JP2002049147A - Planographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planographic printing original plate with a water- insoluble photosensitive layer containing a photosensitive composition containing a hydrophilic polymer, a specified cyanine compound as a light absorbent and a crosslinker formed on a substrate directly or by way of another layer. SOLUTION: Since the specified cyanine compound excellent in thermal decomposability is used as a light absorbent, when the printing plate is irradiated with light, the hydrophilic functional groups of the hydrophilic polymer in the photosensitive layer are partially decomposed to impart an affinity for ink to the layer. The printing plate can be handled in a light room, does not require operations such as development and wiping and is excellent in sensitivity, resolution and printing resistance. Since the light absorbent has a sulfonic acid group or its salt, it is excellent also in compatibility with the highly hydrophilic polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used in a printing plate and a bright room, can draw directly on the plate with a laser beam, has excellent sensitivity, does not require operations such as development and wiping, and has a resolution and a screen. Plate reproducibility, plate for lithographic printing excellent in various printing characteristics such as printing durability, especially sensitive to light in the near infrared region,
The present invention relates to a planographic printing plate using a dampening solution.

[0002]

2. Description of the Related Art Lithographic printing, so-called offset printing, is the mainstream in printing on paper and is widely used. Conventionally, the printing plate used in this offset printing is to print the document once on paper or the like, then take a photograph of this document to create a composition film, and expose and develop a photosensitive plate through this composition film. It was made by doing.

However, in recent years, digitization of information and increase in the output of a laser have led to a method of making a plate by directly scanning a laser and drawing directly on the plate without using the above-described underlaying film in the production of a plate. So-called CTP (Computer To Plate)
The method is in practical use.

As a CTP plate currently in practical use, there is a photopolymer type printing plate using a photoreaction by visible light of about 500 nm. This plate, of course, requires not only development but also There are problems that the resolution is inferior and that it cannot be handled in a bright room.

In order to improve such a problem, Japanese Patent Laid-Open Publication No. Hei 7-20629 discloses a printing plate using a thermal reaction caused by light in the near-infrared region. Have been. However, this plate can be handled in a bright room, has excellent resolution, and has excellent printing durability due to heat treatment, but still requires development processing.

Further, as a plate which does not require a developing treatment, Japanese Patent Application Laid-Open No. Hei 7-314934 discloses a plate in which a silicon resin ink repellent layer is laminated on an inorganic light absorbing layer such as titanium or titanium oxide. A version has also been developed. The plate is also commercially available, but in this plate, the silicone resin layer repels the ink to form a non-image area, and an image area is formed by irradiation with near-infrared light. The silicone resin layer is not removed, and a printing operation requires a wiping operation to remove the silicone resin in a portion irradiated with light. If the wiping of the silicone resin is insufficient, the ink does not sufficiently adhere to the irradiated portion, causing a defect in the image portion and making it impossible to print well.

[0007] For example, Japanese Patent Application Laid-Open No. Hei 6-199064 discloses a plate in which a light absorbing layer in which carbon black is dispersed in nitrocellulose and a hydrophilic layer or an ink-repellent layer are laminated on the substrate. ing. In this plate, the light absorbing layer and the hydrophilic layer or the ink repellent layer thereon are removed by thermal decomposition of the light absorbing layer, thereby exposing the ink-philic substrate surface.
This is an exposure method based on so-called ablation. This plate can be handled in a bright room and does not require development processing,
The hydrophilic layer or the ink repellent layer does not absorb light and is heated by heat from the light absorbing layer. Therefore, a large amount of energy is required for removing the light absorbing layer and the hydrophilic layer or the ink-repellent layer thereon, so that not only long exposure time or high power is required but also the hydrophilic layer or the ink-repellent layer is The temperature rise of the layer is insufficient for decomposition, and the layer hardly decomposes, and is forcibly blown off by the force generated during thermal decomposition of the light absorbing layer. Therefore, a large amount of fine dust derived from the removed hydrophilic layer or ink-repellent layer and dust derived from the decomposed product of the light absorbing layer scatter and accumulate around the exposed portion of the plate in a large amount. Due to the adhesion of the dust, the property that the ink does not adhere is reduced, causing background stains and printing defects, and the dust is gradually peeled off from the plate during printing and transferred to a printed material.

Further, Japanese Patent Application Laid-Open No. 60-52392 discloses that the surface of a non-water-absorbing resin film is hydrophilized by sulfonation, and the sulfonated surface layer is removed by irradiation with light to make the surface lipophilic. Version is disclosed. In this case, ablation is required, but only the surface layer needs to be ablated.Therefore, the generation of decomposed products is extremely small, and this plate has been improved in this regard. Further, the sulfonation treatment is complicated and dangerous, and there are various production problems.

[0009] As a version not based on ablation, U
S-3793033 discloses a technique in which a photosensitive layer composed of hydroxyethylcellulose, a phenol resin, and a photoradical generator is made lipophilic by curing by light irradiation, but the balance between hydrophilicity and lipophilicity after light irradiation is disclosed. Is not good, and clean printing cannot be performed.

