JPH0934110A - Photopolymerizable composition, method for generating radical, photosensitive material for producing planographic printing plate, and production of planographic printing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photopolymerizable compsn. having satisfactory preservability, capable of writing with IR and capable of forming an image having satisfactory resolution and sensitivity, to provide a method for generating radicals with IR highly sensitively, to obtain a photosensitive material having high photosensitivity in a near IR region as the oscillation wavelength region of semiconductor laser and excellent in shelf stability and to produce a planographic printing plate using the photosensitive material. SOLUTION: This photopolymerizable compsn. contains a polymerizable compd., at least one of onium salts represented by general formulae I-IV, a photothermic conversion element and a radical generating agent on a substrate. In the formulae I-IV, each of R1 -R4 and R10 -R13 is alkyl, aryl or aralkyl, R1 -R4 may bond to one another to form a ring, R10 -R13 may bond to one another to form a ring, each of R5 -R7 is alkyl or aryl, R5 -R7 may bond to one another to form a ring, each of R8 and R9 is aryl and X<-> is a counter anion.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photopolymerizable composition and a radical generating method using a novel radical generator,
More specifically, a photopolymerizable composition utilizing an onium salt (phosphonium salt, sulfonium salt, iodonium salt, ammonium salt), a photothermal conversion element and a radical generator, a radical generating method, a photosensitive material for preparing a lithographic printing plate, and the same. The present invention relates to a method for producing a lithographic printing plate used.

[0002]

2. Description of the Related Art An image forming medium using a photopolymerizable composition comprising a polymerizable compound, a photopolymerization initiator, a colorant and, if necessary, an organic polymer binder is used for producing a colored image such as a color proof. For example, JP-A-61-18853
No. 7, 61-286858. These are generally those in which the photosensitive layer is imagewise exposed and then the unexposed area is eluted with a liquid to form an image consisting of the exposed area. Has spectral sensitivity.

Further, JP-A-3-111402 and 4-1.
46905 and 4-362935 disclose photopolymerization initiators comprising a combination of a near infrared dye and a boron salt.
With these combinations, although the sensitivity is high, there is a large change in sensitivity over time, and there is a problem with storage stability.

Further, Japanese Patent Publication No. 43-19161 discloses a method in which bisimidazole is irradiated with ultraviolet rays to generate radicals to develop a leuco dye, and then an image is fixed with visible light. As shown in this method, bisimidazole is generally known to be cleaved by ultraviolet rays to generate a radical, but a radical is not generated simply by combining with an infrared dye.

As another form, there has been reported a method of obtaining an image by using radicals generated by photolysis or thermal decomposition of an onium salt. For example, Bull. Chem. Soc. J
apan (Burtin of the Chemical Society of Japan) 43,567 (1970)
Although a method of obtaining an image by polymerizing a monomer using a radical generated by thermal decomposition of an onium salt is disclosed, there is no description of using it in combination with a photothermal conversion material (photothermal conversion element in the present invention).

A large number of photosensitive lithographic printing plate materials using a photopolymerization system and methods of preparing lithographic printing plates using the same are known.

Conventionally, as the photopolymerization initiator of the photopolymerizable composition used in these lithographic printing plate forming methods, aromatic ketones such as benzophenone, thioxanthone, quinone and thioacridone, benzoin, benzyl, benzyl ketal, etc. Is used. These photopolymerization initiators,
Since the photosensitive wavelength is in the ultraviolet region, the mask material is brought into close contact with it, exposed to an ultraviolet light source such as a mercury lamp, and then the unexposed portion is eluted and developed.

With the recent advances in image processing, light sources, and image forming techniques, there has been a demand for a photosensitive material that is more sensitive to long-wave light than before. For example, a so-called direct for forming a printing plate by modulating a light source and directly scanning and exposing a light-sensitive material with an image signal transmitted through a communication line and an output signal from an electronic plate making system or an image processing system. It is a plate making system. A laser is suitable as a light source at this time. In particular, there has been a demand for the development of a photosensitive lithographic printing plate material that is small in size and low in cost and can directly form a printing plate with high resolution by using scanning exposure of a semiconductor laser.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art. That is, a first object of the present invention is to provide a photopolymerizable composition capable of writing with infrared light and forming an image with good resolution and sensitivity. The second purpose is to provide a photopolymerizable composition having good storage stability. A third object is to provide a radical generating method for generating radicals with high sensitivity by infrared light. A fourth object is a photosensitive material for preparing a lithographic printing plate having high photosensitivity in the near infrared region which is an oscillation wavelength region of a semiconductor laser and excellent in storage stability, and a method for preparing a lithographic printing plate using the same. To provide.

