On-press developable lithographic printing plate precursor and method for manufacturing printing plate

Abstract

The present invention provides an on-press developable lithographic printing plate precursor and a method for manufacturing a printing plate, the on-press developable lithographic printing plate precursor comprising an image recording layer on a support, the image recording layer containing a color-developing compound having a moiety that is cleaved by infrared exposure, a polymerization initiator, a polymerizable compound, and a hydrogen-donating compound. The hydrogen-donating compound is a compound different from the polymerization initiator, the polymerizable compound, the color-developing compound, and an acid-cleavable compound. The hydrogen-donating compound has at least one moiety, which is selected from the group consisting of -OH, -NH-, -SO2-NH-, -SO2-OH, -CO-NH-, and -CO-OH, in the molecule, and has a molecular weight of less than 3,000.

Description

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

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

[0002] Generally, a lithographic printing plate consists of an oleophilic image area that accepts ink during the printing process and a hydrophilic non-image area that accepts fountain solution. Lithographic printing utilizes the mutual repulsion of water and oil-based ink, with the oleophilic image area of ​​the lithographic printing plate acting as the ink-receptive area and the hydrophilic non-image area acting as the fountain solution-receptive area (ink-non-receptive area) to create a difference in ink adhesion on the surface of the lithographic printing plate, and after ink is applied only to the image area, the ink is transferred to a printing substrate such as paper to print.

[0003] Currently, in the platemaking process for producing a lithographic printing plate from a lithographic printing plate precursor, image exposure is performed by CTP (computer-to-plate) technology, i.e., image exposure is performed by scanning exposure or the like directly on the lithographic printing plate precursor using a laser or laser diode, without using a lithographic film.

[0004]

[0003] Meanwhile, with growing concern about the global environment, environmental issues related to waste liquids associated with wet processes such as development processes have come to the fore in the production of lithographic printing plate precursors, and as a result, efforts are being made to simplify or eliminate development processes. As one of the simplified development processes, a method called "on-press development" has been proposed. On-press development is a method in which, after image exposure of a lithographic printing plate precursor, the plate is directly mounted on a printing press without undergoing conventional wet development processes, and the non-image areas of the image-recording layer are removed at an early stage of the normal printing process.

[0005] Patent Document 1 describes a lithographic printing plate precursor having an image recording layer on a support, the image recording layer containing an infrared absorber that decomposes upon exposure to infrared light, a binder polymer having a structural unit formed from an aromatic vinyl compound, a polymerization initiator, and a polymerizable compound. Patent Document 2 describes a color-forming composition containing an acid generator, a tetraarylborate, an acid-sensitive dye precursor, and a compound having a specific structure (I).

[0006] Japanese Patent Publication No. 2020-69789 Japanese Patent No. 7280351

[0007] When a lithographic printing plate precursor is mounted on a printing press, the image in the exposed area is usually visually confirmed. When a conventional wet development process is performed, a lithographic printing plate from which the non-image area has been removed is mounted on the printing press, making it easy to visually confirm the image in the exposed area of ​​the lithographic printing plate. On the other hand, when on-press development is performed, a lithographic printing plate precursor from which the non-image area has not yet been removed is mounted on the printing press, making it difficult to visually confirm the image on the lithographic printing plate. In light of the above, and with a view to improving color development in the exposed area, a lithographic printing plate precursor has been developed that contains a color-forming compound in the image-recording layer that has a group that is cleaved by infrared exposure. While it is common to store exposed lithographic printing plate precursors under white light, it has been found that the visibility of the exposed area is particularly prone to deterioration after storage under white light in lithographic printing plate precursors that contain a color-forming compound in the image-recording layer that has a group that is cleaved by infrared exposure. On the other hand, when a color-forming compound having a group that is cleaved by infrared exposure is not used in order to suppress deterioration of visibility of the image area after storage under white light, there was a tendency that good visibility of the exposed area immediately after exposure was difficult to maintain.

[0008] The present invention has been made in view of the above, and an object of the present invention is to provide an on-press development type lithographic printing plate precursor that has good visibility in the exposed area immediately after exposure, that is likely to maintain good visibility immediately after exposure, and that has good visibility in the exposed area even after storage under white light, and a method for producing a printing plate using the on-press development type lithographic printing plate precursor.

[0009] The means for solving the above problems are described below.

[0010] [1] An on-press development type lithographic printing plate precursor having an image recording layer on a support, the image recording layer containing a color-forming compound having a group that is cleaved by infrared exposure, a polymerization initiator, a polymerizable compound, and a hydrogen-donating compound, wherein the hydrogen-donating compound is a compound different from the polymerization initiator, the polymerizable compound, the color-forming compound, and the acid-cleavable compound, and is selected from the group consisting of —OH, —NH—, —SO ２-NH-, -SO ２ An on-press development type lithographic printing plate precursor, which is a compound having at least one group selected from the group consisting of --OH, --CO--NH--, and --CO--OH in the molecule and having a molecular weight of less than 3,000.

[0011] [2] The on-press development type lithographic printing plate precursor according to [1], wherein the hydrogen donor compound is a compound having at least one partial structure represented by the following formula (I) in the molecule:

[0012]

[0013] In formula (I), X is —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a hydrogen donating group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. １Ａ ~R ３Ａ are each independently a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. １Ａ ~R ３Ａ At least two of these may be linked to form a ring. When X is a monovalent group, R １Ａ ~R ３Ａ When X is a divalent group, one or more hydrogen atoms contained in R １Ａ ~R ３Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0014] [3] The on-press development type lithographic printing plate precursor according to [1] or [2], wherein the hydrogen donor compound is a compound having at least one partial structure represented by the following formula (II) in the molecule:

[0015]

[0016] In formula (II), Ar represents an aromatic ring group, and X represents —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. ４Ａis a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. m represents an integer of 1 to 5. When m represents an integer of 2 or more, multiple Xs may be the same or different. n represents an integer of 0 to 5. When n represents an integer of 2 or more, multiple R ４Ａ may be the same or different. When n is 2 or more, a plurality of R ４Ａ may be linked to form a ring. When all Xs are monovalent groups, R ４Ａ When at least one X is a divalent group, R ４Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0017] [4] The on-press development type lithographic printing plate precursor according to any one of [1] to [3], wherein the hydrogen donor compound is a compound having at least one partial structure represented by the following formula (III) in the molecule:

[0018]

[0019] In formula (III), X is —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. ５Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. p represents an integer of 1 to 5. When p represents an integer of 2 or more, multiple Xs may be the same or different. q represents an integer of 0 to 5. When q represents an integer of 2 or more, multiple R ５ may be the same or different. When q is 2 or more, a plurality of R ５Ａ may be linked to form a ring. p+q is 6 or less. When all Xs are monovalent groups, R ５Ａ When at least one X is a divalent group, R ５Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0020] [5] The hydrogen donor compound is —OH, —NH—, —SO ２ -NH-, -SO ２ [6] The on-press development type lithographic printing plate precursor according to any one of [1] to [4], wherein the hydrogen donor compound is a compound having at least two groups selected from the group consisting of —OH, —CO—NH—, and —CO—OH in the molecule. ２ [7] The on-press development type lithographic printing plate precursor according to any one of [1] to [5], which has at least one group selected from the group consisting of —NH—. ２ The on-press development type lithographic printing plate precursor according to any one of items [1] to [6], which has at least two groups selected from the group consisting of —NH—.

[0021] [8] The on-press development type lithographic printing plate precursor according to any one of [1] to [7], wherein the hydrogen donor compound has at least one phenolic hydroxyl group. [9] The on-press development type lithographic printing plate precursor according to any one of [1] to [8], wherein the hydrogen donor compound has two or more phenolic hydroxyl groups.

[0022]

[10] The on-press developable lithographic printing plate precursor according to any one of items [1] to [9], wherein the color-forming compound having a group that is cleaved by infrared exposure is a cyanine dye represented by formula 1.

[0023]

[0024] In formula 1, R １ is exposed to infrared light １ represents a group that cleaves the -L bond, and R １１ ~R １８ each independently represents a hydrogen atom, a halogen atom, —Ra, —ORb, —SRc, or —NRdRe, and each independently represents a hydrocarbon group; A １ , A ２ and multiple R １１ ~R １８ may be linked to form a monocyclic or polycyclic ring, A １ and A ２ each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom; n１１ and n １２ each independently represents an integer of 0 to 5, provided that n １１ and n １２ The sum of n is 2 or more, １３ and n １４ each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0025]

[11] The on-press developable lithographic printing plate precursor according to

[10] , wherein the color-forming compound having a group that is cleaved by exposure to infrared light is a compound represented by formula 2.

[0026]

[0027] In formula 2, R １ is exposed to infrared light １ represents a group that cleaves the -L bond, and R ２ and R ３ each independently represents a hydrogen atom or an alkyl group; R ２ and R ３ may be linked to each other to form a ring, and Ar １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring; Y １ and Y ２ are each independently an oxygen atom, a sulfur atom, or —NR ０ - or a dialkylmethylene group, R ０ represents a hydrogen atom, an alkyl group, or an aryl group; R ４ and R ５ each independently represents an aliphatic hydrocarbon group, R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group, and L represents an oxygen atom, a sulfur atom, or —NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0028]

[12] The on-press development type lithographic printing plate precursor according to

[11] , wherein R in the above formula 2 represents an oxygen atom. １ The on-press development type lithographic printing plate precursor according to

[12] , wherein R is a group represented by the following formula (5):

[0029]

[0030] In formula (5), R １５ and R １６ each independently represents a hydrogen atom, an alkyl group, or an aryl group, E represents an onium group, and * represents a bonding site with the oxygen atom represented by L in formula 2.

[14] The on-press development type lithographic printing plate precursor according to any one of items [1] to

[13] , wherein the polymerizable compound contains a polymerizable compound having 11 or more functionalities.

[0031]

[15] The on-press development type lithographic printing plate precursor according to any one of [1] to

[14] , wherein the polymerization initiator contains a borate compound as an electron-donating polymerization initiator.

[16] The on-press development type lithographic printing plate precursor according to any one of [1] to

[15] , wherein the polymerization initiator contains an onium salt compound as an electron-accepting polymerization initiator.

[0032]

[17] The on-press development type lithographic printing plate precursor according to any one of items [1] to

[16] , wherein the image recording layer contains an acid color former in addition to the color-forming compound having a group that is cleaved by infrared exposure.

[18] The on-press development type lithographic printing plate precursor according to any one of items [1] to

[17] , which has a protective layer on the image recording layer.

[0033]

[19] The on-press development type lithographic printing plate precursor according to

[18] , wherein the protective layer contains an inorganic layer compound.

[20] The content of the inorganic layer compound is 5 to 80 mg / m ２ The on-press development type lithographic printing plate precursor according to

[19] ,

[0034]

[21] The on-press development type lithographic printing plate precursor according to any one of [1] to

[20] , wherein the micropores in the anodized film of the support are composed of large-diameter pores extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend from the communicating positions to a depth of 20 nm to 2,000 nm, and the large-diameter pores have an average diameter of 15 nm to 100 nm at the surface of the anodized film, and the small-diameter pores have an average diameter of 15 nm or less at the communicating positions.

[0035]

[22] The on-press development type lithographic printing plate precursor according to any one of [1] to

[20] , wherein the micropores in the anodized film of the support are composed of small-diameter pores extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm and large-diameter pores that communicate with the bottoms of the small-diameter pores and extend from the communicating positions to a depth of 20 nm to 2,000 nm, and the average diameter of the small-diameter pores at the surface of the anodized film is 35 nm or less, and the average maximum diameter of the large-diameter pores is 40 to 300 nm.

[0036]

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

[20] , wherein the support has an anodized film, the anodized film having, in order from the surface of the anodized film in the depth direction, an upper layer having a thickness of 30 to 500 nm and having micropores with an average diameter of 20 to 100 nm, an intermediate layer having a thickness of 100 to 300 nm and having micropores with an average diameter of 1 / 2 to 5 times the average diameter of the micropores in the upper layer, and a lower layer having a thickness of 300 to 2000 nm and having micropores with an average diameter of 15 nm or less.

[0037]

[24] A method for preparing a printing plate, comprising: a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of items [1] to

[23] ; and a step of supplying at least one of printing ink and fountain solution on a printing press to remove unexposed areas of the image recording layer in the on-press development type lithographic printing plate precursor.

[0038] According to the present invention, it is possible to provide an on-press development type lithographic printing plate precursor that has good visibility in the exposed area immediately after exposure, that is likely to maintain good visibility immediately after exposure, and that has good visibility in the exposed area even after storage under white light, and a method for producing a printing plate using the on-press development type lithographic printing plate precursor.

[0039] FIG. 1 is a graph showing an example of an alternating current waveform diagram used in electrochemical graining treatment. FIG. 2 is a side view showing an example of a radial cell in electrochemical graining treatment using AC. FIG. 3 is a schematic diagram showing the cross-sectional shape of the edge of a lithographic printing plate precursor. FIG. 4 is a conceptual diagram showing an example of the cutting section of a slitter device. FIG. 5 is a side view showing the concept of a brush graining step used in mechanical graining treatment in the production of an aluminum support. FIG. 6 is a schematic diagram of an anodizing treatment device used in anodizing treatment.

[0040] The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In the description of groups (atomic groups) in this specification, a notation that does not specify whether they are substituted or unsubstituted encompasses both unsubstituted and substituted groups. For example, the term "alkyl group" encompasses not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used to encompass both acrylic and methacrylic, and "(meth)acryloyl" is a term used to encompass both acryloyl and methacryloyl. The term "process" in this specification includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In the present invention, 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 specification are molecular weights determined by gel permeation chromatography (GPC) using columns of TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) in THF (tetrahydrofuran) as a solvent, detected by a differential refractometer, and converted using polystyrene as a standard. Hereinafter, the present invention will be described in detail.

[0041] [On-press development type lithographic printing plate precursor] An on-press development type lithographic printing plate precursor having an image recording layer on a support, the image recording layer containing a color-forming compound having a group that is cleaved by infrared exposure, a polymerization initiator, a polymerizable compound, and a hydrogen-donating compound, wherein the hydrogen-donating compound is a compound different from the polymerization initiator, the polymerizable compound, the color-forming compound, and the acid-cleavable compound, and the hydrogen-donating compound is a compound selected from the group consisting of —OH, —NH—, —SO ２ -NH-, -SO ２ The on-press development type lithographic printing plate precursor is a compound having at least one group selected from the group consisting of --OH, --CO--NH--, and --CO--OH in the molecule and having a molecular weight of less than 3,000.

[0042] The on-press development type lithographic printing plate precursor according to the present invention, by adopting the above-mentioned configuration, makes it possible to obtain an on-press development type lithographic printing plate precursor in which the visibility of the exposed area is good immediately after exposure, the good visibility immediately after exposure is easily maintained, and the visibility of the exposed area is good even after storage under white light. The reason for this is not clear, but is presumed to be as follows.

[0043] In consideration of the visibility of the exposed areas, it is common practice to add a color-forming compound having a group that is cleaved by infrared exposure to the image recording layer of a lithographic printing plate. By including a color-forming compound having a group that is cleaved by infrared exposure in the image recording layer, the visibility of the exposed areas immediately after exposure tends to be good, and the good visibility immediately after exposure tends to be maintained. As mentioned above, it is common practice to store exposed lithographic printing plate precursors under white light (white fluorescent light). However, it has been found that the visibility of the exposed areas is particularly likely to deteriorate after storage under white light in lithographic printing plate precursors containing a color-forming compound having a group that is cleaved by infrared exposure in the image recording layer. It is presumed that the color-forming body formed by the color-forming compound having a group that is cleaved by infrared exposure in the exposed areas is oxidatively decomposed during storage under white light, making it difficult to maintain the good visibility immediately after exposure and prone to deterioration.

[0044] The on-press development type lithographic printing plate precursor of the present invention contains a hydrogen donor compound in the image recording layer. Even when the lithographic printing plate precursor is stored under white light, the coexistence of the hydrogen donor compound and a color-forming compound having a group cleaved by infrared exposure in the image recording layer prevents oxidative decomposition of the color former formed in the exposed area by the color-forming compound having a group cleaved by infrared exposure during storage under white light. This is thought to be because the hydrogen donor compound donates hydrogen radicals to hydroperoxides to suppress the oxidative decomposition reaction of the highly active peroxy radicals generated during the oxidative decomposition reaction of the color former. This is thought to prevent a decrease in visibility of the image area after storage under white light. From the above, it is thought possible to obtain an on-press development type lithographic printing plate precursor that exhibits good visibility in the exposed area immediately after exposure, is likely to maintain the good visibility immediately after exposure, and maintains good visibility in the exposed area even after storage under white light.

[0045] (On-press development type lithographic printing plate precursor) First, the lithographic printing plate precursor of the present invention will be described.

[0046] (Support) The support is preferably an aluminum support. The aluminum plate used for such an aluminum support is made of a dimensionally stable metal containing aluminum as the main component, i.e., aluminum or an aluminum alloy. It is preferably selected from a pure aluminum plate and an alloy containing aluminum as the main component and trace amounts of other elements.

[0047] The foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is 10% by mass or less. Pure aluminum plate is preferred, but since completely pure aluminum is difficult to produce due to smelting technology, an alloy containing a small amount of foreign elements may also be used. The aluminum plate used as the aluminum support does not have a specific composition, and conventionally known aluminum plates, such as JIS A 1050, JIS A 1100, JIS A 3103, and JIS A 3005, can be used as appropriate. The thickness of the support (preferably, an aluminum plate) is preferably about 0.1 to 0.6 mm.

[0048] (Anodized Film) The support preferably has an anodized film. The anodized film refers to an anodized film (preferably an anodized aluminum film) having extremely fine pores (also referred to as micropores) formed on the surface of a support (preferably an aluminum plate) by anodizing. The micropores extend along the thickness direction (support side, depth direction) from the surface of the anodized film opposite the support. From the viewpoints of tone reproducibility, printing durability, and blanket smearing, the average diameter (average opening diameter) of the micropores on the surface of the anodized film is preferably 7 nm to 150 nm, more preferably 10 nm to 100 nm, even more preferably 10 nm to 60 nm, particularly preferably 15 nm to 60 nm, and most preferably 18 nm to 40 nm. The depth of the micropores is preferably 10 nm to 3,000 nm, more preferably 10 nm to 2,000 nm, and even more preferably 10 nm to 1,000 nm.

[0049] The shape of the micropores is usually a substantially straight tube (substantially cylindrical) in which the diameter of the micropores remains almost constant in the depth direction (thickness direction), but they may also be conical in which the diameter continuously decreases in the depth direction (thickness direction). Alternatively, they may have a shape in which the diameter discontinuously decreases in the depth direction (thickness direction). Examples of micropores with a shape in which the diameter discontinuously decreases in the depth direction (thickness direction) include micropores composed of a large-diameter pore portion extending in the depth direction from the surface of the anodized coating and a small-diameter pore portion that communicates with the bottom of the large-diameter pore portion and extends in the depth direction from the communicating position.

[0050] Specifically, micropores composed of large-diameter pores extending 10 nm to 1,000 nm in the depth direction from the surface of the anodized film and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend a further 20 to 2,000 nm in the depth direction from the communicating positions are preferred. The large-diameter pores and small-diameter pores are described in detail below.

[0051] Large-diameter pores: From the viewpoints of tone reproducibility, printing durability, and blanket smear resistance, the average diameter (average opening diameter) of the large-diameter pores on the surface of the anodized film is preferably 7 nm to 150 nm, more preferably 10 nm to 100 nm, even more preferably 15 nm to 100 nm, particularly preferably 15 nm to 60 nm, and most preferably 18 nm to 40 nm. The average diameter of the large-diameter pores is calculated by observing the surface of the anodized film using a field-emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times (N=4), randomly selecting 50 micropores (large-diameter pores) present within a range of 400 nm x 600 nm from the four obtained images, measuring their diameters, and calculating the arithmetic mean value. Note that if the shape of the large-diameter pores is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle with the same projected area as the projected area of ​​the opening.

[0052] The bottoms of the large diameter pores are preferably located at a depth of 70 nm to 1,000 nm (hereinafter also referred to as depth A) from the surface of the anodized film. In other words, the large diameter pores are preferably pores that extend 70 nm to 1,000 nm in the depth direction (thickness direction) from the surface of the anodized film. In particular, in terms of achieving a more excellent effect in the method for producing a lithographic printing plate precursor, depth A is more preferably 90 nm to 850 nm, even more preferably 90 nm to 800 nm, and particularly preferably 90 nm to 600 nm. The above depth is calculated as the arithmetic average of the depths of 25 or more large diameter pores measured in a photograph (150,000x magnification) of the cross section of the anodized film.

[0053] The shape of the large-diameter pores is not particularly limited, and examples thereof include a substantially straight tube shape (substantially cylindrical shape) and a conical shape whose diameter decreases in the depth direction (thickness direction), with a substantially straight tube shape being preferred. The shape of the bottom of the large-diameter pores is also not particularly limited, and may be curved (convex) or flat. The inner diameter of the large-diameter pores is not particularly limited, but is preferably approximately the same size as the diameter of the opening, or smaller than the diameter of the opening. The inner diameter of the large-diameter pores may differ from the diameter of the opening by approximately 1 nm to 10 nm.

[0054] -Small diameter hole- The small diameter hole is a hole that communicates with the bottom of the large diameter hole and extends further in the depth direction (thickness direction) from the communication position. One small diameter hole usually communicates with one large diameter hole, but two or more small diameter holes may communicate with the bottom of one large diameter hole. The average diameter of the small diameter holes at the communication position is preferably 15 nm or less, more preferably 13 nm or less, more preferably 11 nm or less, and particularly preferably 10 nm or less. There is no particular lower limit, but 5 nm is preferred.

[0055] The average diameter of the small pores is calculated by observing four images of the anodized film surface using an FE-SEM at a magnification of 150,000 times, randomly selecting 50 micropores (small pores) within a 400 nm × 600 nm range from the four images obtained, measuring their diameters, and calculating the arithmetic mean. If the large pores are deep, the upper part of the anodized film (the area where the large pores are located) may be cut (e.g., with argon gas), and then the anodized film surface may be observed with the FE-SEM to determine the average diameter of the small pores. If the shape of the small pores is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle with the same projected area as the projected area of ​​the opening.

[0056] The bottoms of the small diameter holes are preferably located at positions extending 20 nm to 2,000 nm in the depth direction from the positions where the small diameter holes communicate with the large diameter holes (corresponding to the depth A described above). In other words, the small diameter holes are holes that extend further in the depth direction (thickness direction) from the positions where the small diameter holes communicate with the large diameter holes, and the depth of the small diameter holes is preferably 20 nm to 2,000 nm, more preferably 100 nm to 1,500 nm, and particularly preferably 200 nm to 1,000 nm. The depth is calculated as the arithmetic average value by taking a photograph (150,000 times) of the cross section of the anodized coating and measuring the depths of 25 or more small diameter holes.

[0057] The shape of the small diameter hole is not particularly limited, and examples thereof include a substantially straight tube shape (substantially cylindrical shape) and a conical shape whose diameter decreases in the depth direction, with a substantially straight tube shape being preferred. The shape of the bottom of the small diameter hole is also not particularly limited, and may be curved (convex) or flat. The inner diameter of the small diameter hole is not particularly limited, and may be approximately the same as the diameter at the communicating position, or may be smaller or larger than the diameter. The inner diameter of the small diameter hole may typically differ from the diameter of the opening by approximately 1 nm to 10 nm.