Further, Japanese Patent Application Laid-Open No. 7-1850 discloses a photosensitive layer containing a microcapsule containing a compound which reacts with a hydrophilic group in the hydrophilic resin in a hydrophilic resin. A technology has been disclosed in which a hydrophilic group in a hydrophilic resin is made lipophilic by a reaction by destroying the hydrophilic group. However, in this method, the particle size of the microcapsules must be made very small in order to increase the resolution, and it has been very difficult to produce them.

A method in which another substrate is brought into close contact with a substrate on which a light absorbing layer containing a resin or the like is formed, and light is irradiated, and the light absorbing layer or the like is transferred to the other substrate by heat generated at that time. Although this method has been proposed, it is difficult to uniformly adhere substrates to each other due to adhesion of dust or the like,
There are drawbacks that a large amount of energy is required for transfer, and that the transferred light-absorbing layer has low strength and is peeled off during printing.

[0012]

As described above, the conventional CT
The printing plate for P has the above-mentioned various problems, and the development of a plate for CTP which has improved such problems has been strongly desired. That is, an object of the present invention is to provide a C which can be handled in a bright room, does not require a developing or wiping operation, and is excellent in various printing characteristics such as sensitivity, resolution, background stain, and printing defects.
An object of the present invention is to provide a printing plate for TP and a photosensitive composition used for a photosensitive layer of the printing plate.

[0013]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and completed the present invention. That is, the present invention is specified by the following items. (1) A photosensitive composition containing a hydrophilic polymer, a cyanine compound represented by the following general formula (1), and a cross-linking agent, directly or via another layer on a substrate, and water Printing plate having a photosensitive layer insoluble in the ink.

[0014]

Embedded image

Wherein R ¹ and R ² are an alkyl group, an alkyl group partially substituted with another atom or atomic group, A _m ,
A _n , A _o , and _Ap are sulfonic acid groups or sulfonates;
Y represents a hydrogen atom, an alkyl group, a halogen atom, or a functional group obtained by substituting a halogen atom, Z represents a hydrogen atom or an alkylene group forming a cyclic structure, and partially substituting another atom or atomic group. Is possible. Further, n and m each independently represent 0 to 6. o, p
Each independently represents 0 to 1. The number of sulfonic acids or sulfonates in the molecule is m + n + o + p ≧ 1. X is a monovalent anion, but may not be present when N ⁺ and a sulfonic acid group of the naphtho fused ring form a salt in the molecule. (2) The original printing plate according to (1), wherein the hydrophilic polymer is a polymer obtained by copolymerizing the following (A) and (B).

(A) an unsaturated monomer having an amide group and (b) a hydrophilic substituent selected from a carboxyl group, a sulfonic acid group, a phosphonic acid group and a hydroxyl group, which is copolymerizable with the unsaturated monomer. Monomers selected from species or monomers having two or more side chains.

(3) The printing plate precursor according to (2), wherein the hydrophilic polymer is obtained by polymerizing an unsaturated monomer having an unsubstituted or substituted amide group.

(4) 97-50% by weight of a hydrophilic polymer,
3 to 50% by weight of the crosslinking agent, and 2 to 20 parts by weight of the cyanine compound represented by the general formula (1) based on 100 parts by weight of the hydrophilic polymer and the crosslinking agent. An original plate for printing according to any of the above.

(5) By irradiating the printing original plate according to any one of (1) to (4) with light to partially decompose the photosensitive layer, the hydrophilicity of the photosensitive layer becomes ink-philic. Printing plate changed to.

(6) The printing original plate according to any one of (1) to (4), which has a photosensitive layer on a lipophilic surface.

(7) A printing plate from which the photosensitive layer has been removed by irradiating the printing original plate described in (6) with light.

(8) Irradiation light is 750 to 1100 nm
The printing plate according to (5) or (7), wherein the wavelength is:

(9) A photosensitive composition contained in the photosensitive layer of the printing original plate according to any one of (1) to (4).

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The printing plate precursor of the present invention comprises a hydrophilic polymer, a cyanine compound represented by the above general formula (1), and a crosslinking agent directly or on another substrate. It has a water-insoluble photosensitive layer containing the photosensitive composition.

First, the photosensitive composition for forming the photosensitive layer of the printing original plate according to the present invention will be described. The photosensitive composition contains a hydrophilic polymer, the cyanine compound represented by the general formula (1), and a crosslinking agent. The hydrophilic polymer has a hydrophilic substituent on a side chain, and the heat generated by light irradiation partially decomposes the hydrophilic polymer, thereby losing the hydrophilicity of the photosensitive layer and reducing the ink-philicity. It is desirable that the ones that change or be such that the hydrophilic polymer decomposes almost completely to expose the lipophilic surface of the substrate.