[0010]

Means for Solving the Problems As a result of earnest studies, the present inventors have found that the combination of a photothermal conversion element, an onium salt and a radical generator enables radical generation with high sensitivity, and an unexpected result. The invention was completed.

That is, the above object of the present invention is achieved by the following constitution.

(1) On a support, a polymerizable compound, at least one of onium salts represented by the following general formulas (I), (II), (III) or (IV), a photothermal conversion element and radical generation A photopolymerizable composition containing an agent.

[0013]

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In the formula, R _{1 to} R ₄ and R _{10 to} R ₁₃ each represent an alkyl group, an aryl group or an aralkyl group, and R ₁ to R ₄
R ₄ and R _{10 to} R ₁₃ may combine with each other to form a ring. R ₅ , R ₆ and R ₇ each represent an alkyl group or an aryl group, and R _{5 to} R ₇ may combine with each other to form a ring. R ₈ and R ₉ each represent an aryl group, and X ⁻
Represents a counter anion.

(2) The photopolymerizable composition according to (1), wherein the radical generator is a bisimidazole derivative.

(3) The photopolymerizable composition according to (1), wherein the counter anion represented by X ⁻ of the onium salt is a halogen ion.

(4) The image-forming material as described in (3), wherein the halogen ion is chlorine ion or bromine ion.

(5) A radical generating method in which the photopolymerizable composition according to (2) is exposed to infrared light.

(6) A photosensitive material for preparing a lithographic printing plate comprising at least a photosensitive layer and a protective layer provided in this order on a hydrophilic support, wherein the photosensitive layer has at least one ethylenically unsaturated bond, A photosensitive material for preparing a lithographic printing plate comprising a binder component, at least one of the onium salts represented by the general formula (I), (II), (III) or (IV), a photothermal conversion element and a radical generator.

(7) In the method for preparing a lithographic printing plate using the photographic material for preparing a lithographic printing plate according to (6), the photosensitive layer of the photosensitive material is imagewise scanned and exposed with a semiconductor laser and then protected. A method for preparing a lithographic printing plate, which comprises eluting and removing the unexposed areas of the layer and the photosensitive layer.

The present invention will be described in more detail below.

First, the phosphonium salt compound represented by the general formula (I) (hereinafter referred to as the phosphonium salt of the present invention) will be described in detail.

Specific examples of the substituents represented by R _{1 to} R ₄ are as follows.

The alkyl group includes linear and branched alkyl groups, and examples thereof include methyl, ethyl, butyl, i-butyl, hexyl, octyl and stearyl groups. An alkyl group having 1 to 10 carbon atoms is preferable from the viewpoint of color density, and a butyl group is particularly preferable. These alkyl groups may combine with each other to form a ring, and the cycloalkyl group has a 5- to 7-membered ring (for example, cyclopentyl,
A cyclohexyl group) is preferred.

Examples of the aryl group include phenyl and naphthyl groups, and examples of the aralkyl group include benzyl and phenethyl groups.

These groups may be further substituted,
As a substituent, a halogen atom, a cyano group, a nitro group, an alkyl group, an aryl group, a hydroxyl group, an amino group (including an alkyl-substituted amino group), an alkoxy group, a carbamoyl group, a -COOR group, a -OCOR group (R is an alkyl group. ,
Organic groups such as aryl groups).

[0027] X ^- include counter anion represented by, but not particularly limited as long as it is a monovalent anion, preferably a halogen ion, further chlorine and bromine anion is preferable in terms of color density. Specific examples of the counter anion include bromide, chloride, iodide, fluoride,
Examples thereof include perchlorate, benzoate, thiocyanate, acetate, trifluoroacetate, hexafluorophosphate, nitrate and salicinate.

Next, the sulfonium salt compound represented by the general formula (II) (hereinafter referred to as the sulfonium salt of the present invention) will be described in detail.

Specific examples of the substituents represented by R _{5 to} R ₇ are as follows.

The alkyl group includes straight chain and branched alkyl groups, and examples thereof include methyl, ethyl, butyl, i-butyl, hexyl, octyl and stearyl groups. An alkyl group having 1 to 10 carbon atoms is preferable from the viewpoint of color density, and a butyl group is particularly preferable. These alkyl groups may combine with each other to form a ring, and the cycloalkyl group is preferably a 5- to 7-membered ring (eg, cyclopentyl, cyclohexyl group, etc.).

Examples of the aryl group include phenyl and naphthyl.

Examples of the ring formed by R _{5 to} R ₇ together with S ⁺ include a benzothiathiopyrylium ring.

These groups may be further substituted,
Examples of the substituent include the same groups as those described in the general formula (I).

[0034] X ^- counter anion represented by the general formula (I) X ^- as synonymous.

