JP2001180144A - Plate for lithographic printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printing plate which is excellent in hydrophilicity and water resistance and free from ablation by the irradiation of light and in which the hydrophilicity of a photosensitive layer is changed to be compatible with ink even without being subjected to development treatment to be excellent in sensitivity, resolution, printability, and printing resistance. SOLUTION: An original plate for lithographic printing contains a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer, and a light absorbent in a substrate. The plate has a photosensitive layer in which a hydrophobic polymer phase is dispersed in a hydrophilic polymer phase. In the printing plate, the hydrophilicity of an irradiation part is made compatible with ink by emitting light to the original plate.

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.
The present invention relates to a planographic printing plate which can be directly drawn on a plate with a laser, does not require a developing or wiping operation, and is excellent in various printing characteristics, particularly 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, 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 Plat)
e) 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, although this plate can be handled in a bright room and has excellent resolution, it still requires development processing.

On the other hand, as a plate which does not require development, US Pat. No. 4,034,183 discloses a water-soluble film-forming organic compound or a water-insoluble reaction of a metal surface with an organic acid or an inorganic acid. There is disclosed a metal plate having a non-photosensitive hydrophilic layer composed of a product, wherein the plate is exposed imagewise and the exposed portion changes to hydrophobic or lipophilic. However, this plate has low sensitivity and requires not only a light source with high output, but also a water-soluble film, which is used as it is, so that the unexposed portion of the film must be dissolved and removed immediately before printing. I had to. Furthermore, a hydrophilic substrate must be used as the substrate, and the surface treatment of the substrate is complicated. Further, a plate having a non-photosensitive hydrophilic layer composed of a water-insoluble reaction product of a metal and a monomer or a polymer acid is also disclosed, but this plate also has low sensitivity and requires a high-output light source. In addition, the resolution was inferior, the adhesion of the hydrophilic layer to the substrate was poor, and the printing durability was poor.

Further, as a plate which does not require development processing, Japanese Patent Application Laid-Open No. Hei 7-314934 discloses a plate in which a silicone 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, causing a defect in the image portion and making it impossible to print well.

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, Japanese Patent Application Laid-Open No. 60-52392 discloses that the surface of a non-water-absorbing resin membrane is hydrophilized by sulfonation, and the sulfonated surface layer is removed by irradiation with light to make it lipophilic. Version is disclosed. In this case, although it depends on ablation, the generation of decomposed matter is very small because it is only the very surface layer, and although this point has been improved, this plate has insufficient hydrophilicity and is easily soiled. ,
The sulfonation treatment is undesirably complicated and dangerous.

[0010] As a version not based on ablation, U
S-3793033 discloses a technique of lipophilicizing a photosensitive layer composed of hydroxyethylcellulose, a phenolic resin, and a photoradical generator by curing by irradiating light. The balance between hydrophilicity and lipophilicity after light irradiation is disclosed. Is not good, and clean printing cannot be performed.

Further, JP-A-7-1850 discloses a photosensitive layer containing a microcapsule containing a lipophilic substance which reacts with a hydrophilic group in the hydrophilic resin in a hydrophilic resin. A technology has been disclosed in which a hydrophilic resin is made lipophilic by destroying the hydrophilic resin. However, this method requires a very small particle size of the microcapsules in order to increase the resolution, and is very difficult to manufacture.

A method is also 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.

Further, Japanese Patent Application Laid-Open No. Hei 10-62970 discloses that PS
The hydrophilicity of a polymer having a phase-separated structure consisting of a phase composed mainly of a hydrophilic polymer and a phase composed mainly of a hydrophobic polymer as a hydrophilic layer instead of the hydrophilic anodized aluminum commonly used for plates A plate consisting of a swelling layer is disclosed. This plate contains a photocrosslinking agent or a photocurable photosensitive compound in the hydrophilic swelling layer, and selectively crosslinks or cures the exposed portion to increase the initial elastic modulus of the hydrophilic swelling layer. It becomes ink-like. However, this plate also requires not only a treatment for washing out the cross-linking agent and the photosensitive compound in the non-exposed area after exposure, but also impregnating or applying the cross-linking agent and the photosensitive compound to the hydrophilic swelling layer. And the production of the original plate was complicated.

