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

Abstract

Provided is an on-machine development-type lithographic printing plate precursor comprising a support body and an image recording layer on the support body. The image recording layer includes an onium compound, a borate compound, and a polymerizable compound. The solubility, with respect to 2-ethylhexyl methacrylate at 25°C, of a salt in which the cation part of the onium compound and the anion part of the borate compound are paired is 0.01 mass% or more. Also provided are: a method for producing a lithographic printing plate using the on-machine development type lithographic printing plate precursor; a lithographic printing method; and a laminate.

Description

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

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

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

[0003] Furthermore, growing concern about the global environment has focused attention on environmental issues related to wastewater from wet processes such as development. To address these environmental issues, efforts are being made to simplify development or platemaking, or to eliminate such processes. One simple production method is known as "on-press development." This method involves exposing a lithographic printing plate precursor to light, without the conventional development process, and directly mounting the plate on a printing press, and removing unnecessary portions of the image-recording layer at an early stage of the normal printing process. In the present disclosure, a lithographic printing plate precursor that can be used for such on-press development is referred to as an "on-press development type lithographic printing plate precursor."

[0004] Examples of conventional planographic printing plate precursors include those described in Patent Documents 1 and 2. Patent Document 1 describes a planographic printing plate precursor having an image recording layer on a support, the image recording layer containing an infrared absorber A, a borate compound B, an iodonium compound C, and a color former precursor D, and the surface free energy of the outermost layer on the image recording layer side is 115 mJ / m ２ Patent Document 2 discloses a lithographic printing plate precursor having a support and an image recording layer on the support, the image recording layer containing an infrared absorber, a polymerization initiator, and a polymer A, the weight average molecular weight of the polymer A being more than 15,000 and not more than 150,000, and the ethylenically unsaturated bond valence of the polymer A being 3.0 mmol / g or more.

[0005] Patent Document 1: International Publication No. 2023 / 145972 Patent Document 2: Japanese Patent Application Laid-Open No. 2023-179624

[0006] An object of one embodiment of the present disclosure is to provide an on-press development type lithographic printing plate precursor that exhibits excellent on-press development properties over time.An object of another embodiment of the present disclosure is to provide a method for producing a lithographic printing plate using the on-press development type lithographic printing plate precursor, or a lithographic printing method.An object of yet another embodiment of the present disclosure is to provide a stack of stacked on-press development type lithographic printing plate precursors that exhibits excellent on-press development properties over time.

[0007] Means for solving the above problems include the following aspects: <1> An on-press development type lithographic printing plate precursor having a support and an image recording layer on the support, the image recording layer containing an onium compound, a borate compound, and a polymerizable compound, and the solubility of a salt formed by a pair of a cation moiety of the onium compound and an anion moiety of the borate compound in 2-ethylhexyl methacrylate at 25°C is 0.01% by mass or more. <2> The on-press development type lithographic printing plate precursor according to <1>, wherein the borate compound contains a compound represented by the following formula (B1):

[0008] In formula (B1), R Ｂ１ ~R Ｂ４each independently represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkenyl group, or an unsubstituted or substituted alkynyl group; R Ｂ１ ~R Ｂ４ may each independently have a ring structure. Ｂ１ ~R Ｂ４ At least one of them is different from the others. ＋ represents a cation.

[0009] <3> R in the above formula (B1) Ｂ１ ~R Ｂ３ <4> The on-press development type lithographic printing plate precursor according to <2>, wherein at least two of R in formula (B1) are phenyl groups and at least one is a substituted aryl group. Ｂ１ ~R Ｂ３ is a phenyl group, and R Ｂ４ <5> The on-press development type lithographic printing plate precursor according to <2>, wherein R in the above formula (B1) is an aryl group having a substituent. Ｂ４ <4> The on-press development type lithographic printing plate precursor according to <4>, wherein the total number of carbon atoms and oxygen atoms of the substituents is 3 or more. <6> The on-press development type lithographic printing plate precursor according to any one of <1> to <5>, wherein the onium compound is an iodonium compound or a sulfonium compound. <7> The on-press development type lithographic printing plate precursor according to any one of <1> to <6>, wherein the onium compound is a diaryl iodonium compound represented by the following formula (5) or (6):

[0010] In formula (5) and formula (6), R ｉ５ ~R ｉ１４ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group; R ｉ５ ~R ｉ１４ At least two of X may be bonded to form a ring structure; － represents a counter anion.

[0011] <8> The on-press developable lithographic printing plate precursor according to any one of <1> to <7>, wherein the polymerizable compound contains a polyfunctional (meth)acrylate having 6 or more functional groups. <9> The on-press developable lithographic printing plate precursor according to any one of <1> to <8>, wherein the polymerizable compound contains a polymerizable compound having an aromatic ring. <10> The on-press developable lithographic printing plate precursor according to any one of <1> to <9>, wherein the image recording layer contains an infrared absorber, and the infrared absorber is a cyanine dye represented by the following formula (7):

[0012] In formula (7), 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.

[0013] <11> The on-press development type lithographic printing plate precursor according to <10>, wherein the infrared absorber is a compound represented by the following formula (8):

[0014] In formula (8), R １ is exposed to infrared light １ represents a group that cleaves the -L bond, and R ２ and R ３each 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.

[0015] <12> The on-press development type lithographic printing plate precursor according to <11>, wherein L in formula (8) is an oxygen atom. <13> The on-press development type lithographic printing plate precursor according to any one of <1> to <12>, wherein the support has an anodized film, and the micropores in the anodized film 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. <14> The on-press development type lithographic printing plate precursor according to any one of <1> to <12>, wherein the support has an anodized film, and the micropores in the anodized film 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 nm to 300 nm. <15> The on-press developable lithographic printing plate precursor according to any one of <1> to <12>, wherein the support has an anodized film, the anodized film having, in this 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 2,000 nm and having micropores with an average diameter of 15 nm or less. <16> A method for preparing a lithographic printing plate, comprising the steps of: imagewise exposing the on-press developable lithographic printing plate precursor according to any one of <1> to <15>; and supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image-recording layer in non-image areas.<17> A lithographic printing method comprising the steps of: imagewise exposing the on-press developable lithographic printing plate precursor according to any one of <1> to <15>; supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas to prepare a lithographic printing plate; and printing with the lithographic printing plate obtained. <18> A laminate comprising an on-press developable lithographic printing plate having an image recording layer laminated on a support, the image recording layer comprising an onium compound, a borate compound, and a polymerizable compound, the solubility of a salt formed by a pair of a cation moiety of the onium compound and an anion moiety of the borate compound in 2-ethylhexyl methacrylate at 25°C being 0.01% by mass or more, and a protective material disposed at least on the uppermost part of the laminate for protecting the on-press developable lithographic printing plate, the saturated mass per unit area of ​​the protective material at 25°C and 30% RH being X (g / m). ２ ), the saturated mass per unit area at 25°C and 80% RH is Y (g / m ２ ) satisfies the following formula (2): (Y-X) / Y≦0.06 (2) <19> The laminate according to <18>, wherein the protective material is at least one selected from the group consisting of cardboard, cardboard, laminated paper, plastic sheet, foam plastic sheet, and rubber sheet. <20> The laminate according to <18> or <19>, wherein the protective material has a thickness of 100 μm or more.

[0016] According to one embodiment of the present disclosure, it is possible to provide an on-press development type lithographic printing plate precursor that exhibits excellent on-press developability over time. Furthermore, according to another embodiment of the present disclosure, it is possible to provide a method for producing a lithographic printing plate using the on-press development type lithographic printing plate precursor, or a lithographic printing method. Furthermore, according to another embodiment of the present disclosure, it is possible to provide a stack of stacked on-press development type lithographic printing plate precursors that exhibits excellent on-press developability over time.

[0017] It is a schematic cross-sectional view of one embodiment of a support, a schematic cross-sectional view of another embodiment of a support, and a schematic view of an anodizing treatment apparatus used for anodizing treatment in a method for producing a support having an anodized coating.

[0018] The contents of the present disclosure will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment. In the present disclosure, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after the term are included as the lower and upper limits. Furthermore, in the notation of groups (atomic groups) in the present disclosure, notations that do not indicate substituted or unsubstituted encompass both unsubstituted and substituted groups. For example, the term "alkyl group" encompasses not only unsubstituted alkyl groups (unsubstituted alkyl groups) but also substituted alkyl groups (substituted alkyl groups). In the present disclosure, "(meth)acrylic" is a term used to encompass both acrylic and methacrylic groups, and "(meth)acryloyl" is a term used to encompass both acryloyl and methacryloyl groups. The term "process" in the present disclosure includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In the present disclosure, "mass %" and "wt %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Unless otherwise specified, in the present disclosure, each component in the composition or each structural unit in the polymer may be contained alone or in combination of two or more types. In the present disclosure, when a plurality of substances or structural units corresponding to each component or each structural unit in the polymer is present in the composition, the amount of each component in the composition or each structural unit in the polymer means the total amount of the corresponding plurality of substances present in the composition or the corresponding plurality of structural units present in the polymer, unless otherwise specified. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.Unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in this disclosure are molecular weights measured by a gel permeation chromatography (GPC) analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation) in THF (tetrahydrofuran) as a solvent, detected by a differential refractometer, and converted using polystyrene as a standard. In this disclosure, the term "lithographic printing plate precursor" encompasses not only lithographic printing plate precursors but also disposable plate precursors. The term "lithographic printing plate" encompasses not only lithographic printing plates prepared from lithographic printing plate precursors, if necessary, through procedures such as exposure and development, but also disposable plates. In the case of disposable plate precursors, exposure and development procedures are not necessarily required. It should be noted that a throwaway plate is a lithographic printing plate precursor that is attached to an unused plate cylinder when, for example, a portion of a page is printed in one color or two colors in color newspaper printing. In the present disclosure, "*" in a chemical structural formula indicates a bonding position with other structures.

[0019] (On-press development type lithographic printing plate precursor) The on-press development type lithographic printing plate precursor (also simply referred to as "lithographic printing plate precursor") according to the present disclosure has a support and an image recording layer on the support, the image recording layer containing an onium compound, a borate compound, and a polymerizable compound, and the solubility of a salt formed by a pair of a cation moiety of the onium compound and an anion moiety of the borate compound in 2-ethylhexyl methacrylate at 25°C is 0.01% by mass or more. The lithographic printing plate precursor according to the present disclosure is preferably a negative-working lithographic printing plate precursor in which exposed areas are polymerized by infrared exposure.

[0020] In conventional on-press development type lithographic printing plate precursors having an image recording layer containing an onium compound and a borate compound, a salt formed over time in which the cation moiety of the onium compound and the anion moiety of the borate compound are paired is formed, and this salt further aggregates and precipitates in the image recording layer, resulting in a problem of deterioration of on-press developability over time. In conventional on-press development type lithographic printing plate precursors, an acrylate compound or a methacrylate compound is preferably used as the polymerizable compound in the image recording layer. It is presumed that the lithographic printing plate precursor according to the present disclosure has improved solubility at 25°C of the salt formed in which the cation moiety of the onium compound and the anion moiety of the borate compound are paired in 2-ethylhexyl methacrylate, thereby suppressing aggregation and precipitation in the image recording layer, thereby enabling the provision of an on-press development type lithographic printing plate precursor that exhibits excellent on-press developability over time.

[0021] Hereinafter, each constituent element of the planographic printing plate precursor according to the present disclosure will be described in detail.

[0022] [Image Recording Layer] The image recording layer in the lithographic printing plate precursor according to the present disclosure is preferably a water-soluble or water-dispersible negative image recording layer. From the viewpoint of on-press developability, it is also preferable that the unexposed areas of the image recording layer are removable with at least one of fountain solution and printing ink.

[0023] Each component contained in the image recording layer will be described in detail below.

[0024] <Solubility of a Salt Formed by Pairing a Cation Moiety of an Onium Compound with an Anion Moiety of a Borate Compound in 2-Ethylhexyl Methacrylate at 25°C> The solubility of a salt formed by pairing a cation moiety of the onium compound with an anion moiety of the borate compound in 2-ethylhexyl methacrylate at 25°C is 0.01% by mass or more, and from the viewpoints of suppressing development defects over time (also referred to as "on-machine developability over time") and printing durability, it is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 10.0% by mass or more. There is no particular upper limit, and 2-ethylhexyl methacrylate and the salt may be mutually soluble at a mass ratio of 1:1 at 25°C.

[0025] The solubility of a salt in 2-ethylhexyl methacrylate at 25°C, in which the cation moiety of the onium compound and the anion moiety of the borate compound are paired, is measured as follows: The structures of the cation moiety of the onium compound and the anion moiety of the borate compound contained in the image recording layer are analyzed and clarified, and then a salt in which the cation moiety of the onium compound and the anion moiety of the borate compound are paired is separately prepared, and its solubility in 2-ethylhexyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is measured in an environment of 25°C. Structural analysis can be performed by a known method.

[0026] <Onium Compound> The image recording layer contains an onium compound as an electron-accepting polymerization initiator. In one embodiment, the electron-accepting polymerization initiator is a compound that generates a polymerization initiating species such as a radical by accepting one electron through intermolecular electron transfer when electrons of an infrared absorber are excited by infrared exposure. The onium compound used in the present disclosure is a compound that generates a polymerization initiating species such as a radical or a cation by the energy of light, heat, or both, and can be appropriately selected from known thermal polymerization initiators, compounds having a bond with low bond dissociation energy, photopolymerization initiators, and the like.

[0027] As the onium compound, from the viewpoint of printing durability, an iodonium compound, a sulfonium compound, or an azinium compound is preferred, an iodonium compound or a sulfonium compound is more preferred, and an iodonium compound is particularly preferred. Specific examples of these compounds are shown below, but the present disclosure is not limited thereto.

[0028] Preferred examples of iodonium compounds include diaryliodonium compounds, and more preferred are diphenyliodonium compounds substituted with electron-donating groups such as alkyl or alkoxy groups, and more preferred are asymmetric diphenyliodonium compounds. 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.

[0029] Specific examples of the onium compound include the compounds described in paragraphs 0044 to 0046 of WO 2020 / 262685.

[0030] The onium compound preferably contains a compound A represented by the following formula (Ia) and one or more compounds B selected from the group consisting of compounds represented by the following formula (Ib) or (Ic):

[0031]

[0032] In formulas (Ia) to (Ic), R １ , R ２ , R ３ , R４ , R ５ and R ６ are each independently a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group having 2 to 9 carbon atoms, and R ３ and R ４ At least one of １ or R ２ Unlike R １ and R ２ The total number of carbon atoms in ３ and R ４ the difference between the total number of carbon atoms in R is 0 to 4 (i.e., 0, 1, 2, 3, or 4); １ and R ２ The total number of carbon atoms in ５ and R ６ The difference between the total number of carbon atoms in X is 0 to 4. １ , X ２ and X ３ are the same or different anions.

[0033] The above R １ , R ２ , R ３ , R ４ , R ５ and R ６are each independently preferably a substituted or unsubstituted alkyl group having 2 to 9 carbon atoms or a substituted or unsubstituted alkoxy group having 2 to 9 carbon atoms, more preferably a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms or a substituted or unsubstituted alkoxy group having 3 to 6 carbon atoms, and even more preferably a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms. The alkyl and alkoxy groups may be linear or branched, but are preferably branched. Examples of substituted or unsubstituted alkyl groups include ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, t-pentyl, sec-pentyl, neopentyl, n-hexyl, isohexyl, sec-hexyl, t-hexyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, and n-nonyl. Examples of substituted or unsubstituted alkoxy groups include ethoxy, n-propoxy, isopropoxy, t-butoxy, n-butoxy, and n-octyloxy.

[0034] Above X １ , X ２ and X ３ Examples of the compound include ClO. ４ － , P.F. ６ － , B.F. ４ － , SbF ６ － , C.H. ３ SO ３ － , C.F. ３ SO ３ － , C ６ H ５ SO ３ － , C.H. ３ C ６ H ４ SO ３ － , H.O.C. ６ H ４ SO ３ － , ClC ６ H４ SO ３ － and borate anions represented by the following structure (Id):

[0035] B － (R １ ) (R ２ ) (R ３ ) (R ４ ) Formula (Id)

[0036] In formula (Id), R １ , R ２ , R ３ and R ４ R each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group (including a halogen-substituted aryl group), a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted heterocyclic group. １ , R ２ , R ３ and R ４ Two or more of R may be linked together to form a substituted or unsubstituted heterocycle containing a boron atom. The resulting heterocycle has up to seven carbon atoms, nitrogen atoms, oxygen atoms, or nitrogen atoms. １ , R ２ , R ３ and R ４ The substituent in the formula (I) may be a chlorine atom, a fluorine atom, a nitro group, an alkyl group, an alkoxy group, or an acetoxy group.

[0037] The above R １ , R ２ , R ３ and R ４ Preferably, all of the groups are substituted or unsubstituted aryl groups, and more preferably, all of the groups are unsubstituted phenyl groups.

[0038] Above X １ , X ２ and X ３ Preferably, at least one of X is a tetraarylborate anion containing the same or different aryl groups, and more preferably, one or more of X is a tetraphenylborate anion; １, X ２ and X ３ More preferably, each of is a tetraphenylborate anion.

[0039] In a preferred embodiment, the onium compound includes a compound represented by formula (Ic), and R １ is R ５ is the same as R ２ is R ６ In particular, R １ is R ２ is the same as, for example, R １ and R ２ are preferably iso-propyl, iso-butyl, or t-butyl groups.

[0040] In another preferred embodiment, the onium compound includes a compound represented by formula (Ib), and R １ is R ２ is the same as R ３ is R ４ In this case, R １ and R ２ Preferably, both of R are isopropyl, isobutyl, or t-butyl groups. １ and R ３ The difference in the number of carbon atoms between is preferably 1 or 2.

[0041] The compounds represented by formula (Ia) to formula (Ic) may be obtained from Sigma-Aldrich or the like, or may be synthesized using known synthetic methods and readily available starting materials.

[0042] From the viewpoint of suppressing development defects over time and printing durability, the onium compound is preferably a diaryl iodonium compound represented by the following formula (5) or formula (6).

[0043] In formula (5) and formula (6), R ｉ５ ~R ｉ１４ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group; Rｉ５ ~R ｉ１４ At least two of X may be bonded to form a ring structure; － represents a counter anion.

[0044] The diaryliodonium compound represented by formula (5) preferably has a symmetric cation moiety. The diaryliodonium compound represented by formula (6) preferably has an asymmetric cation moiety. ｉ５ ~R ｉ９ At least one of R is preferably a substituted or unsubstituted alkyl group. ｉ１０ ~R ｉ１４ At least one of the groups is preferably a substituted or unsubstituted alkyl group.

[0045] The above R ｉ５ ~R ｉ１４ are each independently preferably a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 9 carbon atoms, more preferably a hydrogen atom or a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms, and even more preferably a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms. The alkyl group may be linear or branched, but branched is preferred. Examples of substituted or unsubstituted alkyl groups include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, a t-pentyl group, a sec-pentyl group, a neopentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a t-hexyl group, an n-heptyl group, an n-octyl group, an iso-octyl group, a 2-ethylhexyl group, and an n-nonyl group.

[0046] Above X － Examples of the compound include ClO. ４ － , P.F. ６ － , B.F. ４ － , SbF ６ － , C.H. ３ SO ３ － , C.F.３ SO ３ － , C ６ H ５ SO ３ － , C.H. ３ C ６ H ４ SO ３ － , H.O.C. ６ H ４ SO ３ － , ClC ６ H ４ SO ３ － or the borate anion represented by the above structure (Id).

[0047] Furthermore, from the viewpoints of developability and printing durability of the resulting lithographic printing plate, the onium compound may contain a compound represented by formula (II) described in paragraphs 0186 to 0197 of WO 2022 / 019217.

[0048] From the viewpoints of improving sensitivity and preventing plate skipping, the lowest unoccupied molecular orbital (LUMO) of the onium compound is preferably −3.00 eV or less, more preferably −3.02 eV or less, and the lower limit is preferably −3.80 eV or more, more preferably −3.60 eV or more.

[0049] The onium compound may be used alone or in combination of two or more. From the viewpoints of visibility, printing durability, and coating solution stability, the content of the onium compound is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass, and particularly preferably 0.5% by mass to 7% by mass, relative to the total mass of the image recording layer.

[0050] <Borate Compound> The image recording layer contains a borate compound. The borate compound is used as an electron-donating polymerization initiator in the image recording layer. The borate compound is a compound that generates polymerization initiating species such as radicals or cations by the energy of light, heat, or both.

[0051] The borate compound is preferably a tetraarylborate compound or a monoalkyltriarylborate compound, and from the viewpoint of compound stability, a tetraarylborate compound is more preferred, and a tetraphenylborate compound is particularly preferred. The counter cation of the borate compound is not particularly limited, but is preferably an alkali metal ion or a tetraalkylammonium ion, and more preferably a sodium ion, a potassium ion, or a tetrabutylammonium ion.

[0052] The borate compound is preferably a compound represented by formula (B1) from the viewpoints of visibility, printing durability, and suppression of development defects over time.

[0053]

[0054] In formula (B1), R Ｂ１ ~R Ｂ４ each independently represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkenyl group, or an unsubstituted or substituted alkynyl group; R Ｂ１ ~R Ｂ４ may each independently have a ring structure. Ｂ１ ~R Ｂ４ At least one of them is different from the others. ＋ represents a cation.

[0055] R Ｂ１ ~R Ｂ４ Examples of the alkyl group represented by the formula (I) include alkyl groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a hexadecyl group, an octadecyl group, an eicosyl group, an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, an isopentyl group, a neopentyl group, a 1-methylbutyl group, an isohexyl group, a 2-ethylhexyl group, a 2-methylhexyl group, a cyclohexyl group, a cyclopentyl group, and a 2-norbornyl group. The alkyl group may be linear, branched, or have a ring structure.

[0056] Also, R Ｂ１ ~R Ｂ４ The alkyl group represented by R may have a substituent. Examples of the substituent of the alkyl group include a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, a sulfonyl group, an amino group, an amide group, and a combination thereof. Ｂ１ ~R Ｂ４ The alkyl groups represented by the formula (I) are each independently preferably an unsubstituted, linear or branched alkyl group having 1 to 12 carbon atoms, more preferably an unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms, and even more preferably an unsubstituted, linear or branched alkyl group having 1 to 6 carbon atoms. Of these, from the viewpoint of suppressing development defects over time, a branched, unsubstituted alkyl group is particularly preferred.