Further, the iodonium salt compound represented by the general formula (III) (hereinafter referred to as the iodonium salt of the present invention)
Will be described in detail.

Examples of the aryl group represented by R ₈ and R ₉ include a phenyl group and a naphthyl group. These groups may be further substituted, and the substituent is represented by the above formula (I). The same groups as those mentioned above can be mentioned.

[0037] X ^- counter anion represented by the general formula (I) X ^- as synonymous.

Next, the ammonium salt compound represented by the general formula (IV) (hereinafter referred to as the ammonium salt of the present invention) will be described in detail.

Specific examples of the substituents represented by R _{10 to} R ₁₃ are as follows.

Alkyl groups include straight chain and branched alkyl groups such as methyl, ethyl, butyl, i-butyl,
Hexyl, octyl, stearyl and the like can be mentioned. From the viewpoint of color density, an alkyl group having 1 to 10 carbon atoms is preferable,
A butyl group is particularly preferable. These alkyl groups may combine with each other to form a ring, and the cycloalkyl group is preferably a 5- to 7-membered ring (eg, cyclopentyl, cyclohexyl group, etc.).

Examples of the aryl group include phenyl and naphthyl groups, and examples of the aralkyl group include benzyl and phenethyl groups.

These groups may be further substituted,
As the substituent, a halogen atom, a cyano group, a nitro group, an alkyl group, an aryl group, a hydroxyl group, an amino group (including an alkyl-substituted amino group), an alkoxy group, a carbamoyl group, a -COOR group, a -OCOR (R is an alkyl group. ,
Organic groups such as aryl groups).

Typical representative examples of the onium salt of the present invention are shown below, but the invention is not limited thereto.

[0044]

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[0045]

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[0046]

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[0047]

[Chemical 6]

[0048]

[Chemical 7]

[0049]

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The addition amount of the onium salt of the present invention varies depending on the type and usage of the onium salt.
0.2-5g is preferable per m < ² >.

Next, the photothermal conversion element will be described in detail.

The photothermal conversion element used in the present invention may be any substance that absorbs light and efficiently converts it into heat. When a semiconductor laser is used as a light source, one having absorption in the near infrared is preferable. For example, carbon black, magnetic powder, and black dye, as infrared dye, various cyanine dyes, anthraquinone-based, indoaniline metal complex-based, azurenium-based, croconium-based, squarylium-based, dithiol metal complex-based, chelate-based, naphthalocyanine A metal complex type, an intermolecular CT type dye or the like can be used.
These dyes can of course be synthesized by a known method, but the following commercial products can also be used.

Nippon Kayaku: IR750 (anthraquinone type); IR002, IR003 (aluminum type); I
R820 (polymethine type); IRG022, IRG03
3 (diimmonium type); CY-2, CY-4, CY-
9, CY-20, Mitsui Toatsu; KIR103, SIR10
3 (phthalocyanine); KIR101, SIR114
(Anthraquinone type); PA1001, PA1005
PA1006, SIR128 (metal complex type), Dainippon Ink and Chemicals; Fastogen blue 8120, Midori Kagaku; MIR-101, 1011, 1021.

Typical examples of the photothermal conversion element preferably used are shown below.

[0055]

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[0056]

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[0057]

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[0058]

[Chemical 12]

[0059]

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The addition amount of the photothermal conversion element is usually 2 to 80% by weight, preferably 20 to 70% by weight based on the solid content composition, and it is preferable to add it to the same layer as the radical initiator, but a plurality of layers may be added. When it is composed of, it may be added to another layer.

Next, the radical generator will be described.

According to the mode of the present invention, it is considered that heat is generated from the photothermal conversion element by infrared light, and the heat causes a radical by the interaction between the onium salt and the radical generator, which is a feature of the present invention.

Specific examples of the radical generator include halides (α-haloacetophenones, trichloromethyltriazines, etc.), azo compounds, aromatic carbonyl compounds (benzoin esters, ketals, acetophenones, o-acyloxyimino). Examples thereof include ketones, acylphosphine oxides, etc.), hexaarylbisimidazole compounds, peroxides, etc., among which bisimidazole derivatives are preferable. A specific example is shown below,
It is not limited to these.

[0064]

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The addition amount of the radical generator of the present invention varies depending on the type and usage of the radical generator, but is preferably 0.1 to 10 g per 1 m ^{2 of} the image forming material.

The photosensitive layer is prepared by dissolving an onium salt, a radical generator and a photothermal conversion element in a solvent together with a binder, or dispersing a fine particle in the solvent to prepare a photosensitive layer coating solution.
It is formed by coating on a support and appropriately drying. The thickness of the photosensitive layer is preferably 5 to 100 μm as a dry film thickness.

