JPH04221957A - Photosensitive planographic printing plaste - Google Patents

Abstract

PURPOSE:To obtain the planographic plate less in malodor malodor and toxicity during/after manufacture and improved in coatabiljty and removal of films and dyes and superior in underdevelopment and film strength by coating a substrate with a specified photosensitive coating solution. CONSTITUTION:The supbstrate is coated with the photosensitive solution containing (a) an o-quinonediazido compound, (b) propyleneglycol 1-4C alkyl ether in the amount of 60-90wt.% of the solid components, (c) 10-25C fatty monocarboxylic acid, and (d) an organic dye espacially changeable in tone by acid. As the quinonediazido compound, the ester compounds of o- naphthoquinonediazidosulfonic acid with the polycondensation product of phenols and aldehydes and/or ketones are enumerated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive lithographic printing plate, and more particularly to a photosensitive lithographic printing plate manufactured using a novel coating solvent with low odor and toxicity.

0002

2. Description of the Related Art Positive-working photosensitive lithographic printing plates generally have an ink-receptive photosensitive layer formed on a hydrophilic support, which becomes solubilized by exposure to light. When this photosensitive layer is subjected to imagewise exposure and development, the non-image areas are removed while leaving the image areas, thereby forming an image. In printing, the difference in properties of image areas being lipophilic and non-image areas being hydrophilic is utilized.

The photosensitive layer of such a positive photosensitive lithographic printing plate usually contains a quinonediazide compound as a photosensitive substance, and an alkali-soluble resin as a component for increasing film strength and alkali solubility. , Contains a dye to improve visible image quality upon exposure.

[0004] The above-mentioned photosensitive layer is usually prepared by using a coating solution prepared by dissolving a composition containing a quinonediazide compound, an alkali-soluble resin, a dye, etc. in a coating solvent such as ethylene glycol monomethyl ether or ethylene glycol monoethyl ether on a support. Obtained by applying on top.

[0005]

[Problems to be Solved by the Invention] The photosensitive planographic printing plate obtained as described above is exposed and developed to obtain a planographic printing plate, but at this time, the non-image areas are not completely removed; There is a problem in that a photoresist film remains even after development, a so-called residual film phenomenon, and a large amount of dye remains after development.

[0006] To address this problem, Japanese Patent Application Laid-Open No. 2-967
No. 61 discloses a method using a specific higher fatty acid, which improves the residual film and dye residue, but on the other hand, deteriorates the film strength and the so-called under-developability as described below. It became clear that

In other words, the development of positive photosensitive lithographic printing plates is normally carried out in a developer consisting of an alkaline aqueous solution, but the developing ability of the developer is subject to fluctuations under various conditions, such as fatigue caused by large-scale processing. The developing ability decreases due to deterioration due to oxidation and air oxidation, and the photosensitive layer in the non-image area of the printing plate may not be completely dissolved even after processing. The allowable range of developing ability reduction that allows for proper developing results to be obtained is defined as "
This is called "under-developability."

Furthermore, the above-mentioned coating solvent has a strong odor and toxicity, which poses a major problem in terms of the working environment during and after production.

Therefore, an object of the present invention is to provide a photosensitive lithographic printing plate that has extremely low odor and toxicity during or after production, has improved residual film and dye residue, and has excellent under-developability and film strength. It is about providing.

0010

[Means for Solving the Problems] In view of the above-mentioned problems, the present inventors have conducted intensive research and found that the above-mentioned object of the present invention is to provide at least (a) a quinonediazide compound, (b) a quinonediazide compound having 1 carbon atom, on a support. To provide a photosensitive lithographic printing plate coated with a photosensitive coating liquid containing a propylene glycol alkyl ether having ~4 alkyl groups, (c) a fatty acid having 10 to 25 carbon atoms, and (d) a dye. We found that this can be achieved by

The present invention will be explained in more detail below.

In the present invention, propylene glycol alkyl ether is used when the alkyl component thereof has 1 to 1 carbon atoms.
A value in the range of 4 is used, and as such, an alkyl component having a carbon atom number of 1 or 2 is preferably used, and an alkyl component having a carbon atom number of 1 is particularly preferably used. . In particular, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol isopropyl ether,
Propylene glycol n-propyl ether, propylene glycol isobutyl ether, propylene glycol n-butyl ether and the like are preferably used.