[0057] R Ｂ１ ~R Ｂ４ Examples of the aryl group represented by the formula (I) include aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, an indenyl group, an acenaphthenyl group, and a fluorenyl group. Examples of the substituent of the aryl group include the above-mentioned substituents of the alkyl group. Ｂ１ ~R Ｂ４ The aryl groups represented by the following formula (I) are each independently preferably an unsubstituted or substituted phenyl group.

[0058] R Ｂ１ ~R Ｂ４ Examples of the alkenyl group represented by R include alkenyl groups having 2 to 20 carbon atoms, such as vinyl, 1-propenyl, 1-butenyl, cinnamyl, and 2-chloro-1-ethenyl. Ｂ１ ~R Ｂ４ The alkenyl group represented by the formula (I) may be linear, branched, or have a ring structure. Examples of the substituent of the alkenyl group include the above-mentioned substituents of the alkyl group. Ｂ１ ~R Ｂ４ The alkenyl groups represented by the following formula (I) are each independently preferably an unsubstituted alkenyl group having 2 to 20 carbon atoms.

[0059] R Ｂ１ ~R Ｂ４ Examples of the alkynyl group represented by the formula (I) include alkynyl groups having 2 to 20 carbon atoms, such as an ethynyl group, a 1-propynyl group, a 1-butynyl group, a trimethylsilylethynyl group, a phenylethynyl group, etc. The alkynyl group may be linear or branched.

[0060] Among the above functional groups, R Ｂ１ ~R Ｂ４ are each preferably a substituted or unsubstituted aryl group. Ｂ１ ~R Ｂ４ are each independently a substituted or unsubstituted aryl group, the HOMO potential of the borate compound is lowered, improving the film stability of the image recording layer, thereby extending the life of the lithographic printing plate.

[0061] In this disclosure, R Ｂ１ ~R Ｂ４ At least one of them is different from the others. Ｂ１ ~R Ｂ４ Among them, R Ｂ１ ~R Ｂ３ are identical, and R Ｂ４ But, R Ｂ１ ~R Ｂ３ This allows a high purity borate compound to be obtained. In addition, the generation of radicals can be suppressed, making it difficult for side reactions to occur. In the above case, R Ｂ１ ~R Ｂ３ However, it is more preferably a phenyl group.

[0062] Also, R Ｂ１ ~R Ｂ４ It is also preferred that at least two of R are phenyl groups and at least one is a substituted aryl group. Ｂ１ ~R Ｂ３ At least two of R are phenyl groups; Ｂ４ is more preferably an aryl group having a substituent (i.e., a substituted aryl group), and R Ｂ１ ~R Ｂ３ is a phenyl group, and R Ｂ４is particularly preferably an aryl group having a substituent.

[0063] R Ｂ１ ~R Ｂ３ is a phenyl group, and R Ｂ４ When the aryl group has a substituent, the total number of carbon atoms and oxygen atoms in the substituent of the aryl group is preferably 2 or more, and more preferably 3 or more. The upper limit is, for example, 8 or less.

[0064] The compound represented by formula (B1) is preferably a compound represented by the following formula (B2):

[0065]

[0066] In formula (B2), R represents an alkyl group having two or more carbon atoms, or an alkoxy group having two or more carbon atoms and oxygen atoms in total. ＋ represents an iodonium cation or an infrared absorbing dye cation.

[0067] In formula (B2), the alkyl group represented by R preferably has 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms. Examples of the alkyl group include an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, an isobutyl group, a sec-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a neopentyl group, and an isopropyl group. The alkyl group may be linear, branched, or have a ring structure.

[0068] In formula (B2), the alkoxy group represented by R preferably has a total of 2 to 4 carbon atoms and oxygen atoms. Examples of the alkoxy group include a methoxy group, an n-propoxy group, an isopropoxy group, and an n-butoxy group. The alkoxy group may be linear or branched.

[0069] In addition, in formula (B1), R Ｂ１ ~R Ｂ３The phenyl group represented by the formula (I) is preferably a phenyl group substituted with an electron-withdrawing group. Examples of the electron-withdrawing group include a halogen atom and a fluoroalkyl group. Among these, a fluorine atom, a chlorine atom, and a fluoroalkyl group having 1 to 3 carbon atoms are preferred.

[0070] In formula (B1), R Ｂ４ The substituent that the aryl group represented by the formula (I) has is preferably an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, or an amide group, more preferably an alkyl group, an alkenyl group, or an alkoxy group, and still more preferably an alkyl group or an alkoxy group.

[0071] In the present disclosure, the compound represented by the above formula (B1) may be a compound represented by the following formula (B3).

[0072]

[0073] In formula (B3), R represents a group having a total number of carbon atoms and oxygen atoms of 2 or more, X represents a halogen atom, an alkyl group, or an alkoxy group, the sum of the Hammett values ​​of R and X is −0.09 to 0.09, and M ＋ Li ＋ , Na ＋ , K. ＋ , iodonium cation, or infrared absorbing dye cation.

[0074] Examples of R in formula (B3) include an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an ester group, a carbonyl group, a sulfonyl group, an amide group, and a combination thereof.

[0075] In formula (B3), examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, and a bromine atom. The alkyl group and alkoxy group represented by X in formula (B3) are the same as the alkyl group and alkoxy group in formula (II), and preferred embodiments are also the same.

[0076] In particular, R in formula (B3) is preferably an alkyl group having 2 to 4 carbon atoms or an alkoxy group having 2 to 4 carbon atoms in total, and more preferably an alkyl group having 2 to 4 carbon atoms. In the above case, X is preferably a halogen atom. Here, the halogen atoms may each independently be different halogen atoms, but it is more preferable that all of them are the same halogen atom.

[0077] In formula (B3), the sum of the Hammett σ values ​​of the substituents (R and X) introduced into the aryl skeleton is preferably within the range of -0.2 to 0.2, and more preferably within the range of -0.09 to 0.09. By having the sum within this range, the HOMO potential can be adjusted to a desired range, and the image recording layer has an excellent balance between film stability and printing durability. In the present disclosure, the sum of the Hammett σ values ​​of the substituents introduced into the aryl skeleton was calculated using the values ​​described in the reference "Chemical Seminar 10: Hammett Side - Structure and Reactivity -" (by Naoki Inamoto, Maruzen Co., Ltd., published in June 1983).

[0078] M in formula (B1) ＋ represents a cation. ＋ is a counter cation of the boron anion. ＋ is not particularly limited as long as it is a cation that can neutralize the boron anion, but from the viewpoint of suppressing staining during development, it is preferably at least one selected from the group consisting of inorganic cations, iodonium cations, and infrared absorbing dye cations. One counter cation may be used alone, or two or more counter cations may be used in combination. In formula (B3), M ＋ Li ＋ , Na ＋ , K. ＋ , an iodonium cation, or an infrared absorbing dye cation. ＋ represents an iodonium cation or an infrared absorbing dye cation.

[0079] When two or more counter cations are used, the combination is not particularly limited, but is preferably a combination of inorganic cations, a combination of iodonium cations, or a combination of infrared absorbing dye cations, and more preferably a combination of iodonium cations or a combination of infrared absorbing dye cations, which further improves the ability to suppress development defects over time and printing durability.

[0080] The iodonium cation may be the cation moiety of an electron-accepting polymerization initiator described later, and the infrared absorbing dye cation may be the cation moiety of an infrared absorber described later. In the image recording layer, the cation moiety of the electron-donating polymerization initiator and the cation moiety of the infrared absorber can bond with the anion moiety of the borate compound represented by formula (B1) to form a salt.

[0081] Examples of inorganic cations include lithium cations, sodium cations, potassium cations, calcium cations, and magnesium cations. Among these, sodium cations, lithium cations, and potassium cations are preferred, and sodium cations are more preferred.

[0082] As the iodonium cation, the cation moiety of the electron-accepting polymerization initiator described below can be used. Specific examples are shown in the following structural formulas: In the following structural formulas, Me represents a methyl group. Note that the iodonium cation is not limited to the following specific examples.

[0083]

[0084] The infrared absorbing dye cation can be the cation moiety of the infrared absorber described below. Specific examples are shown in the following structural formulas: In the following structural formulas, Me represents a methyl group, and Bu represents a butyl group. Note that the infrared absorbing dye cation is not limited to the following specific examples.

[0085]

[0086]

[0087] From the viewpoints of chemical resistance and printing durability, the highest occupied molecular orbital (HOMO) of the borate compound is preferably −6.0 eV or more, more preferably −5.95 eV or more, and even more preferably −5.93 eV or more. The upper limit is preferably −5.00 eV or less, more preferably −5.40 eV or less, and particularly preferably −5.93 eV to −5.70 eV.

[0088] In the present disclosure, calculations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are performed using the following method. First, the counter anion in the compound to be calculated is ignored. Quantum chemistry calculation software Gaussian09 is used, and structural optimization is performed using DFT (B3LYP / 6-31G(d)). MO (molecular orbital) energy calculations are performed using DFT (B3LYP / 6-31+G(d,p) / CPCM (solvent=methanol)) with the structure obtained by the structural optimization. The MO energy Ebare (unit: hearttree) obtained in the above MO energy calculation is converted to Escaled (unit: eV), which is used as the HOMO and LUMO values ​​in the present disclosure, using the following formula: Escaled = 0.823168 x 27.2114 x Ebare - 1.07634 Note that 27.2114 is simply a coefficient for converting heartle to eV, and 0.823168 and -1.07634 are adjustment coefficients that are determined so that the HOMO and LUMO of the compound to be calculated match the measured values.

[0089] Preferred specific examples of the borate compound represented by formula (B1) are shown below, but the invention is not limited to these: In the following structural formula, Me represents a methyl group.

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096] The image recording layer may contain only one kind of borate compound or may contain two or more kinds of borate compounds. From the viewpoints of visibility, printing durability, and coating solution stability, the content of the borate compound is preferably 0.01% by mass to 30% by mass, more preferably 0.1% by mass to 20% by mass, and even more preferably 0.5% by mass to 15% by mass, relative to the total mass of the image recording layer.

[0097] <Infrared absorber> The image recording layer preferably contains an infrared absorber. The infrared absorber is not particularly limited, and examples thereof include pigments and dyes. Examples of dyes that can be used as infrared absorbers include commercially available dyes and known dyes described in literature such as "Dye Handbook" (edited by the Society of Organic Synthetic Chemistry, published in 1970). Specific examples of such dyes include azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complex dyes.

[0098] Particularly preferred of these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Furthermore, cyanine dyes and indolenine cyanine dyes are also preferred. Of these, cyanine dyes are particularly preferred.

[0099] The infrared absorber is preferably a cationic polymethine dye having an oxygen or nitrogen atom at the meso position. Preferred examples of the cationic polymethine dye include cyanine dyes, pyrylium dyes, thiopyrylium dyes, and azulenium dyes. From the viewpoints of availability, solvent solubility during the introduction reaction, and the like, cyanine dyes are preferred.

[0100] 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.

[0101] The infrared absorber may also contain an infrared absorber (decomposable infrared absorber) other than the compound represented by formula (1) that decomposes upon exposure to infrared light. It is presumed that by using a decomposable infrared absorber as the infrared absorber, the infrared absorber or its decomposition products promote polymerization, and the decomposition products of the infrared absorber interact with the polymerizable compound, resulting in excellent printing durability. The decomposable infrared absorber is preferably an infrared absorber that has the function of absorbing infrared light, decomposing, and developing a color upon infrared exposure. Hereinafter, a color-developed compound formed by the decomposable infrared absorber absorbing infrared light and decomposing upon infrared exposure is also referred to as a "color-developing body of the decomposable infrared absorber." The decomposable infrared absorber 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 that absorbs and decomposes at least a portion of light in the infrared wavelength region (wavelength 750 nm to 1 mm), but is preferably an infrared absorbent having a maximum absorption wavelength in the wavelength region of 750 nm to 1,400 nm, and more preferably an infrared absorbent having a maximum absorption wavelength in the wavelength region of 760 nm to 900 nm. More specifically, the decomposable infrared absorbent is preferably a compound that decomposes due to exposure to infrared light to produce a compound having a maximum absorption wavelength in the wavelength region of 500 nm to 600 nm.

[0102] The decomposable infrared absorber is preferably an infrared absorber that decomposes due to heat, electron transfer, or both caused by infrared exposure, and more preferably an infrared absorber that decomposes due to electron transfer caused by infrared exposure. Here, "decomposes due to electron transfer" means that electrons excited from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) of the decomposable infrared absorber by infrared exposure undergo intramolecular electron transfer to an electron-accepting group (a group having a potential close to that of the LUMO) within the molecule, resulting in decomposition.

[0103] From the viewpoints of visibility and printing durability, the infrared absorber is preferably a cyanine dye represented by the following formula (7).

[0104] In formula (7), R １ is exposed to infrared light１ 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.

[0105] The above-mentioned heat or infrared exposure １ The group whose bond with -L is cleaved is not particularly limited as long as it is cleavable, but from the viewpoint of visibility, it is preferably a group represented by any one of formulas 2-1 to 4-1.

[0106]

[0107] In formulas 2-1 to 4-1, R ２０ , R ３０ , R ４１ and R ４２ each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line represents the bonding site with the group represented by L in the above formula (7).

[0108] When the compound of formula (7) is exposed to infrared light, R １ The -L bond is cleaved and L is ═O, ═S, or ═NR １０ The color changes as a result.

[0109] In formula 2-1, R ２０represents an alkyl group or an aryl group, and the wavy line portion represents the bonding site with the group represented by L in formula (7). ２０ The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and even more preferably an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear, branched, or have a ring structure. ２０ The aryl group represented by the formula (I) is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and even more preferably an aryl group having 6 to 12 carbon atoms. ２０ From the viewpoint of visibility, the group is preferably an alkyl group.

[0110] In addition, from the viewpoint of decomposability and visibility, R ２０ The alkyl group represented by R is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. ２０ The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, and is particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0111] Specific examples of the group represented by formula 2-1 above are listed below, but the present disclosure is not limited to these. In the following structural formula, ● represents the bonding site with the group represented by L in formula (7).

[0112]

[0113] In formula 3-1, R ３０ represents an alkyl group or an aryl group, and the wavy line portion represents the bonding site with the group represented by L in formula (7). ３０ The alkyl group and aryl group represented by the formula 2-1 are R ２０ The same applies to the alkyl and aryl groups represented by the following formula (1), and the preferred embodiments are also the same.

[0114] From the viewpoint of decomposability and visibility,３０ The alkyl group represented by R is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. ３０ The alkyl group represented by R is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, and is particularly preferably an isopropyl group or a tert-butyl group, with a tert-butyl group being most preferred. Furthermore, from the viewpoints of decomposability and visibility, R ３０ The alkyl group represented by the formula (I) is preferably a substituted alkyl group, more preferably a fluoro-substituted alkyl group, further preferably a perfluoroalkyl group, and particularly preferably a trifluoromethyl group.

[0115] From the viewpoint of decomposability and visibility, ３０ The aryl group represented by the formula (I) is preferably a substituted aryl group, and examples of the substituent include an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms) and an alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms).

[0116] Specific examples of the group represented by formula 3-1 above are listed below, but the present disclosure is not limited to these. In the following structural formula, ● represents the bonding site with the group represented by L in formula (7).

[0117]

[0118] In formula 4-1, R ４１ and R ４２ each independently represents an alkyl group or an aryl group, Zb represents a counter ion that neutralizes the charge, and the wavy line portion represents the bonding site with the group represented by L in formula (7). ４１ or R ４２ The alkyl group and aryl group represented by the formula 2-1 are R ２０ The preferred embodiments are the same as those of the alkyl and aryl groups represented by R ４１ From the viewpoints of decomposability and visibility, R is preferably an alkyl group. ４２From the viewpoints of decomposability and visibility, the group is preferably an alkyl group.

[0119] From the viewpoint of decomposability and visibility, ４１ The alkyl group represented by R is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group. ４２ The alkyl group represented by R is preferably a secondary alkyl group or a tertiary alkyl group, and more preferably a tertiary alkyl group. ４２ The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a branched alkyl group having 3 to 10 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms, and is particularly preferably an isopropyl group or a tert-butyl group, and most preferably a tert-butyl group.

[0120] Zb in formula 4-1 may be any counter ion for neutralizing the charge, and the entire compound may be included in Za in formula (7). Zb is preferably a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, or a perchlorate ion, and more preferably a tetrafluoroborate ion or a hexafluorophosphate ion.

[0121] Specific examples of the group represented by formula 4-1 above are listed below, but the present disclosure is not limited to these. In the following structural formula, ● represents the bonding site with the group represented by L in formula (7).

[0122]

[0123] In formula (7), L is an oxygen atom or —NR １０ - is preferred, and an oxygen atom is particularly preferred. １０ R in - １０ is preferably an alkyl group. １０ The alkyl group represented by R is preferably an alkyl group having 1 to 10 carbon atoms.１０ The alkyl group represented by the formula (I) may be linear, branched, or have a ring structure. Among the alkyl groups, a methyl group or a cyclohexyl group is preferred. １０ R in - １０ When is an aryl group, it 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. These aryl groups may have a substituent.

[0124] In formula (7), R １１ ~R １８ are each independently a hydrogen atom, -R ａ , -OR ｂ , -SR ｃ , or -NR ｄ R ｅ It is preferable that R ａ ~R ｅ The hydrocarbon group represented by the formula (I) is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably a hydrocarbon group having 1 to 15 carbon atoms, and even more preferably a hydrocarbon group having 1 to 10 carbon atoms. The hydrocarbon group may be linear, branched, or have a cyclic structure. As the hydrocarbon group, an alkyl group is particularly preferred.

[0125] The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and 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.

[0126] The alkyl group may have a substituent, and 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.

[0127] R in formula (7) １１ ~R １４ are each independently a hydrogen atom or -R ａ (i.e., a hydrocarbon group), more preferably a hydrogen atom or an alkyl group, and even more preferably a hydrogen atom, except in the following cases. １１ and R １３ is preferably an alkyl group, and more preferably both groups are bonded to form a ring. The ring formed may be a monocyclic ring or a polycyclic ring. Specific examples of the ring formed include monocyclic rings such as a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, and a cyclohexadiene ring, and polycyclic rings such as an indene ring and an indole ring. １ ＋ R bonded to the carbon atom to which １２ is R １５ or R １６ (Preferably R １６ ) to form a ring, and A ２ R bonded to the carbon atom to which １４ is R １７ or R １８ (Preferably R １８ ) to form a ring.

[0128] In formula (7), n １３ is 1, and R １６ is -R ａ (i.e., a hydrocarbon group). １６ A １ ＋ R bonded to the carbon atom to which １２It is preferable that n is 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 improving the visibility of the exposed area, an indolium ring is more preferable. These rings may further have a substituent. In formula (7), n １４ is 1, and R １８ is -R ａ (i.e., a hydrocarbon group). １８ A ２ R bonded to the carbon atom to which １４ It is preferable that R in formula (7) is 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 improving the visibility of the exposed area, an indole ring is more preferable. These rings may further have a substituent. １６ and R １８ are preferably the same group, and when each of them forms a ring, A １ ＋ and A ２ It is preferred that the rings have the same structure except for the following:

[0129] R in formula (7) １５ and R １７ are preferably the same group. １５ and R １７ is -R ａ (i.e., a hydrocarbon group), more preferably an alkyl group, and even more preferably a substituted alkyl group.

[0130] In the compound represented by formula (7), from the viewpoint of improving water solubility, R １５ and R １７ is preferably a substituted alkyl group. １５ or R １７ Examples of the substituted alkyl group represented by the formula (a1) include groups represented by any one of the following formulas (a1) to (a4).

[0131]

[0132] 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 each independently represents a single bond or an alkylene group having 1 to 12 carbon atoms, and M represents a hydrogen atom, a sodium atom, a potassium atom, or an onium group.

[0133] 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, etc., and an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferred, and an n-propylene group is 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, or a tert-butyl group is preferred, a methyl group or an ethyl group is 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:

[0134] Specific examples of the group represented by formula (a1) are shown below, but the present disclosure 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.

[0135]

[0136] In formulas (a2) to (a4), R Ｗ２ ~R Ｗ４ 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., and an ethylene group, an n-propylene group, an isopropylene group, or an n-butylene group is preferred, and an ethylene group or an n-propylene group is particularly preferred. In formula (a3), two M's may be the same or different.

[0137] In formulas (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. ２ M, PO in formula (a2) ３ M ２ , and SO in formula (a4) ３ Each of M may have an anionic structure in which M is dissociated. The counter cation of the anionic structure is A １ ＋ or R in formula (7) １ -It may be a cation that can be contained in L.

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

[0139] n in formula (7) １１ and n １２ are preferably the same, and are both preferably integers of 1 to 5, more preferably integers of 1 to 3, even more preferably 1 or 2, and particularly preferably 2.

[0140] A in formula (7) １ and A ２ each independently represents an oxygen atom, a sulfur atom, or a nitrogen atom, and a nitrogen atom is preferable. １ and A ２ are preferably the same atom.

[0141] Za in formula (7) represents a counter ion that neutralizes the charge. １１ ~R １８ and R １ If all of -L are charge-neutral groups, Za is a monovalent counter anion. １１ ~R １８ and R １ -L may have an anionic or cationic structure, for example, R １１ ~R １８ and R １ When -L has two or more anionic structures, Za can also serve as a counter cation. Note that, if the cyanine dye represented by formula (7) has a structure in which the entire compound, excluding Za, is charge-neutral, Za is not necessary. When Za serves as a counter anion, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, a perchlorate ion, and the like, with a tetrafluoroborate ion being preferred. When Za serves as a counter cation, examples thereof include an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, a sulfonium ion, and the like, with a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion being preferred, with a sodium ion, a potassium ion, or an ammonium ion being more preferred.

[0142] From the viewpoint of visibility, the infrared absorber is preferably a compound represented by the following formula (8):

[0143] In formula (8), 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 ２are 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.

[0144] R in formula (8) １ , L and Za are R in formula (7) １ , L and Za, and preferred embodiments are also the same.

[0145] Ar １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent other than -X. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, and a group formed by combining these groups, but an alkyl group is preferred.