[0058] The ratio of the average diameter of the large diameter pores on the surface of the anodized film to the average diameter at the communicating positions of the small diameter pores, i.e., (average diameter of the large diameter pores on the surface of the anodized film) / (average diameter of the small diameter pores at the communicating positions), is preferably 1.1 to 13, and more preferably 2.5 to 6.5. The ratio of the depth of the large diameter pores to the depth of the small diameter pores, i.e., (depth of the large diameter pores) / (depth of the small diameter pores), is preferably 0.005 to 50, and more preferably 0.025 to 40.

[0059] The shape of the micropores is generally a substantially straight tube (substantially cylindrical) shape in which the diameter of the micropores remains almost constant in the depth direction (thickness direction), but they may also be conical in which the diameter increases continuously in the depth direction (thickness direction). Alternatively, they may have a shape in which the diameter increases discontinuously in the depth direction (thickness direction). Examples of micropores with a shape in which the diameter increases discontinuously in the depth direction (thickness direction) include micropores composed of a small-diameter pore portion extending in the depth direction from the surface of the anodized coating and a large-diameter pore portion that communicates with the bottom of the small-diameter pore portion and extends in the depth direction from the communicating position.

[0060] Specifically, micropores composed of small-diameter pores extending 10 nm to 1,000 nm in the depth direction from the surface of the anodized film and large-diameter pores that communicate with the bottoms of the small-diameter pores and extend a further 20 to 2,000 nm in the depth direction from the communicating position are preferred.

[0061] Small Diameter Pores The average diameter (average opening diameter) of the small diameter pores on the surface of the anodized film is not particularly limited, but is preferably 35 nm or less, more preferably 25 nm or less, and particularly preferably 20 nm or less. There is no particular lower limit, but 15 nm is preferred. The average diameter of the small diameter pores is calculated by observing N=4 images of the anodized film surface using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, randomly selecting 50 micropores (small diameter pores) present within a range of 400 nm x 600 nm from the four obtained images, measuring their diameters, and calculating the arithmetic mean value. Note that if the shape of the small diameter pores is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle with the same projected area as the projected area of ​​the opening.

[0062] The bottoms of the small diameter pores are preferably located at a depth of 70 nm to 1,000 nm (hereinafter also referred to as depth A') from the surface of the anodized film. In other words, the small diameter pores are preferably pores that extend 70 nm to 1,000 nm in the depth direction (thickness direction) from the surface of the anodized film. The depth is calculated as the arithmetic average of the depths of 25 or more large diameter pores measured in a photograph (150,000x magnification) of the cross section of the anodized film.

[0063] The shape of the small diameter hole is not particularly limited, and examples thereof include a substantially straight tube shape (substantially cylindrical shape) and a cone shape whose diameter increases in the depth direction (thickness direction), with a substantially straight tube shape being preferred. The shape of the bottom of the small diameter hole is also not particularly limited, and may be curved (convex) or flat. The inner diameter of the small diameter hole is not particularly limited, but is preferably approximately the same size as the diameter of the opening, or smaller than the diameter of the opening. The inner diameter of the small diameter hole may differ from the diameter of the opening by approximately 1 nm to 10 nm.

[0064] Large-diameter pores are pores that communicate with the bottoms of the small-diameter pores and extend further in the depth direction (thickness direction) from the communication position. Typically, two or more small-diameter pores may communicate with the bottom of one large-diameter pore. The average diameter of the large-diameter pores at the communication positions is preferably 20 nm to 400 nm, more preferably 40 nm to 300 nm, even more preferably 50 nm to 200 nm, and particularly preferably 50 nm to 100 nm.

[0065] The average diameter of the large-diameter pores is calculated by observing four images of the anodized film surface using an FE-SEM at a magnification of 150,000 times, randomly selecting 50 micropores (large-diameter pores) present within a range of 400 nm x 600 nm from the four obtained images, measuring their diameters, and calculating the arithmetic mean. If the small-diameter pores are deep, the upper part of the anodized film (the area where the small-diameter pores are located) may be cut (e.g., with argon gas), and then the surface of the anodized film may be observed with the FE-SEM to determine the average diameter of the large-diameter pores. If the shape of the large-diameter pores is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle with the same projected area as the projected area of ​​the opening.

[0066] The bottoms of the large-diameter pores are preferably located at positions extending 20 nm to 2,000 nm in the depth direction from the positions where the pores communicate with the small-diameter pores (corresponding to the depth A' described above). In other words, the large-diameter pores are pores that extend further in the depth direction (thickness direction) from the positions where the pores communicate with the small-diameter pores, and the depth of the large-diameter pores is preferably 20 nm to 2,000 nm, more preferably 100 nm to 1,500 nm, and particularly preferably 200 nm to 1,000 nm. The depth is calculated as the arithmetic average of the depths of 25 or more large-diameter pores measured in a photograph (150,000 times magnification) of the cross section of the anodized coating.

[0067] The shape of the large-diameter hole is not particularly limited, and examples thereof include a substantially straight tube shape (substantially cylindrical shape) and a conical shape whose diameter decreases in the depth direction, with a substantially straight tube shape being preferred. The shape of the bottom of the large-diameter hole is also not particularly limited, and may be curved (convex) or flat. The inner diameter of the large-diameter hole is not particularly limited, and may be approximately the same as the diameter at the communicating position, or may be smaller or larger than the diameter. The inner diameter of the large-diameter hole may typically differ from the diameter of the opening by approximately 1 nm to 10 nm.

[0068] It is preferable that the support has an anodized film, and the anodized film has, in order from the surface of the anodized film in the depth direction, an upper layer having a thickness of 30 to 500 nm and having micropores with an average diameter of 20 to 100 nm, an intermediate layer having a thickness of 100 to 300 nm and having micropores with an average diameter of 1 / 2 to 5 times the average diameter of the micropores in the upper layer, and a lower layer having a thickness of 300 to 2000 nm and having micropores with an average diameter of 15 nm or less.

[0069] In an on-press development type lithographic printing plate precursor, it is useful to have high brightness on the anodized film surface of the support (the surface on which the image recording layer is formed) from the viewpoint of improving image visibility. In the printing process of a lithographic printing plate, a plate inspection is usually performed to confirm whether the intended image has been recorded before the printing plate is mounted on the printing press. Since it is necessary to confirm the image after image exposure in an on-press development type lithographic printing plate precursor, a method for producing a so-called print-out image in the image-exposed area is used. A method for quantitatively evaluating the visibility of the image area (image visibility) of an image-exposed on-press development type lithographic printing plate precursor can be a method of measuring the brightness of the image-exposed area and the brightness of the unexposed area and calculating the difference between them. Here, the brightness can be the brightness L* value in the CIE L*a*b* color system, and the measurement can be performed using a colorimeter (SpectroEye, manufactured by X-Rite Corporation). The greater the difference in brightness between the image-exposed and unexposed areas obtained by measurement, the easier the image will be to see. It has been found that a high brightness L* value in the CIE L*a*b* color system of the anodized film surface is effective in increasing the difference in brightness between the image-exposed and unexposed areas. In other words, a brightness L* value of 60 to 100 is preferred.

[0070] The support having an anodized coating may, if necessary, have a backcoat layer containing an organic polymer compound described in JP-A-5-45885 or a silicon alkoxy compound described in JP-A-6-35174 on the side opposite to the side on which the constituent layer containing a hydroxy acid compound having two or more hydroxyl groups is formed.

[0071] (Production of Aluminum Support Having Anodized Coating) As an example of a support, a method for producing an aluminum support having an anodized coating will be described. An aluminum support having an anodized coating can be produced using a known method. The method for producing an aluminum support having an anodized coating is not particularly limited. A preferred embodiment of the method for producing an aluminum support having an anodized coating includes a step of roughening an aluminum plate (roughening step), a step of anodizing the roughened aluminum plate (anodizing step), and a step of contacting the aluminum plate having the anodized coating obtained in the anodizing step with an acid aqueous solution or an alkaline aqueous solution to enlarge the diameter of micropores in the anodized coating (pore widening step).

[0072] Each step will be described in detail below.

[0073] <Surface Roughening Treatment Step> The surface roughening treatment step is a step of subjecting the surface of an aluminum plate to a surface roughening treatment, including electrochemical graining. The surface roughening treatment step is preferably performed before the anodizing treatment step described below, but may not be performed if the surface of the aluminum plate already has a desirable surface shape.

[0074] The roughening treatment may be electrochemical roughening alone, or may be a combination of electrochemical roughening with at least one of mechanical roughening and chemical roughening. When mechanical roughening and electrochemical roughening are combined, it is preferable to perform the electrochemical roughening treatment after the mechanical roughening treatment.

[0075] The electrochemical graining treatment is preferably carried out in an aqueous solution of nitric acid or hydrochloric acid.

[0076] Mechanical graining is generally performed on the surface of an aluminum plate with the aim of achieving a surface roughness Ra of 0.35 to 1.0 μm. The conditions for mechanical graining are not particularly limited, but the treatment can be performed, for example, according to the method described in Japanese Patent Publication No. 50-40047. Mechanical graining can be performed by brush graining using a pumice suspension or by a transfer method. Chemical graining is also not particularly limited, and can be performed according to known methods.

[0077] After mechanical graining, it is preferable to carry out the following chemical etching treatment. The chemical etching treatment carried out after mechanical graining is carried out to smooth the edges of the uneven shape on the surface of the aluminum plate, prevent ink from catching during printing, improve the stain resistance of the lithographic printing plate, and remove unnecessary substances such as abrasive particles remaining on the surface. Known chemical etching treatments include acid etching and alkali etching, but a method that is particularly excellent in terms of etching efficiency is chemical etching treatment using an alkali solution (hereinafter also referred to as "alkali etching treatment").

[0078] The alkaline agent used in the alkaline solution is not particularly limited, but suitable examples include caustic soda, caustic potash, sodium metasilicate, sodium carbonate, sodium aluminate, and sodium gluconate. The alkaline solution may contain aluminum ions. The concentration of the alkaline agent in the alkaline solution is preferably 0.01% by mass or more, more preferably 3% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less. Furthermore, the temperature of the alkaline solution is preferably room temperature or higher, more preferably 30°C or higher, and preferably 80°C or less, more preferably 75°C or less.

[0079] The etching amount is 0.01 g / m ２ More than 0.05 g / m ２ More preferably, 30 g / m ２ Preferably, 20 g / m or less ２The following is more preferable: The treatment time is preferably 2 seconds to 5 minutes depending on the etching amount, and more preferably 2 to 10 seconds from the viewpoint of improving productivity.

[0080] When alkaline etching is performed after mechanical graining, it is preferable to perform a chemical etching treatment (hereinafter also referred to as a "desmutting treatment") using a low-temperature acidic solution in order to remove any products produced by the alkaline etching treatment. The acid used in the acidic solution is not particularly limited, but examples include sulfuric acid, nitric acid, and hydrochloric acid. The concentration of the acidic solution is preferably 1 to 50% by mass. The temperature of the acidic solution is preferably 20 to 80°C. When the concentration and temperature of the acidic solution are within these ranges, the resistance to dot-like staining in a lithographic printing plate using an aluminum support is further improved.

[0081] Preferred embodiments of the roughening treatment step are exemplified below. -Aspect SA- An embodiment in which the treatments shown in (1) to (8) are carried out in this order. (1) Chemical etching treatment using an alkaline aqueous solution (first alkaline etching treatment) (2) Chemical etching treatment using an acidic aqueous solution (first desmutting treatment) (3) Electrochemical roughening treatment using an aqueous solution mainly containing nitric acid (first electrochemical roughening treatment) (4) Chemical etching treatment using an alkaline aqueous solution (second alkaline etching treatment) (5) Chemical etching treatment using an acidic aqueous solution (second desmutting treatment) (6) Electrochemical roughening treatment using an aqueous solution mainly containing hydrochloric acid (second electrochemical roughening treatment) (7) Chemical etching treatment using an alkaline aqueous solution (third alkaline etching treatment) (8) Chemical etching treatment using an acidic aqueous solution (third desmutting treatment)

[0082] -Aspect SB- An aspect in which the treatments shown in (11) to (15) are carried out in this order: (11) Chemical etching treatment using an alkaline aqueous solution (fourth alkaline etching treatment) (12) Chemical etching treatment using an acidic aqueous solution (fourth desmutting treatment) (13) Electrochemical graining treatment using an aqueous solution mainly containing hydrochloric acid (third electrochemical graining treatment) (14) Chemical etching treatment using an alkaline aqueous solution (fifth alkaline etching treatment) (15) Chemical etching treatment using an acidic aqueous solution (fifth desmutting treatment)

[0083] Before the treatment (1) of the above-mentioned embodiment SA or before the treatment (11) of the embodiment SB, a mechanical graining treatment may be carried out as necessary.

[0084] The amount of aluminum plate dissolved in the first alkaline etching treatment and the fourth alkaline etching treatment was 0.5 g / m ２ ~30g / m ２ is preferred, and 1.0 g / m ２ ~20g / m ２ is more preferred.

[0085] The aqueous solution containing nitric acid as the main component used in the first electrochemical graining treatment in Aspect SA may be an aqueous solution used in electrochemical graining treatments using direct or alternating current. For example, an aqueous solution obtained by adding aluminum nitrate, sodium nitrate, ammonium nitrate, or the like to a 1 g / L to 100 g / L aqueous solution of nitric acid may be used. The aqueous solution containing hydrochloric acid as the main component used in the second electrochemical graining treatment in Aspect SA and the third electrochemical graining treatment in Aspect SB may be an aqueous solution used in electrochemical graining treatments using direct or alternating current. For example, an aqueous solution obtained by adding 0 g / L to 30 g / L of sulfuric acid to a 1 g / L to 100 g / L aqueous solution of hydrochloric acid may be used. Note that this aqueous solution may further contain nitrate ions such as aluminum nitrate, sodium nitrate, or ammonium nitrate; or chloride ions such as aluminum chloride, sodium chloride, or ammonium chloride.

[0086] The AC power waveform used in the electrochemical graining treatment may be a sine wave, square wave, trapezoidal wave, or triangular wave. The frequency is preferably 0.1 Hz to 250 Hz. FIG. 1 is a graph showing an example of an alternating current waveform used in the electrochemical graining treatment. In FIG. 1, ta is the anode reaction time, tc is the cathode reaction time, tp is the time it takes for the current to reach its peak from 0, Ia is the peak current in the anode cycle, and Ic is the peak current in the cathode cycle. In the trapezoidal wave, the time it takes for the current to reach its peak from 0, tp, is preferably 1 msec to 10 msec. The conditions for one cycle of AC used in electrochemical graining treatment are preferably such that the ratio tc / ta of the anode reaction time ta to the cathode reaction time tc of the aluminum plate is 1 to 20, the ratio Qc / Qa of the quantity of electricity when the aluminum plate is an anode to the quantity of electricity when the aluminum plate is an anode is 0.3 to 20, and the anode reaction time ta is in the range of 5 msec to 1,000 msec. The current density is 10 to 200 A / dm2 at the peak value of the trapezoidal wave for both the anode cycle side Ia and the cathode cycle side Ic. ２ The ratio Ic / Ia is preferably 0.3 to 20. The total amount of electricity involved in the anodic reaction of the aluminum plate at the time when the electrochemical graining treatment is completed is 25 C / dm ２ ~1,000C / dm ２ is preferred.

[0087] The electrochemical graining treatment using AC can be performed using the apparatus shown in FIG. 2. FIG. 2 is a side view showing an example of a radial cell for AC electrochemical graining treatment. In FIG. 2, 50 denotes a main electrolytic cell, 51 denotes an AC power source, 52 denotes radial drum rollers, 53a and 53b denote main electrodes, 54 denotes an electrolyte supply port, 55 denotes an electrolyte, 56 denotes a slit, 57 denotes an electrolyte passage, 58 denotes an auxiliary anode, 60 denotes an auxiliary anode cell, and W denotes an aluminum sheet. When two or more electrolytic cells are used, the electrolysis conditions may be the same or different. The aluminum sheet W is wound around a radial drum roller 52 immersed in the main electrolytic cell 50 and electrolyzed by the main electrodes 53a and 53b connected to an AC power source 51 during transport. Electrolyte 55 is supplied from the electrolyte supply port 54 through a slit 56 to an electrolyte passage 57 between the radial drum roller 52 and the main electrodes 53a and 53b. The aluminum sheet W treated in the main electrolytic cell 50 is then electrolyzed in an auxiliary anode cell 60. In this auxiliary anode cell 60, an auxiliary anode 58 is disposed opposite the aluminum sheet W, and an electrolytic solution 55 is supplied so as to flow through the space between the auxiliary anode 58 and the aluminum sheet W.

[0088] The amount of aluminum plate dissolved in the second alkaline etching treatment is set to 1.0 g / m in order to facilitate the production of a predetermined lithographic printing plate precursor. ２ ~20g / m ２ is preferred, and 2.0 g / m ２ ~10g / m ２ is more preferred.

[0089] The amount of dissolution of the aluminum plate in the third alkaline etching treatment and the fifth alkaline etching treatment is set to 0.01 g / m from the viewpoint of facilitating the production of a predetermined lithographic printing plate precursor. ２ ~0.8g / m ２ is preferred, and 0.05 g / m ２ ~0.3g / m ２ is more preferred.

[0090] In the chemical etching treatments using acidic aqueous solutions (first to fifth desmutting treatments), an acidic aqueous solution containing phosphoric acid, nitric acid, sulfuric acid, chromic acid, hydrochloric acid, or a mixed acid containing two or more of these acids is preferably used. The acid concentration in the acidic aqueous solution is preferably 0.5% by mass to 60% by mass.

[0091] <Anodizing Treatment Step> The anodizing treatment step is a step of forming an aluminum oxide film on the surface of the aluminum plate by anodizing the aluminum plate that has been subjected to the surface roughening treatment. An anodizing treatment forms an aluminum anodized film having micropores on the surface of the aluminum plate. The anodizing treatment can be carried out according to a method conventionally known in this field by appropriately setting the production conditions in consideration of the desired shape of the micropores, etc.

[0092] In the anodizing treatment process, aqueous solutions of sulfuric acid, phosphoric acid, oxalic acid, etc. can be used primarily as the electrolyte. In some cases, aqueous or non-aqueous solutions of chromic acid, sulfamic acid, benzenesulfonic acid, etc., or combinations of two or more of these, can also be used. When a direct or alternating current is passed through the aluminum plate in the electrolyte, an anodized film can be formed on the surface of the aluminum plate. The electrolyte may contain aluminum ions. The aluminum ion content is not particularly limited, but is preferably 1 to 10 g / L.

[0093] The conditions for the anodizing treatment are appropriately set depending on the electrolyte used, but generally, the electrolyte concentration is 1 to 80 mass % (preferably 5 to 20 mass %), the solution temperature is 5 to 70°C (preferably 10 to 60°C), and the current density is 0.5 to 60 A / dm ２ (preferably 5 to 50 A / dm ２ ), a voltage of 1 to 100 V (preferably 5 to 50 V), and an electrolysis time of 1 to 100 seconds (preferably 5 to 60 seconds) are suitable.

[0094] A preferred example of anodizing treatment is the method described in British Patent No. 1,412,768, in which anodizing is carried out in sulfuric acid at a high current density.

[0095] Anodizing treatment can be performed multiple times. One or more of the conditions, such as the type, concentration, solution temperature, current density, voltage, and electrolysis time of the electrolyte used, can be changed in each anodizing treatment. When the anodizing treatment is performed twice, the first anodizing treatment is sometimes referred to as the first anodizing treatment, and the second anodizing treatment is sometimes referred to as the second anodizing treatment. By performing the first anodizing treatment and the second anodizing treatment, anodized films with different shapes can be formed, making it possible to provide a lithographic printing plate precursor with excellent printing performance. Furthermore, the pore widening treatment described below can be performed following anodizing treatment, and then anodizing treatment can be performed again. In this case, the first anodizing treatment, pore widening treatment, and second anodizing treatment are performed. By using the above-described method of performing the first anodizing treatment, pore widening treatment, and second anodizing treatment, it is possible to form micropores composed of large-diameter pores extending in the depth direction from the surface of the anodized film and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend in the depth direction from the communicating positions.

[0096] <Pore widening treatment step> The pore widening treatment step is a treatment (pore diameter enlargement treatment) for enlarging the diameter of micropores present in the anodized film formed by the anodized film treatment step described above. This pore widening treatment enlarges the diameter of the micropores, resulting in the formation of an anodized film having micropores with a larger average diameter.

[0097] The pore widening treatment can be carried out by bringing the aluminum plate obtained by the above-mentioned anodizing treatment step into contact with an acid aqueous solution or an alkaline aqueous solution. The contacting method is not particularly limited, and examples thereof include a dipping method and a spraying method. Among these, the dipping method is preferred.

[0098] When an alkaline aqueous solution is used in the pore-widening treatment step, it is preferable to use at least one alkaline aqueous solution selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide. The concentration of the alkaline aqueous solution is preferably 0.1 to 5% by mass. The pH of the alkaline aqueous solution is adjusted to 11 to 13, and the aluminum sheet is suitably brought into contact with the alkaline aqueous solution for 1 to 300 seconds (preferably 1 to 50 seconds) at 10 to 70°C (preferably 20 to 50°C). In this case, the alkaline treatment solution may contain metal salts of polyvalent weak acids such as carbonates, borates, and phosphates.

[0099] When an aqueous acid solution is used in the pore widening treatment step, it is preferable to use an aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, nitric acid, or hydrochloric acid, or a mixture thereof. The concentration of the aqueous acid solution is preferably 1 to 80% by mass, more preferably 5 to 50% by mass. The aluminum plate is suitably brought into contact with the aqueous acid solution for 1 to 300 seconds (preferably 1 to 150 seconds) under conditions where the temperature of the aqueous acid solution is 5 to 70°C (preferably 10 to 60°C). The aqueous alkaline solution or the aqueous acid solution may contain aluminum ions. The content of aluminum ions is not particularly limited, but is preferably 1 to 10 g / L.

[0100] The method for producing an aluminum support having an anodized film may include a hydrophilization treatment step after the pore-widening treatment step. The hydrophilization treatment may be performed by a known method such as those described in paragraphs 0109 to 0114 of JP-A-2005-254638.

[0101] The hydrophilization treatment is preferably carried out by immersing the substrate in an aqueous solution of an alkali metal silicate such as sodium silicate or potassium silicate, or by applying a hydrophilic vinyl polymer or a hydrophilic compound to form a hydrophilic undercoat layer.

[0102] The hydrophilization treatment with an aqueous solution of an alkali metal silicate such as sodium silicate or potassium silicate can be carried out according to the method and procedure described in US Pat. Nos. 2,714,066 and 3,181,461.

[0103] [Image Recording Layer] The image recording layer contains a color-forming compound having a group that is cleaved by exposure to infrared light, a polymerization initiator, a polymerizable compound, and a hydrogen-donating compound.

