the entire compound may be included in Za in Formula 1-1. Zb is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a tetrafluoroborate ion.

[0109] Specific examples of the group represented by formula 4 are shown below. However, the group represented by formula 4 is not limited to the specific examples shown below. In the following structural formula, "●" represents the bonding site with L in formula 1-1.

[0110] [ka]

[0111] In formula 1-1, L is an oxygen atom or —NR 10 Preferably, it is -, and more preferably, it is an oxygen atom.

[0112] -NR 10 -R in 10 is preferably an alkyl group. 10 The alkyl group represented by R is preferably an alkyl group having 1 to 10 carbon atoms. 10 The alkyl group represented by R may be linear or branched. 10 The alkyl group represented by the formula (I) may have a ring structure. The alkyl group is preferably a methyl group or a cyclohexyl group.

[0113] -NR 10 -R 10 The aryl group represented by the formula (I) is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and particularly preferably an aryl group having 6 to 12 carbon atoms. The aryl group may have a substituent.

[0114] In Formula 1-1, R 11 ~R 18 are each independently a hydrogen atom, -R a , -OR b , -SR c , or -NR d R e It is preferable that:

[0115] R a ~R e The hydrocarbon group represented by the formula (I) is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably a hydrocarbon group having 1 to 15 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group may be linear or branched. The hydrocarbon group may have a ring structure. The hydrocarbon group is preferably an alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and particularly preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear or branched. The alkyl group may have a ring structure. Examples of alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, s-butyl, tert-butyl, isopentyl, neopentyl, 1-methylbutyl, isohexyl, 2-ethylhexyl, 2-methylhexyl, cyclohexyl, cyclopentyl, and 2-norbornyl. Among these, the alkyl group is preferably a methyl, ethyl, propyl, or butyl group. The alkyl group may have a substituent. Examples of the substituent include an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and a group formed by combining these groups.

[0116] R in Formula 1-1 11 ~R 14 are each independently a hydrogen atom or -R a (i.e., a hydrocarbon group), and more preferably a hydrogen atom or an alkyl group. Except for the following cases, R in Formula 1-1 11 ~R 14 are each preferably independently a hydrogen atom.

[0117] In Formula 1-1, R bonded to the carbon atom bonded to the carbon atom bonded to L 11 and R 13 is preferably an alkyl group, and more preferably the two are linked to form a ring. The ring formed may be a monocyclic or polycyclic ring. Examples of the monocyclic ring include a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, and a cyclohexadiene ring. Examples of the polycyclic ring include an indene ring and an indole ring.

[0118] In Formula 1-1, R bonded to the carbon atom to which A1 is bonded 12 is R 15 or R 16 (preferably R 16 ) to form a ring. 14 is R 17 or R 18 (preferably R 18 ) to form a ring.

[0119] In Formula 1-1, n 13 is 1 and R 16 -R a (i.e., a hydrocarbon group) is preferred.

[0120] In Formula 1-1, R 16 is the R bonded to the carbon atom to which A1 is bonded. 12It is preferable that the ring is linked to the above to form a ring. The ring formed is preferably an indolium ring, a pyrylium ring, a thiopyrylium ring, a benzoxazoline ring, or a benzimidazoline ring, and from the viewpoint of improving the visibility of the exposed area, an indolium ring is more preferable. These rings may further have a substituent.

[0121] In Formula 1-1, n 14 is 1 and R 18 -R a (i.e., a hydrocarbon group) is preferred.

[0122] In Formula 1-1, R 18 is the R bonded to the carbon atom to which A2 is bonded. 14 It is preferable that the ring is linked to the above to form a ring. The ring formed is preferably an indole ring, a pyran ring, a thiopyran ring, a benzoxazole ring, or a benzimidazole ring, and from the viewpoint of improving the visibility of the exposed area, it is more preferably an indole ring. These rings may further have a substituent.

[0123] R in Formula 1-1 16 and R 18 It is preferable that R are the same group. 16 and R 18 When each of these groups forms a ring, it is preferred that they form rings of the same structure except for A1 and A2.

[0124] R in Formula 1-1 15 and R 17 It is preferable that R are the same group. 15 , and R 17 -R a (i.e., a hydrocarbon group), more preferably an alkyl group, and particularly preferably a substituted alkyl group.

[0125] From the viewpoint of improving the water solubility of the compound represented by formula 1-1, R 15 , and R 17is preferably a substituted alkyl group. Examples of the substituted alkyl group include groups represented by the following formulae (a1) to (a4).

[0126] [ka]

[0127] In formulas (a1) to (a4), R W0 represents an alkylene group having 2 to 6 carbon atoms, W represents a single bond or an oxygen atom, and n W1 represents an integer from 1 to 45, and R W1 is an alkyl group having 1 to 12 carbon atoms, or -C(=O)-R W5 represents R W5 represents an alkyl group having 1 to 12 carbon atoms, and R W2 ~R W4 each independently represents a single bond or an alkylene group having 1 to 12 carbon atoms, and M represents a hydrogen atom, a sodium atom, a potassium atom, or an onium group.

[0128] In formula (a1), R W0 Specific examples of the alkylene group represented by the formula (I) include an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, and an isohexyl group. An ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferred, and an n-propylene group is more preferred.

[0129] In formula (a1), n W1 is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3.

[0130] In formula (a1), R W1Specific examples of the alkyl group represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an n-octyl group, and an n-dodecyl group. A methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or a tert-butyl group is preferred, a methyl group or an ethyl group is more preferred, and a methyl group is particularly preferred.

[0131] In formula (a1), R W5 The alkyl group represented by R W1 The meaning and preferred embodiments are also the same as those of the alkyl group represented by the following formula:

[0132] Specific examples of the group represented by formula (a1) are shown below. However, the group represented by formula (a1) is not limited to the specific examples shown below. In the following structural formulas, Me represents a methyl group, Et represents an ethyl group, and * represents a bonding site.

[0133] [ka]

[0134] In formulas (a2) to (a4), R W2 ~R W4 Specific examples of the alkylene group represented by the formula (I) include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, an n-octylene group, and an n-dodecylene group, of which an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferred, and an ethylene group or an n-propylene group is more preferred.

[0135] In formula (a3), the two M's may be the same or different.

[0136] In the formulae (a2) to (a4), examples of the onium group represented by M include an ammonium group, an iodonium group, a phosphonium group, and a sulfonium group.

[0137] CO2M in formula (a2), PO3M2 in formula (a2), and SO3M in formula (a4) may each have an anionic structure in which M is dissociated. The counter cation of the anionic structure is A1 + or R in Formula 1-1 1 -L may be a cation that can be contained therein.

[0138] Among the groups represented by formulae (a1) to (a4), groups represented by formula (a1), formula (a2) or formula (a4) are preferred.

[0139] n in Formula 1-1 11 and n 12 are preferably the same, and are both preferably integers of 1 to 5, more preferably integers of 1 to 3, even more preferably 1 or 2, and particularly preferably 2.

[0140] In formula 1-1, A1 and A2 each independently represent an oxygen atom, a sulfur atom, or a nitrogen atom, and are preferably a nitrogen atom. In formula 1-1, A1 and A2 are preferably the same atom.

[0141] Za in Formula 1-1 represents a counter ion that neutralizes the charge. 11 ~R 18 and R 1 If all of -L are charge-neutral groups, Za is a monovalent counter anion. 11 ~R 18 and R 1 -L may have an anionic or cationic structure. For example, R 11 ~R 18 and R 1When -L contains two or more anionic structures, Za can also serve as a counter cation. Note that Za is not necessary if the compound represented by Formula 1-1 has a charge-neutral structure throughout the compound, excluding Za. When Za is a counter anion, examples of the counter anion include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, and a perchlorate ion, with a tetrafluoroborate ion being preferred. When Za is a counter cation, examples of the counter cation include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, and a sulfonium ion, with a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion being preferred, with a sodium ion, a potassium ion, or an ammonium ion being more preferred.

[0142] (Compound represented by formula 1-2) The decomposable compound, which is one type of color-changing compound, is preferably a compound represented by the following formula 1-2: The compound represented by the following formula 1-2 is a cyanine dye.

[0143] [ka]

[0144] In formula 1-2, R 1 represents a group represented by any one of the above formulas 2 to 4, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e represents R 23 , and R 24 are each independently -R a represents R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R21 and R 22 , or R 23 and R 24 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 , and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion that neutralizes the charge.

[0145] R in Equation 1-2 1 is R in Equation 1-1 1 The same applies to the preferred embodiments.

[0146] In Formula 1-2, R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b or -CN. 19 , and R 21 is a hydrogen atom or -R a It is preferable that R 20 , and R 22 is a hydrogen atom, -R a , -OR b or -CN.

[0147] In Formula 1-2, R 19 ~R 22 -R expressed as a is preferably an alkyl group or an alkenyl group. 19 ~R 22 All of -R a If R 19 and R 20 , and R 21 and R 22 are preferably linked to form a monocyclic or polycyclic ring. 19 and R 20 , or R 21 and R 22Examples of the ring formed by linking include a benzene ring and a naphthalene ring.

[0148] In Formula 1-2, R 23 and R 24 are preferably linked to form a monocyclic or polycyclic ring. 23 and R 24 The ring formed by linking may be a monocyclic ring or a polycyclic ring. Examples of the monocyclic ring include a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, and a cyclohexadiene ring. Examples of the polycyclic ring include an indene ring.

[0149] In Formula 1-2, R d1 ~R d4 is preferably an unsubstituted alkyl group. d1 ~R d4 are preferably the same group. The unsubstituted alkyl group includes, for example, an unsubstituted alkyl group having 1 to 4 carbon atoms, and a methyl group is preferred.

[0150] In order to increase the water solubility of the compound represented by formula 1-2, W in formula 1-2 1 , and W 2 is preferably a substituted alkyl group. 1 and W 2 Examples of the substituted alkyl group represented by the formula (a1) include the groups represented by the formula (a1) to the formula (a4) described above in the section "Compound represented by formula 1-1," and the preferred embodiments are also the same. 1 , and W 2 are each independently an alkyl group having a substituent, and the substituent is preferably —(OCH2CH2)—, a sulfo group, a salt of a sulfo group, a carboxy group, or a group having at least a salt of a carboxy group.

[0151] In Formula 1-2, Za represents a counter ion that neutralizes the charge within the molecule. 19 ~R 22 , R 23 ~R 24 , Rd1 ~R d4 , W 1 , W 2 , and R 1 If all of -L are charge-neutral groups, Za is a monovalent counter anion. 19 ~R 22 , R 23 ~R 24 , R d1 ~R d4 , W 1 , W 2 , and R 1 -L may have an anionic or cationic structure. For example, R 19 ~R 22 , R 23 ~R 24 , R d1 ~R d4 , W 1 , W 2 , and R 1 When -L contains two or more anion structures, Za can also be a counter cation. Note that Za is not necessary if the compound represented by formula 1-2 has a charge-neutral structure throughout the compound, excluding Za. Examples of when Za is a counter anion are the same as Za in formula 1-1, and preferred embodiments are also the same. Examples of when Za is a counter cation are the same as Za in formula 1-1, and preferred embodiments are also the same.

[0152] (Compounds represented by formulas 1-3 to 1-7) From the viewpoints of decomposability and color development, the decomposable compound, which is a type of color-changing compound, is preferably a compound represented by any one of the following formulas 1-3 to 1-7, and more preferably a compound represented by any one of the following formulas 1-3, 1-5, and 1-6. The compounds represented by the following formulas 1-3 to 1-7 are cyanine dyes.

[0153] [ka]

[0154] In formulas 1-3 to 1-7, R 1represents a group represented by any one of the above formulas 2 to 4, and R 19 ~R 22 are each independently a hydrogen atom, a halogen atom, or -R a , -OR b , -CN, -SR c , or -NR d R e represents R 23 , and R 24 are each independently -R a represents R 25 , and R 26 are each independently a hydrogen atom, a halogen atom, or -R a represents R a ~R e each independently represents a hydrocarbon group; R 19 and R 20 , R 21 and R 22 , R 23 and R 24 , or R 25 and R 26 may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or -NR 10 - represents R 10 represents a hydrogen atom, an alkyl group, or an aryl group; R d1 ~R d4 , W 1 , and W 2 each independently represents an alkyl group which may have a substituent, and Za represents a counter ion that neutralizes the charge.

[0155] R in Formulas 1-3 to 1-7 1 , R 19 ~R 22 , R d1 ~R d4 , W 1 , W 2 , and L is R in Formula 1-2 1 , R 19 ~R 22 , R d1 ~R d4 , W 1 , W 2 The meanings and preferred embodiments of R in Formula 1-7 are the same as those of L. 25 and R26 are each independently preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, and particularly preferably a methyl group.

[0156] Specific examples of cyanine dyes included in the decomposable compounds are shown below, but the cyanine dyes are not limited to the specific examples shown below.

[0157] [ka]

[0158] As the cyanine dye included in the decomposable compound, the infrared absorbing compounds described in WO 2019 / 219560 can be suitably used.

[0159] The color-changing compound may contain an acid color former. As the acid color former, for example, the acid color formers described in the section "Image Recording Layer" below can be used, and the same applies to preferred embodiments. As the color-changing compound, the above-mentioned decomposable compound and the below-mentioned acid generator may be used in combination.

[0160] The outermost layer may contain one or more types of color-changing compounds.

[0161] From the viewpoint of color development, the content of the color-changing compound in the outermost layer is preferably 0.10% by mass to 50% by mass, more preferably 0.50% by mass to 30% by mass, and particularly preferably 1.0% by mass to 20% by mass, relative to the total mass of the outermost layer.

[0162] The content of the infrared absorbing agent in the image recording layer (M Y ) the content of the color-changing compound in the outermost layer (M X ) ratio (M X / M Y ) is preferably 0.1 or more, more preferably 0.2 or more, and particularly preferably 0.3 or more and 3.0 or less, from the viewpoint of color development.

[0163] [Other ingredients] The outermost layer may contain other components in addition to the components described above, such as an oil sensitizer, an acid generator, and an infrared absorbing agent.

[0164] An acid generator is a compound that generates an acid when exposed to light or heat. Examples of acid generators include compounds that decompose upon exposure to infrared light to generate an acid. The acid generated is preferably a strong acid with a pKa of 2 or less (e.g., sulfonic acid and hydrochloric acid). The acid generated from the acid generator can cause the acid color former to change color. From the viewpoints of sensitivity and stability, the acid generator is preferably an onium salt compound. Specific examples of onium salts suitable as acid generators include the compounds described in paragraphs 0121 to 0124 of WO 2016 / 047392. Examples of onium salts suitable as acid generators include sulfonates, carboxylates, and BPh4 of triarylsulfonium or diaryliodonium. - , BF4 - , PF6 - , or ClO4 - Here, Ph represents a phenyl group.

[0165] Examples of the infrared absorbing agent include the infrared absorbing agents described in the section "Image Recording Layer" below.

[0166] [Formation method] The outermost layer can be formed by a known method (for example, a coating method). The coating amount (solid content) of the outermost layer is 5 mg / m 2 ~2,000mg / m 2 Preferably, it is 20 mg / m 2 ~1,000mg / m 2 In the present disclosure, the term "solid content" refers to components other than the solvent.

[0167] <<Brightness change>> In one embodiment, 110 mJ / cm 2When exposed to infrared light having a wavelength of 830 nm at an energy density of 1000 kJ / cm, the change in lightness ΔL before and after exposure is preferably 2.0 or more, more preferably 3.0 or more, even more preferably 5.0 or more, particularly preferably 8.0 or more, and most preferably 10.0 or more. When the lightness change ΔL is within the above range, the visibility of the exposed area can be improved. There is no upper limit to the lightness change ΔL. An example of the upper limit of the lightness change ΔL is 20.0. In particular, when the outermost layer contains a color-changing compound, it is preferable that the lightness change ΔL satisfy the above range.

[0168] The lightness change ΔL is measured by the following method: the lithographic printing plate precursor is printed using a Luxel PLATESETTER T-9800 manufactured by Fujifilm Global Graphic Systems Co., Ltd., equipped with an infrared semiconductor laser with a wavelength of 830 nm, under conditions of 99.5% output, an outer drum rotation speed of 220 rpm (revolutions per minute), and a resolution of 2,400 dpi (dots per inch, 1 inch = 25.4 mm) (energy density: 110 mJ / cm 2 The exposure is carried out in an environment of 25°C and 50% RH (relative humidity). The change in brightness of the lithographic printing plate precursor before and after exposure is measured. The brightness is measured using a spectrophotometer eXact manufactured by X-Rite. Specifically, the brightness is measured from the outermost layer side of the lithographic printing plate precursor to the L * a * b * Color space L * The value (brightness) of the exposed area was measured. * value and L of the unexposed area * The absolute value of the difference between the values is taken as the brightness change ΔL.

[0169] <<Support>> The on-press development type lithographic printing plate precursor according to an embodiment of the present disclosure has a support. The support can be appropriately selected from supports used in known lithographic printing plate precursors. The support is preferably a support having a hydrophilic surface.

[0170] The support is preferably an aluminum plate that has been subjected to a surface roughening treatment and anodizing treatment by a known method. Specifically, the support preferably comprises an aluminum plate and an anodized aluminum coating disposed on the aluminum plate.

[0171] The anodized aluminum film is preferably located closer to the image recording layer than the aluminum plate, and the anodized aluminum film preferably has micropores extending in the depth direction from the surface on the image recording layer side.

[0172] Preferred embodiments of the support will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a support according to one embodiment. The aluminum support 12a shown in FIG. 1 has a structure in which an aluminum plate 18 and an aluminum anodized film 20a (hereinafter simply referred to as "anodized film 20a") are laminated in this order. The anodized film 20a on the aluminum support 12a is located closer to the image recording layer than the aluminum plate 18. In other words, a lithographic printing plate precursor according to one embodiment preferably has an aluminum plate, and on the aluminum plate, at least an aluminum anodized film, an image recording layer, and an outermost layer, in this order.

[0173] A preferred embodiment of the anodized coating 20a will be described below. The anodized coating 20a is a coating formed on the surface of the aluminum plate 18 by anodizing. The anodized coating 20a has extremely fine micropores 22a that are substantially perpendicular to the coating surface and are uniformly distributed. The micropores 22a extend from the surface of the anodized coating 20a on the image recording layer side (i.e., the surface of the anodized coating 20a opposite the aluminum plate 18 side) in the depth direction (i.e., toward the aluminum plate 18 side).