The propylene glycol alkyl ether is contained in the coating solution used in an amount of 50 to 90% by weight, preferably 60 to 90% by weight.

The photosensitive lithographic printing plate of the present invention contains a fatty acid having 10 to 25 carbon atoms, and preferably an aliphatic monocarboxylic acid is used as such fatty acid. If the number of carbon atoms is less than 10, there will be little improvement in residual film, dye residue, and under-developability, and if it is more than 25, the solubility in solvents may be poor, resulting in poor coating properties.

Specifically, the following compounds are used.

[0016]

[Chemical formula 1]

[0017]

[Chemical formula 2] The above fatty acid is preferably 0.2 to
Contains 8% by weight.

Examples of the quinonediazide compound used in the present invention include ester compounds of orthonaphthoquinonediazide sulfonic acid and polycondensation resins of phenols and aldehydes or ketones.

Examples of the above-mentioned phenols include monohydric phenols such as phenol, o-cresol, m-cresol, p-cresol, 3,5-xylenol, carvacrol, and thymol, and dihydric phenols such as catechol, resorcinol, and hydroquinone. Examples include trihydric phenols such as hydric phenols, pyrogallol, and phloroglucin.

[0020] Examples of the aldehyde include formaldehyde, benzaldehyde, acetaldehyde, crotonaldehyde, and furfural. Preferred among these aldehydes are formaldehyde and benzaldehyde.

[0021] Furthermore, examples of the above-mentioned ketones include acetone and methyl ethyl ketone.

Specific examples of the polycondensation resin include phenol/formaldehyde resin, m-cresol/formaldehyde resin, m-, p-mixed cresol/formaldehyde resin, resorcinol/benzaldehyde resin, pyrogallol/acetone resin, etc. It will be done.

The condensation rate of o-naphthoquinonediazide sulfonic acid with respect to the OH group of the phenol in the orthonaphthoquinonediazide compound (reaction rate with respect to one OH group) is preferably 15 to 80%, more preferably 20 to 45%.
%.

The quinonediazide-containing polymer compound used in the present invention preferably has a weight average molecular weight of 1,000 or more, more preferably 1,500 or more, in view of coating properties. be.

Further, examples of the quinonediazide compound used in the present invention include those described in JP-A-58-43451. Also, 2,3,4-trihydroxybenzophenone, 2,3,4,4-tetrahydroxybenzophenone, 2,3,4,2',4'-pentahydroxybenzophenone, 2,3,4,3',4 ′、
Condensation compounds of 5'-hexahydroxybenzophenone and the like and orthoquinonediazide groups can also be used.

Among the above quinonediazide compounds, 1 and 2
-benzoquinonediazide sulfonyl chloride or 1,2
Most preferred is an orthoquinonediazide ester compound obtained by reacting -naphthoquinonediazide sulfonyl chloride with a pyrogallol/acetone condensation resin or 2,3,4-trihydroxybenzophenone.

As the quinonediazide compound used in the present invention, each of the above compounds may be used alone, or two
A combination of two or more kinds of compounds may be used.

The preferred amount of the quinonediazide compound used is 10 to 40% by weight in the photosensitive planographic printing plate.

Particularly preferred as the quinonediazide group are the 4- or 5-sulfonic acid group of 1,2-quinonediazide or the 4- or 5-carboxyl group of 1,2-quinonediazide.

The photosensitive lithographic printing plate of the present invention contains a dye, and such a dye includes a pigment as well as a dye, and inorganic pigments can also be used, but in particular, the color tone cannot be changed by acid. It is preferable to use organic dyes that cause

Examples of the organic dyes used include diphenylmethane, triphenylmethane, thiazine,
Examples include oxazine-based, xanthene-based, anthraquinone-based, iminonaphthoquinone-based, and azomethine-based.