[0104] [Color-forming compound having a group cleaved by infrared exposure] The image recording layer in the lithographic printing plate precursor according to the present invention contains a color-forming compound having a group cleaved by infrared exposure (hereinafter also referred to as "color-forming compound"). The color-forming compound contained in the image recording layer is preferably an infrared absorber that absorbs infrared light, decomposes, and develops color upon infrared exposure. "Decomposition" refers to the cleavage of a group that cleaves upon infrared exposure. Herein, "color development" refers to the fact that the compound has almost no absorption in the visible light region (wavelength region of 400 nm or more and less than 750 nm) before infrared exposure, but absorbs in the visible light region upon infrared exposure. This also includes the shift of absorption in a wavelength region lower than the visible light region to a longer wavelength region. Hereinafter, a color-formed compound formed by the color-forming compound absorbing infrared light and decomposing upon infrared exposure is also referred to as a "color former of the color-forming compound." Furthermore, the color-forming compound preferably has the function of absorbing infrared light upon infrared exposure and converting the absorbed infrared light into heat. The decomposable infrared absorbent may be any one that absorbs and decomposes at least a portion of light in the infrared wavelength region (wavelength 750 nm to 1 mm), but is preferably an infrared absorbent that has a maximum absorption in the wavelength region of 750 nm to 1,400 nm.

[0105] The color-forming compound is preferably an infrared absorber that decomposes due to heat, electron transfer, or both caused by infrared exposure, and more preferably an infrared absorber that decomposes due to electron transfer caused by infrared exposure. Here, "decomposes due to electron transfer" means that electrons excited from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) of the decomposable infrared absorber by infrared exposure undergo intramolecular electron transfer to an electron-accepting group (a group having a potential close to that of the LUMO) within the molecule, resulting in decomposition.

[0106] From the viewpoints of color development and UV printing durability of the resulting lithographic printing plate, the color-forming compound is preferably a cyanine dye that decomposes upon exposure to infrared light. From the viewpoints of color development and UV printing durability of the resulting lithographic printing plate, the color-forming compound is more preferably a cyanine dye represented by the following formula 1:

[0107]

[0108] In formula 1, R １ is exposed to infrared light １ represents a group that cleaves the -L bond, and R １１ ~R １８ each independently represents a hydrogen atom, a halogen atom, —Ra, —ORb, —SRc, or —NRdRe, and each independently represents a hydrocarbon group; A １ , A ２ and multiple R １１ ~R １８ may be linked to form a monocyclic or polycyclic ring, A １ and A ２ each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom; n １１ and n １２ each independently represents an integer of 0 to 5, provided that n １１ and n １２ The sum of n is 2 or more, １３ and n １４ each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0109] The cyanine dye of formula 1 reacts with the R １ The -L bond is cleaved and L is ═O, ═S, or ═NR １０ Thus, a color-forming compound is formed. １ The radicals or ions are released to form radicals or ions, which contribute to the polymerization of the polymerizable compound contained in the image recording layer.

[0110] In Formula 1, R １１ ~R １８are each independently preferably a hydrogen atom, -Ra, -ORb, -SRc, or -NRdRe. The hydrocarbon group in Ra to Re is preferably a hydrocarbon group having 1 to 30 carbon atoms (number of carbon atoms), more preferably a hydrocarbon group having 1 to 15 carbon atoms, and even more preferably a hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group may be linear, branched, or have a ring structure.

[0111] R in Formula 1 １１ ~R １４ are each independently preferably a hydrogen atom or a hydrocarbon group, more preferably a hydrogen atom or an alkyl group, and even more preferably a hydrogen atom. １１ and R １３ is preferably an alkyl group, and more preferably both are linked to form a ring. The ring formed is preferably a 5-membered or 6-membered ring, more preferably a 5-membered ring. １ R bonded to the carbon atom to which + is bonded １２ and A ２ R bonded to the carbon atom to which １４ are respectively R １５ and R １７ It is preferred that they are linked to form a ring.

[0112] R in Formula 1 １５ is preferably a hydrocarbon group. １５ And, A １ R bonded to the carbon atom to which + is bonded １２ and R are preferably linked 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 color development, an indolium ring is more preferred. １７ is preferably a hydrocarbon group. １７ And, A ２ R bonded to the carbon atom to which １４ and R in Formula 1 are preferably linked 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 color development, an indole ring is more preferred.１５ and R １７ are preferably the same group, and when each of them forms a ring, it is preferable that they form the same ring.

[0113] R in Formula 1 １６ and R １８ Furthermore, from the viewpoint of improving the water solubility of the compound represented by Formula 1, it is preferable that R １６ and R １８ are each independently preferably an alkyl group having a (poly)oxyalkylene group or an alkyl group having an anionic structure, more preferably an alkoxyalkyl group, an alkyl group having a carboxylate group or a sulfonate group, and even more preferably an alkyl group having a terminal sulfonate group. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. The counter cation of the anionic structure is represented by R in Formula 1. １ -Cation that can be contained in L or A １ The counter cation of the sulfonate group may be R + or an alkali metal cation or an alkaline earth metal cation. １ -Cation that can be contained in L or A １ +, or may be an alkali metal cation or an alkaline earth metal cation. In addition, in order to increase the maximum absorption wavelength of the compound represented by Formula 1 and to improve color development and printing durability of a lithographic printing plate, R １６ and R １８ are each independently preferably an alkyl group or an alkyl group having an aromatic ring. As the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferred, an alkyl group having 1 to 4 carbon atoms is more preferred, and a methyl group or an ethyl group is even more preferred. As the alkyl group having an aromatic ring, an alkyl group having an aromatic ring at the terminal is preferred, and a 2-phenylethyl group, a 2-naphthalenylethyl group, or a 2-(9-anthracenyl)ethyl group is more preferred.

[0114] n in Formula 1 １１ and n １２ are preferably the same integers of 0 to 5, more preferably integers of 1 to 3, even more preferably 1 or 2, and particularly preferably 2.

[0115] A in Formula 1 １ and A ２ each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom, and a nitrogen atom is preferred. １ and A ２ are preferably the same atom.

[0116] Za in Formula 1 represents a counter ion that neutralizes the charge. When Za represents an anionic species, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroantimonate ion, a p-toluenesulfonate ion, a perchlorate ion, etc., with a hexafluorophosphate ion or a hexafluoroantimonate ion being preferred. When Za represents a cationic species, examples thereof include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, a sulfonium ion, etc., 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. R １１ ~R １８ and R １ -L may have an anionic structure or a cationic structure, and R １１ ~R １８ and R １ If all of -L are charge-neutral groups, Za is a monovalent counter anion. １１ ~R １８ and R １ When -L has two or more anionic structures, Za can also be a counter cation. When the cyanine dye represented by Formula 1 has a charge-neutral structure as a whole compound, Za does not exist.

[0117] In Formula 1, R １ By infrared exposure represented by R １ The groups that cleave the -L bond will be described in detail later.

[0118] The cyanine dye that decomposes upon exposure to infrared light is more preferably a cyanine dye represented by the following formula 2, from the viewpoints of color development and UV printing durability of the resulting lithographic printing plate.

[0119]

[0120] In formula 2, R １ is exposed to infrared light １ represents a group that cleaves the -L bond, and R ２ and R ３ each independently represents a hydrogen atom or an alkyl group; R ２ and R ３ may be linked to each other to form a ring, and Ar １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring; Y １ and Y ２ are each independently an oxygen atom, a sulfur atom, or —NR ０ - or a dialkylmethylene group, R ０ represents a hydrogen atom, an alkyl group, or an aryl group; R ４ and R ５ each independently represents an aliphatic hydrocarbon group, —CO ２ M group or -PO ３ M ２ group, M represents a hydrogen atom, a Na atom, a K atom or an onium group, R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group, and L represents an oxygen atom, a sulfur atom, or —NR １０ represents -, and R １０ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counter ion that neutralizes the charge.

[0121] R ４ , R ５ The aliphatic hydrocarbon group in formula 2 is not particularly limited, but is preferably an alkyl group. ２ ~R ９ and R ０The alkyl group in the formula (I) is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and even more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a cyclic structure. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, a s-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group. Of the alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is preferred.

[0122] 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 combinations thereof.

[0123] R ０The aryl group in the formula (I) is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms. The aryl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, and combinations thereof. Specific examples include a phenyl group, a 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 the aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, or a naphthyl group is preferred.

[0124] R ２ and R ３ are preferably linked to form a ring. ２ and R ３ When they are linked to form a ring, a 5-membered or 6-membered ring is preferred, and a 5-membered ring is particularly preferred.

[0125] Y １ and Y ２ are each independently an oxygen atom, a sulfur atom, or —NR ０ represents - or a dialkylmethylene group, -NR ０ - or a dialkylmethylene group is preferred, and a dialkylmethylene group is more preferred. ０ represents a hydrogen atom, an alkyl group or an aryl group, and is preferably an alkyl group.

[0126] R ４ or R ５ The alkyl group represented by R may be a substituted alkyl. ４ or R ５ Examples of the substituted alkyl group represented by the formula (a1) include groups represented by any one of the following formulas (a1) to (a5).

[0127]

[0128] -RＷ６ -R Ｗ７ (a5)

[0129] In formulas (a1) to (a4), R Ｗ０ represents an alkylene group having 2 to 6 carbon atoms, W represents a single bond or an oxygen atom, n Ｗ１ represents an integer of 1 to 45, 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 , R Ｗ６ each independently represents a single bond or an alkylene group having 1 to 12 carbon atoms, and M represents a hydrogen atom, a Na atom, a K atom, or an onium group. Ｗ７ represents an aryl group. The aryl group includes R ０ The preferred ranges are the same as those of the aryl group of the formula (I) and (II).

[0130] In formula (a1), R Ｗ０ Specific examples of the alkylene group represented by the formula (I) include an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, and the like, with an ethylene group, an n-propylene group, an isopropylene group, and an n-butylene group being preferred, and an n-propylene group being particularly preferred. Ｗ１ is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3. Ｗ１ Specific examples of the alkyl group represented by R 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, of which a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a tert-butyl group are preferred, a methyl group and an ethyl group are more preferred, and a methyl group is particularly preferred. Ｗ５ The alkyl group represented by R Ｗ１ The preferred embodiment is the same as the alkyl group represented by R Ｗ１ The preferred embodiments are the same as those of the alkyl group represented by the following formula:

[0131] Specific examples of the group represented by formula (a1) are shown below, but the present invention is not limited to these. In the following structural formula, Me represents a methyl group, Et represents an ethyl group, and * represents a bonding site.

[0132]

[0133] In formulas (a2) to (a5), R Ｗ２ ~R Ｗ４ , R Ｗ６ Specific examples of the alkylene group represented by the formula (a3) ​​include a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an isopentylene group, an n-hexyl group, an isohexyl group, an n-octylene group, an n-dodecylene group, etc., with an ethylene group, an n-propylene group, an isopropylene group, and an n-butylene group being preferred, and an ethylene group and an n-propylene group being particularly preferred. In formula (a3), two M's may be the same or different.

[0134] In 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.

[0135] Among the groups represented by formulae (a1) to (a5), the groups represented by formula (a1) or formula (a4) are preferred.

[0136] In Formula 2, R ４ and R ５ Each of R is preferably an unsubstituted alkyl group. ４ and R ５ are preferably the same group.

[0137] R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group, and preferably a hydrogen atom. １ and Ar ２each independently represents a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, a phosphonic acid group, and a group combining these. The substituent is preferably an alkyl group. Furthermore, from the viewpoint of lengthening the maximum absorption wavelength of the compound represented by Formula 2 and improving the color development property and the printing durability of the lithographic printing plate, Ar １ and Ar ２ are each independently preferably a group that forms a naphthalene ring or a benzene ring having an alkyl group or an alkoxy group as a substituent, more preferably a group that forms a naphthalene ring or a benzene ring having an alkoxy group as a substituent, and particularly preferably a group that forms a naphthalene ring or a benzene ring having a methoxy group as a substituent.

[0138] In Formula 2, Ar １ or Ar ２ is preferably a group that forms a group represented by the following formula (b1):

[0139]

[0140] In formula (b1), R １９ represents an alkyl group having 1 to 12 carbon atoms. n3 represents an integer of 1 to 4. * represents a bonding site.

[0141] Za represents a counter ion for neutralizing the charge. However, if the compound represented by formula 2 has a corresponding ionic substituent in its structure and charge neutralization is not necessary, Za is not necessary. When Za represents an anionic species, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroantimonate ion, a p-toluenesulfonate ion, a perchlorate ion, etc., with a hexafluorophosphate ion or a hexafluoroantimonate ion being preferred. When Za represents a cationic species, examples thereof include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, or a sulfonium ion, etc., 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. R １ ~R ９ , R ０ , Ar １ , Ar ２ , Y １ and Y ２ may have an anionic structure or a cationic structure, and R １ ~R ９ , R ０ , Ar １ , Ar ２ , Y １ and Y ２ If all of R are charge-neutral groups, Za is a monovalent counter anion. １ ~R ９ , R ０ , Ar １ , Ar ２ , Y １ and Y ２ When the compound has two or more anionic structures, Za can also be a counter cation.

[0142] In the above formula 1 and formula 2, R １ By infrared exposure represented by R １ The groups that cleave the -L bond are described below. When L is an oxygen atom in Formula 1 or Formula 2, R １From the viewpoint of color development, 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).

[0143]

[0144] In formulas (1-1) to (1-7), ● represents a bonding site with the oxygen atom represented by L in formula 1 or formula 2, and R ２０ are each independently a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, or —OR ２４ , -NR ２５ R ２６ or -SR ２７ represents R ２１ each independently represents a hydrogen atom, an alkyl group, or an aryl group; R ２２ is an aryl group, —OR ２４ , -NR ２５ R ２６ , -SR ２７ , -C(=O)R ２８ , -OC(=O)R ２８ or a halogen atom, R ２３ represents an aryl group, an alkenyl group, an alkoxy group, or an onium group; R ２４ ~R ２７ each independently represents a hydrogen atom, an alkyl group, or an aryl group; R ２８ is an alkyl group, an aryl group, -OR ２４ , -NR ２５ R ２６ or -SR ２７ represents Z １ represents a counter ion for neutralizing the charge.

[0145] R ２０ , R ２１ and R ２４ ~R ２８ In a preferred embodiment, when R is an alkyl group, ２ ~R ９ and R ０ The preferred embodiments of the alkyl group in R ２０ and R ２３ The number of carbon atoms in the alkenyl group in R is preferably 1 to 30, more preferably 1 to 15, and even more preferably 1 to 10. ２０ ~R２８ 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.

[0146] From the viewpoint of color development, R in formula (1-1) ２０ represents an alkyl group, an alkenyl group, an aryl group, -OR ２４ , -NR ２５ R ２６ or -SR ２７ is preferred, and alkyl group, -OR ２４ , -NR ２５ R ２６ or -SR ２７ More preferably, it is an alkyl group or —OR ２４ is more preferred, and -OR ２４ is particularly preferred. ２０ When R in formula (1-1) is an alkyl group, the alkyl group may be an alkyl group having an arylthio group, an alkyloxycarbonyl group, or an arylsulfonyl group at the α-position, and an alkyl group having an arylthio group or an alkyloxycarbonyl group at the α-position is preferred. ２０ Ga-OR ２４ If R ２４ is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, further preferably an isopropyl group or a tert-butyl group, and particularly preferably a t-butyl group. ２０ When is an alkenyl group, the alkenyl group may be an alkenyl group having an aryl group or a hydroxyaryl group.

[0147] From the viewpoint of color development, R in formula (1-2) ２１ is preferably a hydrogen atom. ２２ is -C(=O)OR ２４ , -OC(=O)OR ２４ or a halogen atom is preferred, and —C(═O)OR ２４ or -OC(=O)OR ２４ More preferably, R in formula (1-2) is ２２ -C(=O)OR ２４ or -OC(=O)OR２４ If R ２４ is preferably an alkyl group.

[0148] From the viewpoint of color development, R in formula (1-3) ２１ are each independently preferably a hydrogen atom or an alkyl group, and at least one R ２１ is more preferably an alkyl group. ２１ The alkyl group in R is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 3 to 10 carbon atoms. ２１ The alkyl group in R is preferably an alkyl group having a branched or cyclic structure, and more preferably an isopropyl group, a cyclopentyl group, a cyclohexyl group, or a tert-butyl group. ２１ In view of color development, the alkyl group in formula (1-3) is preferably a secondary or tertiary alkyl group. ２３ 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. ２３Examples of the onium group in the formula (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 aryl 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 group combining these groups. However, an alkyl group, an aryl group, and a group combining these groups are 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. ２３ is a pyridinium group, examples of the counter anion include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroantimonate ion, a p-toluenesulfonate ion, a perchlorate ion, and the like, and a p-toluenesulfonate ion, a hexafluorophosphate ion, or a hexafluoroantimonate ion is preferred.

[0149] From the viewpoint of color development, R in formula (1-4) ２０ is preferably an alkyl group or an aryl group, and two R ２０ Of these, it is more preferable that one of them is an alkyl group and the other is an aryl group. ２０may be linked to form a ring. ２０ is preferably an alkyl group or an aryl group, more preferably an aryl group, and even more preferably a p-methylphenyl group. ２０ are each independently preferably an alkyl group or an aryl group, more preferably a methyl group or a phenyl group. １ is a counter ion for neutralizing the charge, and the compound as a whole may be included in the above Za. １ is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroantimonate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a p-toluenesulfonate ion, a hexafluorophosphate ion, or a hexafluoroantimonate ion.

[0150] When L in Formula 1 or Formula 2 is an oxygen atom, from the viewpoint of color development, it is more preferable that R １ is a group represented by the following formula (5):

[0151]

[0152] In formula (5), R １５ and R １６ each independently represents a hydrogen atom, an alkyl group or an aryl group; E represents an onium group; * represents a bonding site with the oxygen atom represented by L in Formula 1 or Formula 2.

[0153] R １５ or R １６ The alkyl group represented by R ２ ~R ９ and R ０ The preferred embodiments are the same as the alkyl groups in R ２ ~R ９ and R ０ The preferred embodiments of the alkyl group in R １５ or R １６ The aryl group represented by R ０The same as the aryl group in R ０ The preferred embodiments of the aryl group represented by E are the same as those of the aryl group represented by R ２３ The same as the onium group in R ２３ In one preferred embodiment, R １５ represents a hydrogen atom, R １６ It preferably represents an alkyl group.

[0154] In formula (5), the onium group represented by E is preferably a pyridinium group represented by the following formula (6).

[0155]

[0156] In formula (6), R １７ represents a halogen atom, an alkyl group, an aryl group, a hydroxy group, or an alkoxy group; R １７ If there are multiple R １７ may be the same or different, or multiple R １７ may be linked to form a ring. n2 represents an integer of 0 to 4. R １８ represents an alkyl group, an aryl group, or an aralkyl group. ｂ represents a counter ion for neutralizing the charge.

[0157] R １７ or R １８ The alkyl group or aryl group represented by R ２ ~R ９ and R ０ The alkyl group or R ０ The same as the aryl group in R ２ ~R ９ and R ０ The alkyl group or R ０ The preferred embodiments of the aryl group are the same as those of the aryl group in R １７ The alkoxy group represented by R is preferably an alkoxy group having 1 to 10 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, and a tert-butoxy group. １８The aralkyl group in R is preferably an aralkyl group having 7 to 31 carbon atoms, more preferably an aralkyl group having 7 to 21 carbon atoms, and even more preferably an aralkyl group having 7 to 13 carbon atoms. Specific examples of the aralkyl group include a benzyl group. The aralkyl group may have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, and a group formed by combining these groups. R １８ preferably represents an alkyl group or an aralkyl group. n2 is preferably 0. Z ｂ The counter ion for neutralizing the charge represented by Z in formula (1-7) is １ The preferred embodiment is also the same as Z in formula (1-7). １ This is the same as the preferred embodiment of the above.

[0158] In the following, when L is an oxygen atom in Formula 1 or Formula 2, R １ Specific examples of the group represented by the formula: － represents a tosylate anion, and ● represents a bonding site with the oxygen atom represented by L in Formula 1 or Formula 2. Me represents methyl.

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169] When L is an oxygen atom, R １When R is an aryl group or a linear alkyl group, R １ No cleavage of the —O bond occurs.

[0170] In Formula 1 or Formula 2, when L is a sulfur atom, R １ is preferably a group represented by the following formula (2-1).

[0171]

[0172] In formula (2-1), ● represents a bonding site with the sulfur atom represented by L in formula 1 or formula 2, and R ２１ each independently represents a hydrogen atom, an alkyl group, or an aryl group; R ２２ represents an aryl group, an alkenyl group, an alkoxy group, or an onium group.

[0173] In Formula 1 or Formula 2, L is -NR １０ -, R bonded to N １ is preferably a group represented by the following formula (3-1).

[0174]

[0175] In formula (3-1), ● represents a bonding site with the nitrogen atom contained in L in formula 1 or formula 2, and X １ and X ２ each independently represents an oxygen atom or a sulfur atom, and Y represents a group represented by the above formula (2-1).

[0176] In the above formula (2-1), R ２１ and R ２２ For the alkyl group, aryl group, alkenyl group, alkoxy group, and onium group represented by the formulas (1-1) to (1-7), the descriptions regarding the alkyl group, aryl group, alkenyl group, alkoxy group, and onium group can be cited.

[0177] In Formula 1 or Formula 2, L is a sulfur atom or —NR １０ represents -, and R １０ It is preferable that represents a hydrogen atom, an alkyl group or an aryl group from the viewpoint of improving printing durability.

[0178] Specific examples of the compounds represented by Formula 1 or Formula 2 are shown below, but the present invention is not limited to these. In the following structural formulas, Ph represents phenyl.

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194] Furthermore, as the color-forming compound, those described in JP-A-2008-544322 or WO 2016 / 027886 can be suitably used.

[0195] The compound represented by Formula 1 or Formula 2 can be synthesized by applying a known method. The compound represented by Formula 1 or Formula 2 can be synthesized, for example, by the method described in

[0109] to

[0113] of JP-A-2020-69789.

[0196] The content of the color-forming compound in the image recording layer is preferably 0.1% by mass to 95% by mass, more preferably 0.5% by mass to 40% by mass, and even more preferably 1% by mass to 20% by mass, based on the total solid content of the image recording layer.

[0197] The color-forming compound itself has excellent infrared absorbing properties and therefore functions well as an infrared absorber. Therefore, when a color-forming compound is used in the image recording layer of a lithographic printing plate precursor, it is not actually necessary to use any other infrared absorber other than the color-forming compound, but the image recording layer may contain other infrared absorbers.

[0198] [Polymerization initiator] The polymerization initiator is a compound that generates polymerization initiating species such as radicals or cations by the energy of light, heat, or both, and can be appropriately selected from known thermal polymerization initiators, compounds having bonds with low bond dissociation energy, photopolymerization initiators, etc. As the polymerization initiator, an infrared-sensitive polymerization initiator is preferred. Furthermore, as the polymerization initiator, a radical polymerization initiator is preferred. Two or more types of radical polymerization initiators may be used in combination.

[0199] The radical polymerization initiator may be either an electron-accepting polymerization initiator or an electron-donating polymerization initiator.

[0200] <Electron-Accepting Polymerization Initiator> Examples of the electron-accepting polymerization initiator include organic halides, carbonyl compounds, azo compounds, organic peroxides, metallocene compounds, azide compounds, hexaarylbiimidazole compounds, disulfone compounds, oxime ester compounds, and onium salt compounds.

[0201] Preferred examples of organic halides include the compounds described in paragraphs 0022 and 0023 of JP-A No. 2008-195018. Preferred examples of carbonyl compounds include the compounds described in paragraph 0024 of JP-A No. 2008-195018. Preferred examples of azo compounds include the azo compounds described in JP-A No. 8-108621. Preferred examples of organic peroxides include the compounds described in paragraph 0025 of JP-A No. 2008-195018. Preferred examples of metallocene compounds include the compounds described in paragraph 0026 of JP-A No. 2008-195018. Preferred examples of azide compounds include compounds such as 2,6-bis(4-azidobenzylidene)-4-methylcyclohexanone. Preferred examples of the hexaarylbiimidazole compound include the compounds described in JP-A-2008-195018, paragraph 0027. Preferred examples of the disulfone compound include the compounds described in JP-A-61-166544 and JP-A-2002-328465. Preferred examples of the oxime ester compound include the compounds described in JP-A-2008-195018, paragraphs 0028 to 0030.