As the support, paper, synthetic paper (for example, synthetic paper containing polypropylene as a main component), resin film or sheet, plastic film or sheet formed by laminating two or more layers of resin, or various kinds Examples thereof include a film or sheet in which a resin layer is laminated on a paper made of a polymer material, metal, ceramic or wood pulp, cellulose pulp, sulfite pulp, or the like. Examples of the resin constituting the film or sheet of such a resin include acrylic resins such as acrylic acid ester and methacrylic acid ester, polyethylene terephthalate,
Polyester resins such as polybutylene terephthalate, polyethylene naphthalate, polycarbonate and polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyolefin resins such as polyethylene, polypropylene and polystyrene, polyamides such as nylon and aromatic polyamide Resins, polyether ether ketone, polysulfone, polyether sulfone, polyimide, polyetherimide, polyparabanic acid, phenoxy resin, epoxy resin, urethane resin, melamine resin, alkyd resin, phenol resin, fluorine resin, silicone resin, etc. .

The support provided with the photosensitive layer when used for preparing a lithographic printing plate includes aluminum, zinc, copper,
Metal plates such as steel, as well as metal plates or paper plated or deposited with chromium, zinc, copper, nickel, aluminum, iron, etc.
Examples thereof include a plastic film and a glass plate, a resin-coated paper, a paper covered with a metal foil such as aluminum, a plastic film subjected to a hydrophilic treatment, and the like. Of these, an aluminum plate is preferable.

The support of the present invention includes a graining treatment,
It is more preferable to use an aluminum plate that has been subjected to anodizing treatment and, if necessary, surface treatment such as sealing treatment.

Known methods can be used for these treatments. Examples of the graining method include a mechanical method and an electrolytic etching method. Examples of the mechanical method include a ball polishing method, a brush polishing method, a polishing method using liquid honing, and a buff polishing method.

The above-mentioned various methods can be used alone or in combination depending on the composition of the aluminum material. Preferred is a method by electrolytic etching.

The electrolytic etching is carried out in a bath of an acid such as phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid or a mixture of two or more kinds thereof.
After the graining treatment, if necessary, desmut treatment is performed with an aqueous solution of alkali or acid, neutralization and washing with water.
The anodic oxidation treatment is performed by using a solution containing one or more of sulfuric acid, chromic acid, oxalic acid, phosphoric acid, malonic acid and the like as an electrolytic solution, and electrolytically using an aluminum plate as an anode. The amount of anodized film formed is suitably 1 to 50 mg / dm ² , and preferably 10 to 40 mg / dm ² . The amount of the anodic oxide film is obtained, for example, by immersing an aluminum plate in a chromic acid phosphoric acid solution, dissolving the oxide film, and measuring the weight change of the plate before and after the film is dissolved.

Specific examples of the sealing treatment include boiling water treatment, steam treatment, sodium silicate treatment, and dichromate aqueous solution treatment. In addition to this, the aluminum plate support may be subjected to an undercoating treatment with an aqueous solution of a water-soluble polymer compound or a metal salt such as zircon fluoride.

The thickness of the support is usually 3 to 1000 μm, preferably 8 to 300 μm.

As the binder resin used in the photosensitive layer, various known polymers can be used. Details of specific binders are described in U.S. Pat. No. 4,072,52.
No. 7, and more preferably described in JP-A-54-9.
No. 8613, a monomer having an aromatic hydroxyl group, such as N- (4-hydroxyphenyl) acrylamide, N- (4-hydroxyphenyl) methacrylamide, o-, m- or p-hydroxystyrene. , O
Copolymers of-, m- or p-hydroxyphenyl methacrylate with other monomers, U.S. Pat. No. 4,123,27
Polymers containing hydroxyethyl acrylate units or hydroxyethyl methacrylate as described in US Pat. No. 6, natural resins such as shellac, rosin, polyvinyl alcohol, polyamide resins as described in US Pat. No. 3,751,257, US Patent 3,660,097
Linear polyurethane resin, phthalated resin of polyvinyl alcohol, bisphenol A, etc.
And epoxy resins condensed from epichlorohydrin, cellulose resins such as cellulose acetate, cellulose acetate phthalate, and the like.

As the binder resin, one kind or a combination of two or more kinds of these resins can be used. Among them, vinyl chloride, vinyl chloride-vinyl acetate copolymer resin, acrylic resin, methacrylic resin, polystyrene, polycarbonate, polysulfone, polyethersulfone, polyvinyl butyral, styrene-acrylonitrile, polyvinyl acetal, nitrocellulose,
Solvent-soluble polymers such as ethyl cellulose are preferred.