[0146] R ２ ~R １０ 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 methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, s-butyl, t-butyl, isopentyl, neopentyl, 1-methylbutyl, isohexyl, 2-ethylhexyl, 2-methylhexyl, cyclohexyl, cyclopentyl, and 2-norbornyl. Of these alkyl groups, methyl, ethyl, propyl, and butyl are particularly preferred.

[0147] The alkyl group may have a substituent, such as an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, or a combination thereof.

[0148] R １０ and R ０The aryl group in (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 of the aryl group include a phenyl group, a naphthyl group, a p-tolyl group, a p-chlorophenyl group, a p-fluorophenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, a p-methylthiophenyl group, and a p-phenylthiophenyl group. Of these aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, or a naphthyl group is preferred.

[0149] R ２ and R ３ are preferably linked to form a ring. ２ and R ３ When R are linked to form a ring, the number of ring members is preferably 5 or 6, and more preferably 6. ２ and R ３ The ring formed by linking the groups is preferably a hydrocarbon ring which may have an ethylenically unsaturated bond.

[0150] 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.

[0151] R ４ and R ５ are preferably the same group. ４ and R ５are each independently preferably a linear alkyl group or an alkyl group having a terminal sulfonate group, more preferably a methyl group, an ethyl group, or a butyl group having a terminal sulfonate group. The counter cation of the sulfonate group may be a cation on the nitrogen atom in formula (8), or may be an alkali metal cation or an alkaline earth metal cation. Furthermore, from the viewpoint of making the compound represented by formula (8) water-soluble, R ４ and R ５ are each independently preferably an alkyl group having an anionic structure, more preferably an alkyl group having a carboxylate group or a sulfonate group, and even more preferably an alkyl group having a sulfonate group at the terminal. ４ and R ５ are each independently preferably an alkyl group having an aromatic ring, more preferably an alkyl group having an aromatic ring at a terminal, and particularly preferably a 2-phenylethyl group, a 2-naphthalenylethyl group, or a 2-(9-anthracenyl)ethyl group.

[0152] R ６ ~R ９ each independently represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom.

[0153] In addition, the compound represented by formula (8) preferably has one or more halogen atoms from the viewpoint of stability over time and printing durability, and R １ , Ar １ and Ar ２ It is more preferable that at least one selected from the group consisting of has one or more halogen atoms, and A １ , Ar １ and Ar ２It is particularly preferred that each of Ar has one or more halogen atoms. Furthermore, from the viewpoint of stability over time and printing durability, the compound represented by formula (8) more preferably has two or more halogen atoms, even more preferably has three or more halogen atoms, and particularly preferably has three to six halogen atoms. Furthermore, preferred examples of the halogen atom include a chlorine atom or a bromine atom. Furthermore, from the viewpoint of stability over time and printing durability, the compound represented by formula 1 １ and Ar ２ At least one of Ar and Ar preferably has a halogen atom. １ and Ar ２ It is more preferable that at least one of Ar has a chlorine atom or a bromine atom. １ and Ar ２ It is particularly preferred that at least one of them has a bromine atom.

[0154] In addition, as the infrared absorber and the infrared absorber that decomposes upon infrared exposure, those described in WO 2020 / 262692 can be suitably used. Furthermore, as the infrared absorber that decomposes upon infrared exposure, those described in JP-A 2008-544322 or WO 2016 / 027886 can be suitably used. In addition, as the cyanine dye that is a decomposable infrared absorber, the infrared absorbing compound described in WO 2019 / 219560 can be suitably used.

[0155] Furthermore, when a printing plate precursor containing an infrared absorber is stored in air, the infrared absorber may be decomposed by ozone contained in the air, for example, via the following intermediate structure.

[0156]

[0157] From the viewpoint of improving stability against ozone, it is preferable that the infrared absorber has a lower HOMO energy level, preferably −5.20 eV or less, more preferably −5.30 eV or less, and even more preferably −5.40 eV or less.

[0158] Furthermore, from the viewpoint of improving stability against ozone and suppressing ozone decomposition, the infrared absorber is preferably a compound represented by the following formula (1):

[0159]

[0160] R １ and R ２ each independently represents a hydrogen atom or an alkyl group; R １ and R ２ may be linked to each other to form a ring, R ３ ~R ６ each independently represents a hydrogen atom or an alkyl group; R ７ and R ８ each independently represents an alkyl group or an aryl group; 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; Ar １ and Ar ２ each independently represents a group forming a benzene ring or a naphthalene ring which may have a group represented by the formula 2 described below; A １ is -NR ９ R １０ , -X １ -X １１ -L １ or a group represented by formula 2 described below, R ９ and R １０ each independently represents an alkyl group, an aryl group, an alkoxycarbonyl group, an arylsulfonyl group, or a trihaloalkylsulfonyl group; X １ represents an oxygen atom or a sulfur atom, and X １１ represents a single bond or an alkylene group, L １ is a hydrocarbon group, a heteroaryl group, or a group that is converted by heat or infrared exposure to X １ X represents a halogen atom, —C(═O)—X, and Za represents a counter ion that neutralizes the charge. ２ -R １１ , -C(=O)-NR １２ R １３, -OC(=O)-R １４ , -CN, -SO ２ NR １５ R １６ or a perfluoroalkyl group, X ２ represents a single bond or an oxygen atom, R １１ represents a hydrogen atom, an alkyl group, or an aryl group; R １４ represents an alkyl group or an aryl group, R １２ , R １３ , R １５ and R １６ each independently represents a hydrogen atom, an alkyl group, or an aryl group.

[0161] Ar １ and Ar ２ Each of Ar independently represents a group forming a benzene ring or a naphthalene ring. The benzene ring and the naphthalene ring may have a substituent other than -X. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a carboxylate group, a sulfo group, a sulfonate group, and a group formed by combining these groups, but an alkyl group is preferred. １ and Ar ２ may each independently have a group represented by the above formula 2. In addition, in formula (1), as a preferred embodiment, Ar １ and Ar ２ In a preferred embodiment, from the viewpoint of printing durability and reducing the HOMO value, １ and Ar ２ It is preferable that both Ar and Ar have a group represented by the above formula 2. １ and Ar ２ At least one of the groups may have a plurality of groups represented by the above formula 2.

[0162] X in formula 2 is a halogen atom, —C(═O)—X ２ -R １１ , -C(=O)-NR １２ R １３ , -OC(=O)-R １４ , -CN, -SO ２ NR １５R １６ or a perfluoroalkyl group, and from the viewpoint of lowering the HOMO of the specific infrared absorbent and suppressing decomposition of the specific infrared absorbent over time, a halogen atom, —C(═O)—X ２ -R １１ , -C(=O)-NR １２ R １３ , -OC(=O)-R １４ , -CN, or -SO ２ NR １５ R １６ is preferably a halogen atom, —C(═O)—O—R １１ , -C(=O)-NR １２ R １３ , or —O—C(═O)—R １４ is preferably a halogen atom, —C(═O)—O—R １１ , or —O—C(═O)—R １４ It is more preferable that the group is a fluorine atom, a chlorine atom, a bromine atom, or —C(═O)—O—R ２０ The halogen atom is, for example, a fluorine atom, a chlorine atom, or a bromine atom, with a chlorine atom being preferred.

[0163] X ２ represents a single bond or an oxygen atom, and is preferably an oxygen atom. １１ represents a hydrogen atom, an alkyl group, or an aryl group, and is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. １４ represents an alkyl group or an aryl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. １２ , R １３ , R １５ and R １６R each independently represents a hydrogen atom, an alkyl group, or an aryl group, and is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and even more preferably an alkyl group having 1 to 12 carbon atoms. ２０ represents a hydrogen atom, an alkyl group, or an aryl group, and is preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms.

[0164] The alkyl group or aryl group may have a substituent, such as an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, or a combination thereof.

[0165] A １ is -NR ９ R １０ , -X １ -X １１ -L １ or -X, and from the viewpoint of suppressing decomposition of the specific infrared absorber over time, -NR ９ R １０ or -X １ -X １１ -L １ Preferably, —NR １７ R １８ , or -S-X １２ -R １９ It is more preferable that:

[0166] R ９ and R １０ each independently represents an alkyl group, an aryl group, an alkoxycarbonyl group, an arylsulfonyl group, or a trihaloalkylsulfonyl group. The alkyl group in the alkoxycarbonyl group is ９ and R １０ The aryl group in the arylsulfonyl group can be the same as the alkyl group in R ９ and R１０ The alkyl group in the trihaloalkylsulfonyl group is the same as the aryl group in R ９ and R １０ Examples of the trihaloalkylsulfonyl group include a trifluoromethylsulfonyl group. ９ and R １０ are each independently preferably an alkyl group, an aryl group, or a trihaloalkylsulfonyl group, preferably an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms.

[0167] X １ represents an oxygen atom or a sulfur atom, L １ When L is a hydrocarbon group or a heteroaryl group, it is preferably a sulfur atom. １ X is converted by heat or infrared exposure １ It is preferable that the bond between L and １ X is converted by heat or infrared exposure １ When the bond to X represents a cleavable group, １１ is a single bond. １１ and X １２ each independently represents a single bond or an alkylene group, preferably a single bond or an alkylene group having 1 to 5 carbon atoms, and more preferably a single bond or an alkylene group having 1 to 3 carbon atoms.

[0168] L １ is a hydrocarbon group, a heteroaryl group, or a group that is converted by heat or infrared exposure to X １ From the viewpoint of printing durability, a hydrocarbon group or a heteroaryl group is preferable, an aryl group or a heteroaryl group is more preferable, and a heteroaryl group is even more preferable. １ From the viewpoint of image contrast development by infrared exposure, X １ A group in which the bond to X is cleaved by heat or infrared exposure is preferred. １ The group that cleaves the bond with R will be described later. １７and R １８ R each independently represents an aryl group, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl group. １９ represents a hydrocarbon group or a heteroaryl group, preferably an aryl group or a heteroaryl group, and more preferably a heteroaryl group.

[0169] L １ and R １９ The heteroaryl group in the formula (I) is not particularly limited, but the following groups are preferred.

[0170]

[0171] R ３１ represents a hydrogen atom, an alkyl group, an aryl group, or an alkenyl group. ３２ ~R ３４ each independently represents a hydrogen atom, an alkyl group, an aryl group, or an alkenyl group. n1 to n3 each independently represent an integer of 1 to 4. When n1 to n3 are integers of 2 to 4, a plurality of R32, a plurality of R ３３ , multiple R ３４ may be the same or different. * represents a bonding position.

[0172] R １ ~R １０ , R ０ , and R ３１ ~R ３４The 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, even more preferably an alkyl group having 1 to 12 carbon atoms, and particularly 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 methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, s-butyl, t-butyl, isopentyl, neopentyl, 1-methylbutyl, isohexyl, 2-ethylhexyl, 2-methylhexyl, cyclohexyl, cyclopentyl, and 2-norbornyl. Of these alkyl groups, methyl, ethyl, propyl, and butyl are particularly preferred.

[0173] The alkyl group may have a substituent, such as an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group, a halogen atom, a carboxy group, a carboxylate group, a sulfo group, a sulfonate group, an alkyloxycarbonyl group, an aryloxycarbonyl group, or a combination thereof.

[0174] R ７ , R ８ , R ９ , R １０ , R １８ , R １９ , R ０ , and R ３１ ~R ３４The aryl group in (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 of the aryl group include a phenyl group, a naphthyl group, a p-tolyl group, a p-chlorophenyl group, a p-fluorophenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, a p-methylthiophenyl group, and a p-phenylthiophenyl group. Of these aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, and a naphthyl group are preferred.

[0175] R ３１ ~R ３４ The alkenyl group in the formula (I) is preferably an alkenyl group having 2 to 30 carbon atoms, more preferably an alkenyl group having 2 to 15 carbon atoms, and even more preferably an alkenyl group having 2 to 10 carbon atoms. The alkyl group may be linear, branched, or have a cyclic structure. The alkenyl group may also 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. Specific examples of the alkenyl group include a vinyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, and a cyclohexenyl group. Of these alkenyl groups, a vinyl group or a propenyl group is preferred.

[0176] R １ and R ２ are preferably linked to form a ring. １ and R ２When R are linked to form a ring, the number of ring members is preferably 5 or 6, and more preferably 6. １ and R ２ The ring to which the groups are linked is preferably a hydrocarbon ring which may have an ethylenically unsaturated bond.

[0177] 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.

[0178] R ７ and R ８ are preferably the same group. ７ and R ８ are each independently preferably a linear alkyl group or an alkyl group having a terminal sulfonate group, more preferably a methyl group, an ethyl group, or a butyl group having a terminal sulfonate group. The counter cation of the sulfonate group may be a cation on the nitrogen atom in formula (1), or may be an alkali metal cation or an alkaline earth metal cation. Furthermore, from the viewpoint of making the compound represented by formula (1) water-soluble, R ７ and R ８ are each independently preferably an alkyl group having an anionic structure, more preferably an alkyl group having a carboxylate group or a sulfonate group, and even more preferably an alkyl group having a sulfonate group at the terminal.

[0179] R ３ ~R ６ each independently represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom.

[0180] Za represents a counter ion that neutralizes the charge, and when it represents an anion species, examples thereof include a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a tetraphenylborate ion, a hexafluorophosphate ion, a perchlorate ion, a sulfonamide anion, and a sulfonimide anion. When it represents a cation species, an alkali metal ion, an alkaline earth metal ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is preferred, a sodium ion, a potassium ion, an ammonium ion, a pyridinium ion, or a sulfonium ion is more preferred, a sodium ion, a potassium ion, or an ammonium ion is even more preferred, and a sodium ion, a potassium ion, or a trialkylammonium ion is particularly preferred. Among these, Za is preferably an organic anion containing a carbon atom, more preferably a sulfonate ion, a carboxylate ion, a sulfonamide anion, or a sulfonimide anion, more preferably a sulfonamide anion or a sulfonimide anion, and particularly preferably a sulfonimide anion. R １ ~R ８ , R ０ , A １ , Ar １ , Ar ２ , Y １ and Y ２ may have an anionic structure or a cationic structure, and R １ ~R ８ , R ０ , A １ , 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 ８ , R ０ , A １ , Ar １ , Ar ２ , Y １ and Y ２In the case where the compound has two or more anionic structures, Za can also serve as a counter cation. In addition, in formula (1), Za may be omitted if the moieties other than Za are neutral in charge.

[0181] The total content of the infrared absorbing agents in the image recording layer is preferably 0.1% by mass to 10.0% by mass, more preferably 0.5% by mass to 5.0% by mass, based on the total mass of the image recording layer.

[0182] Furthermore, preferred examples of the relationship between the borate compound (electron-donating polymerization initiator), the onium compound (electron-accepting polymerization initiator), and the infrared absorber include the relationship between the HOMO and LUMO of each compound described in paragraphs 0081 to 0083 of WO 2023 / 023681.

[0183] <Color Former> The image recording layer preferably further contains a color former, and more preferably contains an acid color former as the color former. As used herein, the term "color former" refers to a compound that develops or fades color in response to a stimulus such as light or acid, thereby changing the color of the image recording layer. The term "acid color former" refers to a compound that develops or fades color in response to a stimulus such as light or acid, thereby changing the color of the image recording layer. The term "acid color former" refers to a compound that develops or fades color in response to a stimulus such as light or acid, thereby changing the color of the image recording layer. The acid color former is preferably a colorless compound that has a partial skeleton such as a lactone, lactam, sultone, spiropyran, ester, or amide, and that rapidly undergoes ring-opening or cleavage upon contact with the electron-accepting compound.

[0184] Examples of such acid color formers include those described in paragraphs 0229 to 0236 of WO 2020 / 262685.

[0185] Among these, from the viewpoint of color development, the color former used in the present disclosure is preferably at least one compound selected from the group consisting of spiropyran compounds, spirooxazine compounds, spirolactone compounds, and spirolactam compounds. From the viewpoint of visibility, the hue of the dye after color development is preferably green, blue, or black.

[0186] Furthermore, from the viewpoints of color development and visibility of exposed areas, the acid color former is preferably a leuco dye. The leuco dye is not particularly limited as long as it has a leuco structure, but it is preferably a dye having a spiro structure, and more preferably a dye having a spirolactone ring structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye is preferably a leuco dye having a phthalide structure or a fluoran structure. Furthermore, from the viewpoints of color development and visibility of exposed areas, the leuco dye having a phthalide structure or a fluoran structure is preferably a compound represented by any one of the following formulas (Le-1) to (Le-3), and more preferably a compound represented by the following formula (Le-2).

[0187]

[0188] 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.

[0189] 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 disclosure, the ortho position in an aryl group or heteroaryl group other than a phenyl group refers to the bonding position (e.g., the 2nd position, etc.) adjacent to the bonding position 1 of the aryl group or heteroaryl group to another structure.Furthermore, from the viewpoints of color development and visibility of exposed areas, the electron-donating group 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.

[0190] 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.

[0191] 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):

[0192] 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.

[0193] 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.

[0194] 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):

[0195]

[0196] 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.

[0197] 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 formula (Le-8), from the viewpoint of color development and visibility of exposed areas, X １ ~X ４ is a hydrogen atom, and Y １ and Y ２ is preferably C. Furthermore, in formula (Le-8), from the viewpoint of color development and visibility of exposed areas, it is preferable that Rb １ and Rb 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.

[0198] From the viewpoints of color development and visibility of exposed areas, the acid color former also preferably contains one or more compounds selected from the group consisting of compounds represented by the following formula (Le-10) and compounds represented by the following formula (Z-4): In other words, the image recording layer in the lithographic printing plate precursor according to the present disclosure preferably further contains one or more compounds selected from the group consisting of compounds represented by the following formula (Le-10) and compounds represented by the following formula (Z-4):

[0199]

[0200] 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.

[0201] Ar in formula (Le-10) １ represents Rb in formulas (Le-7) to (Le-9). １ and Rb ２ The same applies to the preferred embodiments of Ar in formula (Le-10). ２ is Rc in formulas (Le-7) to (Le-9). １ and Rc ２ The same applies to the preferred embodiments.

[0202] The alkyl group in formulas (Le-1) to (Le-9) may be linear, branched, or have a ring structure. The number of carbon atoms in the alkyl group in formulas (Le-1) to (Le-9) is preferably 1 to 20, more preferably 1 to 8, even more preferably 1 to 4, and particularly preferably 1 or 2. The number of carbon atoms in the aryl group in formulas (Le-1) to (Le-10) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8. Specific examples of the aryl group in formulas (Le-1) to (Le-10) include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group, each of which may have a substituent. Specific examples of the heteroaryl group in formulas (Le-1) to (Le-10) include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group, each of which may have a substituent.

[0203] Furthermore, each of the monovalent organic groups, alkyl groups, aryl groups, heteroaryl groups, dialkylanilino groups, alkylamino groups, alkoxy groups, and the like in Formulae (Le-1) to (Le-10) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a heteroarylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a monoalkylmonoheteroarylamino group, a diarylamino group, a diheteroarylamino group, a monoarylmonoheteroarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heteroaryloxycarbonyl group, and a cyano group. Furthermore, these substituents may be further substituted with other substituents.

[0204]

[0205] In formula (Z-4), Rza １ represents a hydrogen atom, an alkyl group, or an alkoxy group; Rzb １ ~Rb ４ each independently represents a hydrogen atom, an alkyl group, or an aryl group; Rzb １ and Rzb ２ , Rzb ３ and Rzb ４ may be linked to form a ring structure, X represents O or NR, R represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, Y １ and Y ２ each independently represents CH or N.

[0206] Rza in formula (Z-4) １ is preferably an alkyl group or an alkoxy group. １ and Rzb ２ are each preferably independently an alkyl group. ３ and Rzb ４are each independently a hydrogen atom, an alkyl group, or an aryl group, and it is preferable that one of them is an aryl group. １ and Y ２ is preferably CH.

[0207] The alkyl group in formula (Z-4) may be linear, branched, or have a cyclic structure. The number of carbon atoms in the alkyl group in formula (Z-4) is preferably 1 to 20, more preferably 1 to 8, and even more preferably 1 to 5. The number of carbon atoms in the aryl group in formula (Z-4) is preferably 6 to 20, more preferably 6 to 10, and particularly preferably 6 to 8. Each group, such as the alkyl group or aryl group, in formula (Z-4) may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a halogen atom, an amino group, an alkylamino group, an arylamino group, a dialkylamino group, a monoalkylmonoarylamino group, a diarylamino group, a hydroxy group, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a cyano group. Furthermore, these substituents may be further substituted with other substituents.

[0208] Furthermore, examples of the leuco dye having a phthalide structure or a fluoran structure that can be suitably used include the acid color formers described in paragraphs 0160 to 0168 of WO 2023 / 032681.

[0209] Furthermore, the following compounds are also suitable as acid color formers.

[0210]

[0211] As the color former, commercially available products can be used, such as ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H-3035, BLUE203, ATP, H-1046, and H-2114 (all manufactured by Fukui Yamada Chemical Co., Ltd.), ORANGE-DCF, and Vermilion. Examples of such dyes include n-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF, and TH-107 (all manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-Black XV, Blue-63, Blue-502, GN-169, GN-2, Green-118, Red-40, and Red-8 (all manufactured by Yamamoto Chemical Industry Co., Ltd.), and crystal violet lactone (manufactured by Tokyo Chemical Industry Co., Ltd.). Among these commercially available products, ETAC, S-205, BLACK 305, BLACK 400, BLACK 100, BLACK 500, H-7001, GREEN 300, NIRBLACK 78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63, GN-169, and crystal violet lactone are preferred because the films they form have good visible light absorptance.

[0212] These color formers may be used alone or in combination of two or more. The content of the color former is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass, based on the total mass of the image recording layer.

[0213] <Polymerizable Compound> The image recording layer preferably contains a polymerizable compound. In the present disclosure, a polymerizable compound refers to a compound having a polymerizable group. The polymerizable group is not particularly limited as long as it is a known polymerizable group, but is preferably an ethylenically unsaturated group. The polymerizable group may be either a radically polymerizable group or a cationically polymerizable group, but is preferably a radically polymerizable group. Examples of the radically polymerizable group include a (meth)acryloyl group, an allyl group, a vinylphenyl group, and a vinyl group, and from the viewpoint of reactivity, a (meth)acryloyl group is preferred. The molecular weight of the polymerizable compound (weight average molecular weight when the polymerizable compound has a molecular weight distribution) is preferably 50 or more and less than 2,500.