[0014]

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, the present invention provides 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 a printing plate drawn by light exposure. It is.

[0015]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and completed the present invention.
That is, the present invention provides: (1) a photosensitive composition comprising a substrate containing a hydrophilic polymer, a cross-linking agent, a hydrophobic polymer, and a light absorbing agent, wherein the hydrophobic polymer phase is dispersed in a hydrophilic polymer phase. (2) The lithographic printing plate precursor having a layer, wherein (2) the hydrophilic polymer has one or more functional groups selected from an amide group, a carboxyl group, a hydroxyl group, and a sulfonic acid group in a side chain. (3) The above-mentioned (1) or (1), wherein the hydrophobic polymer is a polymer obtained mainly by an unsaturated monomer selected from an aromatic unsaturated monomer and an unsaturated nitrile monomer and obtained by emulsion polymerization. (2) The lithographic printing plate precursor according to (2), (4) the lithographic printing plate precursor according to (3), wherein the hydrophobic polymer is a polymer having a functional group that reacts with the functional group of the hydrophilic polymer. Polymer Wherein the functional group that reacts with the hydrophilic polymer is a glycidyl group;
(5) the lithographic printing plate precursor according to the above (5), wherein the glass transition temperature of the hydrophobic polymer is 60 ° C. or higher; (7) the photosensitive layer is 92 to 50% by mass of the hydrophilic polymer, 3 to 35% by mass of the crosslinking agent;
The above (1) to (1) to (1) to (5), which contain 5 to 35% by mass of a hydrophobic polymer, and further contain 2 to 20 parts by mass of a light absorber with respect to 100 parts by mass of the total of the hydrophilic polymer, the crosslinking agent, and the hydrophobic polymer. 6) An original plate for lithographic printing according to any one of
(8) The lithographic printing plate precursor according to any one of (1) to (7), wherein the light absorbing agent has a light absorbing ability in a wavelength range of 750 to 1100 nm, (9). A lithographic printing plate in which the lithographic printing original plate according to any of the above is irradiated with light to change the hydrophilicity of the photosensitive layer to ink-philicity, (10) the irradiation light has a wavelength of 750 to 1100 nm. (11) a hydrophilic polymer in an amount of 92 to 50% by mass, a crosslinking agent in an amount of 3 to 35% by mass,
A photosensitive composition containing 5 to 35% by mass of a hydrophobic polymer, and 2 to 20 parts by mass of a light absorber with respect to a total of 100 parts by mass of the hydrophilic polymer, the crosslinking agent, and the hydrophobic polymer;
(12) The photosensitive composition according to (11), wherein the hydrophilic polymer has one or more functional groups selected from an amide group, a carboxyl group, a hydroxyl group, and a sulfonic acid group in a side chain. (14) The photosensitive composition according to the above (11) or (12), wherein the polymer is a polymer mainly containing an unsaturated monomer selected from an aromatic unsaturated monomer and an unsaturated nitrile monomer, and obtained by emulsion polymerization. The photosensitive composition according to (13), wherein the hydrophobic polymer is a polymer having a functional group that reacts with the functional group of the hydrophilic polymer. (15) The photosensitive composition according to the above (14), wherein the functional group which reacts with the functional group of the hydrophilic polymer in the hydrophobic polymer is a glycidyl group, and (16) the light absorber has a wavelength of 750 to 1100 nm. The photosensitive composition according to any one of the above (11) to (15), which has a light absorbing ability.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The lithographic printing plate precursor of the present invention comprises a substrate containing a hydrophilic polymer, a cross-linking agent, a hydrophobic polymer, and a light absorbing agent, wherein the hydrophobic polymer phase is a hydrophilic polymer. A hydrophilic photosensitive layer dispersed in a phase consisting of the following, wherein the photosensitive layer loses hydrophilicity and changes to ink-philic by irradiation with light.

Specific examples of the substrate used for the lithographic printing plate precursor of the present invention include metal plates such as aluminum plate, steel plate, stainless plate and copper plate, and plastic films such as polyester, nylon, polyethylene, polypropylene, polycarbonate and ABS resin. And paper, aluminum foil laminated paper,
Metal-deposited paper, plastic film laminated paper, etc. The thickness of these substrates is not particularly limited, but is usually about 100 to 400 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.