Examples of the hydrophilic polymer include amide groups, carboxyl groups and alkali metal or amine salts thereof, hydroxyl groups, sulfonic acid groups and salts thereof, amino groups and salts thereof, phosphonic acid groups and salts thereof, sulfonamide groups, and polyoxy groups. Polymers having a hydrophilic substituent such as an ethylene group or a polyoxypropylene group on the side chain, and polyoxyethylene polymers, polyoxypropylene polymers, polyoxyethylene / polyoxypropylene polymers, cellulose polymers, gelatin, etc. No. Among these hydrophilic polymers, in the present invention, when the photosensitive composition is used for the photosensitive layer of a printing plate, the photosensitive layer is required to have water resistance, and must be insoluble in water by crosslinking or the like. The hydrophilic polymer is selected from amide group, carboxyl group, sulfonic acid group, phosphonic acid group, and hydroxyl group in view of the easiness of insolubilization in water, the decomposition characteristics of the photosensitive layer upon exposure, and the like. Polymers having one or more substituents on the side chain are preferred.

Specific examples of these preferred polymers will be described below. Examples of the polymer having an amide group in the side chain include homopolymers and copolymers obtained by polymerizing an unsaturated monomer having an unsubstituted or substituted amide group, and those polymers. Of various modified polymers (eg, hydrolyzed polymers,
Polymers to which various compounds are added). Examples of the unsaturated monomer having an unsubstituted or substituted amide group include unsubstituted or substituted (meth) acrylamide, amidated monomers of dibasic acids such as itaconic acid, fumaric acid, and maleic acid, N-vinylacetamide, N- Vinylformamide, N-vinylpyrrolidone, and the like. More specific examples of unsubstituted or substituted (meth) acrylamide include:
(Meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N
-Ethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, diacetone (meth) acrylamide, methylol (meth) acrylamide, Methoxymethyl (meth) acrylamide, butoxymethyl (meth)
Acrylamide, propyl sulfonate (meth) acrylamide, (meth) acryloylmorpholine and the like can be mentioned. In the case of the amidated monomer of a dibasic acid such as the itaconic acid, a monoamide in which one carboxyl group is amidated, a diamide in which both carboxyl groups are amidated, and one carboxyl group is amidated, and May be an amide ester in which the carboxyl group is esterified.

Examples of the polymer having a carboxyl group in the side chain include (meth) acrylic acid, itaconic acid, fumaric acid,
Homopolymers and copolymers obtained by polymerizing dibasic unsaturated acids such as maleic acid and anhydride thereof and carboxyl group-containing unsaturated monomers such as monoesters and monoamides of these dibasic unsaturated acids, and various modifications of these polymers Polymers and the like. In these polymers having a carboxyl group, the carboxyl group may be neutralized with an inorganic base such as sodium hydroxide or potassium hydroxide or an amine.

Examples of the polymer having a sulfonic acid group on the side chain include vinyl sulfonic acid, sulfoethyl (meth) acrylate, (meth) acrylamidomethylpropanesulfonic acid, vinylmethylsulfonic acid, isopropenylmethylsulfonic acid, and (meth) acrylic acid. Ethylene oxide to acid,
Or a sulfuric acid ester of an alcohol to which propylene oxide is added (for example, Eleminol RS manufactured by Sanyo Chemical Industries, Ltd.)
-30), (meth) acryloyloxyethyl sulfonic acid, an ester of a monoalkyl sulfosuccinate with a compound having an allyl group (for example, Eliminol JS2 of Sanyo Chemical Industries, Ltd., Latemul S- of Kao Corporation) 180,
Or S180A), a homopolymer or a copolymer obtained by polymerizing a reaction product of a monoalkyl sulfosuccinate with glycidyl (meth) acrylate, and Antox MS60 of Nippon Emulsifier Co., Ltd., and various modified polymers of these polymers. And the like. In these polymers having a sulfonic acid group, the sulfonic acid group may be neutralized with an inorganic base such as sodium hydroxide or potassium hydroxide or an amine.

Examples of the polymer having a phosphonic acid group in the side chain include vinyl phosphoric acid, mono (2-hydroxyethyl) (meth) acrylate phosphate, and mono (2-hydroxyethyl) (meth) acrylate of monoalkyl phosphate. And various modified polymers of these polymers and the like.
In these polymers having a phosphonic acid group, the phosphonic acid group may be neutralized with an inorganic base such as sodium hydroxide or potassium hydroxide or an amine.

Examples of the polymer having a hydroxyl group in a side chain include:
Examples include a polyvinyl alcohol-based polymer, a homopolymer or a copolymer obtained by polymerizing an unsaturated monomer having a hydroxyl group, and various modified polymers of these polymers. When the polyvinyl alcohol-based polymer is described in more detail, a polymer obtained by completely or partially hydrolyzing a homopolymer or copolymer of a fatty acid vinyl monomer such as vinyl acetate or vinyl propionate, and a partial formalization or acetalization of the polymer, Butyralized polymers and the like. Examples of the unsaturated monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and monomers obtained by adding ethylene oxide and propylene oxide to these (meth) acrylates, methylol Examples thereof include (meth) acrylamide and methoxymethyl (meth) acrylamide and butoxymethyl (meth) acrylamide, which are condensates of the methylol (meth) acrylamide with methyl alcohol or butyl alcohol. In the present invention, the description of “(meth) acryl”, (meth) acrylate ”, (meth) acryloyl” and the like means both acryl and methacryl, acrylate and methacrylate, and acryloyl and methacryloyl.