[0214] The polymerizable compound may be, for example, a radically polymerizable compound or a cationically polymerizable compound, but is preferably an addition-polymerizable compound (ethylenically unsaturated compound) having at least one ethylenically unsaturated bond. The ethylenically unsaturated compound is preferably a compound having at least one terminal ethylenically unsaturated bond, and more preferably a compound having two or more terminal ethylenically unsaturated bonds. The polymerizable compound has a chemical form such as a monomer, a prepolymer, i.e., a dimer, trimer, or oligomer, or a mixture thereof. Among these, from the viewpoint of printing durability, the polymerizable compound preferably contains a bifunctional or higher functional polymerizable compound, more preferably a hexafunctional or higher functional polymerizable compound, and even more preferably a 10-functional or higher functional polymerizable compound. Furthermore, from the viewpoint of printing durability of the resulting lithographic printing plate, the polymerizable compound more preferably contains a bifunctional or higher functional (meth)acrylate compound (preferably a hexafunctional or higher functional, more preferably a 10-functional or higher functional) polyfunctional (meth)acrylate compound.

[0215] From the viewpoints of on-press developability and stain suppression, the polymerizable compound preferably contains a difunctional or lower polymerizable compound, more preferably a difunctional polymerizable compound, and particularly preferably a difunctional (meth)acrylate compound. From the viewpoints of printing durability, on-press developability, and stain suppression, the content of the difunctional or lower polymerizable compound (preferably a bifunctional polymerizable compound) is preferably 5% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, and particularly preferably 15% by mass to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0216] From the viewpoint of on-press developability, the polymerizable compound preferably has a smaller weight-average molecular weight, and from the viewpoint of printing durability, the weight-average molecular weight is preferably larger. From the viewpoint of achieving both on-press developability and printing durability, the weight-average molecular weight of the polymerizable compound 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.

[0217] From the viewpoint of suppressing development defects over time, the polymerizable compound preferably contains a polymerizable compound having an aromatic ring. The proportion of aromatic rings in a molecule is preferably one or more, more preferably two or more, and even more preferably three or more per molecule.

[0218] The polymerizable compound contained in the image recording layer preferably contains a polymerizable compound that is an oligomer (hereinafter simply referred to as "oligomer"). In the present disclosure, an oligomer refers to a polymerizable compound having a molecular weight (weight average molecular weight when the molecular weight distribution is present) of 600 to 15,000 and containing at least one polymerizable group. From the viewpoint of excellent chemical resistance and printing durability, the molecular weight of the oligomer is preferably 1,000 to 15,000.

[0219] Furthermore, from the viewpoint of improving printing durability, the number of polymerizable groups in one molecule of the oligomer is preferably 2 or more, more preferably 3 or more, even more preferably 6 or more, and particularly preferably 10 or more. Furthermore, there is no particular upper limit to the number of polymerizable groups in the oligomer, but the number of polymerizable groups is preferably 20 or less.

[0220] From the viewpoints of printing durability and on-press developability, the oligomer preferably has 7 or more polymerizable groups and a molecular weight of 1,000 to 15,000, and more preferably has 7 or more polymerizable groups and a molecular weight of 1,000 to 15,000. The oligomer may contain polymer components that may be generated during the production process of the oligomer.

[0221] From the viewpoints of printing durability, visibility, and on-press developability, the oligomer preferably contains at least one selected from the group consisting of a compound having a urethane bond, a compound having an ester bond, and a compound having an epoxy residue, and more preferably contains a compound having a urethane bond. In the present disclosure, the epoxy residue refers to a structure formed by an epoxy group, and means, for example, a structure similar to the structure obtained by the reaction of an acid group (such as a carboxylic acid group) with an epoxy group.

[0222] The compound having a urethane bond, which is an example of the oligomer, is preferably, for example, a compound having at least a group represented by the following formula (Ac-1) or formula (Ac-2), and more preferably a compound having at least a group represented by the following formula (Ac-1).

[0223]

[0224] In formula (Ac-1) and formula (Ac-2), L １ ~L ４ Each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and the wavy line represents the bonding position to other structures. １ ~L ４are each independently preferably an alkylene group having 2 to 20 carbon atoms, more preferably an alkylene group having 2 to 10 carbon atoms, and even more preferably an alkylene group having 4 to 8 carbon atoms. The alkylene group may have a branched or cyclic structure, but is preferably a linear alkylene group.

[0225] It is preferred that the wavy line portions in formula (Ac-1) or formula (Ac-2) are each independently directly bonded to the wavy line portions in the groups represented by formula (Ae-1) or formula (Ae-2) below.

[0226]

[0227] In formula (Ae-1) and formula (Ae-2), R each independently represents an acryloyloxy group or a methacryloyloxy group, and the wavy line portion represents the bonding position to the wavy line portion in formula (Ac-1) and formula (Ac-2).

[0228] Alternatively, the compound having a urethane bond may be a compound obtained by introducing a polymerizable group into a polyurethane obtained by reacting a polyisocyanate compound with a polyol compound through a polymer reaction. For example, a compound having a urethane bond may be obtained by reacting a polyurethane oligomer obtained by reacting a polyol compound having an acid group with a polyisocyanate compound with a compound having an epoxy group and a polymerizable group.

[0229] The number of polymerizable groups in the compound having an ester bond, which is an example of an oligomer, is preferably 3 or more, and more preferably 6 or more.

[0230] As a compound having an epoxy residue, which is an example of an oligomer, a compound containing a hydroxy group is preferred. The number of polymerizable groups in the compound having an epoxy residue is preferably 2 to 6, and more preferably 2 to 3. The compound having an epoxy residue can be obtained, for example, by reacting a compound having an epoxy group with acrylic acid.

[0231] Specific examples of oligomers are shown in the table below, but the oligomers used in the present disclosure are not limited to these. Commercially available oligomers may be used, and examples thereof include UA510H, UA-306H, UA-306I, and UA-306T (all manufactured by Kyoeisha Chemical Co., Ltd.), UV-1700B, UV-6300B, and UV7620EA (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), U-15HA (manufactured by Shin-Nakamura Chemical Co., Ltd.), EBECRYL450, EBECRYL657, EBECRYL885, EBECRYL800, EBECRYL3416, and EBECRYL860 (all manufactured by Daicel Allnex Corporation), but are not limited thereto.

[0232] From the viewpoint of improving chemical resistance, printing durability, and suppression of on-press development residue, the content of the oligomer is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass, relative to the total mass of the polymerizable compounds in the image recording layer.

[0233] The polymerizable compound may further contain a polymerizable compound other than the oligomer. From the viewpoint of chemical resistance, the polymerizable compound other than the oligomer is preferably a low-molecular-weight polymerizable compound. The low-molecular-weight polymerizable compound may be in a chemical form such as a monomer, a dimer, a trimer, or a mixture thereof. From the viewpoint of chemical resistance, the low-molecular-weight polymerizable compound is preferably at least one polymerizable compound selected from the group consisting of polymerizable compounds having three or more ethylenically unsaturated groups and polymerizable compounds having an isocyanuric ring structure.

[0234] In the present disclosure, a low-molecular-weight polymerizable compound refers to a polymerizable compound having a molecular weight (weight-average molecular weight when the compound has a molecular weight distribution) of 50 or more and less than 600. From the viewpoint of achieving excellent chemical resistance, printing durability, and on-press development residue suppression, the molecular weight of the low-molecular-weight polymerizable compound is preferably 100 or more and less than 600, more preferably 300 or more and less than 600, and even more preferably 400 or more and less than 600.

[0235] When the polymerizable compound contains a low-molecular-weight polymerizable compound as a polymerizable compound other than an oligomer (when two or more types of low-molecular-weight polymerizable compounds are contained, the total amount of the low-molecular-weight polymerizable compounds), from the viewpoints of chemical resistance, printing durability, and suppression of on-press development residue, the ratio of the oligomer to the low-molecular-weight polymerizable compound (oligomer / low-molecular-weight polymerizable compound) is preferably 10 / 1 to 1 / 10, more preferably 10 / 1 to 3 / 7, and even more preferably 10 / 1 to 7 / 3, by mass.

[0236] In addition, as the low molecular weight polymerizable compound, the polymerizable compounds described in paragraphs 0082 to 0086 of WO 2019 / 013268 can also be suitably used.

[0237] The details of the method of use, such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount added, can be set as desired. In particular, from the viewpoint of printing durability, it is preferable that the image recording layer contains two or more types of polymerizable compounds. The content of the polymerizable compounds (when two or more types of polymerizable compounds are contained, the total content of the polymerizable compounds) is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 70% by mass, and even more preferably 15% by mass to 60% by mass, relative to the total mass of the image recording layer.

[0238] <Particles> The image recording layer preferably contains particles. The particles may be organic particles or inorganic particles, but from the viewpoint of printing durability, it is preferable to contain organic particles, and it is more preferable to contain polymer particles. As the inorganic particles, known inorganic particles can be used, and metal oxide particles such as silica particles and titania particles can be preferably used.

[0239] The polymer particles are preferably selected from the group consisting of thermoplastic resin particles, thermoreactive resin particles, polymer particles having polymerizable groups, microcapsules encapsulating hydrophobic compounds, and microgels (crosslinked polymer particles). Among these, polymer particles or microgels having polymerizable groups are preferred. In a particularly preferred embodiment, the polymer particles contain at least one ethylenically unsaturated polymerizable group. The presence of such polymer particles enhances the printing durability of exposed areas and the on-press developability of unexposed areas. Furthermore, from the viewpoints of printing durability and on-press developability, the polymer particles are preferably thermoplastic resin particles.

[0240] Preferred examples of thermoplastic resin particles include thermoplastic polymer particles 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 thermoplastic resin 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, as well as mixtures thereof. Preferred examples include copolymers containing polystyrene, styrene, and acrylonitrile, or polymethyl methacrylate. The average particle size of the thermoplastic resin particles is preferably 0.01 μm to 3.0 μm.

[0241] The thermoreactive resin particles include polymer particles having thermoreactive groups, which form hydrophobic regions due to crosslinking caused by a thermal reaction and the resulting change in functional groups.

[0242] The thermally reactive group in the polymer particles having a thermally reactive group may be any functional group that undergoes any reaction as long as a chemical bond is formed, but is preferably a polymerizable group, and preferred examples thereof include ethylenically unsaturated groups that undergo radical polymerization reactions (e.g., acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, etc.), cationically polymerizable groups (e.g., vinyl groups, vinyloxy groups, epoxy groups, oxetanyl groups, etc.), isocyanato groups or their block products that undergo addition reactions, epoxy groups, vinyloxy groups, and functional groups having active hydrogen atoms that are their reaction partners (e.g., amino groups, hydroxy groups, carboxy groups, etc.), carboxy groups that undergo condensation reactions, and their reaction partners, hydroxy groups or amino groups, and acid anhydrides that undergo ring-opening addition reactions, and their reaction partners, amino groups or hydroxy groups.

[0243] As for the microcapsules, as described in, for example, JP-A Nos. 2001-277740 and 2001-277742, at least some of the components of the image recording layer are encapsulated in the microcapsules. The components of the image recording layer can also be contained outside the microcapsules. In a preferred embodiment, the image recording layer containing microcapsules has a hydrophobic component encapsulated in the microcapsules and a hydrophilic component contained outside the microcapsules.

[0244] The microgel (crosslinked polymer particle) can contain a part of the components of the image recording layer on at least one of its surface and interior. In particular, a reactive microgel having a radically polymerizable group on its surface is preferred from the viewpoints of the sensitivity of the resulting lithographic printing plate precursor and the printing durability of the resulting lithographic printing plate.

[0245] Known methods can be used to microencapsulate or microgel the components of the image recording layer.

[0246] Furthermore, from the viewpoint of the printing durability, stain resistance, and storage stability of the resulting lithographic printing plate, the polymer particles are preferably those obtained by reacting a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in its molecule with isophorone diisocyanate, with a compound having active hydrogen. The polyphenol compound is preferably a compound having multiple benzene rings each having a phenolic hydroxy group. The compound having active hydrogen is preferably a polyol compound or a polyamine compound, more preferably a polyol compound, and even more preferably at least one compound selected from the group consisting of propylene glycol, glycerin, and trimethylolpropane. Examples of resin particles obtained by reacting a polyisocyanate compound, which is an adduct of a polyphenol compound having two or more hydroxy groups in its molecule with isophorone diisocyanate, with a compound having active hydrogen include the polymer particles described in paragraphs

[0032] to

[0095] of JP-A-2012-206495.

[0247] Furthermore, from the viewpoint of the printing durability and solvent resistance of the resulting lithographic printing plate, the polymer particles preferably have a hydrophobic main chain and include both i) a constituent unit having a pendant cyano group directly bonded to the hydrophobic main chain, and ii) a constituent unit having a pendant group containing a hydrophilic polyalkylene oxide segment. A preferred example of the hydrophobic main chain is 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 polyalkylene oxide segment is preferably ethylene oxide or propylene oxide, and more preferably ethylene oxide. The number of repeating alkylene oxide structures in the hydrophilic polyalkylene 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 polyalkylene oxide segment include those described in paragraphs 0039 to 0068 of JP-T-2008-503365.

[0248] Further, from the viewpoints of printing durability and on-press developability, the polymer particles preferably have a hydrophilic group. The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxy group, a hydroxy group, an amino group, a cyano group, and a polyalkylene oxide structure. Among these, from the viewpoints of on-press developability and printing durability, a polyalkylene oxide structure is preferred, and a polyethylene oxide structure, a polypropylene oxide structure, or a polyethylene / propylene oxide structure is more preferred. Further, from the viewpoints of on-press developability and suppression of development residue during on-press development, the polyalkylene oxide structure preferably has a polypropylene oxide structure, and more preferably has a polyethylene oxide structure or a polypropylene oxide structure. Further, from the viewpoints of printing durability, ink receptivity, and on-press developability, the hydrophilic group preferably contains a structural unit having a cyano group or a group represented by the following formula Z, more preferably contains a structural unit represented by the following formula (AN) or a group represented by the following formula Z, and particularly preferably contains a group represented by the following formula Z: *-Q-W-Y Formula Z In Formula Z, Q represents a divalent linking group, W represents a divalent group having a hydrophilic structure or a divalent group having a hydrophobic structure, Y represents a monovalent group having a hydrophilic structure or a monovalent group having a hydrophobic structure, either W or Y has a hydrophilic structure, and * represents a bonding site with another structure.

[0249]

[0250] In formula (AN), R ＡＮ represents a hydrogen atom or a methyl group.

[0251] From the viewpoint of printing durability, the polymer contained in the polymer particles preferably contains a structural unit formed by a compound having a cyano group. The cyano group is typically introduced into the resin as a structural unit containing a cyano group using a compound (monomer) having a cyano group. Examples of compounds having a cyano group include acrylonitrile compounds, with (meth)acrylonitrile being preferred. The structural unit containing a cyano group is preferably a structural unit formed by an acrylonitrile compound, and more preferably a structural unit formed by (meth)acrylonitrile, i.e., a structural unit represented by the above formula (AN). When the polymer contains a polymer having a structural unit containing a cyano group, the content of the structural unit containing a cyano group, preferably the structural unit represented by the above formula (AN), in the polymer having the structural unit containing a cyano group is preferably 5% to 90% by mass, more preferably 20% to 80% by mass, and particularly preferably 30% to 60% by mass, relative to the total mass of the polymer having the structural unit containing a cyano group.

[0252] Furthermore, from the viewpoints of printing durability, ink receptivity, and on-press developability, the polymer particles preferably contain polymer particles having a group represented by the formula Z above.

[0253] Q in the above formula Z is preferably a divalent linking group having 1 to 20 carbon atoms, and more preferably a divalent linking group having 1 to 10 carbon atoms. Furthermore, Q in the above formula Z is preferably an alkylene group, an arylene group, an ester bond, an amide bond, or a group consisting of a combination of two or more of these, and more preferably a phenylene group, an ester bond, or an amide bond.

[0254] The divalent group having a hydrophilic structure in W of the above formula Z is a polyalkyleneoxy group or a polyalkyleneoxy group having —CH ２ CH ２ NR Ｗ It is preferable that R Ｗ represents a hydrogen atom or an alkyl group. The divalent group having a hydrophobic structure represented by W in the above formula Z is -RＷＡ -, -O-R ＷＡ -O-, -R Ｗ N-R ＷＡ -NR Ｗ -, -OC(=O)-R ＷＡ —O— or —OC(═O)—R ＷＡ It is preferable that R is —O—. ＷＡ each independently represents a linear, branched, or cyclic alkylene group having 6 to 120 carbon atoms, a haloalkylene group having 6 to 120 carbon atoms, an arylene group having 6 to 120 carbon atoms, an alkylylene group having 6 to 120 carbon atoms (a divalent group obtained by removing one hydrogen atom from an alkylaryl group), or an aralkylene group having 6 to 120 carbon atoms.

[0255] The monovalent group having a hydrophilic structure in Y of the above formula Z is -OH, -C(=O)OH, a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the end, or a polyalkyleneoxy group having a hydrogen atom or an alkyl group at the other end and -CH ２ CH ２ N (R Ｗ The monovalent group having a hydrophobic structure represented by Y in the above formula Z is preferably a linear, branched or cyclic alkyl group having 6 to 120 carbon atoms, a haloalkyl group having 6 to 120 carbon atoms, an aryl group having 6 to 120 carbon atoms, an alkaryl group (alkylaryl group) having 7 to 120 carbon atoms, an aralkyl group having 7 to 120 carbon atoms, -OR ＷＢ , -C(=O)OR ＷＢ , or —OC(═O)R ＷＢ It is preferable that R ＷＢ represents an alkyl group having 6 to 20 carbon atoms.

[0256] In terms of printing durability, ink receptivity, and on-press developability, it is more preferable that the polymer particles having a group represented by the above formula Z are such that W is a divalent group having a hydrophilic structure, Q is a phenylene group, an ester bond, or an amide bond, W is a polyalkyleneoxy group, and Y is a polyalkyleneoxy group whose terminal is a hydrogen atom or an alkyl group.

[0257] Furthermore, from the viewpoints of printing durability and on-press developability, the polymer particles preferably contain polymer particles having a polymerizable group, and more preferably contain polymer particles having a polymerizable group on the particle surface. Furthermore, from the viewpoint of printing durability, the polymer particles preferably contain polymer particles having a hydrophilic group and a polymerizable group. The polymerizable group may be a cationically polymerizable group or a radically polymerizable group, but from the viewpoint of reactivity, a radically polymerizable group is preferable. The polymerizable group is not particularly limited as long as it is a polymerizable group, but from the viewpoint of reactivity, an ethylenically unsaturated group is preferable, a vinylphenyl group (styryl group), a (meth)acryloxy group, or a (meth)acrylamide group is more preferable, and a (meth)acryloxy group is particularly preferable. Furthermore, the polymer in the polymer particles having a polymerizable group preferably has a structural unit having a polymerizable group. Furthermore, a polymerizable group may be introduced onto the surface of the polymer particle by a polymer reaction.

[0258]

[0033] Furthermore, from the viewpoints of printing durability and on-press developability, the image recording layer preferably contains addition polymerization resin particles having a dispersible group as the polymer particles, and it is more preferable that the dispersible group contains a group represented by the above formula Z.

[0259] Furthermore, from the viewpoints of printing durability, ink receptivity, on-press developability, and suppression of development residue during on-press development, the polymer particles preferably contain a resin having a urea bond, more preferably contain a resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water, and particularly preferably contain a resin having a structure obtained by at least reacting an isocyanate compound represented by the following formula (Iso) with water, and having a polyethylene oxide structure and a polypropylene oxide structure as the polyoxyalkylene structure. Furthermore, the particles containing the resin having a urea bond are preferably microgels.

[0260]

[0261] In formula (Iso), n represents an integer of 0 to 10.

[0262] An example of a reaction between an isocyanate compound represented by the above formula (Iso) and water is the reaction shown below. Note that the following example uses the 4,4-isomer, where n = 0. As shown below, when an isocyanate compound represented by the above formula (Iso) is reacted with water, some of the isocyanate groups are hydrolyzed by the water to generate amino groups. The resulting amino groups then react with the isocyanate groups to form urea bonds and a dimer. Furthermore, the following reaction is repeated to form a resin having a urea bond. Furthermore, by adding a compound (a compound having active hydrogen) reactive with isocyanate groups, such as an alcohol compound or an amine compound, to the following reaction, the structure of the alcohol compound, amine compound, or the like can be introduced into the resin having a urea bond. Preferred examples of the compound having active hydrogen include those described above for the microgel.

[0263]

[0264] The resin having a urea bond preferably has an ethylenically unsaturated group, and more preferably has a group represented by the following formula (PETA).

[0265]

[0266] In formula (PETA), the wavy line portion represents the bonding position to other structures.

[0267] Furthermore, from the viewpoints of printing durability and on-press developability, the image recording layer preferably contains thermoplastic resin particles. The thermoplastic resin contained in the thermoplastic resin particles is not particularly limited, and examples thereof include polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polymethyl (meth)acrylate, polyethyl (meth)acrylate, polybutyl (meth)acrylate, polyacrylonitrile, polyvinyl acetate, and copolymers thereof. The thermoplastic resin may be in a latex state. The thermoplastic resin according to the present disclosure is preferably a resin that forms part or all of the hydrophobic film that forms the recording layer by melting or softening the thermoplastic resin due to heat generated in the exposure step described below.

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

[0269] Resin A contained in the thermoplastic resin preferably has a structural unit formed by an aromatic vinyl compound. Examples of aromatic vinyl compounds include compounds having a structure in which a vinyl group is bonded to an aromatic ring. Examples of aromatic vinyl compounds include styrene compounds and vinylnaphthalene compounds, with styrene being preferred and styrene being more preferred. Examples of styrene compounds include styrene, p-methylstyrene, p-methoxystyrene, β-methylstyrene, p-methyl-β-methylstyrene, α-methylstyrene, and p-methoxy-β-methylstyrene, with styrene being preferred. Examples of vinylnaphthalene compounds include 1-vinylnaphthalene, methyl-1-vinylnaphthalene, β-methyl-1-vinylnaphthalene, 4-methyl-1-vinylnaphthalene, 4-methoxy-1-vinylnaphthalene, with 1-vinylnaphthalene being preferred.

