Positive lithographic printing plate precursor and method for producing lithographic printing plate

Abstract

The present invention addresses the problem of providing a positive lithographic printing plate precursor and a method for producing a lithographic printing plate, said positive lithographic printing plate precursor having good development discrimination and having good brush resistance and image portion scratch resistance. The present invention provides a positive lithographic printing plate precursor and a method for making a lithographic printing plate using the positive lithographic printing plate precursor. The positive lithographic printing plate precursor comprises: a support; and an image recording layer formed from a positive photosensitive resin composition on the support. The positive photosensitive resin composition contains: a compound having at least one electron withdrawing group and at least one phenolic hydroxyl group in one molecule; an alkali soluble resin; and an infrared absorbent, wherein the electron withdrawing group does not include a sulfonyl group.

Description

Technical Field

[0001] This invention relates to a positive offset printing plate original and a method for manufacturing offset printing plates. Background Technology

[0002] Previously, various photosensitive compositions have been used as visible light image forming materials or lithographic printing plate materials. In particular, the development of lasers in the lithographic printing field in recent years has been significant, especially solid-state lasers or semiconductor lasers with near-infrared to infrared emission regions, which can now easily produce high-output and compact products. These lasers are very useful in the lithographic printing field as exposure light sources when directly creating plates based on digital data such as computer images.

[0003] Regarding the original positive offset printing plate for infrared lasers, the image forming layer contains alkali-soluble resin and infrared absorbers (e.g., infrared absorbing dyes, hereinafter also referred to as IR dyes) that absorb light and generate heat.

[0004] Regarding infrared absorbers, especially IR dyes, in the unexposed section, they function as development inhibitors that substantially reduce the solubility of the resin in the developer solution through interaction with the resin, thus becoming the image section of the lithographic printing plate. Furthermore, in the exposed section, due to the generated heat, the interaction between the IR dyes and the resin weakens, causing them to dissolve in the developer solution and become the non-image section, thereby forming the lithographic printing plate.

[0005] In positive offset printing plates, the greater the difference in solubility of the alkaline developer between the exposed and unexposed parts based on infrared lasers, the better the image forming performance is evaluated.

[0006] As a previous typeface printing plate original, the typeface printing plate originals described in Patent Document 1 and Patent Document 2 are known.

[0007] Patent Document 1 describes a lithographic printing plate original, which has two image recording layers on a support. The first layer, the lower layer, contains a first resin that is water-insoluble and alkali-soluble, and the second layer, the upper layer, contains a second resin containing a phenolic hydroxyl group that is water-insoluble and alkali-soluble, a photothermal conversion agent, and a group of compounds with a molecular weight of 800 or less containing at least one substituent such as a carboxylic acid group or a phenolic hydroxyl group that inhibits the dissolution of the second resin. Furthermore, the developability of the exposed and unexposed parts is significantly different.

[0008] Patent Document 2 describes a positive photosensitive composition containing an alkali-soluble organic polymer with phenolic hydroxyl groups, a photothermal conversion substance, at least one of a specific resin, and a low-molecular-weight compound with three phenolic hydroxyl groups, i.e., a dissolution inhibitor, and the unexposed portion has good alkali resistance to development.

[0009] Patent Document 1: Japanese Patent Application Publication No. 2004-287001

[0010] Patent Document 2: Japanese Patent No. 4081491

[0011] As required performance characteristics of a positive lithographic printing plate, good alkaline developability difference between exposed and unexposed areas, i.e., good development discrimination, is a given. Furthermore, the resulting lithographic printing plate exhibits good brush resistance and scratch resistance in the image area.

[0012] It is believed that in positive offset printing plates, reducing the solubility of the image area in alkaline developer to form a brush-resistant, i.e., a firm image area, and obtaining good alkaline developability in the non-image area are contradictory properties, making it difficult to achieve both simultaneously. Summary of the Invention

[0013] One embodiment of the present invention aims to solve the problem of providing a positive lithographic printing plate original with good development differentiation and good brush resistance and scratch resistance of the image area of ​​the obtained lithographic printing plate.

[0014] Another problem to be solved by an embodiment of the present invention is to provide a method for manufacturing a lithographic printing plate with good brush resistance and good developability of the non-image area.

[0015] The following methods are among the ways to solve the above problems.

[0016] <1> A positive offset printing plate original, which has the following characteristics:

[0017] Support body; and

[0018] The image recording layer formed of the positive photosensitive resin composition on the aforementioned support,

[0019] The above-mentioned positive photosensitive resin composition contains:

[0020] A compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule;

[0021] Alkali-soluble resins; and

[0022] Infrared absorber,

[0023] The electron-withdrawing groups mentioned above do not include sulfonyl groups.

[0024] <2> according to <1> The aforementioned positive offset printing plate original, wherein the electron-withdrawing group is selected from at least one of the group consisting of halogen atoms, trifluoromethyl, nitro, cyano, alkoxycarbonyl, acyloxy, amide, and alkylcarbonyl.

[0025] <3> according to <1> or <2> The original positive offset printing plate, wherein the compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is a compound having two or more phenolic hydroxyl groups in one molecule.

[0026] <4> according to <1> or <2> The aforementioned positive offset printing plate original, wherein the compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is a compound having three or more phenolic hydroxyl groups in one molecule.

[0027] <5> according to <1> to <3> The original positive offset printing plate according to any one of the following, wherein the electron-withdrawing group is an alkoxycarbonyl or an alkylcarbonyl.

[0028] <6> according to <1> to <5> The original positive lithographic printing plate according to any one of the above-mentioned compounds having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule comprises compounds selected from gallic ester compounds and compounds having multiple gallic ester sites in the same molecule.

[0029] <7> according to <1> to <6> The original positive lithographic printing plate according to any one of the above-mentioned compounds having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is a gallic ester compound.

[0030] <8> A positive offset printing plate original, which has the following characteristics:

[0031] Support body; and

[0032] The image recording layer on the support body

[0033] The image recording layer comprises a lower layer and an upper layer sequentially from the support side, and at least one of the lower layer and the upper layer is formed of a positive photosensitive resin composition.

[0034] The above-mentioned positive photosensitive resin composition contains:

[0035] A compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule;

[0036] Alkali-soluble resins; and

[0037] Infrared absorber,

[0038] The electron-withdrawing groups mentioned above do not include sulfonyl groups.

[0039] <9> according to <8> The original positive offset printing plate, wherein an undercoat layer is provided between the support and the image recording layer.

[0040] <10> according to <8> or <9> The aforementioned positive offset printing plate original, wherein the lower layer is formed from the aforementioned positive photosensitive resin composition, and the alkali-soluble resin contained in the lower layer comprises at least one selected from acrylic resins having sulfonamide groups on the side chain, acrylic resins having phenolic hydroxyl groups on the side chain, and phenolic varnish resins.

[0041] <11> according to <8> to <10> The positive lithographic printing plate original as described in any one of the above-mentioned positive photosensitive resin compositions, wherein the upper layer is formed from the above-mentioned positive photosensitive resin composition, the upper layer comprising an infrared absorber and a water-insoluble and alkali-soluble resin, wherein the water-insoluble and alkali-soluble resin is at least one selected from the group consisting of polyamide resin, epoxy resin, polyacetal resin, acrylic resin, methacrylic resin, polystyrene resin and phenolic varnish-type phenolic resin, wherein an interaction is formed between the polar groups of the water-insoluble and alkali-soluble resin and the infrared absorber.

[0042] <12> according to <9> The original positive offset printing plate, wherein the base coating comprises at least one selected from the group consisting of phosphonic acid having an amino group, organophosphonic acid, organophosphate, organophosphonic acid, amino acid and amine hydrochloride having a hydroxyl group.

[0043] <13> according to <8> to <12> The original positive lithographic printing plate according to any one of the following, wherein the upper layer further comprises a polymer having structural units having fluoroalkyl groups on their side chains.

[0044] <14> according to <8> to <12> The original positive lithographic printing plate according to any one of the above-mentioned upper and lower layers comprises a polymer having a structural unit represented by the following formula (I).

[0045] [Chemical Formula 1]

[0046]

[0047] In equation (I), R 11 and R 12 Each can be independently represented by a hydrogen atom or an alkyl group, R 13 L represents a hydrogen atom or a monovalent substituent. 11 and L 12 Each can be used to represent a single bond or a divalent linker, and Rh represents a substituent containing two or more silicon atoms.

[0048] <15> according to <14> The aforementioned positive offset printing plate original, wherein the upper layer comprises a polymer having the structural unit represented by the above formula (I).

[0049] <16> A method for manufacturing a lithographic printing plate, comprising, in sequence: an exposure process, and... <1> to <7> The original positive lithographic printing plate described in any one of the following steps is subjected to image exposure; and a developing process is performed by developing the exposed original positive lithographic printing plate using an alkaline aqueous solution with pH 8.5 to pH 13.5.

[0050] <17> A method for manufacturing a lithographic printing plate, comprising, in sequence: an exposure process, and... <8> to <15> The original positive lithographic printing plate described in any one of the following steps is subjected to image exposure; and a developing process is performed by developing the exposed original positive lithographic printing plate using an alkaline aqueous solution with pH 8.5 to pH 13.5.

[0051] Invention Effects

[0052] According to one embodiment of the present invention, a positive lithographic printing plate original with good development resolution and good brush resistance and scratch resistance of the image area can be provided.

[0053] According to another embodiment of the present invention, a method for manufacturing a lithographic printing plate with good brush resistance and good developability of the non-image portion is provided. Detailed Implementation

[0054] The present invention will now be described in detail. The description of the constituent elements described below is based on a representative embodiment of the present invention, but the present invention is not limited to this embodiment.

[0055] Furthermore, in this invention, the "~" indicating a numerical range is used to encompass the lower and upper limits of the numerical values ​​recorded before and after it.

[0056] Furthermore, in the marking of groups (atomic groups) in this invention, the markings that do not indicate whether they are substituted or unsubstituted include not only groups without substituents, but also groups with substituents. For example, "alkyl" includes not only alkyl groups without substituents (unsubstituted alkyl), but also alkyl groups with substituents (substituted alkyl).

[0057] Furthermore, in this invention, "mass%" and "weight%" have the same meaning, and "parts by mass" and "parts by weight" have the same meaning.

[0058] In this invention, the solid component included in the composition refers to the mass after removing volatile components such as solvents. For example, even liquid components such as low molecular weight monomers are included in the solid component.

[0059] In this invention, the term "process" 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 can be achieved.

[0060] Furthermore, in this invention, the combination of preferred methods is a more preferred method.

[0061] In this invention, unless otherwise specified, the molecular weight in the polymer component is the weight-average molecular weight (Mw) or number-average molecular weight (Mn) of polystyrene determined by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as solvent.

[0062] (Original positive offset printing plate)

[0063] The positive lithographic printing plate original of the present invention comprises: a support; and an image recording layer formed on the support by a positive photosensitive resin composition, wherein the positive photosensitive resin composition contains: a compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule; an alkali-soluble resin; and an infrared absorber, wherein the electron-withdrawing group does not include a sulfonyl group.

[0064] The electron-withdrawing group is preferably selected from at least one of the following groups: halogen atom, trifluoromethyl, nitro, cyano, alkoxycarbonyl, acyloxy, amide, and alkylcarbonyl.

[0065] Examples of halogen atoms include chlorine, bromine, fluorine, and iodine.

[0066] In the present invention, a compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is also referred to as a "specific compound".

[0067] Through in-depth research, the inventors discovered that in the positive lithographic printing plate original involved in this invention, the positive photosensitive resin composition contained in the image recording layer has good development resolution due to the presence of the aforementioned specific compounds, and the resulting lithographic printing plate has good brush resistance and scratch resistance of the image area.

[0068] Furthermore, in this invention, "the image recording layer formed from the positive photosensitive resin composition" refers to a layer formed from the dried product of the positive photosensitive resin composition. The dried product of the positive photosensitive resin composition can be obtained using a drying apparatus or by natural drying.

[0069] Although the detailed mechanism by which the above effects are achieved is not yet clear, the following is a hypothesis.

[0070] The specific compound contained in the image recording layer of the original positive offset printing plate according to the present invention has phenolic hydroxyl groups within its molecule, thus forming a quasi-crosslinked structure based on multi-point hydrogen bonds with the coexisting alkali-soluble resin. Therefore, in the unexposed area, the penetration and neutralization of the alkaline developer into the image recording layer is suppressed. On the other hand, in the exposed area, when the aforementioned multi-point hydrogen bonds are broken, the presence of the electron-withdrawing groups and phenolic hydroxyl groups of the original specific compound results in a low acidity (pKa) of the molecule, thereby acting as an alkali dissolution promoter.

[0071] Therefore, it is believed that specific compounds exhibit development-inhibiting effects in unexposed areas and development-promoting effects in exposed areas, thus resulting in good development resolution. Furthermore, it is believed that in unexposed areas, due to the strong interaction between phenolic hydroxyl groups and alkali-soluble resins, lithographic printing plates with excellent brush resistance can be obtained. This trend is believed to be further enhanced by the large number of phenolic hydroxyl groups and the low molecular weight of specific compounds.

[0072] Furthermore, the above-mentioned mechanism is a speculative mechanism and does not constitute any limitation on the present invention.

[0073] The positive photosensitive resin composition that forms the image recording layer of the positive lithographic printing plate original involved in this invention is also referred to simply as the positive photosensitive resin composition of this invention.

[0074] The following describes in detail the components contained in the positive photosensitive resin composition of the present invention.

[0075] <Specific compound>

[0076] The positive photosensitive resin composition contains a specific compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule.