[0202] Among the electron-accepting polymerization initiators, onium salt compounds such as iodonium salts, sulfonium salts, and azinium salts are more preferred. Iodonium salts and sulfonium salts are particularly preferred. Specific examples of iodonium salts and sulfonium salts are shown below, but the present invention is not limited thereto.

[0203] Preferred examples of iodonium salts include diphenyliodonium salts, particularly diphenyliodonium salts having an electron-donating group as a substituent, for example, diphenyliodonium salts substituted with an alkyl group or an alkoxyl group, and asymmetric diphenyliodonium salts are also preferred. Specific examples include diphenyliodonium hexafluorophosphate, 4-methoxyphenyl-4-(2-methylpropyl)phenyliodonium hexafluorophosphate, 4-(2-methylpropyl)phenyl-p-tolyliodonium hexafluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium tetrafluoroborate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, and bis(4-t-butylphenyl)iodonium hexafluorophosphate.

[0204] Preferred examples of sulfonium salts include triarylsulfonium salts, particularly triarylsulfonium salts having electron-withdrawing groups as substituents, for example, triarylsulfonium salts in which at least a portion of the groups on the aromatic ring are substituted with halogen atoms, and more preferred are triarylsulfonium salts in which the total number of halogen atoms substituted on the aromatic ring is four or more. Specific examples include triphenylsulfonium hexafluorophosphate, triphenylsulfonium benzoylformate, bis(4-chlorophenyl)phenylsulfonium benzoylformate, bis(4-chlorophenyl)-4-methylphenylsulfonium tetrafluoroborate, tris(4-chlorophenyl)sulfonium 3,5-bis(methoxycarbonyl)benzenesulfonate, tris(4-chlorophenyl)sulfonium hexafluorophosphate, and tris(2,4-dichlorophenyl)sulfonium hexafluorophosphate. The polymerization initiator preferably contains an onium salt compound as an electron-accepting polymerization initiator.

[0205] The electron-accepting polymerization initiator may be used alone or in combination of two or more. The content of the electron-accepting polymerization initiator is preferably from 0.1 to 30% by mass, more preferably from 0.1 to 20% by mass, and even more preferably from 0.5 to 15% by mass, of the total solid content of the image recording layer, from the viewpoints of color development upon exposure, color fading upon exposure to white light, printing durability, and coating solution stability.

[0206] <Electron-Donating Polymerization Initiator> Electron-donating polymerization initiators contribute to improving the printing durability of lithographic printing plates prepared from lithographic printing plate precursors. Examples of electron-donating polymerization initiators include the following five types: (i) Alkyl or aryl ate complexes: It is believed that the carbon-hetero bond is cleaved by oxidative reaction to generate an active radical. Specific examples include borate compounds. (ii) Aminoacetic acid compounds: It is believed that the C-X bond on the carbon adjacent to the nitrogen is cleaved by oxidation to generate an active radical. X is preferably a hydrogen atom, a carboxy group, a trimethylsilyl group, or a benzyl group. Specific examples include N-phenylglycines (which may have a substituent on the phenyl group) and N-phenyliminodiacetic acid (which may have a substituent on the phenyl group). (iii) Sulfur-containing compounds: Compounds in which the nitrogen atom of the above-mentioned aminoacetic acid compounds is replaced with a sulfur atom can generate active radicals by a similar mechanism. Specific examples include phenylthioacetic acid (which may have a substituent on the phenyl group). (iv) Tin-containing compounds: Compounds in which the nitrogen atom of the aminoacetic acid compound is replaced with a tin atom can generate active radicals by the same action. (v) Sulfinates: Can generate active radicals by oxidation. Specific examples include sodium arylsulfinates.

[0207] Among electron-donating polymerization initiators, borate compounds are preferred. As the borate compound, tetraarylborate compounds or monoalkyltriarylborate compounds are preferred, and from the viewpoint of compound stability, tetraarylborate compounds are more preferred. As the counter cation of the borate compound, alkali metal ions or tetraalkylammonium ions are preferred, and sodium ions, potassium ions, or tetrabutylammonium ions are more preferred. The polymerization initiator preferably contains a borate compound as the electron-donating polymerization initiator.

[0208] Specific examples of the borate compound include the compounds shown below. ｃ ＋ represents a monovalent cation, preferably an alkali metal ion or a tetraalkylammonium ion, more preferably an alkali metal ion or a tetrabutylammonium ion, and Bu represents an n-butyl group.

[0209]

[0210]

[0211]

[0212]

[0213] The electron-donating polymerization initiator may be used alone or in combination of two or more. The content of the electron-donating polymerization initiator is preferably from 0.1 to 20% by mass, more preferably from 0.3 to 15% by mass, and even more preferably from 0.5 to 10% by mass, of the total solid content of the image recording layer, from the viewpoints of color development upon exposure, printing durability, and coating solution stability.

[0214] [Polymerizable Compound] The polymerizable compound may be, for example, a radical polymerizable compound or a cation polymerizable compound, but is preferably an addition polymerizable compound (ethylenically unsaturated compound) having at least one ethylenically unsaturated bond.As the ethylenically unsaturated compound, a compound having at least one terminal ethylenically unsaturated bond is preferred, and a compound having two or more terminal ethylenically unsaturated bonds is more preferred.The polymerizable compound can have a chemical form such as a monomer, a prepolymer, i.e., a dimer, a trimer or an oligomer, or a mixture thereof.

[0215] From the viewpoint of printing durability, the polymerizable compound is preferably pentafunctional or more, more preferably heptafunctional or more, and even more preferably eleven or more functional. "Functional" refers to a group (functional group) that contributes to polymerization, and an ethylenically unsaturated bond is preferred. For example, "tetrafunctional or more" indicates that the number of groups that contribute to polymerization is four or more. The polymerizable compound is not particularly limited, but typically has 20 or less functionalities. From the viewpoint of printing durability, the polymerizable compound is preferably a pentafunctional or more ethylenically unsaturated compound, more preferably a heptafunctional or more ethylenically unsaturated compound, and even more preferably an eleven or more functional ethylenically unsaturated compound.

[0216] The molecular weight of the polymerizable compound (weight average molecular weight when the polymerizable compound has a molecular weight distribution) is not particularly limited, but from the viewpoint of on-press developability, a smaller molecular weight is preferable, and from the viewpoint of printing durability, a larger molecular weight is preferable. The molecular weight is preferably less than 15,000. Furthermore, the molecular weight is preferably 100 or more. From the viewpoint of achieving both on-press developability and printing durability, the molecular weight is preferably 100 or more and less than 15,000, more preferably 500 or more and less than 13,000, and even more preferably 1,000 or more and less than 10,000. In a preferred embodiment, the image recording layer preferably contains, as the polymerizable compound, a polymerizable compound having 7 or more functionalities and a molecular weight of less than 15,000. In a preferred embodiment, the image recording layer preferably contains, as the polymerizable compound, a polymerizable compound having 11 or more functionalities and a molecular weight of less than 15,000.

[0217] Examples of the monomer include unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid), as well as their esters and amides. Esters of unsaturated carboxylic acids and polyhydric alcohol compounds, and amides of unsaturated carboxylic acids and polyamine compounds are preferably used. Also suitable are addition reaction products of unsaturated carboxylic acid esters or amides having a nucleophilic substituent such as a hydroxy group, an amino group, or a mercapto group with monofunctional or polyfunctional isocyanates or epoxies, and dehydration condensation reaction products of monofunctional or polyfunctional carboxylic acids. Also suitable are addition reaction products of unsaturated carboxylic acid esters or amides having an electrophilic substituent such as an isocyanate group or an epoxy group with monofunctional or polyfunctional alcohols, amines, or thiols, and substitution reaction products of unsaturated carboxylic acid esters or amides having a leaving substituent such as a halogen atom or a tosyloxy group with monofunctional or polyfunctional alcohols, amines, or thiols. As another example, compounds in which the above unsaturated carboxylic acids are replaced with unsaturated phosphonic acids, styrene, vinyl ethers, etc. can also be used. These compounds are described in JP-T-2006-508380, JP-A-2002-287344, JP-A-2008-256850, JP-A-2001-342222, JP-A-9-179296, JP-A-9-179297, JP-A-9-179298, JP-A-2004-294935, JP-A-2006-243493, JP-A-2002-275129, JP-A-2003-64130, JP-A-2003-280187, JP-A-10-333321, and the like.

[0218] Specific examples of the ester monomer of a polyhydric alcohol compound and an unsaturated carboxylic acid include, as acrylic acid esters, ethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate, ethylene oxide isocyanurate (EO)-modified triacrylate, polyester acrylate oligomer, etc. Specific examples of the methacrylic acid esters include tetramethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, pentaerythritol trimethacrylate, bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane, bis[p-(methacryloxyethoxy)phenyl]dimethylmethane, etc. Specific examples of amide monomers of polyamine compounds and unsaturated carboxylic acids include methylenebisacrylamide, methylenebismethacrylamide, 1,6-hexamethylenebisacrylamide, 1,6-hexamethylenebismethacrylamide, diethylenetriaminetrisacrylamide, xylylenebisacrylamide, and xylylenebismethacrylamide.

[0219] Also suitable are urethane-based addition-polymerizable compounds produced by an addition reaction between an isocyanate and a hydroxy group, and specific examples thereof include vinyl urethane compounds containing two or more polymerizable vinyl groups in one molecule, which are obtained by adding a vinyl monomer containing a hydroxy group represented by the following formula (M) to a polyisocyanate compound having two or more isocyanate groups in one molecule, as described in JP-B-48-41708: CH ２ = C(R Ｍ４ ) COOCH ２ CH (R Ｍ５ )OH (M) In formula (M), R Ｍ４ and R Ｍ５each independently represents a hydrogen atom or a methyl group.

[0220] Further, urethane acrylates described in JP-A-51-37193, JP-B-2-32293, JP-B-2-16765, JP-A-2003-344997, JP-A-2006-65210, JP-B-58-49860, JP-B-56-17654, JP-B-62-39417, JP-B-62-39418 Also suitable are urethane compounds having an ethylene oxide skeleton described in JP-A Nos. 2000-250211 and 2007-94138, and urethane compounds having a hydrophilic group described in U.S. Pat. No. 7,153,632, JP-A Nos. 8-505958, 2007-293221 and 2007-293223.

[0221] Details of the method of use, such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount added, can be set as desired, taking into consideration the final use of the lithographic printing plate precursor, etc. The content of the polymerizable compound is preferably from 1 to 90% by mass, more preferably from 5 to 70% by mass, and even more preferably from 10 to 50% by mass, of the total solid content of the image recording layer.

[0222] [Hydrogen-donating compound] The hydrogen-donating compound is a compound different from the polymerization initiator, the polymerizable compound, the color-forming compound, and the acid-cleavable compound, and is a compound having a structure such as —OH, —NH—, —SO ２ -NH-, -SO ２ It is a compound having at least one group selected from the group consisting of --OH, --CO--NH--, and --CO--OH in the molecule and having a molecular weight of less than 3,000.

[0223] -OH, -NH-, -SO ２ -NH-, -SO ２ A group selected from the group consisting of -OH, -CO-NH-, and -CO-OH (hereinafter also simply referred to as a "hydrogen donating group") is a group that can donate a hydrogen atom. "-OH" represents a hydroxyl group, which is different from "-CO-OH" (a carboxyl group), and -SO ２ - is a non-bonding group. "-NH-" is -SO ２ - and -CO- are groups that do not bond.

[0224] The term "compounds other than polymerization initiators, polymerizable compounds, color-forming compounds, and acid-cleavable compounds" means that even if a compound has the above-mentioned hydrogen-donating group and has a molecular weight of less than 3,000, it is not included in the hydrogen-donating compound as long as it functions as a polymerization initiator, a polymerizable compound, a color-forming compound, or an acid-cleavable compound. The polymerization initiator, polymerizable compound, and color-forming compound are as described above.

[0225] The acid-cleavable compound refers to a compound that is cleaved by the action of an acid, specifically, a ring in the molecule is cleaved (opened) by the action of an acid. So-called acid color formers that develop color upon cleavage by the action of an acid are included in the acid-cleavable compound. The hydrogen-donor compound is a compound that is different from an acid color former.

[0226] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the following formula (I) in the molecule:

[0227]

[0228] In formula (I), X is —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. １Ａ ~R ３Ａ are each independently a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. １Ａ ~R ３Ａ At least two of these may be linked to form a ring. When X is a monovalent group, R １Ａ ~R ３Ａ When X is a divalent group, one or more hydrogen atoms contained in R １Ａ ~R ３Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0229] The hydrogen donating group for X is preferably —OH, —NH—, or —SO 3 from the viewpoints of preventing fading when exposed to white light and of compatibility with the image recording layer. ２-NH- or -CO-NH- is preferred, and -OH or -SO ２ —NH— is more preferred.

[0230] R １Ａ ~R ３Ａ The group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom (hereinafter also referred to as "substituent A") is not particularly limited, but is preferably a group having 0 to 30 carbon atoms. The halogen atom is not particularly limited, but examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The heteroatom is not particularly limited, but examples thereof include a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. The substituent A is not particularly limited, but is preferably, for example, a hydrogen atom or a hydrocarbon group. The hydrocarbon group may have a heteroatom or a halogen atom.

[0231] R １Ａ ~R ３Ａ At least two of the above may be linked to form a ring. The ring formed may be a monocyclic ring or a polycyclic ring. Examples of the ring formed include an aromatic ring and an aliphatic hydrocarbon ring, and the number of ring atoms of the ring formed is preferably 6 to 14. When X is a monovalent group (specifically, -OH, -SO ２ -OH and -CO-OH) is R １Ａ ~R ３Ａ When X is a divalent group (specifically, -NH-, -SO ２ -NH- and -CO-NH-) can constitute a partial structure in formula (I), but R １Ａ ~R ３Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0232] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the above formula (I) in the molecule, and may be a compound having at least two or more partial structures represented by the above formula (I) in the molecule. The number of partial structures represented by the above formula (I) in the molecule is not particularly limited, but is preferably 1 to 10, and more preferably 1 to 5.

[0233] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the following formula (II) in the molecule:

[0234]

[0235] In formula (II), Ar represents an aromatic ring group, and X represents —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. ４Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. m represents an integer of 1 to 5. When m represents an integer of 2 or more, multiple Xs may be the same or different. n represents an integer of 0 to 5. When n represents an integer of 2 or more, multiple R ４Ａ may be the same or different. When n is 2 or more, a plurality of R ４Ａ may be linked to form a ring. When all Xs are monovalent groups, R ４Ａ When at least one X is a divalent group, R ４Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0236] X has the same meaning as X in formula (I), and the preferred range is also the same. Examples of the aromatic ring in the aromatic ring group of Ar include an aromatic hydrocarbon ring and an aromatic heterocycle. The aromatic hydrocarbon ring may be a monocyclic ring or a polycyclic ring. The number of ring atoms is preferably 6 to 15, and more preferably 6 to 10. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring. Among these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred.

[0237] The aromatic heterocycle may be a monocycle or a polycycle. The number of ring atoms is preferably 5 to 15. Examples of the heterocycle having aromaticity include a furan ring, a thiophene ring, a benzofuran ring, a benzothiophene ring, a dibenzofuran ring, a dibenzothiophene ring, a pyridine ring, an indole ring, a benzodiazole ring, and a carbazole ring.

[0238] R ４Ａ The group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom (hereinafter also referred to as "substituent A1") is not particularly limited, but is preferably a group having 0 to 24 carbon atoms. The halogen atom is not particularly limited, but examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The heteroatom is not particularly limited, but examples thereof include a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. The substituent A1 is not particularly limited, but is preferably, for example, a hydrogen atom or a hydrocarbon group. The hydrocarbon group may have a heteroatom or a halogen atom.

[0239] m represents an integer of 1 to 5. m preferably represents an integer of 1 to 3, and more preferably represents an integer of 1 or 2. n represents an integer of 0 to 5. n preferably represents an integer of 0 to 2, and more preferably represents an integer of 0 or 1.

[0240] When n is 2 or more, multiple R ４Ａ may be linked to form a ring. ４ＡHowever, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aromatic ring and an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0241] When X is a monovalent group (specifically, —OH, —SO ２ -OH and -CO-OH) is R ４Ａ When X is a divalent group (specifically, -NH-, -SO ２ -NH- and -CO-NH-) can constitute a partial structure in formula (I), but R ４Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0242] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the above formula (II) in the molecule, and may be a compound having at least two or more partial structures represented by the above formula (II) in the molecule. The number of partial structures represented by the above formula (I) in the molecule is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.

[0243] The hydrogen donor compound is preferably a compound having at least one partial structure represented by the following formula (III) in the molecule.

[0244]

[0245] In formula (III), X is —OH, —NH—, or —SO ２ -NH-, -SO ２ R is a group selected from the group consisting of —OH, —CO—NH—, and —CO—OH. ５Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom. p represents an integer of 1 to 5. When p represents an integer of 2 or more, multiple Xs may be the same or different. q represents an integer of 0 to 5. When q represents an integer of 2 or more, multiple R ５may be the same or different. When q is 2 or more, a plurality of R ５Ａ may be linked to form a ring. p+q is 6 or less. When all Xs are monovalent groups, R ５Ａ When at least one X is a divalent group, R ５Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

[0246] X has the same meaning as X in formula (I), and the preferred range is also the same. ５Ａ The group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a heteroatom (hereinafter also referred to as "substituent A2") is not particularly limited, but is preferably a group having 0 to 24 carbon atoms. The halogen atom is not particularly limited, but examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The heteroatom is not particularly limited, but examples thereof include a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. The substituent A2 is not particularly limited, but is preferably, for example, a hydrogen atom or a hydrocarbon group. The hydrocarbon group may have a heteroatom or a halogen atom.

[0247] p represents an integer of 1 to 5. p preferably represents an integer of 1 to 3, and more preferably represents an integer of 1 or 2. q represents an integer of 0 to 5. q preferably represents an integer of 0 to 2, and more preferably represents an integer of 0 or 1.

[0248] When q is 2 or more, a plurality of R ５Ａ may be linked to form a ring. ５Ａ However, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aromatic ring and an aliphatic hydrocarbon ring, and the number of member atoms of the ring formed is preferably 6 to 10.

[0249] The hydrogen donating group in the hydrogen donating compound is preferably —OH, —NH—, or —SO 3 from the viewpoints of preventing fading when exposed to white light and being easily compatible with the image recording layer. ２A group selected from the group consisting of —NH— and —CO—NH— is preferred, and —OH and —SO ２ A group selected from the group consisting of -NH- is more preferred. From the viewpoint of suppressing fading upon exposure to white light, the hydrogen donor compound preferably contains at least one of the above-mentioned hydrogen donor groups, more preferably contains at least two, and even more preferably contains at least three. The number of hydrogen donor groups contained in the hydrogen donor compound is not particularly limited, but is, for example, preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less.

[0250] In a preferred embodiment, the hydrogen donor compound is —OH, —NH—, or —SO ２ -NH-, -SO ２ It is preferable that the hydrogen donor compound is a compound having at least two groups selected from the group consisting of —OH, —CO—NH—, and —CO—OH in the molecule. In a preferred embodiment, the hydrogen donor compound is a compound having at least two groups selected from the group consisting of —OH and —SO ２ In a preferred embodiment, the hydrogen donor compound has at least one group selected from the group consisting of —OH and —SO ２ It is preferred that the alkyl group has at least two groups selected from the group consisting of —NH—.

[0251] The hydrogen donor compound preferably has at least one phenolic hydroxyl group. The phenolic hydroxyl group represents a hydroxyl group (—OH) directly bonded to an aromatic ring (specifically, a benzene ring). The hydrogen donor compound preferably has two or more phenolic hydroxyl groups. The hydrogen donor compound preferably has two to six phenolic hydroxyl groups, and more preferably has two to four phenolic hydroxyl groups. "Having two or more phenolic hydroxyl groups" means that an aromatic ring bonded to one phenolic hydroxyl group may further have one or more phenolic hydroxyl groups bonded thereto, or an aromatic ring different from the aromatic ring bonded to one phenolic hydroxyl group may further have one or more phenolic hydroxyl groups bonded thereto.

[0252] The hydrogen donor compound is preferably a compound represented by the following formula (IV) or a compound represented by the following formula (V).

[0253]

[0254] In formula (IV), X Ａ represents —OH. ６Ａ represents an organic group or a halogen atom. r represents an integer of 1 to 5. s represents an integer of 0 to 5. When s represents an integer of 2 or more, a plurality of R ６Ａ may be the same or different. When s is 2 or more, a plurality of R ６Ａ may be linked to form a ring. In formula (V), L represents a single bond or a divalent linking group. X Ｂ represents —OH. ７Ａ represents an organic group or a halogen atom. ｃ represents —OH. ８Ａ represents an organic group or a halogen atom. t represents an integer of 1 to 5. u represents an integer of 0 to 5. When u represents an integer of 2 or more, a plurality of R ７Ａ may be the same or different. When u is 2 or more, a plurality of R ７Ａ may be linked to form a ring. v represents an integer of 1 to 5. w represents an integer of 0 to 5. When w represents an integer of 2 or more, a plurality of R ８Ａ may be the same or different. When w is 2 or more, a plurality of R ８Ａ may be linked to form a ring.

[0255] R ６Ａ , R ７Ａ , R ８Ａ The organic group in R is not particularly limited, but examples thereof include alkyl groups and aryl groups. The alkyl group may be linear or branched, and examples thereof include alkyl groups having 1 to 10 carbon atoms. The aryl group may be monocyclic or polycyclic, and examples thereof include aryl groups having 6 to 20 carbon atoms. ６Ａ , R ７Ａ , R ８Ａ The halogen atom is not particularly limited, but may include a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

[0256] r represents an integer of 1 to 5. r preferably represents an integer of 1 to 3, more preferably 1 or 2. s represents an integer of 0 to 5. s preferably represents an integer of 0 to 3, more preferably 0 or 1. r+s is preferably 6 or less. Multiple R ６Ａ However, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aliphatic hydrocarbon ring, and the number of ring atoms in the formed ring is preferably 6 to 10.

[0257] The divalent linking group of L is not particularly limited, but examples thereof include an alkylene group, —CO—, and —SO ２ Examples of the alkylene group include -, -O-, and combinations thereof. Examples of the alkylene group include linear or branched alkylene groups having 1 to 5 carbon atoms. The alkylene group may further have a substituent. The substituent is not particularly limited, but examples include aryl groups (preferably having 6 to 10 carbon atoms). The aryl group may further have a substituent, and examples of the further substituent include a hydroxyl group.

[0258] t represents an integer of 1 to 5. t preferably represents an integer of 1 to 3, more preferably 1 or 2. u represents an integer of 0 to 5. u preferably represents an integer of 0 to 3, more preferably 0 or 1. t+u is preferably 6 or less. ７Ａ However, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aliphatic hydrocarbon ring, and the number of ring atoms in the formed ring is preferably 6 to 10.