[0270] Furthermore, preferred examples of the structural unit formed from an aromatic vinyl compound include a structural unit represented by the following formula A1.

[0271]

[0272] In formula A1, R Ａ１ and R Ａ２ each independently represents a hydrogen atom or an alkyl group, Ar represents an aromatic ring group, R Ａ３ represents a substituent, and n represents an integer of 0 or more and not more than the maximum number of substituents on Ar. Ａ１ and R Ａ２ are each independently preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom. In Formula A1, Ar is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring. In Formula A1, R Ａ３is preferably an alkyl group or an alkoxy group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, and even more preferably a methyl group or a methoxy group. Ａ３ If there are multiple R Ａ３ In formula A1, n is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0273] In Resin A contained in the thermoplastic resin, the content of the structural unit formed by the aromatic vinyl compound is preferably greater than the content of the structural unit having a cyano group, which will be described later, from the viewpoint of ink receptivity, and is more preferably 15% by mass to 85% by mass, and even more preferably 30% by mass to 70% by mass, relative to the total mass of the thermoplastic resin.

[0274] The resin A contained in the thermoplastic resin particles preferably contains a structural unit having a cyano group. The cyano group is usually preferably introduced into the resin A as a structural unit containing a cyano group using a compound (monomer) having a cyano group. Examples of the compound having a cyano group include an acrylonitrile compound, and (meth)acrylonitrile is preferred. The structural unit having a cyano group is preferably a structural unit formed by an acrylonitrile compound, and more preferably a structural unit formed by (meth)acrylonitrile.

[0275] Furthermore, preferred examples of the structural unit formed by a compound having a cyano group include a structural unit represented by the following formula B1.

[0276]

[0277] In formula B1, R Ｂ１ represents a hydrogen atom or an alkyl group. Ｂ１ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0278] From the viewpoint of ink receptivity, the content of the structural unit having a cyano group in Resin A is preferably smaller than the content of the structural unit formed from the aromatic vinyl compound, and is more preferably 55% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, relative to the total mass of Resin A.

[0279] Furthermore, when resin A contained in the thermoplastic resin contains a structural unit formed from an aromatic vinyl compound and a structural unit having a cyano group, the content ratio of the structural unit formed from the aromatic vinyl compound to the structural unit having a cyano group (structural unit formed from the aromatic vinyl compound:structural unit having a cyano group) is preferably 5:5 to 9:1, and more preferably 6:4 to 8:2, on a mass basis.

[0280] From the viewpoints of printing durability and chemical resistance, it is preferable that the resin A contained in the thermoplastic resin particles further contains a structural unit formed by an N-vinyl heterocyclic compound. Examples of the N-vinyl heterocyclic compound include N-vinylpyrrolidone, N-vinylcarbazole, N-vinylpyrrole, N-vinylphenothiazine, N-vinylsuccinimide, N-vinylphthalimide, N-vinylcaprolactam, and N-vinylimidazole, with N-vinylpyrrolidone being preferred.

[0281] Furthermore, preferred examples of the structural unit formed by the N-vinyl heterocyclic compound include a structural unit represented by the following formula C1:

[0282]

[0283] In formula C1, Ar Ｎ represents a heterocyclic structure containing a nitrogen atom, and Ar Ｎ The nitrogen atom in the formula C1 is bonded to the carbon atom marked with *. Ｎ The heterocyclic structure represented by the formula (I) is preferably a pyrrolidone ring, a carbazole ring, a pyrrole ring, a phenothiazine ring, a succinimide ring, a phthalimide ring, a caprolactam ring, or an imidazole ring, and more preferably a pyrrolidone ring. Ｎ The heterocyclic structure represented by the formula: may have a known substituent.

[0284] The content of the structural unit formed by the N-vinyl heterocyclic compound in Resin A is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 40% by mass, relative to the total mass of Resin A.

[0285] The resin A contained in the thermoplastic resin particles may contain a structural unit having an acidic group, but from the viewpoint of on-press developability and ink receptivity, it is preferable that the resin A does not contain a structural unit having an acidic group. Specifically, the content of the structural unit having an acidic group in the thermoplastic resin is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The lower limit of the content is not particularly limited and may be 0% by mass. Furthermore, the acid value of the thermoplastic resin is preferably 160 mg KOH / g or less, more preferably 80 mg KOH / g or less, and even more preferably 40 mg KOH / g or less. The lower limit of the acid value is not particularly limited and may be 0 mg KOH / g. In the present disclosure, the acid value is determined by a measurement method in accordance with JIS K0070:1992.

[0286] From the viewpoint of ink receptivity, the resin A contained in the thermoplastic resin particles may contain a structural unit containing a hydrophobic group. Examples of the hydrophobic group include an alkyl group, an aryl group, and an aralkyl group. The structural unit containing a hydrophobic group is preferably a structural unit formed from an alkyl (meth)acrylate compound, an aryl (meth)acrylate compound, or an aralkyl (meth)acrylate compound, and more preferably a structural unit formed from an alkyl (meth)acrylate compound. The alkyl group in the alkyl (meth)acrylate compound preferably has 1 to 10 carbon atoms. The alkyl group may be linear or branched, or may have a cyclic structure. Examples of the alkyl (meth)acrylate compound include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. The number of carbon atoms in the aryl group in the aryl (meth)acrylate compound is preferably 6 to 20, and more preferably a phenyl group. The aryl group may have a known substituent. A preferred example of the aryl (meth)acrylate compound is phenyl (meth)acrylate. The number of carbon atoms in the alkyl group in the aralkyl (meth)acrylate compound is preferably 1 to 10. The alkyl group may be linear or branched, or may have a cyclic structure. The number of carbon atoms in the aryl group in the aralkyl (meth)acrylate compound is preferably 6 to 20, and more preferably a phenyl group. A preferred example of the aralkyl (meth)acrylate compound is benzyl (meth)acrylate.

[0287] The content of the structural unit having a hydrophobic group in the resin A contained in the thermoplastic resin particles is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the resin A.

[0288] The thermoplastic resin contained in the thermoplastic resin particles preferably has a hydrophilic group from the viewpoint of printing durability and on-press developability.The hydrophilic group is not particularly limited as long as it has a hydrophilic structure, and examples thereof include an acid group such as a carboxy group, a hydroxy group, an amino group, a cyano group, and a polyalkylene oxide structure.From the viewpoint of printing durability and on-press developability, the hydrophilic group is preferably a group having a polyalkylene oxide structure, a group having a polyester structure, or a sulfonic acid group, more preferably a group having a polyalkylene oxide structure or a sulfonic acid group, and even more preferably a group having a polyalkylene oxide structure.

[0289] From the viewpoint of on-press developability, the polyalkylene oxide structure is preferably a polyethylene oxide structure, a polypropylene oxide structure, or a poly(ethylene oxide / propylene oxide) structure. Furthermore, from the viewpoint of on-press developability, the polyalkylene oxide structure among the hydrophilic groups is preferably a polypropylene oxide structure, and more preferably a polyethylene oxide structure or a polypropylene oxide structure. From the viewpoint of on-press developability, the number of alkylene oxide structures in the polyalkylene oxide structure is preferably 2 or more, more preferably 5 or more, even more preferably 5 to 200, and particularly preferably 8 to 150.

[0290] From the viewpoint of on-press developability, the hydrophilic group is preferably a group represented by the formula Z.

[0291] From the viewpoint of improving printing durability, chemical resistance, and on-press developability, the resin A contained in the thermoplastic resin particles preferably contains a structural unit having a hydrophilic group. Examples of the hydrophilic group include —OH, —CN, —CONR １ R ２ , -NR ２ COR １ (R １ and R ２ R each independently represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group. １ and R ２may be bonded to form a ring. ３ R ４ , -N ＋ R ３ R ４ R ５ X － (R ３ ~R ５ each independently represents an alkyl group having 1 to 8 carbon atoms; X － represents a counter anion), a group represented by the following formula PO, and a hydrophilic group preferably contained in the thermoplastic resin contained in the thermoplastic resin particles. １ R ２ or a group represented by the formula PO is preferred, and a group represented by the formula PO is more preferred.

[0292]

[0293] In the formula PO, L Ｐ each independently represents an alkylene group; R Ｐ represents a hydrogen atom or an alkyl group, and n represents an integer of 1 to 100. Ｐ are each independently preferably an ethylene group, a 1-methylethylene group or a 2-methylethylene group, more preferably an ethylene group. Ｐ is preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, still more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom or a methyl group. In formula PO, n is preferably an integer of 1 to 10, more preferably an integer of 1 to 4.

[0294] The content of the structural unit having a hydrophilic group in the resin A is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the resin A.

[0295] The resin A contained in the thermoplastic resin particles may further contain other structural units. The other structural units may contain structural units other than the above-mentioned structural units without any particular limitation, and examples thereof include structural units formed by an acrylamide compound, a vinyl ether compound, etc. Examples of acrylamide compounds include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-butyl(meth)acrylamide, N,N'-dimethyl(meth)acrylamide, N,N'-diethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-hydroxypropyl(meth)acrylamide, and N-hydroxybutyl(meth)acrylamide. Examples of vinyl ether compounds include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, and phenoxypolyethylene glycol vinyl ether.

[0296] The content of other structural units in the thermoplastic resin is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass, relative to the total mass of the thermoplastic resin.

[0297] From the viewpoints of printing durability and ink receptivity, the glass transition temperature (Tg) of the thermoplastic resin is preferably 60° C. to 150° C., more preferably 80° C. to 140° C., and even more preferably 90° C. to 130° C. When the thermoplastic resin particles contain two or more thermoplastic resins, the value determined by the FOX equation described below is referred to as the glass transition temperature of the thermoplastic resin.

[0298] In the present disclosure, the glass transition temperature of a resin can be measured using differential scanning calorimetry (DSC). A specific measurement method is performed in accordance with the method described in JIS K 7121 (1987) or JIS K 6240 (2011). The glass transition temperature used herein is the extrapolated glass transition onset temperature (hereinafter sometimes referred to as Tig). The method for measuring the glass transition temperature will be described in more detail below. To determine the glass transition temperature, the resin is held at a temperature approximately 50°C lower than the expected Tg of the resin until the apparatus stabilizes, and then heated at a heating rate of 20°C / min to a temperature approximately 30°C higher than the temperature at which the glass transition ends, and a differential thermal analysis (DTA) curve or a DSC curve is created. The extrapolated glass transition onset temperature (Tig), i.e., the glass transition temperature Tg in this specification, is determined as the temperature at the intersection of a straight line extending the low-temperature baseline of a DTA curve or a DSC curve toward a higher temperature and a tangent drawn at the point where the gradient of the curve in the stepwise change portion of the glass transition is maximum.

[0299] When the thermoplastic resin particles contain two types of thermoplastic resins, the Tg of the thermoplastic resin contained in the thermoplastic resin particles can be calculated as follows: When the Tg of the first thermoplastic resin is Tg1(K), the mass fraction of the first thermoplastic resin relative to the total mass of the thermoplastic resin components in the thermoplastic resin particles is W1, the Tg of the second thermoplastic resin is Tg2(K), and the mass fraction of the second resin relative to the total mass of the thermoplastic resin components in the thermoplastic resin particles is W2, the Tg0(K) of the thermoplastic resin particles can be estimated according to the following FOX formula: FOX formula: 1 / Tg0=(W1 / Tg1)+(W2 / Tg2) Furthermore, when the thermoplastic resin particles contain three or more types of resins, or when three or more types of thermoplastic resin particles containing different types of thermoplastic resins are contained in the pretreatment liquid, the Tg0(K) of the thermoplastic resin particles can be estimated according to the following formula, similar to the above, when the Tg of the nth resin is Tgn(K) and the mass fraction of the nth resin relative to the total mass of the resin components in the thermoplastic resin particles is Wn. FOX formula: 1 / Tg0=(W1 / Tg1)+(W2 / Tg2)+(W3 / Tg3)...+(Wn / Tgn)

[0300] In the present disclosure, Tg is a value measured by a differential scanning calorimetry (DSC). As the differential scanning calorimeter (DSC), for example, an EXSTAR6220 manufactured by SII NanoTechnology, Inc. can be used.

[0301] From the viewpoint of printing durability, the arithmetic mean particle size of the thermoplastic resin particles is preferably 1 nm or more and 200 nm or less, more preferably 3 nm or more and less than 80 nm, and even more preferably 10 nm or more and 49 nm or less.

[0302] The arithmetic mean particle size of thermoplastic resin particles in the present disclosure refers to a value measured by dynamic light scattering (DLS) unless otherwise specified. The arithmetic mean particle size of thermoplastic resin particles by DLS is measured using a Brookhaven BI-90 (manufactured by Brookhaven Instrument Company) according to the manual for the instrument.

[0303] The weight average molecular weight of the thermoplastic resin contained in the thermoplastic resin particles is preferably 3,000 to 300,000, and more preferably 5,000 to 100,000.

[0304] The thermoplastic resin contained in the thermoplastic resin particles can be produced by any known method, without any particular limitation. For example, the thermoplastic resin can be obtained by polymerizing, by a known method, a styrene compound, an acrylonitrile compound, and, if necessary, at least one compound selected from the group consisting of the N-vinyl heterocyclic compound, the compound used to form the structural unit having an ethylenically unsaturated group, the compound used to form the structural unit having an acidic group, the compound used to form the structural unit having a hydrophobic group, and the compound used to form the other structural unit.

[0305] Specific examples of the thermoplastic resin contained in the thermoplastic resin particles are shown in the table below, but the thermoplastic resin used in the present disclosure is not limited to these.

[0306]

[0307]

[0308] In the above specific examples, the content ratio of each structural unit can be appropriately changed in accordance with the preferred range of the content of each structural unit described above. In addition, the weight average molecular weight of each compound shown in the above specific examples can be appropriately changed in accordance with the preferred range of the weight average molecular weight of the thermoplastic resin described above.

[0309] The average particle size of the particles is preferably 0.01 μm to 3.0 μm, more preferably 0.03 μm to 2.0 μm, and even more preferably 0.10 μm to 1.0 μm. Within this range, good resolution and stability over time can be obtained. The average primary particle size of the particles in this disclosure is measured by a light scattering method, or by taking an electron microscope photograph of the particles, measuring the particle sizes of a total of 5,000 particles on the photograph, and calculating the average value. For non-spherical particles, the particle size is taken to be the particle size of a spherical particle having the same particle area as the particle area on the photograph. Furthermore, the average particle size in this disclosure is taken to be the volume-average particle size, unless otherwise specified.

[0310] The image recording layer may contain one type of particle, particularly polymer particles, or two or more types. From the viewpoints of on-press developability and printing durability, the content of the particles, particularly polymer particles, in the image recording layer is preferably 5% to 90% by mass, more preferably 10% to 90% by mass, even more preferably 20% to 90% by mass, and particularly preferably 50% to 90% by mass, relative to the total mass of the image recording layer. From the viewpoints of on-press developability and printing durability, the content of the polymer particles in the image recording layer is preferably 20% to 100% by mass, more preferably 35% to 100% by mass, even more preferably 50% to 100% by mass, and particularly preferably 80% to 100% by mass, relative to the total mass of components of the image recording layer having a molecular weight of 3,000 or more.

[0311] <Binder polymer> The image recording layer may contain a binder polymer. As the binder polymer, a binder polymer used in the image recording layer of an on-press development type lithographic printing plate precursor can be used. Specifically, as the binder polymer, the binder polymers described in paragraphs 0288 to 0317 of WO 2022 / 019217 can be suitably used.

[0312] In the image recording layer, one type of binder polymer may be used alone, or two or more types may be used in combination. The binder polymer may be contained in the image recording layer in any amount, but the content of the binder polymer is preferably 1% by mass to 90% by mass, and more preferably 5% by mass to 80% by mass, relative to the total mass of the image recording layer. Furthermore, when the image recording layer of the present disclosure contains another binder polymer, the content of the other binder polymer relative to the total mass of the thermoplastic resin particles and the other binder polymer is preferably more than 0% by mass and 99% by mass or less, more preferably 20% by mass to 95% by mass, and even more preferably 40% by mass to 90% by mass.

[0313] <Oil Agent> The image recording layer preferably contains an oil agent. In the present disclosure, the oil agent refers to a hydrophobic compound that is liquid at 80°C and separates when mixed with an equal mass of water without being miscible. When two or more oil agents are used, even if a compound with a melting point of 80°C or higher is included, it is sufficient that the two or more oil agents are in a liquid state at 80°C when mixed. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, the oil agent is preferably a compound with a molecular weight of less than 1,000, more preferably a compound with a molecular weight of 200 to 800, and particularly preferably a compound with a molecular weight of 300 to 500. Furthermore, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, the oil agent is preferably a compound with a boiling point at 1 atmosphere of 200°C or higher, more preferably a compound with a boiling point at 1 atmosphere of 250°C or higher, even more preferably a compound with a boiling point at 1 atmosphere of 300°C or higher, and particularly preferably a compound with a boiling point at 1 atmosphere of 400°C or higher and 500°C or lower. In the present disclosure, unless otherwise specified, the term "boiling point" refers to the boiling point at 1 atmosphere. From the viewpoints of on-press developability and suppression of turbidity in the dampening water, the melting point of the oil agent at 1 atmosphere is preferably 50°C or lower, more preferably 30°C or lower, and particularly preferably -200°C or higher and 25°C or lower. In the present disclosure, unless otherwise specified, the term "melting point" refers to the melting point at 1 atmosphere.

[0314] Examples of oil agents include phosphate ester compounds, aromatic hydrocarbon compounds, glyceride compounds, fatty acid compounds, aromatic ester compounds, etc. Among these, from the viewpoints of printing durability, ink receptivity, on-press developability, and suppression of turbidity in the dampening water, at least one compound selected from the group consisting of phosphate ester compounds, aromatic hydrocarbon compounds, glyceride compounds, and aromatic ester compounds is preferred, at least one compound selected from the group consisting of phosphate ester compounds, aromatic hydrocarbon compounds, and glyceride compounds is more preferred, at least one compound selected from the group consisting of phosphate ester compounds and aromatic hydrocarbon compounds is even more preferred, and a phosphate ester compound is particularly preferred.

[0315] As the phosphate ester compound, from the viewpoints of printing durability, ink receptivity, on-press developability, and suppression of fountain solution clouding, a phosphate triester compound is preferred, a triaryl phosphate ester compound is more preferred, tricresyl phosphate is even more preferred, and a mixture of two or more of the ortho-, meta-, and para-tricresyl phosphate isomers is particularly preferred. As the aromatic hydrocarbon compound, from the viewpoints of on-press developability and suppression of fountain solution clouding, a compound having two or more aromatic rings is preferred, and a compound having two or more non-fused benzene rings is more preferred. As the glyceride compound, from the viewpoints of on-press developability and suppression of fountain solution clouding, a triglyceride compound is preferred, a fatty oil is more preferred, and a fatty oil that is liquid at 25°C, such as castor oil, is particularly preferred. As the fatty acid compound, from the viewpoints of on-press developability and suppression of fountain solution clouding, an unsaturated fatty acid is preferred, an unsaturated fatty acid having 8 to 30 carbon atoms is more preferred, and an unsaturated fatty acid having 12 to 24 carbon atoms is particularly preferred. As the aromatic ester compound, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, an aromatic diester compound is preferred, and an aromatic diester compound having an aliphatic ring is more preferred. As the aliphatic ester compound, from the viewpoints of on-press developability and suppression of turbidity of the fountain solution, an aliphatic ester compound having a branched alkyl group is preferred, and an aliphatic ester compound having a branched alkyl group and having 10 to 24 carbon atoms is more preferred.

[0316] From the viewpoints of printing durability, ink receptivity, on-press developability, and dampening water turbidity suppression, the oil agent preferably contains an oil agent having a phosphorus atom, and more preferably an oil agent having a phosphorus atom. Also, from the viewpoints of on-press developability and dampening water turbidity suppression, the oil agent preferably contains an oil agent having an aromatic ring, more preferably contains an oil agent having two or more aromatic rings, and particularly preferably contains an oil agent having two or more non-condensed benzene rings.

[0317] From the viewpoints of printing durability, ink receptivity, on-press developability, and dampening water turbidity suppression, the clogP value of the oil agent is preferably 5.0 or more, more preferably 5.50 or more, even more preferably 5.50 or more and 10.0 or less, and particularly preferably 5.60 or more and 7.00 or less. The clogP value is a value obtained by calculating the common logarithm logP of the partition coefficient P between 1-octanol and water. Known methods and software can be used to calculate the clogP value, but unless otherwise specified, the present disclosure will use the ClogP program incorporated into Cambridgesoft's ChemBioDraw Ultra 12.0.

[0318] Specific examples of oil agents include tricresyl phosphate, dimethyl(1-phenylethyl)benzene, 2,4-diphenyl-4-methyl-1-pentene, dicyclohexyl phthalate, castor oil, α-linolenic acid, and tri(2-ethylhexyl) phosphate.

[0319] Although only one oil agent may be used or two or more oil agents may be used in combination, from the viewpoints of on-press developability and suppression of turbidity of the dampening water, it is preferable that the image recording layer contains two or more oil agents having different structures. The content of the oil agent is preferably 0.0001% by mass to 10.0% by mass, more preferably 0.0002% by mass to 1.0% by mass, still more preferably 0.0005% by mass to 0.5% by mass, and particularly preferably 0.001% by mass to 0.05% by mass, relative to the total mass of the image recording layer.

[0320] <Chain Transfer Agent> The image recording layer may contain a chain transfer agent. As the chain transfer agent, a chain transfer agent used in the image recording layer of an on-press development type lithographic printing plate precursor can be used. Specifically, as the chain transfer agent, the chain transfer agents described in paragraphs 0388 to 0393 of WO 2022 / 019217 can be suitably used.

[0321] The content of the chain transfer agent is preferably 0.01% by mass to 50% by mass, more preferably 0.05% by mass to 40% by mass, and even more preferably 0.1% by mass to 30% by mass, based on the total mass of the image recording layer.

[0322] <Oil-sensitizing agent> The image recording layer may contain an oil-sensitizing agent to improve ink receptivity. As the oil-sensitizing agent, an oil-sensitizing agent used in the image recording layer of an on-press development type lithographic printing plate precursor can be used. Specifically, as the oil-sensitizing agent, the oil-sensitizing agents described in paragraphs 0395 to 0404 of WO 2022 / 019217 can be suitably used.