[0077] Phenolic hydroxyl groups can be any hydroxyl group bonded to an aromatic ring. For example, they can be hydroxyl groups bonded to a benzene ring or hydroxyl groups bonded to a naphthalene ring formed by the fusion of two or more aromatic rings.

[0078] From the viewpoint of improving the developing differentiation of alkaline developer and the brush resistance of the obtained image, the specific compound is preferably a compound having two or more phenolic hydroxyl groups in one molecule, and more preferably a compound having three or more phenolic hydroxyl groups in one molecule.

[0079] A compound having two or more phenolic hydroxyl groups in one molecule refers to a compound having two or more hydroxyl groups directly bonded to one aromatic ring.

[0080] Regarding the electron-withdrawing group of a particular compound, in addition to sulfonyl groups, it is preferably selected from at least one group consisting of halogen atoms, trifluoromethyl, nitro, cyano, alkoxycarbonyl, acyloxy, amide, and alkylcarbonyl groups, which will be referred to below as specific electron-withdrawing groups. Hereinafter, examples of halogen atoms include chlorin, bromine, fluorine, and iodo groups.

[0081] The specific electron-withdrawing group is more preferably selected from at least one of the following groups: chlorine, bromine, trifluoromethyl, nitro, cyano, alkoxycarbonyl, acyloxy, amide, and alkylcarbonyl.

[0082] Furthermore, among the specific electron-withdrawing groups, from the viewpoint of more easily promoting the alkaline developability of the exposed portion, alkoxycarbonyl or alkylcarbonyl groups are more preferably preferred as specific electron-withdrawing groups in the specific compounds involved in the present invention.

[0083] A particular compound may have only one electron-withdrawing group or more than two. In the case of having more than two electron-withdrawing groups in a molecule, the electron-withdrawing groups may be the same as each other or different from each other. From the viewpoint of maintaining good solubility in the coating solvent used in the production of lithographic printing plates, it is preferable that the electron-withdrawing groups are different from each other.

[0084] The following describes specific examples of a particular compound, but the specific compound is not limited to the following specific examples.

[0085] <Specific examples of compounds having one phenolic hydroxyl group and one electron-withdrawing group within the molecule: specific compound group i>

[0086] [Chemical Formula 2]

[0087]

[0088] [Chemical Formula 3]

[0089]

[0090] <Specific examples of compounds having one phenolic hydroxyl group and two or more electron-withdrawing groups within the molecule: Specific compound group ii>

[0091] [Chemical Formula 4]

[0092]

[0093] [Chemical Formula 5]

[0094]

[0095] <Specific examples of compounds having one or two phenolic hydroxyl groups on the naphthalene ring and one or two electron-withdrawing groups: specific compound group iii>

[0096] [Chemical Formula 6]

[0097]

[0098] [Chemical Formula 7]

[0099]

[0100] <Specific examples of compounds having two phenolic hydroxyl groups and one or more electron-withdrawing groups: specific compound group iv>

[0101] [Chemical Formula 8]

[0102]

[0103] [Chemical Formula 9]

[0104]

[0105] <Specific examples of compounds having three or more phenolic hydroxyl groups and one or two electron-withdrawing groups: specific compound group v>

[0106] [Chemical Formula 10]

[0107]

[0108] [Chemical Formula 11]

[0109]

[0110] The specific examples described above all involve a single benzene ring or naphthalene ring having one or more phenolic hydroxyl groups and specific electron-withdrawing groups. However, specific compounds are not limited to these examples and can also be compounds with multiple aromatic rings containing phenolic hydroxyl groups and specific electron-withdrawing groups within the molecule. By having multiple aromatic rings containing phenolic hydroxyl groups and specific electron-withdrawing groups within the molecule, stronger alkali-resistant development properties based on multi-point hydrogen bonds are sometimes observed.

[0111] The following are specific examples of aromatic rings having multiple phenolic hydroxyl groups and specific electron-withdrawing groups.

[0112] <Specific examples of aromatic rings having multiple phenolic hydroxyl groups and specific electron-withdrawing groups: specific compound group vi>

[0113] [Chemical Formula 12]

[0114]

[0115] [Chemical Formula 13]

[0116]

[0117] [Chemical Formula 14]

[0118]

[0119] In the above, the specific compound preferably includes compounds selected from gallic acid ester compounds belonging to the specific compound group i and compounds having multiple gallic acid ester sites in the same molecule, and more preferably includes gallic acid ester compounds represented by the following structure.

[0120] [Chemical Formula 15]

[0121]

[0122] Positive photosensitive resin compositions may contain one specific compound alone or two or more.

[0123] From the viewpoint of improving the development resolution of the original lithographic printing plate and the brush resistance of the obtained lithographic printing plate, the content of the specific compound is preferably 0.05% to 30% by mass, more preferably 0.5% to 15% by mass, relative to the total solids content of the positive photosensitive resin composition.

[0124] Alkali-soluble resins

[0125] The positive photosensitive resin composition contains an alkali-soluble resin.

[0126] In this invention, "alkali-soluble" resin means that 0.01g of resin dissolves within 200 seconds in 5g of a sodium hydroxide aqueous solution at 30°C and pH 13.0. Furthermore, "dissolved" refers to a state where no visible residue remains after dissolution.

[0127] Examples of alkali-soluble resins include acrylic resins, phenolic varnish resins, polyurea, polyurethane, or polycarbonate.

[0128] From the viewpoint of further improving the resolution of development and the brush resistance, acrylic resin or phenolic varnish resin is preferred.

[0129] The preferred embodiments of the alkali-soluble resin involved in this invention will be described below.

[0130] [Acrylic resins]

[0131] As an alkali-soluble resin, compounds known in the field of positive offset printing plate originals can be used without particular limitation, but water-insoluble and alkali-soluble resins described in paragraphs 0025 to 0062 of Japanese Patent Application Publication No. 2008-151929 are preferred examples.

[0132] Among these, acrylic resins having sulfonamide groups on the side chain or acrylic resins having phenolic hydroxyl groups on the side chain are preferred.

[0133] -Acrylic resins with sulfonamide groups on their side chains-

[0134] Examples of acrylic resins having sulfonamide groups on their side chains include copolymers comprising monomer units formed from monomers having sulfonamide groups.

[0135] There are no particular limitations on the monomers containing sulfonamide groups, but examples include (meth)acrylamide compounds containing sulfonamide groups, (meth)acrylate compounds containing sulfonamide groups, and styrene compounds containing sulfonamide groups.

[0136] Specifically, examples include N-(p-toluenesulfonyl)acrylamide and N-(p-toluenesulfonyl)methylacrylamide.

[0137] The copolymer may also contain monomer units formed from other monomers. Examples of other monomers include known (meth)acrylate compounds, (meth)acrylamide compounds, acrylonitrile compounds, styrene compounds, etc., and monomers described in paragraphs 0034 to 0035 of Japanese Patent Application Publication No. 2008-151929 are preferred.

[0138] Furthermore, in this invention, the description of (meth)acrylate compounds, etc., refers to acrylate compounds or methacrylate compounds, etc.

[0139] -Acrylic resins with phenolic hydroxyl groups on their side chains-

[0140] Examples of acrylic resins having phenolic hydroxyl groups in their side chains include copolymers comprising monomer units formed from monomers having phenolic hydroxyl groups.

[0141] There are no particular limitations on the monomers having phenolic hydroxyl groups, but examples include (meth)acrylamide compounds, (meth)acrylate compounds, or hydroxystyrene compounds having phenolic hydroxyl groups. Specifically, N-(2-hydroxyphenyl)acrylamide, N-(3-hydroxyphenyl)acrylamide, N-(4-hydroxyphenyl)acrylamide, N-(2-hydroxyphenyl)methacrylamide, N-(3-hydroxyphenyl)methacrylamide, N-(4-hydroxyphenyl)methacrylamide, o-hydroxyphenyl acrylate, m-hydroxyphenyl acrylate, p-hydroxyphenyl acrylate, o-hydroxyphenyl methacrylate, m-hydroxyphenyl methacrylate, p-hydroxyphenyl methacrylate, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, ethyl 2-(2-hydroxyphenyl)acrylate, ethyl 2-(3-hydroxyphenyl)acrylate, ethyl 2-(4-hydroxyphenyl)acrylate, ethyl 2-(2-hydroxyphenyl)methacrylate, ethyl 2-(3-hydroxyphenyl)methacrylate, ethyl 2-(4-hydroxyphenyl)methacrylate, etc., are preferred.

[0142] The copolymers of the acrylic resins having sulfonamide groups on the side chains and the acrylic resins having phenolic hydroxyl groups on the side chains may also contain monomer units formed from other monomers. Examples of other monomers include known (meth)acrylate compounds, acrylonitrile compounds, allyl cyanide compounds, styrene compounds, etc., and the monomers described in paragraphs 0034 to 0035 of Japanese Patent Application Publication No. 2008-151929 are preferred.

[0143] The weight-average molecular weight of acrylic resins having sulfonamide groups on the side chain or having phenolic hydroxyl groups on the side chain is preferably greater than 5,000 and less than 300,000, more preferably 10,000 to 200,000.

[0144] The following examples illustrate acrylic resins having sulfonamide groups on their side chains or phenolic hydroxyl groups on their side chains, but are not limited thereto. In the following examples, the subscripts in parentheses representing monomer units indicate the content (mol%) of each monomer unit, Me represents methyl, and Ph represents phenyl.

[0145] [Chemical Formula 16]

[0146]

[0147] [Polyurea, polyurethane, polycarbonate]

[0148] Furthermore, polyurea, polyurethane, or polycarbonate can be preferably used as alkali-soluble resins.

[0149] Polyurea, polyurethane, or polycarbonate preferably have acidic groups, and from the viewpoint of brush resistance and developability, it is more preferably to have sulfonamide groups on the main chain.

[0150] Polyurea, polyurethane, or polycarbonate preferably have other acidic groups on their side chains. Phenolic hydroxyl, sulfonamide, or carboxyl groups are preferred as acidic groups on the side chains.

[0151] Regarding these alkali-soluble resins, the compounds described in paragraphs 0083 to 0114 of Japanese Patent Application Publication No. 2018-165797 can be cited as examples, and these descriptions can be referenced in this invention.

[0152] [Phenolic varnish resin]

[0153] Phenolic varnish resin is also a preferred choice as an alkali-soluble resin.

[0154] Phenolic varnish resins that can be used in the positive photosensitive resin compositions involved in this invention include, preferably, phenol-formaldehyde resin, m-cresol-formaldehyde resin, p-cresol-formaldehyde resin, m / p mixed cresol-formaldehyde resin, phenol / cresol (which may be any one of m, p, or m / p mixture) mixed formaldehyde resin, or pyrogallol-acetone resin.

[0155] Furthermore, as described in U.S. Patent No. 4,123,279, examples include condensation polymers of phenol and formaldehyde having alkyl groups with 3-8 carbon atoms, such as tert-butylphenol-formaldehyde resin and octylphenol-formaldehyde resin. The weight-average molecular weight (Mw) is preferably 500 or more, more preferably 1,000 to 700,000. The number-average molecular weight (Mn) is preferably 500 or more, more preferably 750 to 650,000. The dispersion (weight-average molecular weight / number-average molecular weight) is preferably 1.1 to 10.

[0156] As an alkali-soluble resin, there are no particular limitations as long as it has the property of dissolving upon contact with an alkaline developer. However, it is preferable that at least one of the main chain and side chains of the polymer has acidic functional groups such as sulfonic acid groups, phosphoric acid groups, sulfonamide groups, or reactive imide groups. Examples include resins containing 10 mol% or more of monomers having such acidic functional groups that impart alkali solubility, and more preferably resins containing 20 mol% or more. If the copolymer content of the monomers imparting alkali solubility is 10 mol% or more, sufficient alkali solubility and excellent developability can be obtained.

[0157] The alkali-soluble resin preferably has a weight-average molecular weight of 2,000 or more and a number-average molecular weight of 500 or more, more preferably a weight-average molecular weight exceeding 5,000 and below 300,000 and a number-average molecular weight of 800 to 250,000. Furthermore, the dispersibility (weight-average molecular weight / number-average molecular weight) of the other alkali-soluble resins mentioned above is preferably 1.1 to 10.

[0158] -content-

[0159] The alkali-soluble resin in the positive photosensitive resin composition involved in this invention can be used alone or in combination with two or more types.

[0160] Furthermore, the content of alkali-soluble resin in this invention is preferably 10% to 90% by mass relative to the total solid content of the positive photosensitive resin composition, more preferably 20% to 80% by mass, and even more preferably 30% to 80% by mass.

[0161] <Infrared absorber>

[0162] The positive photosensitive resin composition contains an infrared absorber.

[0163] As an infrared absorber, there are no particular restrictions on the use of any dye that absorbs infrared light and generates heat; various dyes known as infrared absorbers can be used.

[0164] As infrared absorbers that can be used in the present invention, examples include those described in paragraphs 0075 to 0085 of International Publication No. 2016 / 047392.

[0165] Among these dyes, particularly preferred dyes include anthocyanin, phthalocyanine, oxacyanine, squaric acid, pyranonium salts, thiopyranonium dyes, and nickel mercaptan complexes. Furthermore, when anthocyanin represented by formula (a) is used as the upper layer in the positive offset printing plate master according to the present invention, it exhibits good relief of exposure-based dissolution inhibition and excellent stability and economy, thus being the most preferred.