These binders may be used by dissolving one or more kinds in an organic solvent and using them in the form of latex dispersion. The amount of the binder used varies depending on the purpose of the image forming material of the present invention and depends on whether it has a single-layer structure or a multi-layer structure.
1.0 to ²⁰ g per m ² is preferred.

Next, the polymerizable compound will be described in detail.

As the polymerizable compound, known monomers can be used without particular limitation. Specific monomers include, for example, 2-ethylhexyl acrylate,
Monofunctional acrylic acid esters such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate and their derivatives or compounds in which these acrylates are replaced with methacrylate, itaconate, crotonate, maleate, etc .; polyethylene glycol diacrylate,
Difunctional acrylates such as pentaerythritol diacrylate, bisphenol A diacrylate, diacrylate of neopentyl glycol hydroxypivalate ε-caprolactone adduct, and their derivatives or these acrylates are replaced with methacrylate, itaconate, crotonate, maleate, etc. Compounds; or polyfunctional acrylic acid esters such as trimethylolpropane tri (meth) acrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, pyrogallol triacrylate and their derivatives, or acrylates of these, methacrylates, itaconates, crotonates, and maleates. And the like. Also, by introducing acrylic acid or methacrylic acid into an oligomer having an appropriate molecular weight,
A so-called prepolymer having photopolymerizability can be preferably used.

In addition to this, JP-A-58-212994,
Nos. 61-6649, 62-46688 and 62-
No. 48589, No. 62-173295, No. 62-18
Nos. 7092 and 63-67189, JP-A-1-244
Compounds described in No. 891 and the like can be mentioned, and further, “11290 chemical products”, Chemical Industry Daily, 286-
The compounds described on page 294, the compounds described on pages 11 to 65 of "UV / EB curing handbook (raw material edition)", Kobunshi Kogyo Kai, etc. can also be preferably used.

Of these, compounds having two or more acryl groups or methacryl groups in the molecule are preferable in the present invention, and those having a molecular weight of 10,000 or less, more preferably 5,000 or less are desirable. In the present invention, among these monomers or prepolymers, one kind or a mixture of two or more kinds can be used.

The compound having an ethylenically unsaturated group is contained in the photosensitive layer in an amount of preferably 20 to 80% by weight, more preferably 30 to 60% by weight.

The photosensitive material for preparing a lithographic printing plate (hereinafter also simply referred to as a photosensitive material) may have an auxiliary layer such as an intermediate layer, a protective layer and an undercoat layer in addition to the photosensitive layer containing the photothermal conversion material. Good.

Next, an image forming method using the light-sensitive material of the present invention will be described. When the photosensitive material is imagewise exposed, heat is generated by the photothermal conversion material according to the exposure amount, and the heat causes the radical generator and the onium salt to interact with each other to generate radicals. When it is used as a material for forming an image by radical polymerization, the generated radicals cause polymerization to form an image. For exposure of photosensitive material, sunlight, tungsten light, mercury lamp, halogen lamp,
Xenon lamp, laser light, light emitting diode, CRT
Etc. can be used. As a material for forming an image by the above radical polymerization, the photosensitive layer contains a polymerizable compound having at least an ethylenically unsaturated bond and, if necessary, a colorant. As such a polymerizable compound having an ethylenically unsaturated bond, a known crosslinkable monomer can be used without particular limitation. Specific monomers include, for example, monofunctional acrylic acid esters such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate, and their derivatives, or these acrylates replaced with methacrylate, itaconate, crotonate, maleate and the like. Compounds, polyethylene glycol diacrylate, pentaerythritol diacrylate, bisphenol A diacrylate, diacrylate of ε-caprolactone adduct of neopentyl glycol hydroxypivalate, etc., and bifunctional acrylic acid esters and their derivatives, or their acrylates, methacrylates and itaconates. , Crotonate, compounds substituted for maleate, etc., or trimethylolpropane tri (meth) acrylate, Pentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, polyfunctional acrylic acid esters and derivatives thereof or methacrylate these acrylates such as pyrogallol triacrylate, itaconate, crotonate,
Examples thereof include compounds substituted for maleate and the like.
As the resin having an ethylenically unsaturated bond, a so-called prepolymer obtained by introducing photopolymerizability by introducing acrylic acid or methacrylic acid into an oligomer having an appropriate molecular weight can be preferably used. In addition to this, JP-A-58-21
No. 2994, No. 61-6649, No. 62-46688
No. 62-48589, No. 62-173295,
Examples thereof include compounds described in JP-A Nos. 62-187092, 63-67189, JP-A-1-244891, and the like, and “Chemical products of 11290” (supra), 2
The compounds described on pages 86 to 294, the "UV / EB curing handbook (raw material edition)" (supra), and the compounds described on pages 11 to 65 can be preferably used in the present invention. Among these, compounds having two or more acryl or methacryl groups in the molecule are preferable in the present invention, and those having a molecular weight of 10,000 or less, more preferably 5,000 or less are preferable. In the present invention, one or two of these monomers or prepolymers are used.
A mixture of more than one species can be used.