Next, the photosensitive layer of the present invention will be described in detail. The lithographic printing plate of the present invention is a plate for offset printing using dampening water. Therefore, when printing the photosensitive layer of the present invention, the unexposed portions repel the ink due to the adhesion of water. Therefore, the photosensitive layer is required to be hydrophilic. The property that water adheres and repels ink is basically required only on the surface of the layer, but when the layer is composed of a hydrophilic polymer, the hydrophilic polymer absorbs water and repels ink. Become like On the other hand, the printing plate also needs to have printing durability and is hydrophilic enough to absorb water, but is also required to be insoluble in water (water resistance). Further, the photosensitive layer of the present invention absorbs light irradiated to form an image and generates heat. Due to the generated heat, the plate of the present invention can be used without performing operations such as development and wiping after exposure, and without completely removing the photosensitive layer of the light-irradiated portion by ablation. Loses hydrophilicity and changes to ink-philic. To realize the various characteristics as described above, the photosensitive layer of the present invention, a hydrophilic polymer, a cross-linking agent, a hydrophobic polymer, and a photosensitive composition containing a light absorber, applied to a substrate, Preferably, it is crosslinked, and in the photosensitive layer, a hydrophobic polymer phase is dispersed in a crosslinked hydrophilic polymer phase. The hydrophilic polymer becomes insoluble (water resistant) in water by being crosslinked by a crosslinking agent. or,
By dispersing the hydrophobic polymer in the photosensitive layer,
Not only the water resistance of the photosensitive layer is improved, but also the hydrophobic polymer is melted by the heat at the time of exposure, and the hydrophobic polymer is migrated to the surface of the photosensitive layer, or the functional group of the hydrophilic polymer and the hydrophobic polymer are combined. When the functional group reacts, the hydrophilicity of the photosensitive layer in the exposed area is lost, and the photosensitive layer is converted to ink-philic property.

The hydrophilic polymer used in the photosensitive layer according to the present invention has a hydrophilic group and a functional group which reacts with a crosslinking agent, and the hydrophilic group is decomposed by heat generated by irradiation with light. And those in which the hydrophilic group loses hydrophilicity by reacting with the functional group in the hydrophobic polymer. When the hydrophilic group is decomposed or reacted, the hydrophilicity is lost and the ink becomes lipophilic. Specific examples of the hydrophilic polymer include one or two or more functional groups selected from amide groups, carboxyl groups, hydroxyl groups, and sulfonic acid groups on the side chains of saponified polyvinyl acetate, celluloses, gelatin, and the like. Among these, amide groups, carboxyl groups, and the like in the above-mentioned side chains because of ease of cross-linking, ease of balancing hydrophilicity and water resistance, ease of ink affinity by light irradiation, and the like. And polymers having one or more kinds of hydroxyl groups and sulfonic acid groups, more specifically, polymers obtained by polymerizing the above-mentioned unsaturated monomers having an amide group, a carboxyl group, a hydroxyl group, and a sulfonic acid group. And modified polymers of this polymer. In these polymers, the carboxyl group or sulfonic acid group may be completely or partially neutralized with a basic compound such as an alkali metal hydroxide or an amine.

Specific examples of the unsaturated monomer having a functional group in the side chain include unsaturated monomers having an amide group include unsubstituted or substituted (meth) acrylamide,
Examples include unsubstituted or substituted itaconic amides, unsubstituted or substituted fumaric amides, unsubstituted or substituted maleic amides, and the like. Unsubstituted or substituted maleic imides are also included in the unsaturated monomer having an amide group of the present invention. 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 monomers such as acrylamide, propyl sulfonate (meth) acrylamide, (meth) acryloylmorpholine, N-vinylacetamide, N-
Vinylformamide, N-vinylpyrrolidone, and the like. Further, in the case of dibasic amides such as itaconic amide, fumaric amide and maleic amide, one or both of the carboxyl groups may be amidated.
When one is amidated, the other carboxyl group may be esterified. Further, the amide group may be substituted with an alkyl group or the like.

Examples of the unsaturated monomer having a hydroxyl group include:
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, methylol (meth) acrylamide, and methoxymethyl (meth), which is a condensate of methylol (meth) acrylamide with methyl alcohol or butyl alcohol ) Acrylamide, butoxymethyl (meth)
Examples of unsaturated monomers having a carboxyl group such as acrylamide include monobasic unsaturated acids such as (meth) acrylic acid, dibasic unsaturated acids such as itaconic acid, fumaric acid, maleic acid and anhydrides thereof, and dibasic unsaturated acids such as these. Monoesters and monoamides of unsaturated acids, and unsaturated monomers having a sulfonic acid group include propyl (meth) acrylamide sulfonate. The carboxyl group or sulfonic group in these unsaturated monomers may be neutralized with an inorganic base such as sodium hydroxide or potassium hydroxide or amines. One or more of the above unsaturated monomers may be used.

In the polymerization, a monomer copolymerizable with these unsaturated monomers may be used in combination. Examples of copolymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate.
Acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, Adamantyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, vinyl acetate and the like can be mentioned. In the above description, (meth) acrylamide and (meth) acrylic acid in (meth) acrylic acid and the like, (meth) acrylic acid, (meth) acryloyl, and further (meth) acrylate and the like are acrylic and methacrylic, acryloyl and methacryloyl, and acrylate. It means both methacrylate.

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,
Known polyhydric alcohol compounds, polycarboxylic acid compounds and anhydrides thereof, which react with a carboxyl group, a sulfonic acid group, a hydroxyl group and, in some cases, an amide group, which are crosslinkable functional groups in the hydrophilic polymer, polyhydric glycidyl Compounds, polyamines, polyisocyanate compounds, epoxy resins,
Oxazoline resins, amino resins and the like. In the present invention, among the above crosslinking agents, various epoxy resins known from the balance between the curing speed and the stability of the photosensitive composition and the balance between hydrophilicity and water resistance of the photosensitive layer, known oxazoline resins, known Amino resins are 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. In order to accelerate the crosslinking reaction, tertiary amines are used when the above-mentioned epoxy resin is used, and acidic compounds such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, and ammonium chloride are used together when the amino resin is used. You may.

In the photosensitive layer, the hydrophobic polymer used in the present invention is preferably a polymer dispersed in a phase composed of the hydrophilic polymer, and a polymer not compatible with the hydrophilic polymer is preferred. From this point, specifically, a polymer mainly containing a monomer selected from an aromatic unsaturated monomer and unsaturated nitrile is preferable.

Further, when the photosensitive layer is irradiated with light, it is required that the irradiated portion loses the hydrophilicity of the irradiated portion and changes to an ink-affinity property. The hydrophilic polymer preferably has a functional group that reacts with the functional group of the hydrophilic polymer, and the functional group is preferably a glycidyl group, and the unsaturated monomer having a glycidyl group is replaced with an aromatic unsaturated monomer or unsaturated nitrile. May be copolymerized.

Examples of the aromatic unsaturated monomer used as a main component in the polymerization of the hydrophobic polymer include styrene, α-methylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylnaphthalene, divinylbenzene and the like. Examples of the unsaturated nitrile include acrylonitrile and methacrylonitrile, and examples of the unsaturated monomer having a glycidyl group include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, paravinylphenyl glycidyl ether, and paraisopropenylphenyl glycidyl ether. No.

In synthesizing the hydrophobic polymer, the unsaturated monomer which can be copolymerized with the above-mentioned aromatic unsaturated monomer, unsaturated nitrile or unsaturated monomer having a glycidyl group is used as long as the effects of the present invention are not impaired. It may be copolymerized. Examples of the copolymerizable unsaturated monomer include unsaturated monomers used in the hydrophilic polymer.

In the photosensitive layer of the present invention, the hydrophobic polymer is dispersed in a layer composed of a hydrophilic polymer.
It is about 0.05 to 1 μm, preferably about 0.1 to 0.5 μm. In view of the fact that a hydrophobic polymer having such a particle size can be stably and easily controlled in the photosensitive layer, the hydrophobic polymer is obtained by emulsion polymerization of the above-mentioned monomer containing an aromatic unsaturated monomer as a main component. The glass transition temperature of the hydrophobic polymer is preferably 60 ° C. or higher from the viewpoint of the dispersion stability of the polymer at the time of heating for crosslinking of the photosensitive layer. The emulsion polymerization method of the above-mentioned hydrophobic polymer is not particularly limited, and examples thereof include a method using a normal surfactant, a so-called soap-free polymerization method, and a protective colloid polymerization method using polyvinyl alcohol, acrylamide, or the like. In particular, from the relation with the stability to the hydrophilic polymer phase, a protective colloid polymerization method that can stabilize the emulsion particles by covering the surface of the emulsion particles with the polymer using polyvinyl alcohol or acrylamide is preferable.

The light absorbing agent used in the photosensitive layer of the present invention may be any as long as it absorbs light and generates heat, and there is no particular limitation on the wavelength of the light to be absorbed. Light in the wavelength range to be absorbed may be used as appropriate.
Specific examples of the light absorber include cyanine dyes, polymethine dyes, phthalocyanine dyes, naphthalocyanine dyes, anthocyanin dyes, porphyrin dyes,
Examples include azo dyes, benzoquinone dyes, naphthoquinone dyes, dithiol metal complexes, metal complexes of diamines, nigrosine, and carbon black. These light absorbers are 750 to 1100 n in terms of handleability in a bright room, output of a light source used in an exposure machine, and ease of use.
Light absorbers that absorb light in the region of m are preferred. The absorption wavelength range of the light absorber can be changed depending on the substituent, the length of the conjugated system of π electrons, and the like. These light absorbers may be dissolved or dispersed in the photosensitive composition or the photosensitive layer.

The photosensitive layer of the present invention preferably contains a hydrophilic polymer, a cross-linking agent, a hydrophobic polymer and a light absorbing agent, and the proportion thereof is a balance between hydrophilicity and water resistance of the photosensitive layer and sensitivity at the time of exposure. From the viewpoint of resolution, easiness of making ink-friendly, and various printing characteristics (ink-adhesion property of exposed portion, stain resistance of non-exposed portion, printing durability), hydrophilic polymer 9 in solid content
2 to 50% by mass, 3 to 35% by mass of a crosslinking agent, 5 to 35% by mass of a hydrophobic polymer, and 2 to 2 parts of a light absorber based on 100 parts by mass of the total of the hydrophilic polymer, the crosslinking agent and the hydrophobic polymer.
0 parts by mass is preferred. When the cross-linking agent is 3% by mass or more, the water resistance of the plate does not decrease, and the printing durability is sufficient.
The above is more preferred. On the other hand, when the amount of the cross-linking agent is 35% by mass or less, the hydrophilicity of the plate is not reduced, and the background is not stained. If the hydrophobic polymer is at least 5 parts by mass, the ink will be sufficiently ink-friendly when the plate is irradiated with light, and the ink-filling property will be sufficient. On the other hand, when the hydrophobic polymer is 35
It is preferable that the amount is not more than part by mass because the hydrophilicity of the plate does not decrease. Further, when the amount of the light absorber is 2 parts by mass or more, the sensitivity of the plate is not reduced, and preferably 4 parts by mass or more.
When the amount of the light absorber is 20 parts by mass or less, ablation does not occur violently, decomposition products do not scatter, and it is preferable from the viewpoint of economy and the like.

The photosensitive layer of the present invention may be prepared by applying a liquid comprising a photosensitive composition containing a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer and a light absorbing agent to a substrate, followed by drying and curing.
The method of application varies depending on the viscosity of the solution of the photosensitive composition 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, a filler can be added to the photosensitive composition to improve various characteristics of the photosensitive layer. The filler used may be organic or inorganic.

After applying the coating composition comprising the photosensitive composition, the composition is heated and dried, and the hydrophilic polymer is crosslinked.
To cure. The heating temperature is usually about 50 to 200 ° C.
The thickness of the photosensitive layer is not particularly limited, but is usually 0.5 to 10 μm.
m is preferable.

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

When the printing plate of the present invention is exposed to light in the absorption wavelength range of the light absorbing agent, for example, light in the range of 750 to 1100 nm, the light absorbing agent absorbs the light and generates heat. Due to this heat generation, the hydrophilic functional groups of the hydrophilic polymer constituting the photosensitive layer are partially decomposed, the hydrophobic polymer phase dispersed in the hydrophilic polymer phase migrates to the photosensitive layer surface, or The hydrophilic functional groups such as amide groups, carboxylic acid groups, and sulfonic acid groups in the polymer react with glycidyl groups in the hydrophobic polymer and the like, and the light-exposed portion of the photosensitive layer loses hydrophilicity and becomes ink-friendly. I do. Due to this exposure, the photosensitive layer in the exposed area may lose its mass or may foam due to the generation of gas. 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 from the unexposed area due to foaming, the printing may start to reduce or eliminate the protrusion due to the printing pressure.

In the present invention, the photosensitive layer becomes ink-philic by exposure to light, but the hydrophilic functional groups of the hydrophilic polymer are eliminated, and the elimination promotes the crosslinking to further promote the hydrophilicity. Or the hydrophilic functional group reacts with the functional group in the hydrophobic polymer to lose hydrophilicity, or the hydrophobic polymer migrates to the surface of the photosensitive layer to form an ink-friendly ink. To be estimated. Of course, the light absorbing agent and the crosslinking agent may be decomposed by heat. However, if the irradiation light amount at the time of exposure is too large, most of the photosensitive layer may be removed or ablated by decomposition, combustion, or the like, but such a problem must be avoided in the present invention.

As described above, in the printing original plate of the present invention, the hydrophilicity of the photosensitive layer in the light-irradiated portion changes its characteristics to ink-philicity, and the ink-irradiated portion can be exposed without developing or wiping. Adheres and printing becomes possible.

The wavelength of light used for exposing the printing original plate of the present invention is not particularly limited, and light that matches the absorption wavelength range of the light absorbing agent may be used. At the time of exposure, it is preferable to scan convergent light at high speed from the viewpoint of exposure speed, and a light source that is easy to use and has high output is suitable. The light to be exposed from this point is preferably a laser beam, particularly a laser beam having an oscillation wavelength in the wavelength range of 750 to 1100 nm, for example, 8
30nm high power semiconductor laser or 1064nm YA
G lasers are used, and exposure machines equipped with these lasers are already on the market as so-called thermal platesetters (exposure machines).

[0038]

Embodiments of the present invention will be described below. [Examples 1 to 6, Comparative Examples 1 and 2] (Synthesis of hydrophilic polymer) 400 g of water in a 1000 cc flask
After removing dissolved oxygen by bubbling nitrogen,
Heat to 80 ° C. While flowing nitrogen gas into the flask, a monomer solution consisting of 78 g of acrylamide, 30 g of acrylic acid, 12 g of hydroxyethyl acrylate and 77 g of water and V-
50 (water-soluble azo initiator manufactured by Wako Pure Chemical Industries, Ltd.) 0.5 g
Was dissolved in 50 g of water, and the aqueous solution of the initiator was continuously dropped over 3 hours while maintaining the internal temperature at 75 ° C. and constantly maintaining the pH in the flask at 8 to 9 with triethylamine. After completion of dropping, polymerization was continued at 80 ° C for 2 hours, and then 90 ° C
, And finally 150 g of water was added to synthesize an aqueous solution of a hydrophilic polymer. An aqueous solution of this polymer has a viscosity
38000 mPa · s, the solid content was 15% by weight. (Synthesis of hydrophobic polymer) 350cc water in 1000cc flask
, And Perex SSL (surfactant made by Kao) 0.5g, heat up to 72 ℃ while flowing nitrogen, 2.5g potassium persulfate
After 10 minutes, 1.5 g of acrylamide, 0.5 g of hydroxyethyl acrylate, 0.3 g of styrene and 0.2 g of glycidyl acrylate were added, and polymerization was carried out at 72 ° C. for 20 minutes. Thereafter, a monomer solution consisting of 325 g of styrene, 75 g of glycidyl acrylate, 80 g of cyclohexyl acrylate, and 20 g of acrylamide was previously emulsion-polymerized while continuously dropping a solution of 175 g of water and 2 g of Perex SSL at 72 ° C. over 4 hours. After dropping of monomer dispersion
Polymerization was further performed at 75 ° C. for 3 hours to obtain an emulsion of a hydrophobic polymer. The solid content of the obtained polymer emulsion was 50%, and the particle size was 0.25 μm. The glass transition temperature of the polymer was 67 ° C. (Photosensitive composition) Next, the above hydrophilic polymer and Cymel 350 (a methylated melamine resin manufactured by Mitsui Cytec Co., Ltd.) as a crosslinking agent, and the above hydrophobic polymer are shown in Table 1 [Table 1] in solid content. Parts by weight and IR as a light absorber
A photosensitive composition was prepared by mixing 5 parts by weight of -125 (a cyanine dye manufactured by Nippon Senseki Dye Co., Ltd.).

[0039]

[Table 1]

(Preparation of printing plate) The above photosensitive composition was applied to a 0.2 μm polyester film using a doctor blade, and then dried at 120 ° C. for 1 hour to form a 2 μm thick photosensitive layer. A printing original plate 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. Sensitivity is approximately 270 for all versions
mJ / cm ² . When the cross section of this plate was observed with a microscope, the photosensitive layer of the exposed portion was foamed and raised in all of the plates of Examples and Comparative Examples.

The exposed plate was set on an offset printing machine using dampening water and printing was performed. In the printing plates of Examples 1 to 6, no ink was attached 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). ). Also, the resolution and printing durability were excellent. On the other hand, the printing plates of Comparative Examples 1 and 3 were poor in the inking property of the ink in the light-exposed area, and the printing plates of Comparative Example 2 were not well printed because the ink was adhered to the unexposed area (background smear).
The plate of Comparative Example 4 had poor water resistance, and the photosensitive layer was peeled off at the same time as the start of printing. It should be noted that there was no problem at all when the plates were handled in a normal light room.

[Examples 7 to 12 and Comparative Examples 3 to 5] In the synthesis of the hydrophilic polymer of Example 1, the unsaturated monomers shown in Table 2 [Table 2] were used, and the synthesis of the hydrophobic polymer was carried out. In Example 3, a hydrophilic polymer and a hydrophobic polymer were synthesized in the same manner as in Example 1 except that the unsaturated monomers shown in Table 3 [Table 3] were used. A photosensitive composition was prepared according to the same formulation as in the photosensitive composition of Example 1 except that the photosensitive polymer was used. The glass transition temperature of the synthesized hydrophobic polymer was (a) 84 ° C.
(B) 63 ° C, (c) 74 ° C, (d) 52 ° C,
(E) was 82 ° C.

Next, a 2 μm-thick butyral resin was applied as a primer in advance to improve the adhesiveness.
The photosensitive composition shown in Table 4 was applied to an aluminum plate having a thickness of 3 mm and dried at 160 ° C. for 15 minutes to prepare a printing plate having a photosensitive layer having a thickness of 3 μm. Using this plate, exposure was performed in the same manner as in Example 1, and printing evaluation was performed. The printing evaluation results showed that all of the plates of Examples 7 to 12 were excellent in printability and printing durability. On the other hand, in all of the plates of Comparative Examples 3 to 5, ink adhered to the unexposed portions (ground stain), and clear printing was not possible. In addition, there was no problem in handling any of the plates in a normal light room.

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

Examples 13 to 15 In the photosensitive composition of Example 1, Cymel 701 (manufactured by Mitsui Cytec Co., Ltd.) was used as a crosslinking agent, and a light absorbing agent of the type shown in Table 5 was used. Using a light absorber and an amount, first a hydrophilic polymer,
After mixing the crosslinking agent and the light absorbing agent, the light absorbing agent was dispersed in a liquid composed of the hydrophilic polymer and the crosslinking agent over 5 hours by a ball mill. Next, a photosensitive polymer composition was prepared by adding an emulsion of a hydrophobic polymer. Next, a printing original plate was prepared using the photosensitive composition in the same manner as in Example 7,
Exposure and printing were evaluated. The sensitivity is 240, 170,
It was 200 mJ / cm2. Further, the printing evaluation results showed that all the plates were excellent in printability and printing durability.

[0049]

[Table 5]

[0050]

According to the present invention, a lithographic printing plate precursor using a fountain solution contains a hydrophilic polymer, a cross-linking agent, a hydrophobic polymer, and a light absorber, and the hydrophobic polymer phase is composed of the hydrophilic polymer. By using a photosensitive layer dispersed in a phase, the hydrophilicity of the photosensitive layer changes to ink-philic by exposure to light, so that steps such as development and wiping are not required, and the hydrophilicity and water resistance are excellent. The present invention provides a printing plate having excellent characteristics such as no background staining, good sensitivity, resolution and printing durability.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Mase 580-32, Takuji Nagaura, Sodegaura-shi, Chiba 580-32 Inside Mitsui Chemicals, Inc. (72) Sumio Hirose 580 Takuji Nagaura, Sodegaura-shi, Chiba 580 No. 32 Mitsui Chemicals F-term (reference) 2H096 AA07 AA08 BA16 BA20 EA04 2H114 AA04 AA23 AA24 BA01 BA10 DA03 DA34 DA43 DA44 DA48 DA50 DA53 DA64 EA01 EA02 EA03 FA08 FA10

Claims (16)

[Claims] 1. A lithographic plate having a photosensitive layer comprising a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer, and a light absorber on a substrate, wherein a hydrophobic polymer phase is dispersed in a hydrophilic polymer phase. Original version for printing. 2. The lithographic printing plate precursor according to claim 1, wherein the hydrophilic polymer has one or more functional groups selected from an amide group, a carboxyl group, a hydroxyl group and a sulfonic acid group in a side chain. 3. The lithographic printing method according to claim 1, wherein the hydrophobic polymer is a polymer containing an unsaturated monomer selected from an aromatic unsaturated monomer and an unsaturated nitrile monomer as a main component and obtained by emulsion polymerization. Original version of. 4. The lithographic printing plate precursor according to claim 3, wherein the hydrophobic polymer is a polymer having a functional group that reacts with the functional group in the hydrophilic polymer. 5. The lithographic printing plate precursor according to claim 4, wherein in the hydrophobic polymer, the functional group that reacts with the functional group of the hydrophilic polymer is a glycidyl group. 6. The glass transition temperature of the hydrophobic polymer is 60 ° C.
The original plate for lithographic printing according to claim 5, which is as described above. 7. The photosensitive layer contains 92 to 50% by weight of a hydrophilic polymer, 3 to 35% by weight of a crosslinking agent, and 5 to 35% of a hydrophobic polymer.
% Of the light absorbing agent based on 100 parts by mass of the total of the hydrophilic polymer, the crosslinking agent and the hydrophobic polymer.
The lithographic printing plate precursor according to any one of claims 1 to 6, comprising 0 parts by mass. 8. The lithographic printing plate precursor according to claim 1, wherein the light absorbing agent has a light absorbing ability in a wavelength range of 750 to 1100 nm. 9. A planographic printing plate in which the lithographic printing original plate according to claim 1 is irradiated with light to change the hydrophilicity of the photosensitive layer to ink-philicity. 10. The planographic printing plate according to claim 9, wherein the irradiation light has a wavelength of 750 to 1100 nm. 11. A polymer comprising 92 to 50% by weight of a hydrophilic polymer, 3 to 35% by weight of a crosslinking agent, 5 to 35% by weight of a hydrophobic polymer,
And a photosensitive composition containing 2 to 20 parts by mass of a light absorber based on 100 parts by mass of the total of the hydrophilic polymer, the crosslinking agent, and the hydrophobic polymer. 12. The photosensitive composition according to claim 11, wherein the hydrophilic polymer has one or more functional groups selected from an amide group, a carboxyl group, a hydroxyl group, and a sulfonic acid group in a side chain. 13. The photosensitive composition according to claim 11, wherein the hydrophobic polymer is a polymer containing an unsaturated monomer selected from an aromatic unsaturated monomer and an unsaturated nitrile monomer as a main component and obtained by emulsion polymerization. object. 14. The photosensitive composition according to claim 13, wherein the hydrophobic polymer is a polymer having a functional group that reacts with the functional group of the hydrophilic polymer. 15. The photosensitive composition according to claim 14, wherein in the hydrophobic polymer, a functional group that reacts with a functional group of the hydrophilic polymer is a glycidyl group. 16. The light absorbing agent has a wavelength of 750 to 1100 nm.
16. A region having a light absorbing ability in the region of
The photosensitive composition according to any one of the above.