[0174] The average diameter (i.e., average opening diameter) of the micropores 22a on the surface of the anodized coating 20a is greater than 10 nm and not greater than 100 nm. When the average diameter of the micropores 22a on the surface of the anodized coating 20a exceeds 10 nm, printing durability and image visibility are improved. When the average diameter of the micropores 22a on the surface of the anodized coating 20a is not greater than 100 nm, printing durability is improved. From the viewpoint of a balance between printing durability, stain resistance, and image visibility, the average diameter of the micropores 22a on the surface of the anodized coating 20a is preferably 15 nm to 60 nm, more preferably 20 nm to 50 nm, and particularly preferably 25 nm to 40 nm. The internal diameter of the micropores 22a may be wider or narrower than the opening diameter of the micropores 22a. The average diameter of the micropores 22a on the surface of the anodized coating 20a is the average value of the diameters of 50 micropores present in an area of 400 nm × 600 nm measured in four images obtained by observing four locations on the surface of the anodized coating 20a using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000. Note that if the shape of the observed micropores 22a is not circular, the circle-equivalent diameter is used. The "circle-equivalent diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle with the same projected area as the projected area of the opening.

[0175] The shape of the micropores 22a in the depth direction is not limited. The micropores 22a shown in Fig. 1 are substantially straight tubular (substantially cylindrical). The micropores 22a may also be conical, with a diameter that decreases in the depth direction (thickness direction). The shape of the bottom of the micropores 22a is not limited. The shape of the bottom of the micropores 22a may be curved (convex) or flat.

[0176] The micropores in the support may have large-diameter pores extending from the surface of the anodized coating to a certain depth, and small-diameter pores communicating with the bottoms of the large-diameter pores and extending from the communicating positions with the large-diameter pores to a certain depth. The terms "large diameter" used in relation to the large-diameter pores and "small diameter" used in relation to the small-diameter pores refer to the relative size relationship between the diameters of the pores. That is, the diameters of the large-diameter pores may be larger than the diameters of the small-diameter pores.

[0177] Fig. 2 is a schematic cross-sectional view of a support according to another embodiment. For example, as shown in Fig. 2, an aluminum support 12b includes an aluminum plate 18 and an anodized film 20b having micropores 22b each having a large-diameter pore portion 24 and a small-diameter pore portion 26. For example, the micropores 22b in the anodized film 20b include large-diameter pore portions 24 extending from the surface of the anodized film 20b to a depth of 10 nm to 1,000 nm (i.e., depth D shown in Fig. 2), and small-diameter pore portions 26 that communicate with the bottoms of the large-diameter pore portions 24 and extend from the communicating positions with the large-diameter pore portions 24 to a depth of 20 nm to 2,000 nm. Specific embodiments of the large-diameter pore portions and the small-diameter pore portions can be described, for example, in paragraphs 0107 to 0114 of JP 2019-162855 A.

[0178] In one embodiment, the support includes an aluminum plate and an anodized aluminum film disposed on the aluminum plate, the anodized film being located closer to the image recording layer than the aluminum plate, the anodized film having micropores extending in the depth direction from the surface facing the image recording layer, the average diameter of the micropores at the surface of the anodized film being preferably greater than 10 nm and not greater than 100 nm, the micropores having large-diameter portions extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm and small-diameter portions communicating with the bottoms of the large-diameter portions and extending from the communicating positions with the large-diameter portions to a depth of 20 nm to 2,000 nm, the average diameter of the large-diameter portions at the surface of the anodized film being preferably 15 nm to 100 nm and the average diameter of the small-diameter portions at the communicating positions being not greater than 13 nm.

[0179] [Method of manufacturing the support] As a method for producing a support, for example, a production method in which the following steps are carried out in order is preferred. (1) Surface roughening process: A process of roughening the surface of an aluminum plate. (2) Anodizing process: A process of anodizing the roughened aluminum plate. (3) Pore widening process: A process in which the aluminum plate having the anodized film obtained in the anodizing process is brought into contact with an acidic or alkaline aqueous solution to widen the diameter of the micropores in the anodized film. The procedure for each step will be described in detail below.

[0180] (Surface roughening process) The surface roughening treatment step is carried out, for example, by subjecting the surface of the aluminum plate to a roughening treatment including electrochemical roughening treatment. The surface roughening treatment step is preferably carried out before the anodizing treatment step described below, but may not be carried out if the surface of the aluminum plate already has a desirable surface shape. The surface roughening treatment step can be carried out, for example, by the method described in paragraphs 0086 to 0101 of JP 2019-162855 A.

[0181] (anodizing process) The procedure for the anodizing treatment step is not particularly limited as long as the above-mentioned micropores can be obtained, and known methods can be used. In the anodizing treatment step, for example, an aqueous solution of sulfuric acid, phosphoric acid, or oxalic acid can be used as the electrolyte. For example, the concentration of sulfuric acid can be 100 g / L to 300 g / L. The anodizing treatment conditions are appropriately set depending on the electrolyte used. For example, the solution temperature can be 5°C to 70°C (preferably 10°C to 60°C), and the current density can be 0.5 A / dm 2 ~60A / dm 2 (preferably 1A / dm 2 ~60A / dm 2), the voltage is 1 V to 100 V (preferably 5 V to 50 V), the electrolysis time is 1 second to 100 seconds (preferably 5 seconds to 60 seconds), and the coating amount is 0.1 g / m 2 ~5g / m 2 (preferably 0.2g / m 2 ~3g / m 2 ) conditions are included.

[0182] (Porewide processing process) The pore widening treatment step is a treatment for enlarging the diameter of micropores present in the anodized film formed by the above-mentioned anodizing treatment step. The pore widening treatment can be carried out by contacting the aluminum plate obtained by the above-mentioned anodizing treatment step with an acid aqueous solution or an alkaline aqueous solution. The contacting method is not particularly limited, and examples thereof include immersion and spraying.

[0183] <<Image recording layer>> The on-press development type lithographic printing plate precursor according to an embodiment of the present disclosure has an image recording layer. The image recording layer is preferably a negative image recording layer. The image recording layer preferably contains a polymerization initiator and a polymerizable compound, and more preferably contains an infrared absorber, a polymerization initiator, and a polymerizable compound.

[0184] [Infrared absorber] The image recording layer preferably contains an infrared absorbing agent, such as a pigment or a dye.

[0185] Examples of dyes used as infrared absorbers include commercially available dyes and known dyes (for example, dyes described in "Dye Handbook" (edited by the Society of Organic Synthetic Chemistry, published in 1970). Specific examples of dyes include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complexes.

[0186] Preferred dyes include, for example, cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. More preferred dyes include cyanine dyes and indolenine cyanine dyes. Among these, cyanine dyes are particularly preferred.

[0187] The infrared absorber is preferably a cationic polymethine dye having an oxygen atom, a nitrogen atom, or a halogen atom at the meso position. Preferred examples of the cationic polymethine dye include cyanine dyes, pyrylium dyes, thiopyrylium dyes, and azulenium dyes. From the viewpoints of availability and solvent solubility during the introduction reaction, the cationic polymethine dye is preferably a cyanine dye.

[0188] Specific examples of cyanine dyes include the compounds described in paragraphs 0017 to 0019 of JP-A No. 2001-133969, the compounds described in paragraphs 0016 to 0021 of JP-A No. 2002-023360, and the compounds described in paragraphs 0012 to 0037 of JP-A No. 2002-040638. Preferred cyanine dyes include the compounds described in paragraphs 0034 to 0041 of JP-A No. 2002-278057 and the compounds described in paragraphs 0080 to 0086 of JP-A No. 2008-195018. Particularly preferred cyanine dyes include, for example, the compounds described in paragraphs 0035 to 0043 of JP-A No. 2007-90850 and the compounds described in paragraphs 0105 to 0113 of JP-A No. 2012-206495. In addition, the compounds described in paragraphs 0008 to 0009 of JP-A No. 5-5005 and paragraphs 0022 to 0025 of JP-A No. 2001-222101 can also be preferably used.

[0189] As a counter cation of the cyanine dye, for example, a borate compound described below may be used.

[0190] As the pigment, the compounds described in paragraphs 0072 to 0076 of JP-A No. 2008-195018 are preferred.

[0191] As the infrared absorber, an infrared absorber that decomposes upon exposure to infrared light (hereinafter also referred to as a "decomposable infrared absorber") can be suitably used. As the infrared absorber that decomposes upon exposure to infrared light, the compounds described in JP-A-2008-544322, WO 2016 / 027886, WO 2017 / 141882, or WO 2018 / 043259 can be suitably used. In addition, in the image recording layer, the color-changing compounds described in the above "Outermost Layer" section can also be suitably used as the infrared absorber. Preferred embodiments of the color-changing compound used as the infrared absorber in the image recording layer are the same as the preferred embodiments of the color-changing compound described in the above "Outermost Layer" section.

[0192] The image recording layer may contain one or more infrared absorbing agents, and a pigment and a dye may be used in combination as the infrared absorbing agent.

[0193] The content of the infrared absorbent is preferably 0.1% by mass to 10.0% by mass, and more preferably 0.5% by mass to 5.0% by mass, relative to the total mass of the image recording layer. When the outermost layer contains an infrared absorbent, from the viewpoints of visibility over time, storage stability, and UV printing durability, the total content of the infrared absorbent in the image recording layer is preferably equal to or greater than the total content of the infrared absorbent in the outermost layer, and more preferably greater than the total content of the infrared absorbent in the outermost layer. The total content of the infrared absorbent is expressed by mass.

[0194] [Polymerization initiator] The image recording layer preferably contains a polymerization initiator. Examples of the polymerization initiator include an electron-accepting polymerization initiator and an electron-donating polymerization initiator. The image recording layer preferably contains an electron-accepting polymerization initiator, more preferably contains at least one selected from the group consisting of electron-accepting polymerization initiators and electron-donating polymerization initiators, and particularly preferably contains an electron-accepting polymerization initiator and an electron-donating polymerization initiator.

[0195] (Electron-accepting polymerization initiator) The image recording layer preferably contains an electron-accepting polymerization initiator, which is a compound that generates a polymerization initiating species (e.g., a radical) by accepting one electron through intermolecular electron transfer when electrons in the infrared absorber are excited by infrared exposure.

[0196] Examples of electron-accepting polymerization initiators include compounds that generate polymerization initiating species (e.g., radicals or cations) by the energy of light, heat, or both (e.g., thermal polymerization initiators, compounds having bonds with small bond dissociation energy, and photopolymerization initiators). The electron-accepting polymerization initiator is preferably a radical polymerization initiator, more preferably an onium salt compound. Furthermore, the electron-accepting polymerization initiator is preferably an infrared-sensitive polymerization initiator.

[0197] Preferred electron-accepting polymerization initiators include oxime ester compounds and onium salt compounds from the viewpoint of curability. From the viewpoint of printing durability, iodonium salt compounds, sulfonium salt compounds, and azinium salt compounds are preferred, iodonium salt compounds and sulfonium salt compounds are more preferred, and iodonium salt compounds are particularly preferred.

[0198] The iodonium salt compound is preferably a diaryliodonium salt compound, and more preferably a diphenyliodonium salt compound substituted with an electron-donating group, such as an alkyl group or an alkoxy group. Furthermore, the iodonium salt compound is preferably an asymmetric diphenyliodonium salt compound. Specific examples of iodonium salt compounds include diphenyliodonium hexafluorophosphate, 4-methoxyphenyl-4-(2-methylpropyl)phenyliodonium hexafluorophosphate, 4-(2-methylpropyl)phenyl-p-tolyliodonium hexafluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium tetrafluoroborate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, and bis(4-t-butylphenyl)iodonium hexafluorophosphate.

[0199] Examples of counter anions of iodonium salt compounds or sulfonium salt compounds include sulfonate anions, carboxylate anions, tetrafluoroborate anions, hexafluorophosphate anions, p-toluenesulfonate anions, tosylate anions, sulfonamide anions, and sulfonimide anions. Among these, sulfonamide anions or sulfonimide anions are preferred, and sulfonimide anions are more preferred. As sulfonamide anions, arylsulfonamide anions are preferred. As sulfonimide anions, bisarylsulfonimide anions are preferred. Specific examples of sulfonamide anions or sulfonimide anions include the compounds described in paragraph 0034 of WO 2019 / 013268. The contents of the above publications are incorporated herein by reference.

[0200] From the viewpoints of color development over time after exposure, developability, and UV printing durability of the resulting lithographic printing plate, the electron-accepting polymerization initiator is preferably at least one selected from the group consisting of compounds represented by the following formula (II) and compounds represented by the following formula (III), and more preferably a compound represented by formula (II). Furthermore, the compounds represented by the following formula (II) and formula (III) are preferred because of their excellent visibility.

[0201] [ka]

[0202] In formula (II) and formula (III), X represents a halogen atom, and R 3 , R 4 , and R 5 each independently represents a monovalent hydrocarbon group. The hydrocarbon group preferably has 1 to 20 carbon atoms. In formula (II), X represents a halogen atom, and R 3 preferably represents an aryl group.

[0203] Examples of X in formula (II) and formula (III) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. X in formula (II) and formula (III) is preferably a bromine atom.

[0204] In formula (II) and formula (III), R 3 , R 4 , and R 5 are each independently preferably an aryl group, and more preferably an aryl group substituted with an amide group, from the viewpoint of achieving an excellent balance between sensitivity and storage stability.

[0205] The electron-accepting polymerization initiator is particularly preferably a compound represented by the following formula (IV).

[0206] [ka]

[0207] In formula (IV), X represents a halogen atom, and R 4 , and R 5 each independently represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, p and q each independently represent an integer of 1 to 5, and p+q is an integer of 2 to 6. X in formula (IV) has the same meaning as X in formula (II).

[0208] Specific examples of the compound represented by formula (II) are shown below: However, the compound represented by formula (II) is not limited to the specific examples shown below.

[0209] [ka]

[0210] [ka]

[0211] [ka]

[0212] [ka]

[0213] [ka]

[0214] [ka]

[0215] [ka]

[0216] From the viewpoints of improving sensitivity and reducing plate skipping, the energy level of the lowest unoccupied molecular orbital (LUMO) of the electron-accepting polymerization initiator is preferably −3.00 eV or less, more preferably −3.02 eV or less, and preferably −3.80 eV or more, more preferably −3.50 eV or more.

[0217] In the present disclosure, the energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are calculated using the following method. First, the counter anion in the compound being calculated is ignored. Using quantum chemistry calculation software Gaussian09, structural optimization is performed using DFT (B3LYP / 6-31G(d)). MO (molecular orbital) energy calculations are performed using DFT (B3LYP / 6-31+G(d,p) / CPCM (solvent=methanol)) based on the structure obtained by the structural optimization. The MO energy Ebare (unit: hartree) obtained in the MO energy calculation is converted to Escaled (unit: eV), which is used as the HOMO and LUMO values in the present disclosure, using the following formula: In the following formula, 27.2114 is simply a coefficient for converting hartrees to eV, and 0.823168 and -1.07634 are adjustment coefficients that determine the HOMO and LUMO of the compound being calculated so that the calculation matches the measured values. Formula: Escaled=0.823168×27.2114×Ebare-1.07634

[0218] The image recording layer may contain one or more electron-accepting polymerization initiators.

[0219] The content of the electron-accepting polymerization initiator is preferably 0.1% by mass to 50% by mass, more preferably 0.5% by mass to 30% by mass, and particularly preferably 0.8% by mass to 20% by mass, relative to the total mass of the image recording layer.

[0220] (Electron-donating polymerization initiator) The image recording layer preferably contains an electron-donating polymerization initiator. The electron-donating polymerization initiator is a compound that generates a polymerization initiation species (e.g., a radical) by donating one electron to an orbital of the infrared absorber that has lost one electron through intermolecular electron transfer when an electron of the infrared absorber is excited or transferred intramolecularly by infrared exposure. The electron-donating polymerization initiator is preferably an electron-donating radical polymerization initiator.

[0221] From the viewpoint of printing durability and color development, the image recording layer preferably contains a borate compound as an electron-donating polymerization initiator. As the borate compound, from the viewpoint of printing durability and color development, a tetraarylborate compound or a monoalkyltriarylborate compound is preferred, and a tetraarylborate compound is more preferred.

[0222] The counter cation of the borate compound is not limited. The counter cation of the borate compound is preferably an alkali metal ion or a tetraalkylammonium ion, and more preferably a sodium ion, a potassium ion, or a tetrabutylammonium ion. The counter cation of the borate compound may also be the cationic polymethine dye described above in the section "Infrared absorber."

[0223] A preferred borate compound is, for example, sodium tetraphenylborate.

[0224] Preferred specific examples (B-1 to B-9) of the electron-donating polymerization initiator are shown below. In the following chemical formulas, Ph represents a phenyl group, and Bu represents an n-butyl group. However, the electron-donating polymerization initiator is not limited to the specific examples shown below.

[0225] [ka]

[0226] From the viewpoints of improving sensitivity and reducing plate skipping, the energy level of the highest occupied molecular orbital (HOMO) of the electron-donating polymerization initiator is preferably −6.00 eV or higher, more preferably −5.95 eV or higher, and particularly preferably −5.93 eV or higher. The energy level of the highest occupied molecular orbital (HOMO) of the electron-donating polymerization initiator is preferably −5.00 eV or lower, more preferably −5.40 eV or lower.

[0227] The image recording layer may contain one or more electron-donating polymerization initiators.

[0228] From the viewpoints of sensitivity and printing durability, the content of the electron-donating polymerization initiator is preferably 0.01% by mass to 30% by mass, more preferably 0.05% by mass to 25% by mass, and particularly preferably 0.1% by mass to 20% by mass, relative to the total mass of the image recording layer.

[0229] (Compounds in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form an ion pair) In one embodiment, the image recording layer preferably contains a compound (i.e., a salt) in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form an ion pair. For example, the polymerization initiator is preferably a compound in which an anion in the electron-donating polymerization initiator and a cation in the electron-accepting polymerization initiator form an ion pair, more preferably a compound in which an onium cation and a borate anion form an ion pair, even more preferably a compound in which an iodonium cation or a sulfonium cation and a borate anion form an ion pair, and particularly preferably a compound in which a diaryliodonium cation or a triarylsulfonium cation and a tetraarylborate anion form an ion pair. Preferred aspects of the anion in the electron-donating polymerization initiator that forms an ion pair are the same as the preferred aspects of the anion in the electron-donating polymerization initiator described above. Preferred aspects of the cation in the electron-accepting polymerization initiator that forms an ion pair are the same as the preferred aspects of the cation in the electron-accepting polymerization initiator described above.

[0230] When the image recording layer contains an anion that is an electron-donating polymerization initiator and a cation that is an electron-accepting polymerization initiator (i.e., when the image recording layer contains a compound that forms an ion pair as described above), the image recording layer is considered to contain an electron-accepting polymerization initiator and an electron-donating polymerization initiator. A compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form an ion pair may be used as either an electron-donating polymerization initiator or an electron-accepting polymerization initiator. A compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form an ion pair may be used in combination with the electron-donating polymerization initiator described above, or may be used in combination with the electron-accepting polymerization initiator described above.