Examples of these organic dyes include Eisen Brilliant Basic Cyanine 6GH [manufactured by Hodogaya Chemical Co., Ltd.], Astra New Fuchsin, Alizarin Red S, Eosin, Ethyl Violet, Erythrosin B, Auramine, Oil Green #502 [Orient Chemical Co., Ltd.] Made by Kogyo Co., Ltd.], Oil Scarlet #308 [
Orient Chemical Industry Co., Ltd.], Oil Pink #312
[Manufactured by Orient Chemical Industry Co., Ltd.], Oil Blue #60
3 [Orient Chemical Industry Co., Ltd.], Oil Red 5B
[Orient Chemical Industry Co., Ltd.], Oil Red OG [
Orient Chemical Industry Co., Ltd.], Oil Red RR [Orient Chemical Industry Co., Ltd.], Orange IV, 2-carboxyanilino-4-p-diethylaminophenylimino naphthoquinone, 2-carbostearylamino-4-p
-dihydroxyethylaminophenylimino naphthoquinone, xylenol blue, quinaldine red, crystal violet, crystal violet F10B, m
-Cresol purple, cresol red, Congo red, cyano-p-diethylaminophenyliminoacetanilide, 4-p-diethylaminophenylimino naphthoquinone, 2,7-dichlorofluorescein, diphenylthiocarbazone, 1,3-diphenyltriazine,
Spin Red BEH Special [manufactured by Hodogaya Chemical Industry Co., Ltd.], sulforhodamine B, thymol sulfophthalein, thymol phthalein, thymol blue, Nile blue 2B, Nile blue A, 1-β-naphthyl-4-p-
Diethylaminophenylimino-5-pyrazolone, α-
Naphthyl red, paraphthacine, paramethyl red, Victoria Pure Blue BOH, Fast Acid Violet R, phenacetaline, 1-phenyl-3-methyl-4-p-diethylaminophenylimino-5-pyrazolone, phenolphthalein, phenol red, fuchsin, Brilliant green, bromocresol purple, bromophenol blue, basic fuchsin,
Benzopurpurin 4B, magenta, malachite green, methanyl yellow, methyl orange, methyl green, methyl violet 2B, methyl violet, p-
Methoxybenzoyl-p'-diethylamino-o'-methylphenyliminoacetanilide, Rose Bengal,
Rhodamine 6G and Rhodamine B can be specifically mentioned.

Among these compounds, triphenylmethyl-based compounds are preferred from the viewpoint of the degree of discoloration and storage stability.

Dyes particularly preferably used in the present invention include malachite green (CI42000),
Methyl violet (CI42535), methyl green (CI42585), crystal violet (CI
42555), brilliant green (CI42040)
), ethyl violet (CI42600), phenolphthalein, phenol red, bromophenol blue, thymol blue, bromocresol purple, Victoria Pure Blue BOH (CI42595), Eisen Brilliant Basic Cyanine 6GH [manufactured by Hodogaya Chemical Co., Ltd.] (CI42025) ), astraneufuchsin (CI42520), magenta (CI425
10), Crystal Violet F10B (manufactured by BASF) (CI42557), Fuchsin (CI42500)
Among them, ethyl violet is particularly preferably used.

The proportion of these dyes in the photosensitive layer of the photosensitive lithographic printing plate is preferably 0.1 to 10% by weight, and 0.1 to 10% by weight.
Particularly preferred is 3 to 5% by weight.

In the present invention, compounds that generate acids or free radicals upon irradiation with actinic rays can be used in combination with the above-mentioned dyes within a range that does not impair the effects of the present invention. Such compounds include trihaloalkyl compounds or diazonium salt compounds can be used.

The above-mentioned quinonediazide compound is preferably used in combination with an alkali-soluble resin. Examples of the alkali-soluble resin include novolac resin, vinyl polymer having a phenolic hydroxyl group, and JP-A-55-57841.
Examples include condensation resins of polyhydric phenols and aldehydes or ketones, which are described in Japanese Patent Publication No. Examples of novolak resin include phenol formaldehyde resin,
Cresol formaldehyde resin, JP-A-55-57
Phenol/cresol/formaldehyde copolycondensation resin as described in JP-A No. 841, JP-A-55-
Examples include copolycondensation resins of p-substituted phenol and phenol or cresol and formaldehyde as described in Japanese Patent No. 127553.

The vinyl polymer having a phenolic hydroxyl group is a polymer having a unit having a phenolic hydroxyl group in its molecular structure, and has the following general formula (I
) to (V) are preferred.