The printing plate used in the present invention has a water-insoluble photosensitive layer containing a photosensitive composition on a substrate. To make the photosensitive layer insoluble in water, the hydrophilic polymer is usually three-dimensionally crosslinked using a crosslinking agent. When polyvinyl alcohol is used as the hydrophilic polymer, the film can be insoluble in water by crystallizing the film. When using the crosslinking agent, a crosslinkable functional group that reacts with the crosslinking agent must be introduced into the hydrophilic polymer. Specific examples of the crosslinkable functional group vary depending on the type of the crosslinking agent used, and include, for example, a hydroxyl group, a carboxyl group and an alkali metal or amine salt thereof,
Examples include sulfonic acid groups and their alkali metal and amine salts, phosphoric acid groups and their alkali metal and amine salts, amide groups, amino groups, isocyanate groups, glycidyl groups, oxazoline groups, and the like. In order to introduce these crosslinkable functional groups, unsaturated monomers having these functional groups, for example, the above-described unsaturated monomers having a hydroxyl group, unsaturated monomers having a carboxyl group, and unsaturated monomers having a sulfonic acid group May be copolymerized with sulfonic acid propyl (meth) acrylamide and the like, and further, as an unsaturated monomer having a glycidyl group, glycidyl (meth) acrylate and the like may be copolymerized.

Further, in the hydrophilic polymer of the present invention, in addition to the unsaturated monomer having a hydrophilic substituent and the unsaturated monomer having a crosslinkable functional group, in order to further improve the effects of the present invention, Other copolymerizable unsaturated monomers can also be copolymerized. Examples of the copolymerizable unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, Diethylaminoethyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, isopolonyl (meth) acrylate, adamantyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile ,
Vinyl acetate and the like.

The crosslinking agent used to crosslink the hydrophilic polymer of the present invention is one that improves the water resistance of the photosensitive layer by making the hydrophilic polymer insoluble in water by a crosslinking reaction with the hydrophilic polymer. If it is, for example,
Carboxyl groups that are crosslinkable functional groups in the hydrophilic polymer, sulfonic acid groups, hydroxyl groups, glycidyl groups, and in some cases, known polyhydric alcohol compounds that react with amide groups, polycarboxylic acid compounds and anhydrides thereof, Polyvalent glycidyl compounds (epoxy resins), polyamine compounds,
Examples include polyamide resins, polyvalent isocyanate compounds (including block isocyanates), oxazoline resins, amino resins, glyoxal, and the like. In the present invention, among the above-mentioned crosslinking agents, various polyvalent glycidyl compounds (epoxy resins) known from the viewpoints of curing speed, stability of the photosensitive composition, balance between hydrophilicity and water resistance of the photosensitive layer, and the like,
Glyoxal, a curing agent for epoxy resins such as oxazoline resins, amino resins, polyamine compounds and polyamide resins, is preferred. Examples of the amino resin include known melamine resins, urea resins, benzoguanamine resins and glycoluril resins, and modified resins of these resins, such as carboxy-modified melamine resins. Further, in order to accelerate the crosslinking reaction, tertiary amines are used when the above-mentioned glycidyl compound is used, and acidic compounds such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, and ammonium chloride are used in combination when an amino resin is used. You may.

In the photosensitive composition of the present invention, 75% is used as a light absorbing agent in order to enable handling in a bright room.
It contains a cyanine compound represented by the following general formula (1) in that it has an absorption band at 810860 nm, which is the oscillation wavelength of a high-power semiconductor laser available on the market, and particularly excellent in sensitivity and decomposition characteristics. I do.

[0036]

Embedded image

[Wherein R ¹ and R ² are an alkyl group, an alkyl group partially substituted with another atom or atomic group, A _m ,
A _n , A _o , and _Ap are sulfonic acid groups or sulfonates;
Y represents a hydrogen atom, an alkyl group, a halogen atom, or a functional group obtained by substituting a halogen atom, Z represents a hydrogen atom or an alkylene group forming a cyclic structure, and partially substituting another atom or atomic group. Is possible. Further, n and m each independently represent 0 to 6. o, p
Each independently represents 0 to 1. The number of sulfonic acids or sulfonates in the molecule is m + n + o + p ≧ 1. X is a monovalent anion, but may not be present when N ⁺ and a sulfonic acid group of the naphtho fused ring form a salt in the molecule. Specific examples of the alkyl group represented by R ¹ and R ² in the general formula (1) include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-hexyl group. Further, a hydroxyl group, a carboxyl group, or the like may be bonded to this. Am, A ² , A ³ and A ⁴ represent sulfonic acids and sulfonic acid salts. In the case of a sulfonate, a metal such as Na or K or an organic compound such as ammonia, trimethylamine or methylolamine can be used. M, n, o, and p indicating the numbers of Am, A ² , A ³ , and A ⁴ are independent of each other, and m + n + o
It suffices that at least one + p be provided. If necessary, an alkyl group, a carboxylic acid group or the like may be introduced into the naphtho condensed ring.
Specific examples of Y include hydrogen, an alkyl group such as a methyl group and an ethyl group, a halogen atom such as fluorine, chlorine, bromine, and iodine, and substitution thereof to introduce an alkyl group, a hydroxyl group, an amine, an aromatic ring, a heterocyclic ring, and the like. It is possible. Z is a hydrogen atom or an alkylene group, particularly preferably a 5-, 6-, or 7-membered ring. X is Cl in a monovalent anion ^-, Br ^-,
I ^-, ClO4 ^-, PF6 ^- represents the like. However, when the sulfonic acid group, the N + of the naphtho condensed ring and the sulfonic acid group form a salt in the molecule, X may not be present.