[0323] The content of the oil sensitizer is preferably from 1 to 40.0% by mass, more preferably from 2 to 25.0% by mass, and even more preferably from 3 to 20.0% by mass, based on the total mass of the image recording layer.

[0324] The image recording layer may contain one oil-sensitizing agent alone, or two or more may be used in combination. One preferred embodiment of the image recording layer used in the present disclosure is an embodiment containing two or more compounds as the oil-sensitizing agent. Specifically, from the viewpoint of achieving both on-press developability and ink-receptivity, the image recording layer used in the present disclosure preferably uses a phosphonium compound, a nitrogen-containing low-molecular-weight compound, and an ammonium group-containing polymer in combination as the oil-sensitizing agent, and more preferably uses a phosphonium compound, a quaternary ammonium salt, and an ammonium group-containing polymer in combination.

[0325] <Development Accelerator> The image recording layer preferably further contains a development accelerator, the polarity term of which SP value is preferably from 6.0 to 26.0, more preferably from 6.2 to 24.0, still more preferably from 6.3 to 23.5, and particularly preferably from 6.4 to 22.0.

[0326] The SP value (solubility parameter, unit: (cal / cm ３ ) １／２The value of the polar term in the Hansen solubility parameter is the value of the polar term δp in the Hansen solubility parameter. The Hansen solubility parameter is a solubility parameter introduced by Hildebrand, which is divided into three components: a dispersion term δd, a polar term δp, and a hydrogen bonding term δh, and is expressed in a three-dimensional space. In this disclosure, the polar term δp is used. δp [cal / cm ３ ] is the Hansen solubility parameter dipole-dipole term, V [cal / cm ３ ] is the molar volume, μ[D] is the dipole moment. For δp, the following formula simplified by Hansen and Beerbower is generally used:

[0327]

[0328] The development accelerator is preferably a hydrophilic polymer compound or a hydrophilic low-molecular-weight compound. In the present disclosure, "hydrophilic" refers to a polarity term of the SP value of 6.0 to 26.0, a hydrophilic polymer compound refers to a compound having a molecular weight (weight-average molecular weight when the molecular weight is distributed) of 3,000 or more, and a hydrophilic low-molecular-weight compound refers to a compound having a molecular weight (weight-average molecular weight when the molecular weight is distributed) of less than 3,000.

[0329] Examples of hydrophilic polymer compounds include cellulose compounds, with cellulose compounds being preferred. Examples of cellulose compounds include cellulose or compounds in which at least a portion of cellulose has been modified (modified cellulose compounds), with modified cellulose compounds being preferred. Preferred modified cellulose compounds include compounds in which at least a portion of the hydroxy groups of cellulose have been substituted with at least one group selected from the group consisting of alkyl groups and hydroxyalkyl groups. The degree of substitution of the compound in which at least a portion of the hydroxy groups of cellulose have been substituted with at least one group selected from the group consisting of alkyl groups and hydroxyalkyl groups is preferably 0.1 to 6.0, more preferably 1 to 4. Preferred modified cellulose compounds are alkyl cellulose compounds or hydroxyalkyl cellulose compounds, with hydroxyalkyl cellulose compounds being more preferred. Preferred alkyl cellulose compounds include methyl cellulose. Preferred hydroxyalkyl cellulose compounds include hydroxypropyl cellulose.

[0330] The molecular weight of the hydrophilic polymer compound (weight average molecular weight when it has a molecular weight distribution) is preferably 3,000 to 5,000,000, and more preferably 5,000 to 200,000.

[0331] Examples of the hydrophilic low-molecular-weight compound include glycol compounds, polyol compounds, organic amine compounds, organic sulfonic acid compounds, organic sulfamine compounds, organic sulfuric acid compounds, organic phosphonic acid compounds, organic carboxylic acid compounds, and betaine compounds, with polyol compounds, organic sulfonic acid compounds, and betaine compounds being preferred.

[0332] Examples of glycol compounds include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, as well as ether or ester derivatives of these compounds. Examples of polyol compounds include glycerin, pentaerythritol, and tris(2-hydroxyethyl)isocyanurate. Examples of organic amine compounds include triethanolamine, diethanolamine, monoethanolamine, and salts thereof. Examples of organic sulfonic acid compounds include alkyl sulfonic acid, toluene sulfonic acid, benzene sulfonic acid, and salts thereof, with alkyl sulfonic acids having an alkyl group of 1 to 10 carbon atoms being preferred. Examples of organic sulfamine compounds include alkyl sulfamic acid and salts thereof. Examples of organic sulfate compounds include alkyl sulfates, alkyl ether sulfates, and salts thereof. Examples of organic phosphonic acid compounds include phenylphosphonic acid and salts thereof. Examples of organic carboxylic acid compounds include tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, and salts thereof. Examples of the betaine compound include a phosphobetaine compound, a sulfobetaine compound, and a carboxybetaine compound, and a preferred example is trimethylglycine.

[0333] The molecular weight of the hydrophilic low-molecular-weight compound (weight average molecular weight when the compound has a molecular weight distribution) is preferably 100 or more and less than 3,000, and more preferably 300 to 2,500.

[0334] The development accelerator is preferably a compound having a cyclic structure. The cyclic structure is not particularly limited, but examples include a glucose ring, an isocyanuric ring, an aromatic ring which may have a heteroatom, and an aliphatic ring which may have a heteroatom, each of which may have at least a portion of a hydroxy group substituted. A glucose ring or an isocyanuric ring is preferred. Examples of compounds having a glucose ring include the above-mentioned cellulose compounds. Examples of compounds having an isocyanuric ring include the above-mentioned tris(2-hydroxyethyl)isocyanurate. Examples of compounds having an aromatic ring include the above-mentioned toluenesulfonic acid and benzenesulfonic acid. Examples of compounds having an aliphatic ring include the above-mentioned alkyl sulfates in which the alkyl group has a cyclic structure.

[0335] The compound having a cyclic structure preferably has a hydroxy group. Preferred examples of the compound having a hydroxy group and a cyclic structure include the above-mentioned cellulose compound and tris(2-hydroxyethyl)isocyanurate.

[0336] The development accelerator is preferably an onium salt compound. Examples of the onium salt compound include ammonium compounds and sulfonium compounds, with ammonium compounds being preferred. Examples of the development accelerator that is an onium salt compound include trimethylglycine. The onium salt compound in the electron-accepting polymerization initiator is a compound whose polarity term of the SP value is not 6.0 to 26.0, and is therefore not included in the development accelerator.

[0337] The image recording layer may contain one type of development accelerator alone, or two or more types may be used in combination. In the present disclosure, one preferred embodiment of the image recording layer is an embodiment in which the image recording layer contains two or more compounds as development accelerators. Specifically, from the viewpoint of on-press developability and ink receptivity, the image recording layer preferably contains the polyol compound and the betaine compound, the betaine compound and the organic sulfonic acid compound, or the polyol compound and the organic sulfonic acid compound as development accelerators.

[0338] The content of the development accelerator relative to the total mass of the image recording layer is preferably from 0.1 to 20% by mass, more preferably from 0.5 to 15% by mass, and even more preferably from 1 to 10% by mass.

[0339] <Other Components> The image recording layer may contain other components such as a surfactant, a polymerization inhibitor, a higher fatty acid derivative, a plasticizer, inorganic particles, an inorganic layer compound, etc. For specific details, see paragraphs 0114 to 0159 of JP-A-2008-284817.

[0340] <<Formation of Image Recording Layer>> The image recording layer in the lithographic printing plate precursor according to the present disclosure can be formed by dispersing or dissolving the necessary components described above in a known solvent to prepare a coating liquid, applying the coating liquid to a support by a known method such as bar coater coating, and drying, as described in paragraphs

[0142] and

[0143] of JP-A No. 2008-195018, for example. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but is generally 0.3 g / m ２ ~3.0g / m ２Within this range, good sensitivity and good film properties of the image recording layer can be obtained. As the solvent, known solvents can be used. Specific examples include water, acetone, methyl ethyl ketone (2-butanone), cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 1-methoxy-2-propanol, 3-methoxy-1-propanol, methoxymethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, methyl lactate, and ethyl lactate. The solvent may be used alone or in combination of two or more. The solid content concentration in the coating solution is preferably 1% by mass to 50% by mass. The coating amount (solid content) of the image recording layer after coating and drying varies depending on the application, but from the viewpoint of obtaining good sensitivity and good film properties of the image recording layer, it is preferably 0.3 g / m ２ ~3.0g / m ２ Preferably, the thickness of the image recording layer in the lithographic printing plate precursor according to the present disclosure is 0.1 μm to 3.0 μm, and more preferably 0.3 μm to 2.0 μm. In the present disclosure, the thickness of each layer in the lithographic printing plate precursor is confirmed by preparing a slice cut in a direction perpendicular to the surface of the lithographic printing plate precursor and observing the cross section of the slice with a scanning electron microscope (SEM).

[0341] [Support] The lithographic printing plate precursor according to the present disclosure has a support. The support can be appropriately selected from known supports for lithographic printing plate precursors. The support is preferably a support having a hydrophilic surface (hereinafter also referred to as a "hydrophilic support").

[0342] The support in the present disclosure is preferably an aluminum plate that has been subjected to a surface roughening treatment and anodization treatment by a known method. That is, the support in the present disclosure preferably comprises an aluminum plate and an anodized aluminum coating disposed on the aluminum plate.

[0343] Preferably, the support has an aluminum plate and an anodized aluminum film disposed on the aluminum plate, the anodized film being closer to the image recording layer than the aluminum plate, the anodized film having micropores extending in the depth direction from the surface facing the image recording layer, the micropores having an average diameter of more than 10 nm and not more than 100 nm at the surface of the anodized film. Furthermore, the micropores are composed of large-diameter pores extending from the surface of the anodized film to a depth of 10 to 1,000 nm and small-diameter pores communicating with the bottoms of the large-diameter pores and extending from the communicating positions to a depth of 20 to 2,000 nm, the large-diameter pores having an average diameter of 15 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. Preferably, the support has an anodized film, the micropores in the anodized film 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, the small-diameter pores having an average diameter of 35 nm or less at the surface of the anodized film, and the large-diameter pores having an average maximum diameter of 40 nm to 300 nm. Furthermore, it is preferable that the support has an anodized coating, and the anodized coating has, in order from the surface of the anodized coating in the depth direction, an upper layer having a thickness of 30 nm to 500 nm and having micropores with an average diameter of 20 nm to 100 nm, an intermediate layer having a thickness of 100 nm 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 nm to 2,000 nm and having micropores with an average diameter of 15 nm or less.

[0344] 1 is a schematic cross-sectional view of one embodiment of an aluminum support 12a. The aluminum support 12a has a laminated structure in which an aluminum plate 18 and an aluminum anodized coating 20a (hereinafter simply referred to as "anodized coating 20a") are laminated in this order. The anodized coating 20a in the aluminum support 12a is located closer to the image recording layer than the aluminum plate 18. In other words, the lithographic printing plate precursor according to the present disclosure preferably has at least an anodized coating, an image recording layer, and a water-soluble resin layer, in this order, on an aluminum plate.

[0345] - Anodized film - A preferred embodiment of the anodized film 20a will be described below. The anodized film 20a is a film produced on the surface of the aluminum plate 18 by anodizing, and this film has extremely fine micropores 22a that are substantially perpendicular to the film surface and are uniformly distributed. The micropores 22a extend from the surface of the anodized film 20a on the image recording layer side (the surface of the anodized film 20a on the side opposite the aluminum plate 18) along the thickness direction (toward the aluminum plate 18).

[0346] The average diameter (average opening diameter) of the micropores 22a in the anodized coating 20a at the surface of the anodized coating is preferably greater than 10 nm and less than or equal to 100 nm. In particular, from the viewpoint of a balance between printing durability, stain resistance, and image visibility, 15 nm to 60 nm is more preferable, 20 nm to 50 nm is even more preferable, and 25 nm to 40 nm is particularly preferable. The diameter inside the pores may be wider or narrower than that at the surface. When the average diameter exceeds 10 nm, excellent printing durability and image visibility are achieved. Furthermore, when the average diameter is 100 nm or less, excellent printing durability is achieved. The average diameter of the micropores 22a is determined by observing the surface of the anodized coating 20a (N = 4) using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, and measuring the diameters (diameters) of micropores present in a 400 nm × 600 nm range at 50 locations in the four obtained images, and averaging the measured values. When the shape of the micropores 22a is not circular, the equivalent circle diameter is used. The "equivalent circle diameter" is the diameter of a circle when the shape of the opening is assumed to be a circle having the same projected area as the projected area of ​​the opening.

[0347] The shape of the micropores 22a is not particularly limited, and although they are generally straight (cylindrical) in Fig. 1, they may also be conical with a diameter that decreases in the depth direction (thickness direction). The shape of the bottom of the micropores 22a is not particularly limited, and may be curved (convex) or flat.

[0348] In the support, the micropores may be composed of large-diameter pores extending from the surface of the anodized coating to a certain depth and small-diameter pores that communicate with the bottoms of the large-diameter pores and extend from the communication positions to a certain depth. For example, as shown in Figure 2, an aluminum support 12b may include an aluminum plate 18 and an anodized coating 20b having micropores 22b each composed of large-diameter pores 24 and small-diameter pores 26. For example, the micropores 22b in the anodized coating 20b are composed of large-diameter pores 24 extending from the surface of the anodized coating to a depth of 10 nm to 1,000 nm (depth D: see Figure 2), and small-diameter pores 26 that communicate with the bottoms of the large-diameter pores 24 and extend from the communication positions to a depth of 20 nm to 2,000 nm. Specifically, for example, the embodiments described in paragraphs 0107 to 0114 of JP-A-2019-162855 can be used.

[0349] The depth of the micropores is not particularly limited, but from the viewpoint of achieving both on-press developability and printing durability, it is preferably 0.01 μm to 1 μm, more preferably 0.05 μm to 0.6 μm, and even more preferably 0.07 μm to 0.25 μm. The depth of the micropores means the distance in the depth direction from the surface of the micropore membrane to the deepest part of the bottom of the micropore.

[0350] The density of micropores on the surface of the film is not particularly limited, but from the viewpoint of achieving both on-press developability and printing durability, it is preferable that the density be 200 pores / μm ２ ~2,000 pieces / μm ２ is preferable, and 400 pieces / μm ２ ~1,500 pieces / μm ２The micropore density is a value obtained by observing the coating surface using a field emission scanning electron microscope (FE-SEM) at a magnification of 150,000 times, arbitrarily selecting measurement regions of 400 nm × 600 nm from four images obtained by observing four different locations, measuring the number of micropores present in the measurement regions, calculating the number of micropores per area of ​​the measurement region for each image, and arithmetically averaging the calculated values.

[0351] The opening rate of the micropores on the surface of the coating is preferably 10% to 90%, more preferably 30% to 85%, from the viewpoint of achieving both on-press developability and printing durability. The opening rate is a value calculated by multiplying the average area of ​​the openings of the large-diameter micropores, calculated using the average radius obtained by dividing the average diameter of the large-diameter micropores on the surface of the coating by 2, by the density (number density) of the micropores on the surface of the coating, and converting the result into a percentage.

[0352] <<Method for Producing Support>> A preferred method for producing a support used in the present disclosure involves, for example, performing the following steps in order: Surface roughening step: a step of roughening an aluminum plate; Anodizing step: anodizing the surface-roughened aluminum plate; Pore widening step: a step of contacting the aluminum plate having the anodized film obtained in the anodizing step with an acid aqueous solution or an alkaline aqueous solution to enlarge the diameter of micropores in the anodized film. The procedure of each step is described in detail below.

[0353] <<Surface Roughening Treatment Step>> The surface roughening treatment step is a step of performing a surface roughening treatment, including electrochemical surface roughening treatment, on the surface of an aluminum plate. This step is preferably performed before the anodizing treatment step described below, but may not be performed if the surface of the aluminum plate already has a preferred surface shape. This can be performed by the method described in paragraphs 0086 to 0101 of JP 2019-162855 A.

[0354] <<Anodizing Treatment Step>> The procedure for the anodizing treatment step is not particularly limited as long as the above-described micropores can be obtained, and known methods can be used. In the anodizing treatment step, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid, or the like can be used as the electrolytic bath. For example, the sulfuric acid concentration can be 100 g / L to 300 g / L. The anodizing treatment conditions are appropriately set depending on the electrolytic solution used, but for example, a solution temperature of 5°C to 70°C (preferably 10°C to 60°C), a current density of 0.5 A / dm ２ ~60 A / dm ２ (preferably 1 A / dm ２ ~60 A / dm ２ ), voltage 1V to 100V (preferably 5V to 50V), electrolysis time 1 second to 100 seconds (preferably 5 seconds to 60 seconds), and coating amount 0.1 g / m ２ ~5g / m ２ (preferably 0.2 g / m ２ ~3g / m ２ ) are listed.

[0355] <<Pore Widening Treatment>> The pore widening treatment is a treatment (pore size enlargement treatment) that enlarges the diameter (pore diameter) of micropores present in the anodized coating formed by the above-mentioned anodizing treatment step. The pore widening treatment can be carried out by contacting the aluminum plate obtained by the above-mentioned anodizing treatment step with an acid aqueous solution or an alkaline aqueous solution. The contact method is not particularly limited, and examples include immersion and spraying.

[0356] <<Silicate Treatment Step>> The method for producing a support preferably includes a silicate treatment step in which an aluminum plate on which an anodized film has been formed by the above-mentioned anodizing treatment and pore widening treatment is subjected to silicate treatment. This is because the silicate treatment step makes it possible to easily produce a support having a specific Si atomic weight within a predetermined range, as described below. The silicate treatment is a treatment in which an anodized film formed on an aluminum plate is brought into contact with an aqueous solution containing an alkali metal silicate, such as sodium silicate or potassium silicate (hereinafter also referred to as the "treatment solution"). In the silicate treatment, it is preferable to immerse the aluminum plate with the anodized film in the treatment solution. For silicate treatment, reference can be made to the methods and procedures described in U.S. Pat. Nos. 2,714,066 and 3,181,461, the disclosures of which are incorporated herein by reference.

[0357] Examples of alkali metal silicates used in the silicate treatment include sodium silicate, potassium silicate, and lithium silicate. In addition to the alkali metal silicate, the treatment solution may further contain an appropriate amount of an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. The treatment solution may also contain an alkaline earth metal salt or a Group 4 (Group IVA) metal salt. Examples of alkaline earth metal salts include nitrates such as calcium nitrate, strontium nitrate, magnesium nitrate, and barium nitrate; sulfates; hydrochlorides; phosphates; acetates; oxalates; and borates. Examples of Group 4 (Group IVA) metal salts include titanium tetrachloride, titanium trichloride, potassium titanium fluoride, potassium titanium oxalate, titanium sulfate, titanium tetraiodide, zirconium oxide chloride, zirconium dioxide, zirconium oxychloride, and zirconium tetrachloride. These alkaline earth metal salts and Group 4 (Group IVA) metal salts may be used alone or in combination of two or more.

[0358] The treatment conditions for the silicate treatment and the concentration of the treatment solution are appropriately adjusted depending on the size of the aluminum plate and anodized film to be treated, as well as the structure (specific structure) and density of the micropores. The content of the alkali metal silicate in the treatment solution is, for example, 3% to 30% by mass, and preferably 3% to 10% by mass, relative to the total mass of the treatment solution. The temperature of the treatment solution used in the silicate treatment is, for example, 30°C to 80°C, and more preferably 40°C to 70°C. The treatment time for the silicate treatment is, for example, 1 second to 15 seconds, and more preferably 3 seconds to 10 seconds. The amount of silicate adsorbed to the support surface by the silicate treatment can alternatively be expressed as the average Si atomic weight calculated when a circular area with a diameter of 30 mm is measured by fluorescent X-ray analysis (hereinafter also referred to as the "specific Si atomic weight"). The Si atomic weight is obtained by performing X-ray fluorescence analysis on a circular region with a diameter of 30 mm on the surface of the support, measuring the Kα ray intensity of the Si element, and then quantifying the Si atomic weight present on the coating surface using a calibration curve. Here, the "average Si atomic weight" refers to a value obtained by selecting three or more non-overlapping circular regions on the surface of the anodized coating facing the image recording layer, determining the Si atomic weight for each region, and then arithmetically averaging the Si atomic weights obtained for each region.

[0359] <<Method for Measuring Si Atomic Weight>> The Si atomic weight in the anodized film was measured using X-ray fluorescence analysis and a calibration curve method. A standard sample for creating a calibration curve was prepared by uniformly dropping an aqueous solution containing a known amount of silicon atoms onto an aluminum plate within an area of ​​30 mmφ and then drying the resulting solution. The measurement conditions for the X-ray fluorescence analysis are shown below.

[0360] X-ray fluorescence analyzer: RIX3000 manufactured by Rigaku Electric Industrial Co., Ltd., X-ray tube: Rh, measurement spectrum: Si-Kα, tube voltage: 50 kV, tube current: 50 mA, slit: COARSE, analyzing crystal: RX4, detector: F-PC, analysis area: 30 mmφ, peak position (2θ): 144.75 deg., background (2θ): 140.70 deg. and 146.85 deg., accumulation time: 80 seconds / sample. The Si atomic weight was set to 0.001 g / m from the viewpoints of on-machine developability over time, printing durability, and stain resistance. ２~0.2g / m ２ is preferred, and 0.05 g / m ２ ~0.1g / m ２ is more preferred.

[0361] The support may have, if necessary, a backcoat layer containing an organic polymer compound described in JP-A-5-45885 or a silicon alkoxy compound described in JP-A-6-35174 on the surface opposite to the image recording layer.

[0362] [Undercoat Layer] The lithographic printing plate precursor according to the present disclosure preferably has an undercoat layer (sometimes referred to as an intermediate layer) between the image recording layer and the support. The undercoat layer strengthens adhesion between the support and the image recording layer in exposed areas and facilitates peeling of the image recording layer from the support in unexposed areas, thereby contributing to improving developability while suppressing a decrease in printing durability. In addition, in the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, thereby preventing heat generated by exposure from diffusing to the support and reducing sensitivity.

[0363] 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.