[0231] (Polymerization initiator content) The image recording layer may contain one or more polymerization initiators. The content of the polymerization initiator is preferably 0.1 to 50% by mass, more preferably 0.5 to 30% by mass, and particularly preferably 0.8 to 20% by mass, relative to the total mass of the image recording layer.

[0232] (Preferred Embodiments of Electron-Donating Polymerization Initiator and Infrared Absorber) From the viewpoints of improving sensitivity and printing durability, the image recording layer preferably has a value of the ratio of the energy level of the highest occupied molecular orbital (HOMO) of the infrared absorber to the energy level of the highest occupied molecular orbital (HOMO) of the electron-donating polymerization initiator of 0.70 eV or less, more preferably 0.70 eV to −0.10 eV, where a negative value means that the energy level of the HOMO of the electron-donating polymerization initiator is higher than that of the infrared absorber.

[0233] (Preferred Embodiments of Electron Acceptor Polymerization Initiator and Infrared Absorber) From the viewpoints of improving sensitivity and printing durability, the image recording layer preferably has a value of the ratio of the energy level of the lowest unoccupied molecular orbital (LUMO) of the electron-accepting polymerization initiator to the energy level of the lowest unoccupied molecular orbital (LUMO) of the infrared absorber of 1.00 eV or less, more preferably 1.00 eV to −0.10 eV, and particularly preferably 0.80 eV to 0.30 eV. Note that a negative value means that the energy level of the LUMO of the infrared absorber is higher than the energy level of the LUMO of the electron-accepting polymerization initiator.

[0234] [Polymerizable compound] The image recording layer preferably contains a polymerizable compound. In the present disclosure, the term "polymerizable compound" refers to a compound having a polymerizable group.

[0235] Examples of the polymerizable group include known polymerizable groups. The polymerizable group is preferably an ethylenically unsaturated group. The polymerizable group may be a radically polymerizable group or a cationically polymerizable group, and is preferably a radically polymerizable group. Examples of the radically polymerizable group include a (meth)acryloyl group, an allyl group, a vinylphenyl group, and a vinyl group, and from the viewpoint of reactivity, a (meth)acryloyl group is preferred.

[0236] The molecular weight of the polymerizable compound (weight average molecular weight when there is a molecular weight distribution) is preferably 50 or more and less than 2,500.

[0237] The polymerizable compound may be, for example, a radically polymerizable compound or a cationically polymerizable compound, and is preferably an addition-polymerizable compound having at least one ethylenically unsaturated bond (i.e., an ethylenically unsaturated compound). The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, and more preferably a compound having two or more terminal ethylenically unsaturated bonds.

[0238] The chemical form of the polymerizable compound may be a monomer, a prepolymer (for example, a dimer, a trimer, or an oligomer), or a mixture thereof.

[0239] From the viewpoint of UV printing durability, the polymerizable compound preferably has three or more polymerizable groups, more preferably has seven or more polymerizable groups, and particularly preferably has ten or more polymerizable groups. From the viewpoint of UV printing durability of the resulting lithographic printing plate, the polymerizable compound preferably contains an ethylenically unsaturated compound having three or more (preferably seven or more, more preferably ten or more) ethylenically unsaturated groups, and more preferably contains a (meth)acrylate compound having three or more (preferably seven or more, more preferably ten or more) (meth)acryloyl groups.

[0240] (oligomer) The polymerizable compound preferably includes a polymerizable compound that is an oligomer (hereinafter simply referred to as "oligomer"). In the present disclosure, "oligomer" refers to a polymerizable compound having a molecular weight (weight average molecular weight when there is a molecular weight distribution) of 600 or more and 10,000 or less and having at least one polymerizable group. From the viewpoint of excellent chemical resistance and UV printing durability, the molecular weight of the oligomer is preferably 1,000 or more and 5,000 or less.

[0241] From the viewpoint of improving UV 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 upper limit to the number of polymerizable groups in the oligomer. The number of polymerizable groups in the oligomer is preferably 20 or less.

[0242] From the viewpoints of UV printing durability and on-press developability, the oligomer is preferably an oligomer having 7 or more polymerizable groups and a molecular weight of 1,000 to 10,000, and more preferably an oligomer having 7 or more polymerizable groups and 20 or less and a molecular weight of 1,000 to 5,000. When the image recording layer contains an oligomer as a polymerizable compound, the image recording layer may contain a polymer component that may be generated in the process of producing the oligomer.

[0243] From the viewpoints of UV printing durability, visibility, and on-press developability, the oligomer preferably contains at least one selected from the group consisting of a compound having a urethane bond, a compound having an ester bond, and a compound having an epoxy residue, and more preferably contains a compound having a urethane bond. In the present disclosure, the term "epoxy residue" refers to a group having a structure formed by an epoxy group. Examples of the structure formed by an epoxy group include a structure obtained by the reaction of an acid group (e.g., a carboxylic acid group) with an epoxy group.

[0244] - Compounds with urethane bonds - The compound having a urethane bond, which is an example of an oligomer, is preferably, for example, a compound having at least a group represented by the following formula (Ac-1) or formula (Ac-2), and more preferably a compound having at least a group represented by the following formula (Ac-1).

[0245] [ka]

[0246] In formula (Ac-1) and formula (Ac-2), L 1 ~L 4 each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and the wavy line portion represents the bonding position to other structures.

[0247] L in formula (Ac-1) and formula (Ac-2) 1 ~L 4are each independently preferably an alkylene group having 2 to 20 carbon atoms, more preferably an alkylene group having 2 to 10 carbon atoms, and particularly preferably an alkylene group having 4 to 8 carbon atoms. The alkylene group may have a branched structure or a cyclic structure. The alkylene group is preferably a linear alkylene group.

[0248] It is preferred that the wavy line portions in formula (Ac-1) or formula (Ac-2) are each independently directly bonded to the wavy line portions in the groups represented by formula (Ae-1) or formula (Ae-2) below.

[0249] [ka]

[0250] In formula (Ae-1) and formula (Ae-2), R each independently represents an acryloyloxy group or a methacryloyloxy group, and the wavy line portion represents the bonding position to the wavy line portion in formula (Ac-1) or formula (Ac-2).

[0251] The compound having a urethane bond may be a compound obtained by introducing a polymerizable group into a polyurethane obtained by reacting a polyisocyanate compound with a polyol compound through a polymer reaction. For example, a compound having a urethane bond may be obtained by reacting a polyurethane oligomer obtained by reacting a polyol compound having an acid group with a polyisocyanate compound with a compound having an epoxy group and a polymerizable group.

[0252] - Compounds with ester bonds - The number of polymerizable groups in a compound having an ester bond, which is an example of an oligomer, is preferably 3 or more, and more preferably 6 or more.

[0253] -Compounds containing epoxy residues- 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 to 3. The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

[0254] Commercially available oligomers may be used. Examples of commercially available oligomers include UA510H, UA-306H, UA-306I, and UA-306T (all manufactured by Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, and UV7620EA (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), U-15HA (manufactured by Shin-Nakamura Chemical Co., Ltd.), and EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, and EBECRYL860 (all manufactured by Daicel Allnex Corporation). However, commercially available oligomers are not limited to the above-mentioned commercially available products.

[0255] From the viewpoint of improving chemical resistance, UV printing durability, and suppression of on-press development residue, the content of the oligomer is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and particularly preferably 80% by mass to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0256] (Low molecular polymerizable compound) The polymerizable compound may further contain a polymerizable compound other than an oligomer. From the viewpoint of chemical resistance, the polymerizable compound other than an oligomer is preferably a low molecular weight polymerizable compound. The chemical form of the low molecular weight polymerizable compound may be a monomer, a dimer, a trimer, or a mixture thereof. From the viewpoint of chemical resistance, the low molecular weight polymerizable compound is preferably at least one selected from the group consisting of polymerizable compounds having three or more ethylenically unsaturated groups and polymerizable compounds having an isocyanuric ring structure.

[0257] In the present disclosure, the term "low molecular weight polymerizable compound" refers to a polymerizable compound having a molecular weight (weight average molecular weight when there is a molecular weight distribution) of 50 or more and less than 600. From the viewpoint of achieving excellent chemical resistance, UV 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 particularly preferably 400 or more and less than 600.

[0258] When the polymerizable compound contains, in addition to an oligomer, a low-molecular-weight polymerizable compound as a polymerizable compound other than the oligomer, from the viewpoints of chemical resistance, UV printing durability, and suppression of on-press development residue, the ratio of the oligomer content (the total amount, if the polymerizable compound contains two or more types of low-molecular-weight polymerizable compounds) to the low-molecular-weight polymerizable compound content (the total amount, if the polymerizable compound contains two or more types of low-molecular-weight polymerizable compounds) (i.e., oligomer / low-molecular-weight polymerizable compound) is preferably 10 / 1 to 1 / 10, more preferably 10 / 1 to 3 / 7, and particularly preferably 10 / 1 to 7 / 3, by mass.

[0259] As the polymerizable compound, the polymerizable compounds described in paragraphs 0082 to 0086 of WO 2019 / 013268 may be used. The contents of the above publications are incorporated herein by reference.

[0260] The image recording layer may contain one or more polymerizable compounds, and preferably contains two or more polymerizable compounds from the viewpoint of UV printing durability.

[0261] The content of the polymerizable compounds (total content of the polymerizable compounds when the image recording layer contains two or more types of polymerizable compounds) is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 70% by mass, and particularly preferably 15% by mass to 60% by mass, relative to the total mass of the image recording layer.

[0262] [particle] The image recording layer preferably contains particles from the viewpoints of developability and UV printing durability. The particles may be inorganic particles or organic particles. The image recording layer preferably contains organic particles as particles, and more preferably contains resin particles. For example, known inorganic particles can be used as the inorganic particles. For example, metal oxide particles (for example, silica particles or titania particles) can be used as the inorganic particles.

[0263] (resin particles) Examples of resin particles include particles containing an addition polymerization type resin (i.e., addition polymerization type resin particles), particles containing a polyaddition type resin (i.e., polyaddition type resin particles), and particles containing a polycondensation type resin (i.e., polycondensation type resin particles). As the resin particles, addition polymerization type resin particles or polyaddition type resin particles are preferred. From the viewpoint of enabling thermal fusion, the resin particles may also be particles containing a thermoplastic resin (i.e., thermoplastic resin particles).

[0264] The resin particles may be in the form of, for example, microcapsules or microgels (ie, crosslinked resin particles).

[0265] The resin particles are preferably at least one selected from the group consisting of thermoplastic resin particles, thermoreactive resin particles, resin particles having polymerizable groups, microcapsules encapsulating hydrophobic compounds, and microgels (crosslinked resin particles). Among these, resin particles having polymerizable groups are preferred. In a particularly preferred embodiment, the resin particles contain at least one ethylenically unsaturated group. Such resin particles have the effect of improving the printing durability of exposed areas and the on-press developability of unexposed areas.

[0266] -Thermoplastic resin particles- Preferred thermoplastic resin particles are those described in Research Disclosure No. 33303 of January 1992, JP-A Nos. 9-123387, 9-131850, 9-171249, 9-171250, or European Patent No. 931647.

[0267] Specific examples of resins constituting the thermoplastic resin particles include homopolymers or copolymers of monomers (e.g., ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, and acrylates or methacrylates having a polyalkylene structure), or mixtures thereof.

[0268] From the viewpoint of ink receptivity and UV printing durability, the thermoplastic resin particles preferably contain a resin having a structural unit formed from an aromatic vinyl compound and a structural unit having a nitrile group.

[0269] The aromatic vinyl compound may be any compound having a structure in which a vinyl group is bonded to an aromatic ring. Examples of the aromatic vinyl compound include styrene compounds and vinyl naphthalene compounds. Examples of the aromatic vinyl compound include styrene compounds, and more preferably styrene. Examples of the styrene compound include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene.

[0270] From the viewpoint of ink receptivity, the content of the structural unit formed by the aromatic vinyl compound is preferably greater than the content of the structural unit having a nitrile group, which will be described later. The content of the structural unit formed by the aromatic vinyl compound is more preferably 15% by mass to 85% by mass, and particularly preferably 30% by mass to 70% by mass, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles.

[0271] The structural unit having a nitrile group is preferably introduced using a monomer having a nitrile group. Examples of the monomer having a nitrile group include acrylonitrile compounds. A preferred example of the monomer having a nitrile group is (meth)acrylonitrile. The structural unit having a nitrile group is preferably a structural unit formed by (meth)acrylonitrile.

[0272] From the viewpoint of ink receptivity, the content of the structural unit having a nitrile group is preferably less than the content of the structural unit formed from an aromatic vinyl compound. The content of the structural unit having a nitrile group is preferably 55% by mass to 90% by mass, and more preferably 60% by mass to 85% by mass, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles.

[0273] When the thermoplastic resin particles contain a resin having a structural unit formed from an aromatic vinyl compound and a structural unit having a nitrile group, the content ratio of the structural unit formed from the aromatic vinyl compound to the structural unit having a nitrile group (i.e., structural unit formed from the aromatic vinyl compound:structural unit having a nitrile group) is preferably 5:5 to 9:1, and more preferably 6:4 to 8:2, on a mass basis.

[0274] From the viewpoint of UV printing durability and chemical resistance, the thermoplastic resin contained in the thermoplastic resin particles preferably further contains a structural unit formed by an N-vinyl heterocyclic compound. Examples of N-vinyl heterocyclic compounds include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylimidazole. Preferred N-vinyl heterocyclic compounds are N-vinylpyrrolidone.

[0275] The content of the structural unit formed by the N-vinyl heterocyclic compound is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 40% by mass, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles.

[0276] The thermoplastic resin contained in the thermoplastic resin particles may have a structural unit having an acidic group. However, from the viewpoint of on-press developability and ink receptivity, it is preferable that the thermoplastic resin contained in the thermoplastic resin particles does not have a structural unit having an acidic group. Specifically, the content of structural units having an acidic group in the thermoplastic resin is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles. The lower limit of the content is not limited and may be 0% by mass.

[0277] The acid value of the thermoplastic resin contained in the thermoplastic resin particles is preferably 160 mgKOH / g or less, more preferably 80 mgKOH / g or less, and particularly preferably 40 mgKOH / g or less. The lower limit of the acid value is not limited and may be 0 mgKOH / g. In the present disclosure, the acid value is determined by a measurement method in accordance with "JIS K0070:1992."

[0278] From the viewpoint of ink receptivity, the thermoplastic resin contained in the thermoplastic resin particles may have a structural unit containing a hydrophobic group. Examples of the hydrophobic group include an alkyl group, an aryl group, and an aralkyl group. As the structural unit containing a hydrophobic group, for example, a structural unit formed from an alkyl(meth)acrylate compound, an aryl(meth)acrylate compound, or an aralkyl(meth)acrylate compound is preferred, and a structural unit formed from an alkyl(meth)acrylate compound is more preferred.

[0279] The content of the structural unit having a hydrophobic group in the thermoplastic resin contained in the thermoplastic resin particles is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles.

[0280] From the viewpoints of UV printing durability and on-press developability, the thermoplastic resin contained in the thermoplastic resin particles preferably has a hydrophilic group. The hydrophilic group is not limited as long as it has a hydrophilic structure. Examples of the hydrophilic group include an acid group (e.g., a carboxy group), a hydroxy group, an amino group, a nitrile group, and a group having a polyalkylene oxide structure. From the viewpoints of UV printing durability and on-press developability, the hydrophilic group is preferably a group having a polyalkylene oxide structure, a group having a polyester structure, or a sulfonic acid group, more preferably a group having a polyalkylene oxide structure or a sulfonic acid group, and particularly preferably a group having a polyalkylene oxide structure.

[0281] From the viewpoint of on-press developability, the polyalkylene oxide structure is preferably a polyethylene oxide structure, a polypropylene oxide structure, or a poly(ethylene oxide / propylene oxide) structure.

[0282] From the viewpoint of on-press developability, the group having a polyalkylene oxide structure preferably has a polypropylene oxide structure, and more preferably has a polyethylene oxide structure or a polypropylene oxide structure.

[0283] From the viewpoint of on-press developability, the number of alkylene oxide structures in the polyalkylene oxide structure is preferably 2 or more, more preferably 5 or more, still more preferably 5 to 200, and particularly preferably 8 to 150.

[0284] The hydrophilic group is preferably a group represented by the following formula PO:

[0285] [ka]

[0286] During the expression PO, L P each independently represents an alkylene group; R P represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 100.

[0287] During the expression PO, L P are each independently preferably an ethylene group, a 1-methylethylene group, or a 2-methylethylene group, and more preferably an ethylene group.

[0288] In the formula PO, R P is preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, even more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom or a methyl group.

[0289] In the formula PO, n is preferably an integer of 1 to 10, and more preferably an integer of 1 to 4.

[0290] The content of the structural unit having a hydrophilic group is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles.

[0291] The resin contained in the thermoplastic resin particles may further have other structural units. Examples of the other structural units include structural units other than the above-mentioned structural units, such as a structural unit formed from an acrylamide compound or a vinyl ether compound.

[0292] The content of other structural units in the thermoplastic resin is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the thermoplastic resin in the thermoplastic resin particles.

[0293] -Thermal reactive resin particles- The thermoreactive resin particles include, for example, resin particles having a thermoreactive group, which form hydrophobic regions by crosslinking due to a thermal reaction and by changing the functional groups during crosslinking.

[0294] The thermally reactive group may be any functional group that undergoes any reaction as long as it forms a chemical bond, but is preferably a polymerizable group.Preferred thermally reactive groups include, for example, ethylenically unsaturated groups that undergo radical polymerization (e.g., acryloyl group, methacryloyl group, vinyl group, and allyl group), cationic polymerizable groups (e.g., vinyl group, vinyloxy group, epoxy group, and oxetanyl group), isocyanate groups or their block compounds that undergo addition reaction, epoxy groups, vinyloxy groups, and functional groups having active hydrogen atoms that are their reaction partners (e.g., amino group, hydroxy group, and carboxy group), carboxy groups that undergo condensation reaction, and hydroxy groups or amino groups that are their reaction partners, and acid anhydrides that undergo ring-opening addition reaction, and amino groups or hydroxy groups that are their reaction partners.

[0295] The resin having a thermally reactive group may be an addition polymerization type resin, a polyaddition type resin, or a polycondensation type resin. The resin having a thermally reactive group may be a thermoplastic resin.

