JP2001031876A - Photosensitive composition and printing plate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition usable as a plate for a computer to plate(CTP) method, handleable in a bright room without requiring development or wiping off operations and excellent in printing characteristics by including a hydrophilic polymer having specific functional groups in the side chain, a cross-linking agent and a light absorber. SOLUTION: This composition comprises (B) a cross-linking agent (preferably an amino resin) and (C) a light absorber (preferably the one having light absorptivity in a region at 750-1,100 nm wavelength) in (A) a hydrophilic polymer having (i) amide group and (ii) one or more cross-linking functional groups selected from carboxyl group, sulfonic acid group, phosphonic acid group and hydroxyl group as a side chain. The mixing ratio of the respective components in the composition is preferably 97-40 wt.% of the component A, 3-60 wt.% of the component B and the component C in an amount of 2-20 pts.wt. based on 100 pts.wt. of the sum total of the components A and B. The offset printing plate using the composition as a photosensitive layer is excellent in hydrophilicity and water resistance and is capable of exhibiting various excellent printing characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing plate, in particular, it is sensitive to light in the near infrared region and can be handled in a bright room.
A photosensitive composition that can be directly drawn on a plate with a laser, does not require development and wiping operations, and has excellent printing characteristics and is used in a lithographic printing plate, particularly a lithographic printing plate using a fountain solution. The present invention relates to a printing plate using the conductive composition.

[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, the digitization of information and the increase in the output of lasers have led to the use of lasers instead of the above-mentioned underlaying films in the production of printing plates. To do so-called CTP (Computer)
to Plate) method has been put to 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, although this plate can be handled in a bright room and has excellent resolution, it 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 is also disclosed. 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, and a defect occurs in the image portion, resulting in poor printing.

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.
The plate is exposed by so-called ablation. This plate can be handled in a bright room, and no processing such as development or wiping is required.However, a large amount of energy is required to remove the light absorbing layer and the hydrophilic layer or the ink repellent layer thereon, and the exposure takes a long time. In addition, a part of the removed light absorbing layer and the hydrophilic layer or the ink repellent layer thereon and the decomposed product are deposited on the unexposed hydrophilic layer or the ink repellent layer around the exposed portion of the plate. However, there is a problem that the property that ink does not adhere is reduced.

Further, a method is proposed in which another substrate is brought into close contact with a substrate having a light absorbing layer containing a resin or the like, and light is irradiated, and the light absorbing layer or the like is transferred to the other substrate by heat generated at that time. However, in this method, it is difficult to uniformly adhere the substrates to each other due to the attachment of dust and the like, a large amount of energy is required for transfer, and the strength of the transferred light absorbing layer is increased. However, there is a drawback that the film is weak and peels off during printing.

[0009]

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, in the present invention, a photosensitive composition used in a CTP plate that can be handled in a bright room, does not require development and wiping operations, and has excellent sensitivity, resolution and various printing characteristics, and the photosensitive composition An object of the present invention is to provide a printing plate using the composition.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and completed the present invention specified by the following (1) to (8).

(1) As a side chain of the polymer (A),
(B) A photosensitive composition comprising a hydrophilic polymer having a functional group and a crosslinking agent and a light absorbing agent. (A) an amide group, (B) one or more crosslinkable functional groups selected from a carboxyl group, a sulfonic acid group, a phosphonic acid group and a hydroxyl group.

(2) 97 to 40% by weight of a hydrophilic polymer,
2. The photosensitive composition according to claim 1, comprising 2 to 20 parts by weight of a light absorber per 100 parts by weight of a composition comprising 3 to 60% by weight of a crosslinking agent.

(3) The photosensitive composition according to claim 1 or 2, wherein the hydrophilic polymer is obtained by copolymerizing the unsaturated monomers (C) and (D). (C) one or more unsaturated monomers selected from unsaturated monomers having an amide group and (D) unsaturated monomers having a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group.

(4) The photosensitive composition according to any one of (1) to (3), wherein the hydrophilic polymer has the following composition. A portion having an amide group 30 to 97% by weight, a portion having a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group 3 to 60% by weight, and other portions 0 to 50% by weight.

(5) The photosensitive composition according to (3) or (4), wherein the unsaturated monomer having an amide group is unsubstituted or substituted acrylamide, N-vinylformamide, N-vinylacetamide or N-vinylpyrrolidone.