[0259] v represents an integer of 1 to 5. v preferably represents an integer of 1 to 3, more preferably 1 or 2. w represents an integer of 0 to 5. w preferably represents an integer of 0 to 3, more preferably 0 or 1. v+w is preferably 6 or less. ８ＡHowever, the ring formed by linking may be a monocycle or a polycycle. Examples of the ring formed include an aliphatic hydrocarbon ring, and the number of ring atoms in the formed ring is preferably 6 to 10.

[0260] The hydrogen donor compound is a low molecular weight compound having a molecular weight of less than 3,000, preferably a low molecular weight compound of 1,500 or less, and more preferably a low molecular weight compound of 1,000 or less. Here, the low molecular weight compound in the present invention is not a so-called polymer or oligomer obtained by cleaving the unsaturated bond of a compound having an unsaturated bond (a so-called polymerizable monomer) using an initiator and growing the bond in a chain reaction, but a compound having a constant molecular weight of 3,000 or less (more preferably 2,000 or less, and even more preferably 1,000 or less) (a compound having substantially no molecular weight distribution).

[0261] The molecular weight of the hydrogen donor compound is not particularly limited, but is preferably at least 50, more preferably at least 100, and more preferably at least 200. In a preferred embodiment, from the viewpoints of on-press developability and printing durability, the molecular weight is preferably from 50 to 3,000, more preferably from 100 to 1,500, and even more preferably from 200 to 1,000.

[0262] Specific examples of the hydrogen donor compound are shown below, but the present invention is not limited to these.

[0263]

[0264]

[0265]

[0266] The hydrogen donor compound may be used alone or in combination of two or more. The content of the hydrogen donor compound is preferably from 0.5 to 30% by mass, more preferably from 1 to 20% by mass, and even more preferably from 1 to 10% by mass, of the total solid content of the image recording layer.

[0267] In the on-press development type lithographic printing plate, the image recording layer may contain, in addition to the above color-forming compound, an infrared absorber, an acid color former, a polymer compound, a chain transfer agent, a low-molecular-weight hydrophilic compound, an oil-sensitizing agent, and other components.

[0268] [Other Infrared Absorbents] The image recording layer may contain an infrared absorbent other than the color-forming compound. Examples of other infrared absorbents include pigments and dyes. Examples of dyes that can be used as other infrared absorbents include commercially available dyes and known dyes described in literature such as "Dye Handbook" (edited by the Society of Organic Synthetic Chemistry, published in 1970). Specific examples include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complex dyes. Particularly preferred dyes among these dyes include cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further examples include cyanine dyes and indolenine cyanine dyes. Of these, cyanine dyes are particularly preferred.

[0269] Specific examples of cyanine dyes include the compounds described in paragraphs 0017 to 0019 of JP-A-2001-133969, the compounds described in paragraphs 0016 to 0021 of JP-A-2002-023360, and the compounds described in paragraphs 0012 to 0037 of JP-A-2002-040638, preferably the compounds described in paragraphs 0034 to 0041 of JP-A-2002-278057 and paragraphs 0080 to 0086 of JP-A-2008-195018, and particularly preferably the compounds described in paragraphs 0035 to 0043 of JP-A-2007-90850, and the compounds described in paragraphs 0105 to 0113 of JP-A-2012-206495. In addition, the compounds described in paragraphs 0008 to 0009 of JP-A No. 5-5005 and paragraphs 0022 to 0025 of JP-A No. 2001-222101 can also be preferably used. As the pigment, the compounds described in paragraphs 0072 to 0076 of JP-A No. 2008-195018 are preferred.

[0270] The other infrared absorbents may be used alone or in combination of two or more. Furthermore, a pigment and a dye may be used in combination as the other infrared absorbents. From the viewpoints of color development and the UV printing durability of the resulting lithographic printing plate, the content of the other infrared absorbents in the image recording layer is preferably less than the content of the color-forming compound, and it is more preferable that the image recording layer does not contain any other infrared absorbents.

[0271] The image recording layer preferably contains an acid color former in addition to the color former having a group that is cleaved by exposure to infrared light.

[0272] [Acid Color Former] The term "acid color former" used in the present invention refers to a compound that has the property of developing or decolorizing a color and changing the color of an image recording layer when heated in a state in which it has accepted an electron-accepting compound (e.g., a proton of an acid, etc.). As the acid color former, particularly preferred are colorless compounds that have a partial skeleton such as a lactone, lactam, sultone, spiropyran, ester, or amide, and that rapidly open or cleave this partial skeleton when brought into contact with an electron-accepting compound.

[0273] Specific examples of acid color formers include those described in WO 2020 / 158138.

[0274] Among these, from the viewpoint of color-developing ability, the acid color former used in the present invention is preferably at least one compound selected from the group consisting of spiropyran compounds, spirooxazine compounds, spirolactone compounds, and spirolactam compounds. From the viewpoint of visibility, the hue of the dye after color development is preferably green, blue, or black.

[0275] Furthermore, from the viewpoints of color development and visibility, the acid color former preferably contains a leuco dye. The leuco dye is not particularly limited as long as it has a leuco structure, but it preferably has a spiro structure, and more preferably has a spirolactone ring structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is preferably a compound represented by any one of the following formulas (Le-1) to (Le-3), and more preferably a compound represented by the following formula (Le-2).

[0276]

[0277] In formulas (Le-1) to (Le-3), ERG each independently represents an electron-donating group; １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; X ５ ~X １０ each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Ra １ represents a hydrogen atom, an alkyl group, or an alkoxy group; Rb １ ~Rb ４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0278] From the viewpoints of color development and visibility of exposed areas, the electron-donating group in ERG of formulae (Le-1) to (Le-3) is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group; more preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, or an aryloxy group; still more preferably a monoalkylmonoarylamino group, a diarylamino group, a diheteroarylamino group, or a monoarylmonoheteroarylamino group; and particularly preferably a monoalkylmonoarylamino group. Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group in the ERG is preferably a di-substituted amino group having an aryl group having a substituent at at least one ortho position or a heteroaryl group having a substituent at at least one ortho position, more preferably a di-substituted amino group having a phenyl group having a substituent at at least one ortho position and an electron-donating group at the para position, even more preferably an amino group having a phenyl group having a substituent at at least one ortho position and an electron-donating group at the para position, and an aryl group or heteroaryl group, and particularly preferably an amino group having a phenyl group having a substituent at at least one ortho position and an electron-donating group at the para position, and an aryl group having an electron-donating group or a heteroaryl group having an electron-donating group. Note that, in the present invention, the ortho position in an aryl group or heteroaryl group other than a phenyl group refers to the bonding position (e.g., the 2nd position) adjacent to the bonding position 1 of the aryl group or heteroaryl group to another structure.Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group contained in the aryl group or heteroaryl group is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

[0279] X in formulas (Le-1) to (Le-3) １ ~X ４ are each independently preferably a hydrogen atom or a chlorine atom, more preferably a hydrogen atom, from the viewpoint of color development and visibility of exposed areas. ５ ~X １０ are each independently, from the viewpoint of color development and visibility of exposed areas, preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, or a cyano group, more preferably a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group, still more preferably a hydrogen atom, a halogen atom, an alkyl group, or an aryl group, and particularly preferably a hydrogen atom. １ and Y ２ From the viewpoint of color development and visibility of exposed areas, it is preferable that at least one of the two is C, and Y １ and Y ２It is more preferable that both of Ra in formulas (Le-1) to (Le-3) are C. １ From the viewpoint of color development and visibility of exposed areas, Rb is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group. １ ~Rb ４ are each independently preferably a hydrogen atom or an alkyl group, more preferably an alkyl group, and particularly preferably a methyl group, from the viewpoints of color development and visibility of exposed areas.

[0280] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is more preferably a compound represented by any one of the following formulas (Le-4) to (Le-6), and even more preferably a compound represented by the following formula (Le-5):

[0281]

[0282] In formulas (Le-4) to (Le-6), ERG each independently represents an electron-donating group; １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Ra １ represents a hydrogen atom, an alkyl group, or an alkoxy group; Rb １ ~Rb ４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0283] ERG and X in formulas (Le-4) to (Le-6) １ ~X ４ , Y １ , Y ２ , Ra １ , and Rb １ ~Rb ４are ERG and X in formulas (Le-1) to (Le-3), respectively. １ ~X ４ , Y １ , Y ２ , Ra １ , and Rb １ ~Rb ４ The same applies to the preferred embodiments.

[0284] Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is more preferably a compound represented by any one of the following formulas (Le-7) to (Le-9), and particularly preferably a compound represented by the following formula (Le-8):

[0285]

[0286] In formulas (Le-7) to (Le-9), X １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Ra １ ~Ra ４ each independently represents a hydrogen atom, an alkyl group, or an alkoxy group; Rb １ ~Rb ４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group; １ and Rc ２ each independently represents an aryl group or a heteroaryl group.

[0287] X in formulas (Le-7) to (Le-9) １ ~X ４ , Y １ and Y ２ represents X in formulas (Le-1) to (Le-3). １ ~X ４ , Y １ and Y ２The same applies to the preferred embodiments. １ ~Ra ４ are each independently preferably an alkyl group or an alkoxy group, more preferably an alkoxy group, and particularly preferably a methoxy group, from the viewpoints of color development and visibility of exposed areas. １ ~Rb ４ are each independently preferably a hydrogen atom or an aryl group substituted with an alkyl group or an alkoxy group, more preferably an alkyl group, and particularly preferably a methyl group, from the viewpoints of color development and visibility of exposed areas. １ and Rc ２ are each independently preferably a phenyl group or an alkylphenyl group, more preferably a phenyl group, from the viewpoints of color development and visibility of exposed areas. １ and Rc ２ are each independently, from the viewpoints of color development and visibility of exposed areas, preferably an aryl group having a substituent at at least one ortho position or a heteroaryl group having a substituent at at least one ortho position, more preferably an aryl group having a substituent at at least one ortho position, still more preferably a phenyl group having a substituent at at least one ortho position, and particularly preferably a phenyl group having a substituent at at least one ortho position and an electron-donating group at the para position. １ and Rc ２ In addition, in the formula (Le-8), from the viewpoint of color development and visibility of the exposed area, X １ ~X ４ is a hydrogen atom, and Y １ and Y ２ is preferably C. Furthermore, in formula (Le-8), from the viewpoint of color development and visibility of exposed areas, it is preferable that Rb １ and Rb ２are each independently an aryl group substituted with an alkyl group or an alkoxy group. １ and Rb ２ are each independently preferably an aryl group or a heteroaryl group, more preferably an aryl group, further preferably an aryl group having an electron-donating group, and particularly preferably a phenyl group having an electron-donating group at the para position. １ , Rb ２ , Rc １ and Rc ２ From the viewpoints of color development and visibility of exposed areas, the electron-donating group in is preferably an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, more preferably an alkoxy group, an aryloxy group, a heteroaryloxy group, or an alkyl group, and particularly preferably an alkoxy group.

[0288] Furthermore, from the viewpoint of color development and visibility of exposed areas, it is preferable that the acid color former contains a compound represented by the following formula (Le-10).

[0289]

[0290] In formula (Le-10), Ar １ each independently represents an aryl group or a heteroaryl group; Ar ２ each independently represents an aryl group having a substituent at at least one ortho-position, or a heteroaryl group having a substituent at at least one ortho-position.

[0291] Ar in formula (Le-10) １ represents Rb in formulas (Le-7) to (Le-9). １ and Rb ２The same applies to the preferred embodiments of Ar in formula (Le-10). ２ is Rc in formula (Le-7) to formula (Le-9). １ and Rc ２ The same applies to the preferred embodiments.

[0292] Furthermore, from the viewpoints of color development and visibility of exposed areas, it is preferable that the acid color former contains a compound represented by the following formula (Le-A).

[0293]

[0294] In formula (Le-A), each ERG independently represents an electron-donating group; n11 represents an integer of 1 to 5; n12 represents an integer of 0 to 2; X １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Rb ４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0295] ERG, X in formula (Le-A) １ ~X ４ , Y １ , Y ２ , and Rb ４ are ERG and X in formulas (Le-1) to (Le-3), respectively. １ ~X ４ , Y １ , Y ２ , and Rb ４ In formula (Le-A), n11 is preferably an integer of 1 to 3, and more preferably 1 or 2. In formula (Le-A), n12 is preferably 0 or 1, and more preferably 0.

[0296] Furthermore, from the viewpoints of color development and visibility of exposed areas, it is preferable that the acid color former contains a compound represented by the following formula (Le-11).

[0297]

[0298] In formula (Le-11), each ERG independently represents an electron-donating group; n11 represents an integer of 1 to 5; X １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a dialkylanilino group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and Rb ２ and Rb ４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0299] ERG and X in formula (Le-11) １ ~X ４ , Y １ , Y ２ , Rb ２ , and Rb ４ are ERG and X in formulas (Le-1) to (Le-3), respectively. １ ~X ４ , Y １ , Y ２ , Rb ２ , and Rb ４ In formula (Le-11), n11 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0300] The alkyl group in formula (Le-1) to formula (Le-9), formula (Le-A), or formula (Le-11) may be linear, branched, or have a ring structure. The number of carbon atoms in the alkyl group in formula (Le-1) to formula (Le-9), formula (Le-A), or formula (Le-11) is preferably 1 to 20, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 or 2. The number of carbon atoms in the aryl group in formula (Le-1) to formula (Le-11), or formula (Le-A) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8. Specific examples of the aryl group in formula (Le-1) to formula (Le-11), or formula (Le-A) include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group, which may have a substituent. Specific examples of the heteroaryl group in Formulae (Le-1) to (Le-11) and (Le-A) include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group, each of which may have a substituent.

[0301] Furthermore, each of the monovalent organic groups, alkyl groups, aryl groups, heteroaryl groups, dialkylanilino groups, alkylamino groups, alkoxy groups, etc. in Formulas (Le-1) to (Le-11) and Formula (Le-A) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, and a cyano group. Furthermore, these substituents may be further substituted with other substituents.

[0302] In addition, from the viewpoints of color development and visibility of exposed areas, the acid color former preferably contains a compound represented by either of the following formulas 3a and 3b. In a preferred embodiment, the acid color former is a compound represented by either of the following formulas 3a and 3b.

[0303]

[0304] In formula (3a), Ar １ , Ar ２ each independently represents an aryl group or a heteroaryl group; R １０ , R １１ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group. In formula (3b), each ERG independently represents an electron-donating group, n represents an integer of 1 to 5, and X １ ~X ４ each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group; Y １ and Y ２ each independently represents C or N, Y １ If is N, then X １ does not exist, and Y ２ If is N, then X ４ does not exist, and R １２ and R １３ each independently represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

[0305] The alkyl group in formulas (3a) and (3b) may be linear, branched, or have a ring structure. The number of carbon atoms in the alkyl group in formulas (3a) and (3b) is preferably 1 to 20, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 or 2. The number of carbon atoms in the aryl group in formulas (3a) and (3b) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8. Specific examples of the aryl group in formulas (3a) and (3b) include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group, each of which may have a substituent. Specific examples of the heteroaryl group in formulas (3a) and (3b) include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group, each of which may have a substituent. ERG in formula (3b) has the same meaning as ERG in formulas (Le-1) to (Le-3), and preferred embodiments are also the same. n in formula (3b) is preferably an integer of 1 to 3, more preferably 1 or 2. The monovalent organic group in formula (3b) is X in formulas (Le-2) to (Le-3). ５ ~X １０ The preferred embodiments are also the same as those of the monovalent organic group represented by the formula (I).

[0306] Furthermore, each group such as a monovalent organic group, an alkyl group, an aryl group, or a heteroaryl group in formulas (3a) to (3b) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, and a cyano group. Furthermore, these substituents may be further substituted with other substituents.

[0307] The leuco dye having the phthalide structure or fluoran structure that can be suitably used is not particularly limited, but examples thereof include the compounds described in

[0141] to

[0150] of JP-A No. 2023-98447.

[0308] In addition, the compounds described in paragraphs

[0151] to

[0188] of JP-A No. 2023-98447 can also be used as the acid color former.

[0309] These acid color formers may be used alone or in combination of two or more. The content of the acid color former is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass, based on the total solid content of the image recording layer.

[0310] (Polymer Compound) The polymer compound may function as a binder polymer in the image recording layer, or may be present in the image recording layer as a particulate polymer compound (polymer particles).

[0311] <Binder Polymer> As the binder polymer, a polymer having film-forming properties is preferred, and preferred examples thereof include a (meth)acrylic resin, a polyvinyl acetal resin, and a polyurethane resin.

[0312] The binder polymer used in the image recording layer is preferably a binder polymer having an alkylene oxide chain. The binder polymer having an alkylene oxide chain may have a poly(alkylene oxide) moiety in the main chain or in the side chain. It may also be a graft polymer having a poly(alkylene oxide) moiety in the side chain, or a block copolymer of a block composed of a repeating unit containing a poly(alkylene oxide) moiety and a block composed of a repeating unit not containing an (alkylene oxide) moiety. 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.

[0313] The alkylene oxide is preferably an alkylene oxide having 2 to 6 carbon atoms, and ethylene oxide or propylene oxide is particularly preferred. The number of repeating alkylene oxides in the poly(alkylene oxide) moiety is preferably 2 to 120, more preferably 2 to 70, and even more preferably 2 to 50. If the number of repeating alkylene oxides is 120 or less, a decrease in printing durability due to abrasion and a decrease in printing durability due to deterioration of ink receptivity are suppressed, which is preferable.

[0314] The poly(alkylene oxide) moiety is preferably contained as a side chain of the binder polymer in the form of a structure represented by the following formula (AO), and more preferably contained as a side chain of the (meth)acrylic resin in the form of a structure represented by the following formula (AO).

[0315]

[0316] In formula (AO), y represents 2 to 120, R １ represents a hydrogen atom or an alkyl group, R ２represents a hydrogen atom or a monovalent organic group. As the monovalent organic group, an alkyl group having 1 to 6 carbon atoms is preferred. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an isohexyl group, a 1,1-dimethylbutyl group, a 2,2-dimethylbutyl group, a cyclopentyl group, and a cyclohexyl group. In formula (AO), y is preferably 2 to 70, and more preferably 2 to 50. R １ is preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom. ２ is particularly preferably a hydrogen atom or a methyl group.

[0317] The binder polymer may be crosslinkable to improve the film strength of the image area. To impart crosslinkability to a polymer, a crosslinkable functional group such as an ethylenically unsaturated bond may be introduced into the main chain or side chain of the polymer. The crosslinkable functional group may be introduced by copolymerization or by a polymer reaction. Examples of polymers having an ethylenically unsaturated bond in the main chain of the molecule include poly-1,4-butadiene and poly-1,4-isoprene. Examples of polymers having an ethylenically unsaturated bond in the side chain of the molecule include polymers of esters or amides of acrylic acid or methacrylic acid, in which the ester or amide residue (the R in -COOR or -CONHR) has an ethylenically unsaturated bond.

[0318] Examples of the residue having an ethylenically unsaturated bond (the above R) include —(CH ２ ) ｎ CR １Ａ =CR ２Ａ R ３Ａ , -(CH ２ O) ｎ CH ２ CR １Ａ =CR ２Ａ R ３Ａ , -(CH ２ CH ２ O) ｎ CH ２ CR １Ａ =CR ２Ａ R３Ａ , -(CH ２ ) ｎ NH-CO-O-CH ２ CR １Ａ =CR ２Ａ R ３Ａ , -(CH ２ ) ｎ -O-CO-CR １Ａ =CR ２Ａ R ３Ａ and -(CH ２ CH ２ O) ２ -X Ａ (In the formula, R Ａ１ ~R Ａ３ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an alkoxy group, or an aryloxy group; R Ａ１ and R Ａ２ or R Ａ３ may be bonded to each other to form a ring. n represents an integer of 1 to 10. X Ａ represents a dicyclopentadienyl residue.

[0319] Specific examples of the ester residue include -CH ２ CH=CH ２ , -CH ２ CH ２ O-CH ２ CH=CH ２ , -CH ２ C(CH ３ ) = CH ２ , -CH ２ CH=CH-C ６ H ５ , -CH ２ CH ２ OCOCH=CH-C ６ H ５ , -CH ２ CH ２ -NHCOO-CH ２ CH=CH ２ and -CH ２ CH ２ Specific examples of the amide residue include -O-X (wherein X represents a dicyclopentadienyl residue). ２ CH=CH ２ , -CH ２ CH２ -Y (wherein Y represents a cyclohexene residue) and -CH ２ CH ２ -OCO-CH=CH ２ Examples include:

[0320] A crosslinkable binder polymer is cured by, for example, addition polymerization of a crosslinkable functional group with a free radical (a polymerization initiation radical or a propagating radical in the polymerization process of a polymerizable compound) between polymer molecules, either directly or via a polymerization chain of the polymerizable compound, forming a crosslink between polymer molecules. Alternatively, an atom in the polymer (e.g., a hydrogen atom on a carbon atom adjacent to a functional crosslinking group) is abstracted by the free radical to generate a polymer radical, which then bonds to each other to form a crosslink between polymer molecules, thereby curing.

[0321] The content of crosslinkable groups in the binder polymer (the content of radically polymerizable unsaturated double bonds determined by iodometric titration) is preferably 0.1 to 10.0 mmol, more preferably 1.0 to 7.0 mmol, and even more preferably 2.0 to 5.5 mmol, per 1 g of the binder polymer, from the viewpoints of good sensitivity and good storage stability.

[0322] Specific examples 1 to 11 of binder polymers are shown below, but the present invention is not limited to these. In the example compounds below, the numerical value written next to each repeating unit (the numerical value written next to the main chain repeating unit) indicates the mole percentage of the repeating unit. The numerical value written next to the side chain repeating unit indicates the number of repeats of the repeating portion. Furthermore, Me represents a methyl group, Et represents an ethyl group, and Ph represents a phenyl group.

[0323]

[0324]

[0325] The molecular weight of the binder polymer is, in terms of polystyrene equivalent weight average molecular weight (Mw) measured by GPC method, 2,000 or more, preferably 5,000 or more, and more preferably 10,000 to 300,000.

[0326] If necessary, a hydrophilic polymer such as polyacrylic acid or polyvinyl alcohol described in JP-A-2008-195018 can be used in combination. Also, a lipophilic polymer and a hydrophilic polymer can be used in combination.

[0327] The binder polymer may be used alone or in combination of two or more. The content of the binder polymer is preferably from 1 to 90% by mass, more preferably from 5 to 80% by mass, of the total solid content of the image recording layer.

[0328] <Particulate Polymer Compound (Polymer Particles)> The image recording layer preferably contains polymer particles. The polymer particles contribute to improving on-press developability. The polymer particles are preferably polymer particles that can convert the image recording layer to hydrophobicity when heat is applied. The polymer particles are preferably at least one selected from hydrophobic thermoplastic polymer particles, heat-reactive polymer particles, polymer particles having a polymerizable group, microcapsules encapsulating a hydrophobic compound, and microgels (crosslinked polymer particles).

[0329] Suitable examples of hydrophobic thermoplastic polymer particles include those described in Research Disclosure No. 33303 published in January 1992, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250, and European Patent No. 931647. Specific examples of polymers constituting the hydrophobic thermoplastic polymer particles include homopolymers or copolymers of monomers such as ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinylcarbazole, and acrylates or methacrylates having a polyalkylene structure, or mixtures thereof. Preferred examples include polystyrene, copolymers containing styrene and acrylonitrile, and polymethyl methacrylate. The average particle size of the hydrophobic thermoplastic polymer particles is preferably 0.01 to 2.0 μm.