[0296] -Microcapsules- As the microcapsules, for example, microcapsules encapsulating at least some of the components of the image recording layer (preferably hydrophobic compounds) are preferred, as described in JP-A Nos. 2001-277740 and 2001-277742. The image recording layer containing microcapsules as resin particles preferably encapsulates the hydrophobic components (i.e., hydrophobic compounds) of the components of the image recording layer in the microcapsules and contains the hydrophilic components (i.e., hydrophilic compounds) outside the microcapsules.

[0297] -Microgel- The microgel (crosslinked resin particles) can contain some of the components of the image recording layer on at least one of the surface and the interior of the microgel. In particular, reactive microgels having polymerizable groups on the surface of the microgel are preferred from the viewpoints of the sensitivity of the lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate. Known synthesis methods can be applied to obtain microcapsules containing the components of the image recording layer.

[0298] -Polyaddition type resin particles- From the viewpoint of the printing durability, stain resistance, and storage stability of the resulting lithographic printing plate, preferred resin particles are polyaddition type resin particles obtained by the reaction of a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in the molecule with isophorone diisocyanate, and a compound having active hydrogen.

[0299] The polyhydric phenol compound is preferably a compound having a plurality of benzene rings each having a phenolic hydroxy group.

[0300] The compound having active hydrogen is preferably a polyol compound or a polyamine compound, more preferably a polyol compound, and more preferably at least one selected from the group consisting of propylene glycol, glycerin, and trimethylolpropane.

[0301] Water can be used as the active hydrogen compound. When water is used as the active hydrogen compound, an amine produced by a reaction between an isocyanate group and water forms a urea bond, thereby forming particles.

[0302] Preferred examples of resin particles obtained by reacting a polyvalent isocyanate compound, which is an adduct of a polyhydric phenol compound having two or more hydroxy groups in the molecule with isophorone diisocyanate, with a compound having active hydrogen include the resin particles described in paragraphs 0230 to 0234 of WO 2018 / 043259.

[0303] From the viewpoints of printing durability, ink receptivity, on-press developability, and suppression of development residue during on-press development, the resin particles preferably contain a polyaddition resin having a urea bond, more preferably a polyaddition resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water, and particularly preferably a polyaddition resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water, and having a polyethylene oxide structure and a polypropylene oxide structure as the polyoxyalkylene structure. Furthermore, the particles containing a polyaddition resin having a urea bond are preferably microgels.

[0304] [ka]

[0305] In formula (Iso), n represents an integer of 0 to 10.

[0306] An example of the reaction between an isocyanate compound represented by formula (Iso) and water is the reaction shown below. Note that the reaction example shown below uses the 4,4-isomer, where n = 0. As shown below, when an isocyanate compound represented by formula (Iso) is reacted with water, a portion of the isocyanate groups is hydrolyzed by the water to generate amino groups, and the resulting amino groups react with the isocyanate groups to form urea bonds, forming dimers. Furthermore, the reaction shown below is repeated to form a polyaddition resin having a urea bond. In addition, by adding a compound reactive with an isocyanate group (i.e., a compound having active hydrogen: for example, an alcohol compound or an amine compound) to the reaction shown below, it is possible to introduce a structure such as an alcohol compound or an amine compound into a polyaddition resin having a urea bond. Preferred examples of the compound having active hydrogen include the compounds having active hydrogen described above.

[0307] [ka]

[0308] Furthermore, the polyaddition resin having a urea bond preferably has an ethylenically unsaturated group, and more preferably has a group represented by the following formula (PETA).

[0309] [ka]

[0310] In formula (PETA), the wavy line indicates the bonding position to other structures.

[0311] -Addition polymerization type resin particles- From the viewpoint of the printing durability and solvent resistance of the resulting lithographic printing plate, the resin particles are preferably addition-polymerized resin particles having a hydrophobic main chain and including both i) a constituent unit having a nitrile group directly bonded to the hydrophobic main chain and ii) a constituent unit having a pendant group containing a hydrophilic polyalkylene oxide segment. Specifically, the particles described in paragraph 0156 of JP-A-2019-64269 are preferred.

[0312] -A group represented by the formula Z- The resin particles preferably have a group represented by the following formula Z as a hydrophilic group. *-QWY :Formula Z

[0313] In Formula Z, Q represents a divalent linking group, W represents a divalent group having a hydrophilic structure or a divalent group having a hydrophobic structure, Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophobic structure, one of W and Y has a hydrophilic structure, and * represents a bonding site to another structure. It is preferable that one of the hydrophilic structures included in Formula Z contains a polyalkylene oxide structure.

[0314] Q in formula Z is preferably a divalent linking group having 1 to 20 carbon atoms, and more preferably a divalent linking group having 1 to 10 carbon atoms.

[0315] Q in formula Z is preferably an alkylene group, an arylene group, an ester bond, an amide bond, or a group consisting of a combination of two or more of these, and more preferably a phenylene group, an ester bond, or an amide bond.

[0316] The divalent group having a hydrophilic structure in W of formula Z is preferably a group having a polyalkylene oxide structure, and is preferably a polyalkyleneoxy group or a group having -CH2CH2NR at one end of the polyalkyleneoxy group. W Preferably, R is a group to which - is bonded. W represents a hydrogen atom or an alkyl group.

[0317] The divalent group having a hydrophobic structure in W of formula Z is -R WA -, -OR WA -O-, -R W NR WA -NR W -, -OC(=O)-R WA -O- or -OC(=O)-R WA -O- is preferred. WA R each independently represents a linear, branched, or cyclic alkylene group having 6 to 120 carbon atoms, a haloalkylene group having 6 to 120 carbon atoms, an arylene group having 6 to 120 carbon atoms, an alkylylene group having 7 to 120 carbon atoms (i.e., a divalent group obtained by removing one hydrogen atom from an alkylaryl group), or an aralkylene group having 7 to 120 carbon atoms. W represents a hydrogen atom or an alkyl group.

[0318] The monovalent group having a hydrophilic structure represented by Y in formula Z is -OH, -C(=O)OH, a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the end, or a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the other end and -CH2CH2N(R WThe monovalent group having a hydrophilic structure is preferably a monovalent group having a polyalkylene oxide structure, and is preferably a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the end, or a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the other end and having -CH 2 CH 2 N(R W A group having a bonded )- is preferred. W represents a hydrogen atom or an alkyl group.

[0319] The monovalent group having a hydrophobic structure for Y in formula Z is a linear, branched, or cyclic alkyl group having 6 to 120 carbon atoms, a haloalkyl group having 6 to 120 carbon atoms, an aryl group having 6 to 120 carbon atoms, an alkaryl group (alkylaryl group) having 7 to 120 carbon atoms, an aralkyl group having 7 to 120 carbon atoms, -OR WB , -C(=O)OR WB , or -OC(=O)R WB It is preferable that R WB represents an alkyl group having 6 to 20 carbon atoms.

[0320] In resin particles having a group represented by formula Z, from the viewpoints of printing durability, ink receptivity, and on-press developability, W is preferably a divalent group having a hydrophilic structure, Q is more preferably a phenylene group, an ester bond, or an amide bond, W is a polyalkyleneoxy group, and Y is more preferably a polyalkyleneoxy group whose terminal is a hydrogen atom or an alkyl group. The group represented by formula Z may function as a dispersing group that enhances the dispersibility of the resin particles.

[0321] -Resin particles with polymerizable groups- From the viewpoint of printing durability and on-press developability, the resin particles preferably have a polymerizable group (preferably an ethylenically unsaturated group), and more preferably contain resin particles having a polymerizable group on the surface. By using resin particles having a polymerizable group, plate skipping (preferably UV plate skipping) can be easily suppressed and printing durability (preferably UV printing durability) can also be improved.

[0322] From the viewpoint of printing durability, the resin particles are preferably resin particles having a hydrophilic group and a polymerizable group. The polymerizable group may be a cationically polymerizable group or a radically polymerizable group, but from the viewpoint of reactivity, a radically polymerizable group is preferable. The polymerizable group is not particularly limited as long as it is a polymerizable group, but from the viewpoint of reactivity, an ethylenically unsaturated group is preferable, a vinylphenyl group (styryl group), a (meth)acryloxy group, or a (meth)acrylamide group is more preferable, and a (meth)acryloxy group is particularly preferable. Furthermore, the resin constituting the resin particles having a polymerizable group preferably has a structural unit having a polymerizable group. Incidentally, a polymerizable group may be introduced onto the surface of the resin particles by a polymer reaction.

[0323] -Synthesis of resin particles- The synthesis method of the resin particles is not particularly limited, and any method capable of synthesizing particles from the various resins described above may be used. Examples of the synthesis method of the resin particles include known synthesis methods for resin particles, such as emulsion polymerization, suspension polymerization, dispersion polymerization, soap-free polymerization, and microemulsion polymerization. The synthesis of the resin particles may also be performed using known synthesis methods for microcapsules or known synthesis methods for microgels (crosslinked resin particles).

[0324] (average particle size) The average particle size of the particles is preferably 0.01 μm to 3.0 μm, more preferably 0.03 μm to 2.0 μm, and particularly preferably 0.10 μm to 1.0 μm. By setting the average particle size within the above range, good resolution and stability over time can be obtained. The average particle size of the particles is measured by a light scattering method, or by taking an electron microscope photograph of the particles, measuring the particle sizes of a total of 5,000 particles on the photograph, and calculating the average. For non-spherical particles, the circle-equivalent diameter of the particles on the photograph is taken. The average particle size of the particles in this disclosure is the volume-average particle size unless otherwise specified.

[0325] (particle content) The image recording layer may contain one type of particle or two or more types of particles. From the viewpoints of developability and printing durability, the content of particles (preferably resin particles) is preferably 5% by mass to 90% by mass, more preferably 10% by mass to 90% by mass, even more preferably 20% by mass to 90% by mass, and particularly preferably 50% by mass to 90% by mass, relative to the total mass of the image recording layer.

[0326] [Color-forming compound] The image recording layer preferably contains a color former capable of undergoing a color reaction with a decomposition product produced by exposure of the image recording layer. Preferred color formers include, for example, compounds represented by Formula 1C and Formula 2C, which will be described later. In the present disclosure, "color reaction" refers to a chemical reaction accompanied by a color development or color change phenomenon.

[0327] The decomposition product generated by exposure of the image recording layer is not particularly limited, but from the viewpoint of visibility of the exposed area, it is preferably a decomposition product of a polymerization initiator or a decomposition product of an infrared absorber, more preferably a decomposition product of a polymerization initiator, and particularly preferably a decomposition product of an electron-donating polymerization initiator. The decomposition product generated by exposure of the image recording layer includes not only decomposition products generated by exposure but also compounds generated by further decomposition or modification of the decomposition products generated by exposure.

[0328] From the viewpoint of visibility of the exposed area, the color reaction is preferably a complex formation reaction, and more preferably a boron complex formation reaction. An example of a color reaction is shown below. The color reaction shown below shows a reaction between curcumin as a color-forming compound and boric acid produced by decomposition of sodium tetraphenylborate (TPB), a decomposition product resulting from exposure of the image recording layer. Curcumin produces an enol form in equilibrium due to keto-enol tautomerism. The reaction of the enol form with boric acid produces a boron complex, resulting in a color reaction from curcumin (yellow) to the boron complex (red). While the color reaction shown below shows an example in which TPB is hydrolyzed to boric acid, for example, diphenylmonohydroxyborane, monophenyldihydroxyborane, etc. may form a complex with curcumin, or triphenylborane may coordinate to the enol form of curcumin as a zero-valent ligand to form a complex.

[0329] [ka]

[0330] From the viewpoints of visibility of exposed areas and tone reproducibility, the color-forming compound is preferably a compound having one or more ketone structures, more preferably a compound having one or more 1,3-diketone structures, β-hydroxyketone structures, or β-aminoketone structures, even more preferably a compound having one or more 1,3-diketone structures or β-hydroxyketone structures, and particularly preferably a compound having one or more 1,3-diketone structures.

[0331] The color former also includes compounds having one or more 1-hydroxy-3-amino structures or 1-hydroxy-3-imino structures.

[0332] From the viewpoints of visibility of exposed areas and tone reproducibility, the color former is preferably a compound having an aromatic ring structure, more preferably a compound having two or more aromatic ring structures, even more preferably a compound having two to four aromatic ring structures, and particularly preferably a compound having two aromatic ring structures. From the viewpoints of visibility of exposed areas and tone reproducibility, the aromatic ring structure is preferably at least one selected from the group consisting of a benzene ring structure and a naphthalene ring structure, and more preferably a benzene ring structure.

[0333] The color former may be a salt or a hydrate.

[0334] In the color reaction, when a complex is formed by reaction between the color former and a decomposition product generated by exposure of the image recording layer, the color former may form a ligand of the complex. The ligand may be a monodentate or polydentate ligand. From the viewpoints of complex formation ability, visibility of the exposed area, and tone reproducibility, the ligand is preferably a polydentate ligand, more preferably a bidentate, tridentate, tetradentate, pentadentate, or hexadentate ligand, still more preferably a bidentate, tridentate, or tetradentate ligand, particularly preferably a bidentate or tridentate ligand, and most preferably a bidentate ligand.

[0335] The image recording layer preferably contains a compound represented by the following formula 1C or a compound represented by the following formula 2C as a color former, and more preferably contains a compound represented by the following formula 1C: After exposure, the compound represented by the following formula 1C or the compound represented by the following formula 2C reacts with decomposition products generated by exposure of the image recording layer to form a complex having the compound represented by the following formula 1C or the compound represented by the following formula 2C as a zero-valent ligand, or an anion obtained by removing one hydrogen atom from the compound represented by the following formula 1C or the compound represented by the following formula 2C as a monovalent ligand, and more preferably the compound represented by the following formula 1C or the compound represented by the following formula 2C reacts with decomposition products generated by exposure of the image recording layer to form a complex having the anion obtained by removing one hydrogen atom from the compound represented by the following formula 1C or the compound represented by the following formula 2C as a monovalent ligand.

[0336] [ka]

[0337] In Formula 1C and Formula 2C, R 1C ~R 4C each independently represents a monovalent organic group; L 1C and L 2C each independently represents a divalent organic group; A C is OH or NR 5C R 6C represents R 5C and R 6C each independently represents a hydrogen atom or a monovalent organic group, and the dotted line represents a moiety which may be a double bond.

[0338] In Formula 1C, R 1C , L 1C , and R 2C Two or more of R may be bonded to form a ring structure. 3C , L 2C , R 4C , R 5C , and R 6C Two or more of these may be bonded to form a ring structure.

[0339] From the viewpoint of visibility of the exposed area and tone reproducibility, R in Equation 1C 1C and R 2C are each independently preferably a monovalent organic group having an aromatic ring, more preferably an aryl group or an alkenyl group having an aryl group, and particularly preferably a 2-arylvinyl group. The aryl group may have a substituent, and from the viewpoints of visibility of exposed areas and tone reproducibility, is preferably an aryl group having one or more substituents selected from the group consisting of hydroxy groups and alkoxy groups, more preferably a phenyl group having one or more substituents selected from the group consisting of hydroxy groups and alkoxy groups, and particularly preferably a phenyl group having one or more substituents selected from the group consisting of hydroxy groups and alkoxy groups.

[0340] R in Equation 1C 1C and R 2C The carbon number (number of carbon atoms) of each is independently preferably 6 to 50, more preferably 6 to 20, and particularly preferably 8 to 20.

[0341] R in Equation 1C 1C and R 2C are preferably the same group.

[0342] L in Equation 1C 1C From the viewpoints of visibility of exposed areas and tone reproducibility, is preferably an alkylene group or an alkylene group having an acyloxy group, more preferably a methylene group or an acyloxymethylene group. From the viewpoint of visibility of exposed areas, the acyloxy group is preferably an acyloxy group having 1 to 10 carbon atoms, more preferably an acyloxy group having 1 to 4 carbon atoms, and particularly preferably an acetoxy group.

[0343] R in Equation 2C 3CFrom the viewpoints of visibility of exposed areas and tone reproducibility, is preferably a monovalent organic group having an aromatic ring, and more preferably an aryl group or an alkenyl group having an aryl group.

[0344] In Equation 2C, from the viewpoint of visibility of the exposed area and tone reproducibility, L 2C and R 4C and preferably bond to form an aromatic ring, and L 2C and R 4C and more preferably bond to form a benzene ring.

[0345] R in Equation 2C 3C and R 4C The number of carbon atoms in each of the groups is preferably 6 to 50, more preferably 6 to 30, and particularly preferably 6 to 20.

[0346] L in Equation 2C 2C is R 4C When the acyloxy group is not bonded to the methyl group, from the viewpoints of visibility of the exposed area and tone reproducibility, the methyl group is preferably an alkylene group or an alkylene group having an acyloxy group, and more preferably a methylene group or an acyloxymethylene group. From the viewpoint of visibility of the exposed area, the acyloxy group is preferably an acyloxy group having 1 to 10 carbon atoms, more preferably an acyloxy group having 1 to 4 carbon atoms, and particularly preferably an acetoxy group.

[0347] L in Equation 2C 2C is R 4C and preferably bonds to form a ring member of an aromatic ring structure.

[0348] From the viewpoints of visibility of exposed areas and tone reproducibility, the compound represented by Formula 2C is preferably a compound having a 1-hydroxyanthraquinone structure or a 1-aminoanthraquinone structure, and more preferably a compound having a 1-hydroxyanthraquinone structure.

[0349] A in Equation 2C CFrom the viewpoint of visibility of exposed areas and tone reproduction, OH or NHR 6C is preferred, and OH is more preferred.

[0350] NR in Equation 2C 5C R 6C R in 5C is preferably a hydrogen atom, an alkyl group, or an aryl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.

[0351] NR in Equation 2C 5C R 6C R in 6C is preferably a hydrogen atom, an alkyl group, or an anthraquinolyl group, more preferably an anthraquinolyl group, and particularly preferably a 1-anthraquinolyl group.

[0352] Preferred color formers include curcumin, demethoxycurcumin, alizarin, iminodianthraquinone, carminic acid, azomethine H, 1,3-bis(4-methoxyphenyl)-1,3-propanedione, 4-methoxychalcone, 1,3-bis(4-dimethylaminophenyl)-1,3-propanedione, and acetoxycurcumin.

[0353] The image recording layer may contain one or more color formers. The image recording layer may contain one or more compounds represented by formula 1C. The image recording layer may contain one or more compounds represented by formula 2C. The complex formed by the color former reaction may be one or more.

[0354] From the viewpoint of visibility of exposed areas and tone reproducibility, the content of the color former is preferably 0.001% by mass to 5% by mass, more preferably 0.01% by mass to 3% by mass, even more preferably 0.05% by mass to 2.5% by mass, and particularly preferably 0.05% by mass to 1.0% by mass, relative to the total mass of the image recording layer.