(6) The crosslinking agent is an amino resin (1)-
The photosensitive composition according to any one of (5).

(7) The light absorber has a wavelength of 750 to 1100 n
(1) to (6) having a light absorbing ability in the region of m
The photosensitive composition according to any one of the above.

(8) Directly on a substrate or through another layer,
A printing plate having a photosensitive layer containing the photosensitive composition according to any one of (1) to (7).

The photosensitive composition of the present invention is a composition containing a crosslinking agent and a light absorbing agent in a hydrophilic polymer,
The hydrophilic polymer has an amide group as an essential component as a side chain, and further has one or two crosslinkable functional groups selected from a carboxyl group, a sulfonic group, a phosphonic group, and a hydroxyl group.
It has more than one species. The polymer is obtained, for example, by copolymerizing an unsaturated monomer having an amide group and an unsaturated monomer having a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group.

The unsaturated monomer having an amide group used in the production of the hydrophilic polymer of the present invention includes unsubstituted or substituted (meth) acrylamide, N-vinylpyrrolidone, N-vinylacetamide, N-vinylformamide, unsubstituted Or substituted itaconic amide, unsubstituted or substituted fumaric acid amide, unsubstituted or substituted maleic amide, 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. In the case of a dibasic acid amide such as the aforementioned itaconic acid amide, a monoamide in which one carboxyl group is amidated may be used, or a diamide in which both carboxyl groups are amidated. In the hydrophilic polymer of the present invention, one or more kinds of unsaturated monomers having an amide group may be used.

In the present invention, the unsaturated monomer having an amide group may be unsubstituted or substituted acrylamide, N-vinylformamide, N-vinylacetamide, N-vinyl, or the like. Pyrrolidone is preferred.

The unsaturated monomer having a carboxyl group used for producing the hydrophilic polymer of the present invention includes:
Monobasic unsaturated acids such as (meth) acrylic acid, itaconic acid,
Examples of dibasic unsaturated acids such as fumaric acid, maleic acid and anhydride thereof, monoesters and monoamides of these dibasic unsaturated acids, and unsaturated monomers having a sulfonic acid group include sulfoethyl (meth) acrylate, (Meth) acrylamidomethylpropanesulfonic acid, vinylsulfonic acid, vinylmethylsulfonic acid, isopropenylmethylsulfonic acid, ethylene oxide to (meth) acrylic 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 reaction product of a monoalkyl sulfosuccinate and glycidyl (meth) acrylate, and Antox MS60 of Nippon Emulsifier Co., Ltd., as a polymerizable unsaturated monomer having a phosphonic acid group, vinyl vinyl phosphate, Mono (2-hydroxyethyl) phosphate (meth)
Acrylate, monoalkyl phosphate mono (2
-Hydroxyethyl) (meth) acrylate and the like. Propyl sulfonate (meth) acrylamide and the like. Monomers having these carboxyl groups, sulfonic acid groups or phosphonic acid groups are sodium hydroxide,
Inorganic bases such as potassium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, alkylamines such as triethylamine, monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, dimethylethanolamine, diethylethanol It may be neutralized with an amine such as an alkanolamine such as an amine. Further, it may be neutralized after the polymerization.

In the present invention, an unsaturated monomer having a hydroxyl group described below is copolymerized, and an acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride or hexahydrophthalic anhydride is added to the hydroxyl group to form a carboxyl group. May be introduced.

Examples of the unsaturated monomer having a hydroxyl group used for producing the hydrophilic polymer of the present invention include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, methylol (meth) acrylamide, and the like. Methoxymethyl (meth) which is a condensate of the methylol (meth) acrylamide with methyl alcohol or butyl alcohol
Acrylamide and butoxymethyl (meth) acrylamide are also one kind of a monomer having a hydroxyl group in the present invention. Further examples include carboxylic acid and amine adducts of glycidyl (meth) acrylate. Further, a polymer obtained by copolymerizing vinyl acetate may be hydrolyzed.

These carboxyl groups, sulfonic groups,
One or more unsaturated monomers having a phosphonic acid group or a hydroxyl group may be used. Naturally, monomers having different substituents, such as an unsaturated monomer having a carboxyl group and an unsaturated monomer having a hydroxyl group, can be used in combination.