[0364] 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 ３is 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.

[0365] 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.

[0366] The content of ethylenically unsaturated bond groups in the polymer used in the undercoat layer is preferably 0.1 mmol to 10.0 mmol, more preferably 0.2 mmol to 5.5 mmol, per 1 g of the polymer. The weight-average molecular weight (Mw) of the polymer used in the undercoat layer is preferably 5,000 or more, more preferably 10,000 to 300,000.

[0367] In addition to the above-described compounds for use in an undercoat layer, the undercoat layer may contain, in order to prevent staining over time, a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, a compound having an amino group or a functional group having polymerization inhibitory ability and a group that interacts with the support surface (e.g., 1,4-diazabicyclo[2.2.2]octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, etc.), and the like.

[0368] The undercoat layer is applied by a known method. The coating amount (solid content) of the undercoat layer is 0.1 mg / m ２ ~100 mg / m ２ is preferred, and 1 mg / m ２ ~30 mg / m ２ is more preferred.

[0369] [Outermost Layer] The lithographic printing plate precursor according to the present disclosure may have an outermost layer (sometimes referred to as a "protective layer" or "overcoat layer") on the surface of the image recording layer opposite the support side. The lithographic printing plate precursor according to the present disclosure preferably has a support, an image recording layer, and an outermost layer in this order. The outermost layer may have the function of preventing scratches on the image recording layer and ablation during exposure to high-intensity laser light, in addition to the function of blocking oxygen to suppress image formation inhibiting reactions.

[0370] The outermost layer may be a known outermost layer ("protective layer" or "overcoat layer") in an on-press development type lithographic printing plate precursor. Specifically, the outermost layer described in paragraphs 0444 to 0462 of WO 2022 / 019217 can be suitably used.

[0371] Furthermore, from the viewpoint of inhibiting decomposition of the infrared absorbent contained in the image recording layer by ozone, a layered compound can also be used in the outermost layer. The layered compound is a particle having a thin, flat plate shape, and specifically, the inorganic layered compounds described in paragraphs 0021 to 0034 of Japanese Patent No. 5172097 are preferably used. By using a layered compound in the outermost layer, the length of the ozone penetration path can be increased, and the decomposition of the infrared absorbent can be inhibited by improving the ozone blocking property.

[0372] Regarding the shape of the layered compound used in the present disclosure, from the viewpoint of increasing the ozone penetration path length and improving ozone blocking properties, 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 coating 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 thickness to the major axis of the particle, and can be measured, for example, from a projection diagram of a micrograph of the particle.The larger the aspect ratio, the greater the effect obtained.

[0373] The particle size of the layered compound used in the present disclosure is preferably 1 μm to 20 μm, more preferably 1 μm to 10 μm, and particularly preferably 2 μm to 5 μm, in terms of the average major axis. When the particle size is 1 μm or more, the ozone blocking properties are sufficient, and the effects of the present disclosure can be fully exhibited. When the particle size is 20 μm or less, the dispersion stability in the coating solution is sufficient, and stable coating can be performed. Furthermore, from the viewpoint of improving the ozone blocking properties, the average thickness of the particles is preferably 0.1 μm or less, more preferably 0.05 μm or less, and particularly preferably 0.01 μm or less. For example, the size of swellable synthetic mica, a representative layered compound, is 1 nm to 50 nm in thickness and has a surface size of about 1 μm to 20 μm.

[0374] The amount of the layered compound used in the present disclosure is 1 mg / m ２ ~1,000mg / m ２ is preferred, and 5 mg / m ２ ~500 mg / m ２ More preferably, 10 mg / m ２ ~100 mg / m ２ The amount of addition is particularly preferably 1 mg / m２ If the concentration is more than 1,000 mg / m, the ozone blocking property is sufficient. ２ If it is below this level, sufficient on-press developability can be obtained.

[0375] The lithographic printing plate precursor according to the present disclosure may have layers other than those described above. The other layers are not particularly limited, and known layers may be included. For example, a backcoat layer may be provided on the side of the support opposite to the image recording layer side, as needed.

[0376] (Method for preparing a lithographic printing plate and a lithographic printing method) A lithographic printing plate can be prepared by imagewise exposing the lithographic printing plate precursor according to the present disclosure and then subjecting it to a development process. The method for preparing a lithographic printing plate according to the present disclosure preferably includes a step of imagewise exposing the on-press development type lithographic printing plate precursor according to the present disclosure (hereinafter also referred to as an "exposure step"), and a step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas (hereinafter also referred to as an "on-press development step"). The lithographic printing method according to the present disclosure preferably includes a step of imagewise exposing the on-press development type lithographic printing plate precursor according to the present disclosure (exposure step), a step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image recording layer in non-image areas to prepare a lithographic printing plate (on-press development step), and a step of printing with the obtained lithographic printing plate (printing step).

[0377]

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

[0378] <Exposure Step> The method for producing a lithographic printing plate according to the present disclosure preferably includes an exposure step of imagewise exposing the lithographic printing plate precursor according to the present disclosure to form exposed and unexposed areas. The lithographic printing plate precursor according to the present disclosure is preferably exposed to laser light through a transparent original having a line image, a halftone dot image, or the like, or imagewise by laser light scanning using digital data. The wavelength of the light source used is preferably 750 nm to 1,400 nm. As a light source with a wavelength of 750 nm to 1,400 nm, a solid-state laser or semiconductor laser that emits infrared light is suitable. With regard to the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably 20 microseconds or less, and the irradiation energy amount is 10 mJ / cm. ２ ~300 mJ / cm ２ It is preferable to use a multi-beam laser device to shorten the exposure time. The exposure mechanism may be any of an internal drum system, an external drum system, a flatbed system, etc. Image exposure can be carried out by a conventional method using a plate setter or the like. In the case of on-press development, the lithographic printing plate precursor may be mounted on a printing press and then image exposure may be carried out on the printing press.

[0379] <On-Press Development Step> The method for producing a lithographic printing plate according to the present disclosure preferably includes an on-press development step of supplying at least one selected from the group consisting of printing ink and fountain solution on a printing press to remove the image-recording layer in non-image areas.

[0380] [On-Press Development Method] In the on-press development method, an image-wise exposed lithographic printing plate precursor is preferably supplied with an oil-based ink and an aqueous component on a printing press, and the image-recording layer in non-image areas is removed to produce a lithographic printing plate. That is, after image-wise exposure, the lithographic printing plate precursor is either mounted on a printing press as is without any development treatment, or the lithographic printing plate precursor is mounted on a printing press, image-wise exposed on the press, and then oil-based ink and an aqueous component are supplied to print. In the early stages of printing, the uncured image-recording layer in the non-image areas is dissolved or dispersed by either or both of the supplied oil-based ink and aqueous component, thereby exposing a hydrophilic surface in those areas. Meanwhile, in the exposed areas, the image-recording layer cured by exposure forms an oil-based ink-receptive area with an oleophilic surface. Either an oil-based ink or an aqueous component may be supplied first to the plate surface, but it is preferable to supply the oil-based ink first to prevent contamination of the aqueous component with the components of the image-recording layer from which the aqueous component has been removed. In this way, the lithographic printing plate precursor is developed on the press and used as is for printing a large number of sheets. As the oil-based ink and aqueous component, printing ink and fountain solution for ordinary lithographic printing are preferably used.

[0381] The laser used for imagewise exposure of the lithographic printing plate precursor according to the present disclosure preferably has a light source wavelength of 300 nm to 450 nm or 750 nm to 1,400 nm. In the case of a light source of 300 nm to 450 nm, a lithographic printing plate precursor containing in an image recording layer a sensitizing dye having an absorption maximum in this wavelength region is preferably used, and for a light source of 750 nm to 1,400 nm, the above-mentioned light sources are preferably used. As a light source of 300 nm to 450 nm, a semiconductor laser is suitable.

[0382] <Printing Step> The lithographic printing method according to the present disclosure includes a printing step in which printing ink is supplied to a lithographic printing plate to print a recording medium. The printing ink is not particularly limited, and various known inks can be used as desired. Examples of preferred printing inks include oil-based inks and ultraviolet-curable inks (UV inks). In the printing step, dampening water may be supplied as needed. The printing step may be performed consecutively to the on-press development step without stopping the printing press. The recording medium is not particularly limited, and known recording media can be used as desired.

[0383] In the method for preparing a lithographic printing plate from a lithographic printing plate precursor according to the present disclosure and the lithographic printing method according to the present disclosure, the entire surface of the lithographic printing plate precursor may be heated, as necessary, before exposure, during exposure, or between exposure and development. Such heating promotes the image formation reaction in the image recording layer, resulting in advantages such as improved sensitivity and printing durability and stabilized sensitivity. Heating before development is preferably carried out under mild conditions at 150°C or less. This embodiment can prevent problems such as hardening of non-image areas. Heating after development is preferably carried out under very strong conditions, preferably in the range of 100°C to 500°C. Within this range, sufficient image strengthening effect can be obtained and problems such as support degradation and thermal decomposition of image areas can be suppressed.

[0384] (Laminate) The laminate according to the present disclosure may be any laminate in which an on-press development type lithographic printing plate according to the present disclosure is laminated, but may also be a laminate in which an on-press development type lithographic printing plate having an image recording layer is laminated on a support, wherein the image recording layer contains an onium compound, a borate compound, and a polymerizable compound, and the solubility of a salt formed by a pair of a cation moiety of the onium compound and an anion moiety of the borate compound in 2-ethylhexyl methacrylate at 25°C is 0.01% by mass or more, and the laminate has a protective material disposed at at least the uppermost part of the laminate to protect the on-press development type lithographic printing plate, and the saturated mass per unit area of ​​the protective material at 25°C and 30% RH is X (g / m ２ ), the saturated mass per unit area at 25°C and 80% RH is Y (g / m ２), it is preferable to satisfy the following formula (2): (Y−X) / Y≦0.06 (2)

[0385] Preferred aspects of the on-press development type lithographic printing plate precursor in the laminate according to the present disclosure are the same as the preferred aspects of the on-press development type lithographic printing plate precursor according to the present disclosure described above.

[0386] <Protective Material> The laminate according to the present disclosure preferably includes a protective material that is disposed at least on top of the stacked on-press development type lithographic printing plate precursors and protects the on-press development type lithographic printing plate precursors. From the viewpoint of suppressing development defects over time, the value of (Y-X) / Y of the protective material is preferably 0.06 or less, more preferably 0.03 or less, and particularly preferably 0.01 or less. The lower limit of the value of (Y-X) / Y is 0.

[0387] The value of (Y-X) / Y of the protective material is measured as follows: The protective material is cut into a size of 10 cm x 20 cm and dried in an oven at 100°C for 1 hour. The dried protective material is conditioned in an environment of 25°C and 30% RH to determine the saturated mass X. Specifically, the mass is measured every hour, and the mass X at each measurement is calculated. ｎ and mass X from 1 hour ago ｎ－１ The point at which the following relationship is met is determined to be the point at which the saturated mass is reached. ｎ -X ｎ－１ ≦0.005g Saturated mass X (g / m ２ ) is calculated using the following formula: X = X ｎ The protective material was conditioned in an environment of 25°C and 80% RH, and the saturated mass Y was determined. Specifically, the mass was measured every hour, and the mass Y at each measurement was calculated. ｎ and mass Y from one hour ago ｎ－１ The point at which the following relationship is met is determined to be the point at which the saturated mass is reached. ｎ -Y ｎ－１ ≦0.005g Saturated mass Y (g / m ２ ) is calculated by the following formula: Y = Y ｎ From the X and Y obtained above, the water absorption rate of the protective material is calculated as follows: Water absorption rate = (Y - X) / Y

[0388] Examples of materials for the protective material include cardboard, cardboard, plastic, foam plastic, and rubber. From the viewpoint of suppressing development defects over time, at least one material selected from the group consisting of cardboard, cardboard, laminated paper, plastic sheet, foam plastic sheet, and rubber sheet is preferred, cardboard or plastic sheet is more preferred, and plastic sheet is particularly preferred. Known polymers can be used as the plastic, including polyester, polycarbonate, and polyolefin, with polyester being preferred. One side of the cardboard surface may be coated with a plastic material, and examples of plastic materials used for coating include polypropylene and low-density polyethylene. The cardboard surface may also be metal-vapor-deposited, and aluminum is preferred as the metal from the viewpoints of processability and cost. The size (length x width) of the protective material is not particularly limited and can be appropriately selected depending on the on-press development-type lithographic printing plate precursor to be used. For example, the size may be the same as or slightly larger than the on-press development-type lithographic printing plate precursor. The thickness of the protective material is not particularly limited, but is preferably 10 μm to 10 mm, more preferably 100 μm to 5 mm, from the viewpoints of strength, moisture permeability, and suppression of development defects over time. Furthermore, the thickness of the protective material is preferably 100 μm or more, from the viewpoints of strength, moisture permeability, and suppression of development defects over time. Furthermore, it is preferable that the protective material be disposed not only at the top but also at the bottom of the laminate.

[0389] <Interleaf Paper> The laminate according to the present disclosure may have an interleaf paper between the two stacked on-press development type lithographic printing plate precursors. Alternatively, an interleaf paper may be present between the on-press development type lithographic printing plate precursor and the protective material. Furthermore, an interleaf paper may be present at the bottom of the laminate.

[0390] In order to reduce material costs, it is preferable to select low-cost raw materials for the interleaving paper used in the present disclosure. For example, paper made from 100% wood pulp, paper made from a mixture of wood pulp and synthetic pulp, or paper with a low-density or high-density polyethylene layer on the surface thereof can be used. Specifically, examples include acidic paper made from a stock prepared by beating bleached kraft pulp and diluting it to a concentration of 4% by weight, adding a sizing agent and a strength agent at 0.1% by weight and 0.2% by weight of the base paper weight, and further adding aluminum sulfate until the pH reaches 5.0. However, neutral paper using a neutral sizing agent such as alkyl ketene dimer (AKD) or alkenyl succinic anhydride (ASA), calcium carbonate as a filler instead of aluminum sulfate, and having a pH of 7 to 8 is preferred. Among these, paper is preferred as the interleaving paper, and paper containing aluminum sulfate or calcium carbonate is more preferred, with calcium carbonate being particularly preferred. The material of the interleaf paper is preferably paper containing 50% by mass or more of pulp, more preferably paper containing 70% by mass or more of pulp, and particularly preferably paper containing 80% by mass or more of pulp.

[0391] The calcium content of the slip paper is preferably 0.15% by mass to 0.5% by mass, more preferably 0.2% by mass to 0.45% by mass, and particularly preferably 0.25% by mass to 0.4% by mass, based on the total amount of the slip paper. The calcium content of the slip paper can be obtained by measuring the slip paper using fluorescent X-rays. The calcium contained in the paper is mainly calcium carbonate, which is widely used as a filler in neutral paper and has the effect of increasing the whiteness of the paper.

[0392] The basis weight of the slip sheet (measured by the method specified in JIS P8124 (2011)) is not particularly limited, but from the viewpoint of printing durability and on-press development, it is preferably 29 g / m ２ ~80g / m ２ It is preferable that the thickness is 35 g / m ２ ~70g / m ２ More preferably, it is 51 g / m ２ ~65g / m ２From the viewpoints of printing durability and on-press development, the basis weight of the slip sheet is particularly preferably 51 g / m ２ The thickness of the slip sheet (measured by the method specified in JIS P8118 (2014)) is not particularly limited, but is preferably 20 μm to 100 μm, more preferably 42 μm to 80 μm, even more preferably 45 μm to 65 μm, and particularly preferably 45 μm to 55 μm.

[0393] Furthermore, from the viewpoint of suppressing color spots, the moisture content of the slip paper (the moisture content of the slip paper when the slip paper is stored at 25°C / 50% RH and the moisture content of the slip paper has stabilized) is preferably 0% by mass to 20% by mass, more preferably 0% by mass to 15% by mass, and particularly preferably 0% by mass to 10% by mass, relative to the total mass of the slip paper.

[0394] As the interleaf paper, the interleaf paper described in JP-A-2010-76336 can be suitably used.

[0395] The shape of the slip sheet is not particularly limited, but examples thereof include a shape that is the same as the shape of the planographic printing plate precursor in the surface direction, or a shape that is larger than that.

[0396] Furthermore, the laminate according to the present disclosure may be packaged as a whole by a known method.

[0397] The present disclosure will be described in detail below using examples, but the present disclosure is not limited thereto. In these examples, "%" and "parts" mean "% by mass" and "parts by mass", respectively, unless otherwise specified. In addition, in polymer compounds, unless otherwise specified, the molecular weight is the weight average molecular weight (Mw), and the ratio of the constituent repeating units is expressed as a molar percentage. In addition, the weight average molecular weight (Mw) is a value measured as a polystyrene equivalent value by gel permeation chromatography (GPC).

[0398] (Examples 1 to 59 and Comparative Examples 1 and 2) Each lithographic printing plate precursor was obtained by forming an undercoat layer described in Table 1 or Table 2 on a support described in Table 1 or Table 2, forming an image recording layer described in Table 1 or Table 2 on the undercoat layer, and forming or not forming a protective layer described in Table 1 or Table 2 on the image recording layer. Details of the method for forming each layer will be described later.

[0399] <Preparation of Support 1> An aluminum plate (aluminum alloy plate) having a thickness of 0.3 mm and a material of 1S was subjected to the following treatments to produce Support 1. Note that a water-rinsing treatment was performed between all treatment steps, and after the water-rinsing treatment, the liquid was removed using nip rollers.

[0400] - Alkali Etching Treatment (1) - An aluminum plate was etched by spraying an aqueous solution of caustic soda with a caustic soda concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass onto the aluminum plate at a temperature of 70°C. The aluminum was then rinsed with water by spraying. The amount of dissolved aluminum on the surface to be subsequently subjected to electrochemical graining treatment was 5 g / m. ２ It was.

[0401] - Desmutting Treatment Using Acidic Aqueous Solution (1) - Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate with a sprayer, and the desmutting treatment was carried out for 3 seconds. The acidic aqueous solution used in the desmutting treatment was an aqueous solution containing 150 g / L of sulfuric acid. The liquid temperature was 30°C.

[0402] -Hydrochloric Acid Electrolysis- Next, hydrochloric acid electrolysis was performed using an electrolytic solution with a hydrochloric acid concentration of 13 g / L, an aluminum ion concentration of 15 g / L, and a sulfuric acid concentration of 1.0 g / L, using an alternating current. The temperature of the electrolytic solution was 25°C. The aluminum ion concentration was adjusted by adding aluminum chloride. The waveform of the alternating current was a sine wave with symmetrical positive and negative waveforms, the frequency was 50 Hz, the anode reaction time and cathode reaction time in one cycle of the alternating current were 1:1, and the current density was 35 A / dm at the peak current value of the alternating current waveform. ２ The total amount of electricity that the aluminum plate takes in the anode reaction is 320 C / dm ２ The electrolytic treatment was 80 C / dm ２The test was carried out four times with a 2.5 second interval between each test. A carbon electrode was used as the counter electrode for the aluminum plate. After that, the aluminum plate was washed with water.

[0403] - Alkali Etching Treatment (2) - After the hydrochloric acid electrolysis, the aluminum plate was etched by spraying an aqueous solution of caustic soda containing 5% by mass of caustic soda and 0.5% by mass of aluminum ions at a temperature of 45°C. The amount of dissolved aluminum on the surface that had been subjected to the hydrochloric acid electrolysis was 0.1 g / m ２ After that, a water washing treatment was carried out.

[0404] - Desmutting Treatment Using Acidic Aqueous Solution (2) - Next, a desmutting treatment was carried out using an acidic aqueous solution. Specifically, the acidic aqueous solution was sprayed onto the aluminum plate, and the desmutting treatment was carried out for 3 seconds. The acidic aqueous solution used in the desmutting treatment had a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The liquid temperature was 35°C.

[0405] <First-stage anodizing treatment> The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis having the structure shown in Fig. 3. A 170 g / L aqueous sulfuric acid solution was used as the electrolytic solution, and the solution temperature was 40°C and the current density was 20 A / dm ２ Anodizing treatment was carried out under the conditions of ２An anodized film of the formula (I) was formed on the surface of the aluminum plate 616. In the anodizing treatment apparatus 610 shown in FIG. 3, the aluminum plate 616 is transported as indicated by the arrow in FIG. 3. In a power supply tank 612 containing an electrolytic solution 618, the aluminum plate 616 is positively charged by a power supply electrode 620. The aluminum plate 616 is then transported upward in the power supply tank 612 by rollers 622, redirected downward by nip rollers 624, transported toward an electrolytic treatment tank 614 containing an electrolytic solution 626, and redirected horizontally by rollers 628. The aluminum plate 616 is then negatively charged by an electrolytic electrode 630, thereby forming an anodized film on the surface of the aluminum plate 616. The aluminum plate 616 leaves the electrolytic treatment tank 614 and is transported to a subsequent process. In the anodizing device 610, a direction changing means is formed by a roller 622, a nip roller 624, and a roller 628, and the aluminum plate 616 is transported in a mountain shape and an inverted U shape in the space between the power supply tank 612 and the electrolytic treatment tank 614 by the roller 622, the nip roller 624, and the roller 628. The power supply electrode 620 and the electrolytic electrode 630 are connected to a DC power supply 634. A tank wall 632 is disposed between the power supply tank 612 and the electrolytic treatment tank 614.

[0406] -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 5 seconds to perform a pore widening treatment. Thereafter, the plate was rinsed with water by spraying.

[0407] - Second-stage anodizing treatment - The second-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 3. A 170 g / L aqueous sulfuric acid solution was used as the electrolytic solution, 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.

[0408] -Silicate Treatment- The aluminum plate that had been subjected to the second anodizing treatment was immersed for 12 seconds in a No. 3 sodium silicate aqueous solution with a concentration of 5% by mass and a liquid temperature of 40°C to obtain Support 1. The amount of Si deposited was 8 mg / m ２The average diameter of the micropores was 30 nm.

[0409] <Preparation of Support 2> In the preparation method of Support 1, the silicate treatment conditions were changed to immersion for 12 seconds in a No. 3 aqueous solution of sodium silicate with a concentration of 5% by mass and a liquid temperature of 55°C, to obtain Support 2. The remaining steps were carried out using the same method and procedure as in the preparation method of Support 1. The amount of Si deposited on Support 2 was 13 mg / m ２ It was.