[0330] The thermally reactive polymer particles include polymer particles having a thermally reactive group, which form a hydrophobic region by crosslinking through a thermal reaction and by changing the functional group.

[0331] As the heat-reactive group in the polymer particles having heat-reactive group, as long as it can form chemical bond, the functional group that can undergo any reaction can be used, and polymerizable group is preferred.Its example can suitably be mentioned the ethylenically unsaturated group (such as acryloyl group, methacryloyl group, vinyl group, allyl group etc.) that undergoes radical polymerization reaction, cation polymerizable group (such as vinyl group, vinyloxy group, epoxy group, oxetanyl group etc.), the isocyanato group or its block compound that undergoes addition reaction, epoxy group, vinyloxy group and the functional group that has active hydrogen atom that is their reactive partner (such as amino group, hydroxy group, carboxy group etc.), the carboxy group that undergoes condensation reaction and the hydroxy group or amino group that is their reactive partner, the acid anhydride that undergoes ring-opening addition reaction and the amino group or hydroxy group that is their reactive partner etc.

[0332] Examples of microcapsules include those in which all or part of the components of the image recording layer are encapsulated in microcapsules, as described in JP-A Nos. 2001-277740 and 2001-277742. The components of the image recording layer can also be contained outside the microcapsules. A preferred embodiment of the image recording layer containing microcapsules is one in which hydrophobic components are encapsulated in microcapsules and hydrophilic components are contained outside the microcapsules.

[0333] The microgel (crosslinked polymer particle) may contain a part of the constituent components of the image recording layer in at least one of its interior and surface. In particular, from the viewpoint of image formation sensitivity and printing durability, it is preferable to have a reactive microgel having a radical polymerizable group on its surface.

[0334] Known methods can be used to microencapsulate or microgelate the components of the image-recording layer. The average particle size of the microcapsules or microgel is preferably 0.01 to 3.0 μm, more preferably 0.05 to 2.0 μm, and particularly preferably 0.10 to 1.0 μm. Good resolution and stability over time can be obtained within this range.

[0335] The polymer particles may be used alone or in combination of two or more kinds. The content of the polymer particles is preferably from 5 to 90% by mass, more preferably from 5 to 80% by mass, and even more preferably from 10 to 75% by mass, of the total solid content of the image recording layer.

[0336] In a preferred embodiment, the polymer particles have a hydrophobic main chain and preferably contain both i) a structural unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a structural unit having a pendant group containing a hydrophilic poly(alkylene oxide) segment. The hydrophobic main chain is preferably an acrylic resin chain. Examples of the pendant cyano group include -[CH ２ CH(C≡N)-] or -[CH ２ C(CH ３)(C≡N)—] is preferred. The structural unit having a pendant cyano group can be easily derived from an ethylenically unsaturated monomer, such as acrylonitrile or methacrylonitrile, or a combination thereof. The alkylene oxide in the hydrophilic poly(alkylene oxide) segment is preferably ethylene oxide or propylene oxide, and more preferably ethylene oxide. The number of repeating alkylene oxide structures in the hydrophilic poly(alkylene oxide) segment is preferably 10 to 100, more preferably 25 to 75, and even more preferably 40 to 50. Preferred examples of resin particles having a hydrophobic main chain and including both i) a structural unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a structural unit having a pendant group including a hydrophilic poly(alkylene oxide) segment include those described in paragraphs 0039 to 0068 of JP-T-2008-503365.

[0337] In one preferred embodiment, the polymer particles are obtained by reacting a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in the molecule with isophorone diisocyanate, with a compound having active hydrogen.

[0338] The average particle size of the polymer particles is preferably from 0.01 to 3.0 μm, more preferably from 0.05 to 2.0 μm, and particularly preferably from 0.10 to 1.0 μm, within which range good resolution and stability over time can be obtained.

[0339] The polymer particles may be used alone or in combination of two or more kinds. The content of the polymer particles is preferably from 5 to 90% by mass, more preferably from 5 to 80% by mass, and even more preferably from 10 to 75% by mass, of the total solid content of the image recording layer.

[0340] The polymer compound contained in the image recording layer is preferably a polymer compound containing a structural unit derived from a styrene compound and / or a structural unit derived from an acrylonitrile compound. From the viewpoint of contributing to on-press developability, this polymer compound can be suitably used as a binder polymer or polymer particles.

[0341] Examples of the styrene compound include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene, with styrene being preferred.

[0342] Examples of the acrylonitrile compound include acrylonitrile and methacrylonitrile, with acrylonitrile being preferred.

[0343] In a polymer compound containing a styrene compound and an acrylonitrile compound as constituent units, the composition ratio of the constituent units derived from the styrene compound to the constituent units derived from the acrylonitrile compound is preferably 4:1 to 1:4.

[0344] (Chain transfer agent) The chain transfer agent contributes to improving the printing durability of a lithographic printing plate produced from the lithographic printing plate precursor. As the chain transfer agent, a thiol compound is preferred, and from the viewpoint of boiling point (difficulty in volatilization), a thiol having 7 or more carbon atoms is more preferred, and a compound having a mercapto group on an aromatic ring (aromatic thiol compound) is even more preferred. The thiol compound is preferably a monofunctional thiol compound.

[0345] Specific examples of the chain transfer agent include the following compounds:

[0346]

[0347]

[0348]

[0349]

[0350] The chain transfer agent may be used alone or in combination of two or more. The content of the chain transfer agent is preferably from 0.01 to 50% by mass, more preferably from 0.05 to 40% by mass, and even more preferably from 0.1 to 30% by mass, of the total solid content of the image recording layer.

[0351] (Oil-sensitizing agent) The oil-sensitizing agent contributes to improving the ink receptivity (hereinafter also simply referred to as "ink receptivity") of a lithographic printing plate prepared from the lithographic printing plate precursor. Examples of oil-sensitizing agents include phosphonium compounds, nitrogen-containing low-molecular-weight compounds, and ammonium group-containing polymers. In particular, when the lithographic printing plate precursor has a protective layer containing an inorganic layered compound, these compounds function as a surface coating agent for the inorganic layered compound and have the function of suppressing a decrease in ink receptivity during printing due to the inorganic layered compound. As the oil-sensitizing agent, a phosphonium compound, a nitrogen-containing low-molecular-weight compound, and an ammonium group-containing polymer are preferably used in combination, and a phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer are more preferably used in combination. As the oil-sensitizing agent, those described in paragraphs

[0151] to

[0155] of WO 2020 / 137919 can be used.

[0352] The content of the oil sensitizer is preferably from 0.01 to 30% by mass, more preferably from 0.1 to 15% by mass, and even more preferably from 1 to 10% by mass, based on the total solid content of the image recording layer.

[0353] (Other Components) The image recording layer may contain other components such as a surfactant, a printing-out agent, a polymerization inhibitor, a higher fatty acid derivative, a plasticizer, inorganic particles, an inorganic layer compound, etc. Specifically, the components described in paragraphs 0114 to 0159 of JP-A-2008-284817 can be used.

[0354] The content of the non-particulate polymer compound having a weight average molecular weight of more than 15,000 is preferably 5% by mass or less, and more preferably 4% by mass or less, of the total solid content of the image recording layer.

[0355] (Formation of Image Recording Layer) The image recording layer can be formed by dispersing or dissolving the necessary components described above in a known solvent as appropriate, and then applying the coating solution by a known method such as bar coater coating, followed by drying, as described in paragraphs 0142 and 0143 of JP-A No. 2008-195018. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but is preferably 0.3 to 3.0 g / m from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer. ２ The degree is preferable.

[0356] From the viewpoint of imparting on-press developability, the image recording layer is preferably water-soluble or water-dispersible. Here, "water-soluble" means that 0.1 g or more of the image recording layer dissolves in 100 g of water at 20° C., and "water-dispersible" means that the image recording layer is uniformly dispersed in water at 20° C.

[0357] The on-press development type lithographic printing plate precursor according to the present invention may have an undercoat layer (sometimes called an intermediate layer) between the image recording layer and the support.

[0358] [Undercoat layer] The undercoat layer strengthens the adhesion between the support and the image recording layer in the exposed areas and facilitates peeling of the image recording layer from the support in the unexposed areas, thereby contributing to improving developability without impairing printing durability. In addition, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, thereby preventing the heat generated by exposure from diffusing to the support and reducing sensitivity.

[0359] The compound used in the undercoat layer may be a polymer having an adsorptive group and a hydrophilic group capable of adsorbing to the support surface. In order to improve adhesion to the image recording layer, a polymer having an adsorptive group and a hydrophilic group and further having a crosslinkable group is preferred. The compound used in the undercoat layer may be a low molecular weight compound or a polymer. Two or more compounds may be mixed together as needed.

[0360] When the compound used in the undercoat layer is a polymer, a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group is preferred. Examples of the adsorptive group that can be adsorbed onto the support surface include a phenolic hydroxy group, a carboxy group, a -PO ３ H ２ , -OPO ３ H ２ , -CONHSO ２ -, -SO ２ NHSO ２ --, --COCH ２ COCH ３ is preferred. As the hydrophilic group, a sulfo group or a salt thereof, or a salt of a carboxy group is preferred. As the crosslinkable group, an acryl group, a methacryl group, an acrylamide group, a methacrylamide group, an allyl group, or the like is preferred. The polymer may have a crosslinkable group introduced by salt formation between a polar substituent of the polymer and a compound having an ethylenically unsaturated bond and a substituent having an opposite charge to the polar substituent, or may be further copolymerized with a monomer other than the above, preferably a hydrophilic monomer.

[0361] Specifically, preferred examples include silane coupling agents having an addition-polymerizable ethylenic double bond reactive group, as described in JP-A-10-282679, and phosphorus compounds having an ethylenic double bond reactive group, as described in JP-A-2-304441. Also preferred are low-molecular-weight or high-molecular-weight compounds having a crosslinkable group (preferably an ethylenically unsaturated bond group), a functional group that interacts with the support surface, and a hydrophilic group, as described in JP-A-2005-238816, JP-A-2005-125749, JP-A-2006-239867, and JP-A-2006-215263. More preferred examples include high-molecular-weight polymers having an adsorptive group, a hydrophilic group, and a crosslinkable group that can be adsorbed to the support surface, as described in JP-A-2005-125749 and JP-A-2006-188038.

[0362] The content of ethylenically unsaturated bond groups in the polymer used in the undercoat layer is preferably 0.1 to 10.0 mmol, more preferably 0.2 to 5.5 mmol, per 1 g of the polymer. The weight-average molecular weight (Mw) of the polymer used in the undercoat layer is preferably 5,000 or more, more preferably 10,000 to 300,000.

[0363] In addition to the above-described compounds for use in an undercoat layer, the undercoat layer may contain, in order to prevent staining over time, a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, a compound having an amino group or a functional group having polymerization inhibitory ability and a group that interacts with the support surface (for example, 1,4-diazabicyclo[2.2.2]octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, etc.), etc.

[0364] The undercoat layer can be formed by coating and drying using a known method. The coating amount (solid content) of the undercoat layer after drying is 0.1 to 100 mg / m ２ is preferred, and 1 to 30 mg / m ２ is more preferred.

[0365] The on-press development type lithographic printing plate precursor according to the present invention may or may not have a protective layer on the image recording layer.

[0366] [Protective Layer] The protective layer has the function of inhibiting image formation inhibiting reactions by blocking oxygen, as well as the function of preventing scratches on the image recording layer and ablation during exposure to high-intensity laser light.

[0367] Protective layers with such properties are described, for example, in U.S. Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. The low-oxygen-permeable polymer used in the protective layer can be either a water-soluble polymer or a water-insoluble polymer, and two or more types can be mixed as needed. Specific examples include polyvinyl alcohol resins (including polyvinyl alcohol and modified polyvinyl alcohol), polyvinylpyrrolidone, water-soluble cellulose derivatives, and poly(meth)acrylonitrile. Suitable polyvinyl alcohols are those with a saponification degree of 50% or higher. The saponification degree of polyvinyl alcohol is preferably 60% or higher, more preferably 70% or higher, and even more preferably 85% or higher. There is no particular upper limit to the saponification degree, as long as it is 100% or lower. The saponification degree can be measured according to the method described in JIS K 6726:1994. Acid-modified polyvinyl alcohols having carboxy or sulfo groups are preferably used as modified polyvinyl alcohols. Specific examples include modified polyvinyl alcohols described in JP-A Nos. 2005-250216 and 2006-259137. Of the water-soluble polymers, polyvinyl alcohol resins are preferred.

[0368] The protective layer preferably contains an inorganic layer compound to enhance oxygen blocking properties. The inorganic layer compound is a thin, tabular particle, and examples thereof include mica group such as natural mica and synthetic mica, and a compound of the formula: 3MgO.4SiO.H ２ Examples of the inorganic layered compound include talc, taeniolite, montmorillonite, saponite, hectorite, and zirconium phosphate represented by the formula: A(B, C) ２－５ D ４ O １０ (OH, F, O) ２ [wherein A is any of K, Na, and Ca, B and C are any of Fe(II), Fe(III), Mn, Al, Mg, and V, and D is Si or Al.]

[0369] In the mica group, natural micas include muscovite, sodalite, phlogopite, biotite, and lepidolite. Synthetic micas include fluorphlogopite KMg. ３ (AlSi ３ O １０ ) F ２ , potassium tetrasilicic mica KMg ２．５ Si ４ O １０ ) F ２ Non-swelling mica such as Na tetrasilicic mica NaMg ２．５ (Si ４ O １０ ) F ２ , Na or Li taeniolite (Na, Li) Mg ２ Li(Si ４ O １０ ) F ２ , montmorillonite-based Na or Li hectorite (Na, Li) １／８ Mg ２／５ Li １／８ (Si ４ O １０ ) F ２ Examples of suitable micas include swellable micas such as those listed above. Synthetic smectite is also useful.

[0370] Among mica compounds, fluorine-based swellable mica is particularly useful. That is, swellable synthetic mica has a layered structure consisting of unit crystal lattice layers with a thickness of about 10 to 15 Å, and the metal atom substitution within the lattice is significantly larger than that of other clay minerals. As a result, the lattice layers have a positive charge deficiency, and to compensate for this, Li is introduced between the layers. ＋ , Na ＋ , Ca ２＋ , Mg ２＋ The cations present between these layers are called exchangeable cations and can be exchanged with various cations. In particular, the cations between the layers are Li ＋ , Na ＋ In the case of mica, the ionic radius is small, so the bonds between the layered crystal lattices are weak, and it swells greatly in water. When shear is applied in this state, it cleaves easily and forms a stable sol in water. Swellable synthetic mica has a strong tendency in this regard, and is particularly preferred.

[0371] Regarding the shape of the mica compound, from the viewpoint of diffusion control, the thinner the thickness, the better, and the larger the planar size, the better, as long as it does not impair the smoothness of the coated surface or the transmittance of actinic rays. Therefore, the aspect ratio is preferably 20 or more, more preferably 100 or more, and particularly preferably 200 or more. The aspect ratio is the ratio of the major axis to the thickness of the particle, and can be measured, for example, from a projection view of a particle in a micrograph. The larger the aspect ratio, the greater the effect obtained.

[0372] The particle size of the mica compound is preferably 0.3 to 20 μm, more preferably 0.5 to 10 μm, and particularly preferably 1 to 5 μm, in terms of average major axis. The average particle thickness is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.01 μm or less. Specifically, for example, in the case of swellable synthetic mica, a representative compound, a preferred embodiment is one in which the thickness is about 1 to 50 nm and the face size (major axis) is about 1 to 20 μm.

[0373] The content of the inorganic layer compound is preferably 0 to 60% by mass, more preferably 3 to 50% by mass, based on the total solid content of the protective layer. Even when multiple types of inorganic layer compounds are used in combination, the total amount of the inorganic layer compounds is preferably within the above content range. Within the above range, oxygen barrier properties are improved, good sensitivity is obtained, and a decrease in ink receptivity can be prevented. The content of the inorganic layer compound is 0.01 to 100 mg / m ２ is preferred, and 5 to 80 mg / m ２ More preferably, 5 to 50 mg / m ２ is particularly preferred.

[0374] The protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coating properties, inorganic fine particles for controlling surface slippage, etc. The protective layer may also contain an oil-sensitizing agent as described for the image-recording layer.

[0375] The protective layer can be formed by coating and drying using a known method. The coating amount (solid content) of the protective layer after drying is 0.01 to 10 g / m ２ is preferred, and 0.02 to 3 g / m ２ More preferably, 0.02 to 1 g / m２ is particularly preferred.

[0376] The on-press development type lithographic printing plate precursor according to the present invention may have a droop shape at the edge portion.

[0377]

[0023] Figure 3 is a schematic diagram showing the cross-sectional shape of the edge of a lithographic printing plate precursor. In Figure 3, a lithographic printing plate precursor 1 has a sag 2 at its edge. The distance X from the upper end of an edge surface 1c of the lithographic printing plate precursor 1 (the boundary point between the sag 2 and the edge surface 1c) to the intersection point between an extension of the edge surface 1c and an extension of the image recording layer surface 1a (protective layer surface if a protective layer is formed) is referred to as the "sag amount X," and the distance Y from the point where the image recording layer surface 1a of the lithographic printing plate precursor 1 starts to sag to the intersection point is referred to as the "sag width Y."

[0378] Regarding the sagging shape of the edge, the sagging amount X is preferably 25 μm or more, more preferably 35 μm or more, and even more preferably 40 μm or more. The upper limit of the sagging amount X is preferably 150 μm from the viewpoint of preventing deterioration of on-press developability due to deterioration of the edge surface condition. Deterioration of on-press developability may cause ink to adhere to the remaining image recording layer, resulting in edge smearing. If the sagging amount X is too small, ink adhered to the edge may be more likely to transfer to the blanket, resulting in edge smearing. When the sagging amount X is in the range of 25 to 150 μm, a small sagging width Y may increase the occurrence of cracks at the edge, which may result in accumulation of printing ink there, resulting in edge smearing. From this viewpoint, the sagging width Y is preferably in the range of 70 to 300 μm, more preferably 80 to 250 μm. The above sagging amount and sagging width ranges are not related to the edge shape of the support surface 1 b of the lithographic printing plate precursor 1. Generally, at the edge of the lithographic printing plate precursor 1, sagging occurs at the boundary B between the image recording layer and the support, and on the support surface 1b, similar to the image recording layer surface 1a.

[0379] The formation of the drooped edge can be achieved, for example, by adjusting the cutting conditions of the lithographic printing plate precursor. Specifically, this can be achieved by adjusting the gap, biting depth, blade angle, etc. between the upper and lower cutting blades of a slitter device used to cut the lithographic printing plate precursor. FIG. 4 is a conceptual diagram showing an example of the cutting section of a slitter device. The slitter device has a pair of upper and lower cutting blades 10 and 20 arranged one above the other. The cutting blades 10 and 20 are circular blades on a disc, and the upper cutting blades 10a and 10b are coaxially supported on a rotating shaft 11, and the lower cutting blades 20a and 20b are coaxially supported on a rotating shaft 21. The upper cutting blades 10a and 10b and the lower cutting blades 20a and 20b rotate in opposite directions. The planographic printing plate precursor 30 is cut to a predetermined width by passing it between the upper cutting blades 10a, 10b and the lower cutting blades 20a, 20b. By adjusting the gap between the upper cutting blade 10a and the lower cutting blade 20a and the gap between the upper cutting blade 10b and the lower cutting blade 20b in the cutting section of the slitter device, it is possible to form an edge having a drooped shape.

[0380] The on-press development type lithographic printing plate precursor according to the present invention preferably has an arithmetic mean height Sa of the outermost layer surface on the side opposite to the side having the image recording layer of 0.3 to 20 μm. Here, "opposite to the side having the image recording layer" means the side opposite to the side having the image recording layer, with the support as the reference. The on-press development type lithographic printing plate precursor according to the present invention preferably has an arithmetic mean height Sa of the outermost layer surface on the side having the image recording layer of 0.3 to 20 μm. Here, "side having the image recording layer" means the side having the image recording layer, with the support as the reference. By providing an outermost layer surface with such properties, the on-press development type lithographic printing plate precursor according to the present invention is excellent in performance, such as prevention of multiple feeding of plates in the step of removing the plates from the stack, prevention of scratches caused by the convex portions provided on the outermost layer surface of the plates, and prevention of development delay caused by the convex portions provided on the outermost layer surface of the plates, even when the plates are stacked without an interleaf paper sandwiched between them (also referred to as "interleaf-less").

[0381] The outermost layer surface on the side opposite to the side having the image recording layer is the surface of the backcoat layer if a backcoat layer is present on the opposite side, and is the surface of the support if no layer is present on the opposite side. For example, when protrusions described below are formed, the lithographic printing plate precursor may have the backcoat layer as the outermost layer and a plurality of protrusions containing a polymer compound on the backcoat layer, or the support as the outermost layer and a plurality of protrusions containing a polymer compound on the support.

[0382] When the image recording layer or the protective layer is the outermost layer, the outermost surface on the side having the image recording layer is the surface of the image recording layer or the surface of the protective layer. For example, when protrusions described later are formed, the lithographic printing plate precursor may have the image recording layer or the protective layer as the outermost layer, and may have a plurality of protrusions containing a polymer compound on the image recording layer or the protective layer.

[0383] The arithmetic mean height Sa of the outermost layer surface on the side opposite to the side having the image recording layer is more preferably 0.5 to 10 μm, and even more preferably 0.5 to 7 μm. The arithmetic mean height Sa of the outermost layer surface on the side having the image recording layer is more preferably 0.5 to 10 μm, and even more preferably 0.5 to 7 μm.

[0384] The arithmetic mean height Sa of the outermost layer surface is measured in accordance with the method described in ISO 25178. Specifically, using a Micromap MM3200-M100 manufactured by Ryoka Systems Co., Ltd., measurements are taken at three or more locations selected from the same sample, and the average value of these measurements is taken as the arithmetic mean height Sa. The measurement range is a 500 μm × 500 μm area randomly selected from the sample surface.

[0385] To achieve the requirement that the arithmetic mean height Sa of the outermost layer surface be 0.3 to 20 μm, it is preferable that the outermost layer have an uneven shape. Specific examples include an embodiment in which the outermost layer contains particles with an average particle size of 0.5 to 20 μm (Embodiment 1), and an embodiment in which the outermost layer has a plurality of protrusions containing a polymer compound as a main component (Embodiment 2). Here, the main component refers to the component with the highest content (mass %).

[0386] In Aspect 1, the particles having an average particle size of 0.5 to 20 μm are not particularly limited, but are preferably at least one type of particles selected from organic resin particles and inorganic particles. The particles described in paragraphs

[0150] to

[0166] of International Publication No. 2022-138880 can be used.

[0387] In the first embodiment, the average particle size of the particles is preferably 0.5 to 10 μm, more preferably 0.5 to 5 μm.

[0388] The average particle size of particles means the volume average particle size, and the volume average particle size is measured using a laser diffraction / scattering particle size distribution analyzer. Specifically, the measurement is performed using, for example, a particle size distribution analyzer "Microtrac MT-3300II" (manufactured by Nikkiso Co., Ltd.). Unless otherwise specified, the average particle size of other particles is also measured using the same measurement method.

[0389] In embodiment 1, the in-plane density of particles having an average particle size of 0.5 to 20 μm is 10,000 particles / mm ２ The in-plane density is preferably 100 to 5000 particles / mm or less. ２ , and more preferably 100 to 3000 pieces / mm ２ is.