Further, the other copolymerizable unsaturated monomer used for producing the hydrophilic polymer of the present invention is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl ( Meta)
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 are included.

In the above description of the unsaturated monomers, (meth) acryl, (meth) acryloyl in (meth) acrylamide and (meth) acrylic acid, and (meth) acrylate, etc. It means both methacryl, acryloyl and methacryloyl, and acrylate and methacrylate.

In the hydrophilic polymer of the present invention, the proportion of a portion having an amide group is preferably from 30 to 97% by weight, more preferably from the viewpoint of balance between hydrophilicity and water resistance of the photosensitive layer and various printing characteristics. Is 50 to 95% by weight, the portion having a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group is 3 to 60% by weight, more preferably 5 to 50% by weight, and the other portion is 0 to 50% by weight. More preferably, it is 0 to 40% by weight.

The portion having an amide group means a portion derived from an unsaturated monomer having an amide group, that is, the entire unsaturated monomer, and the above-mentioned unsaturated group having a carboxyl group, a sulfonic acid group or a phosphonic acid group. A monomer that is neutralized is also a portion having a carboxyl group or a sulfonic acid group. Further, a copolymer obtained by copolymerizing an unsaturated monomer having a hydroxyl group and then adding an acid anhydride to the hydroxyl group to introduce a carboxyl group is a portion having a carboxyl group.

The hydrophilic polymer according to the present invention comprises the above-mentioned unsaturated monomer having an amide group, a carboxyl group,
Using a radical polymerization initiator, a mixture of an unsaturated monomer having a sulfonic acid group, a phosphonic acid group or a hydroxyl group, and, if necessary, other copolymerizable unsaturated monomers, in a lump or with a solvent such as alcohol. From normal temperature to 15
It is obtained by polymerizing in a usual manner at a temperature of 0 ° C.

Examples of the radical polymerization initiator used in this case include persulfates such as potassium persulfate and ammonium persulfate, peroxides such as benzoyl peroxide, dibutyl peroxide and cumene hydroperoxide, and azobisisobutyrate. Examples include azo compounds such as lonitrile and azobisvaleronitrile. In addition, a chain transfer agent such as a mercaptan may be used in the polymerization, or various reducing agents or amines may be used when a radical is generated by a redox reaction.

The photosensitive composition of the present invention comprises a hydrophilic polymer,
It contains a cross-linking agent and a light absorbing agent, and the mixing ratio is 97 to 40% by weight, preferably 95 to 95% by weight of the hydrophilic polymer in terms of solid content, in view of the balance between hydrophilicity and water resistance of the photosensitive layer and various printing characteristics. 45% by weight, more preferably 90 to 50% by weight, the cross-linking agent is 3 to 60% by weight, preferably 5 to 55% by weight, more preferably 10 to 50% by weight, and the light absorber crosslinks with the hydrophilic polymer. The amount is preferably 2 to 20 parts by weight based on 100 parts by weight of the total solid content of the agent.

The crosslinking agent used in the present invention may be any one which improves the water resistance of the hydrophilic polymer by performing a crosslinking reaction with the hydrophilic polymer. For example, a crosslinking functional group in the hydrophilic polymer may be used. A carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group, and in some cases, a polyhydric alcohol compound that reacts with an amide group, a polyvalent carboxylic acid compound or an anhydride thereof, a polyvalent glycidyl compound,
Examples include a polyvalent isocyanate compound, an epoxy resin, an oxazoline resin, an amino resin, and a phenol resin.

In order to satisfy both hydrophilicity and water resistance, the photosensitive layer of the present invention has a phase separation structure of a hydrophilic phase and a hydrophobic phase, and has a large affinity between the hydrophilic phase and the hydrophobic phase. Preferably, a part of the cross-linking agent reacts with the hydrophilic polymer to form a phase mainly composed of the hydrophilic polymer, and the remaining cross-linking agent self-cross-links to form a phase composed mainly of the cross-linking agent. It is preferable to adopt a separation structure. In this regard, and in the present invention, among the crosslinking agents described above, from the curing speed and the stability of the photosensitive composition, etc., the hydrophilicity of the photosensitive layer among the crosslinking agents described above in the present invention is considered. Amino resins are preferred from the viewpoint of the balance of water resistance and the like. Examples of the amino resin include melamine resin, urea resin, benzoguanamine resin and glycoluril resin obtained by reacting melamine, urea, benzoguanamine and glycoluril with formalin and formalin and alcohol, and modified resins of these resins, such as carboxy-modified resin. Melamine resins and the like can be mentioned. When the above-mentioned amino resin is used, an acidic compound such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, ammonium chloride or the like may be used in combination in order to promote a crosslinking reaction.

Examples of the light absorbing agent used in the present invention include dyes and pigments having a light absorbing ability in a wavelength range of 750 to 1100 nm. More specifically, cyanine dyes, polymethine dyes, phthalocyanine dyes, naphthalocyanine dyes, anthracyanine dyes, azo dyes, benzoquinone dyes, naphthoquinone dyes, dithiol metal complexes, metal complexes of diamines And carbon black. These light absorbers may be dissolved or dispersed in the photosensitive composition.

The photosensitive composition of the present invention comprises the above-mentioned hydrophilic polymer, cross-linking agent, light absorbing agent, and, if desired, a curing accelerator such as an acid or a base, an antifoaming agent, a leveling agent, an anti-repellent agent and a coupling. It is obtained by mixing additives such as agents.
Further, in order to further improve the hydrophilicity of the photosensitive layer, water resistance and ink landing properties, an inorganic filler or an organic filler, and a styrene emulsion, an acrylic emulsion, a vinyl acetate emulsion, a butadiene emulsion, a urethane resin emulsion, A resin emulsion such as an epoxy resin emulsion may be added.

The printing plate of the present invention is obtained by forming a photosensitive layer containing the above-mentioned photosensitive composition on a substrate, and the substrate used in this case is an aluminum plate, a steel plate, polyester,
Examples include plastic films such as nylon and polypropylene, and paper. The thickness of these substrates is not particularly limited, but is usually about 100 to 400 μm.

In the present invention, a photosensitive layer composed of the photosensitive composition is formed on the substrate. At this time, in order to improve the adhesion of the photosensitive layer to the substrate, heat diffusion is performed. One or more intermediate layers may be provided between the substrate and the photosensitive layer to prevent or prevent halation of the irradiated light, or the surface of the substrate may be subjected to, for example, corona discharge treatment or rough surface treatment. May be performed.

In the present invention, a method for forming a photosensitive layer includes a method of applying a solution of a photosensitive composition, and the method of applying the solution varies depending on the viscosity of the solution to be applied and the application speed. For example, a roll coater, a blade coater, a gravure coater, a curtain flow 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-repellent agent, and a coupling agent may be used in the solution of the photosensitive composition for defoaming and for smoothing the film. After applying the photosensitive composition, it is dried by heating, and the photosensitive layer is crosslinked and cured. The heating temperature is usually about 50 to 200 ° C. The thickness of the photosensitive layer is not particularly limited, but is preferably about 0.5 to 10 μm.

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

The printing plate of the present invention has a wavelength of 750 to 1100 n.
It has photosensitivity to light in the region of m. By exposing the plate to the light in the area and recording the information, a plate actually used for printing can be made. For example, equipped with a high-power semiconductor laser of 830 nm or a YAG laser of 1064 nm,
What is necessary is just to use a plate setter (exposure machine) for a so-called thermal plate.

The photosensitive layer of the printing plate of the present invention absorbs irradiation laser light and generates heat. Due to this heat generation, the light absorbing agent is decomposed, and the hydrophilic polymer is also partially decomposed, resulting in swelling. Then, the photosensitive layer in the portion irradiated with the laser light foams and, in some cases, bulges. Although the mechanism is unknown, the light-irradiated part of the photosensitive layer changes its property from hydrophilic to ink-philic, and ink adheres to the laser-irradiated part without developing or wiping. Printing is possible. The details of the mechanism by which the irradiated portion of the laser beam changes from hydrophilic to ink-philic are unknown, but amide groups, carboxyl groups, hydroxyl groups, etc., which are hydrophilic groups,
Further, it is considered that the ink becomes lipophilic due to the crosslinking progressing due to the detachment or the like and the water absorption rate decreasing. Also,
The photosensitive layer of the printing plate of the present invention has excellent resolution, halftone dot reproducibility and printing durability. Of course, it can be handled in the light room.