[0166] [Chemical Formula 17]

[0167]

[0168] In equation (a), X 1 Represents hydrogen atom, halogen atom, diarylamino, -X 2 -L 1 Or a group represented by the following formula (b). X 2 L represents an oxygen atom or a sulfur atom. 1This refers to a hydrocarbon group with 1 to 12 carbon atoms, an aromatic ring containing heteroatoms, or a hydrocarbon group with 1 to 12 carbon atoms containing heteroatoms. Here, heteroatoms refer to N, S, O, halogen atoms, or Se.

[0169] [Chemical Formula 18]

[0170]

[0171] In formula (b), Xa - With Za (described later) - The meaning is the same, R a It represents a substituent selected from the group consisting of hydrogen atoms, alkyl groups, aryl groups, substituted or unsubstituted amino groups, and halogen atoms.

[0172] R 21 and R 22 Each group independently represents a hydrocarbon group with 1 to 12 carbon atoms. From the perspective of the preservation stability of the original positive lithographic printing plate, R... 21 and R 22 Preferably, it has a hydrocarbon group with two or more carbon atoms, and more preferably R. 21 With R 22 They bond together to form 5-membered or 6-membered rings.

[0173] Ar 1 Ar 2 The groups can be the same or different, indicating that they can be aromatic hydrocarbon groups with substituents. Preferred aromatic hydrocarbon groups include benzene rings and naphthalene rings. Furthermore, preferred substituents include hydrocarbon groups with 1 to 12 carbon atoms, halogen atoms, and alkoxy groups with 1 to 12 carbon atoms.

[0174] Y 11 Y 12 They can be the same or different, representing dialkylmethylene groups with 3 to 12 sulfur or carbon atoms. R 23 and R 24 The substituents can be the same or different, indicating that they can be hydrocarbon groups with 1 to 20 carbon atoms. Preferred substituents include alkoxy, carboxyl, and sulfonyl groups with 1 to 12 carbon atoms.

[0175] R 25 R 26 R 27 and R 28 These can be the same or different, representing hydrocarbon groups with 1 to 12 hydrogen or carbon atoms. Considering the availability of raw materials, hydrogen atoms are preferred. Furthermore, Za... - This indicates the presence of counteracting anions. However, when the anthocyanin represented by formula (a) has anionic substituents within its structure and does not require neutralization charge, Za is not necessary.- From the perspective of preserving the stability of the original positive offset printing plate, the preferred Za... - The ions are halide ions, perchlorate ions, tetrafluoroborate ions, hexafluorophosphate ions, and arylsulfonate ions, with perchlorate ions, hexafluorophosphate ions, and arylsulfonate ions being particularly preferred.

[0176] Specific examples of anthocyanin pigments represented by formula (a) that can be preferably used include those described in paragraphs 0017 to 0019 of Japanese Patent Application Publication No. 2001-133969, paragraphs 0012 to 0038 of Japanese Patent Application Publication No. 2002-40638, and paragraphs 0012 to 0023 of Japanese Patent Application Publication No. 2002-23360. Anthocyanin dye A, as shown below, is particularly preferred as an infrared absorber.

[0177] [Chemical Formula 19]

[0178] Indigo dye A

[0179]

[0180] The content of the infrared absorber in the positive photosensitive resin composition is preferably 0.01% to 50% by mass, more preferably 0.1% to 30% by mass, and particularly preferably 1.0% to 30% by mass, relative to the total solid content of the positive photosensitive resin composition. If the content is 0.01% by mass or more, it results in high sensitivity, and if it is 50% by mass or less, the obtained layer has good uniformity and excellent durability.

[0181] <Acid-producing agent>

[0182] From the viewpoint of improving sensitivity to exposure, positive photosensitive resin compositions preferably contain an acid-generating agent.

[0183] In this invention, the acid-generating agent is a compound that produces acid due to light or heat, specifically a compound that decomposes and produces acid upon exposure to infrared radiation or heating to 100°C or higher. The produced acid is preferably a strong acid with a pKa of 2 or less, such as sulfonic acid or hydrochloric acid. The acid produced by this acid-generating agent increases the permeability of the developing solution to the exposed portion, and further improves the solubility of the exposed portion in an alkaline aqueous solution.

[0184] As an acid-generating agent preferably used in the positive photosensitive resin composition involved in this invention, examples include the acid-generating agents described in paragraphs 0116 to 0130 of International Publication No. 2016 / 047392.

[0185] From the perspective of sensitivity and stability, ononium salt compounds are preferred as acid-generating agents. The following is a description of ononium salt compounds.

[0186] As preferred onium salt compounds for use in the positive photosensitive resin compositions of the present invention, examples include compounds known to be produced by infrared exposure and by decomposition of compounds generated from the heat energy produced by the infrared absorber during exposure to produce acids. From the viewpoint of sensitivity, preferred onium salt compounds for the positive photosensitive resin compositions of the present invention include compounds having a known thermal polymerization initiator or having an onium salt structure as described below with a low bond dissociation energy.

[0187] Examples of ononium salts preferred for use in the positive photosensitive resin compositions of the present invention include known diazonium salts, iodonium salts, sulfonium salts, ammonium salts, pyridinium salts, azazine ononium salts, etc., among which sulfonates, carboxylates, and BF4 of triarylsulfonium or diaryliodonium are preferred. - PF6 - ClO4 - wait.

[0188] Examples of onium salts that can be used as acid-generating agents in the positive photosensitive resin compositions involved in this invention include onium salts represented by the following formulas (III) to (V).

[0189] [Chemical Formula 20]

[0190] Equation (III)

[0191] Formula (IV)

[0192] Formula (V)

[0193] In equation (III), Ar 11 and Ar 12 Each of the following groups independently represents an aryl group having 6 to 20 carbon atoms that can have substituents. Preferred substituents for this aryl group include halogen atoms, nitro groups, alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, or aryloxy groups having 1 to 12 carbon atoms. 11- It refers to the counter ion selected from the group consisting of sulfonate ions with fluorine atoms, such as halide ions, perchlorate ions, tetrafluoroborate ions, hexafluorophosphate ions, arylsulfonate ions, and perfluoroalkylsulfonate ions, preferably perchlorate ions, hexafluorophosphate ions, arylsulfonate ions, and perfluoroalkylsulfonate ions.

[0194] In equation (IV), Ar 21This indicates an aryl group having 6 to 20 carbon atoms that can have substituents. Preferred substituents include halogen atoms, nitro groups, alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, aryloxy groups having 1 to 12 carbon atoms, alkylamino groups having 1 to 12 carbon atoms, dialkylamino groups having 2 to 12 carbon atoms, arylamino groups having 6 to 12 carbon atoms, or diarylamino groups (each independently, the aryl group has 6 to 12 carbon atoms). 21- Indicates with Z 11- The same counter ion.

[0195] In equation (V), R 31 R 32 and R 33 These can be the same or different, indicating that the substituents can be hydrocarbon groups with 1 to 20 carbon atoms. Preferred substituents include halogen atoms, nitro groups, alkyl groups with 1 to 12 carbon atoms, alkoxy groups with 1 to 12 carbon atoms, or aryloxy groups with 1 to 12 carbon atoms. 31- Indicates with Z 11- The same counter ion.

[0196] In the positive photosensitive resin compositions of the present invention, specific examples of onium salts that can be preferably used are the same as those described in paragraphs 0121 to 0124 of International Publication No. 2016 / 047392.

[0197] Furthermore, as another example of the compounds represented by the above formulas (III) to (V), the compounds described in paragraphs 0036 to 0045 of Japanese Patent Application Publication No. 2008-195018 as examples of free radical polymerization initiators can preferably be used as acid-generating agents in the positive photosensitive resin compositions involved in the present invention.

[0198] As a more preferred example of an acid-generating agent that can be used in the positive photosensitive resin composition according to the present invention, compounds represented by the following formulas PAG-1 to PAG-5 can be cited. Furthermore, in formulas PAG-1 to PAG-5, Me represents methyl.

[0199] [Chemical Formula 21]

[0200]

[0201] When the positive photosensitive resin composition involved in this invention contains these acid-generating agents, these compounds can be used alone or in combination of two or more.

[0202] The content of the acid-generating agent, relative to the total solids content of the positive photosensitive resin composition, is in the range of 0.01% to 50% by mass, preferably in the range of 0.1% to 40% by mass, and more preferably in the range of 0.5% to 30% by mass. When the content is within the above range, the effect of adding the acid-generating agent, namely, the increase in sensitivity, and the suppression of residual film formation in the non-image area, are observed.

[0203] <Acid proliferation agent>

[0204] The positive photosensitive resin composition may contain an acid proliferation agent. In this invention, the acid proliferation agent refers to a compound substituted with residues of a relatively strong acid, and a compound that readily decomposes in the presence of an acid catalyst to generate a new acid. That is, it decomposes through an acid-catalyzed reaction to generate acid again. Adding one or more acids in a single reaction accelerates the increase in acid concentration as the reaction proceeds, thereby dramatically improving sensitivity. As the acid dissociation constant (pKa), the strength of the generated acid is preferably 3 or less, more preferably 2 or less. If the acid dissociation constant is 3 or less, a decomposition reaction based on the acid catalyst is easily induced.

[0205] Examples of acids used in such acid catalysts include dichloroacetic acid, trichloroacetic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, and benzenesulfonic acid.

[0206] The acid proliferation agents that can be used are the same as those described in paragraphs 0133 to 0135 of International Publication No. 2016 / 047392.

[0207] The content of these acid proliferation agents, relative to the total mass of the positive photosensitive resin composition, is in the range of 0.01% to 20% by mass, preferably in the range of 0.01% to 10% by mass, and more preferably in the range of 0.1% to 5% by mass. If the content of the acid proliferation agents is within the above range, the effect of adding acid proliferation agents can be sufficiently obtained, resulting in improved sensitivity to exposure and suppression of film strength reduction in the image region.

[0208] <Other Additives>

[0209] Positive photosensitive resin compositions may include developer accelerators, surfactants, baking agents / colorants, plasticizers, waxes, etc., as other additives. These can use the same additives as described in paragraphs 0138 to 0142 of International Publication No. 2016 / 047392.

[0210] <Composition ratio of each component>

[0211] Relative to the total solids content of the positive photosensitive resin composition involved in this invention, the content of specific compounds is preferably 0.05% to 30% by mass, the content of alkali-soluble resin is preferably 10% to 90% by mass, the content of infrared absorber is preferably 0.01% to 50% by mass, the content of acid-producing agent is preferably 0% to 50% by mass, the content of acid proliferator is preferably 0% to 20% by mass, the content of developer accelerator is preferably 0% to 20% by mass, the content of surfactant is preferably 0% to 5% by mass, the content of baking agent / colorant is preferably 0% to 10% by mass, the content of plasticizer is preferably 0% to 10% by mass, and the content of wax is preferably 0% to 10% by mass.

[0212] From the viewpoint that the positive photosensitive resin composition involved in the present invention can record with high sensitivity, has excellent image forming properties, and the formed image portion has good durability, the positive lithographic printing plate original involved in the present invention, having an image recording layer formed by the positive photosensitive resin composition, can produce a lithographic printing plate with excellent brush resistance.

[0213] (Structure of the original positive offset printing plate)

[0214] The positive offset printing plate original involved in this invention has an image recording layer containing the aforementioned positive photosensitive resin composition on a support having a hydrophilic surface.

[0215] The image recording layer can be a single layer or a multi-layer structure with a lower and upper layer near the support.

[0216] Furthermore, the image recording layer is an image recording layer having a lower layer and an upper layer sequentially from the support side. Preferably, at least one of the lower layer and the upper layer is a layer formed of a positive photosensitive resin composition, and more preferably, the lower layer and the upper layer are each formed of a positive photosensitive resin composition.

[0217] The image recording layer of the positive lithographic printing plate original involved in this invention can be formed by dissolving the components of the aforementioned positive photosensitive resin composition in a solvent, coating it onto a suitable support, and then curing it.

[0218] Examples of solvents used herein include, but are not limited to, dichloroethane, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate, ethyl lactate, N,N-dimethylacetamide, N,N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and toluene. These solvents may be used alone or in combination.

[0219] <Formation of the lower and upper layers>

[0220] Furthermore, the positive lithographic printing plate original involved in this invention is preferably a positive lithographic printing plate original having image recording layers having a lower layer and an upper layer sequentially on a support (hereinafter also referred to as "a double-layer image recording layer").

[0221] The lower and upper layers are preferably formed by separating them into two layers.

[0222] Methods for separating two layers include, for example, utilizing the difference in solvent solubility between the components contained in the lower layer and the components contained in the upper layer, or rapidly drying and removing the solvent after coating the upper layer. The latter method is preferred because it improves the separation between layers.

[0223] The following describes these methods in detail, but the method of coating two layers separately is not limited to these.

[0224] One method utilizes the difference in solvent solubility between the components in the lower layer and the components in the upper layer. A solvent system in which all components in the lower layer are insoluble when the upper layer is coated is used. Therefore, even with double-layer coating, each layer can be clearly separated to form a coating film. For example, as the lower layer component, a component insoluble in solvents such as methyl ethyl ketone or 1-methoxy-2-propanol (which dissolves the alkali-soluble resin in the upper layer) is selected. The lower layer is coated using a solvent system that dissolves the lower layer component and then dried. Subsequently, the upper layer, which is mainly composed of alkali-soluble resin, is dissolved in methyl ethyl ketone or 1-methoxy-2-propanol, coated, and dried, thereby achieving double-layer coating.