The polymerizable compound having an ethylenically unsaturated bond is usually contained in the photosensitive layer forming composition in an amount of 5% by weight or more,
More preferably, it is set to 15% by weight or more.

A binder resin is used in the photosensitive layer if necessary. As the binder resin, polyester resin, polyvinyl acetal resin, polyurethane resin, polyamide resin, cellulose resin, olefin resin, vinyl chloride resin, (meth) acrylic resin,
Examples thereof include styrene resin, polycarbonate, polyvinyl alcohol, polyvinylpyrrolidone, polysulfone, polycaprolactone resin, polyacrylonitrile resin, urea resin, epoxy resin, phenoxy resin and rubber resin. Further, a resin having an unsaturated bond in the resin, for example, a diallyl phthalate resin and its derivative, chlorinated polypropylene, etc., can be polymerized with the above-mentioned compound having an ethylenically unsaturated bond, so that it is suitably used depending on the application. Can be used. As the binder resin, one or more of the above resins can be used in combination.

These binder resins are preferably used in an amount of 500 parts by weight or less, more preferably 200 parts by weight or less, relative to 100 parts by weight of the polymerizable compound having an ethylenically unsaturated bond.

As one form of the present invention, it may be colored with a coloring agent. The colorant is configured so that the absorbance at any point (absorption in the present invention means transmission density) is 3.0 or more in at least the wavelength range of 350 to 700 nm. This colorant is contained in the photosensitive layer.

As the coloring agent, carbon black, titanium oxide, iron oxide, phthalocyanine pigment, azo pigment,
Anthraquinone pigments, quinacridone pigments, and known pigments and / or dyes such as crystal violet, methylene blue, azo dyes, anthraquinone dyes, cyanine dyes, etc., are used alone or in combination of two or more so as to satisfy the above absorbance. It is contained in the photosensitive layer.

The addition amount of the colorant is preferably 10 to 80% by weight, more preferably 15 to 70% by weight in the composition for forming the photosensitive layer or the color material layer.

In order to add the colorant into the photosensitive layer or the color material layer, the colorant is added to the photosensitive layer composition other than the colorant, such as a sand mill, a ball mill, an attritor, an ultrasonic disperser, a jet mill or a homogenizer. It is possible to disperse and mix using a publicly-used device such as a planetary mill, and further filter the coating solution as needed before use.

The photosensitive layer according to the present invention may optionally contain other components such as a sensitizer, a thermal polymerization inhibitor, a heat-fusible compound, an oxygen scavenger and a plasticizer as long as the purpose is not impaired. is there.

As a sensitizer, Japanese Patent Laid-Open No. 64-13140 is used.
Compounds described in JP-A-64-1314
1, an aromatic onium salt, an aromatic halonium salt,
Examples thereof include organic peroxides described in JP-A 64-13143, bisimidazole compounds and thiols described in JP-B-45-37377 and US Pat. No. 3,652,275. The sensitizer is added in an amount of 10 parts by weight or less, preferably about 0.01 to 5 parts by weight, based on 100 parts by weight of the total amount of the polymerizable compound having an ethylenically unsaturated bond and the binder.

As the thermal polymerization inhibitor, compounds such as quinone type and phenol type are preferably used. For example, hydroquinone, pyrogallol, p-methoxyphenol, catechol, β-naphthol, 2,6-di-t-butyl-
p-cresol and the like. Total amount of polymerizable compound having ethylenically unsaturated bond and binder 100
10 parts by weight or less based on parts by weight, preferably 0.01 to
About 5 parts by weight are added.

As the oxygen quencher, N, N-dialkylaniline derivatives are preferable, for example, US Pat.
72, 541 11th column 58th line-12th column 35
The compounds mentioned in the row are mentioned.

Examples of the plasticizer include phthalic acid esters, trimellitic acid esters, adipic acid esters, other saturated or unsaturated carboxylic acid esters, oxalic acid esters, epoxidized soybean oil, epoxidized linseed oil and stearin. Examples thereof include acid epoxies, orthophosphoric acid esters, phosphite esters, and glycol esters.

As the heat-fusible compound, a compound which is solid at room temperature and reversibly becomes liquid when heated is used.
Examples of the heat-fusible substance include alcohols such as terpineol, menthol, 1,4-cyclohexanediol and phenol; amides such as acetamide and benzamide; esters such as coumarin and benzyl cinnamate; ethers such as diphenyl ether and crown ether. Ketones such as camphor and p-methylacetophenone; Aldehydes such as vanillin and dimethoxybenzaldehyde;
Typical examples are hydrocarbons such as norbornene and stilbene; higher fatty acids such as margaric acid; higher alcohols such as eicosanol; higher fatty acid esters such as cetyl palmitate; higher fatty acid amides such as stearic acid amide; higher amines such as behenylamine. Monomolecular compound, beeswax,
Waxes such as candelilla wax, paraffin wax, ester wax, montan wax, carnauba wax, amide wax, polyethylene wax, microcrystalline wax, ester gum, rosin maleic acid resin, rosin phenol resin and other rosin derivatives, phenolic resin, ketone Resins, epoxy resins, diallyl phthalate resins, terpene hydrocarbon resins, cyclopentadiene resins, polyolefin resins, polycaprolactone resins, polyethylene glycol, polypropylene glycol and other polymer compounds represented by polyolefin oxide it can.

Further, if necessary, an antioxidant, a filler, an antistatic agent, etc. may be added to the photosensitive layer.

As the antioxidant, a chroman compound,
Claman-based compounds, phenol-based compounds, hydroquinone derivatives, hindered amine derivatives, spiroindane-based compounds, sulfur-based compounds, phosphorus-based compounds and the like are mentioned, and JP-A-59-182785 and 60-130735,
61-159644, JP-A-1-127387,
The compounds described in “Chemical products of 11290” (supra), pages 862 to 868, etc., and compounds known to improve durability in photographs and other image recording materials can be mentioned.

Examples of the filler include inorganic fine particles and organic resin particles. Examples of the inorganic fine particles include silica gel, calcium carbonate, titanium oxide, zinc oxide, barium sulfate, talc, clay, kaolin, acid clay, activated clay, alumina and the like, and organic fine particles include fluorine resin particles and guanamine resin. Particles, resin particles such as acrylic resin particles and silicone resin particles, and antistatic agents include cationic surfactants, anionic surfactants, nonionic surfactants, polymeric antistatic agents, conductive fine particles, etc. Others, "11290 chemical products" (above),
The compounds described on pages 875 to 876 can also be preferably used.

In the present invention, the photosensitive layer may be formed of a single layer or a plurality of layers of two or more layers.
When it is composed of a plurality of layers, it may be composed of photosensitive layers having different compositions, and in this case, a photosensitive layer containing no colorant may be contained.

The thickness of the photosensitive layer is preferably 0.2 to 10 μm, more preferably 0.5 to 5 μm.

The photosensitive layer is formed by dispersing or dissolving the forming components in a solvent to prepare a coating solution and directly laminating and coating on the intermediate layer and drying, or by coating and drying on a cover sheet described later. To be done.

Solvents used in the coating method include water, alcohols (ethanol, propanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), aromatics (toluene, xylene, chlorobenzene, etc.), ketones (acetone). , Methyl ethyl ketone, etc.), ester solvents (ethyl acetate, butyl acetate, etc.), ethers (tetrahydrofuran, dioxane, etc.), chlorine solvents (chloroform, trichloroethylene, etc.), amide solvents (dimethylformamide, N-methylpyrrolidone, etc.) , Dimethyl sulfoxide and the like.

For coating, a conventionally known surface sequential coating method using a gravure roll, an extrusion coating method, a wire bar coating method, a roll coating method and the like can be adopted.

[0106]

EXAMPLES The present invention will be specifically described below with reference to examples.

(Preparation of Supports A and B) Thickness 0.24 m
6 m aluminum plate (material 1050, temper H16)
Immerse in a 5% sodium hydroxide aqueous solution kept at 5 ° C,
After performing degreasing treatment for 1 minute, it was washed with water. The degreased aluminum plate was immersed in a 10% hydrochloric acid aqueous solution kept at 25 ° C. for 1 minute for neutralization, and then washed with water.

Then, this aluminum plate was electrolytically surface-roughened for 60 seconds with an alternating current in a 1.0 wt% hydrochloric acid aqueous solution at 25 ° C. and 100 A / dm ² and then at 60 ° C.
Desmutting treatment was carried out for 10 seconds in a 5% aqueous sodium hydroxide solution maintained at. This roughened aluminum plate is placed in a 40% phosphoric acid solution under the conditions of 30 ° C. and 4 A / dm ² for 6 hours.
Anodizing treatment was performed for a minute, and then a sealing treatment was further performed with sodium silicate to prepare a support.

(Preparation of Photosensitive Material for Lithographic Printing Plate) A photopolymerizable composition coating solution having the following composition was applied onto the above support using a wire bar so that a dry film thickness was 2.0 μm. Was formed.

Photopolymerizable composition Binder resin (hydroxyethyl methacrylate / methyl methacrylate / butyl acrylate / acrylic acid = 30/50/5/15) 50 parts by weight Monomer (dipentaerythritol hexaacrylate) 50 parts by weight Radical generator (A-1) 5 parts by weight Photothermal conversion material (IR-5) 10 parts by weight Onium salt (Q-1) 5 parts by weight Methyl ethyl ketone 400 parts by weight Polyvinyl alcohol (Nippon Gosei Kagaku GL- A 10% aqueous solution of (05) was applied and dried with a wire bar to a dry film thickness of 2.0 μm to form a protective layer. The obtained photosensitive material is protected from light at 80 ° C.
-Photosensitive material 1 for evaluation was obtained by heat treatment for 2 minutes.

(Image formation and evaluation) The formed light-sensitive material was image-exposed under the following conditions.

Light source: LT090MD (manufactured by Sharp, output 100 mW, main wavelength 830 nm) Optical efficiency: 67% Exposure beam diameter: 1 / e ² = 10 μm (power density: 85
307 W / cm ² ) Exposure pitch: 6 μm The exposed light-sensitive material was placed in a developing solution having the following composition at 25 ° C.
After immersion for 45 seconds, the protective layer and the unexposed portion of the photosensitive layer were eluted, washed with water, and dried to obtain an image.

Developer composition Benzyl alcohol 360 parts by weight Diethanolamine 210 parts by weight Perex NBL 180 parts by weight (Kao: sodium t-butylnaphthalene sulfonate) Potassium sulfite 90 parts by weight Water 3000 parts by weight Sensitivity and storability are as follows. evaluated.

<Sensitivity> The minimum exposure energy required for image formation (exposure amount capable of reproducing a line width of 10 μm) was measured. The smaller the value, the higher the sensitivity.

<Preservability> The sensitivity after storage at 55 ° C. and 20% RH for 7 days was measured. The smaller the difference from the sensitivity before storage, the better the storage stability.

Next, photosensitive materials 2 to 20 were prepared in the same manner as photosensitive material 1 except that the composition of the photosensitive layer was changed as shown in Table 1, and images were similarly prepared and evaluated.

[0117]

[Table 1]

[0118]

Embedded image

From the results shown in the table, it is understood that the combination of the radical generator and the onium salt provides good sensitivity and little fluctuation after storage for the first time.

[0120]

INDUSTRIAL APPLICABILITY According to the present invention, a lithographic printing plate can be provided using a photographic material for preparing a lithographic printing plate which has high sensitivity in the near infrared region and is excellent in storage stability.

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Claims (7)

[Claims] 1. A polymerizable compound, at least one of onium salts represented by the following general formula (I), (II), (III) or (IV), a photothermal conversion element and a radical generator on a support. A photopolymerizable composition containing: Embedded image [In the formula, R _{1 to} R ₄ and R _{10 to} R ₁₃ are each an alkyl group,
Represents an aryl group or an aralkyl group, R _{1 to} R ₄ and R
_{10 to} R ₁₃ may be bonded to each other to form a ring.
R ₅ , R ₆ and R ₇ each represent an alkyl group or an aryl group, and R _{5 to} R ₇ may combine with each other to form a ring.
R ₈ and R ₉ each represent an aryl group, and X ⁻ represents a counter anion. ] 2. The photopolymerizable composition according to claim 1, wherein the radical generator is a bisimidazole derivative. 3. The counter anion represented by X ⁻ of the onium salt is a halogen ion.
The photopolymerizable composition as described in the above. 4. The image forming material according to claim 3, wherein the halogen ion is chlorine ion or bromine ion. 5. A method of generating radicals, which comprises exposing the photopolymerizable composition according to claim 2 to infrared light. 6. A photosensitive material for preparing a lithographic printing plate comprising at least a photosensitive layer and a protective layer provided in this order on a hydrophilic support, wherein the photosensitive layer has at least one ethylenically unsaturated bond, and a binder. A lithographic printing plate comprising: a component, at least one of the onium salts represented by the general formula (I), (II), (III) or (IV), a photothermal conversion element and a radical generator. Photosensitive material. 7. A method of preparing a lithographic printing plate using the lithographic printing plate-forming photosensitive material according to claim 6, wherein the photosensitive layer of the photosensitive material is subjected to imagewise scanning exposure with a semiconductor laser, and then the protective layer. And a method for producing a lithographic printing plate, which comprises eluting and removing an unexposed portion of the photosensitive layer.