[0039]

embedded image [In the formula, R1 and R2 each represent a hydrogen atom, an alkyl group, or a carboxyl group, and preferably a hydrogen atom. R3 represents a hydrogen atom, a halogen atom, or an alkyl group, preferably a hydrogen atom or an alkyl group such as a methyl group or an ethyl group. R4 represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, preferably a hydrogen atom. A represents an alkylene group optionally having a substituent that connects a nitrogen atom or an oxygen atom and an aromatic carbon atom, m represents an integer of 0 to 10, and B has a substituent. represents a phenylene group that may have a substituent or a naphthylene group that may have a substituent. ] The polymer used in the photosensitive lithographic printing plate of the present invention preferably has a copolymer-type structure, and can be used in combination with the structural units represented by the above general formulas (I) to (V), respectively. Examples of monomer units include ethylene, propylene, isobutylene,
Ethylenically unsaturated olefins such as butadiene and isoprene; styrenes such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene; acrylic acids such as acrylic acid and methacrylic acid; e.g. itaconic acid and maleic acid. acids, unsaturated aliphatic dicarboxylic acids such as maleic anhydride, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α - Esters of α-methylene aliphatic monocarboxylic acids such as methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, ethyl ethacrylate, nitriles such as acrylonitrile, methacrylonitrile, amides such as acrylamide, e.g. acrylic Anilides such as anilide, p-chloroacrylanilide, m-nitroacrylanilide, m-methoxyacrylanilide, e.g. vinyl acetate,
Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate, etc., such as methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, β-
Vinyl ethers such as chloroethyl vinyl ether, vinyl chloride, vinylidene chloride, vinylidene cyanide, such as 1-methyl-1-methoxyethylene, 1,1
-dimethoxyethylene, 1,2-dimethoxyethylene,
1,1-dimethoxycarbonylethylene, 1-methyl-
Ethylene derivatives such as 1-nitroethylene, e.g.
There are N-vinyl monomers such as vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidene, and N-vinylpyrrolidone. These vinyl monomers exist in polymer compounds with a structure in which unsaturated double bonds are cleaved.

Among the above-mentioned monomers, esters of aliphatic monocarboxylic acids and nitriles are preferred because they exhibit excellent performance for the purpose of the present invention.

These alkali-soluble resins have 1,50
Those having a molecular weight of 0 or more are preferable, and those having a molecular weight of 2,500 or more are more preferable.

These alkali-soluble resins are preferably contained in the photosensitive planographic printing plate of the present invention in an amount of 50 to 90% by weight.

The photosensitive lithographic printing plate of the present invention may contain other additives, if necessary, in addition to the above-mentioned materials. For example, various low-molecular compounds such as phthalate esters, triphenyl phosphates, and maleate esters are used as plasticizers, and fluorine-based surfactants and nonionic surfactants such as ethyl cellulose polyalkylene ether are used as coating properties improvers. Examples include surfactants such as.

A sensitizer for improving sensitivity can also be added to the photosensitive composition of the present invention. Examples of the sensitizer include gallic acid derivatives as described in JP-A-57-118237, phthalic anhydride, tetrahydrophthalic anhydride, as described in JP-A-52-80022, 5-membered cyclic acid anhydrides such as hexahydrophthalic anhydride, maleic anhydride, succinic anhydride, pyrometic acid, itaconic acid, etc., and glutaric anhydride and Examples include 6-membered cyclic acid anhydrides such as derivatives thereof. Among these, preferred are cyclic acid anhydrides, especially 6
Member cyclic acid anhydrides are preferred.

[0045] In the present invention, the coating method for coating the support with the photosensitive coating solution may be a conventionally known method, for example,
Spin coating, wire bar coating, dip coating, air knife coating, roll coating, blade coating, curtain coating, etc. are possible.

Supports on which the photosensitive layer is provided include metal plates such as aluminum, zinc, copper, and steel; metal plates plated or vapor-deposited with chromium, zinc, copper, nickel, aluminum, and iron; paper; Plastic film; paper coated with resin; paper covered with metal foil such as aluminum;
Examples include plastic films treated to make them hydrophilic. Among these, aluminum plates are preferred.