[0225] Next, as a method to dry the solvent very quickly after coating the second layer (upper layer), it can be achieved by blowing high-pressure air through a slit nozzle set approximately perpendicular to the direction of travel of the roll material, or by using a roller (heating roller) that supplies a heating medium such as steam to the inside to impart heat energy from the lower surface of the roll material by means of heat conduction, or a combination of these methods.

[0226] The specific compound is preferably contained in at least one of the lower and upper layers, more preferably in the upper layer only, and especially preferably in the lower layer only or in both the upper and lower layers.

[0227] The amount of the lower layer component coated on the support of the original positive offset printing plate involved in this invention after drying is preferably 0.5 g / m². 2 ~4.0g / m 2 Within the range, more preferably within 0.6 g / m 2 ~2.5g / m 2 Within the range. If it is 0.5g / m 2 The above indicates excellent brush resistance; if it is 4.0 g / m², then the brush resistance is excellent.2 The following results in excellent image reproducibility and sensitivity.

[0228] Furthermore, the coating weight of the upper layer component after drying is preferably 0.05 g / m². 2 ~1.0g / m 2 Within the range, more preferably within 0.08 g / m 2 ~0.7g / m 2 Within the range. If it is 0.05g / m 2 The above indicates excellent development tolerance and scratch resistance; if it is 1.0 g / m 2 The following parameters demonstrate excellent sensitivity.

[0229] The total coating weight after drying, including both the lower and upper layers, is preferably 0.6 g / m². 2 ~4.0g / m 2 Within the range, more preferably within 0.7 g / m 2 ~2.5g / m 2 Within the range. If it is 0.6g / m 2 The above indicates excellent brush resistance; if it is 4.0 g / m², then the brush resistance is excellent. 2 The following results in excellent image reproducibility and sensitivity.

[0230] <Upper Level>

[0231] The upper layer of the image recording layer in the double-layer structure of the present invention can be a layer formed by the positive photosensitive resin composition involved in the present invention, but preferably a layer formed by a resin composition other than the positive photosensitive resin composition involved in the present invention.

[0232] The upper layer of the double-layer image recording layer in this invention is preferably an infrared-sensitive positive image recording layer whose solubility in an alkaline aqueous solution is enhanced by heat.

[0233] There are no particular limitations on the mechanism by which the solubility of the upper layer in the alkaline aqueous solution is increased by heat; any method that includes a binder resin and improves the solubility of the heated area is acceptable. Examples of heat used for image formation include the heat generated when a lower layer containing an infrared absorber is exposed.

[0234] As an upper layer whose solubility in alkaline aqueous solution is improved by heat, preferred examples include layers containing alkali-soluble resins with hydrogen bonding such as phenolic varnish and urethane, layers containing water-insoluble and alkali-soluble resins and compounds with dissolution-inhibiting effects, and layers containing compounds capable of ablation.

[0235] More specifically, the preferred embodiment is as follows: the upper layer comprises an infrared absorber and a water-insoluble and alkali-soluble resin, wherein the water-insoluble and alkali-soluble resin is at least one selected from the group consisting of polyamide resin, epoxy resin, polyacetal resin, acrylic resin, methacrylic resin, polystyrene resin, and phenolic varnish-type phenolic resin, wherein the polar groups of the water-insoluble and alkali-soluble resin interact with the infrared absorber.

[0236] In the upper layer, by forming the above-mentioned interactions, the developability of the exposed part can be maintained, and the occurrence of undesirable ablation of the upper layer surface caused by exposure can be suppressed.

[0237] Furthermore, by adding an infrared absorber to the upper layer, the heat generated in the upper layer can be utilized for image formation. Examples of preferred structures for the upper layer containing the infrared absorber include a layer containing an infrared absorber, a water-insoluble and alkali-soluble resin, and a compound having a dissolution-inhibiting effect; and a layer containing an infrared absorber, a water-insoluble and alkali-soluble resin, and an acid-generating agent.

[0238] [Water-insoluble and alkali-soluble resin]

[0239] The upper layer of the double-layer image recording layer in this invention preferably contains a water-insoluble and alkali-soluble resin. By containing a water-insoluble and alkali-soluble resin, an interaction is formed between the infrared absorber and the polar groups of the water-insoluble and alkali-soluble resin, forming a layer with positive photosensitivity.

[0240] Common water-insoluble and alkali-soluble resins are described in detail below, among which, for example, polyamide resins, epoxy resins, polyacetal resins, acrylic resins, methacrylic resins, polystyrene resins, and phenolic varnish-type phenolic resins are preferred.

[0241] As for the above-mentioned water-insoluble and alkali-soluble resin, there are no particular limitations as long as it has the property of dissolving when in contact with alkaline developer. It is preferred to be a homopolymer, copolymer of the like, or mixture of the like in which at least one of the main chain and side chain of the polymer contains acidic groups.

[0242] As a water-insoluble and alkali-soluble resin having such an acidic group, it is preferable to have functional groups such as phenolic hydroxyl, carboxyl, sulfonic acid, phosphoric acid, sulfonamide, and reactive imide groups. Therefore, such a resin can be suitably produced by copolymerizing a mixture of monomers containing one or more olefinically unsaturated monomers having the above-mentioned functional groups. Regarding olefinically unsaturated monomers having the above-mentioned functional groups, in addition to acrylic acid and methacrylic acid, compounds and mixtures thereof represented by the following formula are preferably exemplified. Furthermore, in the following formula, R... 40 It represents a hydrogen atom or a methyl group.

[0243] [Chemical Formula 22]

[0244]

[0245] As the aforementioned water-insoluble and alkali-soluble resin, it is preferable to use a polymeric compound obtained by copolymerizing other polymeric monomers besides the aforementioned polymeric monomers. As the copolymerization ratio in this case, it is preferable to include alkali-soluble monomers such as monomers possessing functional groups such as phenolic hydroxyl groups, carboxyl groups, sulfonic acid groups, phosphate groups, sulfonamide groups, and reactive imide groups at a concentration of 10 mol% or more, and more preferably at a concentration of 20 mol% or more. If the copolymerization component of the alkali-soluble monomer is 10 mol% or more, sufficient alkali solubility and excellent developability can be obtained.

[0246] Other polymerizable monomers that can be used include the compounds listed below.

[0247] Alkyl acrylates or alkyl methacrylates, including methyl acrylate, ethyl acrylate, propyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. Acrylates and methacrylates containing aliphatic hydroxyl groups, such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate. Acrylamide, methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-phenylacrylamide, and other acrylamides or methacrylamides. Vinyl esters, including vinyl acetate, vinyl chloroacetate, vinyl butyrate, and vinyl benzoate. Styrene derivatives, including α-methylstyrene, methylstyrene, and chloromethylstyrene. Other nitrogen-containing monomers, such as N-vinylpyrrolidone, N-vinylpyridine, acrylonitrile, and methacrylonitrile. Maleimide derivatives include N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-phenylmaleimide, N-2-methylphenylmaleimide, N-2,6-diethylphenylmaleimide, N-2-chlorophenylmaleimide, N-cyclohexylmaleimide, N-laurylmaleimide, and N-hydroxyphenylmaleimide.

[0248] Among these other olefinic unsaturated monomers, (meth)acrylates, (meth)acrylamides, maleimides, and (meth)acrylonitriles are preferred.

[0249] Furthermore, phenolic varnish resins, which are other alkali-soluble resins, are preferably included as any component of the positive photosensitive resin composition involved in the present invention.

[0250] Furthermore, the above-mentioned water-insoluble and alkali-soluble resin can also be used in the positive photosensitive resin composition involved in this invention.

[0251] Furthermore, in the upper layer of the double-layer image recording layer in this invention, other resins can be used in combination without compromising the effect of the original positive offset printing plate involved in this invention. Regarding the upper layer itself, especially in the non-image areas, since alkali solubility is required, it is necessary to select a resin that does not impair this property. From this viewpoint, water-insoluble and alkali-soluble resins can be cited as examples of resins that can be used in combination. Common water-insoluble and alkali-soluble resins will be described in detail below, among which, for example, polyamide resins, epoxy resins, polyacetal resins, acrylic resins, methacrylic resins, polystyrene resins, and phenolic varnish-type phenolic resins are preferably included.

[0252] Furthermore, the amount of the mixture is preferably 50% by mass or less relative to the water-insoluble and alkali-soluble resins mentioned above.

[0253] The aforementioned water-insoluble and alkali-soluble resin preferably has a weight-average molecular weight of 2,000 or more and a number-average molecular weight of 500 or more, more preferably a weight-average molecular weight of 5,000 to 300,000 and a number-average molecular weight of 800 to 250,000. Furthermore, the dispersibility (weight-average molecular weight / number-average molecular weight) of the aforementioned water-insoluble and alkali-soluble resin is preferably 1.1 to 10.

[0254] The above-mentioned water-insoluble and alkali-soluble resins can be used alone or in combination with two or more.

[0255] The content of the water-insoluble and alkali-soluble resin relative to the total solid content of the upper layer of the double-layer image recording layer in this invention is preferably 2.0% to 99.5% by mass, more preferably 10.0% to 99.0% by mass, and even more preferably 20.0% to 90.0% by mass. If the content of the water-insoluble and alkali-soluble resin is 2.0% by mass or more, the image recording layer (photosensitive layer) has excellent durability, and if it is 99.5% by mass or less, both sensitivity and durability are excellent.

[0256] [Infrared absorber]

[0257] The aforementioned upper layer may contain an infrared absorber.

[0258] As an infrared absorber, there are no particular limitations as long as it is a dye that absorbs infrared light and generates heat, and the infrared absorber used in the aforementioned positive photosensitive resin composition of the present invention can be used in the same way.

[0259] The preferred dye is the cyanine dye represented by the above formula (a).

[0260] By including an infrared absorber in the upper layer, a positive offset printing plate with excellent image forming properties can be obtained.

[0261] The content of the infrared absorber in the upper layer is preferably 0.01% to 50% by mass, more preferably 0.1% to 30% by mass, and especially preferably 1.0% to 10% by mass, relative to the total solid content of the upper layer. By making the content 0.01% by mass or more, the sensitivity is improved, and if it is 50% by mass or less, the uniformity of the layer is good and the durability of the layer is excellent.

[0262] [surfactants]

[0263] From the viewpoint of improving the surface finish of the coating, the aforementioned upper layer preferably contains a surfactant.

[0264] Examples of surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and fluorinated surfactants. Surfactants can be used alone or in combination of two or more.

[0265] The nonionic surfactants used in this invention are not particularly limited, and conventionally known nonionic surfactants can be used. Examples include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrene phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerol fatty acid partial esters, dehydrated sorbitol fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol monofatty acid esters, sucrose fatty acid partial esters, polyoxyethylene dehydrated sorbitol fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerol fatty acid partial esters, polyoxyethylene castor oil, polyoxyethylene glycerol fatty acid partial esters, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, polyethylene glycol, and copolymers of polyethylene glycol and polypropylene glycol.

[0266] The anionic surfactant used in this invention is not particularly limited, and conventionally known anionic surfactants can be used. Examples include fatty acid salts, rosin salts, hydroxyl alkyl sulfonates, alkyl sulfonates, dialkyl sulfosuccinate salts, linear alkylbenzene sulfonates, branched alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, sodium N-methyl-N-oleoyl taurate, disodium N-alkyl sulfosuccinate monoamide, petroleum sulfonates, sulfated tallow, sulfated salts of fatty acid alkyl esters, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fatty acid monoglycerides sulfates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene styrene phenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ether phosphates, partially saponified products of styrene / maleic anhydride copolymers, partially saponified products of olefin / maleic anhydride copolymers, and naphthalene sulfonate formaldehyde condensates.

[0267] The cationic surfactant used in this invention is not particularly limited, and conventionally known cationic surfactants can be used. Examples include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.

[0268] The amphoteric surfactants used in this invention are not particularly limited, and conventionally known amphoteric surfactants can be used. Examples include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfates, and imidazolines.

[0269] In addition, among the surfactants mentioned above, "polyoxyethylene" can also be replaced with "polyoxyethylene" such as polyoxymethylene, polyoxypropylene, and polyoxybutylene. These surfactants can also be used in this invention.

[0270] As a further preferred surfactant, fluorinated surfactants containing perfluoroalkyl groups within the molecule can be cited as examples. Examples of such fluorinated surfactants include anionic types such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates; amphoteric types such as perfluoroalkyl betaines; cationic types such as perfluoroalkyl trimethylammonium salts; and nonionic types such as perfluoroalkyl amine oxides, perfluoroalkyl ethylene oxide additives, oligomers having perfluoroalkyl and hydrophilic groups, oligomers having perfluoroalkyl and lipophilic groups, oligomers having perfluoroalkyl, hydrophilic, and lipophilic groups, and urethanes having perfluoroalkyl and lipophilic groups. Furthermore, fluorinated surfactants described in Japanese Patent Application Publications Nos. 62-170950, 62-226143, and 60-168144 are also preferred examples.

[0271] Furthermore, in addition to the surfactants mentioned above, other surfactants may be added, without impairing the effects of the present invention, in order to expand the processing stability of the developing conditions of the present invention or to improve the coating properties, such as amphoteric surfactants described in Japanese Patent Application Publication No. 59-121044 and Japanese Patent Application Publication No. 4-13149; siloxane compounds described in EP950517; fluorinated monomer copolymers described in Japanese Patent Application Publication No. 11-288093; fluorinated surfactants described in Japanese Patent Application Publication No. 62-170950; and other surfactants.