The cyanine compound of the present invention represented by the general formula (1) is rapidly decomposed with a large amount of heat generation upon absorption of a laser beam. The heat causes the hydrophilic substituents of the hydrophilic polymer of the photosensitive layer and a part of the main chain to be decomposed, so that the hydrophilicity of the photosensitive layer can be changed to lipophilicity (ink). Since some of them are gasified, the accumulation of decomposition products is small.

When the above-mentioned cyanine compound used in the present invention is insoluble in the hydrophilic polymer used, when it is used in a photosensitive composition, it can be dispersed and used. The particle size of the compound when dispersed, the thickness of the photosensitive layer of the printing plate,
Although it depends on the resolution, usually it is preferably 0.5 μm or less on average. As a method of dispersing, for example, there is a method in which a sand mill, a paint shaker, three rolls, and a slurry are caused to collide at high speed under pressure.

In the present invention, other light absorbing agents may be used in addition to the cyanine compound as the light absorbing agent. Light absorbers that can be used in combination include polymethine compounds, phthalocyanine compounds, naphthalocyanine compounds, anthocyanin compounds, porphyrin compounds, azo compounds, benzoquinone compounds, naphthoquinone compounds, dithiol metal complexes, and diamine metal complexes. Examples include complexes, nigrosine, carbon black, and the like, and cyanine compounds other than those described above.

In the photosensitive composition of the present invention, the proportions of the hydrophilic polymer, the light absorbing agent and the cross-linking agent are determined in consideration of the balance between hydrophilicity and water resistance of the photosensitive layer of the printing plate and various printing characteristics. 97 to 50% by weight of the hydrophilic polymer in solid content, 3 to 50% of the crosslinking agent, and the light absorbing agent are preferably 2 to 20 parts by weight based on the total of 100 parts by weight of the solid content of the hydrophilic polymer and the crosslinking agent. More preferably, the content of the hydrophilic polymer is 95 to 55% by weight, and the amount of the crosslinking agent is 5 to 45% by weight. When the amount of the light absorber is less than 2 parts by weight, the sensitivity is low, which is not preferable.
If it exceeds 0 parts by weight, there is no particular advantage, and it is not preferable because it is disadvantageous in economy.

In the present invention, from the viewpoint of easy change of the exposed portion of the photosensitive layer of the printing plate from hydrophilic to lipophilic (ink), balance between hydrophilicity and water resistance, and various printing characteristics. The hydrophilic polymer contains 30 to 100% by weight of an unsaturated monomer having an amide group, a carboxyl group and a hydroxyl group, 0 to 60% by weight of an unsaturated monomer having a crosslinkable functional group, and other unsaturated monomers. A polymer in which a portion of a saturated monomer is 0 to 50% by weight is more preferable, and a portion of an unsaturated monomer having an amide group, a carboxyl group, and a hydroxyl group is 40 to 100% by weight, and an unsaturated monomer having a crosslinkable functional group is more preferable. The monomer portion is 0 to 50% by weight, and the other unsaturated monomer portion is 0 to 50% by weight. However, when the hydrophilic substituent is only an amide group, the portion of the unsaturated monomer having an amide group is 40 to 97% by weight, the portion of the unsaturated monomer having a crosslinkable functional group is 3 to 50% by weight, and others. Preferably, the polymer is composed of 0 to 50% by weight of an unsaturated monomer portion, more preferably 50 to 95% by weight of an unsaturated monomer portion having an amide group, and more preferably a polymer having an unsaturated monomer portion having a crosslinkable functional group. 5-
40% by weight, and the amount of other unsaturated monomers is 0 to
50% by weight. Note that the unsaturated monomer having an amide group, a carboxyl group, a hydroxyl group, and a sulfonic acid group is an unsaturated monomer having a hydrophilic substituent and an unsaturated monomer having a crosslinkable functional group. In the composition of the hydrophilic polymer, the unsaturated monomer having an amide group, a carboxyl group, a hydroxyl group, and a sulfonic acid group is regarded as an unsaturated monomer having a hydrophilic substituent, and as an unsaturated monomer having a crosslinkable functional group, It shall not be calculated.