[0390] The in-plane density can be confirmed by observing the surface of the lithographic printing plate precursor with a scanning electron microscope (SEM). Specifically, the surface of the lithographic printing plate precursor is observed at five points with a scanning electron microscope (SEM) and the number of particles is counted. ２ The particle size can be calculated by converting the particle size into the number of particles per unit area and then calculating the average value.

[0391] The outermost layer on the side opposite to the image recording layer preferably contains a binder in addition to particles having an average particle size of 0.5 to 20 μm. Examples of the binder include novolak resins such as phenol formaldehyde resin, m-cresol formaldehyde resin, p-cresol formaldehyde resin, m- / p-mixed cresol formaldehyde resin, and phenol / cresol (m-, p-, or m- / p-mixed) mixed formaldehyde resin, resol resins, pyrogallol, acetone resin, epoxy resin, saturated copolymer polyester resin, phenoxy resin, polyvinyl acetal resin, vinylidene chloride copolymer resin, polybutene, polybutadiene, polyamide, and unsaturated copolymer polyester. It is preferable that the toner contains at least one resin selected from the group consisting of ester resin, polyurethane, polyurea, polyimide, polysiloxane, polycarbonate, epoxy resin, chlorinated polyethylene, aldehyde condensation resin of alkylphenol, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylate, carboxyvinyl polymer, acrylic resin copolymer resin, hydroxycellulose, hydroxymethylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, cellulose acetate, methylcellulose, and carboxymethylcellulose. A water-insoluble resin is preferable to prevent the risk of dissolution in fountain solution during on-press development.

[0392] The binder preferably contains at least one selected from the group consisting of polyurethane, acrylic resin, polystyrene, and polyethylene. In Aspect 1, the particles and the binder preferably each independently contain at least one selected from the group consisting of polyurethane, acrylic resin, polystyrene, and polyethylene.

[0393] The outermost layer on the side opposite to the side having the image recording layer may contain other components in addition to the particles and binder. Examples of other components include known additives such as surfactants.

[0394] The thickness of the outermost layer on the side opposite to the side having the image recording layer is preferably 0.5 to 10 μm, more preferably 0.5 to 5 μm, and even more preferably 0.5 to 3 μm.

[0395] Examples of the polymer compound constituting the plurality of protrusions containing the polymer compound as a main component in embodiment 2 include novolak resins such as phenol formaldehyde resin, m-cresol formaldehyde resin, p-cresol formaldehyde resin, m- / p-mixed cresol formaldehyde resin, and phenol / cresol (m-, p-, or m- / p-mixed) mixed formaldehyde resin, resol resin, pyrogallol acetone resin, epoxy resin, saturated copolymer polyester resin, phenoxy resin, polyvinyl acetal resin, vinylidene chloride copolymer resin, polybutene, and polybutadiene. At least one polymer compound selected from the group consisting of polyamide, unsaturated copolymer polyester resin, polyurethane, polyurea, polyimide, polysiloxane, polycarbonate, epoxy resin, chlorinated polyethylene, aldehyde condensation resin of alkylphenol, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylate, carboxyvinyl polymer, acrylic resin copolymer resin, hydroxycellulose, hydroxymethylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, cellulose acetate, methylcellulose, and carboxymethylcellulose is preferred.

[0396] Among these, water-soluble polymers are more preferred from the viewpoint of excellent developability even when the detached protrusions migrate to the image recording layer. Specific examples include polyacrylates, carboxyvinyl polymers, acrylic resin copolymer resins, hydroxycellulose, hydroxymethylcellulose, polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, cellulose acetate, methylcellulose, and carboxymethylcellulose. Acid-modified polyvinyl alcohols having carboxy groups or sulfo groups are preferably used as modified polyvinyl alcohols. Specifically, the modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137 are suitable.

[0397] The shape and height of the protrusions are not particularly limited, but the arithmetic mean height Sa is preferably 0.3 to 20 μm. The method for forming stripe-shaped protrusions (stripe coating film) is not particularly limited, but can be easily formed by applying a composition containing at least one selected from the group consisting of particles and polymer compounds using at least one method selected from the group consisting of bar coating, inkjet printing, gravure printing, screen printing, spray coating, and slot die coating. The method for forming dot-shaped protrusions (dot coating film) is not particularly limited, but can be easily formed by applying a composition containing at least one selected from the group consisting of particles and polymer compounds using at least one method selected from the group consisting of spray coating, inkjet printing, and screen printing. The method for forming dashed-line-shaped protrusions (dashed-line coating film) is not particularly limited, but can be easily formed by applying a composition containing at least one selected from the group consisting of particles and polymer compounds using at least one method selected from the group consisting of inkjet printing and screen printing.

[0398] Examples of the binder contained in the outermost layer in Aspect 2 include polymer compounds similar to those contained in the protrusions, and the same applies to preferred aspects. In Aspect 2, from the viewpoint of preventing detachment of the protrusions, it is preferable that the binder contained in the outermost layer and the polymer compound contained in the protrusions contain the same type of resin. Here, "the same type of resin" means that the resin type, such as polyurethane, acrylic resin, polystyrene, or polyethylene, is the same, and it is not necessary that all of the structural units in the resin are the same.

[0399] [Method for preparing a printing plate] The method for preparing a printing plate according to the present invention will be described using the lithographic printing plate precursor according to the present invention. The method for preparing a printing plate includes a step of imagewise exposing the lithographic printing plate precursor (exposure step), and a step of removing the unexposed area of ​​the image recording layer of the lithographic printing plate precursor after imagewise exposure on a printing press with at least one of printing ink and fountain solution (on-press development step).

[0400] [Exposure step] Imagewise exposure is preferably carried out by a method of scanning and exposing digital data with an infrared laser or the like. The wavelength of the exposure light source is preferably 750 to 1,400 nm. As a light source having a wavelength of 750 to 1,400 nm, a solid-state laser or semiconductor laser that emits infrared light is suitable. The exposure mechanism may be any of an internal drum system, an external drum system, a flatbed system, or the like. The exposure step can be carried out by a known method using a platesetter or the like. Alternatively, using a printing press equipped with an exposure device, the lithographic printing plate precursor may be mounted on the printing press and then imagewise exposure may be carried out on the printing press.

[0401] [On-press development process] In the on-press development process, printing ink and fountain solution are supplied to the lithographic printing plate precursor after image exposure on a printing press without any development treatment, and printing is started. The unexposed areas of the lithographic printing plate precursor are removed in the early stages of printing, thereby exposing the surface of the hydrophilic support and forming non-image areas. Known printing inks and fountain solution for lithographic printing are used as the printing ink and fountain solution. Either printing ink or fountain solution may be supplied first to the surface of the printing plate precursor, but it is preferable to supply printing ink first in order to prevent the fountain solution from being contaminated by the removed image-recording layer components. In this way, the lithographic printing plate precursor is developed on-press on an offset printing press and is used as is for printing a large number of sheets.

[0402] The method for producing a printing plate according to the present invention may include other known steps in addition to the steps described above, such as a plate inspection step for checking the position and orientation of the lithographic printing plate precursor before each step, and a confirmation step for checking the printed image after the on-press development step.

[0403] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, "%" and "parts" mean "% by mass" and "parts by mass", respectively, unless otherwise specified. In polymer compounds, unless otherwise specified, the molecular weight is the weight average molecular weight (Mw), and the ratio of the constituent repeating units is expressed as a molar percentage. The weight average molecular weight (Mw) is a value measured as a polystyrene equivalent value by gel permeation chromatography (GPC).

[0404] [Examples 1 to 67 and Comparative Examples 1 and 2]

[0405] <Preparation of Support 1> A 0.3 mm thick aluminum plate (aluminum alloy plate) of material 1S was subjected to the following treatments (Ja) to (Jm) to produce Support 1. Note that a water rinsing treatment was performed between all treatment steps, and after the water rinsing treatment, the liquid was removed using nip rollers.

[0406] (Ja) Mechanical roughening treatment (brush graining method) Using an apparatus such as that shown in FIG. 5, a suspension of pumice (specific gravity 1.1 g / cm ３ ) was supplied to the surface of the aluminum plate as an abrasive slurry, while a mechanical roughening treatment was performed using a rotating bundled brush. In Figure 5, 31 is an aluminum plate, 32 and 34 are roller-shaped brushes (bundled brushes in this example), 33 is an abrasive slurry, and 35, 36, 37, and 38 are support rollers. In the mechanical roughening treatment, the median diameter (μm) of the abrasive was 30 μm, the number of brushes was 4, and the brush rotation speed (rpm) was 250 rpm. The bundled brush was made of 6-10 nylon, with a bristle diameter of 0.3 mm and a bristle length of 50 mm. The brush was densely packed in a φ300 mm stainless steel cylinder with holes drilled into it. The distance between the two support rollers (φ200 mm) below the bundled brush was 300 mm. The bundled brush was pressed down until the load of the drive motor rotating the brush was 10 kW higher than the load before pressing the bundled brush against the aluminum plate. The direction of rotation of the brush was the same as the direction of movement of the aluminum plate.

[0407] (J-b) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 10 g / m. ２ It was.

[0408] (J-c) Desmutting Treatment Using Acidic Aqueous Solution Desmutting treatment was performed by spraying the nitric acid waste solution used in the subsequent electrochemical graining treatment at a liquid temperature of 35°C onto the aluminum plate for 3 seconds as the acidic aqueous solution.

[0409] (J-d) Electrochemical graining treatment using aqueous nitric acid solution Continuous electrochemical graining treatment was performed using a 60 Hz AC voltage. The electrolyte used was an aqueous solution of nitric acid 10.4 g / L to which aluminum nitrate was added to adjust the aluminum ion concentration to 4.5 g / L, and the electrolyte temperature was 35°C. The AC power source waveform was the waveform shown in Figure 1, and the time tp until the current value reached its peak from zero was 0.8 msec, the duty ratio was 1:1, and a trapezoidal square wave AC was used. Electrochemical graining treatment was performed using a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode. The electrolytic cell shown in Figure 2 was used. The current density was 30 A / dm at the peak current value. ２ 5% of the current flowing from the power supply was diverted to the auxiliary anode. ２ ) is the total amount of electricity when the aluminum plate is the anode, 185 C / dm ２ It was.

[0410] (Je) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 27% by mass of caustic soda and 2.5% by mass of aluminum ions onto the aluminum plate at a temperature of 50°C. The amount of dissolved aluminum was 3.5 g / m ２ It was.

[0411] (J-f) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L and a liquid temperature of 30°C was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0412] (J-g) Electrochemical graining treatment using a hydrochloric acid solution Continuous electrochemical graining treatment was performed using a 60 Hz AC voltage. The electrolyte used was an aqueous solution of 6.2 g / L hydrochloric acid with aluminum chloride added to adjust the aluminum ion concentration to 4.5 g / L, and the electrolyte temperature was 35°C. The AC power source waveform was the waveform shown in Figure 1, and the time tp until the current value reached its peak from zero was 0.8 msec, the duty ratio was 1:1, and a trapezoidal square wave AC was used. Electrochemical graining treatment was performed using a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode. The electrolytic cell shown in Figure 2 was used. The current density was 25 A / dm at the peak current value. ２ and the quantity of electricity in hydrochloric acid electrolysis (C / dm ２ ) is the total amount of electricity when the aluminum plate is the anode, 63 C / dm ２ It was.

[0413] (J-h) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions onto the aluminum plate at a temperature of 60°C. The amount of dissolved aluminum was 0.2 g / m ２ It was.

[0414] (J-i) Desmutting Treatment Using Acidic Aqueous Solution An aqueous solution of waste liquid (sulfuric acid concentration 170 g / L and aluminum ion concentration 5 g / L) generated in the anodizing treatment step at a liquid temperature of 35°C was sprayed onto the aluminum plate for 4 seconds to perform desmutting treatment.

[0415] (J-j) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in FIG. 6. A 170 g / L aqueous sulfuric acid solution was used as the electrolytic solution, and the solution temperature was 50°C and the current density was 30 A / dm ２ Anodizing treatment was carried out under the conditions of ２ An anodic oxide film was formed.

[0416] (Jk) Pore Widening Treatment The anodized aluminum plate was immersed in an aqueous solution of caustic soda with a caustic soda concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass at 40° C. for 3 seconds to perform a pore widening treatment.

[0417] (J-l) Second-stage anodizing treatment: The second-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 6. A 170 g / L aqueous sulfuric acid solution was used as the electrolyte, and the solution temperature was 50°C and the current density was 13 A / dm ２ Anodizing treatment was carried out under the conditions of ２ An anodic oxide film was formed.

[0418] (J-m) Hydrophilization Treatment To ensure hydrophilicity in non-image areas, the aluminum plate was subjected to silicate treatment by immersing it in a 2.5% by mass aqueous solution of No. 3 sodium silicate at 50°C for 7 seconds. The amount of Si attached was 8.5 mg / m ２ The average diameter of the micropores was 30 nm. The lightness L* value of the anodized film surface of Support 1 in the L*a*b* color system was 72.3.

[0419] <Preparation of Support 2> A 0.3 mm thick aluminum plate (aluminum alloy plate) made of material 1S was subjected to the following treatments (F-a) to (F-g) to prepare Support 2. Note that a water rinsing treatment was performed between all treatment steps, and after each water rinsing treatment, the liquid was removed using nip rollers.

[0420] (F-a) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m. ２ It was.

[0421] (Fb) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 150 g / L and a liquid temperature of 30° C. was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0422] (F-c) Electrochemical Graining Treatment Electrochemical graining treatment was carried out using an electrolytic solution with a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L, and an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The waveform of the alternating current was a sine wave with symmetrical positive and negative waveforms, the frequency was 50 Hz, the anode reaction time and cathode reaction time in one cycle of the alternating current were 1:1, and the current density was 75 A / dm at the peak current value of the alternating current waveform. ２ The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm ２ and the electrolysis temperature is 112.5 C / dm ２ The test was carried out four times with a 4-second interval between each test. A carbon electrode was used as the counter electrode to the aluminum plate.

[0423] (F-d) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions onto the aluminum plate at a temperature of 45°C. The amount of dissolved aluminum on the electrochemically roughened surface was 0.2 g / m. ２ It was.

[0424] (Fe) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L and a liquid temperature of 35°C was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0425] (F-f) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 6. A 150 g / L aqueous phosphoric acid solution was used as the electrolyte, and the solution temperature was 35°C and the current density was 4.5 A / dm ２ Anodizing treatment was carried out under the conditions of ２An anodized film of the formula (I) was formed on the aluminum plate 416. In the anodizing treatment apparatus 410 shown in FIG. 6, the aluminum plate 416 is transported as indicated by the arrow in FIG. 6. In a power supply tank 412 containing an electrolytic solution 418, the aluminum plate 416 is positively charged by a power supply electrode 420. The aluminum plate 416 is then transported upward in the power supply tank 412 by a roller 422, redirected downward by a nip roller 424, transported toward an electrolytic treatment tank 414 containing an electrolytic solution 426, and redirected horizontally by a roller 428. The aluminum plate 416 is then negatively charged by an electrolytic electrode 430, thereby forming an anodized film on the surface of the aluminum plate 416. The aluminum plate 416 leaves the electrolytic treatment tank 414 and is transported to a subsequent process. In the anodizing treatment device 410, a direction changing means is formed by the roller 422, the nip roller 424, and the roller 428, and the aluminum plate 416 is transported in a mountain shape and an inverted U shape by the rollers 422, 424, and 428 in the space between the power supply tank 412 and the electrolytic treatment tank 414. The power supply electrode 420 and the electrolytic electrode 430 are connected to a DC power supply 434.

[0426] (F-g) Second-stage anodizing treatment: The second-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in FIG. 6. A 170 g / L aqueous sulfuric acid solution was used as the electrolyte, and the solution temperature was 50°C and the current density was 13 A / dm ２ Anodizing treatment was carried out under the conditions of ２ An anodized film of 1000 nm was formed on the support 2. The support 2 was then washed with water by spraying. The average diameter of the micropores in the support 2 was 40 nm. The lightness L* value of the anodized film surface of the support 2 in the L*a*b* color system was 83.7.

[0427] <Preparation of Support 3> A 0.3 mm thick aluminum plate (aluminum alloy plate) made of material 1S was subjected to the following treatments (F-a) to (F-f) to prepare Support 3. Note that a water rinsing treatment was performed between all treatment steps, and after each water rinsing treatment, the liquid was removed using nip rollers.

[0428] (F-a) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 26% by mass of caustic soda and 6.5% by mass of aluminum ions onto the aluminum plate at a temperature of 70°C. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m. ２ It was.

[0429] (Fb) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 150 g / L and a liquid temperature of 30° C. was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0430] (F-c) Electrochemical Graining Treatment Electrochemical graining treatment was carried out using an electrolytic solution with a hydrochloric acid concentration of 14 g / L, an aluminum ion concentration of 13 g / L, and a sulfuric acid concentration of 3 g / L, and an alternating current. The temperature of the electrolytic solution was 30°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The waveform of the alternating current was a sine wave with symmetrical positive and negative waveforms, the frequency was 50 Hz, the anode reaction time and cathode reaction time in one cycle of the alternating current were 1:1, and the current density was 75 A / dm at the peak current value of the alternating current waveform. ２ The total amount of electricity that the aluminum plate takes in the anode reaction is 450 C / dm ２ and the electrolysis temperature is 112.5 C / dm ２ The test was carried out four times with a 4-second interval between each test. A carbon electrode was used as the counter electrode to the aluminum plate.

[0431] (F-d) Alkali Etching Treatment An aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions onto the aluminum plate at a temperature of 45°C. The amount of dissolved aluminum on the electrochemically roughened surface was 0.2 g / m. ２ It was.

[0432] (Fe) Desmutting Treatment Using Acidic Aqueous Solution An acidic aqueous solution having a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L and a liquid temperature of 35°C was sprayed onto the aluminum plate for 3 seconds to perform desmutting treatment.

[0433] (F-f) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 6. A 150 g / L aqueous phosphoric acid solution was used as the electrolyte, and the solution temperature was 35°C and the current density was 4.5 A / dm ２ Anodizing treatment was carried out under the conditions of ２ The average diameter of the micropores in Support 3 was 40 nm. The lightness L* value of the surface of the anodized coating on Support 3 in the L*a*b* color system was 82.4.

[0434] <Preparation of Support 4> Support 4 was prepared according to the support manufacturing method of Example 5 of WO 2021 / 67054.

[0435] <Formation of Undercoat Layer 1> An undercoat layer coating solution (1) having the following composition was applied to a support in a dry coating amount of 26 mg / m ２ The undercoat layer 1 was formed by coating the mixture in such a manner that the thickness of the undercoat layer 1 becomes 1 / 2 mm.

[0436] (Undercoat layer coating solution (1)) Undercoat layer compound (2) (structure shown below) 0.013 parts Hydroxyethyliminodiacetic acid 0.005 parts Ethylenediaminetetraacetic acid tetrasodium 0.005 parts Polyoxyethylene lauryl ether 0.0003 parts Water 3.15 parts

[0437]

[0438] The numerical value in the parentheses to the right of each structural unit in the compound (2) for undercoat layer indicates the mass ratio, and the numerical value in the parentheses to the right of the ethyleneoxy unit indicates the number of repetitions.

[0439] <Formation of Undercoat Layer 2> An undercoat layer coating solution (2) having the following composition was applied onto a support in a dry coating amount of 0.03 g / m ２ The undercoat layer 2 was formed by coating the mixture so that the thickness became

[0440] (Undercoat layer coating solution (2)) Polyacrylic acid aqueous solution (40% by mass) Jurymer AC-10S (manufactured by Toagosei Co., Ltd.) 3.0 parts Water 27.0 parts

[0441] <Formation of Image Recording Layers 1 to 58, 61 to 62, 63 to 69> Each image recording layer coating liquid (image recording layer coating liquids (1) to (58), (61) to (62), (63) to (69)) having the following composition was applied with a bar, and then dried in an oven at 110°C for 40 seconds to form a layer with a dry weight of 1.0 g / m ２ The image recording layers 1 to 58, 61 to 62, and 63 to 69 were formed, respectively. The amounts of the compounds listed in Table 1 were selected so that the dry weights would be the contents listed.

[0442] (Image recording layer coating liquid) 2-butanone: 5.3155 parts 1-methoxy-2-propanol: 2.8825 parts Methanol: 2.3391 parts Color-forming compound (listed in Table 1): Amount listed in Table 1 Hydrogen-donating compound (listed in Table 1): Amount listed in Table 1 Polymerizable compound (listed in Table 1): Amount listed in Table 1 Electron-accepting polymerization initiator (listed in Table 1): Amount listed in Table 1 Electron-donating polymerization initiator (listed in Table 1): Amount listed in Table 1 Infrared absorber (listed in Table 1): Amount listed in Table 1 Acid color former (listed in Table 1): Amount listed in Table 1 Tricresyl phosphate: 0.0125 parts Anionic surfactant (A-1): 0.0162 parts Microgel liquid: 2.8779 parts Fluorine-based surfactant (W-1): 0.0042 parts

[0443]

[0444] The method for preparing the microgel used in the above microgel solution is as follows.

[0445] - Preparation of Polyisocyanate Compound - 0.043 parts of bismuth tris(2-ethylhexanoate) (Neostane U-600, manufactured by Nitto Kasei Co., Ltd.) was added and stirred to a suspension of 17.78 parts (80 molar equivalents) of isophorone diisocyanate and 7.35 parts (20 molar equivalents) of a polyhydric phenol compound (1) represented by the following structural formula in 25.31 parts of ethyl acetate. 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 polyisocyanate compound (1).

[0446]

[0447] - Preparation of Microgel - The oil phase components and aqueous phase components listed below were mixed and emulsified using a homogenizer at 12,000 rpm for 10 minutes. The resulting emulsion was stirred at 45°C for 4 hours, after which 5.20 g of a 10% aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene-octylate (U-CAT SA102, manufactured by San-Apro Co., Ltd.) was added, stirred at room temperature for 30 minutes, and allowed to stand at 45°C for 24 hours. The solids concentration was adjusted to 20% by mass with distilled water, yielding an aqueous dispersion of microgel. The average particle size was measured by light scattering and found to be 0.28 μm.

[0448] Oil Phase Components (Component 1) Ethyl acetate: 12.0 parts (Component 2) An adduct obtained by adding trimethylolpropane (6 molar equivalents) and xylene diisocyanate (18 molar equivalents) to one-terminally methylated polyoxyethylene (1 molar equivalent, number of repeating oxyethylene units: 90) (50% by mass ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.): 3.76 parts (Component 3) Polyvalent isocyanate compound (1) (as a 50% by mass ethyl acetate solution): 15.0 parts (Component 4) 65% by mass ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer Co., Ltd.): 11.54 parts (Component 5) 10% ethyl acetate solution of sulfonate-type surfactant (Paionin A-41-C, manufactured by Takemoto Oil & Fat Co., Ltd.): 4.42 parts

[0449] ~Aqueous phase components~ Distilled water: 46.87 parts

[0450] <Formation of Image Recording Layers 59 to 60> Each image recording layer coating solution (image recording layer coating solutions (59) to (60)) having the following composition was applied with a bar, and then dried in an oven at 110°C for 40 seconds to form a layer having a dry weight of 0.9 g / m ２ Image recording layers 59 to 60 were formed, respectively. The amounts of the compounds listed in Table 1 were selected so that the dry weights would be the contents listed. (Image recording layer coating liquid) 1-propanol 4.94 parts 2-butanone 2.40 parts γ-butyl lactone 0.14 parts 1-methoxy-2-propanol 4.22 parts Water 0.66 parts Polymer dispersion ＊１ 1.056 parts Hydroxypropyl methylcellulose ＊２ 0.600 copies ・BYK 302 ＊３ 0.18 parts Color-forming compound (described in Table 1): Amount described in Table 1 Hydrogen-donor compound (described in Table 1): Amount described in Table 1 Polymerizable compound (described in Table 1): As described in the Examples table Electron-accepting polymerization initiator (described in Table 1): Amount described in Table 1 Electron-donating polymerization initiator (described in Table 1): Amount described in Table 1 Infrared absorber (described in Table 1): Amount described in Table 1 Acid color former (described in Table 1): Amount described in Table 1 *1: The polymer dispersion was prepared according to the description of EP 1765593 A1, and used as a 23.5% by mass dispersion in n-propanol / water (80:20 [mass ratio]). *2: 5.0% by mass aqueous solution *3: 25% by mass concentration 1-methoxy-2-propanol solution (manufactured by BYK Chemie)

[0451] [Color-forming compounds] The color-forming compounds shown in Table 1 are as described above. [Hydrogen-donating compounds] The hydrogen-donating compounds shown in Table 1 are as described above.