[0272] Specific examples of amphoteric surfactants include alkyl di(aminoethyl)glycine, alkyl polyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethyl imidazoline betaine, or N-tetradecyl-N,N-betaine type (e.g., trade name "AMOGEN K": manufactured by DKS Co., Ltd.). As for siloxane compounds, block copolymers of dimethylsiloxane and polyepoxides are preferred. Specific examples include polyepoxide-modified silicones such as DBE-224, DBE-621, DBE-712, DBP-732, DBP-534 manufactured by CHISSO CORPORATION, and Tego Glide100 manufactured by Tego GmbH, Germany.

[0273] As specific examples of surfactants, the following surfactants can be cited as commercially available products.

[0274] In addition, "DOWSIL", "XIAMETER", and "SYLGARD" are registered trademarks. The following will omit the mention of "DOWSIL", "XIAMETER", and "SYLGARD" as registered trademarks.

[0275] Among the products manufactured by Dow Toray Co., Ltd., DOWSIL BY 16-205, DOWSIL BY16-849 Fluid, DOWSIL FZ-3710 Fluid, DOWSIL FZ-3760, DOWSIL FZ-3785, DOWSIL SF8417 Fluid, DOWSIL BY 16-891, DOWSIL FZ-3789, DOWSIL BY 16-839 Fluid, DOWSIL SF8411 Fluid, DOWSIL SF 8413Fluid, DOWSIL SF 8421 Fluid, DOWSIL BY 16-880 Fluid, DOWSIL BY 16-201, DOWSIL SF 8427 Fluid, DOWSIL SF 8428 Fluid, DOWSIL 580 WAX, DOWSIL BY 16-606, DOWSIL BY 16-846Fluid, XIAMETER OFX-0203Fluid, XIAMETER OFX-0230 Fluid, DOWSIL SF 8416 Fluid, DOWSIL SF 8419 Fluid, DOWSIL 501W Additive, DOWSIL FZ-2110, DOWSIL FZ-2123, DOWSIL L-7001, SYLGARD OFX-0309Fluid, XIAMETEROFX-5211 Fluid, DOWSIL SF 8410 Fluid, DOWSIL SH 3746Fluid, DOWSIL SH 8400Fluid, DOWSIL SH 8700 F1uid, DOWSIL SH 510 Fluid(100cSt, 500cSt), DOWSIL SH 550 Fluid, DOWSIL SH 710 Fluid, DOWSIL FS 1265 Fluid, etc. can be cited.

[0276] Shin-Etsu Chemical Co., Ltd. in Shin-Etsu Silicone (note commercial title) products include KP-124, KP-109, KP-110, KP-121, KP-118, KP-341, KP-112, KP-125, KP-101, KP-106, KP-120, KP-105, KP-104, KP-611, KP-626, KP-327, KP-323, KP-322, KP-625, KP-623, KP-624, KP-620, KP-651, KP-652, KP-650, KP-310, KP-306, KP-301, KP-621, KP-369, KP-368, KP-126, etc., KF series and FL series such as KF-868, KF-865, KF-864, KF-859, KF-393, KF-860, KF-880, KF-8004, KF-8002, KF-8005, KF-867, KF-8021, KF-869, KF-861, KF-877, KF-101, KF-1001, KF-102, KF-1002, KF-1005, KF-2001, KF-2004, KF-99, KF-9901, PAM-E, K F-8010, KF-8012, KF-8008, KF-105, KF-6000, KF-6001, KF-6002, KF-6003, KF-6123, KF-9701, KF-2012, KF-857, KF-862, KF-858, KF-35 1A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-644, KF-6020, KF-6204, KF-6011, KF-6012, KF- 6015, KF-6017, KF-410, FL-5, FL-100-100cs, FL-100-450cs, FL-100-1,000cs, FL-100-10,000cs, KF-412, KF-413, KF-414, KF-415, KF -4003, KF-4701, KF-4917, KF-7235B, KF-3935, KF-50-100cs, KF-50-300cs, KF-50-1,000cs, KF-50-3,000cs, KF-53, KF-54, KF-6004, etc.

[0277] Among BYK's products, the following models can be cited: BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315N, BYK-320, BYK-322, BYK-323, BYK-325N, BYK-326*, BYK-327*, BYK-330, and BYK-331. BYK-333, BYK-342, BYK-345 / 346, BYK-347, BYK-348, BYK-349, BYK-370, BYK-375, B YK-377, BYK-378, BYK-3450*, BYK-3451*, BYK-3455, BYK-3456*, BYK-3760*, BYK-UV 3500, BYK-UV 3505*, BYK-UV 3510, BYK-UV 3530, BYK-UV 3535*, BYK-UV 3570, BYK-UV 3575*, BYK-UV 3576, BYK-350, BYK-354, BYK-355 / 356 acrylic copolymer, BYK-358N / 361N, BYK-381 acrylic copolymer, BYK-392 acrylic copolymer, BYK-394 acrylic copolymer, BYK-3441 acrylic copolymer, BYK-399, BYK-3440*, BYK-3550, BYK-3560*, BYK-3565*, BYK-3566*, BYK-SILCLEAN3700, BYK-SILCLEAN 3701*, BYK-SILCLEAN 3720, BYK-DYNWET 800N, etc.

[0278] [Other ingredients]

[0279] In addition, the upper layer of the image recording layer in the double-layer structure may contain acid-producing agents, acid proliferation agents, development accelerators, baking agents, colorants, plasticizers, waxes, etc.

[0280] Furthermore, in a dual-layer image recording layer, to adjust the dissolution rate of the image recording layer, a development accelerator can be included not only in the upper layer but also in the lower layer. That is, a development accelerator can be included in at least one of the upper and lower layers, or it can be included in both the upper and lower layers.

[0281] Examples of development promoters include acid anhydrides, phenols, and organic acids, such as sulfonium salt A (b-1), sulfonium salt B (b-2), phenolic compound (a-2), and phenolic compound (c-1) in the examples described later.

[0282] These components can be used in the same way as those used in the aforementioned positive photosensitive resin compositions of the present invention, preferably in the same manner.

[0283] The upper layer preferably further comprises a polymer having structural units having fluoroalkyl groups on their side chains.

[0284] The upper layer contains a polymer with structural units having fluoroalkyl groups on the side chains, which improves the surface finish of the coating when the upper layer is applied, thereby enhancing the ink acceptability of the image area in the offset printing plate.

[0285] Examples of polymers having structural units with fluoroalkyl groups on their side chains include the following compounds.

[0286] The following compounds are available as commercially available products, such as fluorinated surfactants (MEGAFACE F-782F, DIC CORPORATION).

[0287] [Chemical Formula 23]

[0288]

[0289] Furthermore, it is preferable that at least one of the above-mentioned upper layer and the lower layer described below contains a polymer having a structural unit represented by the following formula (I), and more preferably that the upper layer contains a polymer having a structural unit represented by the following formula (I).

[0290] Furthermore, from the viewpoint of improving the coating surface appearance during top coating and the ink acceptability of the image area in offset printing plates, polymers with siloxane bonds on the side chains are preferred, in addition to polymers having structural units with fluoroalkyl groups on the side chains. As a specific example, a polymer in which the fluoroalkyl structural units of the above-mentioned structure are replaced with structural units having three-branched siloxane structures can be cited.

[0291] As a structural unit with a 3-branched siloxane structure, the following structural units can be cited.

[0292] [Chemical Formula 24]

[0293]

[0294] As a polymer that changes the fluoroalkyl structural unit of a polymer having a fluoroalkyl structural unit on the side chain to a structural unit having a 3-branched siloxane structure, examples of polymers can be given below.

[0295] [Chemical Formula 25]

[0296]

[0297] There are no particular limitations on the main chain backbone of polymers having structural units containing fluoroalkyl groups on their side chains and polymers having siloxane bonds on their side chains; examples include acrylic acid backbones and methacrylic acid backbones. The main chain backbones of the structural units constituting the polymer can be the same as or different from each other.

[0298] [Chemical Formula 26]

[0299]

[0300] In equation (I), R 11 and R 12 Each can be independently represented by a hydrogen atom or an alkyl group, R 13 L represents a hydrogen atom or a monovalent substituent. 11 and L 12 Each can be used to represent a single bond or a divalent linker, and Rh represents a substituent containing two or more silicon atoms.

[0301] As a result of R 11 and R 12 Examples of alkyl groups include linear alkyl groups with 1 to 18 carbon atoms, branched alkyl groups with 3 to 18 carbon atoms, and cyclic alkyl groups. Specifically, examples of such alkyl groups include methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, and cyclohexyl.

[0302] As R 11 and R 12 All of them are preferably hydrogen atoms.

[0303] As a result of R 13 The monovalent substituent can be represented by, for example, alkyl, alkenyl, or aryl.

[0304] By L 11 Examples of divalent bonding groups include -C(=O)-O- (the so-called ester bond) or -C(=O)-NH-.

[0305] Additionally, by L 11 The divalent linking group is preferably -C(=O)-O-, which is an ester bond.

[0306] By L 12 The divalent linking group indicated is any group capable of linking L... 11 There are no particular restrictions on the groups and Rh. As for L... 12 Examples of divalent linking groups include alkylene groups. Preferably, the alkylene group has 2 to 10 carbon atoms, and more preferably has 4 to 8 carbon atoms.

[0307] As a substituent containing two or more silicon atoms represented by Rh, there is no particular limitation as long as the atomic group constituting the substituent contains two or more silicon atoms. From the viewpoint of machine reproducibility, substituents containing two or more silicon atoms preferably contain silicon atoms as silicon-oxygen bonds (Si-O bonds). Substituents containing two or more silicon atoms preferably have two or more silicon-oxygen bonds, more preferably three or more, and even more preferably three to twelve. Substituents containing two or more silicon atoms preferably contain silicon-oxygen bonds as a polysiloxane structure.

[0308] Furthermore, from the viewpoint of machine developability, substituents containing two or more silicon atoms preferably have a branched structure, and more preferably have a branched structure with silicon atoms as the central branch.

[0309] As a substituent containing two or more silicon atoms, it is particularly preferred to contain two or more groups with structures represented by the following formula (BIa).

[0310] [Chemical Formula 27]

[0311]

[0312] In the above formula (BIa), * represents the bonding position, R b11 R b12 and R b13 Each can be independently represented as alkyl, alkenyl, aryl, or alkylene aryl.

[0313] As a result of R b11 R b12 and R b13 Examples of alkyl groups include linear alkyl groups with 1 to 18 carbon atoms, branched alkyl groups with 3 to 18 carbon atoms, and cyclic alkyl groups. Specifically, examples of such alkyl groups include methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, and cyclohexyl.

[0314] As a result of R b11 R b12 and R b13 Examples of alkenyl groups that can be represented include alkenyl groups with 2 to 12 carbon atoms. Specifically, examples of alkenyl groups include vinyl, 1-propenyl, 1-butenyl, 1-methyl-1-propenyl, 1-cyclopentenyl, and 1-cyclohexenyl.

[0315] As a result of R b11 R b12 and R b13 The aryl group can be represented by, for example, aryl groups with 6 to 12 carbon atoms. Specifically, examples of the aforementioned aryl groups include phenyl, α-methylphenyl, and naphthyl groups.

[0316] As a result of Rb11 R b12 and R b13 The alkylene aryl group is represented by, for example, alkylene aryl groups with 7 to 30 carbon atoms.

[0317] In formula (BIa), R b11 R b12 and R b13 Each component is preferably an alkyl group, more preferably all of the same alkyl group, even more preferably all of the alkyl groups having 1 to 4 carbon atoms, and especially preferably all of the alkyl groups being methyl.

[0318] Substituents containing two or more silicon atoms are preferably groups containing three or more of the structure represented by the above formula (BIa), and more preferably groups containing three to six of the structure.

[0319] Substituents containing two or more silicon atoms are preferably groups represented by the following formula (Ba2).

[0320] [Chemical Formula 28]

[0321]

[0322] In the above formula (Ba2), * represents the bonding position, R b1 R b2 and R b3 Each can be independently represented as alkyl, alkenyl, aryl, or alkylene aryl.

[0323] As a result of R b1 R b2 and R b3 Examples of alkyl groups include linear alkyl groups with 1 to 18 carbon atoms, branched alkyl groups with 3 to 18 carbon atoms, and cyclic alkyl groups. Specifically, examples of such alkyl groups include methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, and cyclohexyl.

[0324] As a result of R b1 R b2 and R b3 Examples of alkenyl groups that can be represented include alkenyl groups with 2 to 12 carbon atoms. Specific examples of alkenyl groups include vinyl, 1-propenyl, 1-butenyl, 1-methyl-1-propenyl, 1-cyclopentenyl, and 1-cyclohexenyl.

[0325] As a result of R b1 R b2 and R b3 The aryl group can be represented by, for example, aryl groups with 6 to 12 carbon atoms. Specifically, examples of the aforementioned aryl groups include phenyl, α-methylphenyl, and naphthyl groups.

[0326] As a result of Rb1 R b2 and R b3 The alkylene aryl group is represented by, for example, alkylene aryl groups with 7 to 30 carbon atoms.

[0327] In formula (Ba2), R b1 R b2 and R b3 Each component is preferably an alkyl group, more preferably all of the same alkyl group, even more preferably all of the alkyl groups having 1 to 4 carbon atoms, and especially preferably all of the alkyl groups being methyl.

[0328] As a specific example of the structural unit represented by formula (I), monomers represented by K-1 to K-12 can be cited. Specific examples of monomer units forming structural units having substituents containing two or more silicon atoms on the side chain are not limited to this.

[0329] In the following structure, n is an integer from 2 to 1000.

[0330] [Chemical Formula 29]

[0331]

[0332] From the viewpoint of obtaining better coating surface properties, the structural unit represented by formula (I) is preferably a copolymer containing structural units having substituents containing two or more silicon atoms on the side chain and structural units having hydrophilic groups on the side chain.

[0333] The structural unit having hydrophilic groups contained in the structural unit represented by formula (I) on the side chain is preferably a structural unit represented by the following formula (Ba4).

[0334] [Chemical Formula 30]

[0335]

[0336] In formula (Ba4), R B7 and R B8 Each can be independently represented by a hydrogen atom or an alkyl group, R B9 L represents a hydrogen atom or a monovalent substituent. B2 It represents -C(=O)-O- or -C(=O)-NH-, L B2 and L B3 Indicates a single bond or a divalent linkage group, X B This indicates a hydrophilic group.

[0337] As a result of R B7 and R B8Examples of alkyl groups include linear alkyl groups with 1 to 18 carbon atoms, branched alkyl groups with 3 to 18 carbon atoms, and cyclic alkyl groups. Specifically, examples of such alkyl groups include methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, and cyclohexyl.

[0338] As R B7 and R B8 All of them are preferably hydrogen atoms.

[0339] As a result of R B9 The monovalent substituent can be represented by, for example, alkyl, alkenyl, or aryl. The aforementioned alkyl, alkenyl, and aryl groups are respectively reacted with R... B11 R B12 and R B13 The alkyl, alkenyl, and aryl groups are represented by the same terms, and the preferred methods are also the same.

[0340] As R B9 Preferably, it contains hydrogen atoms or methyl groups.

[0341] By L B3 The divalent linker indicated is only required to be able to link L B2 and X B There are no particular restrictions on the groups involved. As a group composed of L... B3 Examples of divalent linking groups include alkylene groups. Preferably, the alkylene group has 2 to 10 carbon atoms, and more preferably has 4 to 8 carbon atoms.

[0342] By X B Examples of hydrophilic groups include hydroxyl groups, phosphate groups, polyalkoxide groups, or groups formed by combining two or more of these. Here, examples of polyalkoxide groups include polyethoxyl, polypropoxyl, polybutoxyl, or groups formed by combining these.

[0343] Specific examples of monomer units used to form structural units having hydrophilic groups on their side chains include monomers represented by H-1 to H-40. Specific examples of monomer units forming structural units having hydrophilic groups on their side chains are not limited to these.

[0344] In the following structure, n and m are independent integers from 2 to 100.

[0345] In the following structure, the term "random" refers to the random arrangement of multiple polyalkoxide groups.

[0346] [Chemical Formula 31]

[0347]

[0348] [Chemical Formula 32]

[0349]

[0350] A polymer having a structural unit represented by formula (I) (hereinafter also referred to as polymer A) may contain one structural unit having a substituent having two or more silicon atoms on its side chain, or may contain two or more substituents.

[0351] In polymer A, the content of structural units having substituents containing two or more silicon atoms on the side chains relative to the mass of polymer A can be 100% by mass, preferably 15% to 70% by mass, more preferably 20% to 60% by mass, and even more preferably 25% to 50% by mass.

[0352] Furthermore, polymer A may contain only one structural unit with a hydrophilic group on its side chain, or it may contain two or more structural units.

[0353] In polymer A, the content of structural units having hydrophilic groups on the side chains is preferably 30% to 85% by mass relative to the mass of polymer A, more preferably 40% to 80% by mass, and even more preferably 50% to 75% by mass.

[0354] In addition, polymer A may contain other structural units.

[0355] Other structural units include, for example, structural units having a carboxylic acid group on their side chain. Examples of structural units having a carboxylic acid group on their side chain include (meth)acrylic acid, itaconic acid, and itaconic acid derivatives. Structural units having a carboxylic acid group on their side chain are preferably included as structural units different from those having the aforementioned hydrophilic groups on their side chain.

[0356] Other structural units include alkyl (meth)acrylates (alkyl groups have 1 to 24 carbon atoms), styrene derivatives, maleic anhydride, maleimide anhydride, (meth)acrylonitrile, vinyl ether derivatives, and alkyl (meth)acrylamide derivatives.

[0357] In polymer A, the content of other structural units relative to the mass of polymer A is preferably 0% to 20% by mass.

[0358] From the viewpoint of obtaining an image recording layer with excellent planar properties, the weight-average molecular weight of polymer A is preferably 5,000 to 100,000, and more preferably 8,000 to 60,000.

[0359] Specific examples of polymer A include BP-1 to BP-10 as shown below. However, specific examples of polymer A are not limited to these.

[0360] [Chemical Formula 33]

[0361]

[0362] The content of polymer A relative to the total mass of the image recording layer coating liquid is preferably set to 0.001% to 0.1% by mass, more preferably 0.002% to 0.01% by mass.

[0363] Furthermore, unless otherwise specified, the term "lithographic printing plate original" in this invention refers to both the single-layer image recording layer and the multi-layer image recording layer with a lower and upper layer structure. Also, unless otherwise specified, the term "image recording layer" refers to both the single-layer and multi-layer image recording layers.

[0364] Through in-depth research, the inventors discovered that by adopting the above-described structure, it is possible to provide a lithographic printing plate with an excellent image recording layer having a coating surface.

[0365] Although the detailed mechanism by which the above effects are achieved is not yet clear, the following is a hypothesis.

[0366] It is believed that in the first embodiment described above, the (meth)acrylic acid polymer contained in the image recording layer, which has substituents containing two or more silicon atoms on its side chain, tends to be biased towards the surface when forming the image recording layer due to the structure of the side chain, thereby contributing to the surface smoothness of the image recording layer.

[0367] Furthermore, it is believed that the polymer containing the structural unit represented by the above formula (I) in the image recording layer is prone to be biased towards the surface when forming the image recording layer due to the structure of the side chain, thereby contributing to the surface smoothness of the image recording layer.

[0368] It is speculated that, as a result, unevenness is not easily visually discernible when the surface is viewed, thus allowing for the acquisition of an image recording layer with excellent coating surface texture.

[0369] <Lower Level>

[0370] The lower layer of the image recording layer in the double-layer structure of the present invention is preferably a layer containing the positive photosensitive resin composition involved in the present invention.

[0371] Furthermore, the lower layer of the image recording layer in the double-layer structure of the present invention is preferably formed by coating the positive photosensitive resin composition involved in the present invention.

[0372] By using the positive photosensitive resin composition involved in this invention as a lower layer, printing plates with excellent image forming properties or brush resistance can be obtained.

[0373] Furthermore, by using the positive photosensitive resin composition involved in this invention as the lower layer, the brush resistance is improved.

[0374] Although the detailed mechanism for achieving the effects described above is not yet clear, it is speculated that the brush resistance in printing depends mainly on the film strength of the resin used in the underlying layer. Therefore, it is presumed that the brush resistance is improved by using the positive photosensitive resin composition of the present invention, which has high film strength, in the underlying layer due to the strong interaction between the adhesives (hydrogen bonds, etc.).

[0375] From the viewpoint of improving brush resistance, the alkali-soluble resin contained in the lower layer preferably includes at least one selected from acrylic resins having sulfonamide groups on the side chain, acrylic resins having phenolic hydroxyl groups on the side chain, and phenolic varnish resins.

[0376] It is believed that by including the aforementioned alkali-soluble resin in the lower layer, the interactions (hydrogen bonds, etc.) between the adhesives are strong, which helps to improve the film strength, resulting in better brush resistance.

[0377] When the positive photosensitive resin composition of the present invention is used as the upper layer, it is preferable that the lower layer is also formed of the positive photosensitive resin composition of the present invention. However, it is also possible to use a resin composition other than the positive photosensitive resin composition of the present invention to form the lower layer. In this case, the preferred method for the lower layer is the same as the preferred method for the upper layer described above.

[0378] It is believed that by also including a polymer having structural units represented by the aforementioned formula (I) in the lower layer, the surface appearance of the coating film in the lower layer can be further improved.

[0379] <Support Body>

[0380] As for the support used in the original positive offset printing plate involved in this invention, there are no particular restrictions as long as it is a plate-shaped object with the required strength and durability and dimensional stability. The same support described in paragraphs 0166 to 0169 of International Publication No. 2016 / 047392 can be used.

[0381] In the above description, an aluminum support body is particularly preferred, and an aluminum support body that has undergone hydrophilic treatment is even more preferred.

[0382] <Undercoat>

[0383] The original positive offset printing plate involved in this invention preferably has an undercoat layer between the support having a hydrophilic surface and the image recording layer.

[0384] Various organic compounds can be used as components of the base coating, such as carboxymethyl cellulose, dextrin and other amino-containing phosphonic acids, organophosphonic acids, organophosphoric acids, organosphinic acids, amino acids, and amine hydrochlorides containing hydroxyl groups. Furthermore, one of these base coating components can be used alone, or two or more can be used in combination. Details of the compounds used in the base coating and the method for forming the base coating are described in paragraphs 0171 to 0172 of Japanese Patent Application Publication No. 2009-175195, and these descriptions also apply to this invention.

[0385] For example, the base coating preferably comprises at least one of the following groups: phosphonic acid having an amino group, organophosphonic acid, organophosphate, organophosphonic acid, amino acid and hydrochloride of amine having a hydroxyl group.

[0386] The aforementioned compounds may be included as part of the structure of a polymer. For example, polymers with the following structures may be cited.

[0387] [Chemical Formula 34]

[0388]

[0389] The preferred coating amount for the base coat is 2 mg / m³. 2 ~200mg / m 2 More preferably 5 mg / m 2 ~100mg / m 2 If the coating amount is within the above range, sufficient brush resistance can be obtained.

[0390] <Back Coating>

[0391] As needed, a back coating is provided on the back side of the support of the original positive offset printing plate according to the present invention. As this back coating, a coating layer formed from metal oxides obtained by hydrolysis and condensation of the organic polymer compound described in Japanese Patent Application Publication No. 5-45885 and the organic or inorganic metal compound described in Japanese Patent Application Publication No. 6-35174 is preferably used. Among these coating layers, silicon alkoxy compounds such as Si(OCH3)4, Si(OC2H5)4, Si(OC3H7)4, and Si(OC4H9)4 are inexpensive and readily available, and the metal oxide coating layers obtained therefrom exhibit excellent resistance to developer, therefore they are particularly preferred.

[0392] (Method for making offset printing plates)

[0393] The method for manufacturing the lithographic printing plate involved in this invention includes, in sequence, an exposure step, which exposes the original positive lithographic printing plate involved in this invention to an image; and a development step, which develops the exposed original positive lithographic printing plate using an alkaline aqueous solution with pH 8.5 to pH 13.5.

[0394] According to the method for manufacturing a lithographic printing plate of the present invention, a fine image can be formed by means of excellent development resolution, thereby obtaining a lithographic printing plate with excellent brush resistance.

[0395] As described above, the method for producing the lithographic printing plate of the present invention can also be applied to positive lithographic printing plate originals having a single-layer image recording layer or multiple-layer image recording layers.

[0396] The following describes in detail each step of the method for manufacturing the offset printing plate involved in this invention.

[0397] <Exposure Process>

[0398] The method for manufacturing a lithographic printing plate according to the present invention includes an exposure step of exposing an image to a positive lithographic printing plate original. The details are identical to those described in paragraphs 0173 to 0175 of International Publication No. 2016 / 047392.

[0399] <Developing Process>

[0400] The method for manufacturing a lithographic printing plate according to the present invention includes a developing step of developing the plate using an alkaline aqueous solution with pH 8.5 to pH 13.5 (hereinafter also referred to as "developing solution").

[0401] The developing solution used in the developing process is an aqueous solution with a pH of 8.5 to 13.5, more preferably an alkaline aqueous solution with a pH of 12 to 13.5.

[0402] Furthermore, the developer preferably contains a surfactant, more preferably at least an anionic surfactant or a nonionic surfactant. Surfactants help improve processability.

[0403] The surfactant used in the above-mentioned developing solution can be any of anionic, nonionic, cationic, and amphoteric surfactants, but as mentioned above, anionic or nonionic surfactants are preferred.

[0404] The anionic, nonionic, cationic, and amphoteric surfactants used in the developing solution of the method for manufacturing the lithographic printing plate according to the present invention can be the surfactants described in paragraphs 0128 to 0131 of Japanese Patent Application Publication No. 2013-134341.

[0405] Furthermore, from the viewpoint of stable solubility or turbidity in water, the HLB (Hydrophile-Lipophile Balance) value is preferably 6 or higher, and more preferably 8 or higher.

[0406] The surfactants used in the above-mentioned developing solutions are preferably anionic surfactants and nonionic surfactants, and are particularly preferred to be anionic surfactants containing sulfonic acid or sulfonate and nonionic surfactants having aromatic rings and ethylene oxide chains.

[0407] Surfactants can be used alone or in combination.

[0408] The surfactant content in the developer is preferably 0.01% to 10% by mass, more preferably 0.01% to 5% by mass.

[0409] To maintain the developer solution at a pH of 8.5–13.5, carbonate and bicarbonate ions are present as buffers. This suppresses pH fluctuations even with prolonged use, preventing decreased developability and the formation of developer residues caused by pH changes. To ensure the presence of carbonate and bicarbonate ions in the developer solution, carbonates and bicarbonates can be added. Alternatively, carbonates and bicarbonates can be generated by adjusting the pH after adding carbonates or bicarbonates. There are no particular limitations on the carbonates and bicarbonates, but alkali metal salts are preferred. Examples of alkali metals include lithium, sodium, and potassium, with sodium being particularly preferred. These can be used alone or in combination of two or more.