In the lithographic printing plate precursor according to the present invention, a water-insoluble photosensitive layer containing the above-mentioned photosensitive composition is provided on a substrate. Specific examples of the substrate used in this case include an aluminum plate, Metal plates such as steel plates, stainless steel plates, copper plates and alloy plates of these metals, polyester, nylon, polyethylene, polypropylene, polycarbonate, ABS resin,
Examples include a plastic film or paper such as cellulose acetate, paper laminated with aluminum foil, metallized paper, plastic film laminated paper and the like. The thickness of these substrates is not particularly limited, but is usually about 100 to 500 μm.
These substrates may be subjected to a surface treatment such as an oxidation treatment, a zinc phosphate treatment, a sand blast treatment, a corona discharge treatment or the like to improve the adhesion. Further, treatment with a polymer may be carried out in order to improve the adhesion to the photosensitive layer or to prevent diffusion of heat. Further, in the case of a printing plate from which the photosensitive layer is removed by exposure, the substrate surface must be made lipophilic (ink), and if the lipophilicity of the substrate surface is insufficient, a lipophilic polymer is applied. And a photosensitive layer.

In order to provide a photosensitive layer on the substrate, a solution containing the photosensitive composition of the present invention may be applied to the substrate, dried and cured. The method of application varies depending on the viscosity of the solution to be applied, the application speed, and the like. Usually, for example, a roll coater, a blade coater, a gravure coater, a curtain flow coater, a die coater, a spray method, or the like may be used.

At this time, various additives such as an antifoaming agent, a leveling agent, an anti-cissing agent and a coupling agent may be used in the coating solution for defoaming the coating solution and for smoothing the coating film. . Further, an organic or inorganic filler may be used in order to improve characteristics such as water resistance of the photosensitive layer. Further, a lipophilic resin such as an acrylic resin emulsion, a styrene resin emulsion, a vinyl acetate resin emulsion, a butadiene rubber emulsion, and an aqueous polyurethane resin may be added. When these are added, the photosensitive layer has a phase separation structure between the crosslinked hydrophilic polymer phase and these lipophilic resin phases. After applying the solution of the photosensitive composition, it is heated to dry and crosslink the hydrophilic polymer. The heating temperature is usually about 50 to 200 ° C. When using polyvinyl alcohol as the hydrophilic polymer of the photosensitive layer and insolubilizing the polymer by crystallizing the polymer, it is preferable to dry at 130 ° C. or higher and cool the mixture. The thickness of the photosensitive layer is not particularly limited, but is usually preferably about 0.5 to 10 μm.

In the printing original plate of the present invention, after forming the photosensitive layer, a film may be laminated on the photosensitive layer to protect the photosensitive layer.

Next, the photosensitive layer of the present invention will be described in detail. The planographic printing plate of the present invention is a plate for offset printing using fountain solution, and therefore the photosensitive layer is required to have hydrophilicity and water resistance (not to be dissolved in fountain solution). The photosensitive layer irradiated with light by exposure partially decomposes, and changes from hydrophilic to lipophilic (ink). Therefore, operations such as development and wiping are not required after exposure. Further, even when the photosensitive layer in the exposed portion is removed, the photosensitive layer itself generates heat by absorbing light, and uses a polymer which is easily gasified and decomposed as described above. Very few, and in this case, development or wiping is not required after exposure.

The water-insoluble photosensitive layer of the present invention repels ink due to the adhesion of dampening water to the unexposed areas during printing. The property that water adheres and repels ink is basically required only on the surface of the layer, but when the layer is made of a hydrophilic polymer, the photosensitive layer absorbs water and repels ink. . On the other hand, in the exposed portion, it is required that ink adhere without water. From these points, the water absorption of the photosensitive layer is preferably about 15 to 400%. When the water absorption is less than 15%, the adhesion of water is insufficient and the background becomes dirty. On the other hand, when the water absorption exceeds 400%, the photosensitive layer swells by absorbing water, and the photosensitive layer and the substrate or the adhesive, etc. A large stress is generated at the interface with the polymer layer to cause separation of the photosensitive layer, which is not preferable. From these points, the water absorption is more preferably 20 to 300%. The water absorption was measured by immersing the photosensitive layer in water at room temperature for 1 hour and then wiping the weight of the surface by wiping the water.
Assuming that the weight after drying at 1 ° C. for 1 hour is Wdry, water absorption = (Wwet−Wdry) / Wdry. In the measurement, the thickness of the photosensitive layer of the actual printing plate is very small. Therefore, even if measurement is performed on the substrate on which the film is formed, a thick film is formed on the substrate so that the measurement can be performed separately. It can also be measured by peeling off from.

In the present invention, when the photosensitive layer is partially decomposed by exposure, a gas is generated and the photosensitive layer may foam. In addition, the photosensitive layer in the exposed portion may be raised from the unexposed portion due to foaming. Even when the photosensitive layer is raised by foaming, when printing is started, the raised may be reduced or eliminated by printing pressure.