[0043]

Embodiments of the present invention are described below.

[Examples 1 to 3 and Comparative Examples 1 and 2] (Synthesis of hydrophilic polymer)
After adding 0 g and removing dissolved oxygen by bubbling nitrogen, the temperature is raised to 80 ° C. While flowing nitrogen gas into the flask, 75 g of acrylamide, 8 g of acrylic acid, 10 g of hydroxyethyl acrylate and 27 g of acrylonitrile 27 were used.
g and a water solution of an initiator prepared by dissolving 0.5 g of potassium persulfate in 50 g of water were separately dropped continuously over 3 hours while maintaining the internal temperature at 80 ° C. After the completion of the dropwise addition, polymerization was continued at 80 ° C. for 2 hours, and further polymerization was performed at 90 ° C. for 2 hours. Finally, 150 g of water was added.
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 had a viscosity of 3000 mPa · s and a solid content of 15% by weight. The composition of the hydrophilic polymer has an amide group moiety of 62.5
% By weight, a portion having a carboxyl group and a hydroxyl group was 15% by weight, and the other portion was 22.5% by weight.

(Photosensitive composition) Next, the above hydrophilic polymer and Cymel 325 (a methylated melamine resin manufactured by Mitsui Cytec Co., Ltd.) as a cross-linking agent were solid parts by weight as shown in Table 1 and further cured. A photosensitive composition was prepared by mixing 1 part by weight of paratoluenesulfonic acid as an accelerator and 5 parts by weight of IR-125 (cyanine dye manufactured by ACROSS) as a light absorber.

[0046]

[Table 1]

(Preparation of Printing Plate) The above photosensitive composition was applied to a 0.2 mm polyester film using a doctor blade, and then dried at 120 ° C. for 3 hours to form a photosensitive layer having a thickness of 3 μm. Thus, a printing plate was prepared.

(Evaluation) Information was recorded on this plate by scanning light while collecting light from a semiconductor laser (manufactured by SDL, USA) having an output of 500 mW and an oscillation wavelength of 830 nm. The portion irradiated with the laser light turned from blue to gray. The sensitivity was approximately 300 mJ / cm ² . 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 to 3, no ink was applied to the non-irradiated portions, while the ink was sufficiently adhered to the irradiated portions, and a clean print was obtained (hereinafter, this property is referred to as printability). ). In addition, it was excellent in high resolution and printing durability.

On the other hand, the printing plate of Comparative Example 1 was inferior in water resistance of the photosensitive layer due to an insufficient amount of the crosslinking agent, and swelled and peeled off with a dampening solution when printing the photosensitive layer with a very small amount of printing. I could not print. Further, in the printing plate of Comparative Example 2, since the amount of the hydrophilic polymer was small, the fountain solution did not sufficiently adhere to the unexposed portion of the photosensitive layer due to insufficient hydrophilicity. As a result, the ink partially adhered. And I couldn't print neatly. It should be noted that there was no problem at all when the plates were handled in a normal light room.

[Examples 4-6, Comparative Examples 3-5] Example 1
Monomer mixture 1 having the weight composition shown in Table 2 in the same manner as
A hydrophilic polymer was synthesized by polymerization using an aqueous monomer solution consisting of 20 g and 77 g of water.

[0051]

[Table 2]

A compounded liquid comprising 70 parts by weight of the hydrophilic polymer shown in Table 2 in solid content, 30 parts by weight of a crosslinking agent of the type shown in Table 3 in solid content, and 1 part by weight of dodecylbenzenesulfonic acid as a curing accelerator. After adding 7 parts by weight of the light absorbing agent shown in Table 3, the light absorbing agent was kneaded with three rolls to prepare a photosensitive composition. Example 1 using this photosensitive composition
A printing plate was prepared in the same manner as described above, exposed and printed, and evaluated for sensitivity (mJ / cm ² ), resolution, printability and printing durability.

The sensitivities of the printing plates of Examples 4 to 6 were 2
It was 50, 250, and 200 mJ / cm ² , and the resolution, printability, and printing durability were all excellent. On the other hand, Comparative Example 3
The plates of Nos. 1 to 4 had a sensitivity of 250 mJ / cm ² without any problem, but the printing plate of Comparative Example 3 was poor in water resistance of the photosensitive layer. The printing durability was poor, and the resolution and printability could not be evaluated. Although the printing plates of Comparative Examples 4 and 5 had no problem in printing durability, the ink adhered vigorously to the unexposed portions, and the printing properties were poor, and the resolution could not be evaluated. It should be noted that there was no problem at all when the plates were handled in a normal light room.