[0410] <Preparation of Support 3> In the preparation method of Support 1, the silicate treatment conditions were changed to immersion for 12 seconds in a No. 3 aqueous solution of sodium silicate with a concentration of 5% by mass and a liquid temperature of 65°C, to obtain Support 3. The remaining steps were carried out using the same method and procedure as in the preparation method of Support 1. The amount of Si deposited on Support 3 was 21 mg / m ２ It was.

[0411] <Preparation of Support 4> A 0.3 mm thick aluminum plate (aluminum alloy plate) made of material 1S was subjected to the following treatments (F-a) to (F-f) to prepare Support 2. Note that a water rinsing treatment was performed between all treatment steps, and after each water rinsing treatment, the liquid was removed using nip rollers.

[0412] (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.

[0413] (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.

[0414] (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.

[0415] (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.

[0416] (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.

[0417] (F-f) First-stage anodizing treatment: The first-stage anodizing treatment was carried out using an anodizing apparatus using direct current electrolysis with the structure shown in Figure 3. A 150 g / L aqueous phosphoric acid solution was used as the electrolyte, and the solution temperature was 35°C and the current density was 4.5 A / dm ２ Anodizing treatment was carried out under the conditions of ２ The average diameter of the micropores in the support 4 was 40 nm. ＊ a ＊ b ＊ Lightness L in the color system ＊ The value was 82.4.

[0418] <Preparation of Support 5> Support 5 was prepared according to the support manufacturing method of Example 5 of WO 2021 / 67054.

[0419] <Formation of Undercoat Layer 1> An undercoat layer coating solution (1) having the following composition was applied on a support in a dry coating amount of 26 mg / m ２ The undercoat layer 1 was formed by coating the undercoat layer 1 so that the thickness of the undercoat layer 1 was 1 / 2 mm.

[0420] - Undercoat layer coating solution (1) - Undercoat layer compound (1) (structure shown below): 0.013 parts Hydroxyethyliminodiacetic acid: 0.005 parts Tetrasodium ethylenediaminetetraacetate: 0.005 parts Polyoxyethylene lauryl ether: 0.0003 parts Water: 3.15 parts

[0421]

[0422] The numerical value in the parentheses to the right of each structural unit in the compound (1) 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.

[0423] <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 in such a manner that the thickness of the undercoat layer 2 becomes 1 / 4 of the thickness of the undercoat layer 2.

[0424] - Undercoat layer coating liquid (2) - Polyacrylic acid aqueous solution (40% by mass) (Jurymer AC-10S, manufactured by Toagosei Co., Ltd.): 3.0 parts Water: 27.0 parts

[0425] <Formation of Image Recording Layer A> Image recording layer coating solution A having the following composition was applied onto the undercoat layer with a bar, and then dried in an oven at 110°C for 40 seconds to obtain a dry coating amount of 1.0 g / m ２ The amount of the compounds listed in Table 1 or 2 added was selected so that the dry coating amount would be the content listed.

[0426] -Image recording layer coating liquid A- 2-butanone: 5.3155 parts 1-methoxy-2-propanol: 2.8825 parts Methanol: 2.3391 parts Polymerizable compound: listed in Table 1 or Table 2 Electron-accepting polymerization initiator: listed in Table 1 or Table 2 Electron-donating polymerization initiator: listed in Table 1 or Table 2 Infrared absorber: listed in Table 1 or Table 2 Acid color former: listed in Table 1 or Table 2 Tricresyl phosphate: 0.045 parts Anionic surfactant (A-1): 0.0162 parts Microgel liquid 2: 2.8779 parts Fluorine-based surfactant (W-1): 0.0042 parts

[0427] <Formation of Image Recording Layer B> Image recording layer coating solution B having the following composition was applied onto the undercoat layer with a bar, and then dried in an oven at 110°C for 40 seconds to obtain a dry coating amount of 0.9 g / m ２ The amount of the compound shown in Table 1 or 2 added was selected so that the dry coating amount would be the content shown.

[0428] -Image Recording Layer Coating Solution B- 1-Propanol: 4.94 parts 2-Butanone: 2.40 parts γ-Butyllactone: 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 Polymerizable compound: listed in Table 1 or Table 2 Electron-accepting polymerization initiator: listed in Table 1 or Table 2 Electron-donating polymerization initiator: listed in Table 1 or Table 2 Infrared absorber: listed in Table 1 or Table 2 Acid color former: listed in Table 1 or Table 2 *1: The polymer dispersion was prepared according to the description of European Patent Application Publication No. 1765593 and used as a 23.5 mass% dispersion in n-propanol / water (80:20 [mass ratio]). *2: 5.0 mass% aqueous solution *3 25 mass% 1-methoxy-2-propanol solution (manufactured by BYK Chemie)

[0429] <Formation of Protective Layer A> After coating the image recording layer with a coating solution A for protective layer having the following composition using a bar, the coating solution was dried in an oven at 120°C for 60 seconds to obtain a dry coating amount of 0.1 g / m ２ A protective layer A was formed.

[0430] -Coating Solution A for Protective Layer- The following components were dissolved or dispersed in ion-exchanged water to prepare Coating Solution A for Protective Layer. Water: 1.0161 parts FS-102 (styrene-acrylic resin, manufactured by Nippon Paint Industrial Coatings Co., Ltd., Tg = 103°C, 17% aqueous dispersion): 0.1177 parts Metrose SM04 (methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd., methoxy substitution degree 1.8): 0.0600 parts Rapisol A-80 (anionic surfactant, manufactured by NOF Corporation, 80% aqueous solution): 0.0063 parts Ion-exchanged water: 1.0161 parts

[0431] <Formation of Protective Layer B> After coating the protective layer coating solution B having the following composition on the image recording layer with a bar, the coating solution was dried in an oven at 120°C for 60 seconds to obtain a dry coating amount of 0.1 g / m ２ A protective layer B was formed.

[0432] -Protective Layer Coating Solution B- Inorganic layer compound dispersion (1) (below): shown in Table 1 or Table 2 Hydrophilic polymer (1) (structure below, Mw: 30,000): 0.03 parts Metolose SM04: 0.0600 parts Rapisol A-80 (80% aqueous solution): 0.0063 parts Water: 2.0 parts

[0433]

[0434] --Preparation of Inorganic Layered Compound Dispersion (1)-- 6.4 parts of synthetic mica Somasif ME-100 (manufactured by Co-op Chemical Co., Ltd.) was added to 193.6 parts of ion-exchanged water, and the mixture was dispersed using a homogenizer until the volume average particle size (laser scattering method) reached 3 μm. The aspect ratio of the resulting dispersed particles was 100 or more.

[0435] <Monomer Solubility> A salt containing a pair of the cation moiety of an onium compound and the anion moiety of a borate compound was prepared in the image recording layer, and its solubility in 2-ethylhexyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was measured at 25°C. 2-Ethylhexyl methacrylate, adjusted to 25°C, was weighed into a glass container containing a magnetic stirrer tip, and the salt was added to a desired concentration. The salt was added while stirring to prevent lumping. After stirring for 24 hours at 25°C, the solution was allowed to stand for another 24 hours, and the state of dissolution was visually confirmed. If there was no residue on the bottom of the glass container and the solution was transparent after standing, it was determined to have dissolved. The highest concentration obtained was determined to be the solubility of the salt. The solubility measurements were performed at the following concentration intervals:

[0436] -Solubility measurement concentration intervals- 0.001% by mass or more and less than 0.01% by mass: 0.001% by mass intervals 0.01% by mass or more and less than 0.1% by mass: 0.01% by mass intervals 0.1% by mass or more and less than 1.0% by mass: 0.1% by mass intervals 1.0% by mass or more and less than 10.0% by mass: 1% by mass intervals 10.0% by mass or more: 5% by mass intervals

[0437] <Water absorption rate of protective material (value of (Y-X) / Y)> The protective material was cut into a size of 10 cm x 20 cm and dried in an oven at 100°C for 1 hour. The dried protective material was conditioned in an environment of 25°C and 30% RH, and the saturated mass X was determined. Specifically, the mass was measured every hour, and the mass X at each measurement was calculated. ｎ and mass X from 1 hour ago ｎ－１ The point at which the following relationship was established was judged to have reached saturation mass. ｎ -X ｎ－１ ≦0.005g Saturated mass X (g / m ２ ) was calculated by the following formula: X = X ｎ The protective material was conditioned in an environment of 25°C and 80% RH, and the saturated mass Y was determined. Specifically, the mass was measured every hour, and the mass Y at each measurement was calculated. ｎ and mass Y from one hour ago ｎ－１ The point at which the following relationship was established was judged to have reached saturation mass.ｎ -Y ｎ－１ ≦0.005g Saturated mass Y (g / m ２ ) was calculated by the following formula: Y = Y ｎ From the X and Y obtained above, the water absorption rate of the protective material was calculated as follows: Water absorption rate = (Y - X) / Y Using the water absorption rate, the saturated mass per unit area of ​​the protective material at 25°C and 30% RH was calculated as X (g / m ２ ), the saturated mass per unit area at 25°C and 80% RH is Y (g / m ２ ), it was determined whether the following formula (2) was satisfied: (Y−X) / Y≦0.06 (2)

[0438] <On-machine developability over time (ability to suppress development defects over time)> After passing the above-mentioned 62 cm × 40 cm lithographic printing plate precursor through nip rolls 50 times, the interleaf paper and the lithographic printing plate precursor were conditioned in a 25°C, 85% RH environment, and 30 sheets were stacked alternately in the same environment. Further 62 cm × 40 cm protective materials described in Table 3 were placed on top and bottom, and the stacks were packaged in aluminum kraft paper. The protective materials were conditioned in an arbitrary environment to achieve the equilibrium moisture content described in Table 3. The equilibrium moisture content was measured using the measurement method according to JIS P 8202 (1998). The above-mentioned packages were left to stand in a 35°C, 80% RH environment for 20 days, and each laminate was produced. Note that in the above laminates, all of the above-mentioned lithographic printing plate precursors were stacked with the support side facing down. The following evaluations were performed using the lithographic printing plate precursor that was in contact with the uppermost protective material of the obtained laminate via the interleaf paper. The resulting lithographic printing plate precursor was exposed using a Luxel® PLATESETTER T-6000III infrared semiconductor laser-equipped printer manufactured by Fujifilm Corporation under conditions of an outer drum rotation speed of 1,000 rpm, a laser output of 70%, and a resolution of 2,400 dpi. The exposed images included a solid image, a fine line image (a test chart in which the thickness of fine lines (fine line image areas in non-image areas) was varied in 2-μm increments from 4 μm to 30 μm), and a 50% halftone dot chart with a 20 μm dot FM screen. The resulting exposed plate precursor was mounted on the plate cylinder of a LITHRONE 26 printing press manufactured by Komori Corporation without development. Using a dampening solution of Ecology-2 (manufactured by Fujifilm Corporation) / tap water = 2 / 98 (volume ratio) and Values-G(N) black ink (manufactured by Dainippon Ink and Chemicals, Inc.), the dampening solution and ink were supplied using the standard automatic print start method of a LITHRONE 26, and on-press development was carried out. After that, 100 sheets were printed on Tokubishi Art paper (manufactured by Mitsubishi Paper Mills, ream weight: 76.5 kg) at a printing speed of 10,000 sheets per hour.

[0439] The 100th printed sheet was evaluated according to the following criteria: A: No stains in the non-image areas; B: No stains visible in the non-image areas, but visible using a 50x magnification loupe; C: Stain visible in part of the non-image areas; D: Stain visible in the entire non-image areas.

[0440] <Printing durability> The obtained lithographic printing plate precursor was exposed using a Luxel PLATESETTER T-6000III equipped with an infrared semiconductor laser manufactured by Fujifilm Corporation under the conditions of an outer drum rotation speed of 1,000 rpm, a laser output of 70%, and a resolution of 2,400 dpi. The exposed image included a solid image and a 50% halftone dot chart of a 20 μm dot FM (Frequency Modulation) screen. The obtained exposed lithographic printing plate precursor was mounted on the plate cylinder of a LITHRONE26 printing press manufactured by Komori Corporation without development processing. Using a dampening solution of Ecology-2 (manufactured by Fujifilm Corporation) / tap water = 2 / 98 (volume ratio) and Values-G(N) black ink (manufactured by DIC Corporation), the dampening solution and ink were supplied using the standard automatic printing start method of the LITHRONE 26, and on-press development was performed. 100 sheets were then printed on Tokubishi Art paper (ream weight: 76.5 kg, manufactured by Mitsubishi Paper Mills, Ltd.) at a printing speed of 10,000 sheets per hour. Printing was continued, and printing durability was evaluated based on the number of prints made at the point at which it was visually observed that the density of the solid image had begun to thin. The higher the number of prints, the better the printing durability.

[0441] <Visibility> The obtained lithographic printing plate precursor was exposed to light using a Trendsetter 3244VX manufactured by Creo Corporation equipped with a water-cooled 40 W infrared semiconductor laser under the conditions of an output of 11.5 W, an outer drum rotation speed of 220 rpm, and a resolution of 2,400 dpi (dots per inch, 1 inch = 25.4 mm). 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 in the SCE (specularly reflected light excluded) mode. The color development was measured using the L ＊ a ＊ b ＊ Color system L ＊ Using the value (brightness), the L ＊ value and L of the unexposed area ＊ The larger the ΔL value, the better the color development.

[0442] The evaluation results are shown in Tables 1 and 2.

[0443]

[0444]

[0445] In Table 2, "Somasif" represents inorganic layered compound dispersion (1). Details of the abbreviations in Tables 1 and 2 other than those described in the preparation method of each layer are shown below. Compounds 1 to 5, 7 to 13, 16, 21, 22, 25, and 31: sodium salts of the following borate anions Compound 32: sodium tetraphenylborate

[0446]

[0447] Here, Me represents a methyl group, and n-Bu represents an n-butyl group.

[0448]

[0449] I-1 to I-8: The following compounds

[0450]

[0451] IR-1 to IR-6: The following compounds. In addition, Me represents a methyl group.

[0452]

[0453] M-1: Urethane acrylate prepared by the following method

[0454] <Method of Producing 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-1) 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.

[0455] M-2 to M-4: the following compounds

[0456]

[0457] <Method for producing M-2>

[0458]

[0459] Bis(4-isocyanatophenyl)methane (12 mmol, 3.0 g), Compound A (25 mmol, 8.4 g), Neostan U-600 (15 mg), and 4-hydroxy TEMPO-free radical (1.0 mg) were added to methyl ethyl ketone (11 mL), and the mixture was reacted at 25° C. for 30 minutes, and then at 50° C. for 3 hours. Diisopropyl ether (33 mL) was added to the reaction solution, and the mixture was stirred at 25° C. for 1 hour. After that, the mixture was filtered under reduced pressure, and the residue was dried under reduced pressure to obtain 9.4 g of M-2.

[0460] <Method for producing M-3>

[0461]

[0462] Bis(4-isocyanatophenyl)methane (20 mmol, 5.0 g), compound B (44 mmol, 12 g), Neostan U-600 (26 mg), and 4-hydroxy TEMPO-free radical (1.7 mg) were added to methyl ethyl ketone (19 mL), and the mixture was reacted at 25° C. for 30 minutes, and then at 50° C. for 3 hours. Diisopropyl ether (57 mL) was added to the reaction solution, and the mixture was stirred at 25° C. for 1 hour. After that, the mixture was filtered under reduced pressure, and the residue was dried under reduced pressure to obtain 13 g of M-3.

[0463] <Method for producing M-4>

[0464]

[0465] Compound C (5.0 mmol, 2.7 g), dipentaerythritol pentaacrylate (10 mmol, 5.2 g), Neostan U-600 (100 mg), and 1,4-benzoquinone (14 mg) were added to THF (13 mL) and reacted at 25°C for 30 minutes, followed by a reaction at 60°C for 4 hours. Diisopropyl ether (39 mL) was added to the reaction solution, and the mixture was stirred at 25°C for 1 hour, after which the solvent was removed by decantation. After purification by column chromatography and drying under reduced pressure, 13 g of M-4 was obtained.

[0466] M-5: A polymerizable compound in a 2-butanone solution having a concentration of 80% by mass, obtained by reacting DESMODUR (registered trademark) N100 (the compound below) with hydroxyethyl acrylate and pentatritol acrylate in a molar ratio of 1:1.5:1.5.

[0467]

[0468] S-1 and S-2: The following compounds. Note that Me represents a methyl group.

[0469]

[0470]

[0471] The results shown in Tables 1 and 2 demonstrate that the lithographic printing plate precursors and laminates according to the examples have excellent on-machine developability over time. Furthermore, the lithographic printing plate precursors according to Examples 39 and 40 also have excellent stability against ozone due to the effects described in paragraphs 0155 to 0181 and 0371 to 0374.

[0472] The disclosures of Japanese Patent Application No. 2024-030660, filed on February 29, 2024, and Japanese Patent Application No. 2024-198463, filed on November 13, 2024, are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0473] 12a, 12b: aluminum support, 14: undercoat layer, 16: image recording layer, 18: aluminum plate, 20a, 20b: anodized film, 22a, 22b: micropores, 24: large diameter pore portion, 26: small diameter pore portion, D: depth of large diameter pore portion, 610: anodizing treatment device, 612: power supply tank, 614: electrolytic treatment tank, 616: aluminum plate, 618, 26: electrolyte, 620: power supply electrode, 622, 628: roller, 624: nip roller, 630: electrolytic electrode, 632: tank wall, 634: DC power source

Claims

1. An on-press development type lithographic printing plate precursor having a support and an image recording layer on the support, wherein the image recording layer contains an onium compound, a borate compound, and a polymerizable compound, and wherein a salt formed by pairing a cation moiety of the onium compound with an anion moiety of the borate compound has a solubility in 2-ethylhexyl methacrylate at 25°C of 0.01% by mass or more.

2. The on-press development type lithographic printing plate precursor according to claim 1, wherein the borate compound comprises a compound represented by the following formula (B1): In formula (B1), R Ｂ１ ~R Ｂ４ each independently represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted alkenyl group, or an unsubstituted or substituted alkynyl group; R Ｂ１ ~R Ｂ４ may each independently have a ring structure. Ｂ１ ~R Ｂ４ At least one of them is different from the others. ＋ represents a cation.

3. R ​​in the formula (B1) Ｂ１ ~R Ｂ３ 3. The on-press development type lithographic printing plate precursor according to claim 2, wherein at least two of the groups are phenyl groups and at least one is a substituted aryl group.

4. R in the formula (B1) Ｂ１ ~R Ｂ３ is a phenyl group, and R Ｂ４ The on-press development type lithographic printing plate precursor according to claim 2, wherein is an aryl group having a substituent.

5. R in the formula (B1) Ｂ４ The on-press development type lithographic printing plate precursor according to claim 4, wherein the total number of carbon atoms and oxygen atoms in the substituent is 3 or more.

6. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the onium compound is an iodonium compound or a sulfonium compound.

7. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the onium compound is a diaryl iodonium compound represented by the following formula (5) or (6): In formula (5) and formula (6), R ｉ５ ~R ｉ１４ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group; R ｉ５ ~R ｉ１４ At least two of X may be bonded to form a ring structure; － represents a counter anion.

8. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the polymerizable compound contains a polyfunctional (meth)acrylate having 6 or more functional groups.

9. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the polymerizable compound contains a polymerizable compound having an aromatic ring.

10. The on-press development type lithographic printing plate precursor according to claim 1 or 2, wherein the image recording layer contains an infrared absorber, and the infrared absorber is a cyanine dye represented by the following formula (7): In formula (7), 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.

11. The on-press development type lithographic printing plate precursor according to claim 10, wherein the infrared absorber is a compound represented by the following formula (8): In formula (8), 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.

12. The on-press development type lithographic printing plate precursor according to claim 11, wherein L in formula (8) is an oxygen atom.

13. The on-press developable lithographic printing plate precursor according to claim 1 or 2, wherein the support has an anodized film, and the micropores in the anodized film 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 average diameter of the large-diameter pores at the surface of the anodized film is 15 nm to 100 nm, and the average diameter of the small-diameter pores at the communicating positions is 15 nm or less.

14. The on-press developable lithographic printing plate precursor according to claim 1 or 2, wherein the support has an anodized film, and the micropores in the anodized film 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 on the surface of the anodized film is 35 nm or less, and the average maximum diameter of the large-diameter pores is 40 nm to 300 nm.

15. The on-press developable lithographic printing plate precursor according to claim 1 or 2, 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 nm to 500 nm and having micropores with an average diameter of 20 nm to 100 nm, a middle layer having a thickness of 100 nm 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 nm to 2,000 nm and having micropores with an average diameter of 15 nm or less.

16. A method for producing a lithographic printing plate, comprising the steps of: exposing the on-press development type lithographic printing plate precursor according to claim 1 or 2 in an imagewise manner; and supplying at least one selected from the group consisting of printing ink and fountain solution on the printing press to remove the image recording layer in the non-image areas.

17. A lithographic printing method comprising the steps of: exposing the on-press development type lithographic printing plate precursor according to claim 1 or 2 in an imagewise manner; supplying at least one selected from the group consisting of printing ink and fountain solution on the printing press to remove the image recording layer in the non-image areas to prepare a lithographic printing plate; and printing with the obtained lithographic printing plate.

18. A laminate comprising an on-press development type lithographic printing plate having an image recording layer laminated on a support, wherein the image recording layer contains an onium compound, a borate compound, and a polymerizable compound, wherein the solubility of a salt formed by a pair of a cation moiety of the onium compound and an anion moiety of the borate compound in 2-ethylhexyl methacrylate at 25°C is 0.01% by mass or more, and wherein the laminate has a protective material disposed at at least the uppermost part of the laminate for protecting the on-press development type lithographic printing plate, and wherein the saturated mass per unit area of ​​the protective material at 25°C and 30% RH is X (g / m ２ ), the saturated mass per unit area at 25°C and 80% RH is Y (g / m ２ ), the laminate satisfies the following formula (2): (Y-X) / Y≦0.06 (2) 19. The laminate according to claim 18, wherein the protective material is at least one material selected from the group consisting of thick paper, cardboard, laminated paper, plastic sheet, foam plastic sheet, and rubber sheet.

20. The laminate according to claim 18 or 19, wherein the protective material has a thickness of 100 μm or more.

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