The wavelength of light used for exposing the printing original plate of the present invention is 750 to 1100 nm, and in this wavelength range, light that matches the absorption wavelength range of the light absorber may be used. As a light source used for exposure, a light source that is easy to use and has a high output is suitable. Lasers, especially 7
A laser having an oscillation wavelength in the wavelength range of 50 to 1100 nm is preferable, for example, a high-output semiconductor laser of 830 nm or a YAG laser of 1064 nm is preferable. An exposure machine equipped with these lasers has already been used as a so-called thermal plate setter (exposure machine). Served on the market.

[0051]

Embodiments of the present invention will be described below. [Examples 1 and 2] (Synthesis of hydrophilic polymer) Water 400 was placed in a 1000 cc flask.
g, bubbling nitrogen to remove dissolved oxygen, and raise the temperature to 80 ° C. While flowing nitrogen gas through the flask, a monomer solution consisting of 90 g of acrylamide, 30 g of acrylic acid, and 77 g of water and an aqueous solution of an initiator in which 0.5 g of potassium persulfate was dissolved in 50 g of water were separated while maintaining the internal temperature at 80 ° C. For 3 hours. After completion of the dropwise addition, polymerization was continued at 80 ° C. for 2 hours, followed by further polymerization at 90 ° C. for 2 hours. Finally, 150 g of water was added, and the pH was adjusted to 4.5 with an aqueous ammonia solution to synthesize an aqueous solution of a hydrophilic polymer. . The aqueous solution of this polymer has a viscosity of 38000 mPa · s and a solid content of 15% by weight.
Met.

(Photosensitive composition) Next, 80 parts by weight of the above hydrophilic polymer in solid content, and 20 parts by weight of Cymel 350 (methylated melamine resin manufactured by Mitsui Cytec Co., Ltd.) as a cross-linking agent were solidified and cured. As an accelerator, 1 part by weight of paratoluenesulfonic acid and 5 parts by weight of a dye dissolved in 100 parts by weight of water (Chemical Formula 6) or (Chemical Formula 7) were mixed and stirred with a disper until uniform.

[0053]

Embedded image

[0054]

Embedded image

(Preparation of printing original plate) The above photosensitive composition was applied to a 0.2 μm polyester film using a blade coater, and then dried at 120 ° C. for 1 hour to form a photosensitive layer having a thickness of 2 μm. A printing master was created.

(Evaluation) In order to evaluate the printing characteristics, information was recorded by scanning a laser beam while condensing 830 nm semiconductor laser light on this plate. The portion irradiated with the laser light turned from blue to gray. The sensitivity was approximately 300 mJ / cm ² . When the cross section of this plate was observed with a microscope,
In each of the examples, the photosensitive layer in the exposed portion was foamed and protruded from the unrecorded portion. Further, when the periphery of the exposed portion was observed with a microscope, no decomposition product was deposited. The exposed plate was set on an offset printing machine using a dampening solution and printing was performed. In the printing plates of Examples 1 and 2, the ink was not attached at all to the unirradiated portion of the light, while the ink was sufficiently adhered to the irradiated portion, and there was no printing defect considered to be due to decomposition products, and the printing plate was clean. Printing was completed (the property is hereinafter referred to as printability). Also, the resolution and printing durability were excellent. It should be noted that there was no problem at all when the plates were handled in a normal light room.

[Examples 3 to 5, Comparative Examples 1 and 2] In the synthesis of the hydrophilic polymer of Example 1, the unsaturated monomers shown in Table 2 were used in place of acrylamide, and the initiator was persulfuric acid. V is a water-soluble azo initiator instead of potassium
-50 (product of Wako Pure Chemical Industries, Ltd.) and the pH of the polymerization solution
Was constantly maintained at 8 to 9 with triethylamine, and a hydrophilic polymer was synthesized in the same manner as in Example 1. Next, Table 1
In a solution consisting of 20 parts by weight of a hydrophilic polymer, 20 parts by weight of water and the kind and part by weight of the type shown in Table 1, a cyanine compound was used as a light absorber, and 5 parts by weight of Example 1 were used. A photosensitive composition was made in the same manner. The amounts in Table 1 represent parts by weight of the solid content.

Next, in order to improve the adhesiveness, a photosensitive composition was applied to a 0.2-mm-thick aluminum plate on which S-lec BM-2 (butyral resin, a product of Sekisui Chemical Co., Ltd.) having a thickness of 2 μm was previously applied as a primer. The resultant was applied and dried at 160 ° C. for 1 hour to prepare a printing master having a photosensitive layer having a thickness of 3 μm.

Using this plate, exposure was performed in the same manner as in Example 1 except that a semiconductor laser having an oscillation wavelength of 810 nm was used, and the exposed portions were observed and printed. Sensitivity (mJ /
cm ² ) are 200, 280, 220, 230 in order from Example 3.
In each of the plates, the photosensitive layer in the exposed portion foamed and was raised more than the unexposed portion. In addition, no droplets such as decomposition products were observed around the exposed portion. As for the evaluation results of printing, the plates of Examples 3 to 5 were excellent in printability and printing durability, but the plates of Comparative Examples 1 and 2 were heavily soiled and could not be printed cleanly. In addition, there was no problem in handling any of the plates in a normal light room.