[0410] The total amount of carbonates and bicarbonates relative to the total mass of the developer is preferably 0.3% to 20% by mass, more preferably 0.5% to 10% by mass, and particularly preferably 1% to 5% by mass. If the total amount is 0.3% by mass or more, the developability and processing capacity will not decrease. If it is less than 20% by mass, it is difficult to form precipitates or crystals, and therefore, it is difficult to gel during neutralization when treating developer waste, thereby suppressing the possibility of causing obstacles to waste treatment.

[0411] Ideally, the drying process should be performed continuously or discontinuously after the developing process. Drying can be carried out using hot air, infrared rays, far-infrared rays, etc.

[0412] As an automatic processing machine preferably used in the method for producing a lithographic printing plate according to the present invention, an apparatus having a developing section and a drying section is used to develop and coat a positive lithographic printing plate in a developing tank, and then dry it in a drying section to obtain a lithographic printing plate.

[0413] Furthermore, to improve brush resistance and other properties, the developed printing plate can be heated under very strong conditions. This heating treatment is also known as the post-heating process.

[0414] From the viewpoint of the desired image enhancement effect or the suppression of thermal decomposition of the image section, the heating temperature in the post-heating process is preferably in the range of 200°C to 500°C.

[0415] The resulting lithographic printing plate is then mounted on an offset printing press and is suitable for multi-sheet printing.

[0416] Example

[0417] The present invention will now be described in detail through embodiments. The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments can be appropriately modified without departing from the spirit of the embodiments of the present invention. Therefore, the scope of the embodiments of the present invention is not limited to the specific examples shown below. Furthermore, in this embodiment, unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass".

[0418] [Examples 1 to 27, Comparative Examples 1 to 11]

[0419] <Preparation of Specific Compounds>

[0420] The specific compounds involved in this invention are available as commercially available products. These specific compounds are available, for example, as reagents or chemicals from companies such as Tokyo Chemical Industry Co., Ltd., FUJIFILM Wako Pure Chemical Corporation, Sigma-Aldrich, and KANTO KAGAKU.

[0421] <Fabrication of the Support Body>

[0422] A support for a lithographic printing plate was manufactured by performing the processes (Aa) to (Ak) shown below on an aluminum alloy plate of material 1S with a thickness of 0.3 mm. In addition, a water washing process was performed between all processing steps, and the liquid was drained by rollers after the water washing process.

[0423] (Aa) Mechanical roughening treatment (brushing method)

[0424] Pumice powder suspension (specific gravity 1.1 g / cm³) 3 While being supplied to the surface of the aluminum plate as a grinding slurry, it undergoes mechanical roughening treatment via a rotating beam brush.

[0425] The median particle size (μm) of the abrasive material was set to 30μm, the number of brushes was set to 4, and the brush rotation speed (rpm: revolutions per minute, the same below) was set to 250rpm. The bristle material of the bristle-planting brush was 6.10 nylon, with a bristle diameter of 0.3mm and a bristle length of 50mm. The brush was densely packed with bristles through holes drilled in a φ300mm stainless steel sleeve. The distance between the two support rollers (φ200mm) at the bottom of the bristle-planting brush was 300mm. The load on the drive motor that pressed the bristle-planting brush until it rotated was increased by 10kW relative to the load before pressing the bristle-planting brush against the aluminum plate. The rotation direction of the brush was the same as the movement direction of the aluminum plate.

[0426] (Ab) Alkali Etching Treatment

[0427] Etching was performed on the aluminum plate obtained above by spraying a caustic soda aqueous solution with a concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass using a nozzle at a temperature of 70°C. Afterwards, a spray water wash was performed. The aluminum dissolution rate was 10 g / m². 2 .

[0428] (Ac) Descaling in acidic aqueous solution

[0429] Next, a descaling treatment was performed in a nitric acid aqueous solution. The nitric acid aqueous solution used for the descaling treatment was waste liquid of nitric acid used for electrochemical roughening in the next process. The liquid temperature was 35°C. The descaling treatment was performed for 3 seconds by spraying the descaling liquid with a sprayer.

[0430] (Ad) Electrochemical roughening treatment

[0431] Electrochemical roughening was performed continuously using a 60Hz AC voltage via nitric acid electrolysis. The electrolyte used was an aqueous solution of 10.4 g / L nitric acid at 35°C, with aluminum nitrate added to adjust the aluminum ion concentration to 4.5 g / L. A rectangular trapezoidal AC wave with a duty cycle of 1:1 and a current time (tp) of 0.8 msec from zero to peak value was used as the AC power supply waveform, with a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode. The current density, measured at peak current, was 30 A / dm³. 2 This causes 5% of the current flowing from the power source to be diverted to the auxiliary anode. (Electricity (C / dm³)) 2 The total charge when using an aluminum plate as the anode is 185 C / dm. 2 After that, it was spray-washed.

[0432] (Ae) Alkali etching treatment

[0433] Etching was performed on the aluminum plate obtained above by spraying a caustic soda aqueous solution with a concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass using a nozzle at a temperature of 50°C. Afterwards, a spray water wash was performed. The aluminum dissolution rate was 0.5 g / m³. 2 .

[0434] (Af) Descaling in acidic aqueous solution

[0435] Next, a descaling treatment was performed in an aqueous sulfuric acid solution. The sulfuric acid solution used for the descaling treatment had a sulfuric acid concentration of 170 g / L and an aluminum ion concentration of 5 g / L. The solution temperature was 30°C. The descaling solution was sprayed using a sprayer for 3 seconds to remove the ash.

[0436] (Ag) Electrochemical roughening treatment

[0437] Electrochemical roughening was performed continuously using hydrochloric acid electrolysis at a 60Hz AC voltage. The electrolyte was an aqueous solution at 35°C with 6.2 g / L hydrochloric acid, to which aluminum chloride was added to adjust the aluminum ion concentration to 4.5 g / L. A trapezoidal rectangular wave AC current was used, with a current-to-peak time (tp) of 0.8 msec, a duty ratio of 1:1, and a carbon electrode as the counter electrode. Ferrite was used as the auxiliary anode.

[0438] The current density, measured in peak current, is 25 A / dm. 2 The amount of electricity generated during hydrochloric acid electrolysis (C / dm³) 2 The total charge when using an aluminum plate as the anode is 63 C / dm. 2 After that, it was spray-washed.

[0439] (Ah) Alkali etching treatment

[0440] Etching was performed on the aluminum plate obtained above by spraying a caustic soda aqueous solution with a concentration of 5% by mass and an aluminum ion concentration of 0.5% by mass using a nozzle at a temperature of 50°C. Afterwards, a spray water wash was performed. The aluminum dissolution rate was 0.1 g / m³. 2 .

[0441] (Ai) Ash removal treatment in acidic aqueous solution

[0442] Next, a descaling treatment was performed in an aqueous sulfuric acid solution. Specifically, the waste liquid generated during the anodizing process (containing 5 g / L of dissolved aluminum ions in a 170 g / L aqueous sulfuric acid solution) was used for a 4-second descaling treatment at a liquid temperature of 35°C. A 3-second descaling treatment was then performed by spraying the descaling solution with a sprayer.

[0443] (Aj) Anodizing treatment

[0444] Anodizing was performed using a two-stage power supply electrolysis process (each of the first and second electrolysis sections is 6m long, each of the first and second power supply sections is 3m long, and each of the first and second power supply electrode sections is 2.4m long). Sulfuric acid was used as the electrolyte supplied to both the first and second electrolysis sections. The electrolyte concentration was 50g / L (containing 0.5% by mass aluminum ions), and the temperature was 20°C. Afterwards, a spray-washing process was performed.

[0445] (Ak) Silicate treatment

[0446] To ensure the hydrophilicity of the non-image area, a silicate treatment was performed by immersion in a 2.5% by mass aqueous solution of sodium silicate No. 3 at 50°C for 7 seconds. The Si adhesion amount was 10 mg / m². 2 After that, it was spray-washed.

[0447] <Formation of the base coating>

[0448] After applying the primer coating liquid 1 as shown below to the support prepared above, dry it at 80°C for 15 seconds to set the primer coating as the support. The coating amount after drying is 15 mg / m². 2 .

[0449] [Primer Coating Liquid 1]

[0450] • 0.3 parts of the following copolymers with a weight-average molecular weight of 28,000.

[0451] Methanol: 100 parts

[0452] Water: 1 part

[0453] [Chemical Formula 35]

[0454]

[0455] In the above chemical formulas, the subscripts in parentheses indicate the content (mass%) of each structural unit.

[0456] <Formation of Image Recording Layer>

[0457] On the obtained support, a coating liquid composition (I) for forming the lower layer, consisting of the following components, is applied using a wire rod and dried in a drying oven at 150°C for 40 seconds to achieve a coating weight of 1.0 g / m². 2 The lower layer is thus formed. On the surface of the lower layer, an upper layer forming coating liquid composition (II) of the following composition is applied using a wire rod to form the upper layer. After applying the upper layer, it is dried at 150°C for 40 seconds to obtain a total coating weight of 1.2 g / m² for both the lower and upper layers. 2 The original offset printing version.

[0458] [Coating liquid composition (I) for lower layer formation]

[0459] • N-(4-aminosulfonylphenyl)methacrylamide / acrylonitrile / methyl methacrylate copolymer (copolymer ratio: 32 / 36 / 32; weight average molecular weight 50,000): 2.5 parts

[0460] • 0.4 parts of p-cresol phenolic varnish

[0461] • Specific or comparative compounds with the following structures (compounds listed in Tables 1 to 7): Amounts listed in Tables 1 to 7

[0462] • Infrared absorber (IR dye (I): structure below): 0.2 parts

[0463] Tetrahydrophthalic anhydride (THPA): 0.3 parts or none (listed in Tables 1 to 7)

[0464] • p-Toluenesulfonic acid (p-TsO): 0.02 parts or none (listed in Tables 1 to 7)

[0465] ·3-Methoxy-4-diazodiphenylamine hexafluorophosphate: 0.1 parts

[0466] • A compound in which the counterion of ethyl violet is changed to 6-hydroxynaphthalenesulfonic acid: 0.15 parts

[0467] Fluorinated surfactant (MEGAFACE F-780F, DIC CORPORATION, structural reference (e-1)): 0.01 parts

[0468] • Silicone-based surface conditioner (BYK-300, BYK JAPAN KK): 0.01 parts or none (listed in Tables 1 to 7)

[0469] • Siloxane-based surface conditioners (additives (e-2) below): 0.01 parts or none (listed in Tables 1 to 7)

[0470] · Methyl ethyl ketone: 30 parts

[0471] ·1-Methoxy-2-butyrolactone: 15 parts

[0472] γ-Butyrolactone: 15 parts

[0473] [Chemical Formula 36]

[0474] (Specific compound)

[0475]

[0476] [Chemical Formula 37]

[0477] (Specific compound)

[0478] [Chemical Formula 38]

[0479] (Compare compounds)

[0480]

[0481] [Chemical Formula 39]

[0482]

[0483] [Coating liquid composition (II) for upper layer formation]

[0484] • Phenolic varnish resin (m-cresol / p-cresol / phenol = 3 / 2 / 5, Mw 8,000): 0.68 parts

[0485] • Ethyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (copolymer ratio: 50 / 20 / 30; weight average molecular weight 42000): 0.16 parts

[0486] • Infrared absorber (IR dye (I): structure as described above): 0.045 parts

[0487] · Methyl ethyl ketone: 15.0 parts

[0488] ·1-Methoxy-2-propanol: 30.0 parts

[0489] • Sulfonate A (with the following structure: b-1): 0.16 parts

[0490] • Sulfonate B (with the following structure: b-2): 0.16 parts

[0491] Fluorinated surfactants (MEGAFACE F-782F, DIC CORPORATION, structural reference (d-1)): 0.01 parts or none

[0492] • Siloxane-based surfactants (compounds with structures (d-2) to (d-6) below): 0.01 parts or none

[0493] • Additives with the following structures (compounds listed in Tables 1 to 7): Amounts (parts) listed in Tables 1 to 7

[0494] In the following structural formula, the composition ratio of each structural unit is set to 100% by weight. MW represents the weight-average molecular weight.

[0495] [Chemical Formula 40]

[0496]

[0497] [Chemical Formula 41]

[0498]

[0499] [Chemical Formula 42]

[0500]

[0501] In addition, in Tables 1 to 7, the numerical values ​​of the content represent parts by mass, and "-" indicates that the compound is not present.

[0502] Using the original offset printing plates of each of the obtained embodiments and comparative examples, the following evaluations were performed, and the results are recorded in Tables 1 to 7 below.

[0503] <Evaluation of the solubility resistance of the image area and the development time of the non-image area>

[0504] For the original positive offset printing plate in each embodiment and comparative example, the test pattern was drawn as an image using a Trendsetter VX manufactured by Creo Corporation with a beam intensity of 9W and a roller speed of 150rpm.

[0505] Then, it was immersed in a developing bath containing developer XP-D (a developer diluted to a conductivity of 42 mS / cm) manufactured by FUJIFILM Corporation, and the time from the start of dissolution of the image part and the time required for development of the non-image part were measured at a developing temperature of 28°C.

[0506] The time from the start of dissolution of the image section is defined as the time until the measured optical density (OD value) in the image section decreases by 0.05 from the measured optical density in the image section before development. Furthermore, the immersion time during which the difference between the measured optical density in the non-image section and the measured optical density of the aluminum support is 0.02 or less is defined as the development time for the non-image section. Optical density was measured using a SpectroEye spectrophotometer manufactured by GretagMacbeth.

[0507] The longer the time from the onset of dissolution of the image area, the better the tolerance to alkaline aqueous solutions. Furthermore, the shorter the development time of the non-image area, the better the solubility of the non-image area in alkaline aqueous solutions, and the better the developability (highlight reproducibility) of the alkaline aqueous solution. Therefore, in positive offset printing plates, the longer the onset time of dissolution of the image area, the shorter the development time of the non-image area, and the greater the difference between the onset time of dissolution of the image area and the development time of the non-image area, the better the developability. In the following tables, the above differences are recorded as "development discrimination".

[0508] It can be said that the shorter the development time of the non-image section, the better it is at suppressing the aforementioned residual colors.

[0509] The results are shown in Tables 1 through 7.

[0510] <Evaluation of scratch resistance>

[0511] The obtained lithographic printing plate original was scratched using a scratch tester manufactured by HEIDON, with a load applied by a sapphire needle (tip diameter 1.0 mm). Afterwards, the image was exposed using a Creo Trendsetter 3244 with a beam intensity of 9.0 W and a drum speed of 150 rpm.

[0512] Using a FUJIFILM Corporation PS processor LP940H containing FUJIFILM Corporation developer DT-2 (diluted 1:8) and FUJIFILM Corporation Finisher FG-1 (diluted 1:1), development was performed at 30°C for 12 seconds. The conductivity of the developer at this time was 43 mS / cm.

[0513] The maximum load (g) at which no scratches appear on the developed lithographic printing plate is taken as the scratch resistance value. A higher value indicates better scratch resistance.

[0514] The evaluation is that a scratch resistance of 7 or higher is a level that is not a problem in practical use, preferably 8 or higher, and more preferably 10 or higher.

[0515] The results are shown in Tables 1 through 7 below.

[0516] <Brush resistance rating>

[0517] For the original positive offset printing plate in each embodiment and comparative example, the test pattern was drawn as an image using a Trendsetter manufactured by Creo Corporation with a beam intensity of 9W and a roller speed of 150rpm.

[0518] Using a FUJIFILM Corporation-manufactured PS processor LP940H equipped with FUJIFILM Corporation-manufactured developer XP-D (a developer diluted to a conductivity of 43 mS / cm), development of the non-image areas was performed at a development temperature of 30°C and a development time of 12 seconds. Continuous printing was performed using a Komori Corporation-manufactured LITHRONE printing press. Toyo Ink Tokuren Black Ink, a low-grade material containing calcium carbonate, was used as the ink. Brush resistance was evaluated by visually determining the number of prints that could maintain sufficient ink concentration. The higher the number of prints, the better the brush resistance. The results are shown in Tables 1 to 7.

[0519] <Evaluation of Coating Surface Texture>

[0520] The original lithographic printing plate was processed to a size of 40cm × 62cm. The surface of the outermost layer of the obtained sample was visually observed under white light illumination of 750–1500 Lux, and the surface appearance was evaluated according to the following criteria. The results are shown in Tables 1–7.

[0521] -Benchmark-

[0522] A: No unevenness was visually discernible across the entire surface.

[0523] B: Slight unevenness can be visually detected in certain areas.

[0524] C: Slight localized unevenness can be visually identified in a region wider than B.

[0525] <Evaluation of Ink Application>

[0526] The original positive lithographic printing plates from each embodiment and comparative example were loaded into the plate supply device and subjected to fully automatic continuous exposure. Developing was performed using the aforementioned developer, and the plates were then discharged into the plate stacker. The exposure resolution was 2,400 dpi (dots per inch, 1 inch = 2.54 cm) and 175 lines, with dot gain varying from 0.5% to 99.5%. The obtained lithographic printing plates were printed using an R201 printing press manufactured by Manrol and Co., Ltd., and DAICURE ABILIO ink manufactured by DIC Graphics Corporation. Visual inspection confirmed that no areas of un-inked printing were present, and the number of prints required to achieve this was used as an indicator of ink adhesion. The fewer prints required for ink adhesion, the better the ink adhesion was considered. Evaluations were conducted according to the following criteria, and the results are recorded in Tables 1 to 7.

[0527] [Evaluation Criteria]

[0528] 1: The number of prints required for inking is less than 15.

[0529] 2: The number of prints required for inking is more than 15 but less than 30.

[0530] 3: The number of prints required for inking exceeds 30.

[0531] [Table 1]

[0532]

[0533] [Table 2]

[0534]

[0535] [Table 3]

[0536]

[0537] [Table 4]

[0538]

[0539] [Table 5]

[0540]

[0541] [Table 6]

[0542]

[0543] [Table 7]

[0544]

[0545] According to the results in Tables 1 to 7, the original positive lithographic printing plates of the various embodiments of the present invention have good development differentiation and can obtain high-precision images. The obtained lithographic printing plates have excellent brush resistance and scratch resistance.

[0546] Based on the results of Example 2, the use of propyl gallate containing the specific compound (a-2) yielded good results. Furthermore, based on the results of Examples 2 through 6, it is evident that good results can be obtained regardless of the content of the specific compound.

[0547] Furthermore, based on the comparison between Example 2 and Examples 21, 22 to 26, it can be seen that by using fluorinated surfactants or siloxane-based surface modifiers, especially by using fluorinated surfactants or siloxane-based surfactants and siloxane-based surface modifiers (e-2) in the upper layer, the development resolution and scratch resistance become even better.

[0548] Comparisons between Comparative Examples 2 to 7 and the various embodiments show that, even compounds containing phenolic hydroxyl groups in one molecule, compared to positive lithographic printing plates having an image recording layer formed from a positive photosensitive resin composition using a compound that does not have electron-withdrawing groups or a compound that has electron-withdrawing groups other than specific electron-withdrawing groups, the development resolution, brush resistance, and scratch resistance of the image area of ​​the various embodiments are better.

[0549] [Examples 28-55, Comparative Examples 12-22]

[0550] In Example 1 above, except that the lower layer forming coating liquid composition (I) was changed to the lower layer forming coating liquid composition (III) described below, the lithographic printing plate original of Example 28 was obtained in the same manner and evaluated in the same manner as in Example 1. Furthermore, lithographic printing plate originals of Examples 28 to 55 and Comparative Examples 12 to 22 were prepared according to the formulations containing the lower layer forming coating liquid composition (III) and the upper layer forming coating liquid composition (II) in the types and amounts described in Tables 8 to 14 below.

[0551] In addition, in Tables 8 to 14, the numerical values ​​of the content represent parts by mass, and "-" indicates that the compound is not present.

[0552] The same evaluation as in Example 1 was performed using the original offset printing plates of each of the obtained embodiments and comparative examples. The results are recorded in Tables 8 to 14 below.

[0553] [Coating liquid composition (III) for lower layer formation]

[0554] • N-(4-aminosulfonylphenyl)methacrylamide / acrylonitrile / methyl methacrylate copolymer (copolymer ratio: 32 / 36 / 32; weight average molecular weight 50,000): 2.5 parts

[0555] • 0.4 parts of p-cresol phenolic varnish

[0556] • Specific or comparative compounds with the following structures (compounds listed in Tables 8 to 14): Amounts listed in Tables 8 to 14

[0557] • Infrared absorber (IR dye (I): structure below): 0.2 parts

[0558] Tetrahydrophthalic anhydride (THPA): 0.3 parts or none (listed in Tables 8 to 14)

[0559] • p-Toluenesulfonic acid (p-TsO): 0.02 parts or none (listed in Tables 8 to 14)

[0560] ·3-Methoxy-4-diazodiphenylamine hexafluorophosphate: 0.1 parts

[0561] • A compound in which the counterion of ethyl violet is changed to 6-hydroxynaphthalenesulfonic acid: 0.15 parts

[0562] Fluorinated surfactant (MEGAFACE F-780F, DIC CORPORATION, structural reference (e-1)): 0.01 parts

[0563] • Silicone-based surface conditioner (BYK-300, BYK JAPAN KK): 0.01 parts or none (listed in Tables 8 to 14)

[0564] • Siloxane-based surface conditioners (additives (e-2) below): 0.01 parts or none (listed in Tables 8 to 14)

[0565] · Methyl ethyl ketone: 30 parts

[0566] ·1-Methoxy-2-propanol: 15 parts

[0567] γ-Butyrolactone: 15 parts

[0568] [Table 8]

[0569]

[0570] [Table 9]

[0571]

[0572] [Table 10]

[0573]

[0574] [Table 11]

[0575]

[0576] [Table 12]

[0577]

[0578] [Table 13]

[0579]

[0580] [Table 14]

[0581]

[0582] According to the results in Tables 8 to 14, the original positive lithographic printing plates of the various embodiments of the present invention have good development differentiation and can obtain high-precision images. The obtained lithographic printing plates have excellent brush resistance and scratch resistance.

[0583] According to the results of Example 29, the use of propyl gallate containing the specific compound (a-2) yielded good results. Furthermore, according to the results of Examples 29 to 33, good results can be obtained regardless of the content of the specific compound.

[0584] According to the comparison between Example 29 and Example 49, and Examples 50 to 54, it can be seen that by using fluorinated surfactants or siloxane-based surface modifiers, and further using siloxane-based surface modifiers (e-2), the development resolution and scratch resistance are particularly improved.

[0585] Comparisons between Comparative Examples 13 to 16 and the various embodiments show that, even compounds containing phenolic hydroxyl groups in one molecule, compared to positive lithographic printing plates having an image recording layer formed from a positive photosensitive resin composition using a compound that does not have electron-withdrawing groups or a compound that has electron-withdrawing groups other than specific electron-withdrawing groups, the development resolution, brush resistance, and scratch resistance of the image area of ​​the various embodiments are better.

Claims

1. A positive offset printing plate original, which has the following characteristics: Support body; and The image recording layer on the support is formed of a positive photosensitive resin composition. The positive photosensitive resin composition contains: A compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule; Alkali-soluble resins; and Infrared absorber, The electron-withdrawing groups do not include sulfonyl groups.

2. The original positive offset printing plate according to claim 1, wherein, The electron-withdrawing group is selected from at least one of the following groups: halogen atom, trifluoromethyl, nitro, cyano, alkoxycarbonyl, acyloxy, amide, and alkylcarbonyl.

3. The original positive offset printing plate according to claim 1 or 2, wherein, The compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is a compound having two or more phenolic hydroxyl groups in one molecule.

4. The original positive offset printing plate according to claim 1 or 2, wherein, The compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is a compound having three or more phenolic hydroxyl groups in one molecule.

5. The original positive offset printing plate according to claim 1 or 2, wherein, The electron-withdrawing group is an alkoxycarbonyl or an alkylcarbonyl group.

6. The original positive offset printing plate according to claim 1 or 2, wherein, The compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule comprises compounds selected from the group consisting of gallic acid ester compounds and compounds having multiple gallic acid ester sites in the same molecule.

7. The original positive offset printing plate according to claim 1 or 2, wherein, The compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule is a gallic acid ester compound.

8. A positive offset printing plate original, which has the following characteristics: Support body; and The image recording layer on the support body The image recording layer has a lower layer and an upper layer sequentially from the support side, and at least one of the lower layer and the upper layer is formed of a positive photosensitive resin composition. The positive photosensitive resin composition contains: A compound having at least one electron-withdrawing group and at least one phenolic hydroxyl group in one molecule; Alkali-soluble resins; and Infrared absorber, The electron-withdrawing groups do not include sulfonyl groups.

9. The original positive offset printing plate according to claim 8, wherein, An undercoat layer is provided between the support and the image recording layer.

10. The original positive offset printing plate according to claim 8, wherein, The lower layer is formed from the positive photosensitive resin composition. The alkali-soluble resin contained in the lower layer comprises at least one selected from the group consisting of acrylic resins having sulfonamide groups on their side chains, acrylic resins having phenolic hydroxyl groups on their side chains, and phenolic varnish resins.

11. The original positive offset printing plate according to claim 8, wherein, The upper layer is formed from the positive photosensitive resin composition. The upper layer comprises an infrared absorber and a water-insoluble but alkali-soluble resin, wherein the water-insoluble but alkali-soluble resin is at least one selected from the group consisting of polyamide resin, epoxy resin, polyacetal resin, acrylic resin, methacrylic resin, polystyrene resin, and phenolic varnish-type phenolic resin. An interaction is formed between the polar groups of the water-insoluble and alkali-soluble resin and the infrared absorber.

12. The original positive offset printing plate according to claim 9, wherein, The base coating comprises at least one selected from the group consisting of phosphonic acids having an amino group, organophosphonic acids, organophosphates, organophosphonic acids, amino acids, and hydrochlorides of amines having a hydroxyl group.

13. The original positive offset printing plate according to claim 8, wherein, The upper layer further comprises a polymer having structural units with fluoroalkyl groups on their side chains.

14. The original positive offset printing plate according to claim 8, wherein, At least one of the upper and lower layers comprises a polymer having structural units represented by the following formula (I), In equation (I), R 11 and R 北 Each can be independently represented by a hydrogen atom or an alkyl group, R 北 L represents a hydrogen atom or a monovalent substituent. 11 and L 12 Each can be used to represent a single bond or a divalent linker, and Rh represents a substituent containing two or more silicon atoms.

15. The original positive offset printing plate according to claim 14, wherein, The upper layer comprises a polymer having the structural unit represented by formula (I).

16. A method for manufacturing a lithographic printing plate, comprising the following steps: The exposure process involves exposing the original positive offset printing plate as described in any one of claims 1 to 15 to an image. and In the developing process, an alkaline aqueous solution with pH 8.5 to pH 13.5 is used to develop the exposed positive lithographic printing plate.

Images