[0054]

[Table 3]

[Examples 7 to 10] In the synthesis of the hydrophilic polymer of Example 1, Example 7 used a monomer having an amide group shown in Table 4 in place of acrylamide, and Example 8 used a monomer in place of acrylamide. The amide groups shown in Table 4 were replaced with the monomers having amide groups shown in Table 4 and the monomers having sulfonic acid groups shown in Table 4 in place of acrylic acid. A hydrophilic polymer was synthesized in the same manner as in Example 1 except that a monomer having a group was used. Next, a photosensitive composition was prepared according to the same formulation as in Example 1. Next, in order to improve the adhesiveness, the photosensitive composition is applied to an aluminum plate having a thickness of 0.2 mm to which a butyral resin having a thickness of 2 μm is applied as a primer in advance, and dried at 160 ° C. for 1 hour, and then dried at a temperature of 160 ° C. A printing plate having a photosensitive layer was prepared.

Using this plate, exposure and printing were performed in the same manner as in Example 1, and evaluation was performed. The sensitivities are 330 and 3, respectively.
50, 250, and 300 mJ / cm ² , and all the plates were excellent in resolution, printability, and printing durability. It should be noted that there was no problem at all when the plates were handled in a normal light room.

[0057]

[Table 4]

[0058]

The photosensitive composition of the present invention comprises an amide group in the side chain and one type of crosslinkable functional group selected from the group consisting of a carboxyl group, a sulfonic acid group, a phosphonic acid group and a hydroxyl group. Or, an offset printing plate comprising a hydrophilic polymer having two or more kinds, a crosslinking agent and a light absorbing agent, and using the photosensitive composition for a photosensitive layer is excellent in hydrophilicity and water resistance, and has a wavelength of 750 to 1100 nm. It does not require operations such as development or wiping, and is excellent in printing characteristics such as good sensitivity, resolution and printing durability, without requiring operations such as development and wiping.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G03F 7/00 503 G03F 7/00 503 7/004 521 7/004 521 7/033 7/033 (72) Inventor Tohru Sato 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemicals, Inc. (72) Inventor Sumio Hirose 580-32 Takuji Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals Inc. Tsuru 580-32, Takuji, Nagaura, Sodegaura-shi, Chiba Prefecture Inside Mitsui Chemicals, Inc.

Claims (8)

[Claims] 1. A photosensitive composition comprising a hydrophilic polymer having functional groups (A) and (B) as side chains of a polymer, a crosslinking agent and a light absorber. (A) an amide group, (B) one or more crosslinkable functional groups selected from a carboxyl group, a sulfonic acid group, a phosphonic acid group and a hydroxyl group. 2. The photosensitive composition according to claim 1, wherein 2 to 20 parts by weight of a light absorber is contained based on 100 parts by weight of a composition comprising 97 to 40% by weight of a hydrophilic polymer and 3 to 60% by weight of a crosslinking agent. Composition. 3. The photosensitive composition according to claim 1, wherein the hydrophilic polymer is obtained by copolymerizing the unsaturated monomers (C) and (D). (C) one or more unsaturated monomers selected from unsaturated monomers having an amide group and (D) unsaturated monomers having a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group. 4. The photosensitive composition according to claim 1, wherein the hydrophilic polymer has the following composition. A portion having an amide group 30 to 97% by weight, a portion having a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group 3 to 60% by weight, and other portions 0 to 50% by weight. 5. An unsaturated monomer having an amide group is substituted or unsubstituted acrylamide, N-vinylformamide,
5. The photosensitive composition according to claim 3, which is N-vinylacetamide or N-vinylpyrrolidone. 6. The cross-linking agent is an amino resin.
The photosensitive composition according to any one of the above. 7. The photosensitive composition according to claim 1, wherein the light absorbing agent has a light absorbing ability in a wavelength range of 750 to 1100 nm. 8. A printing plate having a photosensitive layer containing the photosensitive composition according to claim 1 on a substrate directly or via another layer.