When an aluminum plate is used as a support, it is preferably subjected to surface treatments such as graining, anodizing, and, if necessary, sealing.

[0048] Examples of the graining treatment include a mechanical method and an electrolytic etching method. Examples of the mechanical method include a ball polishing method, a brush polishing method, a polishing method using liquid honing, and a buffing method. The various methods described above can be used alone or in combination depending on the composition of the aluminum material. A preferred method is electrolytic etching.

[0049] Electrolytic etching can be performed using phosphoric acid, sulfuric acid, hydrochloric acid,
It is carried out in a bath containing one or more inorganic acids such as nitric acid. After the graining treatment, if necessary, desmut treatment is performed with an aqueous alkali or acid solution, neutralized, and washed with water.

[0050] In the anodizing process, one or two types of sulfuric acid, chromic acid, oxalic acid, phosphoric acid, malonic acid, etc. are used as the electrolyte.
Electrolysis is carried out using a solution containing at least one species, with an aluminum plate used as an anode. The amount of anodic oxide film formed is 1 to 5
0mg/dm2 is suitable, preferably 10-40m
g/dm2. The amount of anodized film can be determined by, for example, applying an aluminum plate to a phosphoric acid chromic acid solution (85% phosphoric acid solution: 35%
milliliter, chromium oxide (VI): prepared by dissolving 20 g in 1 liter of water) to dissolve the oxide film,
It is determined by measuring changes in weight before and after dissolving the film on the plate.

Specific examples of the sealing treatment include hot water treatment, steam treatment, sodium silicate treatment, and dichromate aqueous solution treatment. In addition, the aluminum plate support may be subjected to subbing treatment using an aqueous solution of a water-soluble polymer compound or a metal salt such as fluorinated zirconate.

In addition, when contact printing a film original onto a photosensitive lithographic printing plate, the printing frame is generally vacuumed.
This method of improving vacuum adhesion can also be applied to the photosensitive lithographic printing plate of the present invention. Methods for improving vacuum adhesion include a method of mechanically making unevenness on the surface of the photosensitive layer, a method of scattering solid powder on the surface of the photosensitive layer, and a method of spreading solid powder on the surface of the photosensitive layer.
A method of providing a matte layer on the surface of a photosensitive layer as described in Japanese Patent Application Laid-open No. 25805, and a method of heat-sealing a solid powder on the surface of a photosensitive layer as described in Japanese Patent Application Laid-open No. 12974/1984, etc. Can be mentioned.

The photosensitive lithographic printing plate of the present invention can be used in the same manner as those conventionally used. For example, by exposing a transparent positive film to a light source such as an ultra-high pressure mercury lamp, metal halide lamp, xenon lamp, or tungsten lamp, and then developing it with an alkaline developer, only the unexposed areas remain on the surface of the support, leaving a positive image. A positive relief image is created.

Examples of the alkaline developer used include alkali metal developers such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium metasilicate, potassium metasilicate, dibasic sodium phosphate, and tribasic sodium phosphate. Examples include aqueous solutions of salts. The concentration of the alkali metal salt is preferably 0.1 to 10% by weight. Furthermore, an anionic surfactant, an amphoteric surfactant, and an organic solvent such as alcohol can be added to the developer as required.

[0055]

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 (Preparation of photosensitive lithographic printing plate sample) An aluminum plate with a thickness of 0.24 mm was degreased in a 5% by weight aqueous sodium hydroxide solution at 60°C for 1 minute, and then 1 liter of 0.
In a 5 molar aqueous hydrochloric acid solution at a temperature of 25°C and a current density of 60
Electrolytic etching treatment was performed under the conditions of A/dm2 and treatment time of 30 seconds. Then, after desmutting in a 5% by weight aqueous sodium hydroxide solution at 60°C for 10 seconds,
Temperature 20°C, current density 3A/dm2 in wt% sulfuric acid solution
The anodic oxidation treatment was carried out under the conditions that the treatment time was 1 minute. Further, a hot water sealing treatment was performed with hot water at 30° C. for 20 seconds to produce an aluminum plate to be used as a support for lithographic printing plate material.

A photosensitive composition coating solution having the following composition was applied to the aluminum plate prepared above using a roll coater, and dried at 90° C. for 4 minutes to obtain positive photosensitive lithographic printing plate sample No. I got 1. The amount of photosensitive composition applied was 24 m.
g/dm2. (Photosensitive coating liquid composition) Binder resin (BD-1)
7.0g
Quinonediazide compound (QD-1)
1.6 g 2
-Trichloromethyl-5-(β-benzofuryl vinyl)
-1,3,4-oxadiazole
0.02g
Victoria Pure Blue BOH
(Manufactured by Hodogaya Chemical)
0.06g Fatty acid (A) of the present invention
0.17g
Propylene glycol monomethyl ether
70 g ethyl acetate
30
g In the coating liquid composition of the photosensitive composition, the binder resin, the quinonediazide compound, the fatty acid of the present invention, and the solvent were as shown in Table 1 to obtain Samples 2 to 13, respectively.

[0058] Each of these lithographic printing plate samples 1 to 13 had 2K
A film original was exposed from a distance of 90 cm using a W metal halide lamp (Idol Fin 2000 manufactured by Iwasaki Electric Co., Ltd.) as a light source. Each of the samples was then developed using the following developing conditions and developer.

[0059]

[Table 1] (Development conditions) Developer: 4% sodium metasilicate aqueous solution with 0.1% sodium benzenesulfonate added (contains no organic solvent) Automatic developer: Konica PS plate automatic developer "PSK-" 9
10'' (manufactured by Konica) Development temperature: 27°C Development time: 20 seconds Using the developer under the above development conditions as a standard, dilute as shown below and develop each sample with each developer. Printing was performed under the following conditions to evaluate plate surface staining. The results are shown in Table 2.

(Printing conditions) Printing machine: Heidel GTO Printing ink: Toyo King New Bright Red (oil-based ink manufactured by Toyo Ink Co., Ltd.) Printing paper: High quality paper Printing speed: 8000 sheets/hour

[0061]

[Table 2] As is clear from Table 2, all of the samples 1 to 10 of the present invention having the structure of the present invention have a higher plate surface than comparative samples 11 to 13 which do not contain at least one fatty acid and propylene glycol. Excellent in terms of stains, dye residue, film strength, and film strength. *1 Quinonediazide compound

[0062]

[C4]

[0063]

[Chemical formula 5] *2 Binder resin BD-1 Copolymer resin of phenol, m-cresol, p-cresol (molar ratio 48:32:20) and formaldehyde

[0064]

[Chemical 6] *3 Fatty acid A cis CH3(CH2)5CH=CH(C
H2)7COOHB cis CH3(CH2)
10CH=CH(CH2)4COOHC cis
CH3(CH2)7CH=CH(CH2)11COO
HD n C10H21COOH E n C11H23COOH *4 PGM: Propylene glycol monomethyl ether *5 Plate surface stain A: No plate surface stain B: Plate surface stain is slightly observed, but to the extent that it can withstand practical use C: Plate surface stain occurs, practical use Slightly affected D: Significant plate surface staining *6 Reflectance: The reflectance of the non-image area of the sample developed with the standard developer was determined from the intensity of reflected light at a wavelength of 280 nm.
The remaining dye and amount of film remaining were evaluated. *7 Film strength: Attach a pencil to a commercially available plotter,
When a straight line is drawn on the sample while applying a load of 50 g to the pencil, the film strength is indicated by the hardness of the softest pencil, which scratches the photosensitive layer and causes grains to appear.

[0065]

[Effects of the Invention] As explained in detail above, the present invention has extremely low odor and toxicity during or after production, improves residual film and dye residue, and has excellent under-developability and film strength. A photosensitive lithographic printing plate can be provided.

Claims (2)

[Claims] Claim 1: At least (a) a quinonediazide compound, and (b) an alkyl component having a carbon atom number of 1 on a support.
A photosensitive lithographic printing plate coated with a photosensitive coating liquid containing propylene glycol alkyl ether having a value within the range of .about.4, (c) a fatty acid having 10 to 25 carbon atoms, and (d) a dye. 2. The photosensitive lithographic printing plate according to claim 1, wherein the dye (d) is ethyl violet.