[0355] From the viewpoints of visibility of exposed areas and tone reproducibility, the content of the compound represented by Formula 1C and the compound represented by Formula 2C is preferably 0.001% by mass to 5% by mass, more preferably 0.01% by mass to 3% by mass, even more preferably 0.05% by mass to 2.5% by mass, and particularly preferably 0.05% by mass to 1.0% by mass, relative to the total mass of the image recording layer.

[0356] From the viewpoint of visibility of the exposed area and tone reproducibility, an energy density of 110 mJ / cm 2 The content of the complex in the image recording layer exposed to infrared light having a wavelength of 830 nm at 1000 W / m is preferably 0.0001% by mass to 10% by mass, more preferably 0.001% by mass to 5% by mass, even more preferably 0.005% by mass to 2.5% by mass, and particularly preferably 0.005% by mass to 1.0% by mass, relative to the total mass of the image recording layer.

[0357] Content M of polymerization initiator in image recording layer I The content M of the color former (preferably the compound represented by formula 1C and the compound represented by formula 2C) in the image recording layer relative to C The molar ratio of (i.e., M C / M I ) is preferably 0.001 to 1, more preferably 0.01 to 0.8, and particularly preferably 0.05 to 0.5.

[0358] Content M of electron-donating polymerization initiator in image recording layer DI The content M of the color former (preferably the compound represented by formula 1C and the compound represented by formula 2C) in the image recording layer relative to C The molar ratio of C / M DI ) is preferably 0.001 to 1.5, more preferably 0.01 to 1, and particularly preferably 0.05 to 0.8.

[0359] [Other ingredients] The image recording layer may contain other components in addition to the components already described, such as a binder polymer, a color former, a chain transfer agent, a low-molecular-weight hydrophilic compound, an oil sensitizer, a plasticizer, and other additives.

[0360] (binder polymer) The image recording layer may contain a binder polymer, if necessary. In the present disclosure, the term "binder polymer" refers to a polymer other than resin particles, i.e., a polymer that is not in particle form. Ammonium salt-containing polymers in oil sensitizers and polymers used as surfactants are excluded from the binder polymer.

[0361] As the binder polymer, known binder polymers (e.g., (meth)acrylic resins, polyvinyl acetal resins, and polyurethane resins) used in the image recording layer of a lithographic printing plate precursor can be suitably used. Hereinafter, as an example of the binder polymer, a binder polymer used in an on-press development type lithographic printing plate precursor (hereinafter also referred to as an on-press development binder polymer) will be described in detail.

[0362] As the binder polymer for on-press development, a binder polymer having an alkylene oxide chain is preferred. The binder polymer having an alkylene oxide chain may have a poly(alkylene oxide) moiety in the main chain or side chain. Furthermore, the binder polymer having an alkylene oxide chain may be a graft polymer having a poly(alkylene oxide) in the side chain, or a block copolymer of a block composed of a poly(alkylene oxide)-containing repeating unit and a block composed of a non-(alkylene oxide)-containing repeating unit. When the binder polymer has a poly(alkylene oxide) moiety in the main chain, a polyurethane resin is preferred. When the binder polymer has a poly(alkylene oxide) moiety in the side chain, examples of the main chain polymer include (meth)acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, polystyrene resin, novolac-type phenolic resin, polyester resin, synthetic rubber, and natural rubber, with (meth)acrylic resin being particularly preferred.

[0363] A preferred example of the binder polymer is a polymer compound (hereinafter also referred to as a star-shaped polymer compound) having a 6- to 10-functional polyfunctional thiol core, polymer chains bonded to the core by sulfide bonds, and the polymer chains having polymerizable groups. As the star-shaped polymer compound, for example, the compounds described in JP 2012-148555 A can be preferably used.

[0364] Examples of star-shaped polymer compounds include compounds having a polymerizable group such as an ethylenically unsaturated bond in the main chain or side chain, preferably in the side chain, for improving the film strength in the image area, as described in JP-A-2008-195018. The polymerizable group in the star-shaped polymer compound forms crosslinks between molecules of the star-shaped polymer compound, accelerating curing.

[0365] The polymerizable group is preferably an ethylenically unsaturated group (e.g., (meth)acrylic group, vinyl group, allyl group, and vinylphenyl group (styryl group)) or an epoxy group, with the (meth)acrylic group, vinyl group, or vinylphenyl group (styryl group) being more preferred from the viewpoint of polymerization reactivity, and the (meth)acrylic group being particularly preferred. These groups can be introduced into the binder polymer by polymer reaction or copolymerization. Specifically, for example, a reaction between a polymer having a carboxy group in the side chain and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be utilized.

[0366] The weight average molecular weight (Mw) of the binder polymer, which is a polystyrene equivalent value measured by the GPC method, is preferably 2,000 or more, more preferably 5,000 or more, and particularly preferably 10,000 to 300,000.

[0367] As the binder polymer, a hydrophilic polymer such as polyacrylic acid or polyvinyl alcohol described in JP-A-2008-195018 can be used in combination, if necessary. Also, a lipophilic polymer and a hydrophilic polymer can be used in combination.

[0368] The image recording layer may contain one or more binder polymers.

[0369] The content of the binder polymer is preferably from 1% by mass to 90% by mass, and more preferably from 5% by mass to 80% by mass, based on the total mass of the image recording layer.

[0370] (color former) The image recording layer preferably contains a color former, more preferably an acid color former, and more preferably a leuco compound (also called a leuco dye) as the color former.

[0371] In the present disclosure, the term "color former" refers to a compound that develops or loses color upon stimulation with, for example, light or acid, thereby changing the color of the image recording layer.

[0372] In the present disclosure, the term "acid color former" refers to a compound that has the property of developing or decolorizing a color when heated in a state in which it accepts an electron-accepting compound (e.g., a proton of an acid, etc.), thereby changing the color of the image recording layer. Preferred examples of acid color formers include colorless compounds that have a partial skeleton such as a lactone, lactam, sultone, spiropyran, ester, or amide, and that rapidly open or cleave this partial skeleton when brought into contact with an electron-accepting compound.

[0373] Examples of acid color formers include the compounds described in paragraphs 0184 to 0191 of JP-A-2019-18412.

[0374] From the viewpoint of color development, the color former is preferably at least one selected from the group consisting of spiropyran compounds, spirooxazine compounds, spirolactone compounds, and spirolactam compounds.

[0375] From the viewpoint of visibility, the color of the dye after color development preferably has a maximum absorption in the range of 450 nm to 650 nm, and the color is preferably red, purple, blue, or black-green.

[0376] From the viewpoints of color development and visibility of exposed areas, the acid color former is preferably a leuco dye. The leuco dye is not particularly limited as long as it is a dye having a leuco structure, but it is preferably a leuco dye having a spiro structure, and more preferably a spirolactone ring structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure. From the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is preferably a compound represented by any one of the following formulas (Le-1) to (Le-3), and more preferably a compound represented by the following formula (Le-2).

[0377] [ka]

[0378] In formulae (Le-1) to (Le-3), ERG each independently represents an electron-donating group, X1 to X4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, and X5 to X 10 each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group; Y1 and Y2 each independently represent C or N; when Y1 is N, X1 is not present; when Y2 is N, X4 is not present; Ra1 represents a hydrogen atom, an alkyl group, or an alkoxy group; and Rb1 to Rb4 each independently represent a hydrogen atom, an alkyl group, or an aryl group.

[0379] From the viewpoints of color development and visibility of exposed areas, the electron-donating group in ERG of Formulae (Le-1) to (Le-3) is preferably an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, an alkoxy group, an aryloxy group, or an alkyl group, more preferably an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, an alkoxy group, or an aryloxy group, still more preferably an arylamino group, a monoalkylmonoarylamino group, or a diarylamino group, and particularly preferably an arylamino group or a monoalkylmonoarylamino group.

[0380] From the viewpoint of color development and visibility of exposed areas, X1 to X4 in formulae (Le-1) to (Le-3) are each preferably independently a hydrogen atom or a chlorine atom, and more preferably a hydrogen atom.

[0381] From the viewpoint of color development and visibility of exposed areas, X5 to X in formula (Le-2) or formula (Le-3) 10are each independently preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, or a cyano group, more preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group, still more preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and particularly preferably a hydrogen atom.

[0382] From the viewpoint of color development and visibility of exposed areas, at least one of Y1 and Y2 in formulae (Le-1) to (Le-3) is preferably C, and both Y1 and Y2 are more preferably C.

[0383] From the viewpoint of color development and visibility of exposed areas, Ra1 in formula (Le-3) is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group.

[0384] From the viewpoint of color development and visibility of exposed areas, Rb1 to Rb4 in formula (Le-1) are each preferably independently a hydrogen atom or an alkyl group, more preferably an alkyl group, and particularly preferably a methyl group.

[0385] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is preferably a compound represented by any one of the following formulas (Le-4) to (Le-6), and more preferably a compound represented by the following formula (Le-5).

[0386] [ka]

[0387] In formulas (Le-4) to (Le-6), ERG each independently represents an electron-donating group, X1 to X4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group, Y1 and Y2 each independently represent C or N, and when Y1 is N, X1 is not present, and when Y2 is N, X4 is not present, Ra1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and Rb1 to Rb4 each independently represent a hydrogen atom, an alkyl group, or an aryl group.

[0388] ERG, X1 to X4, Y1, Y2, Ra1, and Rb1 to Rb4 in formulae (Le-4) to (Le-6) have the same meanings as ERG, X1 to X4, Y1, Y2, Ra1, and Rb1 to Rb4 in formulae (Le-1) to (Le-3), respectively, and preferred embodiments are also the same.

[0389] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is preferably a compound represented by any one of the following formulas (Le-7) to (Le-9), and more preferably a compound represented by the following formula (Le-8).

[0390] [ka]

[0391] In formulas (Le-7) to (Le-9), X1 to X4 each independently represent a hydrogen atom, a halogen atom, or a dialkylanilino group; Y1 and Y2 each independently represent C or N; when Y1 is N, X1 is not present; when Y2 is N, X4 is not present; Ra1 to Ra4 each independently represent a hydrogen atom, an alkyl group, or an alkoxy group; Rb1 to Rb4 each independently represent a hydrogen atom, an alkyl group, or an aryl group; and Rc1 and Rc2 each independently represent an aryl group.

[0392] X1 to X4, Y1, and Y2 in formulae (Le-7) to (Le-9) have the same meanings as X1 to X4, Y1, and Y2 in formulae (Le-1) to (Le-3), respectively, and the preferred embodiments are also the same.

[0393] From the viewpoint of color development and visibility of exposed areas, Ra1 to Ra4 in formula (Le-7) are each preferably independently an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group.

[0394] From the viewpoint of color development and visibility of exposed areas, Rb1 to Rb4 in formulas (Le-7) to (Le-9) are each preferably independently a hydrogen atom, an alkyl group, or an aryl group substituted with an alkyl group or an alkoxy group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom or a methyl group.

[0395] From the viewpoint of color development and visibility of exposed areas, Rc1 and Rc2 in formula (Le-8) are each preferably independently a phenyl group or an alkylphenyl group, and more preferably a phenyl group.

[0396] In terms of color development and visibility of exposed areas, it is preferred that X1 to X4 are hydrogen atoms, and Y1 and Y2 are carbon atoms in formula (Le-8).

[0397] From the viewpoint of color development and visibility of exposed areas, in formula (Le-8), Rb1 and Rb2 are each preferably independently a hydrogen atom, an alkyl group, or an aryl group substituted with an alkyl group or an alkoxy group, and more preferably a hydrogen atom or an alkyl group.

[0398] The alkyl group in formulas (Le-1) to (Le-9) may be linear or branched. The alkyl group in formulas (Le-1) to (Le-9) may have a ring structure.

[0399] The alkyl group in formulae (Le-1) to (Le-9) preferably has 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, even more preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms.

[0400] The aryl group in formulae (Le-1) to (Le-9) preferably has 6 to 20 carbon atoms, more preferably 6 to 10 carbon atoms, and particularly preferably 6 to 8 carbon atoms.

[0401] Each group in Formulae (Le-1) to (Le-9) (e.g., a monovalent organic group, an alkyl group, an aryl group, a dialkylanilino group, an alkylamino group, and an alkoxy group) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a cyano group. The substituent may be further substituted with the above-mentioned substituent.

[0402] Suitable leuco dyes having a phthalide structure or a fluoran structure include the following compounds:

[0403] [ka]

[0404] [ka]

[0405] [ka]

[0406] [ka]

[0407]

change

[0408]

change

[0409]

change

[0410]

change

[0411] As the acid color former, commercially available products (i.e., commercial products) can be used, such as ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H-3035, BLUE203, ATP, H-1046, and H-2114 (all manufactured by Fukui Yamada Chemical Co., Ltd.), ORANGE-DCF, Vermilion-DCF, and PINK-D. Examples of suitable dyes include CF, RED-DCF, BLMB, CVL, GREEN-DCF, and TH-107 (all manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green-118, Red-40, and Red-8 (all manufactured by Yamamoto Chemical Industry Co., Ltd.), and crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.). Among these commercially available products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63, GN-169, and crystal violet lactone are preferred because the films formed have good visible light absorptance.

[0412] As leuco dyes that are preferably used, the following compounds can be mentioned from the viewpoints of color development and visibility of exposed areas.

[0413] [ka]

[0414] The image recording layer may contain one or more color formers, and the content of the color former is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass, relative to the total mass of the image recording layer.

[0415] (chain transfer agents, low molecular weight hydrophilic compounds, oil sensitizers, and other additives) Components that can be used in the image recording layer are described, for example, in paragraph 0082 of JP-A-2019-162855, the disclosure of which is incorporated herein by reference.

[0416] [Formation method] The image recording layer can be formed by a known method (for example, a coating method). The coating amount (solid content) of the image recording layer is 100 mg / m 2 ~3,000mg / m 2 is preferably 300 mg / m 2 ~1,500mg / m 2 It is more preferable that:

[0417] << Undercoat layer >> The on-press development type lithographic printing plate precursor according to one embodiment of the present disclosure preferably has an undercoat layer between the image recording layer and the support. In technical fields related to the present disclosure, the undercoat layer is sometimes referred to as an intermediate layer. The undercoat layer strengthens adhesion between the support and the image recording layer in the exposed areas of the undercoat layer, and facilitates peeling of the image recording layer from the support in the unexposed areas of the undercoat layer. This contributes to improving developability without impairing printing durability. Furthermore, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, preventing heat generated by exposure from diffusing to the support and reducing sensitivity.

[0418] Examples of compounds contained in the undercoat layer include polymers having an adsorptive group and a hydrophilic group that can be adsorbed to the support surface. In order to improve adhesion to the image recording layer, the compound contained in the undercoat layer is preferably a polymer having an adsorptive group and a hydrophilic group and further having a crosslinkable group. The compound contained in the undercoat layer may be a low molecular weight compound or a polymer. Two or more compounds may be mixed and used as needed.

[0419] When the compound contained in the undercoat layer is a polymer, the polymer is preferably a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group.

[0420] The adsorptive group is preferably a phenolic hydroxy group, a carboxy group, -PO3H2, -OPO3H2, -CONHSO2-, -SO2NHSO2-, or -COCH2COCH3.

[0421] The hydrophilic group is preferably a sulfo group or a salt thereof, or a salt of a carboxy group.

[0422] The crosslinkable group is preferably an acrylic group, a methacrylic group, an acrylamide group, a methacrylamide group, or an allyl group.

[0423] The polymer may have a crosslinkable group introduced by salt formation between a polar substituent of the polymer and a compound having an ethylenically unsaturated bond and a substituent having an opposite charge to the polar substituent. The polymer may further be copolymerized with a monomer other than the above, preferably a hydrophilic monomer.

[0424] Specifically, preferred examples include silane coupling agents having an addition-polymerizable ethylenic double bond reactive group as described in JP-A-10-282679, and phosphorus compounds having an ethylenic double bond reactive group as described in JP-A-2-304441. Also preferred are low-molecular-weight or high-molecular-weight compounds having a crosslinkable group (preferably an ethylenically unsaturated bond group) as described in JP-A-2005-238816, JP-A-2005-125749, JP-A-2006-239867, and JP-A-2006-215263, as well as functional groups that interact with the support surface and hydrophilic groups. More preferred examples include high-molecular-weight polymers having adsorptive groups, hydrophilic groups, and crosslinkable groups that can be adsorbed onto the support surface as described in JP-A-2005-125749 and JP-A-2006-188038.

[0425] The content of ethylenically unsaturated bond groups in the polymer contained in the undercoat layer is preferably 0.1 mmol to 10.0 mmol, and more preferably 0.2 mmol to 5.5 mmol, per 1 g of polymer.

[0426] The weight average molecular weight (Mw) of the polymer contained in the undercoat layer is preferably 5,000 or more, and more preferably 10,000 to 300,000.

[0427] [Hydrophilic compound] From the viewpoint of developability, the undercoat layer preferably contains a hydrophilic compound. As the hydrophilic compound, for example, known hydrophilic compounds used in undercoat layers can be used.

[0428] Preferred hydrophilic compounds include, for example, carboxymethyl cellulose, phosphonic acids having an amino group such as dextrin, organic phosphonic acids, organic phosphoric acids, organic phosphinic acids, amino acids, and hydrochlorides of amines having a hydroxy group.

[0429] Other preferred hydrophilic compounds include compounds having an amino group or a functional group having polymerization-inhibiting ability and a group that interacts with the support surface (e.g., 1,4-diazabicyclo[2.2.2]octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, ethylenediaminetetraacetic acid (EDTA) or a salt thereof, hydroxyethylethylenediaminetriacetic acid or a salt thereof, dihydroxyethylethylenediaminediacetic acid or a salt thereof, and hydroxyethyliminodiacetic acid or a salt thereof).

[0430] From the viewpoint of scratch and stain prevention, the undercoat layer preferably contains a hydroxycarboxylic acid or a salt thereof as a hydrophilic compound.

[0431] In the present disclosure, the term "hydroxycarboxylic acid" is a general term for organic compounds having one or more carboxy groups and one or more hydroxy groups in one molecule, and is also called a hydroxy acid, an oxy acid, an oxycarboxylic acid, or an alcohol acid (see Iwanami Dictionary of Physics and Chemistry, 5th Edition, published by Iwanami Shoten Co., Ltd. (1998)).

[0432] The hydroxycarboxylic acid or a salt thereof is preferably represented by the following formula (HC): R HC (OH) mhc (COOM HC ) nhc :Formula(HC)

[0433] In formula (HC), R HC represents an organic group with a valence of mhc+nhc, and M HC each independently represents a hydrogen atom, an alkali metal, or an onium; mhc and nhc each independently represent an integer of 1 or more; when nhc is 2 or more, M may be the same or different.

[0434] In formula (HC), R HCExamples of the mhc+nhc valent organic group represented by the formula (1) include mhc+nhc valent hydrocarbon groups. The hydrocarbon group may have a substituent and / or a linking group. Examples of the hydrocarbon group include mhc+nhc valent groups derived from aliphatic hydrocarbons (e.g., alkylene groups, alkanetriyl groups, alkanetetrayl groups, alkanpentyl groups, alkenylene groups, alkenetriyl groups, alkenetetrayl groups, alkenepentyl groups, alkynylene groups, alkyntriyl groups, alkyntetrayl groups, and alkynpentyl groups), and mhc+nhc valent groups derived from aromatic hydrocarbons (e.g., arylene groups, arenetriyl groups, arenetetrayl groups, and arenepentyl groups). Examples of the substituent include alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, and aryl groups. Specific examples of the substituent include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, a 2-norbornyl group, a methoxymethyl group, a methoxyethoxyethyl group, an allyloxymethyl group, a phenoxymethyl group, an acetyloxymethyl group, a benzoyloxymethyl group, Examples of the alkyl group include an alkyl group, a benzyl group, a phenethyl group, an α-methylbenzyl group, a 1-methyl-1-phenylethyl group, a p-methylbenzyl group, a cinnamyl group, an allyl group, a 1-propenylmethyl group, a 2-butenyl group, a 2-methylallyl group, a 2-methylpropenylmethyl group, a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a phenyl group, a biphenyl group, a naphthyl group, a tolyl group, a xylyl group, a mesityl group, a cumenyl group, a methoxyphenyl group, an ethoxyphenyl group, a phenoxyphenyl group, an acetoxyphenyl group, a benzoyloxyphenyl group, a methoxycarbonylphenyl group, an ethoxycarbonylphenyl group, and a phenoxycarbonylphenyl group.The linking group is a linking group constituted by at least one atom selected from the group consisting of hydrogen atoms, carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms. The number of atoms in the linking group is preferably 1 to 50. Specific examples of the linking group include alkylene groups, substituted alkylene groups, arylene groups, and substituted arylene groups. The linking group may have a structure in which a plurality of the above-mentioned divalent groups are linked by at least one bond selected from the group consisting of an amide bond, an ether bond, a urethane bond, a urea bond, and an ester bond.

[0435] In formula (HC), M HC Examples of the alkali metal represented by formula (HC) include lithium, sodium, and potassium, and sodium is particularly preferred. HC Examples of the onium represented by the formula include ammonium, phosphonium, and sulfonium, and ammonium is particularly preferred. HC From the viewpoint of scratch and stain prevention, is preferably an alkali metal or an onium, and more preferably an alkali metal.

[0436] In formula (HC), the total number of mhc and nhc is preferably 3 or more, more preferably 3 to 8, and particularly preferably 4 to 6.

[0437] The molecular weight of the hydroxycarboxylic acid or salt thereof is preferably 600 or less, more preferably 500 or less, and particularly preferably 300 or less. The molecular weight of the hydroxycarboxylic acid or salt thereof is preferably 76 or more.

[0438] Examples of hydroxycarboxylic acids that constitute hydroxycarboxylic acid salts include gluconic acid, glycolic acid, lactic acid, tartronic acid, hydroxybutyric acid (e.g., 2-hydroxybutyric acid, 3-hydroxybutyric acid, and γ-hydroxybutyric acid), malic acid, tartaric acid, citramalic acid, citric acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinelaideic acid, cerebronic acid, quinic acid, shikimic acid, monohydroxybenzoic acid derivatives (e.g., salicylic acid, creosote acid (homosalic acid)), and the like. Examples of suitable hydroxybenzoic acid derivatives include cinnamic acid, ...

[0439] As the hydroxycarboxylic acid or the hydroxycarboxylic acid constituting the salt of the hydroxycarboxylic acid, from the viewpoint of scratch and stain suppression, a compound having two or more hydroxy groups is preferred, a compound having three or more hydroxy groups is more preferred, a compound having five or more hydroxy groups is even more preferred, and a compound having five to eight hydroxy groups is particularly preferred.

[0440] As a compound having one carboxy group and two or more hydroxy groups, gluconic acid or shikimic acid is preferred. As a compound having two or more carboxy groups and one hydroxy group, citric acid or malic acid is preferred. As a compound having two or more carboxy groups and two or more hydroxy groups, tartaric acid is preferred. Among the above, gluconic acid is particularly preferred as a hydroxycarboxylic acid.

[0441] The undercoat layer may contain one or more hydrophilic compounds. When the undercoat layer contains a hydrophilic compound (preferably a hydroxycarboxylic acid or a salt thereof), the content of the hydrophilic compound (preferably a hydroxycarboxylic acid or a salt thereof) is preferably 0.01% by mass to 50% by mass, more preferably 0.1% by mass to 40% by mass, and particularly preferably 1.0% by mass to 30% by mass, relative to the total mass of the undercoat layer.

[0442] -Application range of hydrophilic compounds- As will be explained below, the hydrophilic compound (preferably a hydroxycarboxylic acid or a salt thereof) can be used not only in the undercoat layer but also as a component of layers other than the undercoat layer.

[0443] From the viewpoint of scratch and stain prevention, the hydrophilic compound (preferably a hydroxycarboxylic acid or a salt thereof) is preferably contained in a layer on an aluminum support, which is one type of support. The layer on the aluminum support is preferably a layer disposed on the side on which the image recording layer is formed. Furthermore, the layer on the aluminum support is more preferably a layer in contact with the aluminum support. Preferred examples of the layer on the aluminum support (preferably a layer in contact with the aluminum support) include an undercoat layer or an image recording layer.

[0444] The hydrophilic compound (preferably a hydroxycarboxylic acid or a salt thereof) may be contained in a layer other than the layer in contact with the aluminum support (for example, the outermost layer or the image-recording layer). In an embodiment, from the viewpoint of scratch and stain resistance, the image-recording layer preferably contains a hydroxycarboxylic acid or a salt thereof.

[0445] A preferred embodiment is one in which the surface of the aluminum support facing the image recording layer is surface-treated with a composition (e.g., an aqueous solution) containing at least a hydroxycarboxylic acid or a salt thereof. In this embodiment, at least a portion of the treated hydroxycarboxylic acid or a salt thereof can be detected in a state contained in a layer (e.g., an image recording layer or an undercoat layer) on the image recording layer side that contacts the aluminum support. By containing a hydroxycarboxylic acid or a salt thereof in the layer on the image recording layer side that contacts the aluminum support, the surface of the aluminum support facing the image recording layer can be made hydrophilic. Furthermore, by containing a hydroxycarboxylic acid or a salt thereof in the layer on the image recording layer side that contacts the aluminum support, the contact angle with water on the surface of the aluminum support facing the image recording layer can be easily set to 110° or less by the airborne water drop method, thereby providing excellent scratch and stain resistance.

[0446] [Other ingredients] In addition to the compounds for the undercoat layer, the undercoat layer may contain, for example, a chelating agent, a secondary or tertiary amine, and a polymerization inhibitor to prevent staining over time.

[0447] [Formation method] The undercoat layer can be formed by a known method (for example, a coating method). The coating amount (solid content) of the undercoat layer is 0.1 mg / m 2 ~300mg / m 2 Preferably, the concentration is 5 mg / m 2 ~200mg / m 2 It is more preferable that:

[0448] <<Applications>> The on-press development type lithographic printing plate precursor according to an embodiment of the present disclosure is a lithographic printing plate precursor that can be used for on-press development. The on-press development type lithographic printing plate precursor according to an embodiment of the present disclosure can form a lithographic printing plate through, for example, an exposure step and an on-press development step described below. The obtained lithographic printing plate can be used for various printing methods.

[0449] <Method for preparing a lithographic printing plate and lithographic printing method> A method for producing a lithographic printing plate according to an embodiment of the present disclosure includes a step of imagewise exposing an on-press development type lithographic printing plate precursor according to an embodiment of the present disclosure (hereinafter also referred to as an "exposure step"), and a step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas (hereinafter also referred to as an "on-press development step"). According to an embodiment of the present disclosure, there is provided a method for producing a lithographic printing plate using an on-press development type lithographic printing plate precursor that is suppressed from discoloring due to exposure to ozone.

[0450] A lithographic printing method according to an embodiment of the present disclosure includes the steps of: imagewise exposing an on-press development type lithographic printing plate precursor according to an embodiment of the present disclosure (i.e., an exposure step); supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas to prepare a lithographic printing plate (i.e., an on-press development step); and printing with the obtained lithographic printing plate (hereinafter also referred to as a "printing step"). According to an embodiment of the present disclosure, a printing method using an on-press development type lithographic printing plate precursor that is suppressed from discoloring due to exposure to ozone is provided.

[0451] Each step will be specifically described below.

[0452] <<Exposure process>> In the exposure step, the on-press development type lithographic printing plate precursor is exposed imagewise. By exposing the on-press development type lithographic printing plate precursor imagewise, exposed areas and unexposed areas are formed. For example, when a negative image recording layer is used as the image recording layer, the exposed areas of the negative image recording layer form image areas, and the unexposed areas of the negative image recording layer form non-image areas. The on-press development type lithographic printing plate precursor used in the method for producing a lithographic printing plate and the printing method is the same as the on-press development type lithographic printing plate precursor described above in the section "On-press development type lithographic printing plate precursor."

[0453] The lithographic printing plate precursor is preferably imagewise exposed by laser exposure through a transparent original having a line image or a halftone dot image, or by laser beam scanning using digital data.

[0454] The wavelength of the light source is preferably 750 nm to 1,400 nm. As a light source with a wavelength of 750 nm to 1,400 nm, a solid-state laser or semiconductor laser that emits infrared light is suitable. With regard to the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably 20 microseconds or less, and the irradiation energy amount is 10 mJ / cm. 2 ~300mJ / cm 2 It is preferable to use a multi-beam laser device in order to shorten the exposure time. The exposure mechanism may be, for example, any of an internal drum type, an external drum type, or a flatbed type.

[0455] The exposure can be carried out by a conventional method using, for example, a platesetter. The lithographic printing plate precursor may be mounted on a printing press and then exposed on the printing press. The exposure may also be carried out before the lithographic printing plate precursor is mounted on the printing press.

[0456] <<On-press development process>> In the on-press development step, at least one selected from the group consisting of printing ink and dampening water is supplied on the printing press to remove the image recording layer in the non-image areas.

[0457] The on-press development process is carried out after the lithographic printing plate precursor is mounted on a printing press. When at least one selected from the group consisting of printing ink and fountain solution is supplied on the printing press, the image recording layer in the non-image areas (e.g., unexposed areas) is dissolved or dispersed and removed by the printing ink and / or fountain solution in the early stages of printing, exposing a hydrophilic surface. Meanwhile, the image recording layer in the remaining image areas (e.g., exposed areas) forms a printing ink-receptive area with an oleophilic surface. The on-press developed lithographic printing plate precursor is used as is for printing a large number of sheets.

[0458] In the on-press development process, the printing ink may be supplied first, or the dampening water may be supplied first. It is preferable to supply the printing ink first to prevent the dampening water from being contaminated by the components of the removed image recording layer. Known printing inks can be used as the printing ink. Examples of preferred printing inks include oil-based inks and ultraviolet-curable inks (UV inks). Known dampening water can be used as the dampening water.

[0459] <<Printing process>> In the printing process, printing is performed using the obtained lithographic printing plate. In the printing process, information may be printed on a recording medium using the obtained lithographic printing plate. The printing process preferably includes a step of supplying printing ink to the lithographic printing plate to print information on the recording medium. Examples of printing inks used in printing include the printing inks described above in the section "On-press development process." Examples of recording media include paper. Examples of information include letters, numbers, symbols, figures, and patterns. In the printing process, dampening water may be supplied as necessary. The printing process may be performed continuously without stopping the printing press.

[0460] <<Other processes>> In the method for preparing a lithographic printing plate according to an embodiment of the present disclosure or the lithographic printing method according to an embodiment of the present disclosure, the entire surface of the lithographic printing plate precursor may be heated, as necessary, before the exposure step, during the exposure step, or between the exposure step and the on-press development step. Such heating promotes the image formation reaction in the image recording layer, resulting in advantages such as improved sensitivity and printing durability, and stabilized sensitivity. Heating before the on-press development step is preferably performed under mild conditions of 150°C or less. Heating under such conditions can prevent problems such as hardening of non-image areas. Heating after the on-press development step is preferably performed under very strong conditions, for example, in the range of 100°C to 500°C. Heating within the above temperature range provides sufficient image strengthening and suppresses problems such as support degradation and thermal decomposition of image areas. [Example]

[0461] The present disclosure will be described in detail below with reference to examples. Unless otherwise specified, "parts" and "%" are by mass.

[0462] <Ingredients> The raw materials used in the examples and comparative examples are shown below. In the following explanation, redundant explanations of raw materials (for example, chemical structures and production methods) may be omitted.

[0463] <<Support (1)>> An aluminum alloy plate having a thickness of 0.3 mm and a quality of 1S was subjected to (Aa) mechanical graining treatment (brush graining method) described in paragraph 0126 of JP 2012-158022 A to (Ai) desmutting treatment in an acidic aqueous solution described in paragraph 0134. Next, the treatment conditions for (Aj) the first stage anodizing treatment described in paragraph 0135 of JP 2012-158022 A to (Am) the third stage anodizing treatment described in paragraph 0138 were appropriately adjusted to form an anodized coating, thereby obtaining a support (1). Between all the processing steps, a water washing treatment was carried out, and after the water washing treatment, the liquid was removed using nip rollers.

[0464] The details of the obtained support (1) are summarized below. L of the micropore anodized film surface * a * b * Lightness L in the color system * Value: 83 Average diameter of the oxide film surface of the large diameter micropores: 35 nm (depth 100 nm) Average diameter of the small pores at the communicating position in the micropores: 10 nm (depth 1,000 nm) Ratio of the depth of the large-diameter holes to the average diameter of the large-diameter holes: 2.9

[0465] <<Support (2)>> (a) Alkaline etching treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass onto the plate at a temperature of 70°C. The plate 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.

[0466] (b) Desmutting treatment using an acidic aqueous solution (first desmutting treatment) Next, a desmutting treatment was carried out using an acidic aqueous solution. The acidic aqueous solution used for the desmutting treatment was an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature was 30°C. The acidic aqueous solution was sprayed onto the aluminum plate, and the desmutting treatment was carried out for 3 seconds. After that, a water rinsing treatment was carried out.

[0467] (c) Electrochemical roughening treatment Next, electrochemical graining treatment was performed using an electrolytic solution with a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L, using an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The AC waveform is a sine wave with symmetrical positive and negative waveforms, the frequency is 50 Hz, the anode reaction time and cathode reaction time in one AC cycle are 1:1, and the current density is 75 A / dm at the peak current value of the AC waveform. 2 The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm 2 and electrolytic treatment is 112.5C / dm 2 The test was carried out four times, with a 4-second interval between each test. A carbon electrode was used as the counter electrode for the aluminum plate. After that, the plate was washed with water.

[0468] (d) Alkaline etching treatment After electrochemical graining, the aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions at 45°C. The amount of dissolved aluminum on the electrochemically grained surface was 0.2 g / m.2 After that, a water washing treatment was carried out.

[0469] (e) Desmutting treatment using an acidic aqueous solution Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used for the desmutting treatment had a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The liquid temperature was 30°C.

[0470] (f) First stage anodizing The first stage of anodizing treatment (also referred to as first anodizing treatment) was carried out using an anodizing treatment apparatus 610 using direct current electrolysis having the structure shown in Fig. 3. Specifically, the first anodizing treatment was carried out under the conditions in the "first anodizing treatment" column shown in Table 1 below, and an anodized film of a predetermined film thickness was formed. The anodizing treatment device 610 shown in FIG. 3 will now be described. In an anodizing treatment apparatus 610 shown in Fig. 3, an aluminum sheet 616 is transported as indicated by the arrow in Fig. 3. In a power supply tank 612 containing an electrolytic solution 618, the aluminum sheet 616 is positively charged by a power supply electrode 620. The aluminum sheet 616 is then transported upward in the power supply tank 612 by rollers 622, redirected downward by nip rollers 624, transported toward an electrolytic treatment tank 614 containing an electrolytic solution 626, and redirected horizontally by rollers 628. The aluminum sheet 616 is then negatively charged by an electrolytic electrode 630, thereby forming an anodized film on its surface, and the aluminum sheet 616 leaves the electrolytic treatment tank 614 and is transported to a subsequent process. In the anodizing treatment device 610, a direction changing means is formed by a roller 622, a nip roller 624, and a roller 628, and the aluminum sheet 616 is transported in a mountain shape and an inverted U shape by the roller 622, the nip roller 624, and the roller 628 in the area between the power supply tank 612 and the electrolytic treatment tank 614. The power supply electrode 620 and the electrolytic electrode 630 are connected to a DC power supply 634. A tank wall 632 is disposed between the power supply tank 612 and the electrolytic treatment tank 614.

[0471] (g) Pore-widening treatment The anodized aluminum plate was subjected to a pore widening treatment by immersing it in an aqueous solution of caustic soda with a temperature of 40°C, a caustic soda concentration of 5 mass%, and an aluminum ion concentration of 0.5 mass% under the conditions shown in Table 1 below.Then, the plate was washed with water by spraying.

[0472] (h) Second anodizing treatment A second stage of anodizing treatment (also referred to as second anodizing treatment) was performed using an anodizing treatment apparatus 610 using direct current electrolysis having the structure shown in Fig. 3. Specifically, the second anodizing treatment was performed under the conditions in the "second anodizing treatment" column shown in Table 1 below, and an anodized film of a predetermined film thickness was formed.

[0473] In this way, the support (2) was prepared. The L of the micropore anodized film surface of the obtained support (2) * a * b * Lightness L in the color system * Table 2 shows the average diameter and depth of the large-diameter micropores on the surface of the oxide film, the average diameter (nm) and depth of the small-diameter micropores at the connecting positions, the depths (nm) of the large-diameter and small-diameter micropores, the micropore density, and the thickness of the anodized film from the bottom of the small-diameter micropores to the surface of the aluminum plate (also referred to as the film thickness). In Table 1, the film thickness (AD) in the "first anodizing treatment" column and the film thickness (AD) in the "second anodizing treatment" column represent the film thickness obtained in each treatment. The electrolyte used is an aqueous solution containing the components shown in Table 1.

[0474] [Table 1]

[0475] [Table 2]

[0476] <<Support (3)>> A 0.28 mm thick Hydro 1052 aluminum alloy web (available from Norsk Hydro ASA, Norway) was used as the aluminum plate, and the surface was treated according to the following procedure to produce a support (3). The solution concentration for the electrochemical graining treatment and the amount of alkaline etching after the electrochemical graining treatment were changed.

[0477] -Alkaline etching treatment- An aluminum plate was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass onto the plate at a temperature of 70°C. The plate 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.

[0478] -Desmutting treatment using an acidic aqueous solution- Next, a desmutting treatment was carried out using an acidic aqueous solution. The acidic aqueous solution used for the desmutting treatment was an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature was 30°C. The acidic aqueous solution was sprayed onto the aluminum plate, and the desmutting treatment was carried out for 3 seconds. After that, a water rinsing treatment was carried out.

[0479] -Electrochemical roughening treatment- Next, electrochemical graining treatment was performed using an electrolytic solution with a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L, using an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The AC waveform is a sine wave with symmetrical positive and negative waveforms, the frequency is 50 Hz, the anode reaction time and cathode reaction time in one AC cycle are 1:1, and the current density is 75 A / dm at the peak current value of the AC waveform. 2 The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm 2 and electrolytic treatment is 112.5C / dm 2The test was carried out four times, with a 4-second interval between each test. A carbon electrode was used as the counter electrode for the aluminum plate. After that, the plate was washed with water.

[0480] -Alkaline etching treatment- After electrochemical graining, the aluminum plate was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass at 45° C., followed by rinsing with water.

[0481] -Desmutting treatment using an acidic aqueous solution- Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate for 3 seconds. The acidic aqueous solution used for the desmutting treatment was an aqueous solution with a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The liquid temperature was 35°C.

[0482] -Anodizing treatment- The aluminum plate was then anodized twice, with each anodizing bath containing approximately 100 liters of anodizing solution. The first anodizing condition was an electrolyte concentration of 175 g / liter, a temperature of 60°C, and a current density of 5.8 A / dm 2 The second anodization was performed under the conditions of an electrolyte concentration of 280 g / liter, a temperature of 23°C, and a current density of 10 A / dm 2 The first anodization process to form the outer aluminum oxide layer was carried out using phosphoric acid as the electrolyte, and the second anodization process to form the inner aluminum oxide layer was carried out using sulfuric acid as the electrolyte.

[0483] <<Support (4)>> To remove rolling oil from the surface of a 0.3 mm thick aluminum plate (material: JIS A 1050), a degreasing treatment was carried out using a 10 mass % sodium aluminate aqueous solution at 50 °C for 30 seconds, and then the plate was wiped with three bundled nylon brushes with a bristle diameter of 0.3 mm and a pumice-water suspension (specific gravity 1.1 g / cm) with a median diameter of 25 μm. 3The aluminum surface was grained using a 45°C etchant and then thoroughly washed with water. The plate was etched by immersing it in a 25% by mass aqueous solution of sodium hydroxide at 45°C for 9 seconds, rinsing it with water, and then immersing it in a 20% by mass aqueous solution of nitric acid at 60°C for 20 seconds and rinsing it with water. The amount of etching on the grained surface at this time was approximately 3 g / m 2 It was. Next, a continuous electrochemical surface roughening treatment was carried out using a 60 Hz AC voltage. The electrolyte used was a 1 mass % aqueous solution of nitric acid (containing 0.5 mass % aluminum ions), with a solution temperature of 50°C. The AC power waveform was a trapezoidal square wave AC with a duty ratio of 1:1 and a time TP from zero to peak of 0.8 msec. The electrochemical surface roughening treatment was carried out using a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode. The current density was 30 A / dm at the peak current value. 2 The auxiliary anode was diverted 5% of the current from the power supply. The quantity of electricity in nitric acid electrolysis was 175 C / dm when the aluminum plate was the anode. 2 After that, the surface was washed with water using a spray. Next, in an electrolyte solution of 0.5 mass% hydrochloric acid (containing 0.5 mass% aluminum ions) at a liquid temperature of 50°C, the aluminum plate was used as the anode with a quantity of electricity of 50 C / dm 2 Under the conditions, electrochemical surface roughening treatment was carried out in the same manner as in the nitric acid electrolysis, and then washing with water was carried out by spraying. Next, this plate was subjected to a current density of 15 A / dm using 15 mass% sulfuric acid (containing 0.5 mass% aluminum ions) as the electrolyte. 2 2.5g / m 2 After forming the DC anodized film, the plate was washed with water and dried. Thereafter, in order to ensure the hydrophilicity of the non-image area, silicate treatment was carried out using a 2.5% by mass aqueous solution of No. 3 sodium silicate at 60°C for 10 seconds, and then washed with water to obtain Support (4). The amount of Si attached was 10 mg / m 2 The center line average roughness (Ra) of the support (4) was measured using a needle with a diameter of 2 μm and was found to be 0.51 μm.

[0484] <<Undercoat layer coating solution (1)>> ·Undercoat layer compound (P-1, 11% by mass aqueous solution): 0.10502 parts Sodium gluconate: 0.07000 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts Preservative (BioHope L, manufactured by K.I. Chemical Co., Ltd.): 0.00149 parts ·Wednesday: 2.87190 copies

[0485] [ka]

[0486] <<Undercoat layer coating solution (2)>> ·Undercoat layer compound (P-1, 11% by mass aqueous solution): 0.10502 parts Hydroxyethyldiiminodiacetic acid: 0.01470 parts Sodium ethylenediaminetetraacetate: 0.06575 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.00159 parts Preservative (BioHope L, manufactured by K.I. Chemical Co., Ltd.): 0.00149 parts ·Wednesday: 2.86144 copies

[0487] <<Undercoat layer coating solution (3)>> The undercoat layer coating liquid (1) described in paragraph 0136 of JP-A No. 2012-66577 was used as the undercoat layer coating liquid (3).

[0488] <<Undercoat layer coating solution (4)>> ·Undercoat layer compound (P-1, 11% by mass aqueous solution): 0.0788 part Hydroxyethyldiiminodiacetic acid: 0.0280 parts Sodium ethylenediaminetetraacetate tetrahydrate: 0.0499 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.0016 parts Preservative (BioHope L, manufactured by K.I. Chemical Co., Ltd.): 0.0015 parts ·Wed: 2.8701 copies

[0489] <<Undercoat layer coating solution (5)>> ·Undercoat layer compound (P-1, 11% by mass aqueous solution): 0.0788 part Sodium gluconate: 0.0700 parts Surfactant (Emalex 710, manufactured by Nippon Emulsion Co., Ltd.): 0.0016 parts Preservative (BioHope L, manufactured by K.I. Chemical Co., Ltd.): 0.0015 parts ·Wednesday: 2.8780 copies

[0490] <<Image recording layer coating liquid (1)>> Infrared absorber (IR-1): 0.02000 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Polymerizable compound (M-1): 0.27500 parts Anionic surfactant (A-1): 0.00600 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.3602 parts 1-Methoxy-2-propanol: 4.4852 parts Methanol: 2.2838 parts Microgel liquid 1: 2.3256 parts

[0491] [ka]

[0492] The energy level of the HOMO of the infrared absorber (IR-1) is −5.35 eV. The energy level of the LUMO of the infrared absorber (IR-1) is −3.75 eV.

[0493] [ka]

[0494] [ka]

[0495] The HOMO energy level of the electron-accepting polymerization initiator (Int-1) is -6.70 eV. The LUMO energy level of the electron-accepting polymerization initiator (Int-1) is -3.08 eV. "Me" in the chemical formula of the electron-accepting polymerization initiator (Int-1) represents a methyl group.

[0496] [ka]

[0497] The HOMO energy level of the electron-donating polymerization initiator (TPB) is −5.90 eV.

[0498] [ka]

[0499] [ka]

[0500] [Method for synthesizing polymerizable compound (M-1)] A mixed solution of Takenate D-160N (polyisocyanate trimethylolpropane adduct, manufactured by Mitsui Chemicals, Inc., 4.7 parts), Aronix M-403 (manufactured by Toagosei Co., Ltd., in an amount such that the NCO value of Takenate D-160N and the hydroxyl value of Aronix M-403 were 1:1), t-butylbenzoquinone (0.02 parts), and methyl ethyl ketone (11.5 parts) was heated to 65°C. Neostan U-600 (bismuth-based polycondensation catalyst, manufactured by Nitto Kasei Co., Ltd., 0.11 parts) was added to the reaction solution, and the mixture was heated at 65°C for 4 hours. The reaction solution was cooled to room temperature (25°C), and methyl ethyl ketone was added to synthesize a urethane acrylate solution with a solids content of 50% by mass. Using a recycle-type GPC (instrument: LC908-C60, columns: JAIGEL-1H-40 and 2H-40 (manufactured by Japan Analytical Industry Co., Ltd.)), molecular weight fractionation of the urethane acrylate solution was carried out with an eluent of tetrahydrofuran (THF). The weight-average molecular weight was 20,000.

[0501] [Method for synthesizing microgel liquid 1] Microgel 1 was synthesized by the following procedure.

[0502] (Preparation of polyisocyanate compounds) To a suspension containing isophorone diisocyanate (17.78 parts, 80 molar equivalents) and the following polyhydric phenol compound (1) (7.35 parts, 20 molar equivalents) in ethyl acetate (25.31 parts), bismuth tris(2-ethylhexanoate) (Neostan U-600, manufactured by Nitto Kasei Co., Ltd., 0.043 parts) was added and stirred. Once the heat generation subsided, the reaction temperature was set to 50°C, and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50% by mass) of the polyhydric isocyanate compound (1).

[0503] [ka]

[0504] (Preparation of Microgels) The oil phase and aqueous phase components listed below were mixed and emulsified using a homogenizer at 12,000 rpm for 10 minutes. The resulting emulsion was stirred at 45°C for 4 hours, after which a 10% by weight aqueous solution (5.20 g) of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) was added. The mixture was stirred at room temperature for 30 minutes and then allowed to stand at 45°C for 24 hours. The solids concentration was adjusted to 20% by weight using distilled water, yielding an aqueous dispersion of microgel (1). The average particle size was measured by light scattering and found to be 0.28 μm.

[0505] -Oil phase components- (Component 1) Ethyl acetate: 12.0 parts (Component 2) 3.76 parts of an adduct obtained by adding trimethylolpropane (6 molar equivalents) and xylene diisocyanate (18 molar equivalents) to one-end methylated polyoxyethylene (1 molar equivalent, number of repeating oxyethylene units: 90) (50% by mass ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.) (Component 3) Polyisocyanate compound (1) (as a 50% by mass ethyl acetate solution): 15.0 parts (Component 4) 65% by weight ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Corporation): 11.54 parts (Component 5) 10% by weight ethyl acetate solution of sulfonate surfactant (Paionin A-41-C, manufactured by Takemoto Oil & Fat Co., Ltd.): 4.42 parts

[0506] -Aqueous phase components- Distilled water: 46.87 parts

[0507] <<Image recording layer coating liquid (2)>> Infrared absorber (IR-1): 0.00600 parts Infrared absorber (IR-2): 0.0200 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Polymerizable compound (M-1): 0.27500 parts Anionic surfactant (A-1): 0.09000 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.9200 parts 1-Methoxy-2-propanol: 3,1000 parts Methanol: 2.7900 parts Microgel liquid 2: 2.90700 parts

[0508] [ka]

[0509] The HOMO energy level of the infrared absorber (IR-2) is -5.31 eV. The LUMO energy level of the infrared absorber (IR-2) is -3.78 eV. "Bu" in the chemical formula of the infrared absorber (IR-2) represents a butyl group.

[0510] [Method for synthesizing microgel liquid 2] -Preparation of oil phase components- 6.66 g of a polyfunctional isocyanate compound (PM-200: manufactured by Wanka Chemical), 5.46 g of a 50% by mass ethyl acetate solution of "Takenate (registered trademark) D-116N (an adduct of trimethylolpropane (TMP), m-xylylene diisocyanate (XDI), and polyethylene glycol monomethyl ether (EO90) (structure shown below))" manufactured by Mitsui Chemicals, Inc., 11.24 g of a 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer), 14.47 g of ethyl acetate, and 0.45 g of Paionin (registered trademark) A-41-C manufactured by Takemoto Oil & Fat Co., Ltd. were mixed and stirred at room temperature (25°C) for 15 minutes to obtain an oil phase component.

[0511] [ka]

[0512] -Preparation of aqueous phase components- As the aqueous phase component, 47.2 g of distilled water was prepared.

[0513] -Microcapsule formation process- The aqueous phase component was added to the oil phase component and mixed, and the resulting mixture was emulsified using a homogenizer at 12,000 rpm for 16 minutes to obtain an emulsion. To the resulting emulsion was added 16.8 g of distilled water, and the resulting liquid was stirred at room temperature for 10 minutes. The stirred liquid was then heated to 45°C and stirred for 4 hours while maintaining the liquid temperature at 45°C, thereby distilling off ethyl acetate from the liquid. Next, 5.12 g of a 10% by 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. The solids concentration was adjusted to 20% by weight with distilled water, yielding an aqueous dispersion of microgel 2. The volume average particle size of microgel 2 was measured using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.) and found to be 165 nm. The obtained aqueous dispersion of polymer particles 2 was designated as microgel liquid 2.

[0514] <<Image recording layer coating liquid (3)>> Infrared absorber (IR-3): 0.026 parts Electron-accepting polymerization initiator (Int-2): 0.060 parts Electron-donating polymerization initiator (TPB): 0.050 parts ·Polymerizable compound (M-2): 0.250 part ·Polymerizable compound (M-3): 0.250 part Binder (S-LEC BX-5Z, manufactured by Sekisui Chemical Co., Ltd.): 0.150 parts 1-Methoxy-2-propanol: 4.988 parts 2-butanone: 9.262 parts

[0515] [ka]

[0516] The HOMO energy level of the infrared absorber (IR-3) is −5.43 eV. The LUMO energy level of the infrared absorber (IR-3) is −3.95 eV.

[0517] [ka]

[0518] The HOMO energy level of the electron-accepting polymerization initiator (Int-2) is −6.96 eV. The LUMO energy level of the electron-accepting polymerization initiator (Int-2) is −3.18 eV.

[0519] [ka]

[0520] [ka]

[0521] [ka]

[0522] <<Image recording layer coating liquid (4)>> Infrared absorber (IR-4): 0.027 parts Infrared absorber (IR-5): 0.015 parts Electron-accepting polymerization initiator (Int-3): 0.041 parts ·Polymerizable compound (M-4): 0.100 part ·Polymerizable compound (M-5): 0.096 part ·Polymerizable compound (M-6): 0.096 part Polymer particles 1:0.300 parts Color former (S-2): 0.041 parts Hydroxypropyl cellulose: 0.030 parts n-Propanol: 5.168 parts 2-butanone: 6,460 parts 1-Methoxy-2-propanol: 1.615 parts Methanol: 2.907 parts

[0523] [ka]

[0524] The HOMO energy level of the infrared absorber (IR-4) is -5.42 eV. The LUMO energy level of the infrared absorber (IR-4) is -3.82 eV. "Ph" in the chemical formula of the infrared absorber (IR-4) represents a phenyl group.

[0525] [ka]

[0526] The HOMO energy level of the infrared absorber (IR-5) is -5.43 eV. The LUMO energy level of the infrared absorber (IR-5) is -3.84 eV. "Ph" in the chemical formula of the infrared absorber (IR-5) represents a phenyl group.

[0527] [ka]

[0528] The HOMO energy level of the electron-accepting polymerization initiator (Int-3) is −7.34 eV. The LUMO energy level of the electron-accepting polymerization initiator (Int-3) is −3.26 eV.

[0529] [ka]

[0530] [ka]

[0531] [ka]

[0532] [ka]

[0533] In the chemical structural formula of polymer particle 1, n is 40. The weight average molecular weight of polymer particle 1 is 90,000.

[0534] [ka]

[0535] <<Image recording layer coating liquid (5)>> The photosensitive solution (1) described in paragraph 0139 of JP-A No. 2012-66577 was used as the image recording layer coating solution (5).

[0536] <<Image recording layer coating liquid (6)>> Infrared absorber (IR-1): 0.0175 parts Infrared absorber (IR-2): 0.0013 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Color-forming compound (Z-1): 0.0010 parts ·Polymerizable compound (M-7): 0.27500 parts Anionic surfactant (A-1): 0.00600 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.3602 parts 1-Methoxy-2-propanol: 4.4852 parts Methanol: 2.2838 parts Microgel liquid 1: 2.3256 parts

[0537] The color former (Z-1) has the following chemical structure.

[0538] [ka]

[0539] The polymerizable compound (M-7) is a urethane (meth)acrylate oligomer (U-15HA (number of functional groups: 15), Shin-Nakamura Chemical Co., Ltd.) shown below. "Me" in the chemical formula of the polymerizable compound (M-7) represents a methyl group.

[0540] [ka]

[0541] <<Image recording layer coating liquid (7)>> Infrared absorber (IR-1): 0.0125 parts Infrared absorber (IR-6): 0.005 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Color-forming compound (Z-1): 0.0020 parts ·Polymerizable compound (M-7): 0.27500 parts Anionic surfactant (A-1): 0.00600 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.3602 parts 1-Methoxy-2-propanol: 4.4852 parts Methanol: 2.2838 parts Microgel liquid 1: 2.3256 parts

[0542] The chemical structure of the infrared absorber (IR-6) is shown below.

[0543] [ka]

[0544] <<Image recording layer coating liquid (8)>> Infrared absorber (IR-1): 0.0175 parts Infrared absorber (IR-2): 0.0013 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Polymerizable compound (M-7): 0.27500 parts Anionic surfactant (A-1): 0.00600 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.3602 parts 1-Methoxy-2-propanol: 4.4852 parts Methanol: 2.2838 parts Microgel liquid 1: 2.3256 parts

[0545] <<Image recording layer coating liquid (9)>> Infrared absorber (IR-1): 0.0175 parts Infrared absorber (IR-7): 0.0013 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Polymerizable compound (M-2): 0.27500 parts Anionic surfactant (A-1): 0.00600 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.3602 parts 1-Methoxy-2-propanol: 4.4852 parts Methanol: 2.2838 parts Microgel liquid 1: 2.3256 parts

[0546] <<Image recording layer coating liquid (10)>> Infrared absorber (IR-1): 0.0175 parts Infrared absorber (IR-2): 0.0013 parts Color former (S-1): 0.02500 parts Electron-accepting polymerization initiator (Int-1): 0.11000 parts Electron-donating polymerization initiator (TPB): 0.02500 parts ·Color-forming compound (Z-1): 0.0020 parts ·Polymerizable compound (M-7): 0.27500 parts Tricresyl phosphate (plasticizer): 0.01250 parts Anionic surfactant (A-1): 0.00600 parts Fluorine-based surfactant (W-1): 0.00416 parts 2-butanone: 4.3602 parts 1-Methoxy-2-propanol: 4.4852 parts Methanol: 2.2838 parts Microgel liquid 1: 2.3256 parts

[0547] <<Image recording layer coating liquid (11)>> Infrared absorber (IR-1): 0.0203 parts Infrared absorber (IR-2): 0.0068 parts Color former (S-3): 0.0120 parts Color former (S-4): 0.0300 parts Electron-accepting polymerization initiator (Int-1): 0.0981 parts Electron-donating polymerization initiator (TPB): 0.0270 parts ·Polymerizable compound (M-1): 0.3536 parts Tricresyl phosphate: 0.0450 parts Anionic surfactant (A-1): 0.0162 parts Fluorine-based surfactant (W-1): 0.0042 parts 2-butanone: 5.3155 parts 1-Methoxy-2-propanol: 2.8825 parts Methanol: 2.3391 parts Microgel solution 2: 2.8779 parts

[0548] [ka]

[0549] [ka]

[0550] <<Image recording layer coating liquid (12)>> Infrared absorber (IR-1): 0.0203 parts Infrared absorber (IR-2): 0.0068 parts Color former (S-3): 0.0120 parts Color former (S-4): 0.0300 parts Electron-accepting polymerization initiator (Int-1): 0.0981 parts Electron-donating polymerization initiator (TPB): 0.0270 parts ·Polymerizable compound (M-1): 0.3536 parts Tricresyl phosphate: 0.0125 parts Anionic surfactant (A-1): 0.0162 parts Paionin A-41-C (Takemoto Oil & Fat Co., Ltd., 70% by weight methanol solution): 0.0081 parts Fluorine-based surfactant (W-1): 0.0042 parts 2-butanone: 5.3155 parts 1-Methoxy-2-propanol: 2.8825 parts Methanol: 2.3391 parts Microgel solution 2: 2.8779 parts

[0551] <<Outermost layer coating liquid>> The composition of the outermost layer coating solution is shown below. In each of the tables below, the values listed in the "hydrophilic polymer," "hydrophobic polymer," "color-changing compound," and "other" columns indicate the amount added (unit: parts by mass) excluding the solvent. In each of the tables below, the "solvent" column indicates that the amount of solvent added was adjusted to make the amount of coating solution 1 part by mass according to the amount of "hydrophilic polymer," "hydrophobic polymer," "color-changing compound," and "other" added (including the solvent in the case of raw materials provided in the form of a solution or dispersion).

[0552] [Table 3]

[0553] [Table 4]

[0554] [Table 5]

[0555] [Table 6]

[0556] The composition of the outermost layer coating solution (43) is shown below. ·Wednesday: 1.0161 copies Metrolose SM04: 0.0600 parts ·FS-102 (17% by mass aqueous dispersion): 0.1177 parts Rapisol A-80 (80% by weight aqueous solution, manufactured by NOF Corporation): 0.0063 parts

[0557] The composition of the outermost layer coating solution (44) is shown below. ·Wednesday: 0.8009 parts Metrolose SM04: 0.0400 parts ·FS-102 (17% by mass aqueous dispersion): 0.3529 parts Rapisol A-80 (80% by weight aqueous solution, manufactured by NOF Corporation): 0.0063 parts

[0558] The details of each component of the coating solution for the outermost layer described above are shown below.

[0559] [Hydrophilic polymer] Gohsenex L3266: Sulfonic acid-modified polyvinyl alcohol, manufactured by Mitsubishi Chemical Corporation, Mw=17,000 Gohsenex CKS-50: Sulfonic acid-modified polyvinyl alcohol, manufactured by Mitsubishi Chemical Corporation, Mw=27,000 Metrose SM04: Methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd., degree of methoxy substitution = 1.8

[0560] [ka]

[0561] [Hydrophobic polymer] FS-101: Acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=49℃ FS-102: Styrene-acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=103℃ FS-106: Acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=84℃ FS-107: Acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=84℃ FS-201: Styrene-acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=89℃ FS-301: Styrene-acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=55℃ FS-501: Acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=79℃ FS-701: Fluorine-based acrylic, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg=82℃ Boncoat SK-105E: Styrene, manufactured by DIC Corporation, Tg=100℃ Boncoat ED-85E: Acrylic, manufactured by DIC Corporation, Tg=30℃ Boncoat H-5: Acrylic, manufactured by DIC Corporation, Tg=33°C Boncoat R-3380-E: Acrylic, manufactured by DIC Corporation, Tg=30℃ Boncoat AN-1170: Acrylic, manufactured by DIC Corporation, Tg=60℃ NEoCryl A-633: Styrene-acrylic, manufactured by DSM Coating Resins, LLC., Tg=63℃ NEoCryl A-639: Styrene-acrylic, manufactured by DSM Coating Resins, LLC., Tg=62℃ NEoCryl A-655: Styrene-acrylic, manufactured by DSM Coating Resins, LLC., Tg=33°C NEoCryl A-662: Styrene-acrylic, manufactured by DSM Coating Resins, LLC., Tg=95℃ NEoCryl A-1092: Styrene-acrylic, manufactured by DSM Coating Resins, LLC., Tg=98℃

[0562] [Color-changing compounds] The chemical structure of the color-changing compound is shown below.

[0563] [ka]

[0564] [ka]

[0565] [ka]

[0566] [others] Emalex 710: surfactant, polyoxyethylene lauryl ether, manufactured by Nippon Emulsion Co., Ltd.

[0567] <Examples 1 to 67 and Comparative Examples 1 to 4> Lithographic printing plate precursors were prepared according to the following procedure using supports and coating solutions selected according to the descriptions in Tables 7 to 9. In Tables 7 to 9, layers marked with "-" indicate layers not included in the lithographic printing plate precursor.

[0568] << Formation of primer layer >> The undercoat layer coating solution was applied to the support in a dry amount of 100 mg / m 2 The undercoat layer was formed by coating the mixture so that the thickness became

[0569] <<Formation of image recording layer>> The image recording layer coating solution was applied onto the support or the undercoat layer with a bar, and then dried in an oven at 120°C for 40 seconds to give a dry coating weight of 1.3 g / m 2 An image recording layer of the above formula was formed.

[0570] <<Formation of the outermost layer>> The outermost layer coating solution was applied onto the image recording layer with a bar, and then dried in an oven at 120°C for 60 seconds to give a dry coating weight of 0.7 g / m 2 The outermost layer was formed.

[0571] <<Evaluation>> [Ozone discoloration] The prepared lithographic printing plate precursor was cut into a size of 3 cm square, placed in a 100 mL vial, and then placed on a table. An ozone generator (ozone concentration: approximately 150 ppm) was fixed to the top of the Kiriyama filter bottle, and the vial was then covered. A stirring blade was placed at the bottom of the Kiriyama filter bottle as a spacer, and the ozone airflow was vented during exposure. The L of the lithographic printing plate before and after 8 hours of ozone exposure was * , a * , and b *was measured using a colorimeter (Ecxact manufactured by X-Rite). Ozone discoloration was evaluated according to the following criteria. The larger the value of the following criteria, the more ozone discoloration is suppressed. The evaluation results are shown in Tables 7 to 9. 10: The color difference (ΔE) before and after exposure to ozone was less than 0.5. 9: The color difference (ΔE) after exposure to ozone was 0.5 or more and less than 1.0. 8: The color difference (ΔE) after exposure to ozone was 1.0 or more and less than 1.5. 7: The color difference (ΔE) after exposure to ozone was 1.5 or more and less than 2.0. 6: The color difference (ΔE) after exposure to ozone was 2.0 or more and less than 2.5. 5: The color difference (ΔE) after exposure to ozone was 2.5 or more and less than 3.0. 4: The color difference (ΔE) after exposure to ozone was 3.0 or more and less than 3.5. 3: The color difference (ΔE) after exposure to ozone was 3.5 or more and less than 4.0. 2: The color difference (ΔE) after exposure to ozone was 4.0 or more and less than 4.5. 1: The color difference (ΔE) after exposure to ozone was 4.5 or more.

[0572] [Development waste on the machine] The prepared lithographic printing plate precursor was exposed using a Fujifilm Corporation Luxel PLATESETTER T-6000III equipped with an infrared semiconductor laser under the following conditions: outer drum rotation speed 1000 rpm, laser output 70%, and resolution 2400 dpi. The exposed image included a solid image and a 50% halftone dot chart with a 20 μm dot FM screen. The exposed lithographic printing plate precursor was mounted on the plate cylinder of a Komori Corporation Lithrone 26 printing press without development. Using a dampening solution of Ecology-2 (Fujifilm) / tap water = 2 / 98 (volume ratio) and Space Color Fusion G black ink (DIC Graphics), the dampening solution and ink were supplied using the standard automatic print start method of the Lithrone 26, and after on-press development, 100 sheets were printed on Tokubishi Art Paper (Mitsubishi Paper Mills, ream weight: 76.5 kg) at a printing speed of 10,000 sheets per hour. This procedure was repeated for 15 plates, and the occurrence of residue on the dampening roller was evaluated sensorily. If residue was present, a grade of C was given; if slight residue was observed, a grade of B; and if no residue was present, an grade of A was given. The evaluation results are shown in Tables 7 to 9.

[0573] [Table 7]

[0574] [Table 8]

[0575] [Table 9]

[0576] The "hydrophobic polymer content" in Tables 7 to 9 indicates the content of the hydrophobic polymer calculated based on the total mass of the outermost layer. The "hydrophobic polymer content" in Tables 7 to 9 can be evaluated as the area occupied by the hydrophobic polymer on the surface of the outermost layer. The "contact angle of a water droplet" in Tables 7 to 9 indicates the contact angle of a water droplet 2 seconds after it was landed on the surface of the outermost layer by the water drop method in air. The "contact angle of oil droplet" in Tables 7 to 9 indicates the contact angle of an oil droplet 2 seconds after landing on the surface of the outermost layer by the water drop method in air. "ΔL" in Tables 7 to 9 is 110 mJ / cm 2 The graph shows the change in brightness ΔL before and after exposure when exposed to infrared light with a wavelength of 830 nm at an energy density of 1000 kJ / cm.

[0577] As shown in Tables 7 to 9, the occurrence of ozone discoloration is suppressed in Examples 1 to 67 compared to Comparative Examples 1 to 4. Furthermore, the occurrence of development residue during on-machine development is suppressed in Examples 1 to 67 compared to Comparative Examples 1 to 4.

[0578] The disclosures of Japanese Patent Application No. 2020-095070 filed on May 29, 2020, Japanese Patent Application No. 2021-012042 filed on January 28, 2021, and Japanese Patent Application No. 2021-061397 filed on March 31, 2021 are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0579] 12a, 12b: Aluminum support 18: Aluminum plate 20a, 20b: Anodic oxide film 22a, 22b: Micropore 24: Large diameter hole 26: Small diameter hole D: Depth 610: Anodizing treatment equipment 612: Power supply tank 614: Electrolytic treatment tank 616: Aluminum plate 618, 626: Electrolyte 620: Power supply electrode 622, 628: Laura 624: Nip roller 630: Electrolytic electrode 632: Tank wall 634: DC power supply

Claims

1. a support, an image recording layer, and an outermost layer in this order; a contact angle of a water droplet measured by an airborne water drop method on the surface of the outermost layer 2 seconds after the droplet hits the surface is greater than 36°; the contact angle of an oil droplet measured by an oil drop method in air on the surface of the outermost layer 2 seconds after landing is 9.5° or less; the outermost layer comprises a hydrophobic polymer and a hydrophilic polymer; The hydrophobic polymer includes at least one selected from the group consisting of an acrylic resin, a styrene resin, and a styrene-acrylic resin. On-press development type lithographic printing plate precursor.

2. The on-press development type lithographic printing plate precursor according to claim 1, wherein the hydrophobic polymer occupies 10% or more of the surface area of the outermost layer.

3. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the hydrophobic polymer is in the form of particles.

4. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 3, wherein the hydrophobic polymer has a glass transition temperature of 60°C or higher.

5. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 4, wherein the content of the hydrophobic polymer is 1.7 times or more the content of the hydrophilic polymer on a mass basis.

6. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 5, wherein the outermost layer contains a color-changing compound.

7. 110 mJ / cm ２ 7. The on-press development type lithographic printing plate precursor according to claim 6, wherein when exposed to infrared light of a wavelength of 830 nm at an energy density of 1000 .mu.m or more, a change in brightness .DELTA.L before and after exposure is 2.0 or more.

8. The on-press developable lithographic printing plate precursor according to claim 6 or 7, wherein the color-changing compound contains a compound that develops color upon exposure to infrared light.

9. The on-press development type lithographic printing plate precursor according to any one of claims 6 to 8, wherein the color-changing compound comprises a decomposable compound that decomposes due to exposure to infrared light.

10. The on-press development type lithographic printing plate precursor according to any one of claims 6 to 9, wherein the color-changing compound is a cyanine dye.

11. The on-press development type lithographic printing plate precursor according to any one of claims 6 to 10, wherein the color-changing compound is a compound represented by the following formula 1-1: 【Chemical 1】 In formula 1-1, R １ represents a group represented by any one of the following formulas 2 to 4, and R １１ ~R １８ are each independently a hydrogen atom, a halogen atom, or —R ａ , -OR ｂ , -SR ｃ , or -NR ｄ R ｅ represents R ａ ~R ｅ each independently represents a hydrocarbon group; A 1, A 2, and a plurality of R １１ ~R １８ may be linked to form a monocyclic or polycyclic ring, and A 1 and A 2 each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom; n 11 and n 12 each independently represent an integer of 0 to 5, the sum of n 11 and n 12 is 2 or more; n 13 and n 14 each independently represent 0 or 1; L represents an oxygen atom, a sulfur atom, or —NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes the charge. 【Chemistry 2】 In formulas 2 to 4, R ２０ , R ３０ , R ４１ , and R ４２ each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L.

12. The on-press development type lithographic printing plate precursor according to any one of claims 6 to 11, wherein the color-changing compound is a compound represented by the following formula 1-2: 【Chemistry 3】 In formula 1-2, R １ represents a group represented by any one of the following formulas 2 to 4, and R １９ ~R ２２ are each independently a hydrogen atom, a halogen atom, or —R ａ , -OR ｂ , -CN, -SR ｃ , or -NR ｄ R ｅ represents R ２３ , and R ２４ are each independently -R ａ represents R ａ ~R ｅ each independently represents a hydrocarbon group; R １９ and R ２０ , R ２１ and R ２２ , or R ２３ and R ２４ may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or —NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group, or an aryl group; R ｄ１ ~R ｄ４ , W １ , and W ２ each independently represents an alkyl group which may have a substituent, and Za represents a counter ion that neutralizes the charge. 【Chemistry 4】 In formulas 2 to 4, R ２０ , R ３０ , R ４１ , and R ４２ each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L.

13. The on-press development type lithographic printing plate precursor according to any one of claims 6 to 12, wherein the color-changing compound is a compound represented by any one of the following formulas 1-3 to 1-7: 【Chemistry 5】 In formulas 1-3 to 1-7, R １ represents a group represented by any one of the following formulas 2 to 4, and R １９ ~R ２２ are each independently a hydrogen atom, a halogen atom, or —R ａ , -OR ｂ , -CN-SR ｃ , or -NR ｄ R ｅ represents R ２３ , and R ２４ are each independently -R ａ represents R ２５ , and R ２６ are each independently a hydrogen atom, a halogen atom, or -R ａ represents R ａ to Re each independently represent a hydrocarbon group; R １９ and R ２０ , R ２１ and R ２２ , R ２３ and R ２４ , or R ２５ and R ２６ may be linked to form a monocycle or polycycle, and L is an oxygen atom, a sulfur atom, or —NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group, or an aryl group; Rd １ ~Rd ４ , W １ , and W ２ each independently represents an alkyl group which may have a substituent, and Za represents a counter ion that neutralizes the charge. 【Chemistry 6】 In formulas 2 to 4, R ２０ , R ３０ , R ４１ , and R ４２ each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with L.

14. The W １ , and the W ２ are each independently a substituted alkyl group, and the substituent is —(OCH ２ CH ２ 14. The on-press development type lithographic printing plate precursor according to claim 12 or 13, wherein the aryl group is a group having at least one of a sulfo group, a salt of a sulfo group, a carboxy group, or a salt of a carboxy group.

15. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 14, wherein the image recording layer contains at least one selected from the group consisting of an electron-accepting polymerization initiator and an electron-donating polymerization initiator.

16. The on-press development type lithographic printing plate precursor according to claim 15, wherein the electron-accepting polymerization initiator comprises a compound represented by the following formula (II): 【Chemistry 7】 In formula (II), X represents a halogen atom, and R ３ represents an aryl group.

17. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 14, wherein the image recording layer contains a compound in which an electron-donating polymerization initiator and an electron-accepting polymerization initiator form an ion pair.

18. The on-press development type lithographic printing plate precursor according to any one of claims 15 to 17, wherein the image recording layer contains an infrared absorber, and a value of the HOMO energy level of the infrared absorber - the HOMO energy level of the electron-donating polymerization initiator is 0.70 eV or less.

19. The on-press developable lithographic printing plate precursor according to any one of claims 15 to 18, wherein the image recording layer contains an infrared absorber, and a value of the LUMO energy level of the electron-accepting polymerization initiator - the LUMO energy level of the infrared absorber is 1.00 eV or less.

20. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 19, wherein the image recording layer contains a polymerizable compound having 7 or more polymerizable groups.

21. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 20, wherein the image recording layer contains a polymerizable compound having 10 or more polymerizable groups.

22. the support has an aluminum plate and an anodized aluminum coating disposed on the aluminum plate, the anodized film is located closer to the image recording layer than the aluminum plate; the anodic oxide coating has micropores extending in a depth direction from the surface on the image recording layer side, The on-press development type lithographic printing plate precursor according to any one of claims 1 to 21, wherein the average diameter of the micropores on the surface of the anodic oxide film is more than 10 nm and not more than 100 nm.

23. the micropores have large-diameter pores extending from the surface of the anodized coating to a depth of 10 nm to 1,000 nm, and small-diameter pores communicating with the bottoms of the large-diameter pores and extending from the communicating positions with the large-diameter pores to a depth of 20 nm to 2,000 nm, the average diameter of the large diameter pores on the surface of the anodized coating is 15 nm to 100 nm; The on-press development type lithographic printing plate precursor according to claim 22, wherein the small diameter pores at the communicating positions have an average diameter of 13 nm or less.

24. a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 23; a step of supplying at least one selected from the group consisting of printing ink and dampening water on a printing press to remove the image recording layer in non-image areas; A method for making a lithographic printing plate, comprising:

25. a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 23; a step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in the non-image areas to prepare a lithographic printing plate; a step of printing with the obtained lithographic printing plate; A lithographic printing method comprising:

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