[0060]

[Table 1]

[Examples 6 to 8] In Example 1, 60 g of acrylic acid, 20 g of hydroxyethyl acrylate,
Acrylonitrile 30 g, ethyl acrylate 10 g,
A hydrophilic polymer was prepared in the same manner as in Example 1 except that a monomer solution consisting of water and 77 g of water was used. A photosensitive composition was prepared using 70 parts by weight of the hydrophilic polymer as solids and 30 parts by weight of the cross-linking agent shown in Table 2 and 10 parts by weight of a light absorber in the same manner as in Example 3. An original plate for printing was prepared, and exposure and printing evaluation were performed. The sensitivities (mJ / cm ² ) were 170, 200, and 180 in the order from Example 7, and in each of the plates, the photosensitive layer in the exposed portion foamed and was raised more than the unexposed portion. In addition, no droplets such as decomposition products were observed around the exposed portion. The printing evaluation results showed that all the plates were excellent in printability and printing durability.

[0062]

[Table 2]

[0063]

The present invention provides a hydrophilic polymer having a hydrophilic substituent,
Offset printing plates using a photosensitive composition comprising a specific cyanine compound and a cross-linking agent as a light absorbing agent in the photosensitive layer are known as 7
Sensitive to light in the region of 50-1100 nm, good sensitivity,
It has high resolution, does not require operations such as development and wiping, has excellent hydrophilicity and water resistance, does not stain, has excellent printability, and has excellent printing durability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 101/02 C08L 101/02 101/14 101/14 C09B 23/00 C09B 23/00 L G03F 7/00 503 G03F 7/00 503 (72) Inventor Sumio Hirose 580 No. 32, Takuji Nagaura, Sodegaura-shi, Chiba F-term in Mitsui Chemicals, Inc. (Reference) 2H025 AA01 AA02 AA12 AB03 AC08 AD01 BD03 BH01 CB30 CB41 CB42 CB43 CB51 CC13 CC17 FA10 2H096 AA06 BA06 EA04 EA23 2H114 AA04 AA22 AA23 AA24 BA01 BA10 DA21 DA43 DA50 DA51 DA52 DA53 DA64 EA01 FA16 4H056 CA01 CA02 CA05 CC02 CC08 CE03 DD03 4J002 BG121 BG131 BJ001 EE017 ER007 EU0206 FD007

Claims (9)

[Claims] 1. A photosensitive composition comprising a hydrophilic polymer, a cyanine compound represented by the following general formula (1), and a crosslinking agent, directly or via another layer on a substrate,
An original printing plate having a photosensitive layer insoluble in water. Embedded image [Wherein, R ^1, R ² is an alkyl group, an alkyl group partially replaced with another atom or atomic _{group, A m, A n, A} O, A P
Is a sulfonic acid group or a sulfonate, Y is a hydrogen atom, an alkyl group, a halogen atom, or a functional group obtained by substituting a halogen atom, Z is a hydrogen atom or an alkylene group forming a cyclic structure, and It can be replaced by another atom or group. Further, n and m each independently represent 0 to 6. o and p each independently represent 0 to 1. The number of sulfonic acids or sulfonates in the molecule is m + n + o + p ≧ 1. X is a monovalent anion,
However, when the N ^{+ of the} naphtho condensed ring and the sulfonic acid group form a salt in the molecule, it may be omitted. ] 2. The printing original plate according to claim 1, wherein the hydrophilic polymer is a polymer obtained by copolymerizing the following (A) and (B). (A) an unsaturated monomer having an amide group and (B) a copolymerizable with the unsaturated monomer, and a carboxyl group,
A monomer selected from monomers having one or more hydrophilic substituents selected from sulfonic acid groups, phosphonic acid groups and hydroxyl groups in one or more side chains. 3. The printing plate precursor according to claim 2, wherein the hydrophilic polymer is obtained by polymerizing an unsaturated monomer having an unsubstituted or substituted amide group. 4. 97 to 50% by weight of the hydrophilic polymer, 3 to 50% by weight of the crosslinking agent, and 10% by weight of the hydrophilic polymer and the crosslinking agent.
The printing original plate according to any one of claims 1 to 3, which contains 2 to 20 parts by weight of the cyanine compound represented by the general formula (1) based on 0 part by weight. 5. The printing plate precursor according to claim 1, wherein the photosensitive layer is partially decomposed by irradiating the printing plate with light to change the hydrophilicity of the photosensitive layer to ink-philicity. Print version. 6. The printing original plate according to claim 1, which has a photosensitive layer on a lipophilic surface. 7. A printing plate from which the photosensitive layer has been removed by irradiating the printing plate precursor according to claim 6 with light. 8. The printing plate according to claim 5, wherein the irradiation light has a wavelength of 750 to 1100 nm. 9. A photosensitive composition contained in the photosensitive layer of the printing plate precursor according to claim 1. Description: