JPH1062982A - Original plate for photosensitive planographic printing plate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the inspectability of a printing plate by insolubilizing a dye with a color formed by exposure in water by forming a photosensitive hydrophilic swellable layer contg. a leuco dye, a photooxidizing agent and an org. acid salt on a substrate. SOLUTION: This original plate has at least a photosensitive hydrophilic swellable layer contg. a leuco dye, a photooxidizing agent and an org. acid salt on the substrate and it is allowed to form a color at the time of exposure. The photooxidizing agent is inert until it is exposed to active radiant light and the agent generates a chemical seed oxidizing the leuco dye to a color forming dye when exposed. The org. acid salt is used for insolubilizing a water- soluble dye with a formed color in water or reducing the water solubility of the dye. An anionic surfactant such as a fatty acid salt or abietate is preferably used as the org. acid salt. A polyacrylic acid copolymer may be used in combination with the anionic surfactant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the practical characteristics of a novel photosensitive lithographic printing plate, and more particularly to a photosensitive lithographic printing plate precursor excellent in plate inspection properties and a method for making the same.

[0002]

2. Description of the Related Art In lithographic printing, an image area and a non-image area are basically present on substantially the same plane, and the image area is made ink-receptive and the non-image area is made ink-repellent. Utilizing the difference in adhesiveness, after inking ink only on the image area,
This refers to a method of printing by transferring ink onto a printing medium such as paper. A PS plate is usually used for such lithographic printing.

[0003] The PS plate mentioned here means the following.

[0004] That is, Teruhiko Yonezawa, "PS Version Overview"
As described in pp. 18-81 of the Printing Society of Japan (1993), a lipophilic photosensitive resin layer is applied on an aluminum substrate that has been subjected to hydrophilic treatment, and the image portion is formed by photolithography. The photosensitive layer remains, while the non-image area is a PS plate with water where the surface of the aluminum substrate is exposed and a dampening water layer is formed on the surface to repel ink.

In the PS plate, an original image of a positive or negative film is usually superimposed on a printing plate and irradiated with active light (this step is called an exposure step). As a result, an exposed portion and an unexposed portion can be obtained. However, in order to easily determine the presence or absence of the exposure step, it is devised that the dye can be identified by coloring or fading of the dye. For example, JP-A-60-57340 proposes a photosensitive layer containing a leuco dye as a dye precursor and a photooxidant. In this method, the dye was developed by exposure, so that the printing property was excellent. However, since the formed leuco dye is water-soluble, a developing solution containing water as a main component, a developing step using water, a washing step, and furthermore, the dye is dissolved from the printing plate into the dampening water so that the exposed part and the unexposed part are exposed. It is difficult to determine whether the original is reproduced and it is difficult to confirm whether or not the original is reproduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object to provide a photosensitive lithographic printing method comprising a leuco dye, a photooxidant and an organic acid salt. It is an object of the present invention to obtain a photosensitive lithographic printing plate in which a plate precursor is colored by exposing a dye precursor to light to improve plate inspection.

[0007]

In order to solve the above-mentioned problems, the present invention has the following arrangement.

(1) A lithographic printing plate having at least a photosensitive hydrophilic swelling layer on a substrate, wherein the hydrophilic swelling layer contains a leuco dye, a photooxidant, and an organic acid salt. Genographic printing plate precursor.

(2) In a photosensitive lithographic printing plate comprising at least a hydrophilic swelling layer and a photosensitive layer laminated on a substrate,
A photosensitive lithographic printing plate precursor characterized in that the photosensitive layer contains a leuco dye, a photooxidant, and an organic acid salt.

(3) A method for making a photosensitive lithographic printing plate, characterized in that the photosensitive lithographic printing plate precursor according to (1) or (2) is colored when exposed.

(4) The method of making a photosensitive lithographic printing plate as described in (3), wherein the image area is colored.

(5) The photosensitive lithographic printing plate precursor as described in (1) or (2), wherein the organic acid salt is an anionic surfactant.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A photosensitive lithographic printing plate precursor according to the present invention having at least a photosensitive hydrophilic swelling layer on a substrate will be described.

The non-image area of the lithographic printing plate of the present invention is characterized in that it comprises a hydrophilic swelling layer.

The hydrophilic swelling layer will be described.

The term "hydrophilic" as used in the present invention means a property of being substantially insoluble in water and exhibiting water swelling property. A known hydrophilic polymer is laminated on a substrate by coating or transfer, and the like. A hydrophilic swelling layer which is cross-linked or pseudo-cross-linked using the above method and is partially water-soluble or insoluble in water to make it water-swellable is used.

The hydrophilic polymer mentioned here means a known water-soluble polymer (meaning one that is completely soluble in water), a pseudo-water-soluble polymer (meaning amphiphilicity, macro-soluble but macro-soluble Means water-swellable polymer (means that swells in water but does not dissolve). That is, it refers to a polymer that adsorbs or absorbs water under normal use conditions, and a polymer that dissolves in or swells in water.

In the present invention, known polymers can be used as the hydrophilic polymer, and include animal polymers, plant polymers, and synthetic polymers. For example, "Function
alMonomers "(by Y. Nyquist, De.
kker), "Water-soluble polymer" (by Nakamura, Chemical Industry Co., Ltd.), "Latest processing / modification technology and application development of water-soluble polymer water-dispersed resin, Comprehensive technical materials" (Management Development Center Publishing Division), Examples include hydrophilic polymers described in "Applications and Markets of New Water-Soluble Polymers" (CMC).
Specific examples are described below.

(A) Natural polymers: starch-acrylonitrile-based graft polymer hydrolyzate, starch-acrylic acid-based graft polymer, starch-styrene sulfonic acid-based graft polymer, starch-
Vinyl sulfonic acid type graft polymer, starch-acrylamide type graft polymer, carboxylated methyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, xanthate cellulose, cellulose-acrylonitrile type graft polymer, cellulose-styrene sulfonic acid type graft polymer , A carboxymethylcellulose-based crosslinked product,
Hyaluronic acid, agarose, collagen, milk casein, acid casein, rennet casein, ammonia casein, potashized casein, borax casein, glue, gelatin, gluten, soy protein, alginate, ammonium alginate, potassium alginate, sodium alginate, arabic gum , Tragacanth gum, karaya gum,
Guar gum, locust bean gum, Irish moss, soy lecithin, pectic acid, starch, carboxylated starch, agar, dextrin, mannan, etc.

(B) Synthetic polymers polyvinyl alcohol, polyethylene oxide, poly (ethylene oxide-co-propylene oxide), aqueous urethane resin, water-soluble polyester, ammonium polyacrylate, sodium polyacrylate, polyammonium methacrylate, Acrylic copolymer, acrylic emulsion copolymer, polyvinyl alcohol-based crosslinked polymer, sodium polyacrylate-based crosslinked product, saponified polyacrylonitrile-based polymer, hydroxyethyl (meth) acrylate-based polymer ((meth) □ in the following description) □
□□ stands for □□□□ or meta □□□□. ), Poly (vinyl methyl ether-co-maleic anhydride), maleic anhydride copolymer, vinylpyrrolidone copolymer, polyethylene glycol di (meth)
Acrylate-based crosslinked polymers, polypropylene glycol di (meth) acrylate-based crosslinked polymers and the like.

The above hydrophilic compound may contain monomers or copolymer components having different substituents for the purpose of imparting flexibility or controlling hydrophilicity, as long as the effects of the present invention are not changed. is there.

Next, a method for crosslinking a hydrophilic polymer will be described.

The hydrophilic swelling layer is formed by crosslinking or pseudo-crosslinking at least one of the above hydrophilic polymers as necessary.
A layer is formed on a substrate by being partially soluble in water or insolubilized in water. Usually, the cross-linking reaction is performed by performing a three-dimensional cross-linking reaction using a reactive functional group of the hydrophilic polymer.

The cross-linking reaction may be covalent cross-linking or ionic cross-linking.

Examples of the compound used for the crosslinking reaction include known polyfunctional compounds having crosslinking properties, such as polyepoxy compounds, polyisocyanate compounds, poly (meth) acrylic compounds, polymercapto compounds, polyalkoxysilyl compounds, Examples include a polyvalent metal salt compound, a polyamine compound, an aldehyde compound, and a polyvinyl compound. The crosslinking reaction is carried out by adding a known catalyst to accelerate the reaction.

These hydrophilic polymers can be used alone or as a mixture of two or more kinds for the purpose of maintaining the form of the hydrophilic swelling layer and adjusting the water swelling property, and blending the non-hydrophilic polymer. It is also possible.

In the hydrophilic swelling layer used in the present invention, trace amounts of various additives such as dyes and pigments, surfactants and organic acids can be added.

The printing plate precursor of the present invention contains a leuco dye. As the leuco dye, known leuco dyes can be used, and the following are used.

Leucocrustal violet, leuco opal blue, leucomalachite green, leucorosaniline, leucobararosalin, p, p ', p "-trimethylleucoopal blue, p, p', p" -trichloroleucoopal blue, leukotriallylmethane compounds such as p, p'-bis-tetramethyl-diaminodiphenylmethane, 3,6-bis (dimethylamino)-
Various leukoxanthene dyes such as 9- (p-dimethylaminophenyl) xanthene and leukothioxanthene dyes such as 3,6-bis (dimethylamino) -9- (p-dimethylaminophenyl) thioxanthene Used, but can be selected according to various colors. Further, two or more kinds may be used in combination.

The content of the leuco dye in the hydrophilic swelling layer is 0.1 to 50% by weight, preferably 0.1 to 50% by weight.
３０30% by weight.

The photooxidant used in the present invention is inactive until it is exposed to active radiation such as visible light, ultraviolet light, infrared light, X-rays, etc. Produces a species that oxidizes to a colored form. As the photo-oxidizing agent, known ones can be used, and the following ones are used. Triarylimidazolyl dimer, carbon tetrabromide, N-bromosuccinimide, halogenated hydrocarbons such as tribromomethylphenylsulfone, azide compounds such as 2-azidobenzoxazole, benzoylazide, 2-azidobenzimidazole And 3-ethyl-1-methoxy-2-pyridothiacyanine perchlorate, 1-methoxy-2-methylpyridinium p-toluenesulfonate.

The above-mentioned photo-oxidizing agents can be used alone or in combination of two or more. In addition, the content of the photooxidant depends on the color development of the leuco dye,
In the case of the most common leuco crystal violet, the content of the leuco dye is 1/4 to 10 times,
Preferably it is 1/2 to 6 times. Further, anthraquinones such as anthraquinone, 2-methylanthraquinone and 2-ethylanthraquinone; benzoin derivatives such as benzoin, benzoin methyl ether and benzoin ethyl ether; thioxanthone derivatives such as chlorothioxanthone, diisopropylthioxanthone and 2,4-diethylthioxanthone; benzophenone It is also possible to improve photochromic properties by coexisting a benzophenone derivative such as 4,4-bis (dimethylamino) benzophenone, an acetophenone derivative such as acetophenone and dimethoxyphenylacetophenone, and a photopolymerization initiator such as benzyl.

The organic acid salt used in the present invention is used for the purpose of insolubilizing a colored water-soluble dye in water or reducing its water solubility.

The following are used as such organic acid salts.

Examples of anionic surfactants include those described in "New surfactant introduction" (Takehiko Fujimoto, Sanyo Chemical Industry Co., Ltd.). Specific examples are described below.

Fatty acid salts, abietic acid salts, hydroxyalkanesulfonic acid salts, alkanesulfonic acid salts,
Dialkyl sulfosuccinates, linear alkyl benzene sulfonates, branched alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl diphenyl ether sulfonates, alkyl phenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts , N-methyl-N-oleyltaurine sodium, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonate, sulfated castor oil, sulfated tallow oil, sulfate salt of fatty acid alkyl ester, alkyl sulfate salt, Polyoxyethylene alkyl ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alkyl phenyl ether sulfates, poly Xyethylene styryl phenyl ether sulfates, polyoxyethylene naphthyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, styrene-maleic anhydride copolymer Partially saponified compounds, partially saponified olefin-maleic anhydride copolymers, and naphthalenesulfonate formalin condensates are exemplified.

In the present invention, a polyacrylic acid-based copolymer can be used together with the above-mentioned anionic surfactant. The polyacrylic acid-based copolymer specifically includes the following polymers. Water-soluble monomers such as methacrylic acid, (anhydride) maleic acid, fumaric acid, itaconic acid, acrylamide, and methacrylamide as monomers to be copolymerized in polyacrylic acid homopolymers and copolymers.
It also contains monomers that are usually insoluble in water, such as acrylic acid esters, methacrylic acid esters, vinyl acetate, and styrene.These monomers can be copolymerized with acrylic acid or copolymerized with acrylic acid esters. By hydrolysis, a water-soluble polyacrylic acid copolymer can be obtained.

Further, the copolymer includes a graft or block type copolymer. For example, when a vinyl acetate / acrylic acid (ester) copolymer is hydrolyzed, a water-soluble vinyl alcohol / acrylic acid copolymer is obtained. The acrylic acid-based copolymer usually contains at least 70% by weight of an acrylic acid monomer component, and a carboxyl group contained in the polymer is partially neutralized as an alkali metal salt, and a preferable degree of neutralization is 30 to 100 mol. %. The acrylic acid-based copolymer is preferably crosslinked by a known method and present as a water-absorbing resin.

In addition, various additives such as a dark reaction inhibitor with a leuco dye and a photooxidant, and a color sensitizer at the time of heating such as a carboxylic acid ester can be added.

In the present invention, the photosensitive layer preferably contains a leuco dye, a photooxidant and an organic acid salt. In order to produce a photosensitive hydrophilic swelling layer containing a leuco dye, a photo-oxidizing agent and an organic acid salt, each component comprising a leuco dye, a photo-oxidizing agent and an organic acid salt comprises one photosensitive hydrophilic swelling layer. A method in which the particles are present in a uniform state is preferable from the viewpoint of color development performance.

Next, an example of a method for producing a lithographic printing plate according to the present invention will be described, but the present invention is not limited thereto.

The image of the lithographic printing plate of the present invention can be formed, for example, by irradiating the plate surface of a photosensitive lithographic printing plate precursor having a hydrophilic swelling layer on a substrate with actinic rays. That is, the difference between the image area and the non-image area is caused by the irradiation of the actinic ray.

Preferably, the lithographic printing plate according to the invention is produced by negative working imaging. That is, the initial elastic modulus of the portion of the hydrophilic swelling layer irradiated with the actinic ray (hereinafter referred to as an unexposed portion) is increased as compared with the portion not irradiated with the actinic ray (hereinafter referred to as an unexposed portion). As a result, an ink-imprinted image portion is formed, and an unexposed portion becomes an ink-repellent non-image portion.

For such image formation, known photosensitive compounds are used.

That is, a known photocrosslinking or photocurable photosensitive compound is contained in the hydrophilic swelling layer of the original plate, and the exposed portion is selectively crosslinked and / or cured to increase the initial elastic modulus. Formation is achieved.

Examples of known photocrosslinkable or photocurable photosensitive compounds include the following specific examples (1) to (6).

(1) Photopolymerizable monomer or oligomer (2) Photodimerizable photosensitive resin composition (3) Composition comprising a combination of a monomer, oligomer or polymer having an epoxy group and a known photoacid generator (4) Composition of monomer, oligomer or polymer having allyl group and / or vinyl group and monomer, oligomer or polymer having mercapto group (5) Composition of diazonium salt compound and hydroxyl group-containing compound (6) Bisazide A photosensitive composition mainly composed of a polyisoprene rubber or a polybutadiene rubber cyclized with a compound, or a cresol novolak resin;

These photosensitive compounds are added to the composition when forming the hydrophilic swelling layer on the substrate and allowed to exist in the layer, or after forming the hydrophilic swelling layer, the photosensitive composition is added to the composition. It is added by using a method of coating on a layer and impregnating the layer.

A known photosensitizer can be added to the hydrophilic swelling layer of the original plate for the purpose of sensitizing these photosensitive compounds.

The substrate of the lithographic printing plate used in the present invention is not limited at all, except that it is required to have a flexibility that can be attached to an ordinary lithographic printing press and a load capable of withstanding a load applied during printing.

Typical examples are aluminum, copper, iron,
And a plastic film such as a polyester film and a polypropylene film, or coated paper and a rubber sheet. Further, the substrate may be a composite of the above materials.

The surface of the substrate may be subjected to various surface treatments such as an electrochemical treatment, an acid-base treatment, and a corona discharge treatment for the purpose of improving plate inspection and adhesion.

It is also possible to form a primer layer on these substrates by applying a coating or the like for the purpose of improving adhesiveness or preventing halation, thereby forming substrates.

Next, the protective layer will be described.

On the surface of the photosensitive hydrophilic swelling layer of the photosensitive lithographic printing plate precursor according to the present invention, a protective layer which can be removed for the purpose of protecting the hydrophilic swelling layer is coated on the hydrophilic swelling layer by coating. It is preferable to form or laminate a protective film.

In order to improve the vacuum adhesion at the time of image exposure, these protective films may be subjected to uneven processing,
It is also preferable to apply a matte treatment on the surface or to apply and laminate a plastic layer containing silica particles on the surface of the protective film.

Next, the method of exposing the photosensitive lithographic printing plate precursor according to the present invention will be described.

The photosensitive lithographic printing plate of the present invention is preferably made into a printing plate through a plate making step for negative working.
That is, the image is exposed through a negative original film by a normal exposure light source.

As a light source used in this exposure step,
For example, a high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a fluorescent lamp and the like can be mentioned.

Next, a method for making a photosensitive lithographic printing plate according to the present invention will be described.

In the plate making process, when the protective layer is a laminated film as described in the above example, the removal is easily performed by a mechanical means such as a film peeling device or a manual means of manual peeling. In this developing step, when rinsing with water or a developing solution, the photosensitive compound and leuco dye present in and / or outside the hydrophilic swelling layer in the unexposed area are dissolved and removed or desensitized, and the ink is repelled. A non-image area having a suitable dispersion structure and water swelling property is obtained, and the exposed area is an image area having a reduced water swelling property as compared with an unexposed area due to photocrosslinking and curing of the photosensitive compound.

Next, a printing method using a lithographic printing plate obtained from the photosensitive lithographic printing plate precursor of the present invention will be described.

For the lithographic printing of the present invention, a known lithographic printing machine is used. That is, sheet-fed and rotary printing machines of the offset and direct printing type are used.

After forming an image on the lithographic printing plate of the present invention,
The lithographic printing press is mounted on a plate cylinder, and the plate surface is supplied with ink from an inking roller that comes into contact with the plate surface.

The non-image portion having the hydrophilic swelling layer on the plate swells with the dampening solution supplied from the dampening solution supply device and repels the ink. On the other hand, the image portion receives ink and supplies the ink to the surface of the offset blanket cylinder or the surface of the printing medium to form a printed image.

The fountain solution used for printing the lithographic printing plate of the present invention may be, for example, pure water containing no additive. Can be used.

When printing using a lithographic printing plate obtained from the photosensitive lithographic printing plate precursor of the present invention, it is preferable to use pure water having no additive.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0069]

EXAMPLES Example 1 An aluminum plate (manufactured by Sumitomo Light Metal Co., Ltd.) having a thickness of 0.3 mm was
The following composition was applied and treated at 180 ° C. for 2 minutes to apply a primer layer having a thickness of ² g / m ² .

(1) 35 parts by weight of resole resin (2) 3 parts by weight of titanium oxide (3) 65 parts by weight of diglyme The following composition was applied on the primer layer obtained as described above. 3 g / m ² at 5 ° C. for 5 hours
Was coated with a photosensitive hydrophilic swelling layer having a thickness of 5 mm to obtain a negative type lithographic printing plate precursor.

(1) Leuco crystal violet (dye precursor) 2 parts by weight (2) Phenyltribromomethylsulfone (photooxidant) 5 parts by weight (3) Sodium dodecylbenzenesulfonate 1 part by weight (4) Sodium acrylate -N-butyl methacrylate copolymer (composition ratio: 40/60 mol%) 70 parts by weight (5) tetraethylene glycol diglycidyl ether 15 parts by weight (6) aqueous latex "JSR0596" (carboxy-modified styrene-butadiene copolymer) Latex, solid content 50.5%: manufactured by Nippon Synthetic Rubber Co., Ltd. 20 parts by weight (7) 2-aminopropyltrimethoxysilane 2 parts by weight (8) Purified water 900 parts by weight Mercury lamp "Jetlight 3"
303kW: manufactured by Oak Manufacturing Co., Ltd.
(ATE CONTOROL WEDGE: manufactured by KALLE) was subjected to contact exposure (3.6 mW / cm ² ) for 90 seconds through a negative film on which a negative film was stuck.

As a result, a clear image in which the exposed portion developed color was obtained. Next, the entire surface of the plate was rinsed with tap water, and the unexposed portions of the leuco dye, the photooxidant, the anionic surfactant and the like were washed and removed, thereby completing the developing step. The density difference between the exposed portion and the unexposed portion was measured with a Macbeth reflection densitometer, and was 1.50. As a result, a plate having excellent plate inspection properties was obtained.

Further, when the obtained printing plate was printed on high quality paper by a sheet-fed offset printing press, a good printed matter was obtained.

Comparative Example 1 Example 1 except that the composition of the photosensitive hydrophilic swelling layer was as follows:
A plate was produced in the same manner as described above.

(1) 2 parts by weight of leuco crystal violet (dye precursor) (2) 5 parts by weight of phenyltribromomethylsulfone (photooxidant) (4) 70 parts by weight of polyvinyl alicol (5) tetraethylene glycol diglycidyl 15 parts by weight of ether (6) 2 parts by weight of 2-aminopropyltrimethoxysilane (7) 900 parts by weight of purified water The obtained lithographic printing plate was obtained using a high-pressure mercury lamp “Jetlight 3”.
303kW: manufactured by Oak Manufacturing Co., Ltd.
(ATE CONTOROL WEDGE: manufactured by KALLE) was subjected to contact exposure (3.6 mW / cm ² ) for 90 seconds through a negative film on which a negative film was stuck.

As a result, a clear image in which the exposed portion developed color was obtained. Next, the entire surface of the plate was rinsed with tap water and developed. As a result, the coloring dye was dissolved into the water from the image area. For this reason, it was found that there was no difference in density between the exposed part and the unexposed part, and the plate inspection property was poor.

Further, when the obtained printing plate was printed on a high-quality paper using a sheet-fed offset printing machine, a good printed matter could not be obtained.

Example 2 On a 0.3 mm thick aluminum plate (manufactured by Sumitomo Light Metal Co., Ltd.),
The following composition was applied and treated at 180 ° C. for 2 minutes to apply a primer layer having a thickness of ² g / m ² .

(1) 35 parts by weight of resole resin (2) 3 parts by weight of titanium oxide (3) 65 parts by weight of diglyme The following composition was applied on the primer layer obtained as above, 3 g / m ² after treatment at 4 ° C. for 4 minutes
A hydrophilic swelling layer having a thickness of .mu.m.

(1) 5 parts by weight of hydrophilic polymer (2) 0.5 parts by weight of tetraethylene glycol diglycidyl ether (3) 95 parts by weight of purified water [Synthesis example of hydrophilic polymer] 60 g of vinyl acetate and 40 g of methyl acrylate To which 0.5 g of benzoyl peroxide was added as a polymerization initiator, and 3 g of partially saponified polyvinyl alcohol and NaCl 10 as dispersion stabilizers.
g in 300 ml of water.

The dispersion was stirred at 65 ° C. for 6 hours to perform suspension polymerization. The methyl acrylate component of the obtained copolymer was identified from the NMR spectrum to be 48 mol%.

The intrinsic viscosity in a benzene solution at 30 ° C. was 2.10.

Next, 8.6 g of the copolymer was added to a saponification reaction solution consisting of 200 g of methanol, 10 g of water and 40 ml of 5N NaOH, and the mixture was stirred and suspended.
After performing the saponification reaction for hours, the temperature was raised to 65 ° C,
The saponification reaction was further performed for 5 hours.

The obtained saponification reaction product was sufficiently washed with methanol and freeze-dried. The saponification degree was 98.3 mol%, and as a result of measurement of an infrared absorption spectrum, 1570 cm
^{At -1} , strong absorption attributed to the -COO ^- group was confirmed.

On the hydrophilic swelling layer obtained as described above, the following composition was applied and treated at 50 ° C. for 3 minutes to form a photosensitive layer having a thickness of 1.0 g / m ^2. Then, a negative type lithographic printing plate precursor was obtained.

(1) Zinc chloride salt of a condensate of p-diazodiphenylamine and paraformaldehyde 20 parts by weight (2) Polyvinyl alcohol 40 parts by weight (3) Leuco crystal violet (dye precursor) 0.5 parts by weight (4) ) Phenyltribromomethylsulfone (photooxidant) 1 part by weight (5) Sodium dodecylbenzenesulfonate 0.1 part by weight (6) Purified water 57.3 parts by weight 3
303kW: manufactured by Oak Manufacturing Co., Ltd.
(ATE CONTOROL WEDGE: manufactured by KALLE) was subjected to contact exposure (3.6 mW / cm ² ) for 90 seconds through a negative film on which a negative film was stuck.

As a result, a clear image in which the exposed portion developed color was obtained. Next, the entire surface of the plate was rinsed with tap water, and the unexposed portions of the leuco dye, the photooxidant, the anionic surfactant and the like were washed and removed, thereby completing the developing step. The density difference between the exposed portion and the unexposed portion was measured with a Macbeth reflection densitometer, and was 1.50. As a result, a plate having excellent plate inspection properties was obtained.

Further, the obtained printing plate was printed on a high-quality paper by using a sheet-fed offset printing press, and a good printed matter was obtained.

Comparative Example 2 A plate was prepared in the same manner as in Example 2 except that sodium dodecylbenzenesulfonate in the photosensitive layer composition of Example 2 was omitted.

The obtained lithographic printing plate was PCW (PLATE CONTOROL WEDGE: manufactured by KALLE) using a high-pressure mercury lamp “Jetlight 3303kW: manufactured by Oak Manufacturing Co., Ltd.”
For 90 seconds through a negative film with
6 mW / cm ² ).

As a result, a clear image in which the exposed portion developed color was obtained. Next, the entire surface of the plate was rinsed with tap water and developed. As a result, the coloring dye was dissolved into the water from the image area. For this reason, it was found that there was no difference in density between the exposed part and the unexposed part, and the plate inspection property was poor.

Further, when the obtained printing plate was printed on high-quality paper by using a sheet-fed offset printing press, a good printed matter could not be obtained.

[0093]

When the photosensitive lithographic printing plate of the present invention is used,
Since the dye formed by the exposure is insoluble in water, a printing plate having excellent plate inspection properties can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location G03F 7/038 G03F 7/038

Claims (5)

[Claims] 1. A lithographic printing plate having at least a photosensitive hydrophilic swelling layer on a substrate, wherein the hydrophilic swelling layer contains a leuco dye, a photooxidant, and an organic acid salt. Lithographic printing plate precursor. 2. A photosensitive lithographic printing plate comprising at least a hydrophilic swelling layer and a photosensitive layer laminated on a substrate, wherein the photosensitive layer contains a leuco dye, a photooxidant, and an organic acid salt. Photosensitive lithographic printing plate precursor. 3. A plate making method for a photosensitive lithographic printing plate, wherein a color is formed when the photosensitive lithographic printing plate precursor according to claim 1 is exposed. 4. A method for making a photosensitive lithographic printing plate according to claim 3, wherein the image area is colored. 5. The photosensitive lithographic printing plate precursor according to claim 1, wherein the organic acid salt is an anionic surfactant.