[0452] [Polymerizable Compounds] The polymerizable compounds listed in Table 1 are described below. 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. To the reaction solution, Neostan U-600 (bismuth-based polycondensation catalyst, manufactured by Nitto Kasei Co., Ltd., 0.11 parts) was added, and the mixture was heated at 65°C for 4 hours. The reaction solution was cooled to room temperature (25°C), and methyl ethyl ketone was added to synthesize a urethane acrylate (M-2) 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 14,000. M-2: A polymerizable compound in a 2-butanone solution at a concentration of 80% by mass, obtained by reacting DESMODUR (registered trademark) N100 with hydroxyethyl acrylate and pentatritol acrylate in a molar ratio of 1:1.5:1.5. M-3: Dipentaerythritol hexaacrylate (DPHA) M-4: Ethoxylated (4) pentaerythritol tetraacrylate "Sartmer SR494"

[0453] [Electron-donating polymerization initiator] The electron-donating polymerization initiators shown in Table 1 are described below.

[0454]

[0455] [Electron-Accepting Polymerization Initiator] The electron-accepting polymerization initiators shown in Table 1 are described below.

[0456]

[0457] [Infrared absorbing agent] The infrared absorbing agents shown in Table 1 are described below. These are compounds different from the color-forming compounds.

[0458]

[0459] [Acid Color Former] The acid color formers shown in Table 1 are described below. They are compounds different from the color-forming compounds.

[0460]

[0461]

[0462] <Formation of Protective Layers 1 to 5> Each protective layer coating solution (protective layer coating solutions (1) to (5)) having the following composition was applied onto the image recording layer with a bar, and then dried in an oven at 120°C for 60 seconds to a dry coating amount of 0.1 g / m ２ A protective layer of

[0463] (Protective layer coating liquid) Inorganic layer compound dispersion (1) (below): Amount described in Table 1 Hydrophilic polymer (1) (structure below, Mw: 30,000): 0.03 parts Metrose SM04 (manufactured by Shin-Etsu Chemical Co., Ltd.): 0.0600 parts Rapisol A-80 (80% aqueous solution) (manufactured by NOF Corporation): 0.0063 parts Water: 2.0 parts

[0464]

[0465] (Preparation of Inorganic Layered Compound Dispersion Liquid (1)) 6.4 parts of synthetic mica Somasif ME-100 (manufactured by Co-op Chemical Co., Ltd.) was added to 193.6 parts of ion-exchanged water, and the mixture was dispersed using a homogenizer until the volume average particle diameter (laser scattering method) reached 3 μm. The aspect ratio of the resulting dispersed particles was 100 or more.

[0466] In the protective layer shown in Table 1, "layer compound" refers to "synthetic mica Somasif ME-100 (manufactured by Co-op Chemical Co., Ltd.)," a component of inorganic layer compound dispersion (1). The content of "inorganic layer compound dispersion (1)" was selected so that the "content" in Table 1 corresponds to the dry weight of the content shown.

[0467] [Preparation of lithographic printing plate precursors] The above supports, undercoat layers, image recording layers, and protective layers were combined as shown in Table 1 to prepare lithographic printing plate precursors of Examples 1 to 74 and Comparative Examples 1 and 2.

[0468]

[0469]

[0470]

[0471]

[0472]

[0473]

[0474] The resulting lithographic printing plate precursor was evaluated as follows.

[0475] <Visibility evaluation: immediately after exposure> The obtained lithographic printing plate precursor was exposed to 110 mJ / cm 2 using a Luxel PLATESETTER T-6000III (manufactured by Fujifilm Corporation) equipped with an infrared semiconductor laser with a wavelength of 830 nm. ２ The exposed image included a solid image and a non-image area. The exposure was carried out in an environment of 25°C and 50% RH. The color development of the lithographic printing plate precursor immediately after exposure was measured. The measurement was carried out using a spectrophotometer CM2600d manufactured by Konica Minolta Inc. and operation software CM-S100W, using the SCE (specularly reflected light excluded) method. The color development was evaluated using the L* value (lightness) of the L*a*b* color system, and the difference ΔL between the L* value of the exposed area and the L* value of the unexposed area. It can be said that the larger the ΔL value, the better the color development.

[0476] <Evaluation of visibility: after storage in a dark place> The obtained lithographic printing plate precursor was subjected to 110 mJ / cm irradiance using a Luxel PLATESETTER T-6000III (manufactured by Fujifilm Corporation) equipped with an infrared semiconductor laser with a wavelength of 830 nm. ２The exposed image included both solid and non-image areas. The exposure was performed in an environment of 25°C and 50% RH. The lithographic printing plate precursor immediately after exposure was stored in a dark environment at 25°C and 50% RH for 72 hours, after which the color development was measured. During storage, the lithographic printing plate precursor was stacked on top of another to prevent the exposed surface from coming into contact with air. Measurements were performed using a spectrophotometer CM2600d manufactured by Konica Minolta, Inc. and operation software CM-S100W, using the SCE (specularly reflected light excluded) method. Color development was evaluated using the L* value (lightness) of the L*a*b* color system, and the difference ΔL between the L* value of the exposed area and the L* value of the unexposed area. The larger the ΔL value, the better the color development. ΔL of 3.5 or more was considered acceptable.

[0477] <Visibility evaluation: after exposure to white light> The obtained lithographic printing plate precursor was subjected to 110 mJ / cm irradiance using a Luxel PLATESETTER T-6000III (manufactured by Fujifilm Corporation) equipped with an infrared semiconductor laser with a wavelength of 830 nm. ２ The exposed image included both solid and non-image areas. The exposure was performed in an environment of 25°C and 50% RH. The lithographic printing plate precursor immediately after exposure was conditioned for 1 hour in a dark environment at 25°C and 30% RH, and then exposed to white fluorescent light for 1 hour so that the illuminance on the plate surface was 800 lux. The environment of 25°C and 30% RH was maintained even during exposure to white light. The color development of the lithographic printing plate precursor after exposure to white light was measured. Measurements were performed using a spectrophotometer CM2600d manufactured by Konica Minolta, Inc. and operation software CM-S100W using the SCE (specularly reflected light excluded) method. Color development was evaluated using the L* value (lightness) of the L*a*b* color system, and the difference ΔL between the L* value of the exposed area and the L* value of the unexposed area. A larger ΔL value indicates better color development. If ΔL is 3.5 or more, it is considered to be within the acceptable range.

[0478] The results obtained are shown in Table 1.

[0479] The resulting lithographic printing plate precursors were further evaluated for "printing durability" and "fountain solution contamination" as follows. Furthermore, the lithographic printing plate precursors obtained in Examples 1, 2, 8, 10-11, 38-40, 45, 55-57, and 65-73 were further evaluated for "sensor readability" as follows.

[0480] <Evaluation of printing durability> The obtained lithographic printing plate precursor was exposed (irradiation energy equivalent to 110 mJ / cm2) using a Kodak Magnus 800 Quantum equipped with an infrared semiconductor laser under the conditions of an output of 27 W, an outer drum rotation speed of 450 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch = 2.54 cm). The exposed image included a solid image and a 10% AM screen (Amplitude Modulation Screen) chart. The obtained exposed plate precursor was mounted on the cylinder of a Heidelberg SX-74 printing press (Kikuban size) without development. A 100 L capacity dampening water circulating tank equipped with a nonwoven fabric filter and a temperature control device was connected to this printing press. Eighty liters of 3.5% dampening solution S-Z1 (manufactured by Fujifilm Corporation) was charged into the circulation device, and UV CORE TYPE-A J Sumi GE M (manufactured by T&K Toka Corporation) was used as the printing ink. After supplying the dampening solution and ink using the standard automatic printing start method, 1,000 sheets were printed on Shiraoi paper (ream weight 48.5 kg, manufactured by Nippon Paper Industries Co., Ltd.) at a printing speed of 10,000 sheets per hour. Further printing was then performed. As the number of prints increased, the image area gradually wore away, resulting in a decrease in ink density on the prints. Printing durability was evaluated by determining the number of prints completed when the dot area ratio of the 10% AM screen dots on the prints, measured using an eXact spectrophotometer (manufactured by X-lite Corporation), fell 3% from the value measured on the 1,000th print. The relative printing durability was evaluated according to the following criteria, with 50,000 printed sheets being set at 100. The higher the value, the better the printing durability. Relative printing durability = (number of printed sheets of target lithographic printing plate precursor / 50,000) x 100 - Evaluation criteria - 6: The relative printing durability value exceeds 110. 5: The relative printing durability value is greater than 100 and not more than 110. 4: The relative printing durability value is greater than 90 and not more than 100. 3: The relative printing durability value is greater than 80 and not more than 90. 2: The relative printing durability value is greater than 70 and not more than 80. 1: The relative printing durability value is not more than 70.

[0481] <Evaluation of Fountain Solution Contamination> After adjusting the water-ink balance properly using an adjustment plate (XP-F manufactured by Fujifilm Corporation), 1,000 sheets were printed. After that, the adjustment plate was removed and the blanket was washed. Next, the ink fountain key was set to zero. The dampening water used during adjustment was discarded and new dampening water was added. At this time, the dampening water circulation system was stopped and the outlet was closed with a rubber stopper. Next, the following operations X1 to X3 were repeated 10 times. X1: The prepared lithographic printing plate precursor (unexposed plate) was dampened 50 times by manual pre-damping. X2: After dampening 50 times, 100 sheets were printed on Shiraoi (high-quality paper, manufactured by Nippon Paper Industries Co., Ltd.). X3: The plate was removed. The printing conditions are also shown below. Printing machine: Lithrone printing machine LS26 / 104 manufactured by Komori Corporation Ink: UV ink (UV CORE TYPE-AJ yellow manufactured by T&K TOKA Corporation) Dampening water: PRESSMAX S-Z1 2% (manufactured by FUJIFILM Corporation) Pre-dampening: 50 times Thereafter, the rubber stopper was removed, the dampening water was collected, and the turbidity was determined by the transparency of the dampening water. The transparency was measured in accordance with JIS K0102 (2019) and evaluated according to the following criteria. - Evaluation criteria - 5: Transparency 8 cm or more 4: Transparency 6 cm or more and less than 8 cm 3: Transparency 4 cm or more and less than 6 cm 2: Transparency 2 cm or more and less than 4 cm 1: Transparency 0 cm or more and less than 2 cm

[0482] <Sensor readability> The obtained lithographic printing plate precursor was exposed (irradiation energy equivalent to 110 mJ / cm2) using a Trendsetter Q800 manufactured by Eastman Kodak Company equipped with an infrared semiconductor laser under the conditions of an output of 14 W, an outer drum rotation speed of 360 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch is 2.54 cm). The exposed image included a data matrix code. The data matrix code (9 mm square size) was read using an SR-1000W sensor manufactured by Keyence Corporation, and the following evaluation was performed based on the matching level (an index representing readability). - Evaluation criteria - A: Matching level of 70% or more B: Matching level of 50% or more but less than 70% C: Matching level of 30% or more but less than 50% D: Matching level less than 30, or unreadable.

[0483] The results obtained are shown in Table 1.

[0484]

[0046] From the results shown in Table 1, the on-press developable lithographic printing plate precursor according to the present invention exhibits good visibility in the exposed areas immediately after exposure, is easily able to maintain good visibility immediately after exposure, and maintains good visibility even after storage under white light. Comparative Example 1 is an embodiment in which the image recording layer of the lithographic printing plate precursor does not contain a color-forming compound but contains an infrared absorber. Comparative Example 1 shows that the visibility in the exposed areas is good immediately after exposure and remains good even after storage under white light, but the good visibility immediately after exposure cannot be maintained and deteriorates. Comparative Example 2 is an embodiment in which the image recording layer of the lithographic printing plate precursor contains a color-forming compound but does not contain a hydrogen-donor compound. Comparative Example 2 shows that the visibility in the exposed areas is good immediately after exposure and can maintain good visibility immediately after exposure, but deteriorates even after storage under white light. It is also clear that the on-press developable lithographic printing plate precursor of the present invention has good printing durability, good color development, and can suppress contamination by dampening water.It is also clear that the on-press developable lithographic printing plate precursor of the present invention has good sensor readability.

[0485] According to the present invention, it is possible to provide an on-press development type lithographic printing plate precursor that has good visibility in the exposed area immediately after exposure, that is likely to maintain good visibility immediately after exposure, and that has good visibility in the exposed area even after storage under white light, and a method for producing a printing plate using the on-press development type lithographic printing plate precursor.

[0486] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on Japanese patent applications filed on August 31, 2023 (Patent Application No. 2023-141847) and February 29, 2024 (Patent Application No. 2024-030807), the contents of which are incorporated herein by reference.

[0487] REFERENCE SIGNS LIST 1 planographic printing plate precursor 1a image recording layer surface 1b support surface 1c edge surface 2 sag 10 cutting blade 10a upper cutting blade 10b upper cutting blade 11 rotating shaft 20 cutting blade 20a lower cutting blade 20b lower cutting blade 21 rotating shaft 30 planographic printing plate precursor 31 aluminum plate 32, 34 roller-shaped brush 33 polishing slurry liquid 35, 36, 37, 38 support roller 50 main electrolytic cell 51 AC power source 52 radial drum roller 53a, 53b main electrode 54 electrolyte supply port 55 electrolyte 56 slit 57 electrolyte passage 58 auxiliary anode 60 auxiliary anode cell 410 anodizing treatment device 412 power supply cell 414 Electrolytic treatment tank 416: Aluminum plate 418, 426: Electrolyte 420: Power supply electrode 422, 428: Roller 424: Nip roller 430: Electrolysis electrode 432: Tank wall 434: DC power source B: Boundary between image recording layer surface and support W: Aluminum plate X: Amount of sagging Y: Width of sagging

Claims

1. An on-press development type lithographic printing plate precursor having an image recording layer on a support, the image recording layer containing a color-forming compound having a group that is cleaved by infrared exposure, a polymerization initiator, a polymerizable compound, and a hydrogen-donating compound, the hydrogen-donating compound being a compound different from the polymerization initiator, the polymerizable compound, the color-forming compound, and the acid-cleavable compound, and containing -OH, -NH-, -SO ２ -NH-, -SO ２ An on-press development type lithographic printing plate precursor, which is a compound having at least one group selected from the group consisting of --OH, --CO--NH--, and --CO--OH in the molecule and having a molecular weight of less than 3,000.

2. The on-press development type lithographic printing plate precursor according to claim 1, wherein the hydrogen donor compound is a compound having at least one partial structure represented by the following formula (I) in the molecule: In formula (I), X is -OH, -NH-, -SO ２ -NH-, -SO ２ R is a hydrogen donating group selected from the group consisting of -OH, -CO-NH-, and -CO-OH. １Ａ ~R ３Ａ R is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a hetero atom. １Ａ ~R ３Ａ At least two of may be linked to form a ring. When X is a monovalent group, R １Ａ ~R ３Ａ One or more hydrogen atoms contained in the group are removed to form bonds. When X is a divalent group, R １Ａ ~R ３Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

3. The on-press development type lithographic printing plate precursor according to claim 1, wherein the hydrogen donor compound is a compound having at least one partial structure represented by the following formula (II) in the molecule: In formula (II), Ar represents an aromatic ring group, and X represents -OH, -NH-, or -SO. ２ -NH-, -SO ２ R is a group selected from the group consisting of -OH, -CO-NH-, and -CO-OH. ４Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a hetero atom. m represents an integer of 1 to 5. When m represents an integer of 2 or more, multiple Xs may be the same or different. n represents an integer of 0 to 5. When n represents an integer of 2 or more, multiple R ４Ａ may be the same or different. When n is 2 or more, a plurality of R ４Ａ may be linked to form a ring. When all X's are monovalent groups, R ４Ａ When at least one X is a divalent group, R ４Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

4. The on-press development type lithographic printing plate precursor according to claim 1, wherein the hydrogen donor compound is a compound having at least one partial structure represented by the following formula (III) in the molecule: In formula (III), X is -OH, -NH-, -SO ２ -NH-, -SO ２ R is a group selected from the group consisting of -OH, -CO-NH-, and -CO-OH. ５Ａ is a group having at least one selected from the group consisting of a hydrogen atom, a carbon atom, a halogen atom, and a hetero atom. p represents an integer of 1 to 5. When p represents an integer of 2 or more, multiple Xs may be the same or different. q represents an integer of 0 to 5. When q represents an integer of 2 or more, multiple R ５ may be the same or different. When q is 2 or more, a plurality of R ５Ａ may be linked to form a ring. p+q is 6 or less. When all X's are monovalent groups, R ５Ａ When at least one X is a divalent group, R ５Ａ One or more hydrogen atoms contained in may be further removed to form bonds.

5. The hydrogen donor compound is -OH, -NH-, -SO ２ -NH-, -SO ２ The on-press development type lithographic printing plate precursor according to claim 1, which is a compound having at least two groups selected from the group consisting of -OH, -CO-NH-, and -CO-OH in the molecule.

6. The hydrogen donor compound is —OH and —SO ２ The on-press development type lithographic printing plate precursor according to claim 1, which has at least one group selected from the group consisting of -NH-.

7. The hydrogen donor compound is —OH and —SO ２ The on-press development type lithographic printing plate precursor according to claim 1, which has at least two groups selected from the group consisting of -NH-.

8. The on-press development type lithographic printing plate precursor according to claim 1, wherein the hydrogen donor compound has at least one phenolic hydroxyl group.

9. The on-press development type lithographic printing plate precursor according to claim 1, wherein the hydrogen donor compound has two or more phenolic hydroxyl groups.

10. The on-press development type lithographic printing plate precursor according to claim 1, wherein the chromogenic compound having a group that is cleaved by exposure to infrared light is a cyanine dye represented by formula 1: In formula 1, R １ is exposed to infrared light １ represents a group in which the -L bond is cleaved, and R １１ ~R １８ each independently represents a hydrogen atom, a halogen atom, -Ra, -ORb, -SRc, or -NRdRe, each independently represents a hydrocarbon group, A １ , A ２ and multiple R １１ ~R １８ may be linked to form a monocyclic or polycyclic ring, A １ and A ２ each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom; １１ and n １２ Each independently represents an integer of 0 to 5, provided that １１ and n １２ The sum of n is 2 or more, １３ and n １４ each independently represents 0 or 1, and L represents an oxygen atom, a sulfur atom, or -NR １０ - represents R １０ represents a hydrogen atom, an alkyl group or an aryl group, and Za represents a counter ion that neutralizes the charge.

11. The on-press development type lithographic printing plate precursor according to claim 10, wherein the color-forming compound having a group that is cleaved by exposure to infrared light is a compound represented by formula 2: In formula 2, R １ is exposed to infrared light １ represents a group in which the -L bond is cleaved, and R ２ and R ３ each independently represents a hydrogen atom or an alkyl group; R ２ and R ３ may be linked together to form a ring, Ar １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring; Y １ and Y ２ each independently represents an oxygen atom, a sulfur atom, or -NR ０ - or a dialkylmethylene group; R ０ represents a hydrogen atom, an alkyl group or an aryl group; R ４ and R ５ each independently represents an aliphatic hydrocarbon group, -CO ２ M group or -PO ３ M ２ group, M represents a hydrogen atom, a Na atom, a K atom or an onium group, R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group; 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.

12. The on-press development type lithographic printing plate precursor according to claim 11, wherein L in formula 2 represents an oxygen atom.

13. R in the above formula 2 １ The on-press development type lithographic printing plate precursor according to claim 12, wherein is a group represented by the following formula (5): In formula (5), R １５ and R １６ each independently represents a hydrogen atom, an alkyl group or an aryl group; E represents an onium group; * represents a bonding site with the oxygen atom represented by L in formula 2; 14. The on-press development type lithographic printing plate precursor according to claim 1, wherein the polymerizable compound contains a polymerizable compound having 11 or more functionalities.

15. The on-press development type lithographic printing plate precursor according to claim 1, wherein the polymerization initiator contains a borate compound as an electron-donating polymerization initiator.

16. The on-press development type lithographic printing plate precursor according to claim 1, wherein the polymerization initiator comprises an onium salt compound as an electron-accepting polymerization initiator.

17. The on-press development type lithographic printing plate precursor according to claim 1, wherein said image recording layer contains an acid color former in addition to said color-forming compound having a group that is cleaved by exposure to infrared light.

18. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 17, which has a protective layer on the image recording layer.

19. The on-press development type lithographic printing plate precursor according to claim 18, wherein the protective layer comprises an inorganic layer compound.

20. The content of the inorganic layered compound is 5 to 80 mg / m ２ The on-press development type lithographic printing plate precursor according to claim 19, 21. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 17, wherein the micropores in the anodized film of the support are composed of large-diameter pores extending from the surface of the anodized film to a depth of 10 nm to 1,000 nm and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend from the communicating positions to a depth of 20 nm to 2,000 nm, the large-diameter pores having an average diameter of 15 nm to 100 nm at the surface of the anodized film and the small-diameter pores having an average diameter of 15 nm or less at the communicating positions.

22. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 17, wherein the micropores in the anodized film of the support are composed of small-diameter pores extending from the surface of the anodized film to a position at a depth of 10 nm to 1,000 nm and large-diameter pores that communicate with the bottoms of the small-diameter pores and extend from the communicating positions to a position at a depth of 20 nm to 2,000 nm, the average diameter of the small-diameter pores on the surface of the anodized film being 35 nm or less and the average maximum diameter of the large-diameter pores being 40 to 300 nm or less.

23. The on-press development type lithographic printing plate precursor according to any one of claims 1 to 17, wherein the support has an anodized film, the anodized film having, in order from the surface of the anodized film in the depth direction, an upper layer having a thickness of 30 to 500 nm and having micropores with an average diameter of 20 to 100 nm, a middle layer having a thickness of 100 to 300 nm and having micropores with an average diameter of 1 / 2 to 5 times the average diameter of the micropores in the upper layer, and a lower layer having a thickness of 300 to 2000 nm and having micropores with an average diameter of 15 nm or less.

24. A method for preparing a printing plate, comprising: a step of imagewise exposing the on-press development type lithographic printing plate precursor according to any one of claims 1 to 17; and a step of supplying at least one of printing ink and fountain solution on a printing press to remove unexposed areas of the image recording layer in the on-press development type lithographic printing